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L b Physics at CDF

L b Physics at CDF. Shin-Shan Yu University of Pennsylvania for the CDF Collaboration Frontiers in Contemporary Physics –III, May 23-28, 2005. Outline. L b. Why L b CDF Detector, Trigger Previous L b Results Lifetime and Mass: L b  J/ L Branching Fractions:

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L b Physics at CDF

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  1. LbPhysics at CDF Shin-Shan Yu University of Pennsylvania for the CDF Collaboration Frontiers in Contemporary Physics –III, May 23-28, 2005

  2. Outline Lb • Why Lb • CDF Detector, Trigger • Previous Lb Results • Lifetime and Mass: Lb  J/ L • Branching Fractions: Lb  J/ L , Lb  pK, pp, Lb  Lc p • New Results • Branching Fractions: Lb  Lc p, Lb  Lc mn • First Observations: Lb  Lc*mn, Lb  Sc pmn Lb  Lcppp • Future Shin-Shan Yu

  3. Big Picture : Why Lb baryon? u d b This is all we know about Lb … Now, Fermilab Tevatron is the only facility that produces Lb and allows us to study Lb. Shin-Shan Yu

  4. HQET and HQE ud q b • Heavy Quark Effective Theory and Heavy Quark Expansion • HQET and HQE predict the b-hadron mass, branching fractions and lifetime • Assuming mb >> LQCD, the 3-body dynamics is reduced to 2-body • heavy vs. light system. • The b quark can be treated the same way as the nucleus in the atom. • Little interaction between the heavy and light system. • Relate the b-hadrons of different flavors • Difference of b-hadrons are expressed in the power of and • Spin of di-quarks = 0, sub-leading order corrections are simpler than • those of B mesons. Measuring Lb mass, branching fractions, and lifetime tests HQET and HQE independently from the B mesons. Shin-Shan Yu

  5. CDF Detector • Solenoid • 1.4Tesla • Silicon Tracker • || < 2 • svertex ~ 30 mm • Central Outer Tracker (COT) • 96 layers drift chamber, up to ||~1 • sPT/PT~ 0.15% PT • Particle ID with dE/dx • Time of Flight • Particle ID of low momentum tracks • Muon chamber • 4 layers drift chamber outside the calorimeter • || < 1 Shin-Shan Yu

  6. B Physics &B Triggers • Huge production rates, 1000 times higher than ate+e-  (4S) • (pp  bX, |y| < 0.6) = 17.6  0.4 (stat.)  2.5 (syst.) bPRD 71, 032001 • Heavy states produced • B0, B+, Bs, Bc, b, b • Backgrounds are also3orders of magnitude higher • Inelastic cross section 100 mb • Challenge is to pick one B decay from ~103 QCD events • Di-muon trigger(lifetime, mass, branching ratios) • pT() > 1.5 GeV/c, within J/Y mass window • Two displaced-tracks trigger(branching ratios) • pT > 2 GeV/c, 120 m ≤ d0≤ 1 mm,Lxy> 200 m, S pT > 5.5 GeV/c • Lepton + displaced-track trigger(lifetime, fbaryon) • pT(,e) > 4 GeV/c, 120 m ≤ d0≤ 1 mm, pT > 2 GeV/c CDF Run II Preliminary Tracks/10 mm • Beam=33 mm Silicon Vertex Trigger Impact Parameter (cm) Shin-Shan Yu

  7. Previous Lb Results

  8. Lifetime, Mass, and Branching Fractions • First measurement of t(Lb) in a fully reconstructed mode Lb  J/ L • dimuon trigger data t = 1.25  0.26  0.10 ps • To be compared with the 2004 world averaget = 1.229  0.080 ps • Best single mass measurement Lb  J/ L • dimuon trigger data M= 5619.7  1.2  1.2 MeV/c2 • To be compared with the 2004 world averageM= 5624.0  9.0 MeV/c2 • Relative BR • dimuon trigger data • To be compared with the Run I result Ratio= 0.27  0.12 (stat)  0.05 (syst) • Best upper limit on Lb charmless decays • two displaced track trigger data B(Lb→ pK+pp) < 2.2 x 10-5 at 90% C.L • To be compared with the 2004 world averageB(Lb→ pK+pp) < 5.0 x 10-5 at 90% C.L Shin-Shan Yu

