DOCSLIB.ORG

The Totem and Atlas/Alfa Experiments a Word from the Director-General

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Totem and Atlas/Alfa Experiments a Word from the Director-General Issue No. 38-39/2016 - Monday 19 September 2016 CERN Bulletin More articles at: http://bulletin.cern.ch DE-SQUEEZE THE BEAMS: THE TOTEM AND ATLAS/ALFA EXPERIMENTS A WORD FROM THE DIRECTOR-GENERAL A special week-long proton–proton run with larger beam sizes at the interaction point is THERE’S MORE TO PARTICLE PHYSICS AT CERN intended to probe the p-p elastic scattering regime at small angles. THAN COLLIDERS CERN’s scientific programme must be compelling, unique, diverse, and integrated into the global landscape of particle physics. One of the Laboratory’s primary goals is to provide a diverse range of excellent physics opportunities and to put its unique facilities to optimum use, maximising the scientific return. (Continued on page 2) In this issue Nicola Turini, deputy spokesperson for TOTEM, in front of one of the experiment’s ‘Roman Pot’ detectors in the LHC tunnel. (Photo: Maximilien Brice/CERN) NEWS Usually, the motto of the LHC is “maximum beams are, and the more parallel the beams are De-squeeze the beams: the luminosity”. But for a few days per year, the LHC when they arrive at the interaction point. For TOTEM and ATLAS/ALFA experiments 1 ignores its motto to run at very low luminosity this special run, the beta-star had to be raised There’s more to particle physics for the forward experiments. This week, the to 2.5 km (whereas in normal runs it is as small at CERN than colliders 1 LHC will provide the TOTEM and ATLAS/ALFA as 0.4 m). News from Council - September 2016 3 experiments with data for a broad physics LHC Report: playing with angles 4 programme. Running with such a high beta-star parameter is LHCb Early Career Scientist Awards 4 an achievement: during Run 1, at 8 TeV, a value The fourth edition of the The TOTEM experiment at Point 5 and the of 1 km was reached. But with a higher energy, ASP took place in Kigali 5 ATLAS/ALFA experiment at Point 1 study the the two incoming protons deviate by smaller How the LHC is inspiring a elastic scattering of protons, which are not angles, for equal transferred momentum. Smart Urban Farm Startup 6 observable in normal operation runs. In the Since the TOTEM and ATLAS/ALFA Roman Pot elastic scattering process, the two protons detectors cannot be moved closer to the beams, Computer Security 7 survive their encounter intact and only change the beta-star parameter must be raised to even Ombud’s Corner 7 directions by exchanging momentum. higher values to provide acceptance for the Johan Blouw (1968 - 2016) 8 smaller angles. “The effort that is required for Siegmund Brandt (1936 – 2016) 8 To allow this special run, the operators play the machine to deliver beams with such a high Werner Kienzle (1936 – 2016) 9 with the so-called beta-star parameter. The value of the beta-star parameter is extremely higher the beta star, the more de-squeezed the challenging,” says Simone Giani, spokesperson Official news 9 (Continued on page 2) Learning 10 Take note 10 Seminars 12 Published by: CERN-1211 Geneva 23, Switzerland Tel. + 41 22 767 35 86 Printed by: CERN Printshop © 2016 CERN - ISSN: Printed version: 2077-950X Electronic version: 2077-9518 A WORD FROM THE DIRECTOR-GENERAL (Continued from page 1) THERE’S MORE TO PARTICLE PHYSICS AT CERN THAN COLLIDERS In this spirit, we have recently established Over 300 people attended the workshop, could be done elsewhere does not allow a Physics Beyond Colliders study group some three quarters coming from outside for the best use of the discipline’s resources with a mandate to explore the unique CERN. The call for proposals resulted in globally. opportunities offered by the CERN around 30 submissions for talks, with about accelerator complex to address some of two third of those being discussed at the I’m looking forward to following the today’s outstanding questions in particle workshop. It was interesting to see a spirit interactions and activities that these physics through projects complementary of collaborative competition, the hallmark working groups will foster over the coming to high-energy colliders and other of our field, building up as the workshop years, and to reading the report that will initiatives in the world. The study group progressed. The proposals addressed be delivered in 2018 to inform the next will provide input to the next update of the questions of fundamental physics using European Strategy update. There’s a bright European Strategy for Particle Physics. approaches complementary to those for future, I’m sure, for physics beyond - and which colliders are best adapted. They alongside - colliders at CERN. The process kicked off with a two-day covered, among others, searches for dark- workshop at CERN on 6 and 7 September, sector particles, measurements of the