Cern News

Subscribe to Ροή Cern News
Ενημερώθηκε: πριν από 11 λεπτά 23 δευτερόλεπτα

Computer Security: Swipes vs PINs vs passwords vs you

Τρί, 09/04/2024 - 15:03
Computer Security: Swipes vs PINs vs passwords vs you

What kind of person are you? An artist, like a painter? A credit card fanatic or just “in numbers”? Cerebral, a memoriser or even a genius? An influencer, like a peacock, or just prettily self-confident? A security buff or sufficiently security aware? Or just ignorant about security and your privacy? Let’s assume for a moment that the way you unlock your smartphone tells us which.

There are many different ways to unlock your smartphone: swiping patterns, PIN numbers, passwords, biometric fingerprints or face recognition. Some are more secure, some less so. But all are better than nothing. So, let’s look at some of them.

Swiping patterns: The obvious choice on Android phones. Your favourite pattern on a 3x3 matrix. But as it should be a continuous swipe, the number of actual possibilities are quite limited, boiling down to about 20 most-used swipes. If yours is listed there, it may be time to move to another, more secure swipe. In any case, your swiping can be spied on and then tried once your smartphone is stolen.

Worse ─ although it’s probably still academic ─ a small basic sonar system combining a local loudspeaker to emit acoustic signals inaudible to humans and a microphone to record them coming back again allowed researchers to use “the echo signal […] to profile user interaction with the device”, i.e. the way your finger swipes over and interacts with the screen. They’ve shown how this sonar can be employed to help identify the swipe pattern to unlock an Android phone – reducing the number of trials to be performed by an attacker by 70%. And that’s only their proof of concept… Maybe PINs and passwords are better?

PINs vs passwords: A common paradigm of computer security is linked to password complexity. Four-digit PIN numbers are no longer state of the art. And even six digits are not necessarily sufficient. While guessing and brute-forcing is difficult, as your smartphone should have a lock-out procedure only allowing a small number of tries before introducing timeouts or even wiping your phone completely(!), PINs can be easily spied on and replayed once your smartphone has been stolen*. Or do you shield your screen as you type your smartphone PIN as you do for your credit card at an ATM? Of course, a better choice is a long and complex password or even passphrase (unless you use one of the top 10 most-used passwords). Admittedly, typing such long and complex passwords can be tedious. Enter: biometrics.

Biometrics: Still our favourite – using your fingerprint sensor or a capture of your face to unlock your phone. Your smartphone (and laptop) manufacturers went to extreme lengths to ensure that your biometric signature cannot be tampered with by your fingerprint on a piece of tape, your face in a photo or your sleeping self. And they also ensured that your biometric information is properly and securely stored using a special-purpose hardware chip (TPM: “trusted platform module”). Still, fingerprint authentication in particular has been broken into in the past for Android and Windows devices, making face recognition our favourite choice to protect access to your smartphone and all the personal (and professional!) data you store and access with it.

 

*Actually, Apple’s latest security patch also fixed some issues with this.

______

Do you want to learn more about computer security incidents and issues at CERN? Follow our Monthly Report. For further information, questions or help, check our website or contact us at Computer.Security@cern.ch.

anschaef Tue, 04/09/2024 - 14:03 Byline Computer Security team Publication Date Tue, 04/09/2024 - 14:01

Large Hadron Collider reaches its first stable beams in 2024

Παρ, 05/04/2024 - 11:28
Large Hadron Collider reaches its first stable beams in 2024 LHC Page 1 showing the first stable beams of 2024 (Image: CERN)

On Friday 5 April, at 6.25 p.m., the LHC Engineer-in-Charge at the CERN Control Centre (CCC) announced that stable beams were back in the Large Hadron Collider, marking the official start of the 2024 physics data-taking season. The third year of LHC Run 3 promises six months of 13.6 TeV proton collisions at an even higher luminosity than before, meaning more collisions for the experiments to take data from. This will be followed by a period of lead ion collisions in October.

Before the LHC could restart, each accelerator in the CERN complex had to be prepared for another year of physics data taking. Beginning with Linac4, which welcomed its first beam two months ago, each accelerator has gone through a phase of beam commissioning in which it is gradually set up and optimised to be able to control all aspects of the beam, from its energy and intensity to its size and stability. During this phase researchers also test the accelerator’s performance and address any issues before it is used for physics. Following Linac4, which contains the source of protons for the beam, each accelerator was commissioned in turn: the Proton Synchrotron Booster, the Proton Synchrotron, the Super Proton Synchrotron, and finally the LHC from 8 March until 5 April. The whole complex is now ready for data taking.

Back to the CCC. While stable beams are the goal, the CCC engineers must first take several steps to achieve them. First, they must inject the beams into the LHC from the previous accelerators in the chain. Then begins the ramp-up process, which involves increasing the beam energy up to the nominal energy of 6.8 TeV. The next step – shown as “flat top” on LHC Page 1 – is where the energy in the beams is consistent, but they’re not quite ready yet. In order to achieve stable beams, the circulating beams must then be “squeezed” and adjusted using the LHC magnets. This involves making the beams narrower and more centred on their paths, and therefore more likely to produce a high number of collisions in the detectors. Only after the squeezing and adjustment has been completed can stable beams be declared and the experiments around the LHC begin their data taking.

Watch a video explaining the process from first injection to stable beams:

Delphine Jacquet and Georges Trad, both engineers in charge of the LHC, explain how the LHC beams work from the injections of protons to stable beams.  (Video: CERN)

Did you know?

Although the solar eclipse on 8 April will not affect the beams in the LHC, the gravitational pull of the moon, like the tides, changes the shape of the LHC because the machine is so big. Read more here.

ndinmore Fri, 04/05/2024 - 10:28 Byline Naomi Dinmore Publication Date Fri, 04/05/2024 - 18:30

FASER measures high-energy neutrino interaction strength

Πέμ, 04/04/2024 - 15:46
FASER measures high-energy neutrino interaction strength

Operating at CERN’s Large Hadron Collider (LHC) since 2022, the FASER experiment is designed to search for extremely weakly interacting particles. Such particles are predicted by many theories beyond the Standard Model that are attempting to solve outstanding problems in physics such as the nature of dark matter and the matter-antimatter imbalance in the Universe. Another goal of the experiment is to study interactions of high-energy neutrinos produced in the LHC collisions, particles that are nearly impossible to detect in the four big LHC experiments. Last week, at the annual Rencontres de Moriond conference, the FASER collaboration presented a measurement of the interaction strength, or “cross section”, of electron neutrinos (νe) and muon neutrinos (νμ). This is the first time such a measurement has been made at a particle collider. Measurements of this kind can provide important insights across different aspects of physics, from understanding the production of “forward” particles in the LHC collisions and improving our understanding of the structure of the proton to interpreting measurements of high-energy neutrinos from astrophysical sources performed by neutrino-telescope experiments.

