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CMS Experiment at the LHC, CERN
Scientific discussion meeting organised by Professor John Ellis CBE FRS, Professor David Charlton and Professor Tejinder Virdee FRS
A new particle resembling the long-sought Higgs boson has been discovered at CERN. This meeting will discuss the genesis of this discovery, its interpretation, its significance, its relations to condensed-matter physics and cosmology, and possible future experiments to explore its nature.
Biographies of the organisers and speakers will be made available shortly, and you can download the draft two-day programme.
Recorded audio of the presentations will be available on this page after the event and the papers will be published in a future issue of Philosophical Transactions A.
This meeting is immediately followed by a related satellite meeting at the Royal Society at Chicheley Hall, home of the Kavli Royal Society International Centre.
This event is intended for researchers in relevant fields and is free to attend. There are a limited number of places and registration is essential. An optional lunch is offered and should be booked during registration (all major credit cards accepted).
Enquiries: Contact the events team
Professor Tom Kibble CBE FRS, Imperial College London, UKSpontaneous symmetry breaking in gauge theories
Tom Kibble was born in 1932 in Madras, India (now Chennai), and educated there and in Edinburgh, where he obtained his PhD in Mathematical Physics in 1958. He joined the theoretical physics group at Imperial College led by Professor Abdus Salam in 1959, becoming a lecturer in 1961, professor in 1970 and Head of Department from 1983 to 1991. His work has been mainly on quantum field theory and cosmology, especially problems of spontaneous symmetry breaking and the formation of topological defects such as cosmic strings in the early universe or analogues in laboratory systems. He was elected to Fellowship of the Royal Society in 1980, received the Royal Society's Hughes medal (jointly with Peter Higgs) in 1981, and the Royal Medal in 2012. He was appointed CBE in 1998. He was chair of Scientists Against Nuclear Arms from 1985 to 1991. He was married to Anne Allan from 1957 until her death in 2005 and has three children and seven grandchildren. His principal recreation is walking.
The aim of this historical talk is to describe the development of the idea of spontaneous symmetry breaking in gauge theories as I saw it from my perspective in Abdus Salam’s group at Imperial College. I will give an account of particle physics in the years after the second world war, describe early attempts at constructing a unified theory of weak and electromagnetic interactions, the obstacles encountered and how they were eventually overcome with the mass-generating mechanism incorporating the idea of spontaneous symmetry breaking, one of whose features is the now-famous Higgs boson.
Professor Günther Dissertori, ETH Zurich, SwitzerlandThe pre-LHC Higgs hunt
Prof. G. Dissertori has studied Physics at the University of Innsbruck, Austria. In 1997 he obtained his PhD in Physics, for a thesis on theoretical studies and experimental data analyses related to the ALEPH experiment at CERN’s electron-positron collider LEP. From 1997 to 2001 he worked at CERN, first as Research Fellow and then as Research Staff scientist. During that time he continued his work on the ALEPH experiment and started his involvement with the CMS detector at the Large Hadron Collider. In September 2001 he became Assistant Professor at ETH Zurich. Since 2007 he is Full Professor and currently he is the Head of the Institute for Particle Physics. The main focus of his research group is on the operation and physics exploitation of the CMS experiment. Besides his research activities, G. Dissertori pays particular attention to his teaching at ETH, which has already been awarded several times.
Already before the start of the LHC, the search for the Higgs boson has been very intense. In this presentation I will summarize the main efforts, carried out over many years at the LEP and Tevatron colliders. The experiments at those colliders were able to constrain the possible mass range for the Higgs boson, either via direct searches, or indirectly via precision measurements and their sensitivity to quantum corrections.
Professor Luis Alvarez-Gaume, CERN, SwitzerlandFrom condensed matter to the Standard Model of particle physics
Sir Chris Llewellyn-Smith FRS, University of Oxford, UKGenesis of the LHC
Chris Llewellyn Smith is Director of Energy Research, Oxford University, and President of the Council of SESAME (Synchrotron-light for Experimental Science and Applications in the Middle East). He has chaired the Council of ITER, the global fusion energy project, directed the UK's fusion programme, and served as Provost and President of University College London, Director General of CERN (1994-1998, when the Large Hadron Collider was approved and construction started), and Chairman of Oxford Physics. His theoretical contributions to the ‘standard model’ of particle physics were recognised by his election to the Royal Society in 1984. He has written and spoken widely on science funding, international scientific collaboration and energy issues, and served on many advisory bodies nationally and internationally, including the UK Prime Minister’s Advisory Council on Science and Technology (1989-92). His scientific contributions and leadership have been recognised by awards and honours in seven countries on three continents.
