applications of accelerators particle physics Emmanuel Tsesmelis CERN/Oxford University of Oxford 1 December 2009

introduction

Evolution of the Universe Big Bang Today 13.7 Billion Years 1028 cm United Kingdom and CERN / May 2009

The Study of Elementary Particles and Fields and their Interactions gauge x8 In 50 years, we’ve come a long way, but there is still much to learn…

Atom Proton Big Bang Radius of Earth Radius of Galaxies Earth to Sun Universe cm Super-Microscope LHC Study physics laws of first moments after Big Bang. Increasing Symbiosis between Particle Physics, Astrophysics and Cosmology. Hubble ALMA VLT WMAP 5

Open Questions in Particle Physics What is the origin of particle masses? Why are there so many types of matter particles? What is the cause of matter-antimatter asymmetry? What are the properties of the primordial plasma? What is the nature of the invisible dark matter? Can all fundamental particles be unified? Is there a quantum theory of gravity? The present and future accelerator-based experimental programmes will address all these questions and may well provide definite answers.

Introduction - Accelerators Historically, HEP has depended on advances in accelerator design to make scientific progress cyclotron  synchrocyclotron  synchrotron  collider (circular, linear) Advances in accelerator design and performance require corresponding advances in accelerator technologies Magnets, vacuum systems, RF systems, diagnostics,... Accelerators enable the study of particle physics phenomena under controlled conditions Costs & time span of today’s accelerator projects are high International co-operation and collaboration are obligatory

Introduction - Accelerators Particle accelerators are designed to deliver two parameters to the HEP user Energy Luminosity Measure of collision rate per unit area Event rate for a given event probability (“cross-section”) given by: For a Collider luminosity is given by  Require intense beams and small beam sizes at IP

Today’s Accelerators HEP typically uses Colliders Counter-propagating beams that collide at one or more IPs Colliders typically store various types of particles Hadrons (protons, ions) Tevatron (p, anti-p), RHIC (p, ions), LHC (p, ions) Leptons (electrons) CESR-c, PEP-II, KEK-B

Today’s Accelerators Hadron Colliders Protons are composite particles Only ~10% of beam energy available for hard collisions producing new particles Need O(10 TeV) Collider to probe 1 TeV mass scale Desired high energy beam requires strong magnets to store and focus beam in reasonable-sized ring. Anti-protons difficult to produce if beam is lost Use proton-proton collisions instead Demand for ever-higher luminosity has led LHC to choose proton-proton collisions Many bunches (high bunch frequency) Two separate rings that intersect at select locations

Today’s Accelerators Lepton Colliders (e+e-) Synchrotron radiation is the most serious challenge Emitted power in circular machine is For a 1 TeV CM energy Collider in the LHC tunnel with a 1 mA beam, radiated power would be 2 GW Would need to replenish radiated power with RF Remove it from vacuum chamber Approach for high energies is Linear Collider (ILC,CLIC)

Future Accelerators Currently, there are several machines under design to address open issues in HEP Not all of the future machines are at the same stage of development Costs are typically high  it is likely that not all will be built Precision Frontier ILC (e+e-) + energy frontier Neutrino Factory (µ+ or µ-) Super-B Factory (e+e-) Energy Frontier sLHC CLIC (e+e-) + precision frontier Muon Collider (µ+µ-)

THE Large hadron Collider

CERN Accelerator Complex

LHC Accelerator & Experiments CMS/TOTEM LHCb ATLAS/LHCf ALICE

The Large Hadron Collider High repetition rate 40 MHz or 25 ns bunch spacing

LHC Lay-out The LHC is a two-ring superconducting proton-proton collider made of eight 3.3 km long arcs separated by 528 m Long Straight Sections. While the arcs are nearly identical, the straight sections are very different.

LHC Nominal Performance Nominal settings Beam energy (TeV) 7.0 Number of particles per bunch 1.15 1011 Number of bunches per beam 2808 Crossing angle (rad) 285 Norm transverse emittance (m rad) 3.75 Bunch length (cm) 7.55 Beta function at IP 1, 2, 5, 8 (m) 0.55,10,0.55,10 Derived parameters Luminosity in IP 1 & 5 (cm-2 s-1) 1034 Luminosity in IP 2 & 8 (cm-2 s-1)* ~5 1032 Transverse beam size at IP 1 & 5 (m) 16.7 Transverse beam size at IP 2 & 8 (m) 70.9 Stored energy per beam (MJ) 362 * Luminosity in IP 2 and 8 optimized as needed Bunch spacing 25 ns.