  9. Branching Fraction LbLcpLc p+ K-p+ • Data come from two displaced track trigger • Background shapes obtained from Monte Carlo simulation: mis- or partially reconstructed b-hadron decays Shin-Shan Yu

  10. New Results

  11. Why B(LbLcmu)/B(LbLcp) ? • Similar Feynman diagrams. Theorists relate hadronic BR to easier and calculable semileptonic BR by factorization. • Differential semileptonic decay width is related to 6 form factors, reduced to one in HQET • Close form of z(w) can be obtained using Large Nc Limits, QCD Sum Rules, and etc. • Predictions of Jenkins(Nucl. Phys. B396, 38), Huang, et al. (hep-ph/0502004) and • Leibovich, Ligeti, Stewart, Wise (Phys. Lett. B586, 337) give a ratio of 15 with 10-30% error Shin-Shan Yu

  12. How B(LbLcmu)/B(LbLcp) ? • If hadronic BR is known, we can get Vcb from the semileptonic BR. • Four charged tracks in the final state • Control samples: similar decays in the B meson system • and • Relative BR is the yield ratio corrected for the efficiency, e.g: • But since we can not reconstruct neutrinos, several backgrounds can fake our semileptonic signals in the data …. Shin-Shan Yu

  13. Control SampleB0 D*X, D*+ D0p+, D0 K-p+ Hadronic Signal Inclusive Semileptonic Signal Shin-Shan Yu

  14. Control SampleB0 DX, D+ K-p+ p+ Inclusive Semileptonic Signal Hadronic Signal Shin-Shan Yu

  15. Signal SampleLbLcXLc p+ K-p+ Inclusive Semileptonic Signal Hadronic Signal Shin-Shan Yu

  16. MC and Data Comparison • We used MC to obtain relative efficiencies of signals and backgrounds. • Compare MC and background subtracted signal distribution in the data. • Tune our MC if MC and data disagree, e.g: pT of b-hadron, M(Lcm) Shin-Shan Yu

  17. Where Are the Semileptonic Backgrounds From? • Background signature: a (charm, muon) in the final state and passes our selection cuts • Physics Background • Muon Fakes • QCD Shin-Shan Yu

  18. Physics Background • Physics Background • b-hadron decays into a charm, a m and additional particles, e.g: • Reduced by the M(Lcm) cut • Normalize the amount to the measured hadronic signal • BRs come from PDG, theoretical estimate and preliminary measurements • 10~40% contribution Shin-Shan Yu

  19. First Observation ofLb  Lc*mn, Lb  Scpmn CDF Run II Preliminary 360 pb-1 Sc++ CDF Run II Preliminary 360 pb-1 CDF Run II Preliminary 360 pb-1 Sc0 Lc(2625) Lc(2593) Lc(2625) Lc(2593) • First observation of several Lb semileptonic decays that can fake the signal • Estimate the BR based on the observation Sc++,+,0 Shin-Shan Yu

  20. How to ObtainB(Lb  Lc p)? • Make use of previous CDF measurements • However, a Lb MC PT spectrum using fully reconstructed decay was not available for CDF I • Correct the CDF I fbaryon/fd using measured PT spectrum • Acceptance correction • Different PT thresholds affect the ratio: 10 GeV/c vs. 6 GeV/c Consistent with the prediction 0.45% (Phys. Lett. B586, 337) Shin-Shan Yu

  21. Muon Fakes m • Muon fakes • p, K, p fake muons • ct and muon d0 cuts suppress fakes from the primary vertex • Our fakes mostly come from b decays. • Weight “charm+TRKfailm” events with muon fake prob. • Fit the weighted mass • ~5% contribution Shin-Shan Yu