I will describe the scientific, technical and political genesis of the LHC. First, I will outline the history of the LHC, from first thoughts and the development of the accelerator experience that underwrote the LHC, through detailed studies of the physics potential and the LHC itself and the evolution of the experimental programme, to the presentation of the proposal to the CERN Council in December 1993. I will then discuss the events leading to the approval of construction in two stages (in December 1994) and later in a single stage (in December 1996), and the negotiations that brought non-Member States into the construction of the LHC in the intervening period. After discussing the initial stages of construction, up to the point of no return, I will conclude by identifying points of potential relevance for the approval of possible future large projects.
Professor Paul Collier, CERN, SwitzerlandThe technical challenges of the LHC
Paul Collier studied physics at Leeds University, UK and obtained his Ph.D. in the Philosophy of Applied Physics in 1985. He is a Fellow of the Institute of Physics and a Chartered Engineer. Having worked as a lecturer on Applied Physics and Electrical Engineering at Sheffield University for two years, he was hired at CERN in 1987 to work on the radio-frequency control system of the LEP (Large Electron Positron collider). His zeal for the design, operation and performance of the LEP accelerator piloted him to the role of Machine Coordinator for the SPS-Accelerator complex. In 1997 he was entrusted the Project of the SPS upgrade of the LHC injector, to oversee the design and installation of new and upgraded material required for the LHC beams. This Project successfully completed, P. Collier was assigned the responsibility of running the Accelerator and Beams Operations Group, thus supervising the operation with beams for the whole CERN complex. Two years later, in 2009, was he nominated Head of the Beams Department, responsible for the beam generation, acceleration, diagnostics and controls of the CERN accelerator complex. With his internationally recognized expertise as an applied physicist he has participated in many international advisory panels and reviews and within the Tripartite Forum on Employment Conditions with CERN Member States.
The LHC is a 27km circumference hadron collider, built at CERN to explore the energy frontier of particle physics. Approved in 1994, it was commissioned and began operation for data taking in 2010. The design and construction of the LHC presented many design, engineering and logistical challenges which involved pushing a number of technologies well beyond their level at the time. Since the start-up of the machine, then there has been a very successful 3-year run with an impressive amount of data delivered to the LHC experiments. With an increasingly large stored energy in the beam the operation of the machine itself presented many challenges and some of these will be discussed. Finally, the planning for the next 20 years has been outlined with progressive upgrades of the machine, first to nominal energy, then to progressively higher collision rates. The upgrades of the machine themselves represent a whole new set of design, engineering and operational challenges. Some of the key areas for the upgrades will be explained in detail.
Professor Austin Ball, CERN, SwitzerlandTechnical challenges of the LHC experiments
Austin Ball is a staff physicist at CERN, the European Organisation for Nuclear Research. At the University of Manchester (UK), he received a Ph.D. in High Energy Physics in 1980 and thereafter studied electron-positron collisions with the JADE experiment at the PETRA collider in DESY, Hamburg, Germany, focusing on the installation, optimisation and exploitation for physics of the muon detection system. Moving to University of Maryland (US), he eventually led the technical team which delivered a large part of the Hadron Calorimeter (HCAL) for the OPAL experiment at the LEP electron positron-collider at CERN. After periods as HCAL technical coordinator, B-physics analysis convenor and Run Coordinator for that experiment, interspersed (until its cancellation) with R & D, at various labs in the US, for the SDC experiment at the Superconducting Supercollider (US), he joined CERN in 1998 as Deputy Technical Coordinator of the CMS experiment, just as construction started. As Technical Coordinator since 2006, he has been responsible for the surface commissioning, underground installation, technical operation and first major upgrade of the CMS experiment.
This presentation will introduce the design of the general purpose experiments ATLAS and CMS, which jointly discovered the Higgs boson, showing how generic features are motivated by the characteristics needed to explore the physics landscape made accessible by the LHC accelerator, whose high collision rate creates a very challenging operating environment for instrumentation. Some examples of the very different component designs chosen by the two experiment collaborations will then be highlighted, as an introduction to briefly describing the techniques used in the construction of these elements and subsequently in the assembly of both detection systems in their respective underground caverns.