FASER is located in a side tunnel of the LHC accelerator, 480 metres away from the ATLAS detector collision point. At that location, the LHC beam is already nearly 10 metres away, bending away on its circular 27-kilometre path. This is a unique location for studying weakly interacting particles produced in the LHC collisions. Charged particles produced in the collisions are deflected by the LHC magnets. Most neutral particles are stopped by the hundreds of metres of rock between FASER and ATLAS. Only very weakly interacting neutral particles like neutrinos are expected to continue straight on and reach the location where the detector is installed.

The probability of a neutrino interacting with matter is very small, but not zero. The type of interaction that FASER is sensitive to is where a neutrino interacts with a proton or a neutron inside the detector. In this interaction, the neutrino transforms into a charged “lepton” of the same family – an electron in the case of an νe, and a muon in the case of a νμ – which is visible in the detector. If the energy of the neutrino is high, several other particles are also produced in the collision.

The detector used to perform the measurement consists of 730 interleaved tungsten plates and photographic emulsion plates. The emulsion was exposed during the period from 26 July to 13 September 2022 and then chemically developed and analysed in search of charged particle tracks. Candidates for neutrino interactions were identified by looking for clusters of tracks that could be traced back to a single vertex. One of these tracks then had to be identified as a high-energy electron or muon.

Event displays identified by the FASER collaboration as candidates for an νe (left) and a νμ (right) interacting in the detector. Invisible here, the neutrinos arrive from the left and then interact to create multiple tracks spraying out to the right (coloured lines), one of which is identified as a charged lepton (labelled). (credit: FASER collaboration)

In total, four candidates for an νe interaction and eight candidates for a νμ interaction have been found. The four νe candidates represent the first direct observation of electron neutrinos produced at a collider. The observations can be interpreted as measurements of neutrino interaction cross sections, yielding (1.2+0.9−0.8) ×10−38 cm2 GeV−1 in the case of the νe and (0.5 ± 0.2) × 10−38 cm2 GeV−1 in the case of the νμ. The energies of the neutrinos were found to be in a range between 500 and 1700 GeV. No measurement of the neutrino interaction cross section had previously been made at energies above 300 GeV in the case of the νe and between 400 GeV and 6 TeV in the case of the νμ.

The results obtained by FASER are consistent with expectations and demonstrate the ability of FASER to make neutrino cross-section measurements at the LHC. With the full LHC Run 3 data, 200 times more neutrino events will be detected, allowing much more precise measurements.

Read more in the FASER publication.

cmenard Thu, 04/04/2024 - 14:46 Byline Piotr Traczyk Publication Date Thu, 04/04/2024 - 14:45

Giuseppe Fidecaro (1926 – 2024)

Πέμ, 04/04/2024 - 09:36
Giuseppe Fidecaro (1926 – 2024)

We are saddened to learn that experimental physicist Giuseppe Fidecaro, who joined CERN in 1956, died on 28 March. He was 97 years old. Giuseppe was a familiar face to the CERN community, often seen arms linked with his wife Maria as the pair made their way through the CERN corridors. He was also known to CERN visitors, featuring prominently in the Synchrocyclotron exhibition’s film. Maria Fidecaro passed away in September 2023.    

Born in Messina, Italy in 1926, Giuseppe graduated in physics from the University of Rome in 1947 under the supervision of Edoardo Amaldi. He came to CERN with Maria in the summer of 1956 and was assigned to the Synchrocyclotron. There, he established a group and prepared equipment for experiments that in 1958 enabled a successful search for pions decaying into an electron and a neutrino – a process which gave experimental ground to the universal Fermi interaction.

In 1975, Giuseppe was appointed co-chair of a joint scientific committee set up under the terms of the collaboration agreement between CERN and the former USSR for the utilization of atomic energy, a responsibility he held until 1986. He was also tasked with coordinating cooperation with the Joint Institute for Nuclear Research in Dubna.

Giuseppe officially retired in 1991 but, together with Maria, he continued his work at CERN as an honorary member of the personnel until as recently as 2020.

A funeral service will be held at the Italian Catholic Mission of Geneva on Friday 5 April at 10:00 a.m.

A full obituary will appear in the CERN Courier.

abelchio Thu, 04/04/2024 - 08:36 Publication Date Thu, 04/04/2024 - 08:29

The CMS experiment at CERN measures a key parameter of the Standard Model

Τετ, 03/04/2024 - 12:01
The CMS experiment at CERN measures a key parameter of the Standard Model

Last week, at the annual Rencontres de Moriond conference, the CMS collaboration presented a measurement of the effective leptonic electroweak mixing angle. The result is the most precise measurement performed at a hadron collider to date and is in good agreement with the prediction from the Standard Model.

The Standard Model of Particle Physics is the most precise description to date of particles and their interactions. Precise measurements of its parameters, combined with precise theoretical calculations, yield spectacular predictive power that allows phenomena to be determined even before they are directly observed. In this way, the Model successfully constrained the masses of the W and Z bosons (discovered at CERN in 1983), of the top quark (discovered at Fermilab in 1995) and, most recently, of the Higgs boson (discovered at CERN in 2012). Once these particles had been discovered, these predictions became consistency checks for the Model, allowing physicists to explore the limits of the theory’s validity. At the same time, precision measurements of the properties of these particles are a powerful tool for searching for new phenomena beyond the Standard Model – so-called “new physics” - since new phenomena would manifest themselves as discrepancies between various measured and calculated quantities.

The electroweak mixing angle is a key element of these consistency checks. It is a fundamental parameter of the Standard Model, determining how the unified electroweak interaction gave rise to the electromagnetic and weak interactions through a process known as electroweak symmetry breaking. At the same time, it mathematically ties together the masses of the W and Z bosons that transmit the weak interaction. So, measurements of the W, the Z or the mixing angle provide a good experimental cross-check of the Model.

The two most precise measurements of the weak mixing angle were performed by experiments at the CERN LEP collider and by the SLD experiment at the Stanford Linear Accelerator Center (SLAC). The values disagree with each other, which had puzzled physicists for over a decade. The new result is in good agreement with the Standard Model prediction and is a step towards resolving the discrepancy between the latter and the LEP and SLD measurements.

“This result shows that precision physics can be carried out at hadron colliders,” says Patricia McBride, CMS spokesperson. “The analysis had to handle the challenging environment of LHC Run 2, with an average of 35 simultaneous proton-proton collisions. This paves the way for more precision physics at the High-Luminosity LHC, where five times more proton pairs will be colliding simultaneously.”

Precision tests of the Standard Model parameters are the legacy of electron-positron colliders, such as CERN’s LEP, which operated until the year 2000 in the tunnel that now houses the LHC. Electron-positron collisions provide a perfect clean environment for such high-precision measurements. Proton-proton collisions in the LHC are more challenging for this kind of studies, even though the ATLAS, CMS and LHCb experiments have already provided a plethora of new ultra-precise measurements. The challenge is mainly due to huge backgrounds from other physics processes than the one being studied and to the fact that protons, unlike electrons, are not elementary particles. For this new result, reaching a precision similar to that of an electron-positron collider seemed like an impossible task, but it has now been achieved.

