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Measurements of the CKM angle g in tree-dominated decays at LHCb

Hadron Collider Physics Symposium, Kyoto, November 12-16, 2012. Measurements of the CKM angle g in tree-dominated decays at LHCb. Stefania Ricciardi (STFC Rutherford Appleton Laboratory ) o n behalf of the LHCb Collaboration. Outline. A very productive year for g at LHCb!

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Measurements of the CKM angle g in tree-dominated decays at LHCb

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  1. Hadron Collider Physics Symposium, Kyoto, November 12-16, 2012 Measurements of the CKM angle g in tree-dominated decays at LHCb Stefania Ricciardi (STFC Rutherford Appleton Laboratory) on behalf of the LHCb Collaboration

  2. Outline A very productive year for g at LHCb! • Results from time-integrated methods • B+ D(KK,pp,Kp)K+ [PLB 712(2012),213] • B+ D(Kppp)K+ [LHCB-CONF-2012-030] • B+ D(KSpp,KSKK)K+ [PLB 718(2012) 43] • First g average from LHCb [LHCB-CONF-2012-032] • First measurements with neutral B decays • B0 D(KK,Kp)K*0 [LHCB-CONF-2012-024] • First time-dependent measurements • B0sDSK± [LHCB-CONF-2012-029] • Other promising multibody decays first observation • B0sDSK ± p+p- [LHCB-PAPER-2012-033] All results based on 1 fb-1 (2011 data-set) Stefania Ricciardi

  3. Precision on g, apath to NP discovery • CKM fits: overall a triumph for SM! However, a few tensions exist • More precision needed to unravel subtle NP effects • g at tree-level largely unaffected by NP, essentially no theoretical uncertainties • gstill least-well measured angle of the UT 66 ± 12 CKMFITTER 72 ± 9 UTFIT Post-ICHEP 2012 average using BaBar, Belle, CDF and first LHCB results g from tree-level decays: theoretically very clean, but experimentally very challenging! [Zupan, arXiv:1101.0134] Stefania Ricciardi

  4. g from trees: time-integrated methods Sensitivity to g through interference of b → c and b → u tree-level amplitudes Interference requires D0 and D0 decay to common final state fD • Hadronic unknowns: • rB,dB • rD, dD • All from data  No hadronic uncertainties • Method to extract them depends on D decay Favoured H- Vcb D0H D0 GLW -CP eigenstates: KK,pp[Gronau-London-Wyler] PLB 253,483(1991), PLB 265,172 1991) ADS- Quasi-flavour-specific: Kp, Kppp[Atwood-Dunietz-Soni] PRL 78,257(1997), PRD 63,036005 (2001) GGSZ - Self-conjugate 3-body : KSpp, KSKK [Giri-Grossman-Soffer-Zupan] PRD 68,054018(2003) Bondar,PRD 70,072003 (2004) D0 B- u u u u B fDH Suppressed Vub D0H D0 • H Expected rB • K0.1 • p0.005 • Naïve assumptions , charged B decays only B- H- Stefania Ricciardi

  5. Experimental challenges Precision @VERTEX LHCB Vertex detector and tracking Excellent invariant mass resolution Excellent vertex resolution Mass resolution and displaced vertices for separation from low-mass background and rejection of combinatorial background Large data sample dedicated trigger Efficient retention of fully hadronic B decays while limiting the overall output <5KHz PID : 2 RICH detectors @LHCb K-p separation over 2—100GeV/c KS reconstruction (specific to GGSZ mode) About 2/3 of KS decay downstream of vertex detector Effectively separate B→DK from 10x more abundant B→Dp Stefania Ricciardi

  6. GLW with B+→D(hh)K+ • [PLB 712(2012),213] D0H B±DK± DCPH B B±Dp± D0H ACP+ (pp)= (-13.5 ± 6.6 ± 1.0)% ACP+ (KK)= (-14.8 ± 3.7 ± 1.0)% B±DK± : clear asymmetry B±Dp± : no significant asymmetry Evidence of non-zero ACP+ in B±DK±with 4.5 ssignificance (KK+pp) Stefania Ricciardi

