CERN: News en LS2 report: waiting for antiprotons... <span>LS2 report: waiting for antiprotons...</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Thomas Hortala</div> </div> <span><span lang="" about="/user/21331" typeof="schema:Person" property="schema:name" datatype="">thortala</span></span> <span>Wed, 10/21/2020 - 13:08</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p><em>“The Antiproton Decelerator (</em><a href=""><em>AD</em></a><em>) is like CERN in miniature: it has two synchrotrons circulating particles and five experiments at the end of transfer lines, all located in a semi-buried hall.</em> <em>It’s small, but it’s a great place to work!”</em> François Butin, Technical Coordinator for the AD (also known as the antimatter factory), might have added that it is a CERN in reverse: in a laboratory that works to accelerate particles, the AD and its new colleague ELENA (<em>Extra Low Energy Antiproton deceleration ring</em>) decelerate particles so that they reach very low energies. Three years after <a href="">the first antiprotons were circulated in ELENA</a>, the new ring has been able to inject H<sup>-</sup> ions (used in place of antimatter until the restart of the Proton Synchrotron) and deliver them to the GBAR and ALPHA experiments for the first time. This is possible thanks to the new transfer lines that have been installed during Long Shutdown 2 (LS2).</p> <p>Despite its modest 30-metre circumference, ELENA is the new keystone of the antimatter factory. ELENA receives protons from the AD with an energy of 5.3 MeV and decelerates them to 0.1 MeV, which avoids the need for deceleration systems that are responsible for particle loss.</p> <p>The new GBAR experiment has been connected to ELENA since it was installed in 2017, but the other experiments remained connected to the AD. Since November 2018, LS2 has largely been spent dismantling and then replacing the old transfer lines between ELENA and ALPHA, AEGIS, ASACUSA, BASE and other potential future experiments.</p> <p>Far from being exact copies of their predecessors, the new transfer lines have introduced innovative technology to the antimatter factory: the old electromagnets have been replaced by dipole and quadrupole electrostatic plates, which are enough to guide the particles that have been slowed down to such an extent. By not using magnet systems, the antimatter factory has opted for a solution that is economical and frees up space to increase the density of the quadrupoles, thereby further stabilising the beam. There have also been innovations in instrumentation: the previous GEM (Gas Electron Multiplier) beam control systems have made way for Secondary Emission Monitors (SEM), which allow increased and non-destructive control of the beam along the entire transfer lines.</p> <p>“<em>The experiments and operations team will have access to a denser, more stable and better controlled beam of antiprotons that have been slowed down by ELENA</em>”, explains Christian Carli, ELENA project leader. The experiments will be able to benefit from these advantages once the Proton Synchrotron (PS) and the AD target (also the subject of major renovation) start up again.</p> <p>The first diagnostics of the H<sup>-</sup> ion beams travelling through the new lines to the experiments are very positive: “<em>The optics are good, as is the size of the beams. After two years working towards this goal, it’s so rewarding to see the particles injected into the lines!”,</em> says Laurette Ponce, who is responsible for AD and ELENA operations. For Laurette and the operations team, it’s the beginning of several months of work to characterise the ion beam, before the AD can supply antiprotons to the new transfer lines and the experiments linked to ELENA.</p> </div> Wed, 21 Oct 2020 11:08:38 +0000 thortala 155876 at Introducing SPARKS! Serendipity forum at CERN <span>Introducing SPARKS! Serendipity forum at CERN </span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Claudia Marcelloni de Oliveira</div> </div> <span><span lang="" about="/user/21331" typeof="schema:Person" property="schema:name" datatype="">thortala</span></span> <span>Tue, 10/20/2020 - 11:54</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>On 26 November, CERN will launch a multidisciplinary science innovation forum and public event: <a href=""><em>Sparks! Serendipity forum at CERN</em></a>. For two days a year, Sparks will bring together renowned scientists from diverse fields around the world, along with decision-makers, representatives of industry, philanthropists, ethicists and the public to address some of the big questions of our time. The forum aims to spark innovation in issues related to science, technology, engineering and mathematics that are relevant to society and that further CERN’s mission of science for peace.