Emmanuel Tsesmelis

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applications of acceleratorsparticle
physics

• Emmanuel Tsesmelis
• CERN/Oxford
• University of Oxford
• 1 December 2009

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introduction
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Evolution of the Universe
Big Bang
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The Study of Elementary Particles and Fields and
their Interactions
In 50 years, weve come a long way, but there is
still much to learn
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(No Transcript)
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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.

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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 todays accelerator projects
  are high
• International co-operation and collaboration are
  obligatory

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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

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Todays 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

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Todays 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

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Todays Accelerators

• Lepton Colliders (ee-)
• 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)

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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 (ee-) energy frontier
• Neutrino Factory (µ or µ-)
• Super-B Factory (ee-)
• Energy Frontier
• sLHC
• CLIC (ee-) precision frontier
• Muon Collider (µµ-)

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THE Large hadron Collider
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CERN Accelerator Complex
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LHC Accelerator Experiments
CMS/TOTEM
LHCb
ATLAS/LHCf
ALICE
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The Large Hadron Collider
High repetition rate 40 MHz or 25 ns bunch
spacing
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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.

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LHC Nominal Performance
Bunch spacing 25 ns.
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LHC Main Bending Cryodipole
8.3 T nominal field 11850 A nominal field
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The LHC Arcs
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The LHC Experimental Challenge
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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 mHlt 1 TeV
• ATLAS CMS are general-purpose detectors and can
  study the production of a variety of particles.
• e.g. Supersymmetric particle production

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The ATLAS Experiment
Number of scientists 2200 Number of
institutes 167 Number of countries 37
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The ATLAS Experiment
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First Collisions - ATLAS
450 GeV x 450 GeV pp collision
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Electro-weak phase transition (ATLAS, CMS)
QCD phase transition (ALICE, CMS)
LHC will study the first 10-10 -10-5 seconds
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Cross sections at the LHC
Well known processes. Dont need to keep all
of them
New Physics!! We want to keep!!
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The BEH Mechanism()
()Brout-Englert-Higgs
EPS09
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Higgs Searches
High MH gt 500 GeV/c2
Medium 130ltMHlt500 GeV/c2
Low MH lt 140 GeV/c2

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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
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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

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Picture from Marusa Bradac
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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!!

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Peak Luminosity
New Injectors IR Upgrade Phase 2
Linac4 IR Upgrade Phase 1
Early operation
Collimation Phase 2
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Integrated Luminosity
New Injectors IR Upgrade Phase 2
Linac4 IR Upgrade Phase 1
Early operation
Collimation Phase 2
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LHC Upgrade
Present Accelerators
Future Accelerators
Proton flux / Beam power
Linac4
Linac2
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
SPS
450 GeV
1 TeV
LHC / SLHC
DLHC
7 TeV
14 TeV
Intermediate step in reaching 1035 cm-2s-1
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Layout of the New Injectors
SPS
PS2
ISOLDE
PS
SPL
Linac4
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Interaction RegionFinal Focusing
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The Tevatron at FERMILAB
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The Tevatron at FERMILAB
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Linear ColliDers
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Colliders Energy vs. Time

• pp and ee- colliders
• have been operational
• simultaneously

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Linear ee- Colliders

• The machine which will complement and extend the
  LHC best, and is closest to be realized, is a
  Linear ee- 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) ? RD CLIC ? Two Beam Acceleration
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A Generic Linear Collider
30-40 km
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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 -gt 6000 bunches IP sx 350 620 nm
sy 3.5 9.0 nm Total power 230
MW Accelerating Gradient 31.5 MeV/m
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The International Linear Collider
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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 gt few 1034 cm-2 s-1 with low machine-induced
  background
• Minimise power consumption and costs

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CLIC Overall Lay-out
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Basic Features
CLIC TUNNEL CROSS-SECTION

• High acceleration gradient gt 100 MV/m
• Compact collider total length lt 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
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
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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

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CLIC Parameters
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Generic Detector Concepts
A lot of RD work on detectors is in
progress good tracking resolution, jet flavour
tagging, energy flow, hermeticity,
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Indicative Physics Reach
Ellis, Gianotti, de Roeck Hep-ex/0112004 updates
Units TeV (except WLWL reach)
indirect search (from precision measurements)
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Muon accelerators
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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

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Muon Beam Challenges

• 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

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Neutrino Factory
Aim for 1021 ?e per year directed towards
detector(s)
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Muon Collider
e.g. _at_ FNAL
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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.