  7. ADS with B+→D(Kp)K+ DCS CF First observation of rare ADS OS B+ D(K-p+)K + (Opposite Sign kaons) [10s] D0H (K-p+) H+ B+ D0H Large asymmetry in BDK : AADS = (-52 ± 15 ± 2)% [4s] Hint of asymmetry in BDp: AADS = (14.3 ± 6.2 ± 1.1)% [2.4s] Stefania Ricciardi

  8. GLW and ADS with B+→D(Kp)K+ GLW ADS LHCb results on ADS and GLW observables more precise than B-factories and Tevatron results Stefania Ricciardi

  9. ADS with B+→D(K3p)K+ [LHCB-CONF-2012-030] Same rB and dB, but different D decay parameters Complementary information to B D(Kp)K not just additional statistics CLEO-c PRD 0031105(2009) First observation of rare ADS mode in BDK [5.1s] and BDp [>10s] Hint of asymmetry in BDK: AADS = (-42 ± 22 )% BDp: AADS = (13 ± 10 )% RADS (K) = (1.24 ± 0.27 )% RADS (p) = (0.369 ± 0.036 )% Stefania Ricciardi

  10. GGSZ: gfrom B+→D(KSh+h-)K+ [PLB 718(2012) 43] • Exploits interference pattern in the D→KSh+h-Dalitz plots (different for B+ and B-) • Rich resonance structure  powerful method (dominates precision on g from B-factories) m± = m(KSh±) B- B+ m+ (GeV2/c4) DKSp+p- 690 signal events Extraction of g requires information on the D→KShhdecay amplitude variation over Dalitz plot: both magnitude and phase dD model of decay amplitude or external measurements (model independent approach) B- B+ m+ (GeV2/c4) DKSK+K- 110 signal events Stefania Ricciardi

  11. GGSZ: binned approach Use discrete measurements of dDin Dalitzplot bins from CLEO-c: ci,si[PRD82(2010)112006] Ki = i |AD(m+ 2,m-2)|2dm+2dm-2 from flavour specific D decays DKSK+K- x±,y±extracted from a simultaneous fit to the signal yields in each Dalitz-plot bin Chosen binning optimise g sensitivity KSKK sample adds just 2 bins DKSp+p- Stefania Ricciardi

  12. GGSZ results [PLB 718(2012) 43] Uncertainties: Statistical Experimental systematic CLEO-c inputs x- = (0.0 ± 4.3 ± 1.5 ± 0.6) x 10-2 y-= (2.7 ± 5.2 ± 0.8 ± 2.3) x 10-2 x+ = (-10.3 ± 4.4 ± 1.8 ± 1.4) x 10-2 y+= (-0.9 ± 3.7 ± 0.8 ± 3.0) x 10-2 Leading source of experimental systematic uncertainty: assumption of no CPV in BDpused to determine efficiency Results on x,y have similar precision to those from BaBar and Belle g = (44 +43 -38) ⁰ rB = 0.07 ± 0.04 Likelihood scan (statistical error only) 2g rB (0,0) Lower rB implies larger uncertainty on g compared to B-factories from this mode rB Stefania Ricciardi

  13. Combination of B+→DK+ results [LHCB-CONF-2012-032] • Precision achieved by combination of GLW, ADS and GGSZ measurements • Frequentist method adopted using LHCb only results + constraints on D parameters from CLEO-c <rB> = 0.092 ± 0.008 <g> = 71.1 +16.1-15.2 () [43.9 – 98.8] @ 95%C.L. <dB>= 112.0 +12.6-15.5 () Comparable precision to g averages from BaBarand Belle BaBar: <g> = 69 +17 -16 () Belle : <g> = 68 +15 -14() Stefania Ricciardi

