Bulletin of the American Physical Society
APS April Meeting 2011
Volume 56, Number 4
Saturday–Tuesday, April 30–May 3 2011; Anaheim, California
Session E8: QCD Physics |
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Sponsoring Units: DPF Chair: Laura Reina, Florida State University Room: Grand F |
Saturday, April 30, 2011 3:30PM - 3:42PM |
E8.00001: Measurement of Dijet Azimuthal Decorrelations in Proton-Antiproton Collisions at $\sqrt{s}=1.96$ TeV Kiran Chakravarthula Azimuthal decorrelations of dijets have been measured in collisions of proton and anti-protons at $\sqrt{s}=1.96$ TeV with the D0 detector at the Fermilab Tevatron Collider. The transverse jet momentum dependence is measured in different regions of the dijet scattering angle. The results are compared with predictions from perturbative QCD at next-to-leading order in the strong coupling constant. [Preview Abstract] |
Saturday, April 30, 2011 3:42PM - 3:54PM |
E8.00002: ABSTRACT WITHDRAWN |
Saturday, April 30, 2011 3:54PM - 4:06PM |
E8.00003: Study of Baryon Production in $e^+e^-$ Annihilation near 10 GeV at {\sc BaBar} Darren M. Jennings, David N. Brown Electron-positron annihilation provides a clean environment in which to study particle production in QCD processes. Using approximately $100 fb^{-1}$ of data collected by the {\sc BaBar} detector at the SLAC National Accelerator Laboratory, we study how the production of protons and $\Lambda^0$ baryons depends on event topology and jets. We also investigate angular correlations between baryons in events. [Preview Abstract] |
Saturday, April 30, 2011 4:06PM - 4:18PM |
E8.00004: Inclusive Hadron Production in $e^+e^-$ Annihilation near 10 GeV at {\sc BaBar} Adam D. Braun, David N. Brown Electron-positron annihilation provides a clean environment in which to study particle production in QCD processes. Using approximately $100 fb^{-1}$ of data collected by the {\sc BaBar} detector at the SLAC National Accelerator Laboratory, we measure inclusive production rates for a variety of charged and neutral hadrons produced in the continuum and at the $\Upsilon(2{\rm S})$ and $\Upsilon(3{\rm S})$ peaks. [Preview Abstract] |
Saturday, April 30, 2011 4:18PM - 4:30PM |
E8.00005: Measurement of Collins Asymmetries in inclusive production of pion pairs in $e^+e^-$ collisions at {\sc BaBar} Isabella Garzia The transversity distribution function, which describes the quark transverse polarization inside a transversely polarized nucleon, is the least known leading-twist component of the QCD description of the partonic structure of the nucleon. Transversity can be extracted from semi-inclusive deep inelastic scattering data, where, however, it couples to a new, unknown fragmentation function, called the Collins function. We present a measurement of the azimuthal asymmetries in the process $e^+e^- \rightarrow q\bar{q} \to \pi \pi X$, where the two pions are produced in opposite hemispheres, based on a data sample collected by the {\sc BaBar} experiment at a center-of-mass energy of about 10 GeV. The Collins function is extracted from the measured asymmetries. [Preview Abstract] |
Saturday, April 30, 2011 4:30PM - 4:42PM |
E8.00006: Charged particle multiplicities in proton-proton collisions at 900 GeV and 7 TeV center of mass energies Remi Zaidan The measurement of the charged particle multiplicities with the ATLAS detector in inelastic $p-p$ collisions at center of mass energies of 900 GeV and 7 TeV are presented. The charged particle density, its dependence on pseudo-rapidity and transverse momentum and its correlation with the average transverse momentum is measured for events with at least two charged particles in the kinematic range $|\eta| < 2.5$ and $p_T > 100$ MeV. The measurements are compared to different Monte Carlo model predictions. [Preview Abstract] |
Saturday, April 30, 2011 4:42PM - 4:54PM |