Fabiola Gianotti organised by the study group conveners: proton electric dipole moment, studies of Joerg Jaeckel (Heidelberg), Mike Lamont ultra-rare decays, searches for axions, and (CERN) and Claude Vallée (CPPM Marseille many more. and DESY). Its purpose was to present experimental and theoretical ideas, and to The next step for the study group is hear proposals for compelling experiments to organise the work to develop and that can be done at the extremely versatile consolidate the ideas that were heard at CERN accelerator complex. From the linacs the workshop and others that can be put to the SPS, CERN accelerators are able to forward in the coming months. Working deliver high intensity beams across a broad groups will examine the physics case and range of energies, particle types and time technical feasibility in the global context: structure. indeed, carrying out research here that (Continued from page 1) DE-SQUEEZE THE BEAMS: THE TOTEM AND ATLAS/ALFA EXPERIMENTS not be physically possible, a detailed study of that region will shed light on what is happening when the two protons almost don’t interact. Secondly, in the same region, the contribution of the electromagnetic interaction (“Coulomb” scattering) interferes with the nuclear part of the elastic interaction. Studying this interference zone can shed light on the internal structure of the protons, and on which part of the protons (either the peripheral or the inner part) is actually responsible for the elastic scattering process. Moreover, it is also possible to get information on the probability that two protons pass through each other without interfering, Part of the ATLAS/ALFA experiment apparatus at Point 1 in the LHC tunnel. (Photo: Ronaldus Suykerbuyk) transparently. “This might appear awkward if you think of a proton as a billiard ball,” notes of the TOTEM Collaboration. “We are very to the “cross-section”) at 13 TeV, TOTEM will Simone Giani. “But the protons should be thankful to the LHC team for having pushed focus on a detailed study of the region of low thought as multi-body quantum systems.” the machine to such extreme settings,” adds transferred momentum of the elastic scattering, Karlheinz Hiller, ALFA project leader. that is, when the two protons barely interact In other words, to use a metaphor, one can and the scattering angles are very small. imagine the two scattering protons as two The TOTEM physics programme foreseen for large “galaxies” (made internally of tiny moving this special high beta-star run features many An in-depth study of this region is important particles) launched at high speed against each interesting measurements. In addition to the for many different reasons. First of all, the other: there is a finite probability that the two precise determination of the total proton– interaction probability seems to diverge for very “galaxies” will pass through each other without proton interaction probability (closely related small transferred momenta, but as this should the inner particles interacting significantly. 2 CERN Bulletin Finally, the TOTEM collaboration plans to gives an independent estimate of the elastic cross-section at 8 TeV. More information conduct physics studies looking for evidence absolute luminosity of the LHC. The luminosity on the TOTEM website. of special states formed by three gluons, which measurements are otherwise normally done via are theoretically predicted but for which the Van der Meer scans, during the standard high- The latest result published by the ATLAS/ALFA experimental evidence is still weak. luminosity runs. Collaboration is the measurement of the total cross section from proton-proton elastic The physics goal of the ATLAS/ALFA experiment “With good statistics – such as 10 million good scattering at 7 and 8 TeV with the beta-star is also to perform a precision measurement of elastic events – we hope to be able to measure parameter at 90 m, whereas the data with the proton–proton total cross section, but the absolute luminosity with a 3% precision,” beta-star at 1 km are still under analysis. More then to use this to determine the absolute LHC says Patrick Fassnacht, deputy project leader of information on the ATLAS/ALFA website. luminosity at Point 1 for the 2.5 km run. the ATLAS/ALFA project. Stefania Pandolfi For ATLAS/ALFA, the interesting part of the spectrum is at low values of transferred momentum, where Coulomb scattering is The latest results published by the TOTEM dominant: since the Coulomb scattering cross- Collaboration include a first observation of section is theoretically known, its measurement deviations from a pure exponential form of the NEWS FROM COUNCIL - SEPTEMBER 2016 I would like to inform you of the main news from the Council this week. First of all, the Council with Council delegates during their first day congratulated CERN and the Collaborations on the superb performance of the accelerator at the beam line.
