1 / 16

Measurement of the Amplitude Ratio of B 0  J/  K *0 to B 0  J/  K *0 (K +  - ) decays

Measurement of the Amplitude Ratio of B 0  J/  K *0 to B 0  J/  K *0 (K +  - ) decays. Max Baak NIKHEF, Amsterdam For the BaBar Collaboration APS Meeting Philadelphia, 8 April 2003. Two simple concepts. Wrong-flavor decay. ?. B 0  J/ K * 0 B 0  J/ K * 0. ( ).

oakes
Download Presentation

Measurement of the Amplitude Ratio of B 0  J/  K *0 to B 0  J/  K *0 (K +  - ) decays

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. Measurement of the Amplitude Ratio of B0 J/ K*0to B0 J/ K*0 (K+-) decays Max Baak NIKHEF, Amsterdam For the BaBar Collaboration APS Meeting Philadelphia, 8 April 2003 Max Baak

  2. Two simple concepts Wrong-flavor decay ? • B0  J/ K * 0 • B0  J/ K * 0 ( ) ( ) Right-flavor decay 1 • B0  J/ K * 0 • B0  J/ K * 0 ( ) ( ) To tag a K*,use charge of kaon and pion 2 Max Baak

  3. Can sin2ßSand sin2ßL be different? BaBar data • Time-dependent asymmetry for B0 J/ KS,L normally given by • - • sin2ßS = sin2ßL • Can sin2ßSand sin2ßL be different? • - SM corrections: (sin2ßS- sin2ßL) ~ 0.01 • - Experimental limit: 0.02 ± 0.17 • How to find wrong-flavor decays if K0 and K0 mix into CP states? •  Use B0 J/ K*0 sample! Same quark-level process. Tag with K*0 K+-. Grossman, Ligeti, Kagan Phys.Lett.B538:327 Observed asymmetry sin2S = 0.741  0.067 For differentsin2ßSand sin2ßL, need non-zero wrong-flavor decay amplitudes (New Physics) sin2L = 0.723  0.158 Max Baak

  4. B  J/ K*0 time dependent analysis B0 Flavor eigenstate With wrong- flavor decays Flavor eigenstate B0(t) B0(t) J/K*0 J/K*0 For final state J/ K*0 replace C  -C , S  -S . Initialstate Initialstate B0 a) a) b) b) J/K*0 B0 Standard Model Wrong-flavor Extract wrong-flavor to right-flavor amplitude-ratios  and  from time-dependent fit to B0/B0  J/ K*0 and B0/B0  J/ K*0 =0C=1, S=0 (standard B0B0 mixing) B0 a) unmixed b) mixed No wrong- flavor decays Max Baak

  5. BaBar Detector Electromagnetic Calorimeter 6580 CsI(Tl) crystals 1.5 T solenoid e+ (3.1 GeV) Cerenkov Detector (DIRC) 144 quartz bars 11000 PMs e- (9 GeV) Drift Chamber 40 stereo layers z Silicon Vertex Tracker 5 layers, double sided strips SVT: 97% efficiency, 15 mm z hit resolution (inner layers, perp. tracks) SVT+DCH:(pT)/pT= 0.13 %  pT+0.45 % DIRC: K- separation 4.2  @ 3.0 GeV/c  2.5  @ 4.0 GeV/c EMC:E/E = 2.3 %E-1/4 1.9 % Max Baak

  6. K-p separation with Cerenkov Detector (DIRC) • Good kaon-pion separation essential to distinguish between K*0K+- and K*0 K-+ • BaBar uses DIRC: Čerenkov light in quartz  angle qc handle on particle ID >9s K/p separation s(qc)  2.2 mrad Momentum range of K and  from K* < 3 GeV Max Baak

  7. Analysis Technique At time of BTAG decay, the 2 B’s are in opposite flavor states K+ Tag B sz ~ 110 mm J/Y Reco B sz ~ 65 mm z U(4s) Dz K*0 gbctB@ 260 mm bg = 0.55 Dt @Dz/gbc Determine flavor of other B meson BTAG (“tagging”) Fully reconstruct B mesonin state J/Y K*0 or J/Y K*0 Reconstruct vertex of BTAG and compute proper time difference Dt Max Baak

  8. Dt distribution of mixed and unmixed events realistic mis-tagging & finite time resolution perfect flavor tagging & time resolution w Bflav Mixing pdf Res w J/Y K* pdf (similar for J/Y K*) D(*) , , a1 sample (Bflav) determines mistag fraction w and resolution function Max Baak

  9. Data Sample [1999-2002]: 82 fb-1 on U(4s) Resonance 3s cut on DE applied signal region E [MeV] ‘tight’ kaon selection mES [GeV/c2] Max Baak

  10. Likelihood Fit • Combined unbinned maximum likelihood fit to Dt spectraof B-flavor and J/Y K*0 and J/Y K*0 samples. • Analysis performed blind. • All Dt parameters extracted from data • Correct estimate of the error and correlations 48 total free parameters Fit Parameters C,S,C,S 4 Mistag fractions for B0 and B0 tags 12 Signal resolution function 8 Empirical description of background Dt 24 B lifetime fixed (PDG 2002 value) tB= 1.542 ps Mixing Frequency fixed (PDG) Dmd = 0.489 ps-1 tagged J/Y K* tagged flavor sample Max Baak

  11. K- swapping WARNING! Fake wrong-flavor decays!Need to minimize this effect mixed up on wrec occasions (assuming C, C and S, S are of equal size) Determined using MC • To lowest order sine terms not affected, but cosine terms are. • Doubly mis-IDing both K+ and - for each other fakes a K*0 for a K*0 - From MC: double mis-ID rate wrec = 0.3 % • Effect of K- swapping on time-dependent decay distributions? Max Baak

  12. Result C = 1.045 ± 0.058 (stat) ± 0.034 (syst) S = -0.024± 0.094 (stat) ± 0.039 (syst) C = 0.966 ± 0.051 (stat) ± 0.034 (syst) S = 0.004± 0.090 (stat) ± 0.039 (syst) a) unmixed Entries / 0.6 ps b) mixed c) asymmetry Asymmetry See my next talk! t (ps) Max Baak

  13. Conclusion • No sign for wrong-flavor decays B0 J/ K*0 and B0 J/ K*0 • Using the relations: Measured values Standard Model • To be submitted to PRL. 1 2 3 Assuming common wrong-flavor decay amplitudes for B0 J/ K*0 and B0 J/ K*0 Max Baak

  14. Backup Slides Max Baak

  15. Cerenkov Particle Identification System (DIRC) • Good kaon-pion separation essential to distinguish between K*0K+- and K*0 K-+ • DIRC: Čerenkov light in quartz K- separation > 4  for this analysis Transmitted by internal reflection Rings projected in standoff box Detected by PMTs Essential for Kaon ID >2 GeV Max Baak

  16. B Flavor Tagging Methods • In BaBar tagging is handled with Neural Nets • Information used: Primary lepton Secondary lepton Kaon(s) Soft pions from D* decays Fast charged tracks Mistag fraction w determined with flavor eigen-states sample Bflav (23.7k events, purity 82%) Smallest mistag fraction The errors on C,S,C,S scale with quality Q Max Baak

More Related