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Studies of open heavy flavour production at LHCb Artur Ukleja

Studies of open heavy flavour production at LHCb Artur Ukleja (The Andrzej Sołtan Institute for Nuclear Studies, Warsaw) on behalf of the LHCb Collaboration XIV International Conference on Hadron Spectroscopy München , 13-17 June 2011. Outlook. Motivation

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Studies of open heavy flavour production at LHCb Artur Ukleja

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  1. Studies of open heavy flavour production at LHCb Artur Ukleja (The AndrzejSołtan Institute for Nuclear Studies, Warsaw) on behalf of the LHCb Collaboration XIV International Conference on Hadron Spectroscopy München, 13-17 June 2011

  2. A.Ukleja Studies of open heavy flavour production at LHCb Outlook • Motivation • Inclusive cross-section to produce b-flavoured hadrons • (two measurements): • semileptonic: • inclusive J/y (mm): • also measured open charm cross-section • ≈ 20 times higher than b cross-section • Fragmentation fractions: • fs/ (fu+fd) • using semileptonic modes: • fLb/ (fu+fd) • using semileptonic modes: • fs/fd • using hadronic modes: • Summary

  3. A.Ukleja Studies of open heavy flavour production at LHCb Motivation • Knowledge of b-yield is critical in ascertaining sensitivity of experiments • in B flavour sector (searching of new sources of CPV) • b-flavour hadrons cross-section can be compared to QCD predictions • also needed to estimate sensitivity to NP in B decays • Fragmentation fractions fs/fd • input to inclusive b cross-section measurement • fsneeded for all B0s branching ratios measurement In particular for precise measurements • Fragmentation fraction fLb: • CDF’s value is substantially larger then LEP’s • explained by CDF: it’s because of difference of <pT(B)>

  4. - A.Ukleja Studies of open heavy flavour production at LHCb b or anti-b hadrons cross-section: using b→D0Xm- n D0→K- p+ Prompt D: IP ≈ 0 • D from b: large IP (the smallest distance between D reconstr. trajectory and PV) • Prompt D and Dfb components can be separated using IP with respect to the closest PV PV D from b: IP > 0 PV IP of D0 NOm requirement 3 nb-1 Prompt D (Back- ground) Prompt D D from b (Signal) 3 nb-1 Background >> Signal

  5. - A.Ukleja Studies of open heavy flavour production at LHCb b or anti-b hadrons cross-section: using b→D0Xm-n D0→K-p+ • To select decay chain we match D0 candidates with tracks identified as muons: • RS combinations: m sign of charge the same as K in D decay • WS combinations: opposite signs of charges of K and m IP of D0 ; Now m required RS WS D from b (Signal) 12 nb-1 12 nb-1 Prompt D (Background) Prompt D (Background) sidebands Now: Background (solid) << Signal (dashed) As expected: prompt yields are consistent between RS and WS

  6. - A.Ukleja Studies of open heavy flavour production at LHCb b or anti-b hadrons cross-section: using b→D0Xm-n D0→K- p+ Dominant systematics: [Phys.Lett.B694,209 (2010)] (MCFM) • Summing over h (2<h<6) • [using LEP frag. fractions]: • s(pp→HbX) = (75.3 ± 5.4 ± 13.0) mb • (stat) (syst) • consistent with predictions The measured value changes if the b-hadron fractions differ If Tevatron frag. fractions are used: s(pp→HbX) = (89.6 ± 6.4 ± 15.5) mb Total b anti-b cross-sections (extrapolate using Pythia): s(pp→HbX) = (284 ± 20 ± 49) mb Using Tevatron frag. fractions result increases by 19%

  7. A.Ukleja Studies of open heavy flavour production at LHCb b or anti-b hadrons cross-section: using b→J/yX J/y→m- m+ Prompt J/y: tz≈ 0 J/y from b: tz> 0 Pseudo lifetime used to separate prompt and J/y from b: PV b PV J/y from b:

  8. A.Ukleja Studies of open heavy flavour production at LHCb b or anti-b hadrons cross-section: using b→J/yX J/y→m- m+ [Submitted to Eur.Phys.J C: hep-ex/1103.0423] • Measured cross-sections depend on y and pT • Total – extrapolate using Pythia (using LEP frag. frac.): • s(pp→HbX) = (288 ± 4stat ± 48syst) mb • (2% change when using Tevatron fractions • is included in systematic error) • Good agreement among both measurements • from : s(pp→HbX) = (284 ± 20 ± 49) mb • Good agreement with QCD predictions Dominant systematics:

  9. A.Ukleja Studies of open heavy flavour production at LHCb Fragmentation fractions Probability of b quarkhadronizing with an antiquark (anti-d,u,s) or a di-quark pair (ud) • Input to inclusive b cross-section measurement • fsneeded forall B0sbranching ratios measurement • in particular for precise measurements Two methods: semileptonic modes: hadronic modes:

