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Radiative and Rare B-Decays at BaBar All results are preliminary unless journal ref. is given limit values are 90% CL unless otherwise specified Carsten.

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Presentation on theme: "Radiative and Rare B-Decays at BaBar All results are preliminary unless journal ref. is given limit values are 90% CL unless otherwise specified Carsten."— Presentation transcript:

1 Radiative and Rare B-Decays at BaBar All results are preliminary unless journal ref. is given limit values are 90% CL unless otherwise specified Carsten Hast, SLAC for the BaBar Collaboration Pittsburgh, October 17

2 Beauty 2003, October 17thCarsten Hast, SLAC2 Overview Since this talk is nicely framed between a theoretical introduction and a Belle summary and outlook I will focus on newer results and analysis techniques from BaBar FCNC b  K Purely Leptonic Decays b   b   b  Kll and b  K*ll B  X s ll Radiative Decays B 0  K 2 *0 (1430)  and B+  K 2 * + (1430) 

3 Beauty 2003, October 17thCarsten Hast, SLAC3 DIRC  PID) 144 quartz bars 11000 PMs 1.5 T solenoid EMC 6580 CsI(Tl) crystals Drift Chamber 40 stereo layers Instrumented Flux Return iron / RPCs (muon / neutral hadrons) Silicon Vertex Tracker 5 layers, double sided strips e + (3.1 GeV) e - (9 GeV) SVT+DCH:  (p T )/p T = 0.13 %  p T + 0.45 %, good dE/dx DIRC: K-  separation 4.2  @ 3.0 GeV/c  2.5  @ 4.0 GeV/c EMC: Very good electron identification and  0 reconstruction IFR: Decent muon identification The BaBar Detector

4 Beauty 2003, October 17thCarsten Hast, SLAC4 On(off)-peak Run 1+282 (10)fb -1 Run 331 (4) fb -1 Run 46 (0)fb -1 Best Peformance PEPII peak Luminosity: 6.582x10 33 cm -2 sec -1 Integrated Luminosity Shift: 135.2 pb -1 in 24 hours: 391.2 pb -1 124.1  10 6 BB 89.7  10 6 BB 82 fb -1 on-peak data for analysis PEP- II Lumi Performance and Recorded BaBar Lumi

5 Beauty 2003, October 17thCarsten Hast, SLAC5 e + e -  (4S)  BB B produced almost at rest in  (4S) frame For B decay with no missing particles use beam energy to constrain mass and energy of the reconstructed B background signal background 0 for signal m B for signal  E and m ES provide uncorrelated measurement of energy and mass Standard Variables in  (4S) Frame

6 Beauty 2003, October 17thCarsten Hast, SLAC6 The best upper limits (@90% CL): –CLEO:Br (B  K )  2.4  10 –4 –B A B AR : Br (B  K )  9.4  10 –5 Semi-Leptonic B-tags: B  Dl X (X  ,  0 or nothing) 50.7 fb -1 New search (80 fb -1 ) with hadronic B-tags hep-ex/0207069 PRL 86 2950 (2001)      Search A rare flavour changing neutral current (FCNC) b  s decay SM prediction: Br (B  K )  4  10 –6 Summed over all neutrino species B   D 0 (*) (   ) (K  ) (K 0 s ) (  0 ) (D*  D 0  and D 0  K , K  0, K3 , K s  ) B constraining kinematic variables:  E and m ES

7 Beauty 2003, October 17thCarsten Hast, SLAC7 Identify tag B in signal  E and m ES area All remaining tracks and neutrals belong to the recoiling signal-side B One well identified Kaon no  0 Missing momentum not in the beam pipe “extra” Energy < 300 MeV Data B  K MC B + B  MCB 0 B 0 MCcc MCu,d,s MC      Search II

8 Beauty 2003, October 17thCarsten Hast, SLAC8      Upper Limit Selected events: 3 Expected background events: 2.7  0.8 Br ( B  K ) < 1.05  10  4 @ 90% CL hep-ex/0304020 Br ( B  K ) < 7.0  10  5 @ 90% CL Combining this result with the previous, (Br (B  K )  9.4  10–5) statistically independent BABAR result, yields a new limit: Going to PRL

9 Beauty 2003, October 17thCarsten Hast, SLAC9 Semi  Leptonic B-tag B  Dl X Hadronic B-tag B  DX had 2 analyses of the 1999-2002 data sample: ~81 fb  1 Reconstruct one B meson as The remaining neutrals and tracks are signal candidates The two samples of tag B mesons are statistically independent   (e,  ) (e,  )    (e,  ) (e,  )   ( ,  0,  )   ( ,  0,  )  very clean but low efficiency (~ 0.25 – 0.30 %)    Search

10 Beauty 2003, October 17thCarsten Hast, SLAC10     event veto Only one charged track having low impact parameter Track is not identified as a kaon Track is an identified lepton Residual neutral energy is used to model PDFs to extract signal and background contributions Three preselections 1 track, 0  0 1 track, 1  0 3 tracks, 0  0 Track is not identified as a kaon Track is identified as lepton or pion Additional cuts on Missing momentum Residual neutral energy Track momentum Invariant masses Background mainly from V cb events Signal efficiency: 11.3%Signal efficiency: 11.3% Signal efficiency: 22.5%Signal efficiency: 22.5% Semi  Leptonic B-Tag Hadronic B-Tag SignalBackground E left (GeV) Events/0.07 GeV  Signal Selection

