1 / 38

Charmless B decays at CDF

Charmless B decays at CDF. Mauro Doneg à Universit é de Gen è ve on behalf of the CDF collaboration. Outline. Lot of Charmless B results… …in this talk: B hh’ (B PP) BR and Acp : B d  Kπ BR : B d  π π B s  KK B VV BR first evidence : B s    B PV

bbroyles
Download Presentation

Charmless B decays at CDF

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Charmless B decays at CDF Mauro Donegà Université de Genève on behalf of the CDF collaboration Mauro Donega – WIN05

  2. Outline Lot of Charmless B results… …in this talk: • B hh’ (B PP) • BR and Acp: Bd Kπ • BR: Bd π π Bs KK • B VV • BR first evidence:Bs  • B PV • BR and AcpB±  K ± Mauro Donega – WIN05

  3. CDF B =1.4 T TIME OF FLIGHT TOF: ~100ps resolution, 2sigmaK/ separation for tracks below 1.6 GeV/c (significant improvement of Bs flavor tag effectiveness) COT: large radius (1.4 m) Drift C. • 96 layers, 200ns drift time • Precise PT above 400 MeV/c • Precise 3D tracking in ||<1 (1/PT) ~ 0.1%GeV –1; (hit)~150m • dE/dx info provides >1.4 sigma K/ separation above 2 GeV • SVX-II + ISL: 5 + 1 (2) layers of double-side silicon (3cm < R < 30cm) • Standalone 3D tracking up to ||= 2 • Very good I.P. resolution: ~30m (~20 m with Layer00) LAYER 00: 1 layer of radiation-hard silicon at very small radius (1.5 cm) (expected 50 fs proper time resolution inBs Dsp ) Mauro Donega – WIN05

  4. Silicon Vertex Trigger Secondary Vertex B Decay Length 35m  33m = 47 m (resolution beam) Lxy Primary Vertex d = impact parameter • B physics @ hadron collider : • 2 leptons • (rare decays, charmonium decays) • 1 lepton + 1 displaced track • (semileptonic decays) • 2 displaced tracks : • (two-body decays, multibody decays) Silicon Vertex Trigger Pt(trk) >2 GeV/c Pt >5.5 GeV/c 100 m<IP(trk)<1 mm || <1 Mauro Donega – WIN05

  5. Bhh’ at CDF CDF is the first experiment to be sensitive to Bshh’ decays Physics opportunities: Counting experiments: BdK+- • Branching Ratio • Direct CP asymmetry • With higher statistics BsK-+ • Branching Ratio • Direct CP asymmetry TeVatron all b-hadrons (Bd, Bs, b…) Both Bshh’ processes and Bdhh’ Contributions from both: tree penguin Mauro Donega – WIN05

  6. Bhh’ at CDF • More than counting: • BsK+K- : • Lifetime measurement • sample sensitive to ΓL • Combined with other lifetime measurements →ΔΓs • … in the future • Bd+-→  • BdK+- →  Time dependent CP asymmetry requires b-flavor tagging and more statistics ! Mauro Donega – WIN05

  7. Bhh’ in 180 pb-1 Bdk Bskk Bd  Selection cuts Bs k Bs Bd Invariant mass  hp (GeV/c2) The only significant cut not already present in the trigger 893±47 Bhh’ events Mauro Donega – WIN05

  8. Unbinned Maximum Likelihood Fit Sum over the 4 channels BKG Likelihood BKG fraction (float) Likelihood variables: Mauro Donega – WIN05

  9. Likelihood in detail Signal likelihood j j fraction of events of the jth mode = j Kinematics Particle Identification Unbalance Momentum P(A|B)P(B) Background likelihood same structure as the signal Mauro Donega – WIN05

  10. Kinematics Invariant mass ( hypothesis) vs unbalance Def: =[1–p1/p2] q1 Helps to disentangle the BdK+-from BsK-+ M BdK-+ Bd+- Bd K+-    M BsK+- BsK-+ BsK+K-    Mauro Donega – WIN05

  11. Particle Identification e p   k Helps to disentangle Bd+- from BsK+K- • K/ separation: • 1.4 @PT>2 GeV/c • …no ev/ev PID separation • This PID performance implies statistical separation of K-pi with resolution 60% of a “perfect” PID • Background composition: • (ad-hoc study) • kaons & • pions (muons)& • protons & • electrons Mauro Donega – WIN05

  12. Fit Projections Mauro Donega – WIN05

  13. Bhh’ results BR and Acp Analyzed Luminosity =180 pb-1 Mauro Donega – WIN05

  14. Systematic uncertainties 0.01272 0.0033 will decrease with statistics 0.04755 0.0464 ±0.063 ± 0.012 ±0.019 ±0.054 Mauro Donega – WIN05

