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The LHC THE STORY SO FAR
Alan BarrUniversity of Oxford
PASCOS, July 2011
Alan Barr
LHC
The Standard Model
4th July 2011
Fields (Maxwell, Weak, Strong)
Fermions (Dirac…)
Masses & potentials.(Untested)
Page 2
+ other terms?
Alan Barr
LHC
The accelerator…1232 x 14.3 m dipolesSuperconducting Superfluid (1.9K)Liquid Helium Cooled
4th July 2011
Page 3
7 TeV CM energy 14 TeV
~1 GJ Magnetic Energy
~100 MJ Beam Energy
1 MJ melts 1.5 kg Cu1 MJ melts 1.5 kg Cu
Alan Barr
LHC
Alan Barr
LHC
CMS
LHCb ATLAS
ALICE
2 x general-purpose experiments energy, momentum, identification controlled environment ~ 109 collision / second ~ decade of operation
Alan Barr
LHC Page 5
4th July 2011
ATLAS
Segment of 4π detector
Alan Barr
LHC
Local Interest: ATLAS Semiconductor Tracker…
4th July 2011
Page 7
Cambridge: Silicon R&D, testing Robotic assembly
Alan Barr
LHC 8
4th July 2011
A year is a long time at the LHC
PASCOS 2010 PASCOS 2011 x
Bunches / beam 25 1380 55
Protons / bunch 2 x 1010 1.2 x 1011 6
Lumi / day 60 nb-1 50 pb-1 800
Integrated 200 nb-1 1.3 fb-1 6500
Commissioned bunch trains50 ns bunch-crossing operation
Alan Barr
LHC4th July 2011
Page 9
PASCOS 2010 0.0002 fb-1
1 fb-1 target
Alan Barr
LHC
Alan Barr
LHC
Sure things @ TeV-scale
Strong interaction
Weak interaction
Higgs Sector or other Electroweak SB
Flavours 3rd generation quarks (t and b)
CP violation
4th July 2011
~ 100 physics publications on collision data from CMS + ATLAS
Page 10
Alan Barr
LHC
Alan Barr
LHC
Strong interactions Self-interacting force
carriers Perturbative regime
Jets of hadrons Radiation from accelerated
colour Backgrounds to all other
searches Non-perturbative
Quark-gluon plasma Nucleon structure
4th July 2011
Page 11
ATLAS
Alan Barr
LHC4th July 2011
Page 12
CMS-QCD-10-011
Agreementover 10 decades
NLOMonte Carlo
DATAdeconvolved
Uncertaintiesin Jet EnergyScale understood
Alan Barr
LHC
Dijets @ muliti-TeV
4th July 2011
CM Energy = 4 TeV
Page 13
ATLAS
ATLAS-CONF-2011-081
Alan Barr
LHC
Alan Barr
LHC
Strong interactions – papers Inelastic cross section Jet cross sections Jet shapes Dijet azimuthal decorrelations Dijet resonances Underlying event Charged hadron distributions Bose-Einstein correlations Strong contact interactions Event shapes
4th July 2011
Page 14
Alan Barr
LHC
Alan Barr
LHC
Weak interactions Masses and
couplings well known
Self-interactions under study
Cross-sections diverge without new physics
4th July 2011
ZZ
WW
Page 15
Alan Barr
LHC
Electroweak cross sections
4th July 2011
Page 16
Alan Barr
LHC
W + Jets
Electroweak + strong radiation
Background to many searches
Test MC simulations
4th July 2011
Page 17
ATLAS-CONF-2011-060
Alan Barr
LHC
After you understand the Z…
4th July 2011
Page 18
ATLAS-CONF-2011-083
Excludes SM-like Z’ M<1.41 TeV
Alan Barr
LHC
Alan Barr
LHC
Higgs sector – the model
Field couples to mass
Scalar potential
Vacuum expectation value
W, Z masses via Higgs/gauge interactions
Fermion masses via Higgs/Yukawa coupling
Field excitation = Higgs boson(s)
4th July 2011
LHC sensitivity to almost all SM Higgs masses 2011-12
Page 19
Alan Barr
LHC
Alan Barr
LHC
Higgs boson production and decay
Coupling mass Production
Gluon fusion Weak boson fusion
Decay To heaviest allowed
states
4th July 2011
Page 20
Alan Barr
LHC4th July 2011
15 June: full ATLAS search Higgs analysis of 2010 data
Page 21
arXiv:1106.2748
Alan Barr
LHC
Higgs WW (search)
4th July 2011
Page 22
Alan Barr
LHC4th July 2011
Higgs search status
Page 23
Alan Barr
LHC
Higgs (search)
4th July 2011
Page 24
CMS-PAS-HIG-10-002
Alan Barr
LHC
Alan Barr
LHC
3rd Generation: t and b
Three generations needed for CP violation
Nearly decoupled from first two generations
Long lived b-quark hadrons
Standard Model: top Higgs coupling ~unity
Radiative corrections from top on mH
Role in electroweak symmetry breaking?