Load more

Recommended publications
  • Detection of Cosmic Rays at the LHC Detection of Cosmic Rays at the LHC
    Particle and Astroparticle Physics at the Large Hadron Collider --Hadronic Interactions-- Albert De Roeck CERN, Geneva, Switzerland Antwerp University Belgium UC-Davis California USA NTU, Singapore November 15th 2019 Outline • Introduction on the LHC and LHC physics program • LHC results for Astroparticle physics • Measurements of event characteristics at 13 TeV • Forward measurements • Cosmic ray measurements • LHC and light ions? • Summary The LHC Machine and Experiments MoEDAL LHCf FASER totem CM energy → Run-1: (2010-2012) 7/8 TeV Run-2: (2015-2018) 13 TeV -> Now 8 experiments Run-2 starts proton-proton Run-2 finished 24/10/18 6:00am 2018 2010-2012: Run-1 at 7/8 TeV CM energy Collected ~ 27 fb-1 2015-2018: Run-2 at 13 TeV CM Energy Collected ~ 140 fb-1 2021-2023/24 : Run-3 Expect ⇨ 14 TeV CM Energy and ~ 200/300 fb-1 The LHC is also a Heavy Ion Collider ALICE Data taking during the HI run • All experiments take AA or pA data (except TOTEM) Expected for Run-3: in addition short pO and OO runs ⇨ pO certainly of interest for Cosmic Ray Physics Community! 4 10 years of LHC Operation • LHC: 7 TeV in March 2010 ->The highest energy in the lab! • LHC @ 13 TeV from 2015 onwards March 30 2010 …waiting.. • Most important highlight so far: …since 4:00 am The discovery of a Higgs boson • Many results on Standard Model process measurements, QCD and particle production, top-physics, b-physics, heavy ion physics, searches, Higgs physics • Waiting for the next discovery… -> Searches beyond the Standard Model 12:58 7 TeV collisions!!! New Physics Hunters
    [Show full text]
  • Laboratori Nazionali Di Frascati
    International Committee for Future Accelerators Sponsored by the Particles and Fields Commission of IUPAP Beam Dynamics Newsletter No. 51 Issue Editor: S. Chattopadhyay Editor in Chief: W. Chou April 2010 3 Contents 1 FOREWORD ........................................................................................................ 11 1.1 FROM THE CHAIRMAN ............................................................................................. 11 1.2 FROM THE EDITOR .................................................................................................. 12 2 INTERNATIONAL LINEAR COLLIDER (ILC) ............................................ 14 2.1 FIFTH INTERNATIONAL ACCELERATOR SCHOOL FOR LINEAR COLLIDERS ............... 14 3 THEME SECTION: ACCELERATOR SCIENCE AND TECHNOLOGY IN THE UK ................................................................................................................ 20 3.1 OVERVIEW – AN EMERGING PARADIGM OF COLLABORATION BETWEEN UNIVERSITIES, NATIONAL FACILITIES AND INDUSTRY ............................................ 20 3.1.1 Introduction .................................................................................................. 20 3.1.2 Mission of UK Accelerator Science and Technology .................................. 20 3.1.3 The Model: Integrated Accelerator Community and Stakeholders .............. 21 3.1.4 The Research Program Driven by Science ................................................... 21 3.1.4.1 Research Focus: Current ..............................................................
