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Measurements of B Rare Decays at the Tevatron

Measurements of B Rare Decays at the Tevatron. Fabrizio Scuri a) – I.N.F.N. Pisa for the CDF and D0 Collaborations Les Rencontres de Moriond – QCD and Hadronic Interactions La Thuile, March 17-24, 2007 . Topics: B  h + h - (charmless) recent results B  mm search status

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Measurements of B Rare Decays at the Tevatron

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  1. Measurements of B Rare Decaysat the Tevatron Fabrizio Scuri a) – I.N.F.N. Pisa for the CDF and D0 Collaborations Les Rencontres de Moriond – QCD and Hadronic Interactions La Thuile, March 17-24, 2007 • Topics: • B  h+h- (charmless) recent results • B  mm search status • B  mm h updates a) e-mail: fabrizio.scuri@pi.infn.it Rare B decays at the Tevatron - Moriond QCD 2007

  2. 1) Charmless B  h+ h’- • a useful tool for probing CKM • sensitive to the New Physics contributions • in the Penguin diagrams • sensitive to New Physics effects via • anomalies in ACP Tree Penguin ? =arg(Vub) 2) Bs  mm SM prediction very suppressed (M.Blanke et.al., JHEP 0610:003,2006) (T.Hurth, hep-ph/0612231v1) Sizable New Physics enhancement predicted in non MFV scenarios, e.g. high tanb SUSY (BSUSY(Bmm) (tanb)6) 3)B  mm h (b  s l+l-) Additional information on the flavor dynamics of FCNC decays from the s-quark and di-lepton system FB asymmetries Why Rare (BR O(10-6) or lower) B Decays are so interesting ?

  3. s(bb) at Tevatron is O(105) larger than production in e+e- colliders at Y(4s) or Z0 energy scale -- all b-hadrons (B+, B0, Bs, Bc, Lb, Sb,……) are produced -- physics program complementary to the B-Factories Fine, but… • The total inelastic x-section is a factor 103 larger than s(bb) • The BRs of rare b-hadron decays are O(10-6) or lower • therefore….. CDF Interesting events must be extracted from a high track multiplicity environment……. Heavy Flavor physics at the Tevatron • Detectors need to have: • Very good tracking and vertex resolution • Wide acceptance and good ID for electrons and muons • Highly selective trigger Rare B decays at the Tevatron - Moriond QCD 2007

  4. Bh+h’-: pp invariant mass 7000 Signal events S/B  8.3 at the peak Region of unobserved modes hidden in the cut optimization procedure Combinatorial background Partially reconstructed B-decays Individual modes overlap in a single peak ! B  h+ h’- Signal composition is determined with a Likelihood Fit, combining information from kinematics (mass and momentum) and particle identification (dE/dx). Rare B decays at the Tevatron - Moriond QCD 2007

  5. CDF unique Now, first results on 1 fb-1 large data sample are available  High precision measurements: a) first observation of rare modes such as Bs  K-p+, Lb  p K-, Lb  p p- b) New limits on B0 K+K- and Bs  p+p- Mode New CDF (BR x 106) (1 fb-1) B0p+p- 5.10 ± 0.33(stat.) ± 0.36(syst.) B0K+K- 0.39 ± 0.16(stat.) ± 0.12(syst.) BsK+K- 24.4 ± 1.4(stat.) ± 4.6(syst.) Bsp+K- 5.0 ± 0.75(stat.) ± 1.0(syst.) Bsp+p- 0.53 ± 0.31(stat.) ± 0.40(syst.) B  h+ h’- : BR result summary • In this talk only highlights on Direct CPV in B0 K+p- and Bs  K-p+ Rare B decays at the Tevatron - Moriond QCD 2007

  6. BsK+p- • First measurement of direct CP • asymmetry in the Bssystem • Direct CP asymmetry measurements • for Lb modes in progress. Raw DCPV asymmetries B0K+p- Plot of pdf(B0)/[pdf(B0)+pdf(B0)] shows the good separation achieved between B0 and B0 (M, , ptot, dE/dx) Rare B decays at the Tevatron - Moriond QCD 2007

  7. ACP BaBar 07 0.2 0 0 -0.2 New result on ACP(B0K+p-) with 1 fb-1 • CDF competitive with BaBar/Belle • Tevatron and B-Factories results agree • 6-7 s effect • Difference with ACP(B+K+p0) • confirmed Rare B decays at the Tevatron - Moriond QCD 2007

