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B s D s h and BDh Decays in LHCb

B s D s h and BDh Decays in LHCb. Steven Blusk Syracuse University On behalf of the LHCb Collaboration. Beauty 2011, Amsterdam, The Netherlands, April 4-8, 2011. Introduction.

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B s D s h and BDh Decays in LHCb

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  1. BsDsh and BDh Decays in LHCb Steven Blusk Syracuse University On behalf of the LHCb Collaboration Beauty 2011, Amsterdam, The Netherlands, April 4-8, 2011

  2. Introduction If NP exists, (and its couplings to the quark sector are not highly suppressed), there should be observable/sizeable effects in loop-mediated diagrams. • B decays provide an excellent laboratory to search for NP in box/loop diagrams • Tremendous progress in the last decay (BaBar, Belle, CLEO, CDF, D0, Lattice…)  New Physics not dominant • But, there is tension/hints. • 2-3s deviations in sin(2b) • Largedirect CPV inBKp. • Maybe hints in sin(2bs), although clearly we need to shrink errors here. • D0 Asl tantalizing, needs confirmation • While errors have been slowly shrinking, we are in great need of precise, “NP-free” measurements. • Direct g dominated by trees  ~NP free • Will play a crucial role in sorting out NP scenarios in the CKM paradigm. E. Lunghi and A. Soni arXiv.1010.6069v2

  3. Angle g in LHCb • Time-independent (ADS, GLW, GGSZ, etc) • E.g. B- D0K- B0 D0K*0B- D0K-p+p- • Time-dependent • E.g. BsDs+K-, BsDs±K-p+p- B0D-p+ B0D-p+p-p+ • Challenges: • Sensitivity through bu low rates • Excellent PID critical, e.g. DCS D0Kp • Fully hadronic mode, triggering, backgrounds • Key strengths of LHCb (for g) • Large b production rate: ~100 kHz bb • Excellent PID: 2 RICHs, eK~95% , O(<5%) p-K misid • Excellent proper time resolution (needed for time-dependent analysis) • Trigger: next slide

  4. A few words on triggering • Sensitivity to g through hadronic final states  hadronic trigger crucial. • L0: require 2x2 calorimeter cluster with ET>3.6 GeV. • eL0/eoff-sel ~ 45% • HLT: • HLT1: Require a single track with pT>1.25 GeV, p>12.5 GeV and IP>125 mm. • eHlt1/eoff-selxL0 ~ 80-90% • HLT2: Form 2, 3, and 4-body states, among tracks with IP c2>16, pT>0.5 GeV, p>5 GeV. • eHlt2/eoff-selxHlt1xL0 ~ 80-90% • Signal on tape is comprised of events where we: • Trigger On the Signal (TOS) • Trigger Independently of the Signal (TIS):generally from the other b • L0: ~50% TOS & ~50% TIS • HLT1 & HLT2: ~90-95% TOS, O(10%) TIS • Some analyses use TOS only, some TOS & TIS

  5. LHCb in 2010 • In 2010, LHCb collected ~37 pb-1 of data • Only 2.5% of a nominal LHCb year, but: • Enough to demonstrate capabilities in key channels • Already able to make world class measurements, including several first observations. • Today, I will present: • Measurement of B0DK-[LHCb-CONF-2011-013] • First observation of BsD0K*0 [LHCb-CONF-2011-008] • New measurements of XbXcppp and First observation of BDKpp. [LHCb-CONF-2011-007, LHCb-CONF-2011-018] • Other signals & work in progress.

  6. p IP K K p B0DK- and fd/fs [LHCb-CONF-2011-013] Goals: • Precise measurement of fs/fd. [ Very important for normalizing Bs decay rates in LHCb ] [1] Using BsDs-p+ and B0D-K+ [2] Using BsDs-p+ and B0D-p+ Refer to talk by Neils Tuning on Tuesday • Improve on B(B0D-K+) [Current error ~30%] Offline Selection: most notable: • D Daughters • IP c2 > 9, pT>300 MeV • DLL(K-p) < 10 (p) • DLL(K-p) > 0 (K) • Bachelor • IP c2 > 9, pT>500 MeV • DLL(K-p) < 0 (p) • DLL(K-p) > 5 (K) Bs Ds • D • pT>1.5 GeV • Vertex c2/dof < 12 • B • tB > 0.2 ps • Vertex c2/dof < 12 Topology:E.g: BsDsp BDT used to optimize usage of a number ofkinematic variables:  Trained on signal MC and data sidebands Trigger:L0 & HLT must Trigger On Signal(TOS) B hadron

  7. Signals and Results B0 D-K+ BDp faking BDK, shape derived from data Events/8 MeV Events/16 MeV B0 D-p+ Most precise measurement of this branching fraction!

