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Measurement of charm and bottom production in pp collisions at √ s = 200 GeV at RHIC-PHENIX

Measurement of charm and bottom production in pp collisions at √ s = 200 GeV at RHIC-PHENIX. Yuhei Morino for the PHENIX collaboration CNS, University of Tokyo JSPS. RUN4 RUN7. A.Dion[poster]. min.bias. 1.Introduction. Phys. Rev. Lett. 98, 172301 (2007). Behavior of heavy quarks

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Measurement of charm and bottom production in pp collisions at √ s = 200 GeV at RHIC-PHENIX

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  1. Measurement of charm and bottom production in pp collisions at √s = 200 GeV at RHIC-PHENIX Yuhei Morino for the PHENIX collaboration CNS, University of Tokyo JSPS

  2. RUN4 RUN7 A.Dion[poster] min.bias 1.Introduction Phys. Rev. Lett. 98, 172301 (2007) Behavior of heavy quarks in hot&dense matter • Observation via lepton measurement • Large energy loss • Large V2 • strongly interacting matter for charm! @hot&dense matter • next open question • bottom flow? • bottom energy loss? charm and bottom are not separated. Need to separate charm/bottom to get more information. b contribution?

  3. FONLL: FONLL b/(b+c) FONLL c/(b+c) FONLL c/(b+c) b contribution to non-photonic electron Phys.Rev.Lett 95 122001 • FONLL: Fixed Order plus Next to Leading Log pQCD calculation • Large uncertainty on c/b crossing 3 to 9 GeV/c Measurement of be/ce is key issue. This talk will show the latest result of measurement of c,b in p+p collisions at mid-rapidity Au+Au results were reported at D.Hornback’s talk

  4. Meson D±,D0 Mass 1869(1865) GeV BR D0 --> K+p- 3.85 ± 0.10 % BR D0 --> K+p-p0 14.1 ± 0.10 % BR --> e+ +X 17.2(6.7) % Heavy quark measurement at PHENIX • lepton from semileptonic decay • large branching ratio • c and b mixture K+ p- direct measurement • direct ID (invariant mass) • large combinatorial background

  5. D e K n partial reconstruction Fragmentation 2 Measurement of non-photonic electron Inclusive electron ( g conversion, p Dalitz,etc and heavy quark ) measurement e- • Background subtraction • cocktail method • converter method Semileptonic decay Non-photonic electron (charm and bottom) . S/N>1 @pt>2GeV/c be/(ce+be)? PRL, 97, 252002 (2006)

  6. Main uncertainty of ec and eb  • production ratios (D+/D0, Ds/D0 etc) c,b separation in non-photonic electron D0e+ K-(NO PID) reconstruction Ntag = Nunlike - N like • background subtraction(unlike-like) • photonic component • jet component tagging efficiency when trigger electron is detected, conditional probability of associate hadron detectionin PHENIX acc From data From simulation (PYTHIA and EvtGen) { decay component (~85%)kinematics e jet component (~15%)

  7. c2 /ndf 21.2/22 @b/(b+c)=0.26(obtained value) (0.5~5.0GeV) c2 /ndf 18.7/22 @b/(b+c)=0.56(obtained value) (0.5~5.0GeV) • tag efficiency of • charm increases as • electron pt • tag efficiency of • data gets near bottom ec count tagging efficiency (ec,eb,edata) edata eb c2 /ndf 28.5/22 @b/(b+c)=0.42(obtained value) (0.5~5.0GeV) reconstruction signal and simulation

  8. bottom fraction in non-photonic electron • first result of b fraction measurement at PHENIX • The result is consistent with FONLL

  9. electron spectra from charm and bottom be = (non-photonic) X (be/(ce+be)) PRL, 97, 252002 (2006) charm bottom sdata/sFONLL ~2 reasonable value

  10. cross section of bottom pt extrapolation of be spectra by pQCD First measurement of bottom cross section at mid-rapidity in p+p collisions at PHENIX. rapidity extrapolation by NLO pQCD (|y|<0.35y integrated) sbb(data)/sbb(FONLL)~2

