Department of Physics

LHC physics

Dr Alan J BarrFor 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 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 PhysicsPage 7

Page 8LHC Physics 22nd June 2011

The LHCb spectrometer

VertexLocator(Silicon)

RICH detectors Tracking Calorimeters

4TmDipole

MuonSystem

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22nd June 2011LHC PhysicsPage 10

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

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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

22nd June 2011Page 21

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 → 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

22nd June 2011Page 34

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 schedulesLHC 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

42

CMS

LHCb ATLAS

ALICE

Four Detectors<10> inelastic collisions @ 20 MHz crossing rateRecord ~100 events/s1 MB per eventMicron-scale precision

22nd June 2011

LHC Physics

Higgs diphoton

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LHC Physics

December 2008

22nd June 2011Page 44

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 → +-

• The upper limits on the branching ratios are BR(B0s → +-) < 5.6 x 10-8 and BR(B0

d

→ +-) < 1.5 x 10-8 at 95% confidence level. • Standard model expectations BR(B0

s → +-) < 0.32 x 10-8 and BR(B0d → +-)

< 0.01 x 10-8

• Approacing the world’s best measurement already with 2010 data

B0s → J/ (Early 2011 data)

• Important for measurement of weak mixing phase in Bs system

• Amazingly small background