  8. The Lipkin test: minimal assumptions, just SM with SU(3) symmetry [Lipkin, Phys. Lett. B621:126, .2005],[Gronau Rosner Phys.Rev. D71 (2005) 074019]. w.a. HFAG ≈ 0.37 w.a. HFAG CDF BR ≈ 1 New results for the Bs K-p+ mode with 1 fb-1 In agreement with latest prediction of SCET: (4.9 ± 1.8) 10-6 Lower than previous predictions of QCDF and pQCD: [6-10] 10-6 Still marginal but sign and magnitude agree with SM predictions  no evidence for exotic sources of CP violation (yet) Very interesting to pursue with more data ! Rare B decays at the Tevatron - Moriond QCD 2007

  9. Procedure • Blind optimization using signal Monte Carlo sample and sideband data • Normalize to the B+J/K+ mode • Reconstruct normalization mode in the same data sample, applying same • criteria  reduce systematics, only ratio of efficiency matters • Evaluate expected background, then “un-blind” the signal region and • calculate BR or limit Similar discriminating observables for the two experiments: (Secondary vertex displacement, B pointing angle to the P.V., B isolation,…..) Similar methods for the search optimization: - CDF: construct a lilkelihood ratio LR with three discriminating observables and optimize LR cut on the expected a-priori 90% C.L. limit - D0: construct a lilkelihood ratio LR with six discriminating observables and a): emm / <nup.lim.(nexp.bkg.)> optimize LR cut on same optimal values b): emm /(1+sqrt(B)) ] B  m+m- Rare B decays at the Tevatron - Moriond QCD 2007

  10. B  m+m- Normalization mode: B+J/y K+ (J/ymm) (~1250 pb-1) Event yield after optimization Optimal LR (~750 pb-1) Run IIb after Summer ’06 insertion of a new inner layer in the SMT

  11. Bmm result summary Dominant uncertainty sources • World best limit, compare • Babar (hep-ex/0408096, 110 fb-1 ) • BR(Bdmm) < 8.3 ∙ 10-8 @ 90% C.L. (*) D0 assumes the contribution of Bdmm to B(Bsmm) suppressed due to |Vtd/Vts|2~ 0.04 Rare B decays at the Tevatron - Moriond QCD 2007

  12. Current constraints from Dms and Bsmm are differently effective in the new physics parameter phase space • Improved limits on Bsmm can further constraint SUSY at large tanb Constraints in MFV within MSSM G.Isidori & P.Paradisi Phys. Lett. B 639 (2006) 499 Foster,Okumura,Roszkowski Phys.Lett. B641 (2006) 452 Impact on New Physics

  13. CDF/DØ similar analysis: • Normalize each signal to analogous BJ/h (J/mm) decays • Exclude J/ and ’ regions in the (mm) inv. mass spectrum • Blind optimization, sideband data used for optimization and bkg. estimate - CDF optimizes Nsig / sqrt(Nsig+Nbkg) - DØ optimizes esig / (1 + sqrt(Nbkg) ) MC B(+) m+m- h(+) Studied decay modes: CDF: B+  m+m-K+, B0  m+m-K0* CDF & D0: Bs  m+m-F (b  s l+ l-) Rare B decays at the Tevatron - Moriond QCD 2007

  14. Bu,d yields (CDF) Fit shown only for illustration purpose Bs yields 2.4 s significance Rare B decays at the Tevatron - Moriond QCD 2007

  15. BR (Bmmh) result summary • Good agreement and similar uncertainty for B-Factories & Tevatron: • Babar PRD 73, 092001 (2006) (208 fb-1 ~10 mmK+, ~15 mmK*0) • Belle hep-ex/0410006 (250 fb-1 ~40 mmK+, ~40 mmK*0) Tevatron result summary • BR(B+mmK+) = [0.60 ± 0.15(stat.) ± 0.04(sys.)]x10-6 CDF, 45 ev. • BR(B0mmK*0) = [0.82 ± 0.31(stat.) ± 0.10(sys.)]x10-6 CDF, 45 ev. • BR(Bsmmf) < 2.4 x10-6 @ 90% C.L., CDF, 920 pb-1, Bayesian approach = [1.16± 0.56(stat.) ± 0.42(sys.)]x10-6 • BR(Bsmmf) < 3.3 x 10-6 @ 90% C.L. D0, 450 pb-1, Feldman-Cousins scheme Rare B decays at the Tevatron - Moriond QCD 2007