</p> <p>The theme of the first Sparks event, which will take place on 17-18 September 2021 at CERN and at HEAD (Geneva University of Art and Design), is future intelligence. The analysis and interpretation of vast amounts of information is at the core of research at CERN. When searching for tiny signals in vast datasets, CERN scientists must avoid bias and embrace novel technologies. Thus, as the challenges faced by particle-physics intensify, CERN has the opportunity to bring together big data and artificial intelligence (AI). After years of mining the LHC data streams, CERN experts will bring valuable insight and contributions to the Sparks! debates, while also learning a lot from participants. </p> <p><strong>Join us on 26 November from 4 p.m. (CET) for the <a href="">virtual launch of Sparks</a>.</strong> Professors Anima Anandkumar, Jürgen Schmidhuber, Francesca Rossi and Stuart Russel will comment on the current status of the field of AI research today, setting the scene for the discussion about the future of the field during the event in 2021. Host Bruno Giussani, Global Curator of TED, will interview CERN AI experts Jennifer Ngadiuba, Sofia Vallercosa, Michael Kagan and Michael Doser on the topics we aim to address in 2021, including how CERN and science in general can benefit from AI.</p> <p>Sparks is part of the CERN &amp; Society programme. CERN &amp; Society activities are only possible thanks to support received from partners, in particular Rolex and its long-standing association with the Organization. The 2020-2021 Sparks event is also supported by Edmond de Rothschild, with support from the Didier et Martine Primat Foundation.</p> <p>For more information about the event, including a list of the confirmed participants in the Future Intelligence forum and public event on 17-18 September 2021: <a href=""></a> </p> </div> Tue, 20 Oct 2020 09:54:19 +0000 thortala 155869 at LS2 Report: increased cryogenic power at LHC Point 4 <span>LS2 Report: increased cryogenic power at LHC Point 4</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Anaïs Schaeffer</div> </div> <span><span lang="" about="/user/151" typeof="schema:Person" property="schema:name" datatype="">anschaef</span></span> <span>Wed, 10/14/2020 - 11:37</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>The LHC is one of the coldest places on Earth. The 1.9 K (-271.3 °C) operating temperature of its main magnets is even lower than the 2.7 K (-270.5 °C) of outer space. To get the LHC to this temperature, 120 tonnes of liquid helium flow around a closed circuit in the veins of the accelerator.</p> <p>The <a href="">LHC cooling system</a> is made up of cryogenic islands with eight helium refrigerators in total. Each even-numbered point on the accelerator (Points 2*, 4, 6 and 8) has two refrigerators, one dating from the LEP (Large Electron-Positron Collider) era, and another newer refrigerator dating from the start-up of the LHC. The LEP refrigerator is composed of two cold boxes – one on the surface and the other downstream in the tunnel, which cool the helium from room temperature to 20 K (-253.15 °C) and from 20 K to 4.5 K respectively – and a unit located in a cavern generating superfluid helium at 1.9 K.</p> <p>“These refrigerators date back to 1994, but they have undergone a number of upgrades since then, in particular in preparation for the LHC in 2006”, says Emmanuel Monneret, an engineer from the TE-CRG group working on the refrigeration project. “On that occasion, their cooling power was increased from 12 to 16 kW at 4.5 K.”</p> <p>During LS2, further upgrades have been carried out on the LEP refrigerator at Point 4, increasing its cooling power to 18 kW at 4.5 K, in preparation for the <a href="">HL-LHC</a> (High-Luminosity LHC): “The Point 4 refrigerators are crucial for the HL-LHC, because as well as cooling sectors 3-4 and 4-5, they must also cool the sections where the radiofrequency cavities are installed, which require a considerable amount of cooling,” continues Emmanuel Monneret.</p> <p>To achieve this important extra 2 kW, the four turbines and heat exchangers in each of the cold boxes at Point 4 have been replaced with higher-performing equivalents. This task was relatively straightforward to carry out for the cold box at the surface, which is easily accessible to workers (see photo 1), but more arduous for the cold box in the tunnel. “We had not anticipated that it would be impossible to get inside the tunnel cold box, which is much more compact than the one on the surface,” Emmanuel Monneret explains. “Working in close collaboration with the manufacturer, we eventually found a solution to allow us to replace the turbines and exchangers from the outside.”