department of physics lhc physics dr alan j barr for the tev-scale physics group
TRANSCRIPT
Department of Physics
LHC physics
Dr Alan J Barr
For the TeV-scale physics group
22nd June 2011LHC Physics
Oxford:Synonymous with subatomic physics
Frederic Soddy (1877–1956) Transmutation: “The interpretation of Radium”
Dick Dalitz (1925-2006) “I used to know all the data; at one time I knew every
event…” Denys Wilkinson (1922-)
Creation of the Nuclear physics laboratory 1964 International cadre of Oxford-trained physicists
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LHC Physics
Oxford’s international standing
Global experimental leadership in:DetectorsTracker R&DConstruction & upgradeMonte Carlo SimulationTriggering / selection algorithmsCalibrationExploitation / analysis
22nd June 2011
Stellarinternationalreputation
(Even before talking about accelerators & theory…)
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LHC Physics
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
22nd June 2011
1 MJ melts 1.5 kg Cu1 MJ melts 1.5 kg Cu
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LHC Physics
The accelerator…1232 x 14.3 m dipolesSuperconducting SuperfluidLiquid Helium Cooled
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LHC Physics
ATLAS
Segment of 4π detector
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Semiconductor Tracker…
Robotic assembly of precision silicon tracker
2004 2005
22nd June 2011LHC Physics
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LHC Physics 22nd June 2011
The LHCb spectrometer
VertexLocator(Silicon)
RICH detectors Tracking Calorimeters
4TmDipole
MuonSystem
22nd June 2011LHC Physics
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22nd June 2011LHC Physics
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RICH1 Front-end electronics Johan Fopma, Phil Sullivan & the electronics workshop team
PIXEL anodes
Level-0 board
Kaptons
RICH1 Mechanics Mike Tacon & the workshop team
Design and constructed the lower HPD mounting system
Designed the upper system
Designed the RICH gas enclosure
LHC Physics 22nd June 2011
2009:Cosmic rays
Precision alignment
Calibrations
Data acquisition
Combined tests
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LHC Physics
13March 2010: first collisions
22nd June 2011
First B+ → J/ K+ candidate
5 April 2010, 01:30:09
22nd June 2011LHC Physics
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LHC Physics 22nd June 2011Page 15
2010 0.035 fb-1
Huge reach even then
LAST WEEK
LHC Physics
The Standard Model
22nd June 2011
Fields (Maxwell, Weak, Strong)
Fermions (Dirac…)
Masses & potentials.(Untested)
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LHC Physics
Sure things
Strong interaction
Weak interaction
Higgs Sector or other EWSB
Flavours 3rd generation quarks (t and b)
CP violation
22nd June 2011
45 physics publications from ATLAS on last year’s beam data
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LHC Physics
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
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LHC Physics
Dijets @ muliti-TeV
22nd June 2011
Excited quarksQuantum Black HolesContact interactions
CM Energy = 4 TeV
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LHC Physics
Weak interactions Masses and
couplings well known
Self-interactions under study
Cross-sections diverge without new physics
22nd June 2011
ZZ
WW
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LHC Physics
W charge asymmetry
Vector – Axial couplings (Chiral couplings) Probe proton structure (Parton distributions) Cancellation of systematic uncertainties
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LHC Physics
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)
22nd June 2011
LHC sensitivity to almost all SM Higgs masses 2011-12
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LHC Physics
Higgs boson production and decay
Coupling mass Production
Gluon fusion Weak boson fusion
Decay To heaviest allowed
states
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LHC Physics 22nd June 2011
Last week: full ATLAS search Higgs analysis of 2010 data
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LHC Physics 22nd June 2011
Higgs search status
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LHC Physics 22nd June 2011Page 26
LHC Physics
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?
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LHC Physics 22nd June 2011Page 28
LHC Physics
Using quantum corrections For example: Tree and penguin-level determinations
of CKM angle Charmless charged two-body B decays Bs mixing phase s from
Bs → J/ Branching fraction of
Bs → +-
Angular distributions in B0 → K*+-
Bs → and other radiative decays
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Over-constrain SM parameters
Hunt for rare processes
Effect of Particle ID on f → K+ K-
Early 900 GeV data Hard-ish RICH cut on each kaon track DLL(K-pi)>15
Example of CP violation measurement 2010 data Separate samples into B0 and B0 using particle ID Raw asymmetries clearly visible in data: direct CP Violation > 3s Central values consistent with expectations and previous
measurements NB: corrections from production and detector asymmetry not yet
corrected for
LHC Physics
More speculative (perhaps?)… Further generations Unification of forces Supersymmetry WIMPs Compositeness / substructure New gauge forces / particles Strong gravity Extra dimensions Something else?
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LHC Physics
Supersymmetry
Partner particles Spin differ by ½ Stabilise mH
Dark Matter candidates
“Missing” momentum
Huge reach at LHC
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LHC Physics
Results
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3 June 201125 Feb 2011
“Missing” momentum Scalar sum of momentum
LHC Physics
Interpretation...
22nd June 2011
ATLAS 0 lepton
CMST
G. Ross et al
2010 data approach cosmologically interesting region
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LHC Physics
LHC and ATLAS upgrade schedules
LHC Phase-0 Shutdown:
End 2012-mid 2013 Physics resumes 2014
Phase-I shutdown End of 2017 Physics resumes end of
of 2018 Phase-II
End of 2021
ATLAS Phase-0
IBL installation Repairs/consolidation
Phase-I shut down Muon small wheels Mini-FCAL L1 calo topological trigger Calorimeter readout NewPix
Phase-II Tracker ready on surface
end of 2020 TDAQ
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LHC Physics 22nd June 2011
Unique Oxford capabilities
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Existing tracker
All Si-upgrade
LHC Physics
Detector & Upgrade
Grid
Operations
Computing
Software
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Hardware
LHC Physics
EXTRA SLIDESAJB
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LHC Physics
Semiconductor Tracker close-up
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LHC Physics 22nd June 2011Page 41
LHC Physics
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CMS
LHCb ATLAS
ALICE
Four Detectors
<10> inelastic collisions @ 20 MHz crossing rate
Record ~100 events/s
1 MB per event
Micron-scale precision
22nd June 2011
LHC Physics
Higgs diphoton
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LHC Physics
December 2008
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PDFs are determined in Deep Inelastic Scattering- STRONG Oxford involvement in HERAPDF-
But can be used to predict cross sections for the LHC. Early LHC data, using 36pb-1, are well predicted using HERAPDFs
ATLAS jets
These data can also be input to the fit to reduce the uncertainties
The CMS muon asymmetry data already reduces the uncertainties on the low-x u and d-valence PDFs
These improvements allow us to predict Standard Model cross sections with greater certainty so that the signal/background for Beyond Standard Model physics is enhanced
CMS μ asymmetry
Search for the ultra-rare decays B0s & B0
d → m+m-
• The upper limits on the branching ratios are BR(B0s → m+m-) < 5.6 x 10-8 and
BR(B0d → m+m-) < 1.5 x 10-8 at 95% confidence level.
• Standard model expectations BR(B0s → m+m-) < 0.32 x 10-8 and BR(B0
d → m+m-) < 0.01 x 10-8
• Approacing the world’s best measurement already with 2010 data
B0s → J/ f (Early 2011 data)
• Important for measurement of weak mixing phase in Bs system
• Amazingly small background