1 / 36

LHCb results

LHCb Collaboration: 755 M embers, from 55 Institutes in 15 Countries. LHCb results. Evgeny Gushchin (INR RAS) for the LHCb collaboration. Outline. Introduction LHC as B-factory LHCb is B-meson experiment for search NP in CPV and rare decays Experimental technique and key performances

mabli
Télécharger la présentation

LHCb results

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. LHCb Collaboration: 755 Members, from 55 Institutes in 15 Countries LHCb results Evgeny Gushchin (INR RAS) for the LHCb collaboration

  2. Outline • Introduction • LHC as B-factory • LHCb is B-meson experiment for search NP in CPV and rare decays • Experimental technique and key performances • Physics program and selected Results • Conclusion XV Lomonosov conference, Moscow

  3. Search for New Physics beyond SM at LHC Search for new particles with observable masses produced directly in pp collisions AND/OR i.e. Higgs, Supersymmetry As virtual contribution of new heavy particles i.e. to loop and box diagrams in FCNC :i.e. it can change values, phases and/or Lorentz structure of couplings. • measurable as deviation from SM precise prediction for heavy quark processes, i.e. for B,D mesons: • in rare decays • in CP violation phase (mixing and decay) • Very good detector: • Selective/efficient trigger • PID • Excellent mass and time resolution • Very good statistics: • Very large bb-production LHCb @ LHC!!! XV Lomonosov conference, Moscow

  4. LHC as B - factory • Very high luminosity – 2.4*1033(nominal-1034)cm-2sec-1 • High production cross-section (@3.5TeV): • ~300µb ( pp  bb X) and ~6.1mb ( pp  cc X) • But also ~65 mb for minimum-bias • Annual yield (in LHCb) – > 1011BB-pair and 20xDD. Tevatron: instant luminosity reached ~4*1032/cm2/s and total L~11/fb. Cross-sections bb is 3 times lower than at LHC. In LHCb: ~1 of 200 collisions with b-quark ! ~1 of 10 - with c-quark ! All b-species: B+ : B0 : B0s : Λ0b : Bc 40%:40%:10%:10%:0.1% To reduce L0 rate > 10 MHz to 2-3 kHz VERY selective trigger is necessary! Trigger on low pT tracks with efficient PID B-pairs are produced mainly in forward and backward directions: Single-arm spectrometer covering ~4% of open angle has ~40% acceptance. XV Lomonosov conference, Moscow

  5. LHCb detector LHCb is forward spectrometer optimized for studies of CPV and B-meson rare decays LHCb key performances: Vertex/proper time resolution : VELO PID: RICH, Calorimeter, Muon system Mass resolution: Tracker ~4Tm p-p interaction point XV Lomonosov conference, Moscow

  6. LHCb detector and trigger efficiency HARDWARE PT PT PT SOFTWARE Detector subsystems are ~99% efficient! Trigger has very high selection efficiency! Muon trigger (J/) eff ~ 95% Hadron trigger (D0) eff ~ 60% XV Lomonosov conference, Moscow

  7. 1.638 ± 0.011 1.525 ± 0.009 1.525 ± 0.009 1.477 ± 0.046 1.391 ± 0.038 Vertex / Time resolution LHCb lifetime measurements using 36 pb-1 of 2010 data – world class! Both statistical and systematical errors are expected to be significantly improved with 2011 data! LHCb-CONF-2011-001 [ps] PDG [ps] Vertex Locator (VELO) provides excellent proper time resolution of ~50 fs XV Lomonosov conference, Moscow

  8. LHCb-CONF-2011-027: masses [MeV/c2] 5279.17 ± 0.29 5279.50 ± 0.30 5279.50 ± 0.30 5366.30 ± 0.60 5620.2 ± 1.6 6277 ± 6 Mass resolution Mass resolution is based on precise momentum measurement with LHCb magnet and tracker: Δp/p<0.5% up to 100 GeV/c With 2010 data! PDG [MeV/c2] World-best mass measurements! 11151±115 events =10.50±0.10 MeV/c2 816±30 events  = 6.96±0.25 MeV/c2 Bu+ J/ψ K+ Bs0 J/ψ φ 2010 L=35 pb-1 2010 L=35 pb-1 XV Lomonosov conference, Moscow

