Presentation Description

No description available.


Presentation Transcript

New (QCD) Results from the Tevatron: 

New (QCD) Results from the Tevatron Sarah Eno U. Maryland For the D0 and CDF collaborations 14 Apr 2004


Tevatron Run 0 ’88/’89 20 pb-1 Run I ’92/’96 120 pb-1 Upgraded 2000 1.8 TeV1.96 TeV Goal: 20 pb-1/week 10E31 cm-2 s-1 2 fb-1 (from summary taped onto my office wall in ’92)


Tevatron DØ Data: 1.0 years Commission: 1.5 years Nov 2002 D0 March 2002 CDF Run I record



CDF and D0: 

CDF and D0 Cal: Ur-liquid Ar Cal: Pb-scintillator DØ CDF

QCD: Run0/Run I: 

QCD: Run0/Run I Rapidity Gaps/Diffractive Physics/Elastic Physics (10 papers) PDF’s: double parton interactions (1 paper), W charge asymmetry (3 papers) Non-Perturbative QCD: jet shapes (4 papers), W/Z boson PT spectra (8 papers), other (9 papers) Perturbative QCD, particle cross sctions: W/Z bosons (9 papers), prompt photons ( 8 papers), jets (14 papers), top (6 papers), b/c quarks (lots of papers) Perturbative QCD with W/Z bosons ( 6 papers) Perturbative QCD with jets: as (1 paper), jet topologies (12 papers) 84 papers! (+ lots of b/c papers) New results in all these areas for this winter’s conferences. It’s not all top and electroweak physics!

Run II, 2003 Winter Conferences: 

Run II, 2003 Winter Conferences CDF inclusive jet cross section, central region dijet mass spectra jet shapes and energy flow in dijet events diffractive jets photon plus heavy quark DØ inclusive jet cross section, central region dijet mass uncorrected dijet DF elastic scattering data

New Results for 2004: 

New Results for 2004 CDF jet multiplicities in W+jet events (127 pb-1) Underlying event in jet events/minbias data Di-photon Cross section (207 pb-1) W/Z cross sections (72 pb-1) top cross sections (126-200 pb-1) DØ inclusive jet cross section, forward region (143 pb-1) dijet cross section (143 pb-1) azimuthal decorrelation in dijet events (150 pb-1) elastic scattering Z’s with rapidity gaps (117 pb-1) top cross sections (140-156 pb-1) Channel-by-channel luminosity variations due to detector-specific good run selection Harder analyses tend to freeze their data sample earlier, and thus have less luminosity

Jet Cross Section, Run I: 

Jet Cross Section, Run I High ET jets probe large x PDF’s, especially gluon PDF. Run II has extended reach in jet ET

New Algorithm: 

New Algorithm Use Run II cone algorithm Combine particles in a R=0.7 cone Use the four vector of every tower as a seed Rerun using the midpoints between pairs of jets as seeds Overlapping jets merged if the overlap area contains more than 50% of lower Pt jet, otherwise particles assigned to nearest jet. Both groups now using same algorithm Reduced sensitivity to soft radiation E-scheme recombination

CDF Update: 

CDF Update 177 pb-1 More luminosity since winter 2003

DØ Results: 

DØ Results First corrected run II jet cross section for forward jets Important PDF information is in the cross section versus rapidity

Uncertainties, Central Jets: 

Uncertainties, Central Jets Uncertainties dominated by jet energy scale. Jet energy scale is systematics dominated in central.

Uncertainties, Forward Jets: 

Uncertainties, Forward Jets Energy scale error large. Systematics dominated. Expect improvement soon.

DØ DiJet Cross Section: 

DØ DiJet Cross Section Often used to search for new resonances Uncertainty dominated by jet energy scale

CDF, Dijet Mass: 

CDF, Dijet Mass CDF’s highest mass dijet event M=1364 GeV, ET’s=633,666

DØ, F Decorrelation: 

DØ, F Decorrelation Leading Order pQCD Jets are back-to-back 3 jets in pQCD Df12 = p Df12 < p Df12 is sensitive to jet formation without having to measure 3rd jet directly!

Azimuthal Decorrelation: 

Azimuthal Decorrelation For small Dh, data agrees well with herwig and reasonably well with LO perturbative calculation (JETRAD) jetrad herwig bkfl

Azimuthal Decorrelation: 

Azimuthal Decorrelation Run II. Differential measurement at small Dh. LO (in 3rd jet) perturbative calculation (JETRAD) does not agree. Not too surprising… Calculation diverges at p no phase space beyond 2p/3 lots of 4 jet events at smaller DF. NLO not so bad!

Azimuthal Decorrelation: 

Azimuthal Decorrelation okay agreement with herwig, pythia. Tuned pythia gives best agreement. NLO is better in intermediate region. Pythia distribution sensitive to “maximum virtuality for the initial-state parton shower in terms of the hard matrix scale” (PARP(67)). Tune “A” is the CDF UE tune discussed later.

CDF, Di-Photon: 

CDF, Di-Photon Two isolated and energetic high Et photons in the central region CDF Run I: cross section 3x prediction from NLO QCD (Bailey, Owens, Ohnemus, Phys. Rev. D 46, 2018 (1992) Correlations between the 2 photons can be used to test NLO QCD and study the transverse momentum of the initial partons (KT)


Di-Photon Plotted versus mass of 2 photons instead of photon PT DIPHOX hep-ph/9911340 Eur.Phys.J C16, 311 Additional “fragmentation” diagrams ResBos hep-ph/9712471

CDF W+Jets: 

CDF W+Jets Systematic uncertainty (10% in s1 to 40% in s4) limits the measurement sensitivity Results agree with LO QCD predictions within the errors! Crucial to be able to calculate/understand this for top/higgs physics ALPGEN LO matrix element interfaced with HERWIG for parton shower Not more than one parton associated with a reconstructed jet

CDF W+jets: 

CDF W+jets

CDF, Underlying Event: 

CDF, Underlying Event The “underlying event” consists of hard initial & final-state radiation plus the “beam-beam remnants” and possible multiple parton interactions. Studies of min bias events, Jet events in Run I produced “PYTHIA Tune A” Run II: Look at distributions/correlations of charged particles with h<1, pT>500 MeV Studies of mini-jets in min bias events Lots has work has been done, far too much to summarize here

CDF, Underlying Event: 

CDF, Underlying Event “Back-to-Back” (Df12>150o,ETj2/ETj1>0.8) Transverse regions are sensitive to underlying event The “underlying event” consists of hard initial & final-state radiation plus the “beam-beam remnants” and possible multiple parton interactions.

Underlying Event: 

Underlying Event Min Bias With and without requiring the 2nd jet back-to-back with leading jet

Underlying Event: 

Underlying Event Pythia tuned using Run I data can describe data better than (untuned) Herwig Compared to pythia Tune A Compared to untuned herwig

Min Bias Data: 

Min Bias Data Look for min bias events with a track over a threshold. Look at distribution of charged PT in F relative to that track. Compare to Tune A

3rd Jet: 

3rd Jet Better job at predicting the emergence of the little jets in back-to-back dijet events than in Min Bias. Herwig also good Tune A Herwig

DØ, Elastic Scattering: 

DØ, Elastic Scattering Pomeron, Odderon Exchange: intact proton,antiproton t ~ θ2, where θ is scattering angle

Elastic Scattering: 

Elastic Scattering ISR and E710 data

Elastic Results: 

Elastic Results normalization is arbitrary!

Diffractive Z’s: 

Diffractive Z’s Collision between a “pomeron” and a proton or antiproton: intact p or pbar Quark-like pomeron has larger event rate and larger fraction of events without jets than Gluon-like pomeron Tevatron “gap” data from jet, b, J/Psi events favor hard-gluon pomeron, but rate is too high compared to extrapolation of DESY data. Tev data at 630 GeV further complicates the extrapolation picture. SCI model (Edin, Ingelman, Rathsman, J. Phys. G22, 943 (1996) , which does not involve pomerons, may better describe the data. Intact proton Can we do at higher luminosity?

Run I: 

Run I CDF: 8246 Wen ’s with a gap fraction of 1.15+-0.6. Jet distribution consistent with quark-like pomeron from the jet fraction, gluon-like for the absolute rate. DØ: 12622 W en ’s with gap fraction of 0.89 +-0.2%, 811 Z ee’s with gap fraction of 1.44+-0.6%. Event characteristics of diffracive and non-diffractive W’s agree well. Unlike diffractive jet events, central W’s have larger gap fraction than forward W’s Some discussion regarding how to correct for the fraction of diffractive events that do not contain a gap. If this is done, the measurements are not in as good of agreement as above implies (500% for DØ, 20% for CDF for pomeron model)

Run II: 

Run II Already same order as we had W’s in Run I

W/Z Cross Section: 

W/Z Cross Section New results from CDF for winter 2004 in all channels. http://tevewwg.fnal.gov/

PDF Uncertainty: 

PDF Uncertainty Michael Schmitt, Northwestern U, CDF Uncertainty on ratio of acceptances using CTEQ6 SF, LO calculation of the cross section, and a parameterization of the acceptance versus boson rapidity. CTEQ6 has a nominal PDF and 40 error PDF’s, corresponding displacing each of the X parameters by +/- 1 sigma.

Top Cross Section: 

Top Cross Section Theory cross sections Kidonakis NNLO-NNNLL hep-ph/0303185 Cacciari et al hep-ph/0303085 Uncertainty dominated by large-x gluon pdf and as


Prospects Both Collaborations expect many publications before summer.





Talks in Working Groups: 

Talks in Working Groups Jets – Alexei Safonov Dijet Mass - Pavel Demine Inclusive Jet Cross Section – Miroslav Kopal Underlying Event: Niccolo Moggi Diffraction – Koji Terashi Diffractive Z production/elastic results - Tamsin Edwards Pentaquarks: Igor Gorelov bottom and charm: Peter Bussey Upsilon and X – Franck Lehner B physics –Tulika Bose EWK: Susana Cabrera Top Physics – Sebastien Greder Top: Roman Lysak SUSY Searches – Tibor Kurca B decays: Simone Donati Leptoquarks: Dan Ryan Other searchs: Arnold Pompos Higgs Physics – Stephanie Beauceron

authorStream Live Help