CDF Run II QCD Group Results

---

  Results are sorted as follows:

• Preliminary:
  • Jets
  • Heavy Flavor Jets
  • Underlying Event / Fragmentation
  • Diffraction / Exclusive Production

• Submitted

• Published

---

Preliminary: Jets

Inclusive Jet Production using the Midpoint Jet Algorithm

Document(s) Web Page       Phys. Rev. D 78, 052006 (2008)       hep-ex/0807.2204 Contact(s) A. Bhatti, F. Chlebana, G. Flanagan, G. Group, K. Hatakeyama, J. Huston and G. Latino Abstract We present a measurement of the inclusive jet cross section in p-pbar collisions at sqrt{s}=1.96 TeV based on data collected by the CDF II detector with an integrated luminosity of 1.13 fb^-1. The measurement was made using the cone-based Midpoint jet clustering algorithm in the rapidity region of |y|<2.1. The results are consistent with next-to-leading-order perturbative QCD predictions based on recent parton distribution functions (PDFs), and are expected to provide increased precision in PDFs at high parton momentum fraction x. The results are also compared to the recent inclusive jet cross section measurement using the k_T jet clustering algorithm, and we find that the ratio of the cross sections measured with the two algorithms is in agreement with theoretical expectations over a large range of jet transverse momentum and rapidity. Comments Last Update: June 2009       Dataset: 1.13 fb-1

Z+Jets

Document(s) Web Page       Phys. Rev. Lett. 100, 102001 (2008)       hep-ex/0711.3717 Contact(s) M. D'Onofrio, M. Martinez and O. Salto Abstract Inclusive jet cross sections in Z/γ* events, with Z/γ* decaying into an electron-positron pair, are measured as a function of jet transverse momentum and jet multiplicity in p-pbar collisions at √s = 1.96 TeV with the upgraded Collider Detector at Fermilab in Run II, based on an integrated luminosity of 1.7 fb-1. The measurements cover the rapidity region |yjet| < 2.1. and the transverse momentum range ptjet > 30 GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections. Comments Last Update: March 2008       Dataset: 1.7 fb-1

W + Jets

Document(s) Web Page       Public Note 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) Phys Rev D 80, 052011 (2009) Contact(s) A. Bocci Abstract We report on a search for the process ppbar -> &gamma+W/Z with W/Z to qqbar in events containing two jets and a photon at the center-of-mass energy sqrt(s)=1.96 TeV, using 184 pb-1 of data collected by the CDF II detector. A neural network event selection has been developed to optimize the rejection of the large QCD production background; it is shown that this method gives a significant improvement in both signal-to-noise ratio and signal sensitivity, as compared with an event selection on conventional cuts. An upper limit is presented for the &gamma+W/Z production cross section with the W and Z decaying hadronically. Comments Last Update: Sep 2009       Dataset: 184 pb-1

Preliminary: Heavy Flavor Jets

Inclusive b-jet Production

Document(s) Web Page       Public Note 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 using SVT

Document(s) Web Page       Public Note Contact(s) S. Vallecorsa Abstract We present a b-bbar jet cross section measurement based on about 260 pb-1 of data, collected by CDF Run II until September 2004. The analysis strongly relies on the CDF detector good tracking capabilities both at trigger level, as data is selected requiring two displaced tracks at Level 2, and offline, since b-tagging is performed reconstructing secondary vertices inside the jet. Jets are reconstructed using a cone algorithm. The cross section is measured in the central region (|eta|< 1.2) as a function of leading jet Et, b-bbar pair invariant mass and azimuthal angle between the two jets. Results are corrected to the hadron level and compared to Leading Order Monte Carlos (Pythia and Herwig) as well as MC@NLO predictions. Comments Last Update: April 2007       Dataset: 260 pb-1

Photon + Heavy Flavor Production

Document(s) Web Page       Public Note Contact(s) R. McNulty and T. Shears Abstract Measurements of photon + b jet production, obtained with a dataset of 340 pb-1, are presented. Cross-sections are measured for all events containing photons with transverse energy above 26 GeV, and differentially in bins of photon transverse energy between 26 and 70 GeV. Our results agree with leading order predictions. Comments Last Update: July 2006       Dataset: 340 pb-1

