7/9/2005U. Heintz - PiC heavy flavor production Ulrich Heintz Boston University

7/9/2005U. Heintz - PiC disclaimers/acknowledgements not a comprehensive review but selected results with concentration on b-production at the Tevatron not covered at all –c-production –results from e + e - collisions material from talks at Moriond, La Thuile, Beauty 2005 thanks to D.Bauer, I.Belyaev, I.Bloch, M.D’Onofrio, M.Hildreth, V.Papadimitriou

7/9/2005U. Heintz - PiC why? check our understanding of QCD –heavy flavor production at high energies checks perturbative QCD –extracting fundamental parameters of the standard model at hadron colliders requires deep understanding of QCD

7/9/2005U. Heintz - PiC b production at high energies HERA (H1/ZEUS) 30/920 GeV –photoproduction Q 2 <1 GeV 2 hard scales: m b, p T –deep inelastic scattering Q 2 >1 GeV 2 hard scales: m b, p T, Q 2 Tevatron (D0/CDF) √s=1.96 TeV –hard scales: m b, p T at least one hard scale  pQCD should work concentrate on Tevatron

7/9/2005U. Heintz - PiC b production at high energies DO Run I (PRL 84 (2000) 5478) CDF Run I (PRL 85 (2002) 5068)

7/9/2005U. Heintz - PiC DØDØ excellent muon acceptance |η|<2 excellent tracking coverage |η|<3 (impact parameter

7/9/2005U. Heintz - PiC CDF excellent mass resolution particle id: tof and dE/dx impact parameter

7/9/2005U. Heintz - PiC Tevatron performance since June fold increase in –peak luminosity –integrated luminosity per week –total integrated luminosity instantaneous luminosities above cm -2 s -1 total integrated luminosity just reached 1 fb -1 analyses shown use pb -1

7/9/2005U. Heintz - PiC b production at Tevatron b production cross section at √s=1.96 TeV  50  b –rate  few kHz at current luminosities many developments in theory in recent years –full calculations to NLO –resummation of log(pT/mb) terms (fixed order NLO +NLL  FONLL) –substantial changes in fragmentation functions –new pdf’s leading order next to leading order

7/9/2005U. Heintz - PiC b cross section measurements J/  and b-hadron production cross sections (CDF) Inclusive b-jet cross section (CDF) High p T cross section for  -tagged jets (DØ)

7/9/2005U. Heintz - PiC b cross section using J/  (CDF) use exclusive decays of b-hadrons to measure the b-production cross section –inclusive J/  cross section –fraction of J/  from decay of b-hadrons –b-hadron cross section for all p T

7/9/2005U. Heintz - PiC b cross section using J/  (CDF) J/  ’s can originate from –direct production –decay of excited cc-states –decay of b-hadrons dimuon trigger –¼ 300k J/  events –mass resolution MeV

7/9/2005U. Heintz - PiC b cross section using J/  (CDF) inclusive J/  cross section

7/9/2005U. Heintz - PiC b cross section using J/  (CDF) long life time of b-hadrons –c  ¼ 450  m J/  decay vertex displaced plot pseudo proper decay time x=L xy m/p T in bins of p T of J/  max likelihood fit for b-fraction f b = 9.4% f b = 33.7%

7/9/2005U. Heintz - PiC b cross section using J/  (CDF) systematic error on b-fraction ¼ 3-13%

7/9/2005U. Heintz - PiC b cross section using J/  (CDF) total inclusive b-hadron cross section comparison with Run I B + cross section Run II scaled for B + fragmentation, |y|<1  Ldt¼ 40 pb -1 PRD 71, (2005)

7/9/2005U. Heintz - PiC high-p T b-jet cross section (CDF) reconstruct b-decay vertex using displaced tracks in jet R jet =0.7, |y jet |<0.7

7/9/2005U. Heintz - PiC high-p T b-jet cross section (CDF) determine b-fraction of tagged jets in bins of jet p T using mass of particles that point to secondary vertex

7/9/2005U. Heintz - PiC high-p T b-jet cross section (CDF) b-jet cross section for 38<p T <400 GeV  L dt = 300 pb -1 source of syst errorlow p T high p T luminosity6% jet energy scale15%40% jet energy scale6% b-tagging efficiency10%15% b-fraction10%40% unfolding8%