Professor Fabiola Gianotti, CERN, SwitzerlandThe Higgs discovery and measurements with ATLAS
Fabiola Gianotti, PhD, is a research physicist at CERN and HonouraryProfessor at the University of Edinburgh. From March 2009 to February 2013 she has been the co-ordinator ("Spokesperson") of the ATLAS experiment at the Large Hadron Collider. On 4 July 2012 she presented the ATLAS results in a seminar at CERN, where the discovery of the Higgs boson was announced by the ATLAS and CMS experiments. She is a member of the Italian Academy of Sciences. She has been awarded the honour of "Grande Ufficiale" by the Italian President Giorgio Napolitano, the Enrico Fermi prize of the Italian Physical Society and the Fundamental Physics Prize of theMilner Foundation. She received Honourary Doctoral Degrees from the University of Uppsala and from the Ecole Polytechnique Federale de Lausanne. She is a member of the Scientific Advisory Board to the UN Secretary-GeneralMr Ban Ki-moon.
On 4 July 2012, the ATLAS and CMS experiments operating at the CERN Large Hadron Collider (LHC) announced the discovery of a new particle compatible with the Higgs boson (sought for almost50 years), which is crucial for our understanding of fundamental physics and thus the structure and evolution of the universe.This talk describes the unprecedented instruments and challenges that have allowed such an accomplishment, the results from the full recorded dataset, the physics and the relevance of this discovery, and the prospects from future detailed studies of this Higgs boson.
Professor Tejinder Virdee FRS, Imperial College London, UKThe Higgs discovery and measurements with CMS
Tejinder (Jim) Virdee is Professor of Physics at Imperial College, London. After the UA1 experiment (1990), where W and Z bosons were discovered, Virdee has concentrated on the physics and experimentation at CERN’s Large Hadron Collider. He is one of the founding members of the Compact Muon Solenoid Collaboration (CMS) at the LHC. Virdee has played a major role in all phases of the experiment, from conception and design, through construction to the extraction of science that have already lasted around 25 years. He poineered some of the techniques used in its calorimeters crucial for the discovery of a Higgs boson announced by the CMS experiment in July 2012, along with the sister experiment ATLAS. Virdee was the Spokesperson of the CMS Collaboration for three years, from 2007, that included the start of collision data taking, and was its Deputy Spokesperson from 1993 to 2006. Virdee’s current work involves studies of the newly found Higgs boson and the definition of the upgraded CMS detector for very high luminosity LHC running. Amongst the prizes he has won is the 2013 European Physical Society-HEPP prize co-awarded for his “pioneering and outstanding leadership role in the making of the CMS experiment”.
On July 4th 2012 the CMS Collaboration announced the discovery of a Higgs boson, along with the ATLAS Collaboration. This talk will give brief details of the design and construction of CMS experiment. The boson’s discovery and recent results from the many CMS measurements of the properties of the boson using the full dataset from Run I of LHC will be presented. These will be compared with the predictions of the standard model of particle physics. The outlook will also be presented for making further measurements using much more data to be collected when the LHC restarts operation in 2015.
Professor Ben Allanach, University of Cambridge, UKMultiple solutions in supersymmetry and the Higgs
Ben Allanach is a Professor of theoretical physics at the University of Cambridge and Principal Investigator for theoretical high energy physics there. He primarily works on interpreting the Large Hadron Collider data, asking what they mean for various theories such as supersymmetry, extra dimensions and models of dark matter. His computer program SOFTSUSY, which calculates the masses and other properties of supersymmetric particles, is used by both general purpose LHC experiments to interpret their searches. He was one of the founding architects of the "SUSY Les Houches accord", which allows the integrated use of such information to be universally communicated between the many different computer programs that calculate various different physical observables. He has been working with experiments to suggest the best ways of presenting complex experimental information. He was scientific secretary for the CERN Council Strategy Group in 2005-2006, and was awarded a Gambrinus Fellowship at Dortmund University of Technology in 2008.
Searches for supersymmetric particles can be difficult to interpret. Here, we shall discuss the fact that, even given a well defined model of supersymmetry breaking with few parameters, there can be multiple solutions. These multiple solutions are physically different, and could potentially mean that points in parameter space have been ruled out by interpretations of LHC data when they shouldn't have been. We shall explain what such multiple solutions are, what they mean and why they haven't been discovered before. We shall illustrate their existence in the Constrained Minimal Supersymmetric Standard Model, although we expect them to be present in other scenarios too.