    [Show full text]
  • Upgrade of the Global Muon Trigger for the Compact Muon Solenoid Experiment at CERN”
    DISSERTATION/DOCTORAL THESIS Titel der Dissertation/Title of the Doctoral Thesis “Upgrade of the Global Muon Trigger for the Compact Muon Solenoid experiment at CERN” verfasst von/submitted by Mag. Dinyar Sebastian Rabady angestrebter akademischer Grad/in partial fulfilment of the requirements for the degree of Doktor der Naturwissenschaften (Dr. rer. nat.) Wien, im Jänner 2018/Vienna, in January 2018 Studienkennzahl lt. Studienblatt/ A 796 605 411 degree programme code as it appears on the student record sheet: Studienrichtung lt. Studienblatt/ Physik field of study as it appears onthe student record sheet: Betreut von/Supervisor: Dipl.-Ing. Dr. Claudia-Elisabeth Wulz Hon.-Prof. Dipl.-Phys. Dr. Eberhard Widmann Für meinen Großvater. Abstract The Large Hadron Collider is a large particle accelerator at the CERN research labo- ratory, designed to provide particle physics experiments with collisions at unprece- dented centre-of-mass energies. For its second running period both the number of colliding particles and their collision energy were increased. To cope with these more challenging conditions and maintain the excellent performance seen during the first running period, the Level-1 trigger of the Compact Muon Solenoid experiment — a so- phisticated electronics system designed to filter events in real-time — was upgraded. This upgrade consisted of the complete replacement of the trigger electronics andafull redesign of the system’s architecture. While the calorimeter trigger path now follows a time-multiplexed processing model where the entire trigger data for a collision are received by a single processing board, the muon trigger path was split into regional track finding systems where each newly introduced track finder receives data from all three muon subdetectors for a certain geometric detector slice and reconstructs fully formed muon tracks from this.
    [Show full text]
  • The Very Forward CASTOR Calorimeter of the CMS Experiment
    EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN) CERN-EP-2020-180 2021/02/11 CMS-PRF-18-002 The very forward CASTOR calorimeter of the CMS experiment The CMS Collaboration* Abstract The physics motivation, detector design, triggers, calibration, alignment, simulation, and overall performance of the very forward CASTOR calorimeter of the CMS exper- iment are reviewed. The CASTOR Cherenkov sampling calorimeter is located very close to the LHC beam line, at a radial distance of about 1 cm from the beam pipe, and at 14.4 m from the CMS interaction point, covering the pseudorapidity range of −6.6 < h < −5.2. It was designed to withstand high ambient radiation and strong magnetic fields. The performance of the detector in measurements of forward energy density, jets, and processes characterized by rapidity gaps, is reviewed using data collected in proton and nuclear collisions at the LHC. ”Published in the Journal of Instrumentation as doi:10.1088/1748-0221/16/02/P02010.” arXiv:2011.01185v2 [physics.ins-det] 10 Feb 2021 © 2021 CERN for the benefit of the CMS Collaboration. CC-BY-4.0 license *See Appendix A for the list of collaboration members Contents 1 Contents 1 Introduction . .1 2 Physics motivation . .3 2.1 Forward physics in proton-proton collisions . .3 2.2 Ultrahigh-energy cosmic ray air showers . .5 2.3 Proton-nucleus and nucleus-nucleus collisions . .5 3 Detector design . .6 4 Triggers and operation . .9 5 Event reconstruction and calibration . 12 5.1 Noise and baseline . 13 5.2 Gain correction factors . 15 5.3 Channel-by-channel intercalibration .