11 Beauty 2003, October 17thCarsten Hast, SLAC11 Br ( B     ) < 7.7  10  4 hep-ex/0303034 hep-ex/0304030 Semi  Leptonic B-Tag Hadronic B-Tag E left (GeV) Events/0.07 GeV Br ( B     ) < 4.9  10  4 47.7  7.0 Observed events onpeak data 39.9  2.8 Expected Bkg in onpeak data (sideband extrapolation) 40.9  3.8 Expected Bkg from MC 35 37.6  4.7  1.5 All 10 8 6 7 4 6.7  2.0  0.6 5.0  1.7  0.4 11.2  2.5  0.5 10.4  2.6  1.2 4.3  1.4  0.3  e e        0    Data candidates Total BkgSelection    Results Br ( B     ) < 4.1  10  4 @ 90% CL SM prediction: < 9.2  10  5 Combined limit hep-ex/0305034

12 Beauty 2003, October 17thCarsten Hast, SLAC12    Search B rest frame CM frame Signal Monte Carlo Data sample 1999–2002: ~81fb –1 Two Body decay  p(  ) ~ m B /2 One well identified muon All the rest is from the companion B –do particle identification –No additional leptons allowed After the companion B was found, p(  ) is re-reconstructed in the signal B rest frame

13 Beauty 2003, October 17thCarsten Hast, SLAC13 All other tracks and neutrals make the Companion-B    Search Signal Monte Carlo

14 Beauty 2003, October 17thCarsten Hast, SLAC14 Signal Selection efficiency: 2.09% Selected events: 11 Expected background: 5.0 Bg fluctuation prob. to the signal: 4% Data B  MC Signal box Sideband B ( B   ) < 6.6  10  6 @ 90% CL @ 90% CL BABAR-CONF-03-007 +1.8  1.4 Upper Limit for    Data

15 Beauty 2003, October 17thCarsten Hast, SLAC15 b   K (*) l l Reconstruct K +, K s   +  -, K *0  K +  -, K *+  K s  + Lepton identification for e + e - with p(e) > 0.5 GeV/c,  +  - with p(  ) > 1.0 GeV/c penguin diagram b  s llbox diagram b  s ll Updated result on 113 fb -1 accepted by PRL

16 Beauty 2003, October 17thCarsten Hast, SLAC16 b   K (*) l l Peaking Background Events with the same final state: B  J/  K (*),  ’ K (*) Signal is scattered in this above area 500 fb -1 B  J/  K(*),  ’ K(*) Monte Carlo little to no contribution outside these veto bands J/  veto  ’ veto M ll [Gev/c 2 ]  E [GeV]

17 Beauty 2003, October 17thCarsten Hast, SLAC17 b   K (*) l l Peaking Background II Background from lepton miss-identification B  h + h - K (*) m ES [Gev/c 2 ] # Events h + h - K (*) events in data convolved with rates for h to fake e,  0.01 events 0.33 events Included as part of the fit to data

18 Beauty 2003, October 17thCarsten Hast, SLAC18 b   K l l Results 2-D unbinned maximum LH fit to m ES and  E on all 4 decays K + ee/  and K s 0 ee/  Br(b  K ll) = (6.5 +1.4 -1.3 +/- 0.4 ) 10 -7 8.4  excess over background accepted by PRL

19 Beauty 2003, October 17thCarsten Hast, SLAC19 b   K* l l Results 3-D unbinned maximum LH fit to m ES,  E and m K  Br(b  K* ll) = (8.8 +3.3 -2.9 +/- 1.0 ) 10 -7 3.3  excess over background Constrain: K*ee = 1.33 X K*   tot (B 0 ) = 1.08 X  tot (B + ) accepted by PRL

20 Beauty 2003, October 17thCarsten Hast, SLAC20 b   K ( * ) l l Results Comparison of m ll in data with simulation, normalized to the measured Br Fits well

21 Beauty 2003, October 17thCarsten Hast, SLAC21 Semi-Inclusive B   Xs l l Sum of exclusive modes approach: reconstruct X s with 1 K ± or K 0 s   +  -, # (   +  0 )  2, #  0  1 10 modes, ~50% of BR(B  X s l + l - ) (75% if assumed K S =K L ) Similar analysis as b  K ( * ) ll but with higher combinatoric background B  Xs e + e - B  Xs  +  - m ES [Gev/c 2 ]

22 Beauty 2003, October 17thCarsten Hast, SLAC22 Semi-Inclusive B   Xs l l Results ModeN sig (  stat) Signifi- cance (stat) Effici- ency B  X s e  e  29.0  8.3 4.02.5% B  X s     12.4  6.2 2.21.2% Sum 41.4  10.3 4.6 Br(B  X s e  e  ) = (6.6  1.9  1.9 1.6 ) 10  6 Br(B  X s     ) = (5.7  2.8  1.7 1.4 ) 10  6 Br(B  X s l  l  ) = (6.3  1.6  1.8 1.5 ) 10  6 + Data Monte Carlo

23 Beauty 2003, October 17thCarsten Hast, SLAC23 Br (B 0  K 2 * 0 (1430)  ) BaBar (12.2 +/- 2.5 +/- 1.1)10 -6 (14.4 +/- 4.0 +/- 1.3)10 -6 Belle ( 13 +/- 5 +/- 1) 10 -6 Cleo (16.6 +/- 5.9 +/- 1.3) 10 -6 B 0  K 2 * 0 (1430)  and B +  K 2 * + (1430)  Br (B +  K 2 * + (1430)  ) BaBar Preliminary

24 Beauty 2003, October 17thCarsten Hast, SLAC24 Summary (1) FCNC b  K  3 bg events expected 3 seen Purely Leptonic Decays b   difficult b   looks quite interesting Radiative Decays B 0  K 2 *0 (1430)  and B+  K 2 * + (1430)  BaBar is in the game

25 Beauty 2003, October 17thCarsten Hast, SLAC25 B   s l l Summary Next step: measure angular and kinematic distributions …and have fun with the next talk covering all the other interesting rare results measured by Belle Br(b  s ll) in good agreement within experiments and prediction

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