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Heavy Flavour Meeting 14/04/2005

Heavy Flavour Meeting 14/04/2005. Semileptonic charm decays to electrons in DIS with 1996-2000 e + p data. Mónica Vázquez Sunil Patel. Motivation. Charm production in DIS is a testing ground for QCD m charm >> L QCD : perturbative calculations can be performed

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Heavy Flavour Meeting 14/04/2005

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  1. Heavy Flavour Meeting14/04/2005 Semileptonic charm decays to electrons in DIS with 1996-2000 e+p data Mónica Vázquez Sunil Patel

  2. Motivation • Charm production in DIS is a testing ground for QCD • mcharm >> LQCD : perturbative calculations can be performed • Dominant contribution is BGF, sensitive to the gluon PDF • Charm tagging through detection of charmed mesons BR(c→D*→pKpS) = 2.57 % BR(c→e-) = 9.6  0.4 %

  3. Data and Monte Carlo Samples Data: 96-97 e+p, 38.6 pb-1 99-00 e+p, 65.0 pb-1 Inclusive DIS MC: 96-97 ARIADNE, CTEQ5L, L = 19.6 pb-1 99-00 ARIADNE, CTEQ5L, L = 65.1 pb-1 Semileptonic Charm MC: 96-97 RAPGAP 3.0 CTEQ5L 260.5 pb-1  6  L9697 99-00 RAPGAP 3.0 CTEQ5L 383.3 pb-1  6  L9900

  4. NLO Calculation: HVQDIS • NLO QCD calculation of charm SL DECAY with HVQDIS • PDF: ZEUS01 • Charm mass: 1.35 GeV (consistent with PDF fit) • Varied to 1.20 and 1.50 GeV but not in the PDF for the moment • Renormalisation and Factorisation scales: • Peterson fragmentation:e=0.035 • Hadronisation fraction:0.096 (PDG 2004) • Thanks to Manuel Zambrana for the help! varied a factor 4, 0.25

  5. Trigger Chain • (Dst9&&Dst11) && (Flt44 || Flt46) && TltDIS03 • DST 09 Electron • Elec5, Local, Exotic, Sinistra, or Sinistra95 electron with energy > 4 GeV • No TLT bits Required • DST 11 Nominal neutral current • TLTNC or TLTLQ , E - pz + 2*lumi g > 30 • DIS 03 Medium Q2 • Sinistra or Emille electron with energy > 4 GeV • Radius > 25 cm (9697) or 35 cm (9900) for RCAL electrons • DISEMPZ • FLTBITS && SLTBITS • FLT 44 REMC or BEMC • FLT 46 RCAL Iso E

  6. DIS selection criteria Positron:Box cut: rpositron> 25.5 cm (35.5 cm) Probability > 0.9 Energy > 10 GeV Q2DA> 25 GeV2 0.03<yDA< 0.7 yel < 0.95 yjb>0.02 38 < E-pz < 65 GeV Ntrkvtx> 0 , |Zvtx| < 50cm (regular tracking) True Cuts: Q2 > 25 GeV2 0.03 < y < 0.7 Detector

  7. Control Plots: Scattered Positron quantities 96-97 99-00

  8. Control Plots: Tracking quantities 96-97 99-00

  9. Control Plots: Kinematic variables 96-97 99-00

  10. Electron Identification • Electron tagging using: • ZUFOs • dEdx (Detlef's corrections) • track requirement • 1.2 < p < 5 GeV • (for better separation of hadrons) • 0.65 < Θ < 2.5 rad  7 CTD SL • (for good dEdx recostruction) • CAL deposit requirement • EEMC/ETOT>0.9 ("electron sample") • EEMC/ETOT<0.4 ("hadron sample") → Estimate background CTD dEdx corrections 1 - run-by-run corrections 2 - air pressure correction (if available) 3 - threshold correction 4 - corrections for space charge effect 5 - pt corrections

  11. Signal Extraction • Hadron sample reweighted to electron sample in p,q • Hadron sample scaled to the electron sample in the region • 0.8 < dEdx < 1.1, where the hadron background is dominant • Hadron sample is subtracted from the electron sample

  12. Dominant e- Background:CONVERSIONS Convert2 package is used to tag conversionswith D<15 • 1.2 < pe- < 5 GeV • pe+ > 200 MeV (for good track reconstruction efficiency) • TSAI NLO QED calculation: used to determine invisible conversions kTsai inverse of histogram

  13. Signal Plots 96-97 99-00

  14. 9697 Data - Bins of Q2 96-97

  15. 9900 Data - Bins of Q2 99-00

  16. Other e- background: Dalitz decays and semileptonic beauty decays • Dalitz decays of neutral pions: π0 →γ e+ e- • Branching ratio small(1.1980.032%) but large abundance of π0 in DIS • Tagging method: • Every e- candidate is combined with all positive tracks in the event. • If the minimum invariant mass is < 0.2 GeV the candidate is rejected. • The number of Dalitz decays is the difference between not making and • making this requirement. Semileptonic decays of beauty: previous studies <3% (MC estimate on the way)

  17. Calculating Cross sections 96-97 99-00

  18. 9697 Data - ds/dQ2 Dalitz and slbeauty background not subtracted yet

  19. 9900 Data - ds/dQ2 Dalitz and slbeauty background not subtracted yet

  20. Outlook • Include estimate of Dalitz and beauty electron background • in cross sections. Previous analysis (Dalitz < 4%, Beauty < 3%) • Investigate difference seen between the two analysis • in the number of DIS events ~0.5% • Vary the charm mass consistently in the HVQDIS calculation • Add more differential cross sections ds/dy, ds/dptSLe, ds/dhSLe

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