</p> <figure class="cds-image" id="CERN-HOMEWEB-PHO-2020-128-1"><a href="//" title="View on CDS"><img alt=",Accelerators" src="//" /></a> <figcaption>The new turbines and their heat exchangers, recently installed in the lower cold box at Point 4. The turbines are mounted on an interface that was specially developed to allow them to be installed from outside the cold box.<span> (Image: CERN)</span></figcaption></figure><p>Thanks to a new interface (see photo 2) developed by the manufacturer in just a few months, the team in charge of the project was able to install the turbines and exchangers without having to connect them from inside the cold box. This new equipment, which has just been commissioned, will be operational by the end of the month.</p> <p><em>*To be precise, there is one helium refrigerator at Point 2 and another at Point 1.8.</em><br />  </p> <table border="1" cellpadding="1" cellspacing="1" style="width: 570px;"><tbody><tr><td><span class="line-of-lines"><strong>The LHC has started cool-down </strong><br /> The post-LS2 cool-down of the LHC began on 5 October in sector 4-5. Cool-down is carried out in three stages: from room temperature to 80 K, from 80 K to 4.5 K, and finally from 4.5 K to 1.9 K. It takes around seven weeks for a sector to be cooled to 1.9 K, including checks and adjustments of the instrumentation and the process control systems. The sectors are cooled gradually, one after another. The LHC should therefore reach its nominal temperature in spring 2021.</span><span class="line-of-lines"> </span></td> </tr></tbody></table><p> </p> </div> Wed, 14 Oct 2020 09:37:22 +0000 anschaef 155834 at CERN begins to manufacture its own surgical masks <span>CERN begins to manufacture its own surgical masks</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Anaïs Schaeffer</div> </div> <span><span lang="" about="/user/151" typeof="schema:Person" property="schema:name" datatype="">anschaef</span></span> <span>Tue, 10/13/2020 - 12:28</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>CERN has recently procured a machine to manufacture surgical masks. This will allow the Organization to provide masks for everyone working on the CERN sites and to ensure the safety of each and every one of us during the COVID-19 pandemic.</p> <p>The machine was installed in Building 947 in September and several members of the EN-SMM group (Survey, Mechatronics and Measurements) have been trained to operate it. The aim is to be able to produce 400,000 masks a month.</p> <p>“CERN, like everyone, was faced with a shortage of surgical masks at the start of the COVID-19 pandemic,” Roberto Losito, head of the EN Department, recalls. “Fortunately, in April we were able to order hundreds of thousands of masks, but the prices were exorbitant. We therefore decided to procure our own manufacturing machine: it will be much more economical in the long term and will ensure we have enough regulation-compliant masks for everyone at CERN.”</p> <p>The masks produced at CERN are being tested at a French laboratory, in accordance with the EN 14683 regulations, and will receive the CE marking, which guarantees that the masks meet European Union requirements.</p> <p>We would like to remind you that it is obligatory at CERN to <a href=";">wear a mask</a> both inside and outside if two-metre physical distancing cannot be observed.</p> <p>____<br /><em>For more information on CERN’s COVID-19 health and safety measures, please visit <a class="bulletin" href="">this page</a>. All information related to COVID-19 is available <a class="bulletin" href="">here</a>.</em></p> </div> Tue, 13 Oct 2020 10:28:27 +0000 anschaef 155825 at From cryogenics to combatting COVID <span>From cryogenics to combatting COVID</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Linn Tvede</div> </div> <span><span lang="" about="/user/21331" typeof="schema:Person" property="schema:name" datatype="">thortala</span></span> <span>Tue, 10/13/2020 - 16:15</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>As an intergovernmental organisation, CERN establishes its own safety rules to function properly, in line with best practices and regulations in the Host States. After building his expertise for nine years within HSE, Andre Henriques currently contributes to shaping the technical aspects of CERN’s Safety Rules.</p> <p>In addition to drafting safety measures at CERN, Andre also leads the <a href="">Kryolize Project</a>. This initiative aims to harmonise the approach to the sizing of safety valves for cryogenics applications at CERN via software developed with support from the <a href="">Knowledge Transfer (KT) fund</a>. The software goes hand in hand with experiments and measurements to improve the state of the art within cryogenics safety through an R&amp;D collaboration with the Karlsruhe Institute of Technology. “The interaction with KT was great. They helped us secure funding for the project, enabling us to get to the next stage,” explains Andre.