Search results for " QCD"
showing 10 items of 463 documents
Extraction of K --> pi pi matrix elements with Wilson fermions
2001
We present the status of a lattice calculation for the K-->pipi matrix elements of the (delta S=1) effective weak Hamiltonian, directly with two pion in the final state. We study the energy shift of two pion in a finite volume both in the I=0 and I=2 channels. We explain a method to avoid the Goldstone pole contamination in the computation of renormalization constants for (delta I=3/2) operators. Finally we show some preliminary results for the matrix elements of (delta I=1/2) operators. Our quenched simulation is done at beta=6.0, with Wilson fermions, on a (24^3 X 64) lattice.
Predictions for cold nuclear matter effects in p+Pb collisions at sNN=8.16 TeV
2018
Predictions for cold nuclear matter effects on charged hadrons, identified light hadrons, quarkonium and heavy flavor hadrons, Drell–Yan dileptons, jets, photons, gauge bosons and top quark pairs produced in p +Pb collisions at sNN=8.16 TeV are compiled and, where possible, compared to each other. Predictions of the normalized ratios of p +Pb to p+p cross sections are also presented for most of the observables, providing new insights into the expected role of cold nuclear matter effects. In particular, the role of nuclear parton distribution functions on particle production can now be probed over a wider range of phase space than ever before.
Covariant approximation averaging
2015
We present a new class of statistical error reduction techniques for Monte-Carlo simulations. Using covariant symmetries, we show that correlation functions can be constructed from inexpensive approximations without introducing any systematic bias in the final result. We introduce a new class of covariant approximation averaging techniques, known as all-mode averaging (AMA), in which the approximation takes account of contributions of all eigenmodes through the inverse of the Dirac operator computed from the conjugate gradient method with a relaxed stopping condition. In this paper we compare the performance and computational cost of our new method with traditional methods using correlation…
A measurement of the ratio of the W and Z cross sections with exactly one associated jet in pp collisions at with ATLAS
2012
The ratio of production cross sections of the W and Z bosons with exactly one associated jet is presented as a function of jet transverse momentum threshold. The measurement has been designed to ma ...
Measurement of the differential cross section of photon plus jet production inpp¯collisions ats=1.96 TeV
2013
We study the process of associated photon and jet production, p (p) over bar -> gamma + jet + X, using 8.7 fb(-1) of integrated luminosity collected by the D0 detector at the Fermilab Tevatron Collider at a center-of-mass energy root s = 1.96 TeV. Photons are reconstructed with rapidity vertical bar y(gamma)vertical bar 20 GeV. The highest-p(T) jet is required to be in one of four rapidity regions up to vertical bar y(jet)vertical bar 0) and opposite signs (y(gamma)y(jet) <= 0) of photon and jet rapidities. We compare the measured triple-differential cross sections, d(3)sigma/dp(T)(gamma)dy(gamma)dy(jet), to next-to-leading order (NLO) perturbative QCD calculations using different sets of p…
Precision measurements of B(D+→μ+νμ), the pseudoscalar decay constant fD+, and the quark mixing matrix element |Vcd|
2014
We report a measurement of the branching fraction B(D+ -> mu(+)nu(mu)) = [3.71 +/- 0.19(stat) +/- 0.06(sys)] x 10(-4) based on 2.92 fb(-1) of data accumulated at root s = 3.773 GeV with the BESIII detector at the BEPCII collider. This measurement, in conjunction with the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V-cd vertical bar determined from a global Standard Model fit, implies a value for the weak decay constant f(D+) = (203.2 +/- 5.3 +/- 1.8) MeV. Additionally, using this branching fraction measurement together with a lattice QCD prediction for f(D+), we find vertical bar V-cd vertical bar 0.2210 +/- 0.0058 +/- 0.0047. In either case, these are the most precise results for…
The magnetic moment of the ρ-meson
2014
The magnetic moment of the \rho-meson is calculated in the framework of a low-energy effective field theory of the strong interactions. We find that the complex-valued strong interaction corrections to the gyromagnetic ratio are small leading to a value close to the real leading tree level result, g_\rho = 2. This is in a reasonably good agreement with the available lattice QCD calculations for this quantity.
From quark-gluon plasma to hadron spectra
2001
Results on initial transverse energy production based on NLO perturbative QCD calculation with final state saturation of produced minijets are used to fix the initial energy density of produced matter. Assuming rapid thermalization, this provides the initial conditions for a hydrodynamic description of the expansion of final matter. Given a prescription of the the decoupling of particles from the thermal system to free particles, final transverse spectra of hadrons and integrated quantities like multiplicity and transverse energy can be calculated in the central rapidity region. Results are reported and compared with measurements.
Studies ofWboson plus jets production inpp¯collisions ats=1.96 TeV
2013
We present a comprehensive analysis of inclusive W(-> ev) + n-jet (n >= 1, 2, 3, 4) production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV at the Tevatron collider using a 3.7 fb(-1) data set collected by the D0 detector. Differential cross sections are presented as a function of the jet rapidities (y), lepton transverse momentum (P-T) and pseudorapidity (eta), the scalar sum of the transverse energies of the W boson and all jets (H-T), leading dijet P-T and invariant mass, dijet rapidity separations for a variety of jet pairings for P-T-ordered and angular-ordered jets, dijet opening angle, dijet azimuthal angular separations for P-T-ordered and angular-ordered j…
The perturbative QCD prediction to Rτ revisited
1992
6 páginas, 3 figuras, 1 tabla.-- CERN-TH-6421-92 ; LAL-92-09.