  14. Including B+Dp+ in the g average • Non-Gaussian behaviour • Impact on best-fit value: 71  85 (<1s) • 95% confidence level essentially unchanged B+→DK+ and B+→Dp+ rB(p) g <g> [61.8-67.8]  [77.9-92.4]@ 68%C.L. dB(p) [43.8 – 101.5] @ 95%C.L. g, rBp and dBp from combination of B+Dp+ GLW and ADS results only Stefania Ricciardi

  15. GLW with B0→D(KK)K*0 D0 d d d u c [LHCB-CONF-2012-024] • Self-tagged mode time-integrated methods similar to B+D(hh)K+ • Interfering diagrams both colour suppressed: • Larger rB (3x)  larger interference • Low yields Vub Vcb D0 b u b c B0 B0 s s K(*)0 K(*)0 d Bs Bs B B0 Hint of large asymmetry in B0DK0* : AdCP+ = (-47 ± 25 ± 2)% No significant asymmetry in BsDK*0 : AsCP+ = (4 ± 17 ± 1)% Stefania Ricciardi

  16. Bs→DsK: time-dependent method • Two final states: • Ds+K- andDs-K+ • Both accessible to Bs and Bs • CPV in decay w & w/out mixing  sensitive to g-2bs • Time-dependent analysis and flavour tagging required • Unique to LHCb b→c b→u + other 2 equations for f CP sensitivity in S tagged events only CP sensitivity in D thanks to DGs0 untagged&tagged events rDsK ~0.4 relative magnitude of the CKM-suppressed to CKM-favoured amplitudes Stefania Ricciardi

  17. Bs→DsK : analysis ingredients Tagging: OS only used in this first analysis, eD2=1.9% Precision tracking and PID: for background suppression Bmass fit: statistical separation of signal from remaining background Bs DsK Ds  KKp/ppp/Kpp Proper time resolution: from MC corrected for data/MC differences <st>~50 fs Signal yield = 1390±98 Proper time acceptance: a,b,n,b from fit to BsDspdata Stefania Ricciardi

  18. Bs→DsK : time-dependent analysis results [LHCB-CONF-2012-029] First measurement of the CP parameters in Bs→DsK Main systematic uncertainties: fixed parameters (Gs, DGs, Dms, acceptance); tagging calibration Extraction of g sensitive to correlations: work in progress to determine systematic error covariance matrix Includes both tagged (40%) and untagged (60%) events Stefania Ricciardi

  19. More under way:Bs→DsK p+p- ArXiv:1211.1541 NEW Bs→DsK p+p- can also be used to measureg-2bs with TD analysis (similar to Bs→DsK ) Bsand B0→DsKpp (first observation) First step: measurement of the branching fractions Selected Ds decays only: Ds  K*K and Dsfp Expect yield 40% ofBs→DsK when other Ds modes added and selection tuned for CP analysis Stefania Ricciardi

  20. Conclusions • First results on g from GLW/ADS/GGSZ measurements at LHCb • No single method dominates sensitivity • Combined measurement from B+→DK+ decays (1/fb, 2011 data sample) similar precision to Belle and Babar • First results from other sensitive modes • B0→D(KK)K*0 first observation • B+→D (hh)K+p+p- first observation • Bs→DsK • Bs→DsK p+p- first observation will provide additional measurements of g with 2011+2012 data sample • Additional g-sensitive B+,B0, Bs, Lb decays under study Excellent prospects for big improvements on g precision from tree-dominated decays! <g> = 71.1 +16.1-15.2 () Stefania Ricciardi

  21. Thank You Kyoto, HCP2012 <g> = 71.1 +16.1-15.2 () from tree decays [B+ →DK+ only] …and Thanks to Nature for these beautiful trees! Stefania Ricciardi

  22. GLW-like with B+→DK+p+p- [LHCB-CONF-2012-021] First observation of B+DK+p+p-with D CP eigenstates and first measurement of CP observables (GLW) Larger data-samples needed to perform ADS analysis and constrain g from these decays Stefania Ricciardi

  23. GGSZ Difference of B+ and B- yields Sum of B+ and B- yields Stefania Ricciardi

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