  8. First Observation of BsD0K*0 • Ultimate goal is to use B0D0K*0 to measure g. • Both diagrams are O(l3) & CS  interference term large • Flavor-specific  time-independent analysis [LHCb-CONF-2011-008] But significant source of background from Bs D0K*0 , andis O(l2) Immediate goal:Measure the rate of this process Normalize to B0D0r0. Kinematically similar (most systematics cancel) O(l2)

  9. Analysis Details Offline Selection: most notable: • D0 Daughters, K (p) • IP c2 > 4 • pT>400 (250) MeV • DLL(K-p) < 4 (p) • DLL(K-p) > 4 (K) • K*/r0 daughters • IP c2 > 4, pT>300 MeV • DLL(K-p) < 3 (p) • DLL(K-p) > 3 (K) B0 K*/r0 K(p) D0 p • D0 • pT>1.5 GeV • Vertex c2/dof < 5 • |m-mD|<20 MeV • K* (r0) • pT > 1 GeV • |cosqh|>0.4 • |m-mV|<50 (150) MeV Topology:E.g: BD0K*0 K p • B • tB > 0.2 ps • Vertex c2/dof < 4 • IP c2 to PV < 9 Uses both TOS and TIS events

  10. First Observation Observed Signals B0 D0r0Normalization Mode Bs D0K*0Signal Mode B0 candidate mass (GeV) Bs candidate mass (GeV) pp invariant mass (MeV) Kp invariant mass (MeV) • Non-r0 contribution: Estimated to be: 30±8 events (need to subtract from the D0r0 yield) • Kp spectrum appears to be consistent with only K*

  11. Results Using fd/fs = 3.71±0.47 from HFAG PID systematic is conservative at this point.

  12. XbXcppp & XbXcKpp Xb = B(s) or Lb Xc = D(s) or Lc • Current measurements are of low precision, ≥ 30% uncertainty or non-existent • These multi-body decays are of interest: • Bs Ds pppfor Dms and serves as a calibration of SSKT for BsDsKpp . • B0 D-ppp can be used to extract g. • BsDsKpp for time-dep. g meas. • B-D0Kpp for time-indep. g meas. • Improve our understanding of B decays PDG • Similar selection criteria to previousanalyses: IP c2, pT, vertex c2, B “points” back to the PV, etc. B K1(1270) K D p Topology:E.g: BDKpp K p p K

  13. Signals in CF modes Signal Modes Normalization Modes B-D0ppp B-D0p B0D-ppp B0D-p BsDsppp BsDsp Lb Lc ppp Lb Lc p Only TOS events used for BF measurement. S/B in 5,6 body modes not much lower than in 3, 4 body modes

  14. Sub-structure in the ppp spectrum B0D-ppp B-D0ppp Red points witherror bars show data Line shows MC simulation Significant a1(1260) +component, but also longtail (non-resonant) out to 3 GeV Similar structure for all b-hadron species. BsDsppp Lb Lc ppp

  15. Results Systematics: ~10% Dominant: Tracking (2 tracks): 6% Trigger Efficiency: 5% Mass Fit: 4-6%  All are reducible in near future PDG • Significant improvement in our knowledge of these decays • Interestingly, the B-D0ppp ratio is closer to 1.0, as opposed to 2.0? • Both CF and CS diagrams present. (Unlike B0, Bs or Lb)  Strong phase(s) differ… Two body amplitude analysis, see: Rosner and Chang, PRD67, 074013 (2003).

  16. Cabibbo-Suppressed Decays With 35 pb-1, we expect ~100 signals events (should be observable) B0D-Kpp andB-D0Kpp • Extension of the analysis on CF decays. • Slightly tighter kinematic selections: applied to both signal and normalization mode • Take all triggers: Signal & trigger efficiencies ~equal to first order. • Tighter kaon PID to suppress CF background; pK<100 GeV (effective region for K/p separation) Selection & trigger efficiencies, as determined from signal MC • Excludes kaon PID efficiency • Evaluated directly from D* calibration data this is not surprising, as the kinematics are very similar. Slightly lower trigger efficiencyin CS mode due to pK<100 GeVrequirement

  17. Signals in Data First Observation First Observation B0D-Kpp B-D0Kpp 8.0ssignificance 6.6ssignificance B0D-ppp B-D0ppp

  18. Results on CS Decays Fitting uncertainty~5% dominantsystematic. For comparison: BDK: Observed ratios in the range of what is expected. B mass signal region B mass sideband region Kpp mass spectrum consistent with dominance of lower lyingK** resonances

  19. Other bbeautiful signals in key modes Working toward g measurement in B- D0K- B- D0p- With D0pp With D0Kp With D0KK With D0Kspp B- D0K- With D0KsK+K-

  20. LHCb, with sg~5o Summary • CKM angle g is one of LHCb’s key measurements for exposing or constraining new physics. • With just 37 pb-1, we have already made world-class measurements. • Yields in key channels are consistent with our expectations. • On track to carry out our rich program of CPV measurements. • Several first observations … and more certainly to come. • Bs and Lb decays largely uncharted territory! • With the 2011 data sample, (~1 fb-1) we expect to measure g to ~5-7o. • We’re optimistic that theSM will yield to precisionb decay measurements! 20 E. Lunghi and A. Soni arXiv.1010.6069v2

  21. B0D0r0 (Triggered on Signal B) (Triggered on Other B)

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