4th July 2011
Page 25
Alan Barr
LHC
Alan Barr
LHC
Papers (flavour)
Cross sections and single mass of top jets Upsilon () J/Psi () Strange
4th July 2011
Page 26
arXiv:1106.0902
Alan Barr
LHC4th July 2011
Page 27
ATLAS-CONF-2011-087
Alan Barr
LHC
Alan Barr
LHC
More speculative (perhaps?)… Further generations Unification of forces Supersymmetry WIMPs Compositeness / substructure New gauge forces / particles Strong gravity Extra dimensions Something else?
4th July 2011
Page 28
Physics Beyond the Standard Model
29
New results with 2011
data
Alan Barr
LHC
Alan Barr
LHC
Supersymmetry
Partner particles Spin differ by ½ Stabilise mH
Dark Matter candidates
“Missing” momentum
Big reach at LHC
4th July 2011
Page 30
Alan Barr
LHC
Alan Barr
LHC
Supersymmetry searches
4th July 2011
Page 31
“Missing” momentum Scalar sum of momentum
arXiv:1106.5048
ATLAS-CONF-2011-086
Alan Barr
LHC
Alan Barr
LHC
Interpretation Simplified
model Squark, gluino,
massless neutralino
Exclude mq = mg < 1.02 TeV
Degenerate points harder
4th July 2011
Page 32
ATLAS-CONF-2011-086
Wider interpretation...
23/03/2011 Alan Barr, University of Oxford 33
http://arxiv.org/abs/1103.0969
Allanach, Khoo, Lester, Williams
Cassel, Ghilencea, Kraml, Lessa, Rosshttp://arxiv.org/abs/1101.4664
Points sampled from fits to global data Global CMSSM fits
Regions with low fine tuning
ATLAS 0/1 leptonATLAS-CONF-2011-086
CMS αT June’11
Jan’11
h
H~𝐵
~𝐻
Alan Barr
LHC
Alan Barr
LHC
Getting the results? ATLAS
Public results: link CMS
Public results: link Recent conference
Physics at the LHC 2011, ; link Upcoming new results:
EPS 2011, 21-27 July; link
4th July 2011
Page 34
Alan Barr
LHC
Alan Barr
LHC
Conclusions Excellent operation of LHC and detectors
> 1 fb-1
Remarkable degree of control New Physics Searches leading the world
Supersymmetry / WIMPs Resonances Substructure …
Sufficient data for Higgs search Over wide range of SM cross-sections Full range by end 2012?
4th July 2011
Page 35
Alan Barr
LHC
EXTRA SLIDESLHC PHYSICS
4th July 2011
Page 36
Alan Barr
LHC
2011 Plans…
4th July 2011
Page 37
Alan Barr
LHC
Alan Barr
LHC
Detector & Upgrade
Grid
Operations
Computing
Software
4th July 2011
Page 38
Hardware
Alan Barr
LHC4th July 2011
Page 39
http://indico.cern.ch/conferenceDisplay.py?confId=100963
Alan Barr
LHC
Alan Barr
LHC4th July 2011
Page 41
Alan Barr
LHC
Alan Barr
LHC
Large Hadron ColliderLEP[ CERN ]Geneva
HERA[ DESY ]Hamburg
TEVATRON[ FermiLab ]Chicago
LHC [ CERN ]Geneva
Particles: ElectronPositron
Electron-Proton
Proton-Anti-proton
Proton-Proton
Beam energy/TeV
0.105 e: 0.030p: 0.92
0.980 7.0(current 3.5)
Luminsoity(1030 cm-2 s-1)
100 75 402 10,000
Stored energy(magnets)
~ GJ
Stored energy(beam)
~ 100 MJ
4th July 2011
1 MJ melts 1.5 kg Cu1 MJ melts 1.5 kg Cu
Page 42
Alan Barr
LHC
Alan Barr
LHC
W charge asymmetry
Vector – Axial couplings (Chiral couplings) Probe proton structure (Parton distributions) Cancellation of systematic uncertainties
4th July 2011
Page 43
Alan Barr
LHC4th July 2011
Page 44
Pileup• The pileup in 2011 is on average <μ>=6
interactions per crossing• Significantly higher than 2010
• And than originally anticipated in early LHC running
• Tails up to 14 interactions per crossing• Due to some bunches with much higher currents
• Causes challenge for physics analyses and software• Detailed simulation models both the <μ>
and the bunch train structure• Reweighted according to data <μ> distribution
• Software performance significantly improved to accommodate Tier0 resources (reco time 11-13s/event)
• Physics performance reasonably unaffected• Jet energy scale uncertainty temporarily
increased for low pT jets
45
46
Summary of Electroweak Boson and Top Quark Cross Sections
• All measurements agree with SM expectation (so far)• Measuring cross sections of ~10 pb
Alan Barr
LHC
Further search papers
Others Monojets e-mu resonances Dilepton resonances
Leptoquarks CHAMPS Dimuons (contact)
W' l Z' l l
Supersymmetry: Squarks or gluinos
Lepton + jet + invis
Dilepton + invis
Same sign leptons + invis
Z + invis
b-jet(s) + invis
R-hadrons
4th July 2011
Page 47
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