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Measurement of the CP parameters in B s  D s K and first observations of B (s) 0 D s K pp

Measurement of the CP parameters in B s  D s K and first observations of B (s) 0 D s K pp. Steven Blusk Syracuse University. on behalf of the LHCb Collaboration. Time dependent B s D s K analysis First observations of B s D s K pp and B 0 D s K pp.

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Measurement of the CP parameters in B s  D s K and first observations of B (s) 0 D s K pp

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  1. Measurement of the CP parameters in Bs DsK and first observations of B(s)0DsKpp Steven Blusk Syracuse University on behalf of the LHCb Collaboration • Time dependent BsDsK analysis • First observations of BsDsKpp and B0DsKpp CKM Workshop, University of Cincinnati, Cincinnati, Ohio, Sept 28 – Oct 2, 2012

  2. Introduction CKM Matrix Wolfenstein parameterization A~1, l = sinqc, r,h are real and imaginary parts in Vub (also in Vtd) • Amplitudes of CC weak interactions depend on 4 parameters in the CKM matrix. • Do these 4 parameters fully describe both the magnitudes and phases associated with many B, D, K decay processes? • Phase g Arg(Vub) is least well measured of the CKM angles, and among the most challenging experimentally • Small BFs ( Vubsmall ) • Purely hadronic modes

  3. Measuring g using Tree Decays • Motivation • Expected to be insensitive to new physics • Theoretically clean, experimental precision will dominate • Time independent measurements • Self-tagging modes, no time-dependence • B-D0K- (ADS, GLW, GGSZ, multi-body) [see talk by SnehaMalde] • Many other modes being explored as well:B0D0K*0, B- D0K-p+p-, BsD0(KK), LbD0pK [see talk by M. Williams] • Time-dependent measurements • BsDsK • Other modes under investigation: BsDsKpp, BsDsK*, B0Dp(pp) • In loops: • Bhh and hhh: See talks by Stefano Perrazini and Jussara de Miranda

  4. BsDsK Phenomenology 2bs g ( ) • CPV requires at least two paths to the same final state • Here: direct bc decay and (Bs mixing + bu decay). Two more rateequations Two rateequations Ds+K- Ds-K+ Bs Bs Bs Bs Ds+K- Ds-K+ • Also, CP conjugate final state: Advantage: Both decay amplitudes are O(l3)  LARGE INTERFERENCE

  5. BsDsK Decay rates Terms containing g have large|lf| (analogous to rB, in BD0K)  The 5 observables are related to the 3 physics parameters (lf, d, g-2bs): where

  6. BsDsK LHCb-CONF-2012-029 Also, see: LHCb Collab, JHEP 1206, 115 (2012) ~1010Bs per fb-1in LHCb acceptance(at s = 7 TeV) +high eff. trigger • Challenges • (fBs/ fb) * BR ~ 10-6. • Fast Bs oscillations • Flavor tagging • Good background rejection needed. st ~ 50 fs « 175 fs timefor BsBsoscillation • Excellent vertex & mass resolution. • Excellent muon, electron and hadron ID (RICH)

  7. Measuring the CP parameters Two strategies being pursued “sFit” “cFit” 1) Simultaneous fit to: mass  time 2) Need to additionally model time distribution of backgrounds. 16 free parameters in fit 1) Fit DsK invariant mass spectrum  extract sWeights2) Apply sWeights to measured Bs candidate decay times to statistically subtract the background.3) 1D fit to the (pure signal) time distribution (no need to model time structure of backgrounds) 5 free parameters in fit cFit usedas x-check Currently, default method

  8. BsDs(p,K) Selection • Trigger (LHCb-PUB-2011-016) • L0: Any L0 trigger (high pThadron, m, mm, etc) • HLT: 2, 3 or 4-body displaced vertex, w/ large SpTand  1 track w/ pT>1.7 GeV/c. • Offline • Reconstruct: Ds+K+K-p+ (B=5.5%), p+p-p+ (B=1.1%)and K+p-p+ (B =0.7%) • Cross-feed suppression from other bc: E.g. BDh, LbLch • Combinatorial background suppression: Data-driven BDT • BsDsp x-feed into BsDsK: Stringent PID requirements on “bachelor” kaon. • Charmless: Require Ds to be significantly displaced from Bs decay point. • Ds mass sidebands show remaining charmless background negligible.

  9. Remaining backgrounds BsDsp

  10. BsDspmass fit Signal yield = 27965 ± 395 Includes:DsKKp, ppp, Kpp

  11. Remaining backgrounds BsDsK Analogous/similar to BsDsp

  12. BsDsK mass fit Signal yield = 1390 ± 98 Includes:DsKKp, ppp, Kpp B0DsK

  13. Time fits - Ingredients • Flavor tagging: Determine flavor of B at production • With a tag comesan efficiency (etag), and a mistagprob (wtag). • Recall • We fit for the coefficients of the cos(Dmst) and sin(Dmst) terms  Need to have good understanding of wtag! • Good decay time resolution • Knowledge of decay time acceptance ( + imperfect tagging algorithms) etag (1-2wtag) (1-2wtag)