  15. Upper Limits • ΔΓs/Γs = 0.12 (Standard Model) • Bs KK = 100% short eigenstate • (HFAG2005) BR(BdK ) = 18.2 x 10-6 • (PDG 2004) fs = 0.107 fd = 0.397 Mauro Donega – WIN05

  16. BVV BPV  Bs g or g  W u,c,t  B+ K+ _ • b->sss pure penguin amplitude Bs  B±K ± • New Physics has a chance to compete! ( BfK*: “B fK* polarization discrepancy Bs   is the Bs counterpart of Bd fK* Unexpected result (3s effect) from sin(2b) measure from penguin dominated modes) • Measuring angular distribution of decay products determine polarization amplitudes and their relative phases through interference effects: • CP violation • ΔΓs • … Mauro Donega – WIN05

  17. Bs  M(kk) GeV/c2 M(kk) GeV/c2 M(kk) GeV/c2 A blind analysis was performed in anticipation of a small signal rate. • Normalize rate using another BsVV decay: BsJ/ : • NO production ratio of Bs vs Bd • (fs/fd) • one K+K- in the final state • some systematic on efficiency cancel • sizeable rate Separate optimization for Signal and Normalization sample Cuts optimized checking which of The tracks fired the trigger Mauro Donega – WIN05

  18. Bs  signal From MC From Data Bsff First observation From PDG * BR = (14 +6 -5 (stat) ± 2(syst) ± 5 (BR))  10-5 * BR(f) needs to be rescaled for fs/fd Mauro Donega – WIN05

  19. Yield and ACP (B±  K±) B±f0K± • Extended unbinned maximum likelihood fit to : • MKKK • Mf • helicity angle • dE/dx from COT mass B± K*0p Bu,dfX comb kaons pions Measure at the same time: N(B±fK±) ACP(B±fK±) ID Helicity angle + disentangle signal from B±f0K±,B± K*0p, Bu,dfX and combinatorial background Normalization: B± J/ K± Extended unbinned maximum L M Mk Mauro Donega – WIN05

  20. B±  K± Results +PDG BR(B± J/ K±) Babar/Belle results with ~100 fb-1 PDG 2004 Analyzed L =180 pb-1 Mauro Donega – WIN05

  21. Bhh’ perspectives • CDF “the present”: • Next round with ~360 pb-1 • Better tracking • Improved PID 180 pb-1 • Bhh’ the future: • Higher precision BR(BsKK) • BsKK lifetime: ΔΓs • Precision Acp(BdKπ) • (eventually1%) • Bs Kπ BR and direct Acp • Tagged time-dependent measurements further ahead: • Acp parameters for Bd and Bs 360 pb-1 Mauro Donega – WIN05

  22. B VV perspective With dataset now on tape new Bs modes should be visible (BsK*0K*0 ,Bsfr): Need significantly more statistics to perform CP measurements (…full Run II) Measure “untagged” quantities with Bsff and BdfK*events: • And other charmless decays are currently under study: • Bd(s)K*+p-(K-) • fV0 (as LbfL0 ) Mauro Donega – WIN05

  23. Conclusions • CDF is giving important contribution in the field of the charmless B decays and remains the only player in the Bs fully hadronic decays • New analysis with improved tracking and PID are already in the pipeline • Significant improvement of the TeVatron performance Mon,23 May 2005 first fb-1 was exceeded (delivered luminosity ~600 pb-1on tape) • Higher level of precision is at the door ! Mauro Donega – WIN05

  24. BACKUP Mauro Donega – WIN05

  25. TeVatron 1 fb-1 delivered Mauro Donega – WIN05

  26. Imbalance - Momentum Signal BCKG Monte Carlo Binned ML fit  p p  Mauro Donega – WIN05

  27. Systematics a) Mass resolution: the mass resolution is input from MC. It is rescaled to match the D0 resolution on data, vary the the rescale factor of ±10% and repeat the fit. b) dE/dx correlation: repeat the fit using the correlation shape extracted in the sample of kaons and pions from “mixed-events”: e.g. one meson from an event, the other from the subsequent event. Quote the difference wrt the central value. c) dE/dx shapes for e and p: repeat the fit assigning to the electrons and protons all 4 combinations of dE/dx shapes (ep)= (/K/KK/K). Quote the maximum difference wrt the central fit. Mauro Donega – WIN05