The measurement presented by CMS uses a sample of proton-proton collisions collected from 2016 to 2018 at a centre-of-mass energy of 13 TeV and corresponding to a total integrated luminosity of 137 fb−1, meaning about 11.000 million million collisions! 

The mixing angle is obtained through an analysis of angular distributions in collisions where pairs of electrons or muons are produced. This is the most precise measurement performed at a hadron collider to date, improving on previous measurements from ATLAS, CMS and LHCb.

Read more:

angerard Wed, 04/03/2024 - 11:01 Publication Date Wed, 04/03/2024 - 16:00

CERN and the Swiss Arts Council announce the artists selected for the sixth edition of Connect

Τρί, 02/04/2024 - 17:09
CERN and the Swiss Arts Council announce the artists selected for the sixth edition of Connect

Connect is an art residency programme launched by Arts at CERN and Pro Helvetia in 2021. Dedicated to Swiss-based artists working at the intersection of science and artistic research, this research-led residency invites them to come to CERN to explore ideas and develop new work.

The selected duo is composed of Robin Meier Wiratunga and Vimala Pons. Meier Wiratunga is an artist and composer who seeks to understand how humans, insects and objects think. Collaborating closely with scientific researchers, Meier Wiratunga's work blends machine learning with insights from animal intelligence, creating constellation scores where musical patterns emerge as ‘thinking tools'. Vimala Pons is an actress who has worked in independent and auteur cinema.

Meier Wiratunga and Pons will dedicate their residency at CERN to developing their proposal titled Guided Meditations for the End of the Universe. This project aims to delve into cosmological theories about the end of the Universe to transform them into meditative and embodied experiences. Employing an anthropological approach to engage with science, the artists intend to employ spoken voice recordings, electronic music, light environments and sonified data from particle events.

Now in its sixth edition, Connect has become a pivotal platform for Swiss-based artists to expand their artistic practice in dialogue with the field of physics and science at CERN. This collaboration framework between Arts at CERN and Pro Helvetia will continue through the next year with an iteration in Chile and India, sustaining its mission to foster interactions and dialogue between artistic and scientific communities.

“We find ourselves in a challenging yet exciting time, as we witness the emergence of a strong and vibrant infrastructure devoted to the integration of artistic activity within the sciences,” says Mónica Bello, Curator and Head of Arts at CERN. “This is a transformational and promising development that presents unprecedented opportunities for cultural innovation. Connect is evidence of these dynamics, and I am proud to see that our partnership with Pro Helvetia is advancing further, bringing in new residents with different perspectives and backgrounds and strengthening the confluence of art and science in Switzerland.”

“This sixth edition of Connect continues to reaffirm the significance of the interface between art, science and technology. The quality and diversity of applications received illustrate the rich interdisciplinarity inherent in this dynamic field, and the extent to which it is part of current artistic practice. We are happy to foster dialogue and innovation at this remarkable intersection and are very pleased about the ongoing collaboration with Arts at CERN,” explains Philippe Bischof, Director of Pro Helvetia.

The jury of Connect was formed by Mónica Bello, Curator and Head of Arts at CERN; Giulia Bini, Head of Program and Curator of “Enter the Hyper-Scientific” at EPFL Lausanne; and Federica Martini, Head of the CCC - Critical Curatorial Cybermedia Master at HEAD Genève.

angerard Tue, 04/02/2024 - 16:09 Publication Date Wed, 04/03/2024 - 14:00

CERN to change name for 70th Anniversary

Τετ, 27/03/2024 - 20:02
CERN to change name for 70th Anniversary The Organization’s new logo. The correct usage of the branding can be found on the Design Guidelines website.

Since its inception in 1954, CERN has grown from a small group of physicists from a handful of countries to a thriving international hub for science and technology. This is why, on the occasion of the Laboratory’s 70th Anniversary, the time has come for the name to be adapted to reflect its new role in society. The new name, the Network of Experiments for Research and Development in Society, will come into force on 1 October 2024, at the Laboratory’s 70th birthday party.

The acronym CERN was borne from an intergovernmental meeting of UNESCO in Paris in December 1951. This is when the first resolution concerning the establishment of a European Council for Nuclear Research (in French Conseil Européen pour la Recherche Nucléaire, or CERN) was adopted. Two months later, an agreement was signed establishing the provisional Council – and the name “CERN” stuck. However, today, our understanding of matter goes much deeper than the nucleus, and “CERN” is now widely viewed across the scientific community as an outdated and exclusionary name.

“The word “nuclear” doesn’t really reflect the full breadth of scientific research we do here,” says Noah Lott, Head of Rebranding at the Organization. “Network of Experiments for Research and Development in Society indicates the range of particle physics, computing, engineering and technology research that takes place at the Laboratory, as well as its impact on society.”

“We are also no longer just a European organisation, as we have grown to a global community encapsulating more than 80 countries,” adds Ivana Reed, spokesperson for international relations at the Laboratory. “We feel that everyone, no matter who they are, will feel accepted and proud to be associated with NERDS.”

A dedicated working group – the Decision for a Unified Moniker Board – was created in 2021 to assess potential options for the new name. “NERDS is so much more memorable and inclusive than CERN,” explains Wirall Geex, president of the working group. “Since we are a global network of varied experiments, we hope the new name will remove negative stereotypes about the type of people who work at the Organization,” he adds, pushing up his glasses.

NERDS was chosen by the working group out of a list of names put forward by the CERN community. Among the high contenders were A Large International Experimental Network (ALIEN), the High Energy Laboratory for Physics (HELP), and the initial frontrunner, the Global Organization for Discovery (GOD). However, following a spirited debate in the working group, GOD was discarded on account of unfortunate echoes of the “God particle” – the controversial name accidentally given to the Higgs boson in 1993.

NERDS looks forward to continuing to be at the forefront of scientific research for the next 70 years and beyond.

ndinmore Wed, 03/27/2024 - 19:02 Publication Date Mon, 04/01/2024 - 09:00

Accelerator Report: Protons or Easter eggs? Let’s hope for both

Τετ, 27/03/2024 - 16:59
Accelerator Report: Protons or Easter eggs? Let’s hope for both

Beam commissioning is progressing well across the entire accelerator complex, with initial completion achieved in the first machines of the chain. Last week, the first physics experiments started in the East Area, behind the PS, and others will follow suit shortly.

A Cell-Coupled-Drift-Tube-Linac (CCDTL) ready to be tested in SM18. (Image: CERN)

However, despite the overall positive momentum of beam commissioning, challenges have arisen along the way, highlighting the complexities involved. Last week, some of the components of one of the Linac4 accelerating structures, specifically the Cell-Coupled-Drift-Tube-Linacs (CCDTLs) 3 and 4, presented some issues. Both CCDTLs rely on a single klystron*, a high-power microwave amplifier crucial for providing accelerating power to the structures, which, in turn, transfer the power to the protons, which are then accelerated.