</p> <p>Although Kryolize was initially developed for CERN, word spread across the community and the software garnered interest from other institutes. Andre worked closely with KT to publicise the technology and establish collaborations. Legal advisors helped set up 11 <a href="">licence agreements</a> with seven academic and four commercial entities. To further improve the design parameters of safety devices, phase two of the Kryolize Project will start in 2021.</p> <p>As an HSE expert, Andre’s knowledge transfer activities extend beyond cryogenics software. He has also been involved in CERN’s efforts against COVID-19 through the <a href="">“Help to society”</a> activities. As the HSE representative within the CERN against COVID task force, Andre contributed to initiatives such as the “<a href="">High-Energy Ventilator</a>” (HEV), a ventilator developed with CERN equipment and knowledge intended for hospitals around the world. Face shields and masks were also donated to local communities and further knowledge transfer is currently planned for some of the designs through <a href="">CERN’s Open Hardware Licence</a>.</p> <p><strong>Find out more about how to get involved in CERN’s Knowledge Transfer activities </strong><a class="bulletin" href=""><strong>here</strong></a><strong>.</strong></p> <p><strong><img alt="KT spotlight poster " data-entity-type="file" data-entity-uuid="a57721aa-1a90-4fb4-8c39-7fe345bd7a4c" src="/sites/" /></strong></p> </div> Tue, 13 Oct 2020 14:15:52 +0000 thortala 155831 at Taking stock of data privacy at CERN <span>Taking stock of data privacy at CERN</span> <span><span lang="" about="/user/151" typeof="schema:Person" property="schema:name" datatype="">anschaef</span></span> <span>Tue, 10/13/2020 - 11:49</span> <div class="field field--name-field-p-news-display-list-cds field--type-cerncdsmedia field--label-hidden field--item"><figure class="cds-image" data-record-id="2741310" data-filename="DataPrivacy" id="CERN-HOMEWEB-PHO-2020-125-1"> <a href="//" title="View on CDS"> <img alt="Taking stock of data privacy at CERN" src="//"/> </a> <figcaption> <span> (Image: CERN)</span> </figcaption> </figure></div> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><figure class="cds-image align-right" id="CERN-HOMEWEB-PHO-2020-125-1"><a href="//" title="View on CDS"><img alt=",Miscellaneous" src="//" /></a><figcaption><span>(Image: CERN)</span></figcaption></figure><p>In June 2017, our Director-General, Fabiola Gianotti, stated that taking all measures possible to protect personal data “is vital for maintaining the trust of the individuals sharing their information with us, and demonstrating that this laboratory applies the same high-level standards that we apply to our research to everything else we do”. Operational Circular 11 (<a href="">OC 11</a>), which describes the data-privacy rights and obligations at CERN, came into force on 1 January 2019 and was a great start to improving data privacy. However, much remains to be accomplished to protect personal data.</p> <p>The Data Privacy Coordination Committee (DPCC), a dedicated entity to coordinate data privacy at CERN, was created in 2018 to define common approaches to the implementation of the data-privacy rights and obligations. Each department has nominated a representative, the Departmental Data Privacy Protection Coordinator (see <a class="bulletin" href="">list of members</a>), who form the DPCC together with members of the Legal Service, the Staff Association and the Office of Data Privacy (<a href="">ODP</a>).</p> <p>Since its inception in 2018, the DPCC has achieved an impressive amount of objectives. For instance, in 2019, an inventory of all CERN services dealing with personal data was carried out. It revealed that 560 such services are currently in existence. From that catalogue, the members of the DPCC coordinated the establishment of privacy notices that explain what we do with and how we protect personal information given to us in confidence.</p> <p>With regard to the day-to-day management, the DPCC has developed a set of specific procedures to guide people when confronted with aspects of data privacy in their work. One example is a procedure for organising events, something that many of us at CERN may be involved with at some point. The <a class="bulletin" href="">ODP website</a> offers detailed and newly reviewed information on data-privacy protection, while the <a class="bulletin" href="">FAQ page</a> provides answers to specific questions. The <a class="bulletin" href="">Admin e-guide</a>, with its new sub-chapter dedicated to data privacy procedures, focuses on the practical implementation of OC11. Data-privacy notices can be found on <a href="">Service Now</a>.