  28. Systematics (cont’d) d) input masses: the fit is done on data in which the recipe used for mass measurement at CDF II was applied. Input masses in the kinematics pdf are those measured by CDF II. Repeat the fit varying M(Bd) and M(Bs) within their statistical uncertainties (0.92 and 1.29 MeV/c2). Quote the differences wrt the central fit e) Background model: the fit assumes mass spectrum of bckg = exp + C. Repeat the fit with p1,p2,p3 and quote the difference wrt central value Mauro Donega – WIN05

  29. Systematics (cont’d) f) Different p-spectra for bckg components: central fit assumes the same momentum distribution for e/pi/K/p of background. Reweight each term of the bckg p.d.f. according to linear fits of populations vs momentum plots. Mauro Donega – WIN05

  30. Systematics (cont’d) g) B lifetimes: relative kinematics efficiencies depend on the lifetime assumed in MC. Re-evaluate efficiencies after simultaneous shift of Bs lifetime (+1) and Bd (-1) and viceversa.  is the PDG2004 uncertainty. Quote difference wrt central value h) Isolation efficiency: has a ~ 10% from measurement on data. Re-evaluate the efficiency at +/- 1  and quote difference wrt central value i) MC statistics: kinematics efficiencies have statistical error. Re-evaluate them at +/- 1  and quote difference wrt the central fit. Mauro Donega – WIN05

  31. Systematics (cont’d) l) Charge asymmetry: assess +/-25% of the 10% charge-asymmetry effect studied in the published D0 analysis m) XFT bias correction: the correction function have uncertainties. Stretch (push) K/ discrepancy shifting simultaneously the correction coefficients by 1 , reevaluate the correction, and quote differences wrt the central fit n) pT(B) spectrum: Bs and Bd spectra are different, in principle, but use MC with an “average” spectrum. Created an additional “shrunk” spectrum by shifting by –1% each entry in the pT(B) histogram used in central fit. Extract weights from the ratio of the two spectra, apply to MC events; re-evaluate the relative efficiencies. Mauro Donega – WIN05

  32. Systematics (cont’d) o) ΔΓs/Γs: Standard Model predicts ~ 0.12±0.06 and Bs→K+K- to be dominated by the short-lived component. We derive the systematic uncertainties from these assumptions by varying ΔΓs/Γs from 0.06 to 0.18 , re-evaluating the relative efficiencies and quoting the differences wrt the central fit. Mauro Donega – WIN05

  33. Systematic uncertainties will decrease with statistics Mauro Donega – WIN05

  34. Hint of discrepancy with SM in bs penguin decays • Measure sin(2b) using golden charmonium modes (i.e. BdJ/KS0)from mixing induced time dependent CP asymmetry B0fK0 and B0’K0 theorethically clean! • Unexpected result (3s effect) when measuring sin(2b) from penguin dominated modes Mauro Donega – WIN05

  35. Bbackground Due to the large width of K* and to its value close to mφ we get in our Bs signal window a reflection from BdJ/ψ K* for BsJ/ψ φ and from Bdφ K* for Bsφφ We get an estimate of this contribution by evaluating from MC the efficiency of reconstructing a BdJ/ψ K* event as BsJ/ψ φ and from the measured BRs and fs/fd. As a cross-check we can evaluate the contribution from the sidebands subtracted mass spectrum of the φ meson, in which the only remaining source of background comes from the BdJ/ψ K* reflection that doesn’t enter the Bs sidebands region Mauro Donega – WIN05

  36. BR(Bs  ) systematics • Systematic error dominated by normalization mode BR uncertainty and already similar in size to the statistical error • Theory uncertainty on polarization very conservative (vary longitudinal fraction in 20 % to 80% range as suggested by A. Kagan) • DGs uncertainty based on the preferred theory value of: DGs/Gs = 0.12 ± 0.06 • BR is rather on the low side respect to QCDF (2.5 s) 1.4 vs 3.7 E-5 Mauro Donega – WIN05

  37. BR(B±  K±) systematics • Systematic error on BR dominated by fit uncertainty and acceptance correction, largely below statistical uncertainty • ACP systematic is largely statistical in nature, intrinsic systematic below 0.01 • Comparable to B-factory experiments Mauro Donega – WIN05

  38. Further Bs modes • Rich harvest of interesting Bs VV decays (Li,Lu,Yang hep-ph/0309136) • Only the p0-less shown in the table here • Measure them all! • K*+K*-/K*0anti-K*0 untagged angular analysis gives g (with SU(2) assumptions) (Fleisher,Duniets) • fr0 dominated by Electro Weak Penguin (insight in to the BpK puzzle!) bd bs Pure penguin Trigger efficiency not included (but expected very similar) Mauro Donega – WIN05

More Related