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First Results from LHCb

The XXth International Workshop High Energy physics and Quantum Field Theory. First Results from LHCb. 2 4 September – 01 October 2011, Sochi, Russia. Yu. Guz (IHEP Protvino), on behalf of the LHCb collaboration. LHCb detector Selected physics results LHCb upgrade issues Conclusions.

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First Results from LHCb

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  1. The XXth International Workshop High Energy physics and Quantum Field Theory First Results from LHCb 24September – 01 October 2011, Sochi, Russia Yu. Guz (IHEP Protvino),on behalf of the LHCb collaboration • LHCb detector • Selected physics results • LHCb upgrade issues • Conclusions

  2. LHC is a pp collider with ECM = 14 (or 7) TeV and luminosity up to 1034 cm-2s-1

  3. b b The LHCb experiment at LHC • LHCb is dedicated to study processes with heavy quarks (b, c): flavor oscillations , CP violation, rare decays etc. • Main physics objective: indirect search for New Physics phenomena, mainly in loop-mediated processes • can access much higher mass, not limited by √s • complementary to direct searches: provides information about magnitudes and phases of NP couplings b b • LHC is good as a B factory:the bb cross section σ(ppbbX) is large, ~300 μb • The bb production is sharply peaked forward-backward. • LHCb choice: a single arm detector 1.9<|η|<4.9σ(bb)~75 μb in the acceptance • to be selected out of ~60 mb of all visible pp interactions  very selective trigger is required! Yu. Guz QFTHEP-2011 First Results from LHCb

  4. The LHCb experiment at LHC • B hadron signature: particle(s) with high pT and displaced vertex. • Typical B hadron flight distance is ~ few mm. • To be able to reconstruct complex decay chain, it is important to have: • good (vertex) coordinate resolution; • magnet and tracking detectors for momentum measurement; • particle identification: • π/K/p separation in wide momentum range; • muon identification; • calorimetry: • for γ/π0 reconstruction; • electron identification; • trigger for high pT particle BD0X π+ IP D0K-π+ K- p p PV μ- B 1 cm K+ μ+ Yu. Guz QFTHEP-2011 First Results from LHCb

  5. The LHCb experiment at LHC Muon System RICH detectors Vertex Locator (VELO) • tracker stations (inner area: silicon; outer: straw tubes) • two RICH detectors • EM calorimeter with preshower • hadron calorimeter, to trigger high pT hadrons • muon identification system • Main components: • Vertex Locator (VeLo): a silicon strip detector surrounding the IP ‒ sensitive area starts at 8 mm from the beam! • warm magnet, ~4 Tm; reversible field polarity to cancel out possible biases in measurements Magnet Tracking System Calorimeters Yu. Guz QFTHEP-2011 First Results from LHCb

  6. Search for New Physics in CP violation and Rare Decays LHCb Collaboration: 55 institutesof15 countries, 755 participants

  7. Tracking system • Vertex detector (VeLo): primary vertex of pp interaction and B decay vertices with few μm accuracy; • tracking stations (silicon strip and straw tubes) upstream and downstream the magnet measure the momentum Accurate magnetic field map and good alignment are necessary prerequisites • PV resolution (for 25 tracks): ~16 μm in X&Y, ~76 μm in Z • IP resolution: ~13 μm in X, Y (~12 μm in MC) • effective mass resolution: as an example, ~15 MeV on J/ψμμ VeLo: two retractable halves, 21 station, Rφ silicon sensors Yu. Guz QFTHEP-2011 First Results from LHCb

  8. Particle ID • Muon ID • efficiency: 97.3±1.2% at p(μ)>4 GeV/c • misID πμ ≈ 2.4%, p  μ≈ 0.18% BR(ημμ)=5.8±0.8·10-6 Particle ID with RICH detectors • K ID efficiency ≈ 96%, πK misID ≈ 7% Yu. Guz QFTHEP-2011 First Results from LHCb

  9. Trigger 10 MHz 850 KHz 3 KHz Average event size ~35 kB Hardware Level-0 trigger followed by two-stage software High Level Trigger, HLT1 and HLT2 • L0 requires presence of a high pT object (h, μ, μμ, γ, e±) in CALO and Muon system • HLT1 performs partial reconstruction, confirms L0 objects: associates them with reconstructed tracks, especially with those displaced from the PV • HLT2: full reconstruction; uses reconstructed objects for exclusive selections with clear signature Depending on luminosity, the L0 and HLT thresholds can be tuned such that not to exceed maximal throughput of the systems. First data of 2010 with low LHC luminosity: loose trigger conditions, data suitable for production studies. Since summer 2010 – trigger optimized for B-physics Yu. Guz QFTHEP-2011 First Results from LHCb

