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LHCb results

PLANCK‘2011,   May-June 2011, Lisboa. LHCb results. Hugo Ruiz On behalf of the LHCb Collaboration. Institut de Ciències del Cosmos. The LHCb physics scope. ATLAS, CMS: direct search LHCb: look for effect of new massive particles in lower energy observables

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LHCb results

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  1. PLANCK‘2011,   May-June 2011, Lisboa LHCb results Hugo Ruiz On behalf of the LHCb Collaboration Institut de Ciències del Cosmos

  2. The LHCb physics scope • ATLAS, CMS: direct search • LHCb: look for effect of new massive particles in lower energy observables • Many low energy constraints  NP will probably show up in loop processes • New particles can distort the SM (CKM) picture of B decays by modifying: • Phases  CP violation • Amplitudes branching ratios • Lorentz Structure  angular distributions

  3. LHCb: B physics at a ppcollider • And: nottoomanyprimarycollisions designlumi 2·1032 cm-2s-1 Signal B K±,p±,m±… Primary pp collision ~ 50 tracks K± m± Tagging B • Signal-background separation: • Invariant mass • Secondary vertices, IP • Particle Id (p-K, etc) • CP violation studies: • Event-by-event lifetime • B flavour @ production <L> ~ 8 mm VELO RICH IP

  4. LHCb: B physics at a pp collider VELO TT RICH1 T RICH2 CALO MAGNET MUON

  5. Data taking in 2010 (and 2011) • CDF&D0 > 6000 pb-1 • But: x-sect (x3), acceptance, trigger, vertex resol., pID, flavourtagging • LHCb prospects: • 1 fb-1byend 2011 (2010 x 27) 2010:  42 pb-1 delivered  37 pb-1 collected (±10%) results in this talk 2011 :  150 pb-1 delivered  130 pb-1 collected DesignlumisinceMay 1st! Butwith ¼ of bunches

  6. Vertexing Tracking Hit residuals s(IPx) track (mm) sm(J/ym+m-) = 13.3 MeV (12.1 in MC) s(Z) vertex (mm) # tracks stB ~ 60 fs (~40 fs from MC), work in progress • oscillation period Bd(Bs) ~12500(350) fs

  7. Particleidentification D  K+p- from D* Ksp+p- Lp+p- fK+K-

  8. Production & spectroscopy

  9. Z production (16.5 pb-1) LHCb-CONF-2011-012 Trigger: pT(m)>10GeV ATLAS CMS ds/dh (pb) hZ x: fract. of pbeamcarried by colliding parton Q2: squared p transfer in partonic collision LHCb preliminary Mainsyst: lumi

  10. W- W+ Acceptance of GPDs W production (16.5 pb-1) LHCb-CONF-2011-012 • Selection: lepton + global event (ΣM<20GeV, ΣPT<10GeV) Trigger: pT(m)>10GeV LHCb preliminary Z&W data vs models: ATLAS, CMS

  11. J/yproduction (5.2 pb-1) Eur. Phys. J. C 71 (2011) 1645 • Interesting: no model describes both dsJ/y/dpT and J/y polarization from Tevatron • LHCb: >0.5M J/y’s, no life-time bias @trigger • Measured both in 5 bins of h and 14 of pT • Prompt and from-B separated using pseudo-lifetime Onebin! from b prompt Prompt J/y production One bin! Main systs: lumi, J/y polarization, etracking

  12. Eur. Phys. J. C 71 (2011) 1645 sbb Phys. Lett. B 694 (2010) 209 • Method 1:from J/y • From “long-lived” component in J/y analysis • Extrapolated to 4p: spp = 288 ± 4 ± 48 mb • Method 2: through b→D0(→K-π+)Xμ-ν (uses BRs of B0D*-Xμ+ν D0Yμ+ν, B+  D0Xμ+ν, B0s  Ds*-Xμ+νD0Yμ+ν) • Extrapolated to 4p: spp = 284 ± 20 ± 49 mb • Good agreement between both • though correlated errors: lumi, etracking, etc) Additional syst.: BR(b→J/ X) (NLO, MCFM v5.8, Campbell, Ellis) Cacciari, et al., NL0 + resum of pT logs to NLO , e.g. hep-ph/9803400 Theoretical error (e.g. mb and μR,F) Mainsysts: lumi, etracking Black, violet: 2 subsamples with different trigger Red: combination