The high-voltage and high-frequency amplifier chain, including the klystron, experienced frequent voltage breakdowns, resulting in a significant drop in accelerating voltage within the two CCDTLs. This disruption severely perturbed the beam, rendering it unusable for the PS Booster. Experts intervened multiple times, initially focusing on fine-tuning the parameters of the amplifier chain and later on cleaning and replacing various components suspected to be causing the breakdowns.

By 22 March, a set of parameters was established to allow the acceleration of beams with a low proton intensity, enabling commissioning activities to continue in the downstream machines, including the LHC. However, these parameters did not meet the requirements for generating the full-blown physics beams that will be required in the coming weeks. On 24 March, a collaborative effort with experts from various groups convened in the CERN Control Centre (CCC) to conduct a final assessment. This evaluation aimed to determine whether the klystron needed replacing.

After re-establishing the parameters suitable for high-intensity beam acceleration, the beam was switched back on. Unfortunately, within the first hour, at least two high-voltage breakdowns occurred – the team thus concluded that the klystron replacement was necessary.

To maintain commissioning activities in the downstream machines, parameters allowing low-intensity beam acceleration were reinstated. This allowed operations to continue until Monday morning, when the klystron replacement process started. Such an intervention typically requires two to three days before beam operations can be restored.

The new klystron is in place, ready to feed the CCDTLs 3 and 4. (Image: CERN)

Meanwhile, commissioning activities in the downstream machines have been suspended and the start of physics at the n_TOF facility, behind the PS, has been postponed (it was originally scheduled to start on 25 March). Commissioning of the North Area's secondary beams began on 22 March instead of 25 March. Thanks to this head start, the incident in Linac4 does not impact the overall schedule for the North Area, where physics is still scheduled to start on 10 April.

In Linac4, the old klystron has been removed, and the new one had been installed and tested by 26 March. Beam was sent to the PS Booster at 5 p.m. that day and, at 9 p.m., the LHC beam commissioning activities resumed. Since then, they have been progressing well.

On 27 March, beams entered into “test” collisions at the target energy of 6.8 TeV in the LHC. These were not yet stable beams, which meant that the experiments did not take data. Collisions for physics at 6.8 TeV are expected to take place on 8 April.

______

* A klystron is a high-power microwave amplifier used to generate high-power radiofrequency (RF) signals at a specific frequency. It operates on the principle of velocity modulation, where bunches of electrons are alternately accelerated and decelerated within a resonant cavity structure. This modulation process results in the amplification of the RF signal.

anschaef Wed, 03/27/2024 - 15:59 Byline Rende Steerenberg Publication Date Thu, 03/28/2024 - 10:49

CERN and STFC support environmentally sustainable physics

Τετ, 27/03/2024 - 11:29
CERN and STFC support environmentally sustainable physics CERN Director-General, Fabiola Gianotti, and STFC Executive Chair, Mark Thomson, sign a new agreement to support the development of more sustainable particle accelerators (Image: CERN)

On 22 March, CERN and the UK’s Science and Technology Facility Council (STFC) signed a new agreement to collaborate on the research and development of advanced new technologies to make future particle accelerators significantly more sustainable.

Minimising the environmental impact of particle physics activities, ensuring their sustainability and energy efficiency is one of the key recommendations of the last update of the European Strategy for Particle Physics, published in 2020.

“CERN is fully committed to fostering sustainability across its existing and forthcoming projects, actively engaging in a variety of initiatives,” explains Mike Lamont, CERN Director of Accelerators and Technology. “These include sourcing renewable energy, implementing heat recovery schemes, and forging collaborations with industry to explore innovative applications of sustainable technology, such as high-power electricity distribution in various contexts. Our philosophy in this regard aligns well with that of the STFC and we look forward for exploiting the potential of this collaboration – together we are stronger.”

The agreement will act as a framework to better direct CERN and STFC’s funding, expertise and technological investment to minimise environmental impact. It provides guidance and recommendations that consider the entire lifecycle of accelerator facilities from design and construction to operation and decommissioning.

The agreement also outlines a proposal for STFC to establish a new Centre of Excellence in Sustainable Accelerators (CESA) at the Daresbury Laboratory in the UK. CESA would conduct original research in sustainable accelerator technologies and train accelerator scientists, technicians and engineers in the skills required to develop new accelerators with sustainability at the heart of the design.

For more details, see the UKRI website.

katebrad Wed, 03/27/2024 - 10:29 Publication Date Wed, 03/27/2024 - 10:28

Spring at CERN, your photos

Τετ, 27/03/2024 - 11:03
Spring at CERN, your photos Ice-white blossom in front of ISOLDE (Image: Sanje Fenkart) (Image: CERN)

Blossom, blue sky and buildings proved the winning combination for our “spring at CERN” photo competition. Congratulations to Sanje Fenkart from the IR department, who wins not just one CAGI Chocopass, but two, allowing her and a friend to spend a day exploring Geneva and tasting from a range of chocolate shops.

Thank you to all of you who sent in your photos. They are beautiful and are now available in a CC-BY photo collection, shown as a slideshow here:

We’d like to thank the International Geneva Welcome Centre (CAGI) for their sweet (pun intended) gesture of offering these prizes. The CAGI cultural kiosk is located in CERN’s main building and is open from Monday to Friday from 8:30 a.m. to 11:00 a.m. and from 11:30 a.m. to 2:30 p.m. It offers numerous discounts for local activities and events both in Switzerland and in France. Find out more here: https://www.cagi.ch/en/cultural-kiosk-agenda/

katebrad Wed, 03/27/2024 - 10:03 Byline Internal Communication Publication Date Wed, 03/27/2024 - 16:46

AMS’s second new life

Τρί, 26/03/2024 - 14:40
AMS’s second new life

In 2011, the Alpha Magnetic Spectrometer (AMS) was installed on the International Space Station (ISS). Since then, it has recorded more than 200 billion cosmic ray events and, while most of their sources are known, a few signatures in the data could point to dark matter. The detector’s latest upgrade will enable scientists to investigate this further.

AMS collects cosmic ray particles that reach Earth coming either directly from the Sun or from far-away sources such as stars ending in supernovae or black holes. Most of the cosmic rays that AMS detects are protons, but heavy nuclei like iron or silicon also reach the detector. However, one signature is particularly intriguing. AMS has detected an unusually high flux of positrons – the antimatter partners of electrons. Positrons and other antimatter particles are rare in the Universe and hence not expected to be seen in the observed data at the strength found by AMS. Their origin is not yet confirmed; they could come from pulsars (fast rotating remnants of stars that emit regular signals), a yet-unknown astrophysical source or dark matter. The observed positron flux fits very well with dark matter models. But in order to investigate this more accurately, the AMS collaboration is now working on refurbishing the detector.