  11. e- K- e+ ne 3 Heavy quark measurement via di-electron e+e- pair A.Toia[talk] arXiv:0802.0050 heavy quark is dominant source @mee >1.1GeV

  12. Di-electron from heavy quark cocktail calculations are subtracted from data • bottom, DY,subtraction •  charm signal !! • mass extrapolation (pQCD) • rapidity extrapolation (pQCD) c dominant b dominant After Drell-Yan subtracted, fit (a*charm+b*bottom) to the data. charm and bottom cross sections from e+e- and c,be agree!

  13. total cross section of bottom total cross section of charm and bottom √s dependence of cross section with NLO pQCD agrees with data

  14. direct measurement: DKp, DKpp • direct ID(peak) • large combinatorial background K+ Meson D±,D0 Mass 1869(1865) GeV BR D0 --> K+p- 3.85 ± 0.10 % p- BR D0 --> K+p-p0 14.1 ± 0.10 % BR --> e+ +X 17.2(6.7) % 4 Direct measurement of D meson

  15. D0K-p+p0 reconstruction S.Butsyk[poster] large branching ratio(14.1%) Clear peak of D0（5<pt<15GeV/c) meson observed in D0K-p+p0 decay channel

  16. tag reconstruct D0K-p+ reconstruction with electron tag electron tag reduce combinatorial background P.Shukla [poster] • observe D0 peak • cross section of D is coming up

  17. 5 Summary and Outlook • be/(ce + be) has been studied in p+p collisions at √s =200GeV via e-h correlation. Cross section of bottom was obtained from electron spectra and be ratio. ・Consistent with FONLL calculation (data/fonll ~ 2) ・This is baseline measurement for understanding heavy quark energy loss and v2 observed in Au+Au collisions and further discussion on heavy quark energy loss will be done. • Cross sections of charm and bottom were obtained from di-electron in p+p collisions at √s =200GeV. • Clear peak of D0 meson observed in p+p collisions at √s =200GeV in D0->K+ p- p0 and D0->K+ p- channels. ・Analysis to determine cross section is on going. • Silicon Vertex Tracker will be installed for more precise study.

  18. back up

  19. Electron Signal and Background [Photonic electron] … Background • Conversion of photons in material Main photon source: p0 → gg In material: g → e+e- (Major contribution of photonic electron) • Dalitz decay of light neutral mesons p0 → g e+e- (Large contribution of photonic) • The other Dalitz decays are small contributions • Direct Photon (is estimated as very small contribution) • Heavy flavor electrons (the most of all non-photonic) • Weak Kaon decays Ke3: K± → p0 e±e (< 3% of non-photonic in pT > 1.0 GeV/c) • Vector Meson Decays w, , fJ → e+e-(< 2-3% of non-photonic in all pT.) [Non-photonic electron] … Signal and minor background

  20. Background Subtraction: Cocktail Method Most sources of background have been measured in PHENIX Decay kinematics and photon conversions can be reconstructed by detector simulation Then, subtract “cocktail” of all background electrons from the inclusive spectrum Advantage is small statistical error.

  21. Ne Electron yield converter 0.8% 0.4% 1.7% With converter Photonic W/O converter Dalitz : 0.8% X0 equivalent radiation length Non-photonic 0 Material amounts: 0 Background Subtraction: Converter Method We know precise radiation length (X0) of each detector material The photonic electron yield can be measured by increase of additional material (photon converter was installed) Advantage is small systematic error in low pT region Background in non-photonic is subtracted by cocktail method Photon Converter (Brass: 1.7% X0)

  22. Consistency Check of Two Methods Accepted by PRL (hep-ex/0609010) Both methods were always checked each other Ex. Run-5 p+p in left Left top figure shows Converter/Cocktail ratio of photonic electrons Left bottom figure shows non-photon/photonic ratio Accepted by PRL (hep-ex/0609010)