  22. QCD Pair Production • QCD: • charm and m come from different b- or charmed hadrons • b, c quarks are pair produced and fragmented into two hadrons • Suppressed due to the ct and PT(m) cuts • Rely on Pythia MC • Most sensitive to gluon splitting • Compare data and MC single hadron production -> 10~40% difference • 1~2% contribution Shin-Shan Yu

  23. Semileptonic Background Summary Shin-Shan Yu

  24. Relative BR with Statistical Uncertainty Shin-Shan Yu

  25. Systematics • Physics background and hadronic signal branching fractions • Measured: from PDG • Estimated or Unmeasured • 5% forcharm decays • 100% for b-hadron decays • Mass fitting model • Vary the constant parameters in the fit • Several background shapes come from inclusive MC • vary BR of the dominant decays • Muon fake estimate • Data sample size for the measurement of muon fake probability • Uncertainty of the proton, kaon, pion fractions in the hadron tracks • MC modeling of acceptance and efficiency • pT spectrum • muon reconstruction efficiency scaling • QCD process • detector material • Lc Dalitz structure, Lb lifetime, Lc and Lb polarizations • Lb semileptonic decay model Shin-Shan Yu

  26. Uncertainty Summary Shin-Shan Yu

  27. Control Sample Result Consistent with the 2004 world average 7.81.0 at the 1s level Consistent with the 2004 world average 19.71.7 at the 0.7s level New world average ratio 8.3  0.9 New world average ratio 19.1  1.4 Shin-Shan Yu

  28. Signal Sample Result • Experimental Uncertainties • dominated by: • Data sample size • Measured BR B (LbLcp) • Reminder: physics backgrounds are normalized to hadronic signal • Dominated by the uncertainties on the production cross-section and • B(Lc->pKp) Leibovich Ligeti Stewart Wise Shin-Shan Yu

  29. B(Lb  Lc mu)? Combined the ratio of BR and B(Lb Lcp), we have Consistent with DELPHI result (Phys. Lett. B585, 63) Weighted average Also in agreement with the theoretical prediction 6.6% (Phys. Lett. B586, 337) • |Vcb| Exercise • Plug in the weighted average and the theoretical slope parameter of the ISGW function into the formula for B (LbLcmu) Consistent with the |Vcb| from DELPHI measured with B->D*lu decays (Eur. Phys. J C33, 213) Shin-Shan Yu

  30. First Observation ofLb  Lc p p p • Data come from two displaced track trigger • Lc p p Dalitz structure study in progress Shin-Shan Yu

  31. Conclusions Previous Lb Results • First time Lb lifetime is measured in a fully reconstructed decay • Best single mass measurement • Improved upper limit of B(Lb→ ph) by more than a factor of 2 • First unambiguous signal of LbLcp • First measurement of New Results • First measurement of • Both ratio and absolute BRs are in agreement with the prediction • First observation of Lb  Lcppp, Lb  Lc*mn, Lb  Sc pmn Shin-Shan Yu

  32. What Do We Know AboutLb Now? Mass m = 5619.9  1.7 MeV/c2 (4.1  2.0) x 10-3 Lc l u (5.5  1.8) % pK + pp < 2.2 x 10-5 Lc+p- p- p+seen Lc(2593) +l u seen Lc(2625)+l u seen Sc++p-l u seen Sc0p+l u seen Shin-Shan Yu

  33. Future • Most analyses are still statistically limited, more data in the future will improve the result • Lb  J/ Llifetime analysis with 5x data expected • TOF+dE/dx combined PID will be used in the search for Lb→ ph • fbaryon/fd using the lepton+displaced track trigger data anticipated • Lifetime and branching fraction measurement from Lb  Lc p p p • Lb  Lc mn form factor • Lb polarizations Shin-Shan Yu

  34. Back Up Slides

  35. Tevatron & CDF Luminosity Collider Run II Peak Luminosity Year 2001 2002 2003 2004 2005 Month 4 7 10 1 4 7 10 1 4 7 10 1 4 7 10 1 4 • Record peak luminosity • 1.27 x 1032 sec-1 cm-2 • May12, 2005 • ~775 pb-1 on tape (Run I  100 pb-1) • ~400 M events from the displaced track trigger ~975 pb-1 delivered ~775 pb-1 to tape Shin-Shan Yu