The main upgrade will be a new detector layer with a higher number of silicon strips that will increase the acceptance of recording infalling particles by 300%. “By 2030, AMS will extend the energy range of the positron flux and reduce the error by a factor of two compared with current data,” says AMS spokesperson Sam Ting (MIT). This will allow the detector to investigate the positron signature even further.

A second important addition will be three new radiative surfaces. Because AMS is exposed to direct sunlight, it was painted white to reflect excess heat and remain at operational temperatures. After 13 years in the demanding conditions of space, the paint has degraded and, to compensate for this, the new radiators will keep AMS cool again.

Astronauts training at NASA’s “Neutral Buoyancy Lab” on a full-scale ISS model submerged under water where they learn to mount the new AMS upgrade parts (Image: Corrado Gargiulo/NASA)

Currently, all the parts of the new upgrade, including electronics and hardware, are being built as “validation” and “qualification” models. If they pass all the tests happening at CERN, INFN Perugia and IABG in Germany, the final flight model will go into production. Astronauts are already training with the prototypes in space-like environments on Earth. In 2026, when the upgrade is launched, the astronauts will mount the new detector parts onto AMS during spacewalks. “Everything is going very, very fast,” says chief engineer Corrado Gargiulo (CERN). “This is a requirement, otherwise we arrive too late at the ISS for the upgrade to make sense.” Indeed, the mission now has an end date. NASA has scheduled the deorbiting of the ISS for 2030 and, until then, AMS will have plenty of cosmic ray events to record to explore the positron signature.

A mock-up detector for the next AMS upgrade, which will be installed during the next anticipated spacewalk for AMS.  Another part of the upgrade includes a large power distribution system (PDS) radiator to restore AMS’s optimal thermal performance. (Image: Chetna Krishna/CERN)

ckrishna Tue, 03/26/2024 - 13:40 Byline Sanje Fenkart Publication Date Tue, 04/02/2024 - 10:00

The delicate balance of lepton flavours

Τρί, 26/03/2024 - 11:33
The delicate balance of lepton flavours

In a talk at the ongoing Rencontres de Moriond conference, the ATLAS collaboration presented the result of its latest test of a key principle of the Standard Model of particle physics known as lepton flavour universality. The precision of the result is the best yet achieved by a single experiment in decays of the W boson and surpasses that of the current experimental average.

Most elementary particles can be classed into groups or families with similar properties. For example, the lepton family includes the electron, which forms the negatively charged cloud of particles surrounding the nucleus in every atom, the muon, a heavier particle found in cosmic rays, and the tau-lepton, an even heavier short-lived particle only seen in high-energy particle interactions.

As far as physicists know, the only difference between these particles is their mass, as generated through their different strengths of interaction with the fundamental field associated with the Higgs boson. In particular, a remarkable feature of the Standard Model is that each lepton type, or “flavour”, is equally likely to interact with a W boson, the electrically charged carrier of the weak force that is one of the four fundamental forces of nature. This principle is known as lepton flavour universality.

High-precision tests of lepton flavour universality, as obtained by comparing the rates of decay of the W boson into an electron and an electron neutrino, into a muon and a muon neutrino or into a tau-lepton and a tau neutrino, are therefore sensitive probes of physics beyond the Standard Model. Indeed, if lepton flavour universality holds, these decay rates should be equal (within negligible mass-dependent corrections).

This can be tested by measuring the ratios of the W boson’s rates of decay into the different lepton flavours. One of the challenges associated with such measurements at the Large Hadron Collider (LHC) is the collection of a pure (“unbiased”) sample of W bosons. In a paper released by Nature Physics in 2021, ATLAS reported the world’s most precise measurement of the ratio of the W boson’s rate of decay into a tau-lepton versus its rate of decay into a muon, demonstrating that collision events in which a pair of top quarks is produced provide an abundant and clean sample of W bosons.

In a recent paper, ATLAS released a new measurement, this time addressing the ratio of the W boson’s rate of decay into a muon versus its rate of decay into an electron. While the combination of all previous measurements showed that this ratio is within about 0.6% of unity, corresponding to equal decay rates, there was still room for improvement.

The new ATLAS result is based on a study of its full dataset from the second run of the LHC, collected between 2015 and 2018. The analysis looked at over 100 million top-quark-pair collision events. The top quark decays promptly into a W boson and a bottom quark, so this sample provides 100 million pairs of W bosons. By counting the number of these events with two electrons (and no muon) or two muons (and no electron), physicists can test whether the W boson decays more often into an electron or a muon.

However, it's not that simple. The Z boson, the electrically neutral carrier of the weak force, can also decay into a pair of electrons or muons, leaving a similar experimental signature to that of a top-quark pair. Since the combined mass of the leptons in Z-boson events clusters around the Z-boson mass of 91 GeV, this background process can be estimated and subtracted.

Moreover, as a result of measurements conducted in the 1990s at CERN’s Large Electron–Positron (LEP) collider, the LHC’s predecessor, and at the Stanford Linear Collider (SLC), the ratio of the Z boson’s rate of decay into two muons versus its rate of decay into two electrons is known to be equal to unity within 0.3%. Thus, in this ATLAS analysis, the Z boson’s decay rate ratio was determined as a reference measurement, allowing researchers to reduce uncertainties coming from the reconstruction of electrons and muons. Additionally, as many measurement uncertainties are similar in the events with two electrons and those with two muons, they were found to have only a minor effect on the measured decay rate ratio.

The final result from this new ATLAS analysis is a ratio of 0.9995, with an uncertainty of 0.0045, perfectly compatible with unity. With an uncertainty of only 0.45%, the result is more precise than all previous measurements combined (see figure below). For now, lepton flavour universality survives intact.

Measurements of the ratio of the W boson’s rate of decay into a muon versus its rate of decay into an electron. The new ATLAS result is shown in the last row as an open blue circle. Previous measurements are shown above using solid symbols, and the Particle Data Group average of all previous results is shown using a black diamond. (Image: ATLAS/CERN) abelchio Tue, 03/26/2024 - 10:33 Byline ATLAS collaboration Publication Date Tue, 03/26/2024 - 10:17

Computer Security: Day of the open firewall

Τρί, 26/03/2024 - 00:22
Computer Security: Day of the open firewall

With ongoing vulnerability scans of CERN’s internet presence performed by an external specialised company, the Computer Security team’s plans to perform penetration testing against selected targets visible to the internet, and the possibility of CERN joining a so-called Bug Bounty programme (a Bulletin article on this will come soon), we are preparing for an increasingly thorough assessment of the weaknesses, misconfigurations and vulnerabilities inside CERN – on the campus network, the technical network and the networks dedicated to the different experiments.