  23. γ e- • 2.25pb-1 of triggered p+p data as reference • Material conversion pairs removed by analysis cut • Combinatorial background removed by mixed events • additional correlated background: • cross pairs from decays with four electrons in the final state • particles in same jet (low mass) • or back-to-back jet (high mass) • well understood from MC e+ e+ π0 e+ e- π0 π0 γ e- γ

  24. Method I • Tune cocktail to PHENIX measured hadrons • Subtract cocktail • Extract cross section in multi steps as in ppg065 • A. dsigma_ee/dy(1.1<Mee<2.5; in ideal PHENIX acceptance) This is what directly measured. Only systematic error in the data and Statistical data present. • A1. Extrapolate to 0<M<5 GeV; However, since ds/dy(1.1<M<2.5) is a very tiny fraction of dsigma/dy(0<M), I would rather not mention about it. • B. dsimga_ee/dy(1.1<Mee<2.5; |ye|<0.35)This is when two arm acceptance of PHENIX is corrected. Since the two arm nature is corrected, this is something a theorist can easily calculate.(now acceptance error is involved) • C. dsimga/dy of ccbar (now PYTHIA error is involved: kt, pdf’s and branching ratio because we go from electrons to charm) • D. sigma(ccbar) total (now add error for rapidity distribution) • In the paper we mention only A., C. and D. for simplicity • A. is calculated from the data, C. and D. are derived in the procedure explained in the next slide

  25. Method II • Tune cocktail to PHENIX measured hadrons • Subtract cocktail • Fit p0*charm + p1*bottom + drell yan • Charm cross section = 567 mb (ppg065) • Beauty cross section = 3.77 mb (Claus Jaroceck and commonly used in single electron analysis) • Drell Yan = 0.040 mb and scaled to NLO calculations from Werner Vogelsang • DY (from PYTHIA) + p0*charm +p1*bottom •     p0           9.13960e-01 ± 8.24258e-02 • p1           1.06418e+00 ± 7.13970e-01 • DY (scaling Pythia to Werner’s calculations for M>4GeV) + p0*charm +p1*bottomQ/2 •     p0           9.08741e-01 ± 8.25467e-02 •     p1           1.14892e+00 ± 7.17499e-01 Q •     p0           8.97103e-01 ± 8.25275e-02 •     p1           1.24826e+00 ± 7.17928e-01 Q*2 •     p0           9.09590e-01 ± 8.25467e-02 •     p1           1.13538e+00 ± 7.17499e-01

  26. 50% ce, be spectra # of non-photnic electron in b/(b+c)  PPG65 spectra sys error of # of non-photnic electron 100%correlation sys error of PPG65 enlarge sys error of bottom non-photonic electron (total>b) 90% C.L

  27. phi0 pt Positive charged track negative charged track Phi … detected phi of charged track Phi*… expected phi when charged track has an opposite charge. (swapped phi around phi0) phi phi0 phi* symmetrical Acceptance filter and symmetrical fiducial cut Symmetrical fiducial cut Fiducial cut is also applied for phi*. (symmetrical fiducial cut) This cut will make phase space symmetrical.

  28. X 1/Nnon-phot e From real data edata 0.029 +- 0.003(stat) +- 0.002(sys) count Electron pt 2~5GeV/c Hadron pt 0.4~5.0GeV/c unlike pair like pair bottom production charm production 4. Analysis(RUN5) From simulation (PYTHIA and EvtGen) charm ec = 0.0364 +- 0.0034(sys) bottom eb = 0.0145 +- 0.0014(sys) Electron pt 2~5GeV/c Hadron pt 0.4~5.0GeV/c unlike pair like pair (unlike-like) /# of ele

  29. Electron-hadron invariant mass(RUN5) Mass of hadron is assigned 494MeV, hadron 0.4 < pt <5 GeV/c Electron pt 2~3 GeV/c Electron pt 3~4 GeV/c Unlike pair Like pair Electron pt 4~5 GeV/c Electron pt 2~5 GeV/c