    [Show full text]
  • Upgrade of the Global Muon Trigger for the Compact Muon Solenoid Experiment at CERN
    DISSERTATION/DOCTORAL THESIS Titel der Dissertation/Title of the Doctoral Thesis “Upgrade of the Global Muon Trigger for the Compact Muon Solenoid experiment at CERN” verfasst von/submitted by Mag. Dinyar Sebastian Rabady angestrebter akademischer Grad/in partial fulfilment of the requirements for the degree of Doktor der Naturwissenschaften (Dr. rer. nat.) CERN-THESIS-2018-033 25/04/2018 Wien, im Jänner 2018/Vienna, in January 2018 Studienkennzahl lt. Studienblatt/ A 796 605 411 degree programme code as it appears on the student record sheet: Studienrichtung lt. Studienblatt/ Physik field of study as it appears onthe student record sheet: Betreut von/Supervisor: Dipl.-Ing. Dr. Claudia-Elisabeth Wulz Hon.-Prof. Dipl.-Phys. Dr. Eberhard Widmann Für meinen Großvater. Abstract The Large Hadron Collider is a large particle accelerator at the CERN research labo- ratory, designed to provide particle physics experiments with collisions at unprece- dented centre-of-mass energies. For its second running period both the number of colliding particles and their collision energy were increased. To cope with these more challenging conditions and maintain the excellent performance seen during the first running period, the Level-1 trigger of the Compact Muon Solenoid experiment — a so- phisticated electronics system designed to filter events in real-time — was upgraded. This upgrade consisted of the complete replacement of the trigger electronics andafull redesign of the system’s architecture. While the calorimeter trigger path now follows a time-multiplexed processing model where the entire trigger data for a collision are received by a single processing board, the muon trigger path was split into regional track finding systems where each newly introduced track finder receives data from all three muon subdetectors for a certain geometric detector slice and reconstructs fully formed muon tracks from this.
    [Show full text]
  • Across the Ocean, Yet Close to Home by Katie Yurkewicz
    Across the ocean, yet close to home By Katie Yurkewicz Among the 10,000 people from around the world who are working on the Large Hadron Collider, 1000 hail from universities and national labs in the United States. The Large Hadron Collider is the world’s next-generation and students from almost 60 nations. More than 1000 of particle accelerator. Arguably the most ambitious scien- these hail from 93 universities and national laboratories tific endeavor ever undertaken, the $8.7 billion project at in the United States. Researchers from US institutions have CERN, the European particle physics lab in Geneva, made vital contributions to all aspects of LHC construction, Switzerland, has been in the works for more than two and are now looking forward to the next phase, when they decades. When it begins operating in mid-2008, scien- will see collisions begin, watch data start flowing, and spend tists predict that its very-high-energy collisions will yield many a sleepless night searching for the tracks of particles extraordinary discoveries about the nature of the whose existence would transform our understanding of the physical universe. universe. The LHC project has two equally important aspects: the collider itself and its six particle detectors, each one a Putting the C in LHC self-contained experiment. The collider, nearing completion The heart of the LHC project is the collider itself, and the in a 27-kilometer ring deep below the Swiss-French border, heart of the collider is a series of thousands of super- will accelerate two beams of protons in opposite directions conducting magnets.
    [Show full text]
  • Study of Diffraction with the ATLAS Detector at The
    Th`esede doctorat de l’Universit´eParis 11 et de l’Institut de Physique Nucléaire de l’Académie Polonaise des Sciences sp´ecialit´e Champs, Particules, Mati`ere pr´esent´eepar Rafa lSTASZEWSKI pour obtenir les grades de docteur de l’Universit´eParis 11 et de l’Institut de Physique Nucléaire de l’Académie Polonaise des Sciences Study of Diffraction with the ATLAS detector at the LHC Th`esesoutenu le 24 Septembre 2012 devant le jury compos´ede: Etienne AUGE(´ pr´esident) Marco BRUSCHI (rapporteur) Janusz CHWASTOWSKI (directeur de th`ese) Alan MARTIN (rapporteur) Christophe ROYON (directeur de th`ese) Robi PESCHANSKI Antoni SZCZUREK Th`esepr´epar´ee au Service de Physique des Particules du CEA de Saclay et `al’Institut de Physique Nucléaire de l’Académie Polonaise des Sciences de Cracovie The thesis is devoted to the study of diffractive physics with the ATLAS de- tector at the LHC. After a short introduction to diffractive physics including soft and hard diffraction, we discuss diffractive exclusive production at the LHC which is particularly interesting for Higgs and jet production. The QCD mechanism de- scribed by the Khoze Martin Ryskin and the CHIDe models are elucidated in detail. The uncertainties on these models are still large and a new possible exclusive jet measurement at the LHC will allow to reduce the uncertainty on diffarctive Higgs boson production to a factor 2 to 3. An additional measurement of exclusive pion production pp → pπ+π−p allows to constrain further exclusive model relying on the use of the ALFA stations, which are used in the ATLAS Experiment for detection of protons scattered in elastic and diffractive interactions.