7/9/2005U. Heintz - PiC high p T  -tagged jet cross section (DØ) first step to b-production cross section jet with  in cone  Ldt = 300 pb -1 R jet =0.5, |y jet |<  -tagged jets PYTHIA:  55% of all  -tagged jets from heavy flavor (b,c)

7/9/2005U. Heintz - PiC high p T  -tagged jet cross section (DØ) unsmear detector resolution NLO: Z. Nagy, Phys. Rev. D 68,

7/9/2005U. Heintz - PiC what changed? long-standing “discrepancies” between predicted and measured cross sections seem resolved better theory: –sum terms with log(p T /m b ) (FONLL) e.g. Cacciari, Frixione,Mangano, Nason, Ridolfi, JHEP 0407 (2004) 033 –better understanding of fragmentation functions –better estimate of theory errors (upward!) better parton distributions: –add more gluons better experimental observables: –not b-quarks but b-hadrons

7/9/2005U. Heintz - PiC quarkonia production slightly different theoretical context –non-relativistic QCD (NRQCD) Lepage et al., PRD (1992) –production described by short distance cross sections and nonperturbative matrix elements for evolution to quarkonium state. –color octet modes required on top of color singlet to describe production (demonstrated by CDF in Run I) results: –DØ: Υ(1s) production, Υ  µµ final state –CDF: prompt J/  polarization

7/9/2005U. Heintz - PiC Y(1S) production (DØ) test boundary between perturbative and non-perturbative QCD –perturbative color singlet production suppressed by  s –color evaporation (soft gluons carry away color/spin  non-perturbative) –perturbative color octet production can reproduce high p T region V.A. Khoze, A.D. Martin, M.G. Ryskin, W.J. Stirling, hep-ph/ –resum logs to address low p T region E.L. Berger, J.Qiu, Y.Wang, Phys Rev D (2005) color singlet process color octet process

7/9/2005U. Heintz - PiC Y(1S) production (DØ) unlike charmonium, all bb-states are produced directly 50% of Y(1S) from decay of other bb- states

7/9/2005U. Heintz - PiC Y(1S) production (DØ) fix mass splittings and relative widths in fit 5 free parameters: –m(1S),  (1S), n(1S), n(2S), n(3S) |y(Y)|<0.60.6<|y(Y)|< <|y(Y)|<1.8 all three: 4 GeV < p T (Y) < 6 GeV

7/9/2005U. Heintz - PiC Y(1S) production (DØ) little variation in the shape of the cross section as a function of rapidity reasonable agreement with calculations by Berger et al, hep-ph/  Ldt = 159 pb-1 hep-ex/ , PRL (2005)

7/9/2005U. Heintz - PiC prompt J/  polarization (CDF) large prompt J/  cross section (Run I) –color octet mechanism Braaten/Fleming PRL (1995) –transversely polarized J/  at large p T transverse alignment (symmetric decays) longitudinal alignment (asymmetric decays)

7/9/2005U. Heintz - PiC HERA contributing processes:  g fusion resolved  –contributes to photoproduction –suppressed at high Q H1 –e § p (72 pb -1 ) ZEUS –e + p (50 pb -1 ) 920 GeV 28 GeV

7/9/2005U. Heintz - PiC HERA  + dijet photoproduction –Q 2 <1 GeV 2 H1: –b-identification large mass –p T of  relative to jet long life time –impact parameter of  –  vis (ep  ebbX  ejj  X)=38.4§3.4(stat)§5.4(syst) pb –prediction: GeV

7/9/2005U. Heintz - PiC HERA  + jet deep inelastic scattering –2 GeV 2 < Q 2 < 100 GeV   vis (ep  ebbX  ej  X)=16.3§2.0(stat)§2.3(syst) pb prediction: GeV

7/9/2005U. Heintz - PiC HERA see discrepancy at low p  and high 

7/9/2005U. Heintz - PiC HERA discrepancy at high  also seen in ZEUS data ZEUS –  vis (ep  ebbX  ej  X)=40.9§5.7(stat) (syst) pb –prediction: GeV hep-ex/ hep-ex/

7/9/2005U. Heintz - PiC conclusions b production at the Tevatron –finally NLO QCD and data agree better theory calculation: –FONLL + fragmentation functions + pdf’s well-defined observables quarkonium production –Y(1S) production agrees with pQCD + resummation predictions –J/  is not transversely polarized as expected by color octet production b production at HERA –pQCD predictions are ¼ 2  low –discrepancies at low p T and high 

7/9/2005U. Heintz - PiC