Session H13: QCD Physics

FCNC Top Quark Production Via Anomalous Gluon Coupling

We calculate flavor-changing neutral current (FCNC) processes with top-quark production via anomalous gluon couplings at various LHC energies. We present the FCNC process $p p \to t g$. We go beyond leading order and include soft-gluon corrections through next-to-next-to-leading order. Additionally, we report the impact of QCD scale variation on the cross section.   

Radii of protons and a way to resolve the proton size puzzle

How to determine radii of protons is a hot topic in recent particle physics. From the research, one can gain information about proton structure and quark-quark interaction, and test quantum chromodynamics and quantum electrodynamics. In this paper, we study radii of protons in terms of wave functions and the way to resolve the proton size puzzle.   

Study of double parton interactions in photon + 3 jets events and photon + $b/c$ + 2 jets events at the Tevatron

We have used a sample of photon + 3 jets as well as photon + $b/c$ + 2 jet events collected by the D0 experiment with an integrated luminosity of 8.7 fb$^{-1}$ to determine the fraction of events with hard double parton (DP) scattering in a single proton-antiproton collision at $\sqrt{s}=1.96$ TeV. The DP fraction and effective cross section, a process-independent scale parameter related to the parton density inside the nucleon, are measured in the kinematic region $p_{\rm T}^{\gamma}>$26 GeV, $p_{\rm T}^{\rm jet1}>$15 GeV, and 15 $\leq p_{\rm T}^{\rm jet2,3}\leq$ 35 GeV.   

Signal Reconstruction and Performance of the ATLAS Hadronic calorimeter

The Tile Calorimeter (TileCal) of the ATLAS experiment is the hadronic calorimeter designed for energy reconstruction of hadrons, jets, tau-particles and missing transverse energy. Latest results on calibration, signal reconstruction and performance of the TileCal detector using pp collision data are presented. The studies of the TileCal response to single isolated charged particles and the noise description with increasing pile-up are presented. In addition, TileCal upgrade plans are discussed.   

Comparisons of Exact Amplitude--Based Resummation Predictions and LHC Data

We present the current status of the comparisons with the respective data of the predictions of our approach of exact amplitude-based resummation in quantum field theory as applied to precision QCD calculations as needed for LHC physics. The agreement between the theoretical predictions and the data exhibited continues to be encouraging.   

Measurements of $W+b+X$ and $W+c+X$ production cross sections at the Tevatron

Studies of associated production of a $W$ boson with heavy quark ($b/c$) jets provide important tests of perturbative quantum chromodynamics calculations. A good understanding of such processes is also essential because they constitute a major background to the production of the standard model Higgs boson in association with a $W$ boson. We present measurements of $W+b+X$ and $W+c+X$ production using Run 2 Tevatron data collected by the D0 detector. The measurements are performed for the integrated acceptance as well as differentially as a function of leading jet transverse momenta. These results are compared to theory calculations as well as prediction from Monte Carlo generators.   

Topological insulators and the QCD vacuum: the theta parameter as a Berry phase

There is considerable evidence, based on large $N_c$ chiral dynamics, holographic QCD, and Monte Carlo studies, that the QCD vacuum is permeated by discrete quasivacua separated by domain walls across which the local value of the topological $\theta$ parameter jumps by $\pm2\pi$. This scenario is realized in a 2-dimensional U(1) gauge theory, the $CP^{N-1}$ sigma model, where a pointlike charge is a domain wall, and $\theta$ describes the background electric flux and the polarization of charged pairs in the vacuum. The transition between discrete $\theta$ vacua occurs via the transport of integer units of charge between the two spatial boundaries of the domain. We show that this screening process, and the role of $\theta$ as an order parameter describing electric polarization, are naturally formulated in terms of Bloch wave eigenstates of the Dirac Hamiltonian in the background gauge field. This formulation is similar to the Berry phase description of electric polarization and quantized charge transport in topological insulators.   

Measurements of the prompt single $J/\psi$ and double $J/\psi$ production cross section at the Tevatron

We present measurements of the production cross section of prompt $J/\psi$ mesons, as well as the cross section of simultaneous production of two prompt $J/\psi$ mesons, in proton-antiproton collisions at $\sqrt{s}=1.96$ TeV using 8.1 fb$^{-1}$ of Tevatron data collected by the D0 experiment. The latter cross section is separated into contributions due to single parton and double parton scatterings. The $J/\psi$ mesons are fully reconstructed in the muonic final states. Using these measurements, the effective cross section, a parameter characterizing an effective spatial area of parton-parton interaction and tightly related to the parton spatial density inside the nucleon, is also measured.   

Measurement of the muon charge asymmetry in inclusive pp to WX production at sqrt(s) = 7 TeV

Measurements of the muon charge asymmetry in inclusive pp to WX production at sqrt(s)=7 TeV are presented. The data sample corresponds to an integrated luminosity of 4.7 inverse femtobarns recorded with the CMS detector at the LHC. With a sample of more than twenty million W to mu nu events, the statistical precision is greatly improved in comparison to previous measurements. These new results provide additional constraints on the parton distribution functions of the proton in the range of the Bjorken scaling variable x from 10E-3 to 10E-1. These measurements are used together with the cross sections for inclusive deep inelastic ep scattering at HERA in a next-to-leading-order QCD analysis. The determination of the valence quark distributions is improved.