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New results on inclusive heavy quark production in gamma gamma collisions are presented. Charm and bottom production are investigated at LEP II energies by the experiments ALEPH, DELPHI, L3, and OPAL. The total and differential cross sections for charm qua
SI-2000-8August2000
HEAVYQUARKPRODUCTIONINγγCOLLISIONSA.BOHRER
¨FachbereichPhysik,Universit¨atSiegen,D-57068Siegen,Germany
E-mail:[email protected]
002Newresultsoninclusiveheavyquarkproductioninγγcollisionsarepresented.Charmandbottom productionareinvestigatedatLEPIIenergiesbytheexperimentsALEPH,DELPHI,L3,andOPAL.Thetotalanddi erentialcrosssectionsforcharmquarksaremeasured.Thecontributionsfromtheepdirectandsingle-resolvedprocessesareseparatedandtheirfractionsquanti ed.Moredetailedstudies,Ssuchasthedependenceofthecrosssectiononthetwo-photoncentre-of-massenergyandthecharm
structurefunctionF1γ,2c
,arereported.Theinclusivebottomcrosssectionispresented.Measurementsarecomparedtonext-to-leadingordercalculations.
1 ]
11Introduction
VevG 1Theproductionofheavy avourintwo-/ b2pphotoncollisionsisdominatedbytwopro- [
1*Dp
9cesses,thedirectandthesingle-resolvedpro-d/0cess.Bothcontributeinequalsharestoσd00heavy avour nalstatesatLEPIIener-/gies.Thelargequarkmassallowsreliablehpperturbativecalculationsforthedirectcon--tribution.Thesingle-resolvedoneinadditionpedependsonthegluondensityofthephoton.
Inthisarticlethenewmeasurements:hvfromtheLEPexperimentsonheavy avouriXproductionandthecomparisonwithnext-to-leadingordercalculations2aresummarized.rT
aOnlythemainresultsaregiven.Fordetailsthereaderisreferredtotheoriginalpapers.Figure1.Di erentialcrosssectiondσ/dpD TversusthetransversemomentumpD ToftheD +.
2
HeavyQuarkIdenti cation
3
Di erentialCharmCrossSection
Aclear,non-ambiguoussignalforcharm
quarkproductionisthepresenceofaD +.ThegooddetectorresolutionandwiththeThisgold-platedsignaturehasbeenexploitedlowkineticenergyavailable,theD +methodbyallfourLEPcollaborations.Boththeallowsforameasurementofthedi erentialproductionprobabilityP(c→D +)andthecrosssectionintransversemomentum(seebranchingratiotoD0π+aswellastheD0Figure1)andpseudorapidity.Thethreeex-branchingratiosarereasonablywell-known.
periments,ALEPH,L3,OPAL,agreeamongTheleptonicdecayhasbeenusedbythemselvesandwiththetheoreticalexpec-ALEPH(µ±forcharm)andL3(µ±ande±tation,thatthedistributioninpseudorapid-bothforcharmandbottom).Thoughtheseityisaboutconstant.Intransversemomen-analysesrelyonthemomentumspectrumastumthemasslessapproachfollowstheOPALtheoreticalinput,thestatisticsissubstan-measurements,whilethemassivecalculationtiallyincreased.
isclosertotheALEPHdata.
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