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LHC physics

LHC physics. Dr Alan J Barr For the TeV -scale p hysics group. 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…”

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LHC physics

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  1. LHC physics Dr Alan J Barr For the TeV-scale physics group

  2. 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 LHC Physics

  3. Oxford’s international standing Stellarinternationalreputation (Even before talking about accelerators & theory…) • Global experimental leadership in: • Detectors • Tracker R&D • Construction & upgrade • Monte Carlo Simulation • Triggering / selection algorithms • Calibration • Exploitation / analysis LHC Physics

  4. Large Hadron Collider 1 MJ melts 1.5 kg Cu LHC Physics

  5. The accelerator… 1232 x 14.3 m dipoles Superconducting SuperfluidLiquid Helium Cooled LHC Physics

  6. ATLAS Segment of 4π detector LHC Physics

  7. Semiconductor Tracker… • Robotic assembly of precision silicon tracker 2004  2005 LHC Physics

  8. LHC Physics

  9. 4Tm Dipole Vertex Locator (Silicon) Muon System RICH detectors Tracking Calorimeters The LHCb spectrometer LHC Physics

  10. RICH1 Front-end electronics Johan Fopma, Phil Sullivan & the electronics workshop team PIXEL anodes Kaptons Level-0 board LHC Physics

  11. RICH1 Mechanics Mike Tacon & the workshop team • Design and constructed the lower HPD mounting system • Designed the upper system • Designed the RICH gas enclosure

  12. 2009: Cosmic rays Precision alignment Calibrations Data acquisition Combined tests LHC Physics

  13. March 2010: first collisions LHC Physics

  14. First B+ → J/K+ candidate 5 April 2010, 01:30:09 LHC Physics

  15. LAST WEEK 2010  0.035 fb-1 Huge reach even then LHC Physics

  16. The Standard Model Fields (Maxwell, Weak, Strong) Fermions (Dirac…) Masses & potentials. (Untested) LHC Physics

  17. Sure things 45 physics publications from ATLAS on last year’s beam data Strong interaction Weak interaction Higgs Sector or other EWSB Flavours 3rdgeneration quarks (t and b) CP violation LHC Physics

  18. 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 LHC Physics

  19. CM Energy = 4 TeV Dijets @ muliti-TeV Excited quarksQuantum Black HolesContact interactions LHC Physics

  20. Weak interactions WW ZZ Masses and couplings well known Self-interactions under study Cross-sections diverge without new physics LHC Physics

  21. W charge asymmetry Vector – Axial couplings (Chiral couplings) Probe proton structure (Parton distributions) Cancellation of systematic uncertainties LHC Physics

  22. Higgs sector – the model LHC sensitivity to almost all SM Higgs masses 2011-12 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) LHC Physics

  23. Higgs boson production and decay • Coupling  mass • Production • Gluon fusion • Weak boson fusion • Decay • To heaviest allowed states LHC Physics

  24. Last week: full ATLAS search Higgs analysis of 2010 data LHC Physics

  25. Higgs search status LHC Physics

  26. LHC Physics

  27. 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? LHC Physics

  28. LHC Physics

  29. Using quantum corrections Over-constrain SM parameters Hunt for rare processes 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 LHC Physics

  30. Effect of Particle ID on f → K+ K- • Early 900 GeV data • Hard-ish RICH cut on each kaon track DLL(K-pi)>15

  31. CPviolation Bd0 Bs0 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

  32. More speculative (perhaps?)… Further generations Unification of forces Supersymmetry WIMPs Compositeness / substructure New gauge forces / particles Strong gravity Extra dimensions Something else? LHC Physics

  33. Supersymmetry Partner particles Spin differ by ½ Stabilise mH Dark Matter candidates “Missing” momentum Huge reach at LHC LHC Physics

  34. Results 3 June 2011 25 Feb 2011 “Missing” momentum Scalar sum of momentum LHC Physics

  35. Interpretation... G. Ross et al ATLAS 0 lepton CMST 2010 data  approach cosmologically interesting region LHC Physics

  36. 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 LHC Physics

  37. Existing tracker Unique Oxford capabilities All Si-upgrade LHC Physics

  38. Software Operations Hardware Grid Detector & Upgrade Computing LHC Physics

  39. AJB Extra slides LHC Physics

  40. Semiconductor Tracker close-up LHC Physics

  41. LHC Physics

  42. Four Detectors <10> inelastic collisions @ 20 MHz crossing rate Record ~100 events/s 1 MB per event Micron-scale precision ATLAS LHCb ALICE CMS LHC Physics

  43. Higgs  diphoton LHC Physics

  44. December 2008 LHC Physics

  45. 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 CMS μ asymmetry 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

  46. Search for the ultra-rare decays B0s & B0d→ 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(B0d→ m+m-) < 0.01 x 10-8 • Approacing the world’s best measurement already with 2010 data

  47. B0s → J/f (Early 2011 data) • Important for measurement of weak mixing phase in Bs system • Amazingly small background

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