Heavy Flavour Production in DIS at HERA Benno List - Zeus - Desy

Heavy Flavour Production in DIS at HERABenno ListBenno List, Beauty 2005❑Introduction❑Charm Production❑Beauty Production1Heavy Flavour Production in DIS at HERA

Deep-Inelastic ep Scattering❑ Virtual photon of virtuality Q 2 =-q 2 acts aspointlike probe❑ Bjorken-x is momentum fraction of parton outof the proton❑ „Light“ quark scattering (m q2

Theoretical Challenges❑ Multi-Scale Problem: Hard scales Q 2 , m Q 2 , p T2❑ Treatment of Quarks:❍„Massless“ quarks for m Q2 < Q 2❍Massive quarks for m Q2 > Q 2❍Transition region Q 2 ≈ m Q2 difficult❍Adressed byVariable Flavour Number Scheme VFNS(Lai, Tung; Chuvakin, Smith, Harris; Thorne, Roberts)❑ Monte Carlo❍LO Monte Carlo available (Pythia, Rapgap, Cascade)❍NLO Calculations (HVQDIS), no full MCs with hadronization❍=> use LO MC for detector and hadronization effects,compare x-sections to NLO resultsBenno List, Beauty 20053Heavy Flavour Production in DIS at HERA

Heavy Flavours and the Gluon❑ The gluon in the proton:❍Drives the QCD evolution of the structure functions(at higher Q 2 = higher resolution, more quarks at low x are visible)❍Generates heavy quarks via boson-gluon-fusion❑ Gluon extracted from inclusive structure function measurementsshould lead to a correct prediction of charm production❑ Heavy flavour (especially charm) production measurements canimprove knowledge of gluon density in the proton❑ Note: Charm contributes up to 35% to proton structure at high Q 2Q 2Benno List, Beauty 20054Heavy Flavour Production in DIS at HERA

CharmTechniques:❑ D* tagging❑ Lifetime taggingResults:❑ Inclusive charm cross sections❑ Fragmentation ratiosBenno List, Beauty 20055Heavy Flavour Production in DIS at HERA

Charm Tagging via D* ProductionZEUS, PR D69 (2004) 012004.❑ Large D* Samples from HERA-I❑ Well described by NLO QCD❑ Q 2 evolution measured over 4orders of magnitudeZEUS preliminary 04-024.ZEUS, PR D69 (2004) 012004.Benno List, Beauty 20056Heavy Flavour Production in DIS at HERA

Charm from an Inclusive Lifetime Tag❑ Central Silicon Tracker resolves track impact parameters❑ Measure Significances S i = δ i /σδ i , order them: S 1 > S 2 > S 3❑ Use subtracted spectra to extract uds, c, and bSubtractEventsS0JetS 1Events, subtractedBenno List, Beauty 2005S 1 S 2S 3H1 preliminary 05-0767Heavy Flavour Production in DIS at HERA

Lifetime Tagging: D + SignalHERA-IIH1, EPJ C38 (2005) 447.ZEUS preliminary 04-033Benno List, Beauty 2005M(Kπ π)9Heavy Flavour Production in DIS at HERA

Fragmentation Ratios❑ Measured by H1 and ZEUS❑ Results consistent with e + e - data and of comparable precisionH1 EPJ C38 (2005) 447.ZEUS preliminary DIS2005.Benno List, Beauty 200510Heavy Flavour Production in DIS at HERA

BeautyTechniques❑ Lifetime tagging❑ Semileptonic decays:Jets+Muons❍Relative p t❍Additonal livetime informationResults:❑ Inclusive cross sections (F 2bb)❑ Visible cross sectionsBenno List, Beauty 200511Heavy Flavour Production in DIS at HERA

Inclusive Beauty Cross Section: F 2bb❑ H1: Uses lifetime tagging to extractcharm and beauty together❍First measurement of inclusive bproduction at HERA❍Reasonably well described by NLO QCD❑ ZEUS: New Micro Vertex Detectorallows the same techniqueF 2bbHERA-IIZEUS preliminary 04-029Benno List, Beauty 200512Bjorken xH1, EPJ C40 (2005) 349.H1 preliminary 05-076Heavy Flavour Production in DIS at HERA

Measuring Beauty Production with μ+jetsp Trelthrust axisof μ jetμμδBenno List, Beauty 2005H1, hep-ex/05021013H1, hep-ex/050210Heavy Flavour Production in DIS at HERA

From HERA to LHC❑ HERA provides precise partondensities needed by LHC forbackground and signalcalculation❑ HERA data pushes theory:❍NNLO calculations❍Evolution equations(at s hat >350GeV, top is „light“!)❍Unintegrated gluon densitiesBenno List, Beauty 200516Heavy Flavour Production in DIS at HERA

BackupBackup slidesBenno List, Beauty 200518Heavy Flavour Production in DIS at HERA

Rapity Distributions❑ Both experiments observe excess in forward direction,i.e. in direction of the proton remnantZEUS, PL B599 (2004) 173.Benno List, Beauty 200520H1, hep-ex/050210Heavy Flavour Production in DIS at HERA

The Gluon at HERAD -D 0Today: gluon known to better than10% at Q 2 =20GeV 2 and x=3·10 -4from F 2 measurementsPre-HERA status:gluon guess uncertain by a factor 3 atQ 2 =20GeV 2 and x=3·10 -4 .Benno List, Beauty 200521Heavy Flavour Production in DIS at HERA