Photon + Heavy Flavor Production using SVT

Document(s) Web Page       Public Note Contact(s) M. Campanelli Abstract We present a study of the photon + b-jet production at the Tevatron in the CDF II detector. The analysis is performed with a dataset that makes use of the on-line tracking reconstruction provided by the SVT to enhance the b content and lower the photon Et threshold with respect to the inclusive photon sample. The trigger efficiency is measured directly from data. We considere events with Et(γ)>12 GeV, |η(γ)|<1.1, Et(j)>20 GeV, |η(j)|<1.5, and Δ R(jγ)>0.7, and measure the total cross section as well as the differential cross sections as a function of photon Et and b-jet Et. Comments Last Update: October 2006       Dataset: 208 pb-1

b-jet Shapes

Document(s) Web Page       Phys. Rev. D 78, 072005 (2008)       arXiv:0806.1699 Contact(s) A. Lister Abstract We present preliminary results on the integrated jet shapes of b-jets in inclusive b-jet production in p-pbar collisions at sqrt{s} = 1.96 TeV. The data used for this analysis were collected between February 2002 and September 2004 and represent an integrated luminosity of about 300 pb-1. The measurements are carried out for jets with rapidity | yjet | < 0.7 and transverse momentum between 52 and 300 GeV/c. The measured b-jet shapes are corrected to the particle level and compared to PYTHIA-Tune A and HERWIG predictions. Comments Last Update: October 2008       Dataset: 300 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       Public Note 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

Kt Distributions of Particles in Jets

Document(s) Web Page       PhysRevLett.102.232002       hep-ex/0803.4264 Contact(s) S. Jindariani, A. Korytov and A. Pronko Abstract We present a measurement of the transverse momentum with respect to the jet axis (kT) of particles in jets produced in p-pbar collisions at sqrt(s)=1.96 TeV. Results are obtained for charged particles within a cone of opening angle 0.5 radians around the jet axis in events with dijet invariant masses between 66 and 737 GeV/c2. The experimental data are compared to theoretical predictions obtained for fragmentation partons within the framework of resummed perturbative QCD using the modified leading log and next-to-modified leading log approximations. The comparison shows that trends in data are successfully described by the theoretical predictions, indicating that the perturbative QCD stage of jet fragmentation is dominant in shaping basic jet characteristics. Comments Last Update: June 2009       Dataset: 774 pb-1

Preliminary: Diffraction / Exclusive Production

Diffractive Dijet Production

Document(s) Web Page Contact(s) M. Gallinaro, K. Goulianos and K. Terashi Abstract Results are presented from a study of diffractive dijet production in p-pbar collisions at a center-of-mass energy of 1.96 TeV. The data sample consists of events collected by triggering on a high transverse energy jet in coincidence with a recoil antiproton detected in a Roman Pot Spectrometer (RPS). Approximately, the average jet transverse energy in an event is 12 GeV, and the fractional momentum loss of the recoil antiproton, ξ, and 4-momentun transfer squared, |t|, are in the range 0.03 < ξ < 0.1 and |t| < 0.1 GeV^2. We measure the ratio of single-diffractive (SD) to non-diffractive (ND) dijet event rates as a function of x-Bjorken and Q^2 in the range 10^-3 < x_Bj < 10^-1 and 10^2 < Q^2 < 100^2 GeV^2. We also measure the |t|-distribution of diffractive events as a function of Q^2 in the range |t| < 1 GeV^2 and Q^2 < 100^2 GeV^2. Our results confirm our Run I result on x_Bj dependence of the ratio of SD/ND event rates, show small Q^2 dependence in the SD/ND event ratio, and no observable Q^2 dependence in the diffractive |t|-distributions. These results reinforce the picture emerged from our Run I results for the diffractive exchange, the Pomeron, as evolving similarly to the proton. This picture is consistent with a composite Pomeron made up from a combination of proton PDFs, one on the hard scale that produces the jets and another (or others) on a soft scale responsible for neutralizing the color being exchanged and producing the rapidity gap. Comments Last Update: February 2006       Dataset: 128 pb-1

