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

2. introduction

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

4. 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…

5. 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

6. 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.

7. 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

8. 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

9. 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

10. 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

11. 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)

12. 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-)

13. THE Large hadron Collider

14. CERN Accelerator Complex

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

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

17. 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.

18. LHC Nominal Performance
Nominal settings
Beam energy (TeV)
7.0
Number of particles per bunch
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.

19. LHC Main Bending Cryodipole
8.3 T
nominal field
11850 A

20. The LHC Arcs

21. The LHC Experimental Challenge

22. 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

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

24. The ATLAS Experiment 24

25. First Collisions - ATLAS
450 GeV x 450 GeV pp collision

26. 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
seconds…

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

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

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

30. 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

31. 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

32. 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

33. 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

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

35. 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

36. Layout of the New Injectors
SPS
PS2
ISOLDE PS
SPL
Linac4

37. Interaction Region Final Focusing

38. The Tevatron at FERMILAB

39. The Tevatron at FERMILAB

40. Linear ColliDers 40

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

42. 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

43. A Generic Linear Collider
30-40 km

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

45. The International Linear Collider

46. 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

47. CLIC Overall Lay-out

48. 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

49. 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

50. CLIC Parameters

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

52. Indicative Physics Reach
Ellis, Gianotti, de Roeck
Hep-ex/ 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
† indirect search (from precision measurements)

53. Muon accelerators 53

54. 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

55. 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

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

57. Muon Collider
FNAL

58. 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.