Given that the CERN networks are many, vast and interconnected in a complex manner, with tens of thousands of registered devices, thousands of them regularly or permanently connected, a large proportion of unmanaged “bring-your-own” devices or unpatchable and inherently vulnerable devices of the Internet of Things, a very large number of heterogenous virtual machines and containers running arbitrary applications, and about ten thousand websites leading to millions of webpages, vulnerability scanning and penetration testing of such an environment is complex, complicated and tedious. That’s why we have decided to lower CERN’s outer perimeter firewall protections for 24 hours on the first Monday of next month so that any external third party interested in poking/hacking/breaking into CERN can do so. The open firewall, allowing any incoming traffic, will facilitate not only the work of the aforementioned external company, but also that of the students affiliated with our WhiteHat programme, Bug Bounty hunters hoping for an entry on our Kudos page and any other benign or malicious attacker.

As usual, any ethical party probing CERN during those 24 hours is supposed to stop their activity before any damage or destruction is done and to report all their findings immediately to us so that they can be addressed, controlled, mitigated and fixed. For those cases where the scans and tests are performed by malicious actors, our network-based intrusion detection system connected to the outer perimeter firewall will stay alert and monitor all activities in the hope of identifying their ill-doing well in time, as we managed to in the past. The Computer Security team will, exceptionally, cover its duties 24/7. Of course, we cannot guarantee that no damage will be done by any malicious attacker, but we are counting on the robustness, resilience and up-to-dateness of your systems, devices, virtual machines/containers and websites. This risk is also the reason why we will open the firewall for just 24 hours: this tight time window should keep any collateral damage low.

So, stay tuned for next Monday, 1 April, 00:00 to 23:59, the day when we shall learn more about the security of CERN’s internal networks, and subsequently further improve all the systems connected to it.  

________

Do you want to learn more about computer security incidents and issues at CERN? Follow our Monthly Report. For further information, questions or help, check our website or contact us at Computer.Security@cern.ch.

anschaef Mon, 03/25/2024 - 23:22 Byline Computer Security team Publication Date Mon, 03/25/2024 - 23:22

First observation of photons-to-taus in proton–proton collisions by CMS

Δευ, 25/03/2024 - 17:27
First observation of photons-to-taus in proton–proton collisions by CMS

In March 2024, the CMS collaboration announced the observation of two photons creating two tau leptons in proton–proton collisions. It is the first time that this process has been seen in proton–proton collisions, which was made possible by using the precise tracking capabilities of the CMS detector. It is also the most precise measurement of the tau’s anomalous magnetic moment and offers a new way to constrain the existence of new physics.

The tau, sometimes called tauon, is a peculiar particle in the family of leptons. In general, leptons, together with quarks, make up the “matter” content of the Standard Model (SM). The tau was only discovered in the late 1980s at SLAC, and its associated neutrino – the tau neutrino – completed the tangible matter part upon its discovery in 2000 by the DONUT collaboration at Fermilab. Precise research for the tau is rather tricky though, as its lifetime is very short: it remains stable for only 290·10-15 s (a hundred quadrillionth of a second).

The two other charged leptons, the electron and the muon, are rather well studied. A lot is also known about their magnetic moments and their associated anomalous magnetic moments. The former can be understood as the strength and orientation of an imaginary bar magnet inside a particle. This measurable quantity, however, needs corrections at the quantum level arising from virtual particles tugging at the magnetic moment, deviating it from the predicted value. The quantum correction, referred to as anomalous magnetic moment, is of the order of 0.1%. If the theoretical and experimental results disagree, then this anomalous magnetic moment, al , opens doors to physics beyond the SM.

The anomalous magnetic moment of the electron is one of the most precisely known quantities in particle physics and agrees perfectly with the SM. Its muonic counterpart, on the other hand, is one of the most investigated ones, into which research is ongoing. Although theory and experiments have mostly agreed so far, recent results give rise to a tension that requires further investigation.

For the tau, however, the race is still going. It is especially hard to measure its anomalous magnetic moment, aτ, due to the tau’s short lifetime. The first attempts to measure aτ after the tau’s discovery came with an uncertainty that was 30 times higher than the size of the quantum corrections. Experimental efforts at CERN with the LEP and LHC detectors improved the constraints, reducing the uncertainties to 20 times the size of the quantum corrections.

In collisions, researchers look for a special process: two photons interacting to produce two tau leptons, also called a di-tau pair, which then decay into muons, electrons, or charged pions, and neutrinos. So far both ATLAS and CMS have observed this in ultra-peripheral lead–lead collisions. Now, CMS reports on the first observation of the same process during proton–proton collisions. These collisions offer a higher sensitivity to physics beyond the SM as new physics effects increase with the collision energy. With the outstanding tracking capabilities of the CMS detector, the collaboration was able to isolate this specific process from others, by selecting events where the taus are produced without any other track within distances as small as 1 mm. “This remarkable achievement of detecting ultra-peripheral proton–proton collisions sets the stage for many groundbreaking measurements of this kind with the CMS experiment,” said Michael Pitt, from the CMS analysis team.

This new method offers a new way to constrain the tau anomalous magnetic moment, which the CMS collaboration tried out immediately. While the significance will be improved with future run data, their new measurement places the tightest constraints so far, with higher precision than ever before. It reduces the uncertainty from the predictions down to only three times the size of the quantum corrections. “It is truly exciting that we can finally narrow down some of the basic properties of the elusive tau lepton,” said Izaak Neutelings, from the CMS analysis team. “This analysis introduces a novel approach to probe tau g-2 and revitalises measurements that have remained stagnant for more than two decades,” added Xuelong Qin, another member of the analysis team.

Further material: 3D interactive version of the event display with all tracks here.

sandrika Mon, 03/25/2024 - 16:27 Publication Date Mon, 03/25/2024 - 17:00

World Wide Web at 35

Δευ, 25/03/2024 - 16:36
World Wide Web at 35 Tim Berners-Lee invented and developed the World Wide Web as an essential tool for high energy physics at CERN from 1989 to 1994. Together with a small team he conceived HTML, http, URLs, and put up the first server and the first 'what you see is what you get' browser and html editor. (Image: CERN)

Thirty-five years ago, a young computer expert working at CERN wrote a proposal that combined accessing information with a desire for broad connectivity and openness. This proposal went on to become the World Wide Web (WWW), whose impact on society has been profound.  

Sir Tim Berners-Lee’s first proposal in March 1989 was for an internet-based hypertext system to link and access information across different computers. In November 1990, this “web of information nodes in which the user can browse at will” was formalised as a proposal, “WorldWideWeb: Proposal for a HyperText Project”, by Berners-Lee, together with a CERN colleague, Robert Cailliau. By Christmas that year, Berners-Lee had implemented key components, namely html, http and URL, and created the first Web server, browser and editor (WorldWideWeb). This server is now exhibited in the Laboratory’s new visitor centre, CERN Science Gateway.