  9. Particle Identification photon/electron/hadron PID – SPD/PRS/ECAL/HCAL Muon PID – Muon system Hadron PID – RICH1 and RICH2 X 0 (no conversions) E= 7.2 MeV/c2 RICH PID absolutely necessary to identify charged hadrons in B  hh XV Lomonosov conference, Moscow

  10. LHCb operation LHCb collected ~37 pb-1 in 2010 and already ~ 700 pb-1 recorded in 2011 By end of 2011 LHCb hopes to collect 1 fb-1 • LHC reached nominal peak luminosity of 2.4*1033 cm-2s-1 with number of bunches is ~1300 from ~2600. • LHCb recording >1pb-1/hour running at • L~3.5*1032 cm-2sec-1 in auto-leveling mode • GPD luminosity is  4 times higher than LHCb LHC performs well! ~30 pb-1 for LHCb in 29 h in single fill ! dL/dt ~ 100 pb-1/week ! LHCb luminosity auto-leveling • Visual average number of vertexes per BX now is ~3 times larger than nominal µ =0.4 (in 2010 ~6 larger) • 1 PV gives ~30 tracks/rapidity unit • Higher µ means higher track multiplicity, that is dangerous for reconstruction 2010 2011 nominal µ =0.4 nominal µ =0.4 XV Lomonosov conference, Moscow

  11. LHCb physics program and key measurements LHCb is optimized for study of CP-violation and rare decays in B-mesons. LHCb physics program includes measurements: • CP-violation in B+,B0,Bs • Prospects for -angle measurement • Tree-level processes (B  DX), • Loop processes (charmless B decays) • Direct CP-violation (B  K) • Mixing induced CPV ( s) • Rare decays &NP • Bd → K*µµ • Bs → µµ • … • Quarkonia studies • Physics with charm • Soft QCD • Electroweak physics (W,Z) More studies are presented today in LHCb talks by Vladislav Balagura, Pavel Krokovny and Dasha Savrina Highlights in this talk      XV Lomonosov conference, Moscow

  12. -angle measurements • CKM – matrix is measured very precisely. • Great jobs done by B-factories and others. • Less constrained -angle : • combinated “trees” & “loops”:  = (67±4)° • from “trees” only:  = (73+22-25)° • Prospects for -measurementswith “trees”: • (based on Gronau-London-Wyler & Atwood-Dunietz-Soni methods • + time-dependent + Dalitz-plot analysis ) • To combine Bs Ds±K±, B0 DK*0 and B±DK± • ()~5° with 2 fb-1 • BsDs-K+ (Ds+K-) decays • under study, time-dependent analysis (Acp   - M) • M– Bs mixing phase well constrained in Bs→Ј/ψФ • - at first step ∆ms measurement using BsDs • B±DK± decays using common mode for D0&D0  K+- • Modemore suppressed for D0 and favored for D0 • maximizes interference: D0  K+- (DCS) and D0 K+- (CF) • But total branching very small (~10-7) • Preliminary: evidence for suppressed ADS mode at 4.0 with 343 pb-1. • Ratio to favored mode: “trees” PLB270,75(1991); PRL78,3257(1997) World-class measurement! World average (without LHCb): 1.6 ± 0.3 -0.58 ± 0.21 XV Lomonosov conference, Moscow

  13. Measurement of ∆ms World-class measurement! • ∆ms – mixing frequency in Bs • Used ~1381 B0s decays from 2010 data: • Combining the 4 decays allows suppress decay-specific features • To be used in time-dependent CPV studies Likelihood scan for ∆ms LHCb-CONF-2011-005, CERN-PAPER-2011-010 World average: ∆ms = 17.77 ± 0.10 ± 0.07 ps-1 XV Lomonosov conference, Moscow