</p> <p>The DPCC is working on many additional measures that are essential for the successful implementation of OC11. High-priority measures include developing the “Privacy by design” policy and procedure, reviewing the current e-learning course to align it with the OC11 and establishing data-retention guidelines.</p> <div class="blockquote">Having a framework such as OC11 and all the supporting measures in place is very good, but alone they are not enough. We need the assistance and cooperation of each and every one at CERN, and we would like to invite you to join the DPCC team in this CERN-wide endeavour to protect the privacy of personal data.</div> <p class="text-align-right"><em>Anne Kerhoas, Rachel Bray</em></p> </div> Tue, 13 Oct 2020 09:49:28 +0000 anschaef 155824 at Council week, accelerator restart and COVID-19 measures: your questions answered <span>Council week, accelerator restart and COVID-19 measures: your questions answered </span> <span><span lang="" about="/user/21331" typeof="schema:Person" property="schema:name" datatype="">thortala</span></span> <span>Tue, 10/13/2020 - 08:00</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>On Thursday, 8 October, the Director-General Fabiola Gianotti addressed the CERN community alongside members of the directorate. They presented the conclusions of the September Council session and outlined the current situation of the Organization and its expected evolution, in light of the <a href="">Update of the European Strategy for Particle Physics</a>. The meeting was broadcast via Webcast and consisted of presentations by Fabiola Gianotti, Frédérick Bordry, Director for Accelerators and Technology, Eckhard Elsen, Director for Research and Computing and James Purvis, Human Resources Department Head. The presentations were followed by a questions and answers session.</p> <p>Fabiola Gianotti introduced the new directorate - freshly appointed by the CERN Council -  discussed the financial situation of the Organization, the scientific strategy of the Laboratory for the 2021-2025 period and announced the imminent start of the construction of CERN <a href="">Science Gateway</a>. The meeting was also an opportunity to present the schedule for the restart of the accelerators as well as the latest findings by the experiments, among which LHCb’s <a href="">time-dependent matter-antimatter asymmetry discovery</a> and ATLAS and CMS’s <a href="">detection of a Higgs boson’s decay into a pair of muons</a>.</p> <p>Much of the meeting was dedicated to the COVID-19 safety and HR-related measures dictated by the current health situation in the Member States and beyond. James Purvis and Doris Forkel-Wirth, Head of the HSE Unit, reasserted CERN’s foremost commitment to ensuring the safety of its community, highlighting that no evidence for on-site infections had been established since the start of the pandemic. Teleworking, leave management, the restaurant situation, quarantine and travel restriction rules were then addressed in detail during the questions and answers section.</p> <p>You can consult the presentations and watch the full recording of the meeting <a class="bulletin" href="">here</a>.</p> </div> Tue, 13 Oct 2020 06:00:09 +0000 thortala 155822 at ALICE honours its thesis award winners <span>ALICE honours its thesis award winners</span> <span><span lang="" about="/user/21331" typeof="schema:Person" property="schema:name" datatype="">thortala</span></span> <span>Fri, 10/09/2020 - 10:11</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>On 23 September, the ALICE collaboration celebrated its best PhD theses, which are selected based on the excellence of the results obtained, the quality of the thesis manuscript, and the importance of the contribution to the collaboration.</p> <p>Out of the 11 outstanding PhD theses received by the selection committee, two theses stood out: <strong>Fabrizio Grosa</strong>’s, entitled “<a href=""><em>Strange and non-strange D-meson production in pp, p-Pb, and Pb-Pb collisions with ALICE at the LHC</em></a>”, and <strong>Arild Velure’s</strong> - “<a href=""><em>Design, Verification and Testing of a Digital Signal Processor for Particle Detectors</em></a>”.</p> <p>The winners were congratulated by ALICE Spokesperson, Luciano Musa, the Collaboration Board Chair, Silvia Masciocchi, and the Chairs of the Thesis Committee, Giuseppe Bruno and Philippe Crochet. Luciano awarded the certificates and prizes to Fabrizio and Arild, who then presented their work.</p> <p>Fabrizio Grosa (Turin Polytechnic) analysed vast data on the production of several particle species in different colliding systems as part of his doctoral research. His results contributed to five published ALICE papers, with two more on the way. Fabrizio has also made significant contributions to the upgrade project of the ALICE Inner Tracking System for the forthcoming LHC runs, working on alignment procedures and physics performance studies.