E8.00007: Measurement of underlying event characteristics using charged particles in pp collisions at $\sqrt{s} = 7 TeV$ with the ATLAS detector at the LHC Joseph Virzi We construct ``track jets'' by applying an anti-Kt algorithm to charged tracks reconstructed in the ATLAS detector, and measure charged particle distributions in the region transverse to the track jet with largest $p_{T}$ (leading track jet). The measurements are based on data collected using a minimum bias trigger to select proton-proton collisions at 7 TeV center-of-mass energy at the Large Hadron Collider. The underlying event (UE) is defined as those aspects of a hadronic interaction attributed not to the hard scattering process, but rather to the accompanying interactions of the rest of the proton. We characterize the underlying event by measuring the $\Sigma p_{T}$ and multiplicity for tracks transverse to the leading jet. The transverse region is defined by $2 \pi / 3 \le \phi < 4 \pi / 3$, where $\phi$ is the azimuthal angle defined relative to the leading track jet. Tracks and jets are required to have $|\eta| \le 1.9$. The data show a higher underlying event activity than that predicted by Monte Carlo models tuned to pre-LHC data. [Preview Abstract] |
Saturday, April 30, 2011 4:54PM - 5:06PM |
E8.00008: Measurement of the Underlying Event Activity in $pp$ collisions at $\sqrt{s} = 0.9$~TeV and 7 TeV Mohammed Zakaria A measurement of the underlying activity in scattering processes with a $p_T$ scale of several GeV/$c$ is performed in proton-proton collisions at $\sqrt{s} = 7$~TeV using corrected data collected by the CMS experiment at the LHC. The production of charged particles is studied with reference to the azimuthal direction of the leading track-jet with $|\eta| < 2$ and $p_T > 0.5$~GeV/$c$. A significant increase of the average number of charged particles and of the average scalar $p_T$ sum is observed followed by a saturation at large values of the $p_T$ scale. A significant growth of the activity in the transverse region is observed when increasing the leading track-jet cut for the same energy or when increasing the energy from $\sqrt{s} = 0.9$~TeV to $\sqrt{s} = 7$~TeV. Various PYTHIA based QCD-inspired models are compared with the data after full detector simulation. [Preview Abstract] |
Saturday, April 30, 2011 5:06PM - 5:18PM |
E8.00009: Measurement of the Isolated Prompt Photon Production Cross Section at CMS Abraham de Benedetti We measure the differential cross section for the inclusive production of isolated prompt photons. This measurement uses data recorded by the CMS detector at the LHC in 2010 with proton-proton collisions having a center of mass energy of 7 TeV. The measurement of photon production at the LHC adds to our understanding of the Standard Model and is important for future investigations of new physics. The cross section is compared to the Standard Model with next-to-leading-order perturbative QCD calculations. [Preview Abstract] |
Saturday, April 30, 2011 5:18PM - 5:30PM |
E8.00010: Measurement of Photon+Jet Cross Section at CMS Michael Anderson Events with photon + jet in the final state are a useful probe of hard scattering in QCD process, and are an important source of background to new physics seraches. Here, we present a measurement of the photon+jet differential cross section by comparing the ratio of production cross sections with respect to jet and photon rapidities in proton-proton collisions at center-of-mass energy of 7 TeV with the Compact Muon Solenoid detector at CERN. [Preview Abstract] |
Saturday, April 30, 2011 5:30PM - 5:42PM |
E8.00011: Search for New Physics in the Dijet Centrality Ratio in CMS Daniel Miner We describe a search for new physics in dijet production, using the early LHC pp data at $\sqrt{s} = 7$~TeV recorded by the CMS detector at CERN. The study is based on the dijet centrality ratio, which is the ratio of the number of events where the two leading jets have pseudorapidity $|\eta| < 0.7$ to the number where both leading jets have $0.7 < |\eta| < 1.3$. The dijet centrality ratio is a measure of the angular distribution of the dijets and is sensitive to deviations from the standard model. We measure the centrality ratio as a function of the invariant mass of the dijet system and find good agreement with the predictions of QCD, allowing us to set limits on the presence of new physics. [Preview Abstract] |
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