  14. Direct CP asymmetry measurement in B0d,s→K LHCb with L=320pb-1 of 2011 data already has done: B0→K - the most precise single measurement and first 5σ observation at hadron machine! B0s→K - the first evidence of CP-violation in Bs decay! Raw asymmetry (has to be corrected for detector and production asymmetry) LHCb-CONF-2011-042 Acp(B0→Kπ) = -0.088±0.011(stat) ±0.008(syst) To be compared with world average: -0.098+0.012-0.011 Acp(Bs→Kπ) = 0.27±0.08(stat) ±0.02(syst) First LHCb result (with 37pb-1 data of 2010) LHCb-CONF-2011-011 Acp(B0→K+π־)= -0.074±0.033(stat) ±0.008(syst) Acp(B0s→K־π+)= -0.15±0.19(stat) ±0.02(syst) HFAG: Acp(B0→K+π־)= -0.098+0.012-0.011 CDF: Acp(B0s→K־π+)= 0.39±0.15(stat) ±0.08(syst) XV Lomonosov conference, Moscow

  15. LHCb result on fs/fd Very important for absolute branching measurements like Bs The ratio of fragmentation fractions fs/fd is measured by LHCb: • In hadronic decays, via relative abundance of B0s→D־s+ to B0→D־K+ and B0→D־+ LHCb-PAPER-2011-006, submit. To PRL • In semileptonic decays LHCb-CONF-2011-028 • And combined result LHCb-CONF-2011-034 XV Lomonosov conference, Moscow

  16. Quarkonium studies LHCb quarkonium physics program is rich and promising: • Heavy quarkonium states • give impact to theory (NRQCD..) • exotic states: molecular type state, tetraquark (?) • + Related production studies – test QCD models in forward region • Highlights : X(3872), X(4140), χc, χb • New exciting results are expected in future: • (2S) and (3S) production • J/ polarization (pT,y) • X(3872) quantum numbers and precise mass • Z±(4430) confirmation and Zb existence • New states? See also Vladislav’s talk today XV Lomonosov conference, Moscow

  17. Production studies at LHCb Many new results for flavour production were obtained with 2010 data: • pp  b b X • pp  J/ X • pp  F X W,Z • (1S) Bc+ • c • pp  J/ J/ X Test QCD model (tetraquark?) LHCb-PAPER-2011-007 LHCb-CONF-2011-012 LHCb-CONF-2011-016 LHCb-CONF-2011-017 Test QCD model in Forward region LHCb-CONF-2011-020 LHCb-PAPER-2011-013 first observation in p-p collisions XV Lomonosov conference, Moscow

  18. Mass measurement X(3872) (LHCb-CONF-2011-021) 2010 data MX(3872) = 3871.96 ± 0.46(stat) ± 0.10 (syst) MeV/c2 X(3872) production cross-section (LHCb-CONF-2011-043) To test molecular state mass precision has to be <0.1 MeV/c2 – in prompt. Quantum numbers have to be identified in B-decays. Search for X(4140) CDF observed a 5σ peak in the B+→J/ψ φ K+ channel. Candidate for exotic bounds state CDF arXiv:1101.6058 Preliminary (LHCb-CONF-2011-045) LHCb does not confirm presence of X(4140) LHCb with 376 pb-1: 364 ± 20 of B+→J/ψ φ K+ sample after φ –mass cut. ~3.2 times more than CDF with 6fb-1. Fit (LHCb): 7 ± 5 events Scaled from CDF data : 39 ± 9 ± 6 events X(3872) J/ +- Unknown quantum numbers. Not excluded conventional charmonium state c2(1D), but predicted mass is far bellow. Can be exotic state: molecular 1++ (D*D0 most popular) or tetraquark. XV Lomonosov conference, Moscow