CERN released the WWW software into the public domain on 30 April 1993, making it freely available for anyone to use and improve. This decision encouraged the use of the Web, and society to benefit from it.

Now, thirty-five years since his original proposal, Sir Tim Berners-Lee reflects on the web’s trajectory in an open letter and states how we, as engaged citizens, can "re-shape a digital future that prioritises human well-being, equity, and autonomy".

katebrad Mon, 03/25/2024 - 15:36 Publication Date Wed, 03/27/2024 - 16:24

Brazil becomes Associate Member State of CERN

Παρ, 22/03/2024 - 10:06
Brazil becomes Associate Member State of CERN

Brazil has become the first Associate Member State of CERN in the Americas, following official notification that the country has completed its internal approval procedures in respect of the agreement signed in March 2022 granting it that status and of the Protocol on Privileges and Immunities of the Organization. The starting date of Brazil’s status as an Associate Member State is 13 March 2024.

Formal cooperation between CERN and Brazil started in 1990 with the signature of an International Cooperation Agreement, allowing Brazilian researchers to participate in the DELPHI experiment at the Large Electron–Positron Collider (LEP). Over the past decade, Brazil’s experimental particle-physics community has doubled in size. At the four main Large Hadron Collider (LHC) experiments alone, about 200 Brazilian scientists, engineers and students collaborate in fields ranging from hardware and data processing to physics analysis.

Today, Brazilian institutes participate in all the main experiments at the LHC – ALICE, ATLAS, CMS and LHCb and their ongoing and planned upgrades – as well as in ALPHA at the anti-proton decelerator. They are also involved in experiments at ISOLDE, ProtoDUNE at the Neutrino Platform and instrumentation projects such as Medipix. Following on from their participation in the RD51 collaboration, Brazilian teams are also contributing to setting up the DRD1 and DRD3 R&D collaborations for future detectors. Brazilian nationals also participate very actively in CERN training and outreach programmes.

Beyond particle physics, CERN and Brazil’s National Centre for Research in Energy and Materials (CNPEM) have also been formally cooperating since December 2020 on accelerator technology R&D and its applications.

As an Associate Member State, Brazil is entitled to appoint representatives to attend meetings of the CERN Council and the Finance Committee. Its nationals are eligible to apply for limited-duration staff positions and CERN’s graduate programmes, and its industry is entitled to bid for CERN contracts, increasing opportunities for industrial collaboration in advanced technologies.

angerard Fri, 03/22/2024 - 09:06 Publication Date Fri, 03/22/2024 - 17:00

CERN rewarded for its contributions to cloud computing

Πέμ, 21/03/2024 - 17:12
CERN rewarded for its contributions to cloud computing

On 21 March, CERN received the “Top End User” special award by the Cloud Native Computing Foundation (CNCF) for its “forward-looking approach to leveraging cloud native technologies to address future scientific and operational challenges”. Prior recipients of the “Top End User” CNCF award have included Mercedes-Benz, Spotify and Apple.  

Cloud native technologies are software solutions that exploit the basic features of cloud computing – e.g., scalability, flexibility, data resiliency – and allow system engineers to effectively manage complex computing environments with minimal effort. CERN has been a member of the CNCF community since 2020 and is considered an “end user” because it develops cloud native technologies internally but does not sell cloud service externally.

CERN contributes to community-driven cloud computing ecosystems, such as the CNCF, but also runs its own private cloud, which is configured and integrated into the CERN network and authentication services. The organization’s cloud ecosystem is heterogeneous and complex, as Taylor Dolezal, head of ecosystem at CNCF confirmed: “CERN's innovative use of cloud native technologies is a shining example of how open source and collaboration can drive cutting-edge research.”

For more details see the CNCF announcement and the IT README.

katebrad Thu, 03/21/2024 - 16:12 Publication Date Thu, 03/21/2024 - 15:39

Scientists use n_TOF to investigate how cerium is produced in the Universe

Πέμ, 21/03/2024 - 12:42
Scientists use n_TOF to investigate how cerium is produced in the Universe The experimental setup. (Image: n_TOF collaboration)

Cerium is a rare Earth metal that has numerous technological applications, for example in some types of lightbulbs and flat-screen TVs. While the element is rare in Earth’s crust, it is slightly more abundant in the Universe. However, much is unknown about how it is synthesised in stars. Now, in a new study published in Physical Review Letters, the n_TOF collaboration at CERN investigates how cerium is produced in stars. The results differ from what was expected from theory, indicating a need to review the mechanisms believed to be responsible for the production of cerium – and other heavier elements – in the Universe.

“The measurement we carried out enabled us to identify nuclear resonances never observed before in the energy range involved in the production of cerium in stars,” explains Simone Amaducci, of INFN’s Southern National Laboratories and first author of the study. “This is thanks to the very-high-energy resolution of the experimental apparatus at CERN and the availability of a very pure sample of cerium 140.”

The abundance of elements heavier than iron observed in stars (such as tin, silver, gold and lead) can be reproduced mathematically by hypothesising the existence of two neutron capture processes: the slow (s) process and the rapid (r) process. The s process corresponds to a neutron flux of 10 million neutrons per cubic centimetre while the r process has a flux of more than one million billion billion neutrons per cubic centimetre. The s process is theorised to produce about half of the elements heavier than iron in the Universe, including cerium.

CERN’s Neutron Time-of-Flight facility (n_TOF) is designed to study neutron interactions, such as those that occur in stars. In this study, the scientists used the facility to measure the nuclear reaction of the cerium 140 isotope with a neutron to produce isotope 141. According to sophisticated theoretical models, this particular reaction plays a crucial role in the synthesis of heavy elements in stars. Specifically, the scientists looked at the reaction’s cross section: the physical quantity that expresses the probability that a reaction occurs. The scientists measured the cross section at a wide range of energies with an accuracy 5% higher than previous measurements.

The results open up new questions about the chemical composition of the Universe. “What intrigued us at the beginning was a discrepancy between theoretical star models and observational data of cerium in the stars of the M22 globular cluster in the Sagittarius constellation,” explains Sergio Cristallo of INAF’s Abruzzo Astronomical Observatory, who proposed the experiment. “The new nuclear data differs significantly, up to 40%, from the data present in the nuclear databases currently used, definitely beyond the estimated uncertainty.”

These results have notable astrophysical implications, suggesting a 20% reduction in the contribution of the s process to the abundance of cerium in the Universe. This means a paradigm shift is required in the theory of cerium nucleosynthesis: other physical processes that are not currently included would need to be considered in calculations of stellar evolution. Furthermore, the new data has a significant impact on scientists’ understanding of the chemical evolution of galaxies, which also affects the production of heavier elements in the Universe.

ndinmore Thu, 03/21/2024 - 11:42 Publication Date Thu, 03/21/2024 - 17:06

CERN launches the White Rabbit Collaboration

Πέμ, 21/03/2024 - 11:12
CERN launches the White Rabbit Collaboration The White Rabbit community gathers to celebrate the launch of the White Rabbit Collaboration. (Image: CERN)

White Rabbit (WR) is a technology developed at CERN, in collaboration with institutes and companies, to synchronise devices in the accelerators down to sub-nanoseconds and solve the challenge of establishing a common notion of time across a network. Indeed, at a scale of billionths of a second, the time light takes to travel through a fibre-optic cable and the time the electronics take to process the signal are no longer negligible. To avoid potential delays, the co-inventors of White Rabbit designed a new ethernet switch.

