XXXIV International Symposium on Multiparticle Dynamics Alberto Cruz On behalf of the CDF collaboration

Main Injector Tevatron DØCDF Chicago   p source Booster Fermilab Florida

Tevatron proton-antiproton collisions Main injector (150 GeV proton storage ring) antiproton recycler (commissioning) Electron cooling this year Operational on June’05 40% increase in Luminosity 36 bunches (396 ns crossing time) Long Term Luminosity Projection (by end FY2009) Base Goal -> 4.4 fb-1 Design -> 8.5 fb-1 Increasing Luminosity: RUN I ( ) ~0.1fb -1 RUN IIa (2001~2005) ~1fb -1

Tevatron Performance Recent Luminosity Record of 10.3x10 31 sec -1 cm -2 (July 16, 2004)

CDF Run II Data CDF Efficiency > 80% DAQ runs with 5% to 10% dead time Rest coming from very careful operation of detector’s HV due to machine losses (…to preserve silicon & trackers…) CDF -> ~450 pb -1 on tape

In proton-antiproton collisions we can occasionally have a “hard” parton-parton scattering resulting in large transverse momentum outgoing partons. The Jet Algorithm Allows us to “see” the partons (or at least their fingerprints) in the final hadronic state.

Jet algorithms & physics Final state partons are revealed through collimated flows of hadrons called jets Measurements are performed at hadron level & theory is parton level (hadron  parton transition will depend on parton shower modeling) Precise jet search algorithms necessary to compare with theory and to define hard physics Natural choice is to use a cone-based algorithm in  -  space (invariant under longitudinal boost)

Run II -> MidPoint algorithm 1.Define a list of seeds using CAL towers with E > 1 GeV 2.Draw a cone of radius R around each seed and form “proto-jet” 3.Draw new cones around “proto-jets” and iterate until stable cones 4.Put seed in Midpoint (  -  ) for each pair of proto-jets separated by less than 2R and iterate for stable jets 5.Merging/Splitting Cross section calculable in pQCD T Arbitrary Rsep parameter still present in pQCD calculation …

Comparison of JetClu and MidPoint for HERWIG MC Differences between MidPoint and JetClu found to be due to “ratcheting”. JetClu  0.5-2% higher E T jets Comparison of the JetClu to MidPoint cone algorithms

W/Z/  +jets) production: introduction QCD-wise, are W/Z/  cross sections of interest? èSmaller subset of diagrams, different mix of initial partons  Below is a set of LO diagrams for W/Z and W/Z/  + 1 jet èInclusive distributions are not affected by jet finding uncertainties lMore theoretical work is needed, e.g.: èW inclusive: known at the level of NNLO èW + 1 jet: known at the level of NLO èW + 2, 3, 4 jets:known at the level of LO  (MCFM does proved W + 2 jets at NLO, it just isn’t an event generator)

W+jet(s) Production (JetClu R=0.4) Background to top and Higgs Physics Stringent test of pQCD predictions Test Ground for ME+PS techniques (Special matching  MLM, CKKW to avoid double counting on ME+PS interface) Alpgen + Herwig LO  large uncertainty W + 1 parton +PS W+ 2 partons 40% higher than the RUNI result QCD corrections cover this difference. Inclusive  (nb) Run I (1.8 TeV): LO: 1.76 NLO:2.41 NNLO:2.50 CDF I:2.38  0.24 Run II (1.96 TeV): LO: 1.94 NLO:2.64 NNLO:2.73 CDF II: 2.64  0.18

W+ jet(s) Production (JetClu R=0.4) 1 st jet in W + 1p 2 nd jet in W + 2p 3 rd 4 th ME+PS implementation tested using the N th jet spectrum in W+N jet events. Dijet Mass in W+2jets Energy-scale

Diphoton Production Testing NLO pQCD and resummation methods Signature of interesting physics –One of main Higgs discovery channels at LHC Data: 2 isolated γs in central region, E T 1,2 > 14, 13 GeV General agreement with NLO predictions

γ +heavy flavour production Probes heavy-quark PDFs b/c-quark tag based on displaced vertices Secondary vertex mass discriminates flavour MC templates for b/c & (uds) used to extract b/c fraction in data

γ +heavy flavour production Good agreement with LO pQCD within still very large stat. errors Validates quark flavour separation using secondary vertex mass γ +b-quark γ +c-quark

Summary Tevatron and CDF are performing well èData samples already significantly exceed those of Run I èOn track for accumulating 4-8 fb -1 by 2009 lRobust QCD program is underway èJets, photons, W+jets, heavy flavors  Jet energy scale is the dominant systematics – improvements on the way  Heavy flavor identification is working well èVerifying and tuning tools: NLO calculations, Monte Carlo generators, resummation techniques, combining ME with PS  NLO does well for hard aspects  LO + Pythia give reasonable description of W+n jets lWe don’t see any discrepancies.