  19. Production of χcJ/  • P-wave charmonium state • ECAL only detection of photons: with/without conversion • States separation is done by fit of mass-spectrum with both states χc1χc2 • 209k χc with 35.6 pb-1 (2010) LHCb-CONF-2011-020 Test NRQCD: colour singlet + colour octet Discrepancy at low pT Observation of b (1S)  • In order to interpret measurements of the  production and polarization the feeddown from higher bottomonium states has to beunderstood. • According to Pythia MC, ~ 40% of (1S) come from ­ b. • A clear signal for b production is seen. • The photon is reconstructed only with the calorimeter info. • Can not do a separation of the states yet. XV Lomonosov conference, Moscow

  20. CP-violation phase in Bs-mixing: Bs→Ј/ψФ • Dominant contribution – tree-level diagram • Contribution from “penguin” is small (10-3 – 10-4) • Interference between direct decay and decay via mixing gives CPV phase: s= M -2D • In Standard Model s  2 s = -2arg(VtsVtb*/VcsVcb*)  - 0.0363 ± 0.0017 rad • Search for New Physics in mixing: s= sSM+sNP See also Pavel’s talk today Expecting world best measurements s, Δms soon! Year 2011: Year 2010: Nsig=836 ± 60 LHCb-CONF-2011-006: data from 2010 L=36 pb-1 Standard Model value, probability = 22%(1.2σ) Results for 2011 data with much larger statistics are coming very soon -> expecting world best measurement of s! “Toy” Monte-Carlo using 2010 data as distribution function, but for 10xlarger statistics XV Lomonosov conference, Moscow

  21. Other channels relevant for s measurement “Penguin” diagram dominated can help to control penguin effect in Bs→Ј/ψФfor s extraction: • Bs→ФФ • Bs→K*K* - The first observation ! Can help to extractsand  • Bs→Ј/ψK* • Bs→K+K־- Most precise lifetime measurement ! Box diagram dominated can be used fors measurement: • Bs→Ј/ψf0(980) - The first observation !CP-odd eigenstate • Bs→Ј/ψf2’(1525) -The first observation ! LHCb-CONF-2011-019 LHCb-CONF-2011-025 LHCb-CONF-2011-018 Phys. Lett. B 698 (2011) 115 LHCb-CONF-2011-035 XV Lomonosov conference, Moscow

  22. Search for NP in rare decays:Bd → K*µµ See also Dasha’s talk today • The most known observable sensitive to NP is AFB • Current status: no evidence of zero-crossing point AFB(q2) predicted in SM • LHCb can reach precision for ZCP Δq2 < 0.5 GeV2 at 2 fb-1 LHCb with 309 pb-1achieved (preliminary) the most precise measurement to date LHCb-CONF-2011-038 Results are consistent with SM prediction for forward-backward asymmetry AFB, longitudinal polarization FL and differential brunching fraction dBF/dq2: Statistical errors are dominated now and will be improved with more data. Systematical error is also expected to be improved with more statistics. BaBar [PRD 79 (2009)], Belle [PRL 103 (2009)], CDF [PRL 106 (2011)] XV Lomonosov conference, Moscow

  23. Prospect:Bs,d → µµ Golden mode: Bs,d → µµ With ~300 pb-1 of LHCb data at SM level after selection: ~3.2 Bs → µµ and ~0.32 Bd → µµ events • Ultra rare decays (FCNC and helicity suppressed) • SM predicts (via box and penguin diagrams): BR(Bs → µµ) = (3.2 ± 0.2) · 10 -9 BR(Bd → µµ) = (1.1 ± 0.1) · 10 -10 CDF reported the observation: BR(Bs → µµ) = (1.8 +1.1-0.9) · 10 -8 arxiv: 1107.2304 Prospect on the base of 37 pb-1 (2010): • ~2 fb-1 will reach exclusion at SM level • Observation will need more statistics • LHCb presents preliminary result with 300 pb-1 • LHCb-CONF-2011-037: • BR(Bs0→ µµ) = 1.3 (1.6) · 10 -8 at 90%(95%)C.L. • BR(B0→ µµ) = 4.2 (5.2) · 10 -9 at 90%(95%)C.L. • Combining with preliminary result with 37 pb-1 • PLB 699(2011) 330,[hep-ex/1103.2165] • BR(Bs0→ µµ) = 1.2 (1.5) · 10 -8 at 90%(95%)C.L. • Combining with CMS observation • LHCb-CONF-2011-047: • BR(Bs0→ µµ) = 0.9 (1.1) · 10 -8 at 90%(95%)C.L. • Excess seen by CDF is not confirmed! Most-precise measurement! ~1 fb-1 allows a considerable constrain on MSSM XV Lomonosov conference, Moscow