LHC Main Bending Cryodipole 8.3 T nominal field 11850 A

The LHC Arcs

The LHC Experimental Challenge

ATLAS and CMS Of central importance for ATLAS & CMS and for the Collider is to elucidate the nature of electroweak symmetry breaking for which the Higgs mechanism (and accompanying Higgs boson(s)) are presumed to be responsible. Discover the Higgs Boson(s) for mH< 1 TeV ATLAS & CMS are general-purpose detectors and can study the production of a variety of particles. e.g. Supersymmetric particle production

The ATLAS Experiment Number of scientists: 2200 Number of institutes: 167 Number of countries: 37 23

The ATLAS Experiment 24

First Collisions - ATLAS 450 GeV x 450 GeV pp collision

LHC will study the first 10-10 -10-5 seconds… Electro-weak phase transition (ATLAS, CMS…) QCD phase transition (ALICE, CMS…) LHC will study the first 10-10 -10-5 seconds…

Cross sections at the LHC “Well known” processes. Don’t need to keep all of them … New Physics!! We want to keep!!

The BEH Mechanism(*) (*)Brout-Englert-Higgs EPS09

Higgs Searches Low MH < 140 GeV/c2 Medium 130<MH<500 GeV/c2 High MH > ~500 GeV/c2 29 29

Search for Higgs at LHC Start-up Sizeable integrated luminosity is needed before significant inroads can be made in SM Higgs search. However, even with moderate luminosity per experiment, Higgs boson discovery is possible in particular mass regions. Example Reach ATLAS + CMS

Supersymmetry: A New Symmetry in Nature Beyond the Higgs Boson Supersymmetry: A New Symmetry in Nature Candidate Particles for Dark Matter  Produce Dark Matter in the lab SUSY particle production at the LHC 31 Picture from Marusa Bradac 31

Supersymmetry SUSY could be at the rendez-vous very early on! 10fb-1 Main signal: lots of activity (jets, leptons, taus, missing ET) Needs however good understanding of the detector & SM processes!! 32 32

New Injectors + IR Upgrade Phase 2 Linac4 + IR Upgrade Phase 1 Peak Luminosity New Injectors + IR Upgrade Phase 2 Linac4 + IR Upgrade Phase 1 Early operation Collimation Phase 2

Integrated Luminosity New Injectors + IR Upgrade Phase 2 Linac4 + IR Upgrade Phase 1 Early operation Collimation Phase 2

LHC Upgrade Linac2 Linac4 PSB LPSPL PS PS2 SPS SPS+ LHC / SLHC DLHC Present Accelerators Future Accelerators Proton flux / Beam power Linac2 Linac4 50 MeV 160 MeV PSB LPSPL 1.4 GeV 4 GeV LPSPL: Low Power Superconducting Proton Linac (4 GeV) PS2: High Energy PS (~ 5 to 50 GeV – 0.3 Hz) SPS+: Superconducting SPS (50 to1000 GeV) SLHC: “Superluminosity” LHC (up to 1035 cm-2s-1) DLHC: “Double energy” LHC (1 to ~14 TeV) PS 26 GeV PS2 50 GeV Output energy SPS 450 GeV SPS+ 1 TeV LHC / SLHC DLHC 7 TeV ~ 14 TeV Intermediate step in reaching 1035 cm-2s-1

Layout of the New Injectors SPS PS2 ISOLDE PS SPL Linac4

Interaction Region Final Focusing

The Tevatron at FERMILAB

The Tevatron at FERMILAB

Linear ColliDers 40

Colliders – Energy vs. Time pp and e+e- colliders have been operational simultaneously

Linear e+e- Colliders The machine which will complement and extend the LHC best, and is closest to be realized, is a Linear e+e- Collider with a collision energy of at least 500 GeV. PROJECTS:  TeV Colliders (CMS energy up to 1 TeV)  Technology ~ready NLC/GLC/TESLA ILC with superconducting cavities  Multi-TeV Collider (CMS energies in multi-TeV range)  R&D CLIC  Two Beam Acceleration