Professor Paris Sphicas, Athens/CERN, GreeceSearches for the supersymmetry
PhD from MIT on UA1 (jet physics). Scientific associate at CERN (UA1, heavy flavors), then Wilson fellow at Fermilab (CDF). Assistant professor at MIT, 1990, always on CDF, working on top and B physics -- then associate then full prof (MIT). Joined CMS experiment at LHC in 94, working on trigger/DAQ. At CERN since 1997, prof of physics at Univ of Athens since 2002. In CMS: till 2004 Data Acquisition System and High Level Trigger; 2005-06 head of Computing. Software and Physics, 2007-2009 physics coordinator, 2012-2013 chair of CMS Publications Committee. From Jan 2014 deputy spokesperson. Working on SUSY searches.
With the discovery of a Higgs boson at the LHC, the Standard Model (SM) of elementary particles and their interactions is now on rock-solid ground, providing an unfailing and remarkably accurate description of experiments with and without high-energy accelerators. With the physics of the very small thought to be understood at energy scales of at least 100 GeV, the situation is reminiscent of previous times in history when our knowledge of nature was deemed to be “complete”. There are hints that this may once more not be so: from astrophysical observations to theoretical calculations of the Higgs sector, there are several indications that some physics “beyond the SM” should exist. To this day, Supersymmetry (SUSY) remains one of the most popular extensions to the SM. A very significant effort has already been invested in searching for signs of the mirror world of particles hypothesized by SUSY, while the LHC experiments are currently carefully combing through their data samples looking for places where SUSY might be hiding. The talk will present a broad-brush picture of “the why, the what and the how” this search is carried out, along with the reasons for which the expectations are still so very high.
Professor Christophe Grojean, ICREA/IFAE, Barcelona, SpainBeyond the standard Higgs
Christophe Grojean started his research work in theoretical high energy physics at CEA Saclay and got his PhD from Orsay University in 1999. He then spent two years as a postdoctoral fellow at UC Berkeley before being hired on a permanent research position at Saclay. In 2004, he was a visiting professor at the University of Michigan in Ann Arbor. In 2006, he joined the theory unit at CERN first as a fellow and then as junior staff scientist. In the fall of 2012, he joined the Institut de Física d’Altes Energies at UAB as an ICREA Research Professor. He has worked on various topics in particle physics beyond the Standard Model and a few years ago he specialized himself in the physics and the dynamics of the Higgs boson and its possible various incarnations.
An elementary, weakly coupled and solitary Higgs boson allows to extend the validity of the Standard Model up to very high energy, maybe as high as the Planck scale. Nonetheless, this scenario fails to fill the universe with Dark Matter and do not explain the matter-antimatter asymmetry. However, amending the Standard Model tends to destabilize the weak scale by large quantum corrections to the Higgs potential. New degrees of freedom, new forces, new organizing principles are requested to provide a consistent and natural description of physics beyond the standard Higgs.
Professor David Charlton, University of Birmingham, UKSearches beyond supersymmetry
Dave Charlton has been the Spokesperson of the ATLAS Collaboration since March 2013. Before that he was Deputy Spokesperson for four years, and previously Physics Coordinator in 2008-9. He has been Professor of Particle Physics at the University of Birmingham since 2005. During ATLAS construction, he worked on two different pieces of the detector: hybrid readout circuits for the silicon strip sensors of the Semiconductor Tracker (SCT) detector; and on the first-level calorimeter trigger system, responsible for selecting one-in-ten-thousand interesting events within a few microseconds of the proton-proton interactions taking place in ATLAS. From 1989 to 2001, he worked on the OPAL experiment at the LEP electron-positron collider at CERN, on data analysis, components of the trigger and data acquisition systems, muon identification, and more. He was OPAL's Physics Coordinator in 1996-7. He was a Royal Society University Research Fellow from 1994 to 2002. Before 1989 he was a PhD student on the UA1 experiment, searching for – and failing to find – the top quark, which was too massive to be detected there.
The questions raised by the discovery of the light Higgs boson suggest new physics, and new particles, may be near to hand, at the energies now – and soon – being probed at the LHC. An extensive programme of searches for new particles is in place, exploring many possibilities. In the absence of definite predictions, the searches look at many and varied event types, hunting in numerous ways for deviations in the data from the background expectations from known processes.
Professor Mikhail Shaposhnikov, EPFL, SwitzerlandHiggs and cosmology
Mikhail Shaposhnikov studied at Moscow State University and got his PhD from the Institute for Nuclear Research of Russian Academy of Sciences (INR RAS) in 1982. From 1982 till 1991 he was a research scientist at INR RAS. During 1991-1998 he was a staff member at CERN, Geneva. In 1998 he moved to the University of Lausanne. Since 2003 he is a Professor at Ecole Polytechnique Federale de Lausanne, leading the Laboratory for Particle Physics and Cosmology. He worked on the problem of baryon asymmetry of the universe, on phase transitions in gauge theories at high temperatures and their cosmological applications, on alternatives to compactification, on dark matter and cosmological constant, and on cosmological inflation.