  14. Flavor Tagging Details in:LHCb-CONF-2012-026 e-, m- “Opposite” side K- Vertexcharge D0 B- K- Bs Ds- K+ Signalb-hadron p- “Signal (same)” side K+ K+ • Flavor of signal b-hadron can be determined using either • Opposite (OS) side tag: • Same side kaon tag • Currently, only OS tag used in this analysis: optimized on flavor-specific decays (J/yK+, BD*+ln ..) • More details in talk by Julian Wishahi

  15. Time resolution • Shape obtained from simulated BsDsK • Resolution function described by the sum of 3 Gaussians. • Each Gaussian width scaled up by a factor of 1.15(Data/MC correction)Determined by comparing width of “fake Bs” == prompt Ds + random track between data and simulation. • Prompt  ‹ t › = 0 , and width is measure of time resolution <st> ~ 50 fs

  16. Time acceptance • Fit BsDsp data with fixed Gs, DGs, (HFAG averagevalues) to get a, b, n,b. • In BsDsK time fit, a correction is applied to accountfor small difference in acceptance between DsK andDsp (~1% difference per 1.5 ps)

  17. Reconstruction effects on flavor-tagged BsDsp (toy) Assuming 80,000reconstructedBsDsp.

  18. Time fit results: BsDsK Includes both tagged (40%) + untagged (60%) events Fixed parameters: Dms = 17.719 ps-1 DGs = 0.105 ps-1 Gs = 0.661 ps-1 (From HFAG) proper time [ps]

  19. Results for CP parameters • First measurement of the CP parameters in BsDsK. • Several possible improvements to sFit analysis being explored  lower sstat. • Also lower uncertainties expected withcFit (mass  time ) 2D fit. Uncertainties, given as a fraction of the statistical error.Total systematic error is absolute. All uncertainties reduciblewith either larger signal/control samples, and withforthcoming analysisimprovements. Time Indep Time Dep • Extraction of g sensitive to correlations : Requires a bit more work on syst. error covariance matrix. (Stat. error correlation matrix in backup)

  20. First observations of BsDs+K-p+p- and B0Ds+K-p+p- LHCb-PAPER-2012-033

  21. Motivation • BsDsKppcan also be used to measure g (alaBsDsK) • B0DsKpppresents a significant background. • Neither of these decays have been observed to date. Bs Decay Diagrams bc tree bu tree bc W-exchange K-, K*-, K1-, etc B0 Decay Diagrams bc tree, w/ ss bc tree, w/ ss bc W-exchange

  22. First goals • Observe these decay modes, and measure ratios of BFs: • Selections very similar to BsDsK analysis • Only use Dsfp, K*K: Non-resonant KKp shows significant charmless background contribution to B0 signal (~none for Bs) • BDT to suppress combinatorial background. • Main differences: • ppp or Kpp mass: 0 < M(3h) < 3 GeV • Backgrounds challenging, due to lower <pT> of daughters. • Types of backgrounds similar.

  23. Signals in Data BsDsKpp BsDsppp N(B0) = 40233 N(Bs) = 21621 N(Bs) = 568383 Preliminary Preliminary

  24. Results (Preliminary) Systematicuncertainties • B(BsDsKpp) consistent with Cabibbo suppression • B(B0DsKpp) and daughter invariant masses suggest dominantcontribution from ss popping • K*p and Kr dominate Kpp final state, with perhaps small contributions from excited strange states (K1(1270), K1(1400), etc)[ next slide ]

  25. Two and Three-Body Masses Bs DsKpp Prominent contribution from “narrow” excited strange states Preliminary Preliminary Preliminary Kpp Mass (MeV) pp Mass (MeV) Kp Mass (MeV) Small contribution from narrow excited strange states B0 DsKpp Preliminary Preliminary Preliminary Kpp Mass (MeV) pp Mass (MeV) Kp Mass (MeV)

  26. First Observation of BsDs(2536)+p- LHCbPreliminary BsDs1(2536)p, Ds1+  Dspp > 6s significant Ds1(2460)would be here (No Ds0*(2317)+ peak seen)

  27. Summary • First time-dependent CP analysis of BsDsK presented • Room for improvement in uncertainties, with addn’l refinements in analysis. • Include SS Kaon tags • g extraction in progress • Incl. 2012 data will increase sample size ~3-4x current yield. • Other decays also being explored • BsDsKpp (first observation): Expect signal yield of ~40% of BsDsK yield. • Other possibilities: BsDsK*+, addn’l Ds decays:DsKsK, KKpp0..B0 decays: B0D-p+, D-ppp … • Other first observations • B0DsKpp, BsDs(2536)p. Matter Anti-matter

  28. Summary • First time-dependent CP analysis of BsDsK presented • Room for improvement in uncertainties, with addn’l refinements in analysis. • Include SS Kaon tags • g extraction in progress • Incl. 2012 data will increase sample size ~ 3x current yield. • Other decays also being explored • BsDsKpp (first observation): Expect signal yield of ~40% of BsDsK yield. • Other possibilities: BsDsK*+, addn’l Ds decays:DsKsK, KKpp0..B0 decays: B0D-p+, D-ppp … • First observations: • B0DsKpp, BsDs(2536)p. Many thanks to the organizers and session chairs

  29. Backup

  30. BsDsK, by Ds final state

  31. Correlation matrixfor CP parameters in BsDsK(Statistical errors only)

  32. BsDsppp Masses Masses

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