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Study of b -> s g and b -> d g

Study of b -> s g and b -> d g. Colin Jessop SLAC BaBar Collaboration. Conference Papers ABS864, ABS865 and ABS866 (Also on hep-ex). Physics Interest. Exclusive Measurements : B ( B -> K * g ) QCD test

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Study of b -> s g and b -> d g

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  1. Study of b -> s g and b -> d g Colin Jessop SLAC BaBar Collaboration Conference Papers ABS864, ABS865 and ABS866 (Also on hep-ex)

  2. Physics Interest Exclusive Measurements: B(B -> K*g) QCD test Acp(B ->K*g) Non SM CP violation B(B ->rg)/B(B -> K*g) Constrain Vtd/Vts Inclusive Measurements: B(b -> sg) Constrain new physics Eg spectrum from b -> sg Mass and Fermi motion of b

  3. BaBar Detector (NIM A 479, 1 2002) Strengths for b ->s,dg studies Photons from CsI Calorimeter K/p separation from DIRC Asymmetric e- (9 GeV) e+ (3.1 GeV) collisions at s =10.56GeV

  4. Event Selection - g B → K*(K+ p -)g Isolated high energy g (1.5 <Eg* < 3.5GeV) K+ Lateral profile is EM like p- Veto photons from p0/h (Un-vetoed p0/h are a significant background) Note isotropic topology

  5. Continuum(qq) Background qq, ( q =u,d,s,c) “underneath” the bb “Jet-like” topology as qq produced above threshold “shape” variables w.r.t to g e.g. cos qThrust-g,energy flow Combinations of variables, e.g Neural Net, help with two component background

  6. B(B -> K*g) and Acp(B -> K*g) DE 22.7 x106 BB (* = CMS frame) theory=hep-ph/0106081,0106067,0105302

  7. Search for B ->r,wg a g b Goal is to measure and compare to DMs/DMdB-mixing to over-constrain CKM Challenges Experiment: Theory: B(B -> rg) ~ 1/50 B(B -> K*g) r ~ 3 K* B ->K*g, b->sg, B -> rp0 backgrounds 15-35% error in Vtd/Vts extraction cf. DMs/DMd 7% error

  8. Background Rejection Continuum rejection variables (shape,DZ,flavor tag) combined in neural net. Validate with control samples. p+ eff. of 80% with K+ miss-id of 1% removes B-> K*(K+ p -/K+ p0)g bkg.

  9. B ->r,wg result Signal Estimated with Maximum Likelihood Fit (DE,MES,Mpp) Data: 84 x 106 BB pairs No Signal, 90% C.L. set a) B(B0 -> r0g) < 1.4 x 10-6 SM Theory: 0.49  0.16x10-6 0.76 +0.26/-0.23 x 10-6 DE*GeV b) B(B+ ->r+g) < 2.3 x 10-6 SM Theory: 0.85  0.32x10-6 1.53 +0.53-0.46 x10-6 c) B(B0 -> wg) < 1.2 x 10-6 SM Theory: Same as r0g (isospin sym) Analysis was performed with signal region “blinded” MES (GeV) Theory: hep-ph/0105302,0106081

  10. Unitarity triangle Combined limit: (B(B0 → r0g)= B(B0 →wg)=2.B(B+ → r+g) B(B→ rg)< 1.9 x 10-6 90% C.L Using =0.7 and DR=-0.25: Ali & Parkhomenko (Eur Phys. J. C23:89 (2002)) Implications for beyond SM in Ali & Lunghi hep-ph/0206242

  11. Inclusive b -> sg B g g b b s Xs HQET: Quark-Hadron Duality B(b -> sg) = B(B -> Xsg) Theory: NLO B(b->sg)=3.57+ - 0.30 x 10-4 (hep-ph/0207131) Phenomenological models of Eg spectrum parameterized in mb and l1. (hep-ph/9805303) Phenomenological Model of Xs fragmentation (JETSET) (hep-ph950891)

  12. If require just g bkg. ~103.Sig. Challenge is to reduce bkg while Minimizing stat.+sys.+model errors Two approaches: qq BB B -> Xsg

  13. Semi-Inclusive B -> Xsg S(exclusive states) = K+/K0s +up to 3p (1p0) , 12 states Subtract continuum with sideband X-feed and BB bkg with Monte Carlo Observe discrepency in JETSET simulation of Xs fragmentation. Efficiency from Monte Carlo weighted to correct discrepency Correct for undetected modes 1.4 < MXs < 1.6 GeV Data 22M BB MES (GeV) MXs (GeV)

  14. <Eg>=2.35 0.04 (stat.)  0.04(sys.) L=0.37 0.09 (stat.)  0.07(sys.) 0.10(theory) (Using Ligeti et.al PRD 60, 034019 (1999)) & mb=4.79 0.08 (stat.)  0.10(sys.) 0.10(theory) (Ligeti – private comm. ) Eg(GeV) Fix mb=4.79 and fit using spectrum Of Kagan & Neubert Euro.Phys. J. C 7,5(1999) B(B ->Xsg)= 4.3 0.5 (stat.)  0.8(sys.) 1.3(theory)x 10-4 MXs (GeV)

  15. L from b -> sg

  16. Fully Inclusive B -> Xsg lepton g B B Xc Xs Suppress continuum background by requiring high momentum lepton tag (Pe(Pm) > 1.3(1.55) GeV Additional shape variable cos(qeg)(cos(qmg))>-0.75(-0.7) Missing E > 1.2 GeV (Signal leptons from B → Xlu) 5% Efficiency for x1200 reduction in background The tag is uncorrelated with signal B so no model dependence

  17. Fully Inclusive B -> Xsg Model Dependence of E*g MC Expectation in 61 x 106 BB qq qq B → Xsg B -> Xsg BB BB 2.1 < Eg < 2.7 Signal Region (from considering stat+sys+model error)

  18. Fully Inclusive B -> Xsg Dominant Systematic Uncertainty is from BB bkg, subtraction BB p0/h Background Control Sample BB Background ~90% p0h ~6% hadrons in EM MC is used for BB subtraction To Test: Same Selection as Signal sample except require g to be from p0h Correct MC for integral in 2.1< E*g < 2.7 GeV by factor 0.89 ±0.17

  19. Fully Inclusive B -> Xsg 61 x 106 BB (54.6 fb-1) Continuum Subtraction with 6.4 fb-1 of “off-resonance” data BB subtraction with Monte Carlo Subtract assumed 4±1.6% b -> dg Signal Region was “blinded” B(B -> Xsg) = 3.88±0.36(stat.)±0.37(sys.)+0.43/-0.23 (theory) x 10-4

  20. Br(B->Xsg) Br(B->Xsg)

  21. Conclusions New limits on B-> r,wg , Will soon help constrain CKM  First results from BaBar on B -> Xsg New techniques for measuring B -> Xsg provides competitative B(B -> Xsg) and will improve rapidly ( < 10% soon) Experimental precision is approaching theoretical errors

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