    [Show full text]
  • The ATLAS Experiment, the World's Largest-Volume Particle Physics
    The ATLAS experiment, the world’s largest-volume particle physics detector. 14 | CERN “For the physics community, the LHC is a discovery machine, in that finding just the Higgs boson anticipated by the Standard Model would be almost a disappointment.” Sergio Bertolucci in the CERN Bulletin. Physics and Experiments ALICE, probing the quark–gluon plasma continued during 2008 for detectors added later to the design ALICE is a heavy-ion experiment designed to study the physics (TRD, PHOS, and EMCAL). Thus, detector integration and of strongly interacting matter and the quark–gluon plasma in commissioning were the main activities in 2008. lead–lead collisions at the LHC. The ALICE Collaboration currently includes more than 1000 physicists and senior Several runs with cosmic rays were performed at the beginning engineers — from both nuclear and high-energy physics — of the year, and from May until mid-October ALICE was from about 100 institutions in some 30 countries. Some new operated continuously (24/7). As far as could be verified, the institutes from the US and South Korea joined ALICE in 2008, performance of all subsystems is very close to (or better than) while the associate members IPE Karlsruhe (Germany) and specification. BARC (Mumbai, India) left after completing their respective technical contributions to the experiment. During LHC commissioning in September, only a subset of detectors was switched on because the particle flux was ALICE consists of a central part, which measures hadrons, occasionally very high during beam tuning. Nevertheless, electrons, and photons, and a forward spectrometer to measure timing of most trigger detectors was verified and adjusted with muons.
    [Show full text]
  • Measurement of the W → Eν Cross Section with Early Data from the CMS Experiment at CERN
    Imperial College London Blackett Laboratory High Energy Physics Measurement of the W eν cross section ! with early data from the CMS experiment at CERN Nikolaos Rompotis A thesis submitted to Imperial College London for the degree of Doctor of Philosophy and the Diploma of Imperial College. January 2011 Abstract The Compact Muon Solenoid (CMS) is a general purpose detector designed to study proton-proton collisions, and heavy ion collisions, delivered by the Large Hadron Col- lider (LHC) at the European Laboratory for High Energy Physics (CERN). This thesis describes a measurement of the inclusive W eν cross section at 7 TeV centre of mass ! energy with 2:88 0:32 pb−1 of LHC collision data recorded by CMS between March ± and September 2010. W boson decays are identified by the presence of a high-pT electron that satisfies selec- tion criteria in order to reject electron candidates due to background processes. Electron selection variables are studied with collision data and found to be in agreement with expectations from simulation. A fast iterative technique is developed to tune electron selections based on these variables. Electron efficiency is determined from simulation and it is corrected from data using an electron sample from Z decays. The number of W candidates is corrected for remaining background events using a fit to the missing transverse energy distribution. The measured value for the inclusive W production cross section times the branching ratio of the W decay in the electron channel is: σ(pp W +X) BR(W eν) = 10:04 0:10(stat) 0:52(syst) 1:10(luminosity) nb; ! × ! ± ± ± which is in excellent agreement with theoretical expectations.
    [Show full text]
  • The CMS Trigger System
    EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN) CERN-EP/2016-160 2017/01/26 CMS-TRG-12-001 The CMS trigger system The CMS Collaboration∗ Abstract This paper describes the CMS trigger system and its performance during Run 1 of the LHC. The trigger system consists of two levels designed to select events of potential physics interest from a GHz (MHz) interaction rate of proton-proton (heavy ion) col- lisions. The first level of the trigger is implemented in hardware, and selects events containing detector signals consistent with an electron, photon, muon, t lepton, jet, or missing transverse energy. A programmable menu of up to 128 object-based algo- rithms is used to select events for subsequent processing. The trigger thresholds are adjusted to the LHC instantaneous luminosity during data taking in order to restrict the output rate to 100 kHz, the upper limit imposed by the CMS readout electronics. The second level, implemented in software, further refines the purity of the output stream, selecting an average rate of 400 Hz for offline event storage. The objectives, strategy and performance of the trigger system during the LHC Run 1 are described. Published in the Journal of Instrumentation as doi:10.1088/1748-0221/12/01/P01020. arXiv:1609.02366v2 [physics.ins-det] 25 Jan 2017 c 2017 CERN for the benefit of the CMS Collaboration. CC-BY-3.0 license ∗See Appendix A for the list of collaboration members Contents 1 Contents 1 Introduction . .2 1.1 The CMS detector . .4 2 The trigger system . .4 2.1 The L1 trigger overview .