First used in 2012, the application of this fully open-source technology has quickly expanded outside the field of particle physics. In 2020, it was included in the worldwide industry standard known as Precision Time Protocol (PTP), governed by the Institute of Electrical and Electronics Engineers (IEEE).

What’s more, CERN recently launched the White Rabbit Collaboration, a membership-based global community whose objective is to maintain a high-performance open-source technology that meets the needs of users and to facilitate its uptake by industry. The WR Collaboration will provide dedicated support and training, facilitate R&D projects between entities with common interests and complementary expertise and establish a testing ecosystem fostering trust in products that incorporate the open-source technology. At CERN, the WR Collaboration Bureau – a dedicated team composed of senior White Rabbit engineers and a community coordinator – will facilitate the day-to-day running of the Collaboration’s activities and support its members.

“A key distinctive feature of White Rabbit, as opposed to other technologies that have been developed since, is that it is open source and based on standards”, says Javier Serrano, Chair of the White Rabbit Collaboration Board and co-inventor of the technology. Companies and institutes can therefore adapt it to their needs and incorporate it in their products and systems, while the technology, in turn, benefits from a large community of developers. “The first step to foster industry uptake was to include WR concepts in the IEEE standard. Through this endeavour, we established many links with industry,” says Maciej Lipinski, Chair of the White Rabbit Collaboration Council and senior White Rabbit engineer at CERN.

White Rabbit is used in the finance sector as well as in many research infrastructures, and it is currently being evaluated for application in the future quantum internet. The technology could also play a key role in the future landscape of global time dissemination technologies, which currently rely heavily on satellites. The infrastructure for the dissemination of time is essential to the economy and underpins most critical national infrastructure. Governments and industry across the globe are therefore striving to find alternatives to distribute a reference time, such as the one WR could offer via optical fibre, with telecom and power grid companies starting to test WR in their networks.

The WR Collaboration comes at a moment when many sectors are undergoing a profound transformation with regards to their timing technology. “The WR Collaboration will provide a neutral gathering point around this open-source technology and define a long-term common vision, establishing a solid ground from which innovation can thrive,” continues Amanda Diez Fernandez from CERN’s Knowledge Transfer group and the White Rabbit Community Coordinator.

To learn more about how to join the White Rabbit Collaboration, go to: www.white-rabbit.tech

_______

From 21–22 March, the White Rabbit community met at CERN to celebrate the launch of the WR Collaboration. To find out more, listen to the recorded talks of the event.

ndinmore Thu, 03/21/2024 - 10:12 Publication Date Fri, 03/22/2024 - 14:10

Observing accelerator resonances in 4D

Τρί, 19/03/2024 - 13:09
Observing accelerator resonances in 4D CERN’s Super Proton Synchrotron in 2022. (Image: CERN)

Whether in listening to music or pushing a swing in the playground, we are all familiar with resonances and how they amplify an effect – a sound or a movement, for example. However, in high-intensity circular particle accelerators, resonances can be an inconvenience, causing particles to fly off their course and resulting in beam loss. Predicting how resonances and non-linear phenomena affect particle beams requires some very complex dynamics to be disentangled.

For the first time, scientists at the Super Proton Synchrotron (SPS), in collaboration with scientists at GSI in Darmstadt, have been able to experimentally prove the existence of a particular resonance structure. While it had previously been theorised and appeared in simulations, this structure is very difficult to study experimentally as it affects particles in a four dimensional space*. These latest results, published in Nature Physics, will help to improve the beam quality for low-energy and high-brightness beams for the LHC injectors at CERN and the SIS18/SIS100 facility at GSI, as well as for high-energy beams with large luminosity, such as the LHC and future high-energy colliders.

“With these resonances, what happens is that particles don’t follow exactly the path we want and then fly away and get lost,” says Giuliano Franchetti, a scientist at GSI and one of the paper’s authors. “This causes beam degradation and makes it difficult to reach the required beam parameters.”

The idea to look for the cause of this emerged in 2002, when scientists at GSI and CERN realised that particle losses increased as accelerators pushed for higher beam intensity. “The collaboration came from the need to understand what was limiting these machines so that we could deliver the beam performance and intensity needed for the future,” says Hannes Bartosik, a scientist at CERN and another of the paper’s authors.

Over many years, theories and simulations were developed to understand how resonances affected particle motion in high-intensity beams. “It required an enormous simulation effort by large accelerator teams to understand the effect of the resonances on beam stability,” says Frank Schmidt at CERN, also one of the paper’s authors. The simulations showed that resonance structures induced by coupling in two degrees of freedom are one of the main causes of beam degradation.

It took a long time to devise how to look for these resonance structures experimentally. This is because they are four dimensional* and require the beam to be measured in both the horizontal and the vertical planes to see if they exist. “In accelerator physics, the thinking is often in only one plane,” adds Franchetti.

Figure 1: Conceptually visualising 4D resonance structures is much more complicated than one-dimensional resonances. This image shows the 4D resonance structure measured in the SPS. (Image: H. Bartosik, G. Franchetti and F. Schmidt, Nature Physics)

To measure how resonances affect particle motion, the scientists used beam position monitors around the SPS. Over approximately 3000 beam passages, the monitors measured whether the particles in the beam were centred or more to one side, in both the horizontal and vertical planes. The resonance structure that was found is shown in Figure 1.

“What makes our recent finding so special is that it shows how individual particles behave in
a coupled resonance,” continues Bartosik. “We can demonstrate that the experimental findings agree with what had been predicted based on theory and simulation.”

While the existence of the coupled resonance structures has now been observed experimentally, much more remains to be done to reduce their detrimental effect. “We’re developing a theory to describe how particles move in the presence of these resonances,” continues Franchetti. “With this study, coupled with all the previous ones, we hope we will get clues on how to avoid or minimise the effects of these resonances for current and future accelerators.”

*Space refers to “phase space” – the space in which all possible states of a system are represented

Read the paper here

ndinmore Tue, 03/19/2024 - 12:09 Byline Naomi Dinmore Publication Date Wed, 03/20/2024 - 11:15

Σελίδες

Πανεπιστήμιο Κρήτης - Τμήμα Φυσικής - Πανεπιστημιούπολη Βουτών - TK 70013 Βασιλικά Βουτών, Ελλάδα
τηλ: +30 2810 394300 - email: chair@physics.uoc.gr