  10. A.Ukleja Studies of open heavy flavour production at LHCb Ratio of fragmentation fractions fs/ (fu+fd) semileptonic modes ncorr – efficiency, branching fractions and cross-feed corrected yields Cross-feed between channels is taken into account (C.Weiser, DELPHI 99-162 TALK 6, 1999)

  11. A.Ukleja Studies of open heavy flavour production at LHCb Semileptonic modes

  12. A.Ukleja Studies of open heavy flavour production at LHCb Ratio of fragmentation fractions fs/(fu+fd) semileptonic modes LHCb: 3 pb-1 Dominant systematics: fs/ (fu+fd) h [2,3] LEP: 0.128 ± 0.012 CDF: 0.135 ± 0.016 • No evidence for dependence on h or pT(charm+m) • Good agreement with LEP and Tevatron values h [3,5] pT(charm+m) [GeV]

  13. A.Ukleja Studies of open heavy flavour production at LHCb Ratio of fragmentation fractions fLb/ (fu+fd) semileptonic modes LHCb: 3 pb-1 • Slope with pT not consistent with zero • Parameterising with straight line gives (for pT< 14 GeV): fLb/ (fu+fd) Systematic error dominates 26% uncertainty on BR(Lc→pKp) h [2,3] h [3,5] pT(charm+m) [GeV]

  14. A.Ukleja Studies of open heavy flavour production at LHCb Ratio of fragmentation fractions fs/fd hadronic modes • The ratio: B0s→D-sp+/ B0d→D-K+ • only tree diagrams are involved • theoretically well understood, branching ratios calculable • suffers from reconstructed yield • of B0d→D-K+ K+ p+ D- D-s B0s B0d World average for B0s-to-B0d lifetime ratio: εX – total detector efficiency NX – observed number of decays Na=1.00±0.02 – non factorizable U-spin breaking effects NF=1.24±0.08 – ratio of form factors (R.Fleisher, N.Serra, N.Tuning, Phys.Rev.D83:014017,2011)

  15. A.Ukleja Studies of open heavy flavour production at LHCb Ratio of fragmentation fractions fs/fd hadronic modes • The ratio: B0s→D-sp+/ B0d→D-p+ • suffers from theoretical uncertainties due to contribution from W exchange diagram p+ p+ D- D-s B0s B0d W εX– total detector efficiency NX – observed number of decays Na=1.00±0.02 – non factorizable U-spin breaking effects NF=1.24±0.08 – ratio of form factors NE=0.966±0.075 – additional correctionterm for the W exchange in B0d→D-p+ decay

  16. A.Ukleja Studies of open heavy flavour production at LHCb Ratio of fragmentation fractions fs/fd hadronic modes Modes topologically identical and using identical selection criteria to minimizing efficiency differences between modes LHCb 35 pb-1 • From B0s→D-sp+ and B0d→D-K+:fs/fd= 0.242 ± 0.024stat ± 0.018syst ± 0.016theor • From B0s→D-sp+ and B0d→D-p+ : fs/fd= 0.249 ± 0.013stat ± 0.020syst ± 0.025theor • Combined:fs/fd= 0.245 ± 0.017stat ± 0.018syst ± 0.018theor • Theoretical uncertainty dominated by uncertainty on form factor ratio • Agrees well with semileptonic result and LEP and Tevatron • Extra result: extract world best BR(B0d→D-K+)=(2.02 ± 0.17 ± 0.12) × 10-4 (LHCb-CONF-2011-013)

  17. A.Ukleja Studies of open heavy flavour production at LHCb Summary • LHCb has measured the b or anti-b hadrons cross-section in √s=7 TeVpp collisions (total): • in agreement with (and more precise than) QCD predictions • measured open charm cross-section (≈20 times higher) • LHCb has measured the ratios of fragmentation fractions • fs/fdin good agreement with LEP and Tevatron • fLb/ (fu+fd) partially for different pT (pT<14GeV) than Tevatron (〈pT〉≈14GeV), in common region of pT good agreement

  18. A.Ukleja Studies of open heavy flavour production at LHCb Backup

  19. A.Ukleja Studies of open heavy flavour production at LHCb D0 cross section – example LHCb: 2 nb-1 Also measured for: D+ , D*+ , D+s The shape and absolute normalization are in good agreement with theoretical predictions 20 times higher than s(b anti-b) (LHCb-CONF-2010-013) Combining all (pT<8 GeV , 2<y<4.5): Full pTand y using Pythia extrapolation:

  20. A.Ukleja Studies of open heavy flavour production at LHCb (C.Weiser, DELPHI 99-162 TALK 6, 1999)

  21. A.Ukleja Studies of open heavy flavour production at LHCb

  22. A.Ukleja Studies of open heavy flavour production at LHCb

  23. A.Ukleja Studies of open heavy flavour production at LHCb

  24. A.Ukleja Studies of open heavy flavour production at LHCb

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