  30. Estimation of systematic error for signal counting Electron pt 2~5 GeV/c real unlike / real like mixing unlike/ mixing like Mixing unlike pair Mixing like pair mixing unlike / mixing like ~=1, there are no effect of phase space RMS is 2%. I will assign this 2% as systematic err about signal counting. mixing unlike/ mixing like

  31. unlike/like ratios Vs invariant mass Real Mixing event Electron pt 2~3 GeV/c Electron pt 3~4 GeV/c Electron pt 4~5 GeV/c Electron pt 2~5 GeV/c

  32. Electron-hadron (unlike – like) invariant mass(RUN5) 0.5 < invariant mass <1.9 GeV pairs are counted as signals. Electron pt 2~3 GeV/c Electron pt 3~4 GeV/c Electron pt 4~5 GeV/c Electron pt 2~5 GeV/c

  33. Electron(2<pt<5) electron (0.4<pt<5 , n0>=2,e/p>0.7) Electron(2<pt<5) hadron (0.4<pt<5,n0<0), mass is assigned 0.511Mev Rejected by pair cut Remaining electron – electron pair rejection(RUN5) Electron veto cut for hadron (n0<0) cannot all electron due to RICH acceptance. pair mass (mass of hadron is assigned 0.511MeV)>0.08GeV cut was used for e-e pairs rejection. But there are remaing electron pairs Mass of associate particle is assigned 494MeV Unlike pair Like pair e –h pair Estimated remaining e-e pair remaing e-e pairs are estimated by invariant mass distribution when mass of associated electron is 0.494Mev. Normalization factor is (# of e-h pair in invariant mass <0.08) / (# of e-e pair in invariant mass <0.08) Unlike pair Like pair Estimated e-e pairs are subtracted. Systematic error of this subtraction is estimated by statistics of (# of e-h pair in invariant mass <0.08) / (# of e-e pair in invariant mass <0.08)

  34. spectra of FONLL&PTYHIA(1.5<kt<10GeV/c) 4.21 +- 0.4 PYTHIA & EvtGen combination::0.88 PDG value & changing B hadron ratio::10+-1% PYTHIA & HVQMNR(NLO QCD) 3.44+-0.25

  35. Electron-hadron (unlike – like) invariant mass(RUN5) after remaining e-e pair rejection Electron pt 2~3 GeV/c Electron pt 3~4 GeV/c Electron pt 4~5 GeV/c Electron pt 2~5 GeV/c

  36. High Pt extension eID … tight cut hadron background was estimated from e/p distribution the effect of h-h correlation hadron iD … standard eID cut +prob<0.01 +0.6<e/p<0.8 99% hadron ehadron :: 0.087+- 0.043 (50% systematic error)

  37. PYTHIA  EvtGen  PISA Produce D (B) products Decay D (B) products Simulate detector response B0 b B0 b Bs+ Bs+ bbar bbar EvtGen

  38. EvtGen products D* PYTHIA products EvtGen and PYTHIA products charm(bottom) gluon string string D* pi0 D0 ……… gamma e+ K- nu gamma EvtGen only EvtGen+PYTHIA Fast monte carlo calculation for EvtGen ony and EvtGen+PYTHIA electron pt 2~5GeV/c EvtGen+PYTHIA … ec 0.0342 EvtGen only …ec0.0301 ~15% of ec are from PYTHIA. This part may be changed by PYTHIA fragmentation,etc I assign PYTHIA 20% systematic error. This error corresponds 3% error for ec

  39. photonic electron unlike/like

  40. count e/p 7~8 GeV/c 5~6 GeV/c 6~7 GeV/c 8~9 GeV/c 9~10 GeV/c Hadron contamination (pt>5 GeV/c) electron peak is clearly seen at pt<9GeV/c tight eid cut (normal && n1>4 &&prob>0.1) estimated hadron (at previous page) 3% 5% 11% fit estimated hadron distribution (back ground) Fix Fit e/p distribution at tight eid cut 12% 17% hadron contamination (e/p>0.9) was estimated these fit functions.

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