Search results for "Gluon"
showing 10 items of 697 documents
Quark gap equation with non-Abelian Ball-Chiu vertex
2018
The full quark-gluon vertex is a crucial ingredient for the dynamical generation of a constituent quark mass from the standard quark gap equation, and its non-transverse part may be determined exactly from the nonlinear Slavnov-Taylor identity that it satisfies. The resulting expression involves not only the quark propagator, but also the ghost dressing function and the quark-ghost kernel, and constitutes the non-abelian extension of the so-called "Ball-Chiu vertex", known from QED. In the present work we carry out a detailed study of the impact of this vertex on the gap equation and the quark masses generated from it, putting particular emphasis on the contributions directly related with t…
Elliptic Flow in Pb-Pb Collisions at
2017
We report a precise measurement of the J/ψ elliptic flow in Pb-Pb collisions at sNN=5.02 TeV with the ALICE detector at the LHC. The J/ψ mesons are reconstructed at midrapidity (|y|<0.9) in the dielectron decay channel and at forward rapidity (2.5<y<4.0) in the dimuon channel, both down to zero transverse momentum. At forward rapidity, the elliptic flow v2 of the J/ψ is studied as a function of the transverse momentum and centrality. A positive v2 is observed in the transverse momentum range 2<pT<8 GeV/c in the three centrality classes studied and confirms with higher statistics our earlier results at sNN=2.76 TeV in semicentral collisions. At midrapidity, the J/ψ v2 is investigated as …
Subjet multiplicity of gluon and quark jets reconstructed with thek⊥algorithm inpp¯collisions
2002
The D empty set Collaboration has studied for the first time the properties of hadron-collider jets reconstructed with a successive-combination algorithm based on relative transverse momenta (k(perpendicular to)) of energy clusters. Using the standard value D = 1.0 of the jet-separation parameter in the k(perpendicular to) algorithm, we find that the p(T) of such jets is higher than the E-T of matched jets reconstructed with cones of radius R = 0.7, by about 5 (8) GeV at p(T) approximate to90 (240) GeV. To examine internal jet structure, the k(perpendicular to) algorithm is applied within D = 0.5 jets to resolve any subjets. The multiplicity of subjets in jet samples at roots = 1800 GeV and…
Non-cancellation of electroweak logarithms in high-energy scattering
2014
We study electroweak Sudakov corrections in high energy scattering, and the cancellation between real and virtual Sudakov corrections. Numerical results are given for the case of heavy quark production by gluon collisions involving the rates $gg \to t \bar t, b \bar b, t \bar b W, t \bar t Z, b \bar b Z, t \bar t H, b \bar b H$. Gauge boson virtual corrections are related to real transverse gauge boson emission, and Higgs virtual corrections to Higgs and longitudinal gauge boson emission. At the LHC, electroweak corrections become important in the TeV regime. At the proposed 100 TeV collider, electroweak interactions enter a new regime, where the corrections are very large and need to be re…
New results from lattice QCD: Non-perturbative renormalization and quark masses
1998
For the first time, we compute non-perturbatively, i.e. without lattice perturbation theory, the renormalization constants of two-fermion operators in the quenched approximation at $\beta=6.0$, 6.2 and 6.4 using the Wilson and the tree-level improved SW-Clover actions. We apply these renormalization constants to fully non-perturbatively estimate quark masses in the $\bar{MS}$ scheme from lattice simulations of both the hadron spectrum and the Axial Ward Identity in the quenched approximation. Some very preliminary unquenched Wilson results obtained from the gluon configurations generated by the T$\chi$L Collaboration at $\beta=5.6$ and $N_{f}=2$ are also discussed.
Parton polarization and constituent quarks
1995
Abstract A systematic study of the polarized-parton distributions is presented and related to the properties of the constituent quarks. The effects of breaking SU(6) symmetry are emphasized and the Isgur-Karl constituent model is discussed in detail. The results on the proton, neutron and deuteron structure functions are compared with the recent experimental data, and the role of the gluon polarization is pointed out. The role of the D-state admixture in the nucleon ground state is also investigated.
Dimensionally regularized box and phase-space integrals involving gluons and massive quarks
1999
The basic box and phase space integrals needed to compute at second order the three-jet decay rate of the Z-boson into massive quarks are presented in this paper. Dimensional Regularization is used to regularize the infrared divergences that appear in intermediate steps. Finally, the cancellation of these divergences among the virtual and the real contributions is showed explicitly.
From RHIC to LHC
2007
Measurements of the nuclear modification factor of inclusive yields of $\pi^0$, $p\bar{p}$, non-phtonic electrons and prompt photon measured at RHIC are reviewed. Some of the difficulties arising from interpretation of these measurements such as similarity of the suppression pattern of light and heavy quarks, quarks and gluons, light quarks and prompt photon are discussed. The potential of two-particle and promt photon correlation technique to unravel some of these open questions is presented. An emphasis is given to the influence of partonic transverse momentum on the prompt-photon correlations. The smearing between the trigger photon and back-to-back jet at LHC energy is discussed.
Longitudinal Spin Physics at COMPASS
2012
Abstract The spin structure of the nucleon is studied by the COMPASS collaboration using scattering of muons off polarised protons and deuterons. From the resulting asymmetries spin structure functions are extracted and the flavour decomposition of the quark contribution to the nucleon spin is studied. The gluon polarisation is investigated using the photon–gluon fusion process. Here, two main channels are investigated, open charm production and high p T hadron pair production. Also first measurements of unpolarised cross sections are reported.
On the rigidity of back-to-back top quark pairs in e^+e^- annihilation
1998
We consider the effect of gluon radiation on the energy of top/antitop quarks and on the anticollinearity of top-antitop quark pairs produced in $e^+e^-$ annihilation. Our results are presented in terms of the $E_q$-dependence of the $t\bar tg$ cross section and the dependence on the cosine of the opening angle $\theta_{12}$ between top and antitop for a center of mass energy of $\sqrt{q^2}=500 GeV$. We then go on to determine mean values for the top quark's energy as well as its longitudinal and transverse projections, and for the deviation of $\sin\theta_{12}$ and $\cos\theta_{12}$ from the anticollinearity limits $\sin\theta_{12}=0$ and $\cos\theta_{12}=-1$. For a center of mass energy o…