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Selected highlights from LHCb

Selected highlights from LHCb. Neville Harnew On behalf of the LHCb Collaboration University of Oxford Discrete 2012, Lisboa December 6th 2012. Outline. The LHCb detector and running conditions Selected physics highlights

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Selected highlights from LHCb

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  1. Selected highlights from LHCb Neville Harnew On behalf of the LHCb Collaboration University of Oxford Discrete 2012, Lisboa December 6th 2012

  2. Outline • The LHCb detector and running conditions • Selected physics highlights Focus on new measurements from LHCb: mostexamples are based on 1 fb-1 of 2011 pp collision data. • Parameters of the CKM matrix • Studies of CPV in the Bssystem • CP violation in charm • Rare B decays • Summary and Outlook

  3. 10 – 300 mrad p p LHCb- forward spectrometer • Forward-peaked production → LHCb is a forward spectrometer (operating in LHC collider mode) • bb cross-section = 284 ± 53 mb at s = 7 TeV [PLB 694 209] → ~ 100,000 bb pairs produced/second (104B factories) [PYTHIA] JINST 3:S08005 (2008)

  4. What the doomsayers said • “Hadron colliders are too dirty an environment for flavour-physics” • “Impossible to trigger efficiently on non-leptonic final states” • “It will take a long time to understand detector performance, and so physics output will take years to emerge”

  5. But if anyone was still left in any doubt… B+→(K+π-)Dπ+ D+,D+s→KKπ Phys Lett B712 (2012) 203 LHCb-PAPER-2012-026 ...and even with photons B+→(KSππ)DK+ B0→K*γ LHCb-PAPER-2012-027 LHCb-CONF-2012-004

  6. LHCb data taking • Nominal luminosity = 2 × 1032 cm-2 s-1 : however, LHCb has learned to run at >2 times this. • Continuous (automatic) adjustment of offset of colliding beams allows luminosity to be levelled • 37 pb-1 collected in 2010 • 1 fb-1 in 2011 • So far >2 fb-1recorded in 2012 – on track for 2.5 fb-1 before the long • shutdown

  7. LHCb 2012 data-taking in numbers

  8. Vertex reconstruction performance • Impact parameter resolution = 12 mm for high pT tracks from VELO detector. • Proper-time resolution: st = 45 fs • Bs–Bs oscillations measured: cf CDF: 17.77 ± 0.10 ± 0.07 ps-1 (st = 87 fs) [PRL 97 242003] Prompt J/y Bs J/y f LHCb-CONF-2011-50 LHCb-CONF-2011-49

  9. PID performance arXiv:1211.6759 • Allows strong suppression ofcombinatorial backgroundeg for f  K+K- • Kaon identification efficiency > 90%for pion misidentification < 5%over a large momentum range (2 < p < 100 GeV/c ) Calibration data Without RICH With

  10. arXiv:1211.3055 The LHCb trigger performance • Hardware level (L0): • 4 μs latency @ 40MHz • high-pT μ, e, γ, hadron candidates, typically • pT(μ)>1.4; ET(e/γ)>2.7; ET(hadron)>3.6 [GeV] • Software level (HLT): • ~30000 tasks in parallel on ~1500 nodes • Combined efficiency (L0+HLT): • ~90 % for di-muon channels • ~30 % for multi-body hadronic final states • Offline processing: • ~1010 events, 700 TB recorded per year • ~800 “stripping” selections to reduce to samples with 0(107) events for analyses

  11. Selected physics highlights • Parameters of the CKM matrix • Studies of CPV in the Bs system • CP violation in charm • Rare B decays

  12. Unitarity triangle : CKM fitter • The CKM describes all the flavour-changing processes in the SM • Amazing progress in the last 20 years; the SM remains intact, but still a whole lot still to learn http://ckmfitter.in2p3.fr 1995 2012 2004

  13. And now LHCb in the game … sin(2β) from B0→J/ψK0S LHCb-PAPER-2012-035 SJ/ψKs = 0.73 ± 0.07 (stat) ± 0.04 (syst) CJ/ψKs = 0.030 ± (stat) ± 0.012 (syst) 0.089 0.091 World average : sin(2β) = 0.667 ± 0.023 ± 0.012

  14. A measurement of g from B±  DK± and Dp± • Four methods, comprising 14 B± decays included in a combined fit See parallel talk of Laurence Carson “GGSZ” Phys Lett B718 (2012) 43 “K3p” : LHCb-CONF-2012-030 “ADS” Phys Lett B712 (2012) 203 “GLW” Phys Lett B712 (2012) 203

  15. B±  DK± andB±  Dπ± ADS & GLW modes B-  (p-K+)DK- B+  (p+K-)DK+ ADS modes B-  (p-K+)Dp- B+  (p+K-)Dp+ B-  (K+K-)DK- B+  (K+K-)DK+ GLW modes B+  (K+K-)Dp+ B-  (K+K-)Dp-