</p> <p>Hailing from Bergen University, Arild Velure worked on the design of the so-called SAMPA ASIC, a complex mixed-signal chip that has become the state-of-the-art readout for gaseous detectors like the ALICE Time Projection Chamber and the muon tracking chambers. He made significant contributions to the ASIC specifications as well as to the design and implementation of the detector front-end cards. Arild’s research is of paramount importance to the success of the forthcoming ALICE high-rate data-taking campaign.</p> </div> Fri, 09 Oct 2020 08:11:35 +0000 thortala 155810 at CMS sees evidence of top quarks in collisions between heavy nuclei <span>CMS sees evidence of top quarks in collisions between heavy nuclei</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Ana Lopes</div> </div> <span><span lang="" about="/user/159" typeof="schema:Person" property="schema:name" datatype="">abelchio</span></span> <span>Fri, 10/09/2020 - 09:10</span> <div class="field field--name-field-p-news-display-list-cds field--type-cerncdsmedia field--label-hidden field--item"><figure class="cds-image" data-record-id="2740819" data-filename="HIN-19-001_black" id="CMS-PHO-EVENTS-2020-026-2"> <a href="//" title="View on CDS"> <img alt="CMS Event display of top quarks in Lead-Lead collisions" src="//"/> </a> <figcaption> Event display of a candidate tt¯ event measured in PbPb collisions where each top quark decays into a bottom quark and a W boson. The b quarks and W bosons, in turn, produce jets and leptons, respectively. The event is interpreted as originating from the dilepton decay chain tt¯→(bW+)(b¯W−)→(be+ν)(b¯μ−ν). <span> (Image: CERN)</span> </figcaption> </figure></div> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>The CMS collaboration has seen evidence of top quarks in collisions between heavy nuclei at the <a href="/science/accelerators/large-hadron-collider">Large Hadron Collider</a> (LHC).</p> <p>This isn’t the first time this special particle – the heaviest known elementary particle – has “made an appearance” at particle colliders. The top quark was first observed in proton–antiproton collisions at the Tevatron collider 25 years ago, and has since been spotted and studied in proton–proton and proton–nucleus collisions at the LHC. But the new finding, described in a <a href="">paper</a> just accepted for publication in <em>Physical Review Letters</em>, is sure to excite experimentalists and theorists alike, for analysis of top quarks in heavy-nuclei collisions offers a new and unique way to study the quark–gluon plasma that forms in these collisions and is thought to have existed in the early moments of the universe. In addition, such analysis could cast new light on the arrangement of quarks and gluons inside heavy nuclei.</p> <p>There isn’t exactly a shortage of particles, or “probes”, with which to investigate the quark–gluon plasma. The LHC experiments have long been using several types of particle to study the properties of this extreme state of matter, in which quarks and gluons are not confined within composite particles but instead roam like particles in a liquid with small frictional resistance. But all of the existing probes provide time-averaged information about the plasma. By contrast, the top quark, owing to the particular way in which it transforms, or “decays” into other particles, can provide snapshots of the plasma at different times of its lifetime.</p> <p>“Faster-moving top quarks provide later-time snapshots. By assembling snapshots taken with top quarks at a range of different speeds, we hope that it will eventually be possible to create a movie of the quark–gluon plasma’s evolution,” explains CERN-based researcher Guilherme Milhano, who co-authored a theoretical <a href="">study</a> on probing the quark–gluon plasma with top quarks. “The new CMS result represents the very first step down that road.”</p> <p>The CMS collaboration saw evidence of top quarks in a large data sample from lead–lead collisions at an energy of 5.02 TeV. The team searched for collisions producing a top quark and a top antiquark. These quarks decay very quickly into a W boson and a bottom quark, which in turn also decay very rapidly into other particles. The CMS physicists looked for the particular case in which the final decay products are charged leptons (electrons or their heavier cousins muons) and “jets” of multiple particles originating from bottom quarks.