  16. BR(BXsl+l-) B-Factories average: (1.60 ± 0.51)x10-6 Contributions to NP from neutral and charged Higgs Contribution to NP only from neutral Higgs Tevatron can contribute to squeeze the error tanb = 30 tanb = 40 L.Lu – Z. Xiao (hep-ph/0611252v2) A special NP scenario: one universal extra dimension predicted Belle CDF BK*0m+m- BaBar F.De Fazio hep-ph/0610208 Impact on New Physics

  17. 95% C.L. limits on B(Bsmm) 100 CDF D0 Branching Fraction x 107 • Bm+m-: • - Limits scale almost linearly with luminosity • - Current values entering the 10-8 territory • - First Tevatron result with almost 2 fb-1 • - Any signal at Tevatron will be evidence of NP 10 1 0.1 10 100 1000 10000 pb-1 Summary • Tevatron is demonstrated to be a good place to study B rare decays offering: • - different possibilities to constraint more and more New Physics, Bmm, bsl+l- • - a physics program complementary to the B-Factories, Bs h+ h’- • Bh+h’-: • - First observation of Bs K-p+ • - First observation of DCPV in Bs: ACP(BsK-p+) • appears to be large in agreement with expectation • bsl+l-: • - CDF/DØ beginning exploration of the bsl+l- field: • - New solid B  mmK signals from CDF; • smaller errors on BR and AFB (?) will • constrain/rule-out different NP scenarios • - A 2.4 s excess in the Bsmmfreported from CDF, • upper limit close to SM prediction • Now, over 2 fb-1 on tape: more significantly improved results coming soon Rare B decays at the Tevatron - Moriond QCD 2007

  18. Back-up slides Rare B decays at the Tevatron - Moriond QCD 2007

  19. The Tevatron at Fnal and the running experiments CDF and D0 CDF DØ Booster Tevatron CDF Run II p source Main injector and recycler Rare B decays at the Tevatron - Moriond QCD 2007

  20. Both detectors: • CDF: L00 (rinner~1.4cm) • Silicon m-vertex • DØ:L0 upgrade (rinner~1.6cm) • Central tracking in solenoid • Calorimeters and muon system • High rate trigger/DAQ [ New Solenoid, Tracking System, Si, SciFi, Preshowers • Good electron, muon ID and acceptance • Excellent tracking acceptance |h| < 2 (3) Central calorimeters Solenoid Central muon • L2 trigger on displaced vertices • [s(d0)~48 mm] • Excellent tracking resolution • [s(pT)/pT2 ~0.15% GeV-1] • Good low momentum PID T.o.f. Forward muon End-plug calorimeters Silicon tracker Drift chamber Two high performance detectors match the requirements… Rare B decays at the Tevatron - Moriond QCD 2007

  21. Strategy for the B h+ h’- analysis B • Fully exploit the selection power of the CDF L2 SVT trigger for • opposite charge track pairs originated form a displaced vertex • (a 8500 events B0(s) h+ h’- signal just after trigger selection) • Tighten trigger cuts in the offline optimization procedure • by minimizing the expected uncertainty on each individual • observable (raw asymmetry, event yield); analytical • functions used to parameterize signal and background • in the pseudo-experiments • Add the isolation cut (efficiency measured in the • B+ J/Y K+ control sample) • Evaluate the sample composition with an unbinned • Likelihood fit combining kinematics and PID • Normalize to the most abundant B0K+p- mode for BRs • Only different K+/K- interactions with material matter for correcting ACP Secondary Vertex Lxy Primary Vertex d = impact parameter B R=1 cone in the DhDF space Rare B decays at the Tevatron - Moriond QCD 2007

  22. pp invariant mass: offline confirmation of the trigger selection L2 trigger selection Rare B decays at the Tevatron - Moriond QCD 2007

  23. Separating decays modes Un-binned ML fit using 5 observables (Mpp,ptot,a,ID1,ID2) fraction of jth mode, to be determined by the fit mass term momentum term PID term (dE/dx) ptot α Signal shapes: from MC and analytic formula Background shapes: from data sidebands sign and bckg shapes from D0 K-p+ Rare B decays at the Tevatron - Moriond QCD 2007

  24. Signal composition other signals B0s→ K+K- B0→ π+π- B0→ K-π+ Contributions to Systematics Systematics ACP(B0K+p-) • dE/dx model (±0.0064); • nominal B-meson masses input to the fit (±0.005); • global mass scale(≈0); • momentum background model (±0.001); • M background model (±0.003). Rare B decays at the Tevatron - Moriond QCD 2007