  16. B±  DK± andB±  Dπ± GGSZ & K(3π) modes GGSZ mode B+ B- (KSpp )D B-  (p-K+p+p-)DK- B+  (p-K+p+p-)DK+ K(3p) modes B-  (p-K+p+p-)Dp- B+  (p-K+p+p-)Dp+

  17. LHCb g combination LHCb-CONF-2012-032 • World average (before LHCb): g = 66o ± 12o • More data eagerly awaited BDK and BDp BDK only + 16.7 + 7.1 17 http://ckmfitter.in2p3.fr

  18. CP violation in Bp+p- & Bs K+K- (angle a/g) See parallel talk of Denis Derkach • 0.6 fb-1 : ~5.4k B0p+p- events • First time-dependent CP asymmetry plot of B0p+p- at a hadron collider • Also first ever time-dependent asymmetry seen in BsK+K- LHCb-CONF-2012-007

  19. Selected physics highlights • Parameters of the CKM matrix • Studies of CPV in the Bs system • CP violation in charm • Rare B decays

  20. See parallel talk of Jeroen van Leerdam Bs weak mixing phase fs in Bs J/y f • Analogue of 2b(phase of B0 mixing) in the Bs system is expected to be very small, and precisely predicted: fs = -0.036 ± 0.002 • VV final state: mixture of CP-odd and CP-even componentsSeparated using an angular analysis J/ψ rest frame frest frame • Golden mode for this study is Bs J/y f [f is vector meson] • First measurements from the Tevatron indicated large values for fsdiscrepancy with SM reaching ~3s LHCb-CONF-2012-002 Perform BsJ/Y f angular analysis Use opposite side tag: Power=(2.29 ± 0.07 ± 0.26)%

  21. Bs J/y f: fit projections CP-even CP-odd

  22. Results correlated with DGs= width difference of the Bsmass eigenstates plotted as contours in (fsvsDGs) plane LHCb-CONF-2012-002 Most significant direct measurement of fs&DGs DGs= 0.116 ± 0.018 ± 0.006 ps-1 fs = ‒0.001 ± 0.101 ± 0.027 rad Add in BsJ/Y ppfs= ‒0.002 ± 0.083 ± 0.027 Not much room for new physics, will continue to improve precision arXiv:1204.5675

  23. CP-violating asymmetry assl in Bs decays See parallel talk of Thomas Bird • CPV in mixing • First step to resolving the issue of the D0 di-muon asymmetry anomaly. • LHCb preliminary result for assl • D0 not confirmed nor ruled out (1.8s from LHCb result). More coming soon Phys. Rev. D 84, 052007 (2011), Phys. Rev. D 86, 072009 (2012) LHCb-CONF-2012-022

  24. Selected physics highlights • Parameters of the CKM matrix • Studies of CPV in the Bs system • CP violation in charm • Rare B decays

  25. Mixing and CP-violation in charm decays See parallel talk of Artur Ukleja

  26. Charm mixing measurement • Charm mixing has been confirmed by BaBar, Belle & CDF, but no clear observation in a single experiment. • LHCb measure the time-dependent ratio of D0 decays to Wrong Sign to Right Sign • Use the sign of the slow pion from D*+Dop+sandD*- Dop-s to tag the initial D0flavour The no mixing hypothesis is now excluded at the 9.1s level in a single experiment arXiv:1211.1230

  27. Signal window Signal window Phys. Rev. Lett. 108 (2012) 111602 First evidence for CP violation in charm Measure D0/D0(bar) decay asymmetries – charge of p from D* determines production state of the D0 In the Standard Model these asymmetries should be close to zero The quantity DACP= AK - Aπ is measured (since systematics largely cancel) DACP=[-0.82±0.21(stat)±0.11(sys)]% 3.5s different from zero • (Note also recent preliminary CDF result: [-0.62 +- 0.21 +- 0.10]% [CDF note 10784] )

  28. Selected physics highlights • Parameters of the CKM matrix • Studies of CPV in the Bs system • CP violation in charm • Rare B decays

  29. g, g, SM + New physics contributions FCNC decay B0 K*0m+m- See parallel talk of Konstantinos Petridis • LHCb BR = (1.22+0.38-0.32) x 10-6 agrees to within ~30% of SM • But forward-backward asymmetry AFB(q2) in the  rest-frame is a sensitive NP probe • LHCb has largest sample in world, as clean as the B Factories! 900 ± 34 events arXiv:1210.4492

  30. B0 K*m+m- continued • Previous results hinted at discrepancy • First measurement of zero crossing point: q2 = 4.9+1.1-1.3 GeV2 • AFB measured by LHCb consistent with Standard Model [arXiv:1101.0470] SM