  10. LHCb running in 2011 The luminosity is limited, in particular, by requirement from reconstruction of not too many visible pp interactions in one event (μ). LHC does luminosity leveling for LHCb by varying the bunch overlap Currently, at LHC energy of 2x3.5 TeV, LHCb is running at L≈ 3.5·1032 cm-2s-1 . With ~1400 bunches in LHC, this corresponds to μ≈1.3 (the original design parameters for 2x7 TeV running with ~2800 bunches were L≈ 2·1032 cm-2s-1 and μ≈0.4 ). Yu. Guz QFTHEP-2011 First Results from LHCb

  11. LHCb luminosity 2011 2010 1 fb-1 expected by the end of 2011, same (or more) in 2012 • LHCb is running smoothly since the LHC startup, no major hardware problems, the detector is >99% operational. Yu. Guz QFTHEP-2011 First Results from LHCb

  12. Selected physics results

  13. LHCb, 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 measurements LHCb-CONF-2011-027 Performed with 2010 data, 37 pb-1. PDG More precise than PDG values! Yu. Guz QFTHEP-2011 First Results from LHCb

  14. 1.638 ± 0.011 1.525 ± 0.009 1.525 ± 0.009 1.477 ± 0.046 1.391 ± 0.038 Lifetime measurements LHCb-CONF-2011-001 Performed with 2010 data, 37 pb-1. LHCb, ps PDG BsJ/ψ φ, t > 0.3 ps Yu. Guz QFTHEP-2011 First Results from LHCb

  15. bb production • The ppbb cross section was measured in two ways: • deduced from J/ψ-from-b production cross-section using the LEP average bJ/ψ branching fraction and extrapolating into 4π (see talk of K. Belous): • σ(ppbbX)=288± 4±48 μb • measured using b D0Xμ-ν (+cc) inclusive yields gives a compatible result: • σ(ppbbX)=284±20±49 μb • In this analysis the b decay candidates were selected as D0 (K-π+) and μ- having common vertex; the right sign combinations has significant nonzero impact parameter (IP) of D0 (K-π+), which is a signature of a true b decay. EPJ C71 (2011) 1645 PL B694 (2010) 209 all D0K-π+ candidates right sign (D0μ-) combination wrong sign (D0μ+) combination Yu. Guz QFTHEP-2011 First Results from LHCb

  16. B+ production LHCb-CONF-2011-033 The B+ production total and differential cross-section were measured in the LHCb acceptance in B+J/ψK+ : σ(B+, 2<y<4.5)=37.1±1.9(stat)±5.3(syst)μb B+ Yu. Guz QFTHEP-2011 First Results from LHCb

  17. b fragmentation, fs/fd Important input for absolute branching measurements, like Bsμμ. • Average obtained using independent measurements by LHCb: • ratio of yields of exclusive hadronic modes BsDs-(K+K-π-)π+ and BdD-(K+π-π-)π+: • fs/fd=0.256±0.014(stat)±0.019(syst)±0.026(theor); • ratio of BsDs-π+ to BdD-K+: • fs/fd=0.250±0.024(stat)±0.017(syst)±0.017(theor); • ratio of yields of inclusive semileptonic modes, D0Xμν, D-Xμν and DsXμν: • fs/fd=0.268±0.008(stat) (syst) • The combined result is: • fs/fd=0.267 LHCb-PAPER-2011-006 LHCb-CONF-2011-028 +0.022- 0.020 LHCb-CONF-2011-034 +0.021- 0.020 Yu. Guz QFTHEP-2011 First Results from LHCb

  18. flavor tagging LHCb-CONF-2011-003 Effective tagging efficiency: εeff=εtagD2=εtag(1-2ω)2, where: εtag – tagging efficiency ω – mis-tag fractionD – dilution factor Necessary for the B time-dependent studies! The flavor tagging was optimized on 2010 data using the B+J/ψK+, B0J/ψK*0 and B0D*-μ+νμ decays. Typically, εeff≈2% for OS taggers only, 2.8% for OS+SS combination; different but close numbers for other B decays; is carefully calibrated for each particular study. The algorithm is designed to provide a per-event estimate of the mis-tag probability. Yu. Guz QFTHEP-2011 First Results from LHCb

  19. Δms LHCb-CONF-2011-050 The Bs mixing frequency, Δms, measured on 341 pb-1 LHCb data in the decay BsD π+, with D K+K–π–, using all three KKπ modes: φπ, K*K and non-resonant KKπ. – s – s Average proper time resolution calibrated on prompt Ds: σt≈45 fs (cf ~350 fs oscillation period of Bs). Flavor tagger performance, εeff=εtag(1-2ω)2 :OST: (3.2±0.8)% ; SST: (1.3±0.4)% (preliminary) result: Δms = 17.725±0.041±0.026 ps-1. Earlier results: LHCb, 37 pb-1 : 17.63±0.11±0.03 ps-1; CDF (2006) : 17.77±0.10±0.07 ps-1.New WA: Δms = 17.731±0.045 ps-1. - world’s best measurement ! LHCb-CONF-2011-005 PRL97, 242003 (2006) Yu. Guz QFTHEP-2011 First Results from LHCb

  20. φs Search of New Physics effects in the Bs mixing. The mixing phase φs in SM is small and has little theoretical uncertainty: φs (SM) = -2arg[-(VtsVtb*)/(VcsVcb*)] = 0.0363  0.0016 Good sensitivity to New Physics effects. Via time-dependent analysis of Bs decay into CP eigenstates. The most suitable final states are J/ψφ, J/ψf0(980) : the decay amplitude is tree-dominated and not sensitive to NP. BR(BsJ/ψφ) · BR(J/ψμμ) · BR(φK+K-) ≈ 4·10-5 however with V+V final state both CP parities are present, angular analysis is necessary. BR(BsJ/ψf0(980)) · BR(J/ψμμ) · BR(f0π+π-) ≈ 0.8·10-5 , angular analysis is not needed. Yu. Guz QFTHEP-2011 First Results from LHCb

  21. φs from BsJ/ψφ LHCb-CONF-2011-049 Apart from 3 KK P-waves for φ, the KK S-wave is included. Total of 10 physics parameters: 3 independent magnitudes out of four (|A ┴|, |A║|, |A0|, |As|) at t=0; 3 relative phases (δ┴, δ║, δs) w.r.t. δ0; φs, Γs, ΔΓs, Δms (the latter was fixed to its LHCb measured value, 17.725±0.11 ps-1). A two-fold ambiguity is present: φs↔π-φs, ΔΓs↔-ΔΓs, δ║↔-δ║, δ┴↔π-δ┴. Unbinned maximum likelihood fit, the event variables being candidate mass, decay time, decay angles and initial flavor. Required accurate description of background, efficiencies, resolutions, flavor tagging. Yu. Guz QFTHEP-2011 First Results from LHCb

  22. φs from BsJ/ψφ 8276±94 LHCb-CONF-2011-049 Proper time resolution was calibrated on prompt J/ψ: σt~50 fs . The lifetime cut t>0.3 ps removes most of the background, resulting in total of 8276±94 signal events. Only OS flavor tagging used for the J/ψφ analysis, calibrated on J/ψK* : D=0.277±0.011±0.025, εtag = (2.08±0.41)% per-event mistag probabilities Yu. Guz QFTHEP-2011 First Results from LHCb

  23. φs from BsJ/ψφ LHCb-CONF-2011-049 δ║   [3.01, 3.36] @ 68% CL The systematic errors mainly come from uncertainties in the description of angular and decay time acceptance and background angular distribution. The 4% KK S-wave contribution. Goodness of fit was checked using the “point-to-point dissimilarity test” (arXiv:1006.3019). Yu. Guz QFTHEP-2011 First Results from LHCb

  24. φs from BsJ/ψφ LHCb-CONF-2011-049 SM To date, world’s most precise result: φs = 0.13 ± 0.18(stat) ±0.07(syst) Γs = 0.656 ± 0.009(stat) ±0.008(syst) ΔΓs = 0.123 ± 0.029(stat) ±0.008(syst) - first 4σ evidence of ΔΓs > 0 ! • Expectations for 2 fb-1 of 2011+2012 • φsstatistical uncertainty of ~0.07 – from simple scaling • further improvement of statistical uncertainty from including same side tagging • reduction of systematic errors from better understanding of acceptance and background Yu. Guz QFTHEP-2011 First Results from LHCb

  25. φs from BsJ/ψφ From http://lhcb-public.web.cern.ch/lhcb-public Yu. Guz QFTHEP-2011 First Results from LHCb

  26. φs from BsJ/ψ f0(980) LHCb-CONF-2011-051 The decay BsJ/ψf0(980) first observed by LHCb,CERN-PH-EP-2011-011 CL contours obtained using Γs from J/ψφ. CP-odd final state, cannot determine Γs and ΔΓs simultaneously. Using both Γs and ΔΓs from BsJ/ψφ: φs =-0.44±0.44(stat)±0.02(syst) When combining BsJ/ψφ and BsJ/ψf0(980): φs =-0.03 ± 0.16(stat) ±0.07(syst) LHCb-CONF-2011-056 Yu. Guz QFTHEP-2011 First Results from LHCb

  27. Bsφ φ Proceeds via bs FCNC penguin, possible New Physics contribution can be revealed e.g. through comparison of CPV phase with the one obtained from BsJ/ψφ +NP BR much lower than BsJ/ψ φ. As a first stage - measurement of time-integrated triple product asymmetry , U=sin(2Φ) , V=sin(±Φ), sign from cos(θ1)*cos(θ2) In SM both AU/V =0.Non-zero measurement means weak phase difference between CP even and odd eigenstates, clear sign of NP [M. Gronau and J. L. Rosner, arXiv:1107.1232] Yu. Guz QFTHEP-2011 First Results from LHCb

  28. Bsφ φ LHCb-CONF-2011-052 Studied with 340 pb-1 of data. Very clean mass peak. No flavour tagging needed for triple product asymmetry AU=-0.064±0.057±0.014 AV=-0.070±0.057±0.014 Consistent with zero Next step : time-dependent CP asymmetry measurements (needs more statistics) Yu. Guz QFTHEP-2011 First Results from LHCb

  29. direct CP asymmetry in Bd,sKπ LHCb-CONF-2011-042 Non-physical asymmetries Aδ were evaluated: Aδ(BdKπ) = -0.007±0.006 Aδ(BsKπ) = -0.010±0.002 +0.012 -0.011 Acp(Bd→Kπ) = -0.088±0.011(stat) ±0.008(syst)– World Average = -0.098 Acp(Bs→Kπ) = 0.27±0.08(stat) ±0.02(syst) - first evidence Yu. Guz QFTHEP-2011 First Results from LHCb

  30. Bs,dμμ see talk by Yu. Shcheglov May be significantly enhanced in models with S or P coupling; e.g. in MSSM BR(Bs.dμμ) ~ tan6β / MA4 ,  a good probe for New Physics! Very rare in SM (FCNC & helicity suppressed): BR(Bsμμ)SM=(3.2±0.2)·10-9; BR(Bdμμ)SM=(1.1±0.1)·10-10. A.J.Buras, arXiv:1012.1447 Previous measurements: D0: BR(Bsμμ) < 5.1·10-8 (95%) (6.1 fb-1) PL B693, 539 (2010) CDF: BR(Bsμμ) = (1.8 )·10-8 (hint !) (7 fb-1) arXiv:1107.2304 LHCb: BR(Bsμμ) < 5.6·10-8 (95%) (6.1 fb-1) PL B699, 330 (2011) Recent CMS measurement: BR(Bsμμ) < 1.9·10-8 (95%) (1.1 fb-1) arXiv:1107.5834 +1.1- 0.9 World best limits obtained by LHCb with 300 pb-1 of 2011 (+37 pb-1 of 2010) BR(Bsμμ) < 1.5 (1.2) ·10-8 at 95% (90%) CL BR(Bdμμ) < 5.2 (4.2) ·10-9 at 95% (90%) CL Yu. Guz QFTHEP-2011 First Results from LHCb

  31. Bsμμ see talk by Yu. Shcheglov Combined with recent CMS result: BR(Bsμμ) < 1.08 (0.90) ·10-8 at 95% (90%) CL LHCb-CONF-2011-047CMS PAS BPH-11-019 Prospects for LHCb taken from arXiv:1108.3018 Yu. Guz QFTHEP-2011 First Results from LHCb

  32. Other LHCb results • Physics results not covered here: • studies of radiative decays Bsφγ and BdK*γ. • FB asymmetries in BK*μμ; • CPV in charm, measurement of AΓ and ΔACP: results of 2010 available, 2011 expected soon • LFV search in BK(π)μμ; • CP asymmetry in B+DK+; • Bc production and decays; • b baryons; • and more … LHCb-CONF-2011-042 LHCb-CONF-2011-038 LHCb-CONF-2011-046 LHCb-CONF-2011-023 LHCb-PAPER-2011-009 LHCb-CONF-2011-023 Yu. Guz QFTHEP-2011 First Results from LHCb

  33. LHCb Upgrade

  34. LHCb long term plans LHCb Upgrade LoI: CERN-LHCC-2011-001 By 2017, LHCb is expected to take 5-10 fb-1 of data. There is strong physics motivation to continue the present programme. Next step is to collect other ~50 fb-1 probe / measure NP effects at % level. For this, LHCb should be able to run at higher luminosities: (1-2)·1033 @√s = 14 TeV. Upgrade is necessary Yu. Guz QFTHEP-2011 First Results from LHCb

  35. LHCb upgrade plan LHCb Upgrade LoI: CERN-LHCC-2011-001 • LHCb at higher luminosity • typical L0 efficiency for purely hadronic final states ~ 50% and will drop with luminosity. The acquisition rate for purely hadronic channels (like Bsφφ) does not increase with increasing luminosity! • apart from the trigger, the LHCb performance will not deteriorate significantly up to 1033 cm-2s-1 The only way out is to replace the present hardware L0 trigger by a flexible software one which is able to digest the full input bandwidth, up to 40 MHz. This implies replacement of almost all the frontend electronics. Yu. Guz QFTHEP-2011 First Results from LHCb

  36. LHCb upgrade plan LHCb Upgrade LoI: CERN-LHCC-2011-001 • Upgrade: • fl;exible software LLT • up to 40 MHz input • up to 20 kHz HLT output • run at 5 times higher luminosity • big gain for hadronic modes • Presently: • hardware L0 • software HLT1 with max 1 MHz input • HLT2 with up to 2 (3) kHz output • run now at 3.5 1032 cm-2s-1 @ √s=7 TeV Yu. Guz QFTHEP-2011 First Results from LHCb

  37. Detector issues • VELO: replace the whole detector (rad damage). New readout chips. Choice between strip and pixel options. • other tracking detectors: leave present OT straw tubes at the periphery. Middle part: the options are silicon strips or scintillating fibers. • RICHes: replace all the photodetectors, as present HPDs include readout electronics. MAPMTs is baseline. Remove aerogel in RICH1 (material budget). • additional PID detector: Time of Internally Reflected Cherenkov Light (TORCH). Quartz plate radiator, 10-15 ps resolution. Installed between RICH2 and calorimeters. • MUON: present frontend electronics can be kept and read out at 40 MHz. remove the M1 station before calorimeters. • CALO: reduce PMT gain. Possible replace few modules in hottest areas. Removing part of the preshower is discussed. Yu. Guz QFTHEP-2011 First Results from LHCb

  38. Conclusions • LHCb is running successfully at its design luminosity (and beyond!), demonstrating very good detector performance, and collected by now ~800 pb-1 of physics data • already now, LHCb obtained physics results competitive with B-factories and Tevatron experiments: • most precise direct CP violation measurements in Bd,sKπ • most precise measurement of Δms, • most precise measurement of φs and ΔΓs in Bs J/ψφ, J/ψf0(980), • best upper limits on rare decay Bsμμ • by now, no significant deviation from SM observed, in particular the hints observed by Tevatron in Bsμμ and φs not confirmed • 1 fb-1 expected by the end 2011, more in 2012. Many important physics results expected! • high luminosity upgrade is foreseen. Yu. Guz QFTHEP-2011 First Results from LHCb

  39. Thank you!

  40. Backup

  41. Luminosity measurement in 2010 In 2010, luminosity will be estimated from beam properties N – number of bunches f – collision frequency n1i, n2i -- # of protons in bunches σXi, σYi – transverse bunch sizes LHCb preliminary 2009, ECM=0.9 TeV Determined with ~15% accuracy in 2009 (dominated by the bunch current measurement uncertainty). In 2010 5-10% precision is expected. Yu. Guz QFTHEP-2011 First Results from LHCb

  42. Lepton flavor violation Looking for DL=2 processes B+→K-μ+μ+and B+→μ+μ+ (allowed in NP models with a Majorana neutrino) LHCB-PAPER-2011-009 No signal observed in 36 pb-1 Improved present best limits by a factor of 40 (30). Publication in preparation. Yu. Guz QFTHEP-2011 First Results from LHCb

  43. Bsφγ Dominating SM quark level diagram has left handed photons An example MSSM diagram with right-handed photons Experimental probe: AD (or effective lifetime) [F. Muheim, Y. Xie, R. Zwicky, PLB 664:174, 2008] AD sensitive to fraction of right-handed photons (even for small fs) AD ~ 0 in SM, can be enhanced by NP with large RH currents. Yu. Guz QFTHEP-2011 First Results from LHCb

  44. Bsφγ First step: measure BR. LHCb-CONF-2011-055 Bs→ fg Bd→ K*g Next step: measure AD (or effective lifetime) Yu. Guz QFTHEP-2011 First Results from LHCb

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