A Generic Linear Collider 30-40 km

International Linear Collider Baseline Design 250 250 Gev 250 Gev e+ e- Linear Collider Energy 250 Gev x 250 GeV # of RF units 560 # of cryomodules 1680 # of 9-cell cavities 14560 2 Detectors push-pull peak luminosity 2 1034 5 Hz rep rate, 1000 -> 6000 bunches IP : sx 350 – 620 nm; sy 3.5 – 9.0 nm Total power ~230 MW Accelerating Gradient 31.5 MeV/m

The International Linear Collider

CLIC Conceptual Design Site independent feasibility study aiming at the development of the technologies needed to extend e+ / e- linear colliders into the multi-TeV energy range. Ecm range complementary to that of the LHC & ILC Ecm = 0.5 – 3 TeV L > few 1034 cm-2 s-1 with low machine-induced background Minimise power consumption and costs

CLIC Overall Lay-out

Basic Features High acceleration gradient: > 100 MV/m CLIC TUNNEL CROSS-SECTION High acceleration gradient: > 100 MV/m “Compact” collider – total length < 50 km at 3 TeV Normal conducting acceleration structures at high frequency Novel Two-Beam Acceleration Scheme Cost effective, reliable, efficient Simple tunnel, no active elements Modular, easy energy upgrade in stages 4.5 m diameter QUAD POWER EXTRACTION STRUCTURE BPM ACCELERATING STRUCTURES Main beam – 1 A, 156 ns from 9 GeV to 1.5 TeV 100 MV/m Drive beam - 95 A, 240 ns from 2.4 GeV to 240 MeV 12 GHz – 64 MW

Main Parameters & Challenges High beam power (several MWatts) Wall-plug to beam transfer efficiency as high as possible (several %) Generation & preservation of beam emittances at I.P. as small as possible (few nmrad) Beam focusing to very small dimensions at IP (few nm) Beamstrahlung energy spread increasing with c.m. colliding energies

CLIC Parameters

Generic Detector Concepts A lot of R&D work on detectors is in progress: good tracking resolution, jet flavour tagging, energy flow, hermeticity,…

Indicative Physics Reach Ellis, Gianotti, de Roeck Hep-ex/0112004 + updates Units : TeV (except WLWL reach) PROCESS LHC sLHC LC 14 TeV 0.8 TeV 5 TeV 100 fb-1 1000 fb-1 500 fb-1 Squarks 2.5 3 0.4 WLWL 2σ 4σ 6σ 30σ Z’ 5 6 8† 30† Extra-dim (δ=2) 9 12 5-8.5† 30-55† q* 6.5 7.5 0.8 Λcompositeness 30 40 100 400 TGC (λγ) 0.0014 0.0006 0.0004 0.00008 † indirect search (from precision measurements)

Muon accelerators 53

Physics with Muon Beams Neutrino Sector Decay kinematics well known e  µ oscillations give easily detectable wrong-sign µ Energy Frontier Point particle makes full beam energy available for particle production Couples strongly to Higgs sector Muon Collider has almost no synchrotron radiation Narrow energy spread Fits on existing laboratory sites

Muon Beam Challenges Fast acceleration system Muons created as tertiary beam (p    µ) Low production rate Need target that can tolerate multi-MW beam Large energy spread and transverse phase space Need solenoidal focusing for the low-energy portions of the facility (solenoids focus in both planes simultaneously) Need acceptance cooling High-acceptance acceleration system and decay ring Muons have short lifetime (2.2 µs at rest) Puts premium on rapid beam manipulations Presently untested ionization cooling technique High-gradient RF cavities (in magnetic field) Fast acceleration system Decay electrons give backgrounds in Collider detectors and instrumentation & heat load to magnets

Aim for 1021 e per year directed towards detector(s) Neutrino Factory Aim for 1021 e per year directed towards detector(s)

Muon Collider e.g. @ FNAL

Summary and Conclusions Highest priority of the particle physics community is to fully exploit the physics potential of the LHC. The European Strategy for Particle Physics incorporates a number of new accelerator projects for the future. The need to renovate the LHC injectors is recognised and relevant projects/studies have been authorised. The main motivation to upgrade the luminosity of the LHC is to explore further the physics beyond the Standard Model while at the same time completing the Standard Model physics started at the LHC. Further down the line, many of the open questions from the LHC could be best addressed by lepton machines. An electron-positron collider (ILC or CLIC) in which all the centre-of-mass energy is made available for collisions between the colliding elementary particles. A neutrino factory/muon collider is also under design. These new initiatives will lead particle physics well into the next decades of fundamental research.