    [Show full text]
  • What Can We Learn / Expect from the LHC Experiments?
    Discussion Session EDS’09 – What can we learn / expect from the LHC Experiments? Chaired by Karsten Eggert6 Panel members: Albert de Roeck1, Konstantin Goulianos4, Per Grafstr¨om1, Hannes Jung3, Hubert Niewiadomski2, Karel Safarik1, Mark Strikman2, Chung-I Tan5 1CERN, 1211 Geneve 23, Switzerland 2Penn State University, Dept. of Physics, University Park, PA, USA 3DESY, Hamburg, Physics Department, University Antwerp 4The Rockefeller University, 1230 York Avenue, New York, NY 10065-9965, USA 5Brown University, Providence, RI, USA 6Case Western Reserve University, Dept. of Physics, Cleveland, OH, USA 1 Introduction Author: Karsten Eggert The panel discussion between experimentalists (most of the LHC experiments were represented) and theorists focussed on the following subjects: What are the most important topics on forward and diffractive physics to be addressed at the start of the LHC? How much can we learn from the experience gained during the forward detector operation at FNAL (K. Goulianos) and HERA (H. Jung) and from their latest physics results? What kind of collaborations between the LHC experiments can be envisaged to maximise synergy effects, including common trigger and run strategies, beam analysis, Monte Carlos and combination of data? The LHC experiments benefit from their large acceptance overlaps of the very forward detectors up to the Roman Pot detectors several hundred meters upstream. As an example, the multiplicity distribu- tions for different pseudorapidity intervals have to be corrected with the individual experimental and trigger acceptances to be able to obtain cross-sections for diffractive processes (K. Safarik). The different systematics of the experiments will help disentangle the various cross-sections. 3 The measurement of the elastic scattering cross-section over a large transverse momentum range t (10− < t < 10 GeV2) is also quite challenging, and benefits from different systematics of the two set-ups (ATLAS and TOTEM) and the way the collaborations will extract the total cross-section (Per Grafstr¨om).
    [Show full text]
  • Proton-Proton Collisions at the Large Hadron Collider's ALICE Experiment: Diffraction and High Multiplicity
    Proton-proton Collisions at the Large Hadron Collider's ALICE Experiment: Diffraction and High Multiplicity Zoe Louise Matthews Thesis submitted for the degree of Doctor of Philosophy Particle Physics Group, School of Physics and Astronomy, University of Birmingham. November 20, 2011 Abstract Diffraction in pp collisions contributes approximately 30 % of the inelastic cross section. Its influ- ence on the pseudorapidity density is not well constrained at high energy. A method to estimate the contributing fractions of diffractive events to the inelastic cross section has been developed, and the fractions are measured in the ALICE detector at 900 GeV (7 TeV) to be fD=0.278±0.055 (fD=0.28±0.054) respectively. These results are compatible with recent ATLAS and ALICE mea- surements. Bjorken's energy density relation suggests that, in high multiplicity pp collisions at the LHC, an environment comparable to A-A collisions at RHIC could be produced. Such events are of great interest to the ALICE Collaboration. Constraints on the running conditions have been established for obtaining a high multiplicity pp data sample using the ALICE detector's multi- plicity trigger. A model independent method to separate a multiplicity distribution from `pile-up' contributions has been developed, and used in connection with other findings to establish a suitable threshold for a multiplicity trigger. It has been demonstrated data obtained under these conditions for 3 months can be used to conduct early strangeness analyses with multiplicities of over 5 times the mean. These findings have resulted in over 16 million high multiplicity events being obtained to date.
    [Show full text]