  13. fs/fd LHCb-CONF-2011-013 • Required for normalizing new Bs BRs with precisely-measured Bd BRs from B factories, current uncertainty 13% • Use decays of Bsand B0 with: • Precise theoretical prediction of ratio of BRs •  same kinematics  cancellation of systematics B0 D-(K+p-p-)p+ B0 D-(K+p-p-)K+ BsDs-(K+K-p-)p+   Same particles in final state Theo. uncert.  9% Theo. uncert.  7% LHCb preliminary Mainsyst: BR(Ds+KKp), 5%

  14. Mass of X(3872) LHCb-CONF-2011-021 • Mass far from expected from conventional charmonium state • Exotic alternatives: D*D0 molecule, tetraquark LHCb preliminary Main systs: p scale, E loss correction, TT alignement

  15. Towards CP violation

  16. CP violation • Bd sector extensively studied at B factories • CKM is basically OK • Lacking precise direct measurement of g • Required modes too rare (B fact. yield 10-4LHCb) • g will provide many new tests of SM • Bs sector only accessed by Tevatron • Lacking a precise measurement of the Bs mixing phase • Penguins unexplored! • Some hints of NP: • Like-sign di-m charge asymmetry hints for NP in mixing, sin2b…

  17. Direct CP violation in B0/Bs K-p+ LHCb-CONF-2011-11 LHCb: ~9σ CP viol. notyetstablished Before LHCb Not corrected for det. & prod. asymm. Bd Bs LHCb preliminary • We had to control potential sources of fake CP violation: • Detector: from many D decays, magnet up & down, using known CP violation • Production: from B+J/y(m+m-)K- + MC correction for B+B0

  18. g from tree processes • Time-independent methods: same final state through crossed D decay (GLW, ADS, GGSZ…) • Main challenge: BRs in suppressed modes • Enhancing statistics: • Measured relative BRs with world-best precisions! • Proved we can do physics with 6 track decays B-D0K- +p+p- LHCb preliminary LHCb-CONF-2011-07

  19. hadron from fragmentation or B** decay (K±, p±) Same side (SS) Signal B PV vertex charge Dx Tagging B Opposite side (OS) kaon (K±) lepton (m±, e±) Flavour tagging & Dmd LHCb-CONF-2011-03 LHCb-CONF-2011-10 • Optimized using real data: Dmd fixed to pdg value LHCb preliminary Main systs: z scale, p scale (to 0.1%, due to B, align.)

  20. Dms LHCb-CONF-2011-05 • Used 1300 events: • Fit with event-by-event values of st (36-44 fs) & mistag prob. • eefftag = 3.8 ± 2.1 % (OS only) • Mixing signal at 4.6s level • CDF: • LHCb: LHCb preliminary

  21. Towards fswith Bs J/yf • Final state combines CP even-odd  need to disentangle polariz. amplitudes  angular analysis • Golden channel: • Acceptances are a key issue, benchmarked by measuring: a) B meson lifetimesb) Polarization amplitudes Time-unbiased trigger only st 50 fs LHCb-CONF-2011-02 LHCb preliminary LHCb-CONF-2011-01 LHCb preliminary All consistent with world values

  22. fs: first results from Bs J/yf • 757±28 events (t>0.3ps) • 7D fit (m,t,tag,η,φ,ψ,θ) • No point-estimate yet • Include statistical uncertainty & systematics from tagging and Δms • All other systematycs << stat. uncert. • Comparison with CDF: SM LHCb preliminary Expect world-best fs measurement with 2011 data!

  23. 1st observation of Bs decays • Bs→J/ψf0(980) (33 pb-1 ) • fs (as J/yf), no need for angular analysis • Bs→K*0K*0 • fs & g through Bs penguin, Bd → fKs • Bs→D0K*0 • Bckgrd for g from trees from BDK • Bs→Ds2*(2573)+m-n (20pb-1) • Start exploration of D reson. in Bs syst. PLB 698 (2011) 115 LHCb-CONF-2011-019 LHCb-CONF-2011-08 PLB 698 (2011) 14

  24. Rare B decays

  25. Bd K*m+m- BR  10-6 • Golden observable: • LHCb: • Good data-MC agreement • Expect to be competitive with 300 pb-1 • Rarestdecayseen: B±K±m+m- (BR  5 · 10-7) Useful to test SM prediction of BR(BKee) / BR(K Kmm) Nσ = 5.5