  25. Pure annihilation modes • BRs small and difficult to predict • Bspp (exp. x3 larger than B0KK) Rare B decays at the Tevatron - Moriond QCD 2007

  26. First observation: 0bp- and 0bpK- 0b mass region PID variable 11  0bph- entangled to B0sK-+ Large DCPV expected for both modes 6  Ratio of BR in agreement with predictions (0.60-0.62) [Mohanta et al. Phys.Rev. D63 (2001) 074001] Rare B decays at the Tevatron - Moriond QCD 2007

  27. Bh+h-: prospects for RunII • Until the beginning of the planned Y(5S) run at Belle and the beginning of LHCb (at least fall 2008 ) only CDF has simultaneous access to B0s , B0d (plus B-baryons) • ACP(B0K) at ≈ 1% and ACP(B0sK) at ≈ 5% • High precision measurements for all BRs • Opportunity to observe annihilation modes B0KK, B0s • Measurements of BR/ACP 0bpK/p • Time-dependent ACP(t) for B0, B0sKK, all ingredients are ready Δms,εD2 ≈ 4% Rare B decays at the Tevatron - Moriond QCD 2007

  28. Discriminating observables: (almost) the same in the two experiments  Pmm DR < 1 (a <57o) 1) B vertex displacement: CDF  D0  Da   3) Isolation (Iso): Pm Pm y  x L3D 2) “pointing angle (Da)”: (fraction of tracks with pTwithin the DR=(Dh2+Df2)1/2=1 cone of the B cand.) z CDF II (780 pb-1) (300 pb-1)

  29. Search optimization: similar methods D0 CDF • Define a single signal region around • the Bs nominal mass, 180 MeV/c2 wide • B from linear extrapolation of the sidebands • Construct a likelihood ratio LR on six • discriminating observables • Pointing angle • 2D decay length significance • Isolation • B impact parameter • minimal muon impact param. • c2 vertex probability • Optimize LR on: • Define two search regions in the (mm) inv. mass spectrum around the nominal Bd and Bs masses, 120 MeV/c2 wide (±2.5 sM measured in the Bhh analysis) • Background PDF from data sidebands • construct a likelihood ratio LR using 3D proper dec. len. l, Da, Iso • Optimize LR cut on the expected a-priori 90% C.L. limit; 0.99 is the optimal value a):emm / <nup.lim.(nexp.bkg.)>  same optimal b): emm /(1+sqrt(B)) values • Evaluate the fake Bhh rate Extraction of the upper limit Bayesian approach assuming flat prior for B(Bmm) and Gaussian uncertainties

  30. Likelihood Ratio Rare B decays at the Tevatron - Moriond QCD 2007

  31. Bmm event yield after optimization Rare B decays at the Tevatron - Moriond QCD 2007

  32. B mm : area of improvement • Improved muon selection based on additional information: • Energy deposition in the calorimeter • dE/dx in the drift chamber • significant reduction in fakes expected. • Neural Net based final discriminant with additional background suppression power • use the 2-dimensional dimuon mass-discriminant plane to evaluate signal/limit Rare B decays at the Tevatron - Moriond QCD 2007

  33. Bs mm h (bs l+l-) status • Bd and B+ modes established at B-factories: • BR(B+mm K+) = 0.34+0.19-0.14 x 10-6(PDG 06) • BR(Bdmm K*0) = 1.22+0.38-0.32 x 10-6 (PDG 06) • Tevatron goals: re-establish B-factories observations and look for the unseen Bsmmf mode; predicted BR(Bsmmf)=1.6x10-6C. Geng and C. Liu, J. Phys. G 29, 1103 (2003) Strategy • Normalize signal to analogous BJ/h (J/mm) decays • Exclude J/ and ’ regions in the (mm) inv. mass spectrum • Blind optimization, sideband data used for optimization and background estimate • Monte Carlo for efficiency ratios with normalization mode • (To estimate signal efficiency for the B+, Bd modes, CDF uses data yields of Bd, B+ • in the normalization modes, scaled using the w.a. of measured BR(B+(d) mm K+(*)) ) Rare B decays at the Tevatron - Moriond QCD 2007

  34. B(+) m+m- h(+) Normalization modes Rare B decays at the Tevatron - Moriond QCD 2007

  35. Signal Selection Optimization Discriminating observables (after pre-selection cuts): Rare B decays at the Tevatron - Moriond QCD 2007

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