Dijet Production in DPE and Exclusive Dijet Production

Document(s) Web Page       Public Note Contact(s) M. Convery, M. Gallinaro, K. Goulianos, C. Mesropian, K. Terashi Abstract We present preliminary results from studies of dijet events produced in Double Pomeron Exchange (DPE), with some emphasis on results on search for exclusive dijet production. In a sample of about 310 pb-1 of Run II data collected with dedicated diffractive triggers, we observe an excess of data events over backgrounds obtained from inclusive DPE dijet Monte Carlo simulation. The observed excess is consistent with exclusive dijet Monte Carlo predictions in terms of kinematic distribution shapes. The cross sections of observed exclusive dijet events are measured using combinations of inclusive DPE and exclusive dijet Monte Carlo simulations. We also present results from studies of heavy flavor quark jets in DPE, particularly the suppression of the ratio of heavy flavor jets to inclusive jets expected in the exclusive kinematic region. The results are based on a sample of about 200 pb-1 of data collected after the Fall 2004 shutdown. We observe a decreasing trend in the ratio at the exclusive kinematic region and the observed behavior is consistent with what we expect for exclusive dijet signal that is present in the region. Comments Last Update: July 2006       Dataset: 310 pb-1

Exclusive γγ Production

Document(s) Web Page       Phys. Rev. Lett. 99, 242002 (2007)   [pdf]       hep-ex/0707.2374       Figures Contact(s) M. Albrow, B. Caron, A. Hamilton, B. Heinemann and J. Pinfold Abstract We have searched for exclusive 2-photon production in proton-antiproton collisions at sqrt{s} = 1.96 TeV, using 532 pb-1 of integrated luminosity taken by the Run II Collider Detector at Fermilab. The event signature requires two electromagnetic showers, each with transverse energy E_T > 5 GeV and pseudorapidity |eta| < 1.0, with no other particles detected in the event. Three candidate events are observed. We discuss the consistency of the three events with gamma-gamma, pi0-pi0, or eta-eta production. The probability that other processes fluctuate to 3 events or more is 1.7x10^-4. An upper limit on the cross section of p+pbar --> p+gamma-gamma+pbar is set at 410 fb with 95% confidence level. Comments Last Update: April 2006       Dataset: 532 pb-1

Exclusive χc Production

Document(s) Web Page Contact(s) A. Wyatt Abstract We report on a study of exclusive J/ψ + γ production. Using 93 pb-1 of CDF Run II data collected with a dimuon trigger, J/ψ events produced by Double Pomeron Exchange are selected. 10 events containing a J/ψ 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 χ_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/ψ + γ production has been extracted: 49 pb ± 18 (stat) ± 39 (syst), for | y | < 0.6. Comments Last Update: September 2003       Dataset: 93 pb-1

---

Submitted

Inclusive Jet Production using the Kt Algorithm

Document(s) Web Page       Phys. Rev. D 75, 092006 (2007)   [pdf] 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 pt ≥ 54 GeV/c in five different jet rapidity regions: |y| < 0.1, 0.1 < |y| < 0.7, 0.7 < |y| < 1.1, 1.1 < |y| < 1.6 and 1.6 < |y| < 2.1. Results are based on 1.0 fb-1 of CDF Run II data. 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 effects. Comments Last Update: August 2006       Dataset: 1.0 fb-1

---

Published

Exclusive e+e- Production

Document(s) Web Page       Phys. Rev. Lett. 98, 112001 (2007)   [pdf]       Figures Contact(s) M. Albrow, B. Caron, A. Hamilton, B. Heinemann and J. Pinfold Abstract We report on the first observation of exclusive production of electron pairs through two-photon exchange in hadron-hadron collisions at CDF. The cross section and kinematic distributions agree with theoretical predictions. Comments Last Update: April 2006       Dataset: 532 pb-1

Inclusive Jet Production using the Midpoint Jet Algorithm

Document(s) Web Page       Phys. Rev. D 74, 071103(R) (2006)   [pdf] 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

Z + b-jet

Document(s) Web Page       Phys. Rev. D 74, 032008 (2006)   [pdf] Contact(s) B. Heinemann and A. Mehta Abstract 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

Inclusive Jet Production using the Kt Algorithm

Document(s) Web Page       Phys. Rev. Lett. 96, 122001 (2006)   [pdf] 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

Prompt Diphoton Production

Document(s) Web Page       Phys. Rev. Lett. 95, 022003 (2005)   [pdf] 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)   [pdf] 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