I will discuss how the Higgs field of the Standard Model can make the Universe flat, homogeneous and isotropic; produce the quantum fluctuations seeding the structure formation; lead to the Hot Big Bang; and play the crucial role in baryogenesis and dark matter production.
Dr Oliver Buchmueller, Imperial College London, UKThe upgraded ATLAS and CMS detectors and their physics capabilities I & II
Dr Buchmueller is an academic faculty member at Imperial College. He is an expert on searches for new physics at colliders with a special emphasis on the subjects of Supersymmetry, Dark matter, and Higgs. He joined the CMS collaboration in 2003 and has spearheaded several activities and data analyses in CMS. Since 2012 he is co-chairing the Trigger Performance and Strategy Working Group in CMS. Driven by the needs of an evolving physics program and increasing LHC luminosity this group is charged to define the trigger characteristics, specifications, and upgrades for CMS operation at the high luminosity LHC.
The unprecedented interaction rate at the High-Luminosity LHC (HL-LHC) will require a significant overhaul of the Trigger, Data Acquisition and Computing strategy of the experiments. In this talk the planned strategies and upgrades for these critical components of the overall upgrade programme of the experiments are presented. In addition to performing precision studies of the properties of the newly discovered Higgs boson, the physics programme of the HL-LHC will also continue to search for New Physics beyond the standard model. On the example of Supersymmetry and a few selected other BSM channels like the search for Dark Matter production in pp collisions, the reach of New Physics searches at the HL-LHC are illustrated.
Dr Pippa Wells, CERN, SwitzerlandThe upgraded ATLAS and CMS detectors and their physics capabilities I & II
Pippa Wells is a physicist at CERN, the European Laboratory for Particle Physics. She first visited the lab in 1986 as a summer student for two months. After completing her PhD at the University of Cambridge, she took up a CERN fellowship and then a staff position, working on the OPAL experiment at the LEP collider. This included taking into account the effects of local electric trains on the LEP magnets, and earth tides on the accelerator tunnel, to make precise measurements of the Z and W boson masses. She is now a member of the ATLAS collaboration at the Large Hadron Collider. After a number of years as project leader of the innermost part of the detector, which measures the tracks of charged particles as they emerge from the interaction point, she now coordinates studies of the physics potential of the high-luminosity LHC and the associated detector upgrades."
The update of the European Strategy for Particle Physics from 2013 states that Europe’s top priority should be the exploitation of the full potential of the LHC, including the high-luminosity upgrade of the machine and detectors with a view to collecting ten times more data than in the initial design. The plans for upgrading the ATLAS and CMS detectors so as to maintain their performance with increasing luminosity are presented here. A cornerstone of the physics programme is to measure the properties of the 125 GeV Higgs boson with the highest possible precision, to test its consistency with the Standard Model. The high-luminosity data will allow precise measurements of the dominant production and decay modes, and offer the possibility of observing rare modes including Higgs boson pair production. Direct and indirect searches for additional Higgs bosons beyond the Standard Model will also continue.
Professor Terry Wyatt FRS, University of Manchester, UKFuture accelerators for Higgs studies
Prof Terry Wyatt FRS is an experimental particle physicist who is distinguished for a number of original andimportant contributions to the experimental verification of the Standard Model (SM). By combining unusualexpertise in detector performance with exceptional insight into the topological features of differentinteraction dynamics, Wyatt has developed and implemented powerful new discriminants of signatures forthe production of heavy quarks (b and t) and electroweak bosons (W and Z). His application of thesetechniques in electron-positron interactions (LEP at CERN) and in proton-antiproton interactions (theSPS collider at CERN and the Tevatron at Fermilab) has resulted in measurements of unprecedentedprecision. He led the D0 experiment at Fermilab as its spokesperson from 2004-2007. He now works onthe ATLAS experiment at the CERN LHC and serves as a member of the CERN Scientific Policy Committee.
Beyond the LHC a number of possible future particle colliders have the potential to play an important role in measuring the properties of the already-discovered Higgs boson and/or searching for additional Higgs bosons. The prospects for the following future machines will be reviewed: circular or linear electron-positron, muon-antimuon, photon-photon, electron-proton, and very high energy hadron-hadron colliders.
Professor John Ellis FRS, Kings College London, UKClosing discussion
Book prize event 6 Mar
History of science lecture 7 Mar
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