  24. Conclusion • In 2010-2011 LHCb collected more than 700 pb-1 of rich data demonstrating: • Very good performance of trigger and data taking • Ability to work efficiently in hadronic environment • Ability to work with much larger luminosity than nominal (2 L -instant luminosity and 6 - PV av. number)! • With 2010 data LHCb already has got competitive results with B-factories and Tevatron • LHCb provided many world-class measurements: • First observations of many B-decay modes • Production of heavy flavour quarks and quarkonium states • World-best single measurement of direct CPV in B0s→K • World-class measurements of CPV phase s, ∆ms • Most precise measurements of rare decays Bd → K*µµ, Bs → µµ • Expecting ~1 fb-1 of data this year and many most-precise measurements very soon! • LHCb searches for New Physics with unprecedented precision! XV Lomonosov conference, Moscow

  25. Thank You! XV Lomonosov conference, Moscow

  26. BACK-UP XV Lomonosov conference, Moscow

  27. LHCb prospects for upgrade LHCb sensitivities for key observables CERN-LHCC-2011-001 XV Lomonosov conference, Moscow

  28. First observations of B-decays in LHCb • Bs  DK* LHCb-CONF-2011-008 • B  DK CS-mode, can be used for -measurements LHCb-CONF-2011-024 • B  (2s) LHCb-CONF-2011-014 – mixing CP • Bs J/K* penguin-suppressed LHCb-CONF-2011-025 • Bs K*barK* time-dependent CP LHCb-CONF-2011-019 • PLB 698(2011)14 • Bs J/ f0(980) mixing phasePLB 698(2011)115 • Bs J/ f2’(1525) mixing phase LHCb-CONF-2011-035 • Bc J/  first observation LHCb-CONF-2011-040 XV Lomonosov conference, Moscow

  29. Search for NP effects in Bd → K*µµ • In SM via FCNC (box and penguin diagrams) • Helicity structure is sensitive to right-handed and new scalar operators • The most known observable sensitive to NP is AFB • Current status: no evidence of zero-crossing point AFB(q2) predicted in SM • LHCb can reach precision for ZCP Δq2 < 0.5 GeV2 at 2 fb-1 XV Lomonosov conference, Moscow

  30. LHCb analysis and results Bd → K*µµ Analysis strategy: Events selection using Boosted Decision Tree (composition of topological and kinematical observables) Correction for non-uniformity of reconstruction and selection MC check with control channels Validation using Bd→Ј/ψK* Fit the angular observables LHCb with 309 pb-1achieved (preliminary) the most precise measurement to date BaBar [PRD 79 (2009)], Belle [PRL 103 (2009)], CDF [PRL 106 (2011)] Results are consistent with SM prediction for forward-backward asymmetry AFB, longitudinal polarization FL and differential brunching fraction dBF/dq2: Statistical errors are dominated now and will improved with more data. Systematical error is also expected to be improved with more statistics. XV Lomonosov conference, Moscow