  26. B0/Bs m+m- Phys. Lett. B 699 (2011) 330 • Double suppression: FCNC & helicity • Precise SM prediction: Bsμ+μ- = (3.2±0.2)×10-9 B0μ+μ- = (1.0±0.1)×10-10 A.J.Buras, arXiv:1012.1447, E.Gamiz et al. Phys.Rev.D 80 (2009) 014503 • Sensitive to NP in scalar/pseudo-scalar sector: MSSM, large tanβ approximation BR(Bs,dμ+μ- ) ∝ tan6β/M4A • Results are competitive with world bests: Bs m+m- • BR(Bs→μμ) < 4.3 (5.6)×10-8 at 90% (95%) CL • CDF BR(Bs→μμ) < 4.3×10-8 at 95% CL • 3.7 fb-1Public note 9892 (2009) • D0 BR(Bs→μμ) < 5.1×10-8 at 95% CL • 6.1 fb-1Phys. Lett. B 693 (2010) • BR(B0→μμ) < 1.2 (1.5)×10-8 at 90% (95%) CL • CDF BR(Bd→μμ)<0.76×10-8 at 95% CL • 3.7 fb-1 Public note 9892 (2009) B0 m+m-

  27. Bs m+m-: prospects LHCb will either find signs of NP or exclude large regions of SUSY parameters with 2010/11 data NUMH1 (O. Buchmuller et al, EPJ C64 (2009)) Compatible regions

  28. Conclusions • LHCb has successfully: • Started exploration of terra incognita: • Proton PDFs • Flavour production • Spectroscopy • Bs and Bd BRs • Produced world-class measurements • Dms • Limits on BR(Bmm) • Demonstrated its capability to find NP with 2010/11 data: • g • fs • BR(Bmm) • B0K*mm • ...

  29. Back-up

  30. Bc+ production Uproduction LHCb-CONF-2011-017 LHCb-CONF-2011-016 • Interestingfor QCDbecause heavy-quark state, challengingbecausefc 0.2 % • Total of  2.2K candidates(in 3 modes) fromTevatron • 43±13 in LHCb… Um+m- Mainsysts: etrigger, Upolariz. Bc±J/yp ± CMS LHCb • In addition: double J/y Mainsysts: Bc±lifetime LHCb-CONF-2011-009

  31. 1st observation of Cabibbo-suppressed decays LHCb-CONF-2011-24 • BR’s measured relative to Cabibbo-favoured modes:   Expect dg/g  5 with 2011/12 data

  32. Rare decays • Interesting decays at the limit of statistical reach of B factories and Tevatron • Some examples: m+ t m+ m+ Z, Z, m- m- m- g g BR NP affects: Right-handed operators  g polarization  CP viol. in mixing appears Bsfg •  5·10-5 Angular distributions sensitive to several new operators B0K*m+m-  10-6 SM: dBR/BR  10%  sensitive to new scalar & pseudoscalar interactions MSSM: BR  tan6β/MA4 • TeVatron @90%CL (2fb1) < 4510-9 Bsm+m-

  33. Branching ratios Production studies • h coverage complementary to that of ATLAS and CMS •  • B factories @ U(4s) measured Bd BRs with precisions 2.5-5% • Could count numbers of produced B • At Tevatron, LHC: non-straight-forward production mechanisms  use B-factory measured BRs for nomalization • To normalize Bs using Bdone needs ratio of b quarks hadronizing to Bs over Bd (fs/fd) • CDF (La Thuile 2011): fs/fd = 0.269 ± 0.033 • HFAG (ALL): fs/fd = 0.270 ± 0.034  13% relative error

  34. Running conditions • LHCb prefers moderate luminosity to avoid multiple pp interactions / crossing • They complicate handling of secondary vertices • 2010 and 2011 conditions far beyond nominal: m # interactions/crossing Design

  35. D0 flavor-specific asymmetry • Inclusive method not fit for LHC, with expected production asymmetry  1%. • Solution: measure difference, where this and other effects cancel D0

  36. Fragmentation functions: semileptonic 3pb-1 • Uncertainties: • Branching ratio BR(Ds) • Bs detection eff • BR(Bs→D0KXμν) • Tracking, PID, Trigger efficiency N(D0) from b: 28474±190 D0 N(D+) from b: 9406±105 D+ N(Ds+) from b: 2208±61 Ds+ • Updated results expected soon

  37. fs at Tevatron

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