</p> <p>After isolating and counting these top–antitop collision events, CMS estimated the probability for lead–lead collisions to produce top–antitop pairs via charged leptons and bottom quarks. The result has a statistical significance of about four standard deviations, so it doesn’t yet cross the threshold of five standard deviations that is required to claim observation of top-quark production. But it represents significant evidence of the process – there’s only a 0.003% chance that the result is a statistical fluke. What’s more, the result is consistent with theoretical predictions, as well as with extrapolations from previous measurements of the probability in proton–proton collisions at the same collision energy.</p> <p>“Our result demonstrates the capability of the CMS experiment to perform top-quark studies in the complex environment of heavy-nuclei collisions,” says CMS physicist Georgios Krintiras, a postdoctoral researcher at the University of Kansas, “and it’s the first stepping stone in using the top quark as a new and powerful probe of the quark–gluon plasma.”</p> <p>______</p> <p><em>Read more on the <a class="bulletin" href="">CMS website</a>.</em></p> </div> Fri, 09 Oct 2020 07:10:14 +0000 abelchio 155809 at LHCb sees new form of matter–antimatter asymmetry in strange beauty particles <span>LHCb sees new form of matter–antimatter asymmetry in strange beauty particles</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Ana Lopes</div> </div> <span><span lang="" about="/user/159" typeof="schema:Person" property="schema:name" datatype="">abelchio</span></span> <span>Tue, 10/06/2020 - 13:43</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>The observed excess of matter over <a href="/science/physics/antimatter">antimatter</a> in the Universe is an enduring puzzle in physics. The imbalance implies a difference in the behaviour of matter and antimatter particles. This difference, or “asymmetry”, is known as CP violation and is a fundamental part of the <a href="/science/physics/standard-model">Standard Model</a> of particle physics. But the amount of CP violation predicted by the model and observed so far in experiments is too small to explain the cosmic imbalance, suggesting the existence of as-yet-unknown sources and manifestations of CP violation beyond the Standard Model.</p> <p>At <a href="">the nineteenth beauty conference</a> last month and at <a href="/events/time-dependent-cp-violation-bs0-decays-lhcb">a seminar today at CERN</a>, the LHCb collaboration reported the first observation of so-called time-dependent matter–antimatter asymmetry in particles known as B<sub>s</sub><sup>0</sup> mesons, which contain a beauty antiquark and a strange quark.</p> <p>CP violation was first observed more than five decades ago in particles called K<sup>0</sup> mesons, and has since been observed in other types of particle – including in B<sup>0</sup> mesons in 2001 by experiments at the SLAC laboratory in the US and the KEK laboratory in Japan, and <a href="/news/press-release/physics/lhcb-sees-new-flavour-matter-antimatter-asymmetry">recently </a>by the LHCb collaboration in D<sup>0</sup> mesons. The effect can manifest itself in two forms: time-integrated and time-dependent. In the time-integrated form, the number of transformations, or “decays”, of a matter particle into certain particles differs from that of the corresponding antimatter particle. In the time-dependent form, the violation varies with the particle’s lifetime due to the spontaneous oscillation of the particle into its antiparticle and back.</p> <p>The new LHCb study provides the first observation of time-dependent CP violation in B<sub>s</sub><sup>0</sup> mesons, in their decays into charged K mesons. The result, obtained by combining data collected during the first and second runs of the <a href="/science/accelerators/large-hadron-collider">Large Hadron Collider</a>, has a statistical significance of 6.7 standard deviations, which is beyond the threshold of 5 standard deviations used by particle physicists to claim an observation.</p> <p>“The B<sub>s</sub><sup>0</sup> mesons oscillate between particle and antiparticle three thousand billion times per second, but the excellent resolution of our detector made it possible to observe the effect of these oscillations. Our observation of time-dependent CP violation in B<sub>s</sub><sup>0</sup> mesons represents a further milestone in the study of the differences between matter and antimatter,” says LHCb spokesperson Chris Parkes, “adding to our previous observation of time-integrated CP violation in these mesons.”</p> <p>The next steps will be to compare the measurement with other measurements of CP violation and with predictions from the Standard Model and beyond. It’s only after researchers make these comparisons that they will be able to tell whether or not the new measurement hides any surprises that might help to explain the matter–antimatter imbalance in the universe.</p> <p>_____</p> <p><em>Read more on the <a class="bulletin" href="">LHCb website</a>.</em></p> </div> Tue, 06 Oct 2020 11:43:36 +0000 abelchio 155799 at