Search results for "Charm quark"
showing 9 items of 59 documents
Splittings of low-lying charmonium masses at the physical point
2019
We present high-precision results from lattice QCD for the mass splittings of the low-lying charmonium states. For the valence charm quark, the calculation uses Wilson-clover quarks in the Fermilab interpretation. The gauge-field ensembles are generated in the presence of up, down, and strange sea quarks, based on the improved staggered (asqtad) action, and gluon fields, based on the one-loop, tadpole-improved gauge action. We use five lattice spacings and two values of the light sea quark mass to extrapolate the results to the physical point. An enlarged set of interpolating operators is used for a variational analysis to improve the determination of the energies of the ground states in ea…
Search for Scalar Charm Quark Pair Production inppCollisions ats=8 TeVwith the ATLAS Detector
2015
The results of a dedicated search for pair production of scalar partners of charm quarks are reported. The search is based on an integrated luminosity of 20.3 fb(-1) of pp collisions at root s = 8 TeV recorded with the ATLAS detector at the LHC. The search is performed using events with large missing transverse momentum and at least two jets, where the two leading jets are each tagged as originating from c quarks. Events containing isolated electrons or muons are vetoed. In an R-parity-conserving minimal super-symmetric scenario in which a single scalar-charm state is kinematically accessible, and where it decays exclusively into a charm quark and a neutralino, 95% confidence-level upper li…
Up, down, strange and charm quark masses withNf=2+1+1twisted mass lattice QCD
2014
Abstract We present a lattice QCD calculation of the up, down, strange and charm quark masses performed using the gauge configurations produced by the European Twisted Mass Collaboration with N f = 2 + 1 + 1 dynamical quarks, which include in the sea, besides two light mass degenerate quarks, also the strange and charm quarks with masses close to their physical values. The simulations are based on a unitary setup for the two light quarks and on a mixed action approach for the strange and charm quarks. The analysis uses data at three values of the lattice spacing and pion masses in the range 210 – 450 MeV , allowing for accurate continuum limit and controlled chiral extrapolation. The quark …
K--pipi amplitudes from lattice QCD with a light charm quark.
2006
4 pages, 1 figure.-- PACS nrs.: 12.38.Gc, 13.25.Es, 11.30.Rd.-- ISI Article Identifier: 000244420700019.-- ArXiv pre-print available at: http://arxiv.org/abs/hep-ph/0607220
O(αs) longitudinal spin polarization in heavy-quark production
1995
We present the massive one-loop QCD corrections to the production cross sