Status and Results from the LHCb Experiment

1. Status and Results from the LHCb Experiment Zhenwei YANG @Tsinghua Univ. on behalf of the LHCb collaboration OCPA7 August 1-5, 2011 , Kaohsiung, Taiwan

2. Outline • Introduction to LHCb and its Performance • Selected Results on Heavy Flavor Physics:onia, exotics, Bc • Rare decay: Bs • Summary

3. ➢ Integrated Lumi ~ 37.7 pb-1 (End of 2010) ➢ Integrated Lumi ~ 488 pb-1 (by 30 July, 2011) Geneva CERN LHC Tunnel

4. 730 members 54 institutes 15 countries

5. Physics Aims of LHCb “dedicated to heavy flavour physics at the LHC” • New PhysicsCP violation: precise measurements of CKM anglesrare decays of beauty and charm hadrons • Heavy Flavour PhysicsOnia productionsB productionBc , b-baryon physicscharm decays (e.g. D-mixing)tau lepton flavour violation......

6. bb production at LHC • bb pair production correlated • σbb ~ 300-500 µb (@7-14 TeV) • 15<<300 mrad, unique acceptance • Average design Luminosity ~ 21032 cm-2s-1 • 2 fb-1 per nominal year (107 s), ~ 1012 bb pairs per year 

7. LHCbDetector RICH1 & RICH2 Excellent PID of K- Calorimeters e, , 0 beam 1 beam 2 VELO high position resolution σx/y ~ 10 μm σz ~ 60 μm Tracking System good tracking efficiency & momentum resolution Muon System good muon-ID

8. LHCb Trigger 40 MHz L0 m L0 had L0 e, g Level -0 1 MHz Impact Parameter Lifetime cuts HLT1 High-Level Trigger 30 kHz Global reconstruction HLT2 Inclusive selections m, m+track, mm Exclusive selections 2 kHz • L0 Hardware Trigger 40 MHz  1 MHz • Search for high pT , m, e, g, hadron candidates • High Level Software Trigger Farm • HLT1: Add Impact parameter cuts • HLT2: Global event reconstruction • Physics output rate 2 kHz – 2.5 kHz • HLT needs operational flexibility • Trigger Configuration Key (TCK) to distribute the configuration to 1000 nodes simultaneously when optimizing parameters during LHC fill • Luminosity following also in extreme conditions during 2010 run

9. LHCb Data Taking of 2011 • LHCb collected so far ~490 pb-1 in 2011 ( 37 pb-1 in 2010) • Analyses shown here use up to ~ 376 pb-1 ~488 pb-1 by 30 July • Luminosity levelling delivers ~ constant operation at 3-3.51032 cm-2s-1 • much lower than design luminosity of the machine

10. Onia and Exotics Understanding of production mechanism: Color Singlet Model, Color Octet Model, Evaporation Model? J/, (2S), c, (1S), (2S), (3S), b X(3872), X(4140), … cross section polarization to be measured mass and/or JPC

11. J/ production cross-section Euro. J. Phys. C71 (2011) 1645 L=5.2 pb-1 Agree with theo. Models well Large uncertainty due to unkown polarization. Polarization as function of pt and y will be measure soon.

12. (2S) production cross-section LHCb-CONF-2011-026 prompt (2S) + that from b Agree with theo. Models well Source separation will made as treated for J/. L=34.9 pb-1

13. c2/c1 production cross-section ratio LHCb-CONF-2011-020 • Radiative decay ccJ/y(mm) g • Challenge: to resolve cc1 and cc2 L=35.6 pb-1 DM = M (J/yg) - M(J/y) First results do not agree well with NLO NRQCD predictions in mid-pT range.

14. Observation of b • Clear cb signal, and LHCb will measure the prodcution cross-section. L~37 pb-1 Ns=35059 • Production and polarization measurement of  needs information on feeddown from higher bottonium states • ~ 40% of (1S) come from cb according to our pythia MC • Separation of differentcb states is not availabe • The phton is reconstructed only with CALO information

15. X(3872) measurements • First discovered by Belle in 2003, but nature remains uncertain • Mass and production x-section measured with first data • Using 2011 data, it’s possible 1) to perform very precise mass measurements 2) to learn about JPC by angular-analyses in B->X(3872)K • (2S) used as calibration channel MX(3872) = 3871.960.460.10 MeV/c2 LHCb-CONF-2011-021 X(3872)BR(X(3872)J/+-) = 4.74  1.10  1.01 nb L~35 pb-1 LHCb-CONF-2011-043 Systematics mainly come from tracking efficiency & decay width.

16. Search for X(4140) CDF arxiv: 1101.6058v1 ~ 6 fb-1 • CDF reported observation of X(4140) in the m(J/K+K-)-m(J/) spectrum in B+J/  K+ events (115 in 6 fb-1). • LHCb has now ~360 clean B+ signals of this channel in ~0.4 fb-1. Ns=196 LHCb Preliminary 376 pb-1 Clean signal B+J/  K+ LHCb preliminary 376 pb-1 expected signal scaled from CDF: 39  9  6 Fit: 7  5 events LHCb-CONF-2011-045 Background model is 3-body phase space convolved with resolution LHCb does not confirm presence of X(4140).

17. Bc production cross-section Bc: unique meson with two open heavy flavors L~32 pb-1 LHCb-CONF-2011-017 • for pT(B) > 4 GeV/c and (2.5,4.5)

18. Observation of BcJ/ • Only Bc J/ and BcJ/ν were ever observed. • BcJ/ first observed at LHCb! Measure relative Br w.r.t. Bc J/

19. Rare Decay: Bsm+m- • FCNC and helicity suppressed decay • Precise SM prediction:BR(Bs+-) = (3.2  0.2)  10-9 (A.J. Buras: arXiv: 1012.1447) • BR sensitive to New Physics, e.g. strongly enhanced by MSSM • Recent exciting hint from CDF ( 7 fb-1 ):

20. LHCb preliminary limit on Bsm+m- Compute limits using frequentist CLs method and LHCb combined result for fs/fd L~300 pb-1 bkgd only bkgd & signal at SM BR LHCb-CONF-2011-037 P-value of bkgrd only hypothesis: 14%

21. Preliminary combination of BR(Bsm+m- ) limit(CMS&LHCb) LHCb value of fs/fd as common input Observed limit at 95% (90%) : 1.1 (0.9)  10-8 ~ 3.4 times the SM expected value

22. Summary • LHCb has provided rich and promising results in heavy flavour sector • Production cross-sections of J/, (2S), (1S),c, b,… at s=7 TeV have been measured • Studies of exotics have started, X(3872), X(4140),… • Bc physics just began, new channel first observed • Limit on Br(Bsμμ), combined with CMS, still favor SM • Lots of new analyses are being done

23. back up

24. Measurement of J/ cross section • good approximation of average b lifetime • well described by exponential distribution (for J/ from b)

25. Upsilon (1S), (2S), (3S)

26. Upsilon production