  31. CP-violation in Bs mixing: Bs→Ј/ψФ See also Pavel’s talk today • Dominant contribution – tree-level diagram • Contribution from “penguin” is small (10-3 – 10-4) • Interference between direct decay and decay via mixing gives CPV phase: s= M -2D • In Standard Model s  2 s = -2arg(VtsVtb*/VcsVcb*)  - 0.0363 ± 0.0017 rad • Search New Physics in mixing: s= sSM+sNP • LHCb relevant results: • LHCb-CONF-2011-001: • Lifetime measurements of b →Ј/ψX • LHCb-CONF-2011-005: from Bs→Ds • Δms = 17.63 ± 0.11(stat) ± 0.04(syst) • Flavour tagging studies: • LHCb-CONF-2011-002: • Bs→Ј/ψФ: • Γs = (0.680 ± 0.034stat ± 0.027syst) ps-1 • ΔΓs = (0.084 ± 0.112stat ± 0.021syst) ps-1 • LHCb-CONF-2011-003: • Tagging efficiency measurements • LHCb-CONF-2011-004: • Time dependent analysis B0→Ј/ψKs DecayD MixingM • Strategy to measure s : • Trigger and select Bs→Ј/ψФ events • measure proper time • Measure transversity angles of final decay products to disentangle CP -odd and –even states • Tag initial flavor • Fit s with other unknown parameters XV Lomonosov conference, Moscow

  32. Expecting world best measurements s, Δms soon! CP-violation phase results: Bs→Ј/ψФ LHCb-CONF-2011-006: data from 2010 L=36 pb-1 Year 2011: Year 2010: Nsig=836 ± 60 Standard Model value, probability = 22%(1.2σ) Results for 2011 data with much larger statistics are coming very soon -> expecting world best measurement of s! “Toy” Monte-Carlo using 2010 data as distribution function, but for 10xlarger statistics XV Lomonosov conference, Moscow

  33. Rare decays: Bs,d → µµ • Ultra rare decays (FCNC and helicity suppressed) • SM predicts (via box and penguin diagrams): BR(Bs → µµ) = (3.2 ± 0.2) · 10 -9 BR(Bd → µµ) = (1.1 ± 0.1) · 10 -10 With ~300 pb-1 of LHCb data at SM level after selection: ~3.2 Bs → µµ and ~0.32 Bd → µµ events CDF reported the observation: BR(Bs → µµ) = (1.8 +1.1-0.9) · 10 -8 arxiv: 1107.2304 • LHCb presents preliminary result with 300 pb-1 • LHCb-CONF-2011-037: • BR(Bs0→ µµ) = 1.3 (1.6) · 10 -8 at 90%(95%)C.L. • BR(B0→ µµ) = 4.2 (5.2) · 10 -9 at 90%(95%)C.L. • Combining with preliminary result with 37 pb-1 • PLB 699(2011) 330,[hep-ex/1103.2165] • BR(Bs0→ µµ) = 1.2 (1.5) · 10 -8 at 90%(95%)C.L. • Combining with CMS observation • LHCb-CONF-2011-047: • BR(Bs0→ µµ) = 0.9 (1.1) · 10 -8 at 90%(95%)C.L. • Excess seen by CDF is not confirmed XV Lomonosov conference, Moscow

  34. Prospect: Bs,d → µµ Prospect on the base of 37 pb-1 (2010): ~2 fb-1 will reach exclusion at SM level Observation will need more statistics ~1 fb-1 allows a considerable constrain on MSSM XV Lomonosov conference, Moscow

  35. Other channels relevant for s • “Penguin” diagram dominated: Bs→ФФBs→K*K* Bs→Ј/ψK* Bs→K+K־ LHCb-CONF-2011-018 Most precise lifetime measurement of Bs→K+K־ Can be used to put constrains ons and ΔΓs LHCb-CONF-2011-019 The first observation of Bs→K*K* Can help to extractsand  LHCb-CONF-2011-025 Assuming all events are from K*→K for mass |M(K)-M(K*)|<150 MeV Can help to control penguin effect in Bs→Ј/ψФfor s extraction XV Lomonosov conference, Moscow

  36. Other channels sensitive for s • Box diagram dominated: Bs→Ј/ψf0(980) Bs→Ј/ψf2’(1525) CP odd eigenstate Phys. Lett. B 698 (2011) 115 The first observation of Bs→Ј/ψf0(980) Statistics of 2010 ~34 pb-1 LHCb-CONF-2011-035 Can be used fors measurement The first observation of Bs→Ј/ψf2’(1525) Statistics of 2010 ~34 pb-1+ 125 pb-1 of 2011 XV Lomonosov conference, Moscow

More Related