  36. Lifetime Lb J/LJ/m+m-, L p+p- ct=374 78 (stat)  29 (syst) mm 46 9 signal candidates CDF II t(Lb) = 1.25  0.26 (stat.)  0.10 (syst.) ps 2004 World average t(Lb)=1.2290.080ps CDF Run I • First measurement of t(Lb) in a fully reconstructed mode dimuon trigger data LbLcln (Lc  pKp) t = 1.33  0.15  0.07 ps Shin-Shan Yu

  37. Mass Lb J/LJ/m+m-, L p+p- CDF II M(Lb) = 5619.7  1.2 (stat.)  1.2 (syst.) MeV/c2 2004 World average M(Lb) =5624.09.0MeV/c2 CDF Run I • Best single mass measurement Data come rom the dimuon trigger • Calibrate mass with the J/Y sample Lb mass = 5621.0  4.0  3.0 MeV/c2 Shin-Shan Yu

  38. Branching FractionLb J/LJ/m+m-, L p+p- CDF Run I • Data come from the dimuon trigger • Pion from the L is soft, can not rely on the MC to get the tracking efficiency for pT < 0.5 GeV/c. • studied by embedding simulated signal hits in the J/y data. Shin-Shan Yu

  39. Search for Lb pK, pp CDF II B(Lb→ pK+pp) < 22 x 10-6 at 90% C.L PDG 2004 B(Lb→ pK) < 50 x 10-6 at 90% C.L PDG 2004 B(Lb→ pp) < 50 x 10-6 at 90% C.L • Data come from two displaced track trigger • Mohanta, Phys. Rev. D63:074001,2001 Prediction: • B(Lb→ pK)=(1.4~1.9)×10-6 • B(Lb→ pp)=(0.8~1.2)×10-6 • compare to B(B0→Kp)= (18.5 1.1)×10-6 • Normalized to B(B0→Kp) • Assigned p mass to both tracks to maximize the separation from B→hh • Large CP assymetry O(10%) expected • Improved previous upper limit Shin-Shan Yu

  40. Control Sample Analysis Requirements pB and mB • pT > 2.0 GeV/c • 120 m ≤ d0≤ 1 mm • |h| < 0.6, fiducial to central muon chamber D0 • 2r < 16 • ct > -70 mm • pT(D*)> 5.0 GeV/c • |M-MPDG | < 3 s Four tracks • 2r < 17 • ct > 200 mm • pT > 6.0 GeV/c pB and mB • pT > 2.0 GeV/c • 120 m ≤ d0≤ 1 mm • |h| < 0.6, fiducial to central muon chamber D+ • 2r < 14 • ct > -30 mm • pT > 5.0 GeV/c Four tracks • 2r < 15 • ct > 200 mm • pT > 6.0 GeV/c Hadronic • | D*-D0 – 0.1455| < 3 s • N = 106  11 Hadronic • | MD-MPDG| < 3 s • N = 579  30 Semileptonic • Muon matching 2r< 9 • 3.0 < Four track mass < 5.3 GeV/c2 • N = 1059  33 Semileptonic • Muon matching 2r< 9 • 3.0 < Four track mass < 5.3 GeV/c2 • N = 4720  100 Shin-Shan Yu

  41. Signal Sample Analysis Requirements pB and mB • pT > 2.0 GeV/c • 120 m ≤ d0≤ 1 mm • |h| < 0.6, fiducial to central muon chamber Lc + • 2r < 14 • ct > -70 mm • pT > 5.0 GeV/c Four tracks • 2r < 15 • ct > 250 mm • pT > 6.0 GeV/c Semileptonic • Muon matching 2r< 9 • 3.7 < Four track mass < 5.64 GeV/c2 • N = 1237  97 Hadronic • | MLc-MPDG| < 3 s • N = 179  19 Shin-Shan Yu

  42. Consistency Check Shin-Shan Yu

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