  31. But not all is quite as expected … • Expected to be ~zero in SM • Significant deviation emerging (4.6s from zero). Requires further studies and better theoretical understanding • No similar effects seen in BK*m+m- • LHCb measure “isospin asymmetry” JHEP 7 (2012) 133

  32. B+ → π+μ+ μ–rare penguin decay • B+ → π+μ+ μ– First observation – (rarest B decay ever observed that has >5s significance) arXiv: 1210.2645 25±6 events 5.2 σ significance • SM prediction: (2.0 ± 0.2)x10−8 • BR measured (2.4±0.6±0.2) 10-8 PRD77 (2008) 014017

  33. Rare decay Bsm+m- See parallel talk of Serena Oggero • Decay strongly suppressed in SM • Predicted BR = (3.5 ± 0.3)  10-9 • Very sensitive to new physics- MSSM • But it’s a bit like looking for a needle in a haystack arXiv:1208:0934 & PRL 109 041801 (2012)

  34. LHCb m+m- mass spectrum LHCb-CONF-2012-025 B0s→m+m-? 5.4

  35. LHCb Bsm+m- candidate 35

  36. Bsm+m- limits prior to Nov 2012 • LHCb selection based on multivariate estimator (BDT) combining vertex and geometrical information • ATLAS/CMS/LHCb combined @95%CL • BR(Bs→ +-) < 4.2 10-9 • SM (Bs→ +-) = (3.5 ± 0.3)  10-9 • BR(Bd→ +-) < 8.1 10-10 LHCb 2011 limits (1 fb-1) Phys. Rev. Lett. 108 (2012) 231801

  37. Results based on 2011/12 data: 2.1 fb-1 : blinded analysis • The known B masses and widths are fixed in the fit • Cut on BDT>0.5 New 3.5 s LHCb-CONF-2012-043

  38. Constraints on new physics models Status in June 2012 (LCC combination) Status in November 2012 (LHCb only) Straub Moriond 2012 (http://phys.davidstraub.de/files/dstraub-moriond12.pdf)

  39. Summary and Outlook • LHCbis a huge success : the detector works spectacularly well • So far all in good agreement with the Standard Model → New physics is becoming constrained in the flavour sector → CP violation in charm may (or may not) be the first evidence of NP. • Up to 2017 we expect 7-8 fb-1 of data in total, and much of this at ~double the current heavy-flavour production cross-section (since √s: 8→14 TeV) • But still much room for new physics, higher precision required …

  40. See parallel talk of Stephan Eisenhardt Outlook: LHCb Upgrade • Main limitation that prevents exploiting higher luminosity is the Level-0 (hardware) trigger • To keep output rate < 1 MHz requires raising thresholds  hadronic yields reach plateau • Proposed upgrade is to remove hardware trigger: read out detector at 40 MHz (bunch crossing rate). Trigger fully in software in CPU farm. Requires replacing front-end electronics • Will allow to increase luminosity by factor ~ 10 to 1–2 × 1033 cm-2 s-1 • Framework TDR submitted to the LHCC: Physics case enthusiastically endorsed, detector R&D underway Upgrade of LHCb detector planned for 2019 to take at least 10× more data: 50 fb-1

  41. Upgrade sensitivities 50 fb-1 LHCb-PUB-2012-009

  42. Spare slides from here on

  43. Flavour tagging Tagging of production flavour (B or B) important for mixing and CP analyses.Performance calibrated using control channels such as B+→ J/y K+ Current opposite side tagging power: e (1-w)2 = (2.29 ± 0.06 ± 0.22)% LHCb-CONF-2012-026 Tagging variable

  44. The sign of DGs PRL 108 (2012) 241801 • To resolve ambiguity(fs, DGs , d , d)  (p-fs, -DGs , 2p-d , -d) study strong phase difference ds=ds -dbetween K+K- P-wave and S-wave amplitudes as a function of m(K+K-) around the f(1020) • P-wave: f(1020), going through resonance→ expect rapid positive phase shift • S-wave: non-resonant and tail from f0(980)→ expect no fast variation of phase • Analysis based on 0.37 fb-1 • Determine ds in four K+K- mass bins Solution corresponding to DGs> 0 preferred with 4.7s significance

  45. Charm CPV combination

  46. [LHCb-CONF-2012-007] preliminary Time-dependent CPV in B0(s) →h+h-

  47. CP violation in BKp and BsKp

  48. See parallel talk of Artur Ukleja talk Charm mixing

  49. Ks L PID calibration samples • Impressive calibration purity → samples allow PID calibrations in efficiency and purity to be evaluated with data D from D* f

  50. Away from flavour: W/Z production LHCb’s unique forward and low pT acceptance equips it to perform EW / QCD measurements which are highly complementary to those of mid-rapididty GPDs Studies of W/Z production [JHEP 6 (2012) 58] alongside ATLAS/CMS gives complete picture Unique kinematical acceptance ATLAS/ CMS LHCb

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