CDF Run II QCD Group Results

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Preliminary: Jets

Inclusive Jet Production using the Midpoint Jet Algorithm

Document(s) Web Page Contact(s) A. Bhatti, F. Chlebana, G. Flanagan, G. Group, K. Hatakeyama and J. Huston Abstract We present a measurement of the inclusive jet cross section in p-pbar interactions at sqrt{s}=1.96 TeV using 1.04 fb-1 of data collected with the CDF II detector at the Fermilab Tevatron. The results are obtained using an improved cone-based jet algorithm (Midpoint). The measurement is carried out for jets with rapidity 0.1 < | yjet | < 0.7 and transverse momentum in the range 61 < ptjet < 620 GeV/c. The results are in good agreement with next-to-leading order perturbative QCD predictions using the CTEQ6.1M parton distribution functions. Comments Last Update: March 2006       Dataset: 1.04 fb-1

Inclusive Forward Jet Production using the Kt Algorithm

Document(s) Web Page Contact(s) R. Lefevre, M. Martinez and O. Norniella Abstract We present a study of the inclusive jet production cross section using the longitudinally invariant kt algorithm (Ellis-Soper inclusive mode) for jets with ptjet > 54 GeV/c in four different jet rapidity regions: | yjet | < 0.1, 0.7 < | yjet | < 1.1, 1.1 < | yjet | < 1.6 and 1.6 < | yjet | < 2.1. Results are based on 385 pb-1 of CDF Run II data and complement previous measurements in the region 0.1 < | yjet | < 0.7. Measurements are fully unfolded to the hadron level. The data is compared to pQCD NLO calculations as determined using JETRAD. The theoretical predictions are corrected for underlying event and hadronization. Comments Last Update: August 2005       Dataset: 385 pb-1

W + Jets

Document(s) Web Page Contact(s) B. Cooper, A. Messina and D. Waters Abstract We present a measurement of W + Jets differential cross sections for W production in association with at least n jets. The results are based on 320 pb-1 of CDF Run II data. The differential cross sections are measured as a function of jet Et, jet-jet delta R and jet-jet invariant mass. The measurements are corrected to the hadron level and compared to W + Jets Monte Carlo samples generated with Leading Order ALPGEN (v2) + PYTHIA, where the Monte Carlo has been normalised to the measured inclusive cross section for each jet multiplicity. Comments Last Update: February 2006       Dataset: 320 pb-1

Search for W/Z Hadronic Decays in Photon Events

Document(s) Web Page Contact(s) A. Bocci Abstract We report on a search for W/Z hadronic decays in photon events. The study is based on 184 pb-1 of CDF Run II data collected with a low pt photon trigger. A neural network technique is employed to select the diboson candidates. The limit is evaluated using a fully Bayesian approach taking into account all the systematic uncertainties. The 95% confident level upper limit on Sigma (p-pbar -> W Gamma) * BR (W -> q q') + Sigma (p-pbar -> Z Gamma) * BR (Z -> q qbar) is set to 54 pb, consistent with the NLO Standard Model prediction of 20.5 pb. Comments Last Update: June 2005       Dataset: 184 pb-1

Preliminary: Heavy Flavor Jets

Inclusive b-jet Production

Document(s) Web Page Contact(s) M. D'Onofrio Abstract We report on a measurement of the inclusive b-jet production cross section in p-pbar collisions at sqrt{s} = 1.96 TeV based on 300 pb-1 of data collected using the upgraded Collider Detector at Fermilab in Run II. The measurement is performed for jets with transverse momentum in the range 38 < ptjet < 400 GeV/c and rapidity | yjet | < 0.7. The measured cross section is in agreement with next-to-leading order perturbative QCD predictions. Comments Last Update: September 2005       Dataset: 300 pb-1

b-bbar Dijet Production

Document(s) Web Page       Public Note Contact(s) R. McNulty, A. Mehta and T. Shears Abstract We present preliminary measurements of the inclusive b-bbar jet production cross section using data taken by the CDF experiment at a centre-of-mass energy of 1.96 TeV. Two secondary vertex tagged jets within | eta | < 1.2 are required; one of these tagged jets has to have a corrected transverse energy greater than 30 GeV, the other has to have a corrected transverse energy greater than 20 GeV. We compare our results to Leading Order (PYTHIA and HERWIG) and Next to Leading Order (MC@NLO) predictions. Comments Last Update: April 2005

Z + b-jet

Document(s) Web Page Contact(s) B. Heinemann and A. Mehta Abstract A measurement of the single inclusive bottom jet cross section is measured for events containing a Z boson in p-pbar collisions at sqrt{s} = 1.96 TeV using the Collider Detector at Fermilab. Z bosons are identified in their electron and muon decay modes. b-jets with Et > 20 GeV and | eta | < 1.5 are identified by reconstructing a secondary decay vertex. The measurement is based on an integratd luminosity of 337 pb-1 for the electron decay mode and 324 pb-1 for the muon decay mode. We find a cross section of Sigma (Z+bjet, Z->l+l-) = 0.96 +/- 0.35 pb and the fraction of b-jets to the total number of jets in this sample is 2.39 +/- 0.86 %. This measurement is in agreement with NLO QCD predictions. Comments Last Update: September 2005       Dataset: 330 pb-1

Photon + Heavy Flavor Production

Document(s) Web Page       Public Note Contact(s) R. McNulty and T. Shears Abstract We measure the photon + b and photon + c cross sections and their ratio in p-pbar collisions at sqrt{s} = 1.96 TeV. We present cross sections both as a function of photon Et in order to test QCD predictions at different energy scales, and for all photons with an Et exceeding 25 GeV to gain maximal statistical sensitivity to deviations that could signal new physics production. Results are based on 67 pb-1 of CDF Run II data. They are compared to and found to be consistent with PYTHIA Leading Order predictions. Comments Last Update: November 2003       Dataset: 67 pb-1

Preliminary: Underlying Event / Fragmentation

Underlying Event in Inclusive Jet Production

Document(s) Web Page Contact(s) R. Field Abstract We study the behavior of the "underlying event" in hard scattering p-pbar collisions at sqrt{s} = 1.96 TeV and compare with PYTHIA Tune A and with our published Run I analysis. The "underlying event" is studied using both "charged particle jets" (as was done in our Run I analysis) and using "calorimeter jets". As expected the properties of the "underlying event" are the same for both the "charged particle jet" and the "calorimeter jet" approach and both agree with the Run I analysis. Comments Last Update: April 2003       Dataset: 75 pb-1

Two-Particle Momentum Correlations in Jets

Document(s) Web Page Contact(s) S. Jindariani, A. Korytov and A. Pronko Abstract We report on measurements of two-particle momentum correlations in jets produced in p-pbar collisions at sqrt{s} = 1.96 TeV. Studies were performed for charged particles within a restricted opening angle of 0.5 rad around the jet axis and for dijet events with masses ranging from about 60 to 600 GeV. Comparison of the experimental results to the theoretical predictions obtained for partons within the framework of the resummed perturbative QCD (Next-to-leading Log Approximation) shows that the parton momentum correlations do survive the hadronization stage of jet fragmentation, thus giving further support to the hypothesis of Local Parton-Hadron Duality. Comments Last Update: October 2005       Dataset: 385 pb-1

Preliminary: Diffraction / Exclusive Production

Diffractive Dijet Production

Document(s) Web Page Contact(s) M. Gallinaro, K. Goulianos, K. Hatakeyama, C. Mesropian and K. Terashi Abstract The diffractive dijet events studied are characterized by the presence of two jets resulting from a hard scattering and a leading antiproton, which escapes the collision intact. Using Run II data and dedicated diffractive triggers, a measurement of the diffractive structure function of the antiproton and a study of Double Pomeron Exchange (DPE) event candidates are presented. Comments Last Update: March 2003       Dataset: 9 pb-1

Dijet Production in Double Pomeron Exchange

Document(s) Web Page Contact(s) M. Convery, M. Gallinaro, K. Goulianos, C. Mesropian, K. Terashi Abstract We present results from studies of dijet events produced in Double Pomeron Exchange (DPE) in Run II. We use about 26 pb-1 of CDF data collected with diffractive triggers. Results on exclusively produced dijet events in DPE trigger data are emphasized. Comments Last Update: May 2003       Dataset: 26 pb-1

Exclusive e+e- and Exclusive Diphoton Productions

Document(s) Web Page Contact(s) M. Albrow, B. Caron, A. Hamilton, B. Heinemann and J. Pinfold Abstract We report on a search for exclusive e+e- and exclusive diphoton. Using 325 pb-1 of CDF Run II data collected with a dedicated trigger, 10 e+e- and 3 diphoton candidates were found. Backgrounds have not been estimated yet. Comments Last Update: December 2005       Dataset: 325 pb-1

Exclusive chi_c Production

Document(s) Web Page Contact(s) A. Wyatt Abstract We report on a study of exclusive J/Psi + gamma production. Using 93 pb-1 of CDF Run II data collected with a dimuon trigger, J/Psi events produced by Double Pomeron Exchange are selected. 10 events containing a J/Psi and a photon candidate but nothing else visible in the full detector including the very forward regions are observed. Those events are consistent with potentially being from chi_c decays. Since the background from multiplicity fluctuations in Double Pomeron Exchange has not been estimated yet, an upper limit on the cross section for exclusive J/Psi + gamma production has been extracted: 49 pb +/- 18 (stat) +/- 39 (syst), for | y | < 0.6. Comments Last Update: September 2003       Dataset: 93 pb-1

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Submitted

Inclusive Jet Production using the Midpoint Jet Algorithm

Document(s) Web Page       hep-ex/0512020 (Submitted to PRL) Contact(s) A. Bhatti, F. Chlebana, G. Flanagan, K. Hatakeyama, J. Huston and G.Latino Abstract We present a measurement of the inclusive jet cross section in p-pbar interactions at sqrt{s}=1.96 TeV using 385 pb-1 of data collected with the CDF II detector at the Fermilab Tevatron. The results are obtained using an improved cone-based jet algorithm (Midpoint). The measurement is carried out for jets with rapidity 0.1 < | yjet | < 0.7 and transverse momentum in the range 61 < ptjet < 620 GeV/c. The results are in good agreement with next-to-leading order perturbative QCD predictions using the CTEQ6.1M parton distribution functions. Comments Last Update: October 2005       Dataset: 385 pb-1

Inclusive Jet Production using the Kt Algorithm

Document(s) Web Page       hep-ex/0512062 (Accepted by PRL) Contact(s) R. Lefevre, M. Martinez and O. Norniella Abstract We report on a measurement of the inclusive jet production cross section in p-pbar collisions at sqrt{s} = 1.96 TeV using data collected with the upgraded Collider Detector at Fermilab in Run II corresponding to an integrated luminosity of 385 pb-1. Jets are reconstructed using the kt algorithm. The measurement is carried out for jets with rapidity 0.1 < | yjet | < 0.7 and transverse momentum in the range 54 < ptjet < 700 GeV/c. The measured cross section is in good agreement with next-to-leading order perturbative QCD predictions after the necessary non-perturbative parton-to-hadron corrections are included. Comments Last Update: September 2005       Dataset: 385 pb-1

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Published

Prompt Diphoton Production

Document(s) Web Page       Phys. Rev. Lett. 95, 022003 (2005) Contact(s) R. Blair, R. Culbertson, J. Huston, S. Kuhlmann, Y. Liu and X. Wu Abstract We report a measurement of the rate of prompt diphoton production in p-pbar collisions at sqrt{s} = 1.96 TeV using a data sample of 207 pb-1 collected with the upgraded Collider Detector at Fermilab. The background from nonprompt sources is determined using a statistical method based on differences in the electromagnetic showers. The cross section is measured as a function of the diphoton mass, the transverse momentum of the diphoton system, and the azimuthal angle between the two photons and is found to be consistent with perturbative QCD predictions. Comments Last Update: August 2004       Dataset: 207 pb-1

Jet Shapes in Inclusive Jet Production

Document(s) Web Page       Phys. Rev. D 71, 112002 (2005) Contact(s) M. Martinez Abstract We report on a study of jet shapes in inclusive jet production in p-pbar collisions at sqrt{s} = 1.96 TeV using the upgraded collider detector at Fermilab in Run II and based on an integrated luminosity of 170 pb-1. Measurements are carried out on jets with rapidity 0.1 < | yjet | < 0.7 and transverse momentum 37 < ptjet < 380 GeV/c. The jets have been corrected to the hadron level. The measured jet shapes are compared to leading-order QCD parton-shower Monte Carlo predictions as implemented in the PYTHIA and HERWIG programs. PYTHIA, tuned to describe the underlying event as measured in CDF Run I, provides a better description of the measured jet shapes than does PYTHIA or HERWIG with their default parameters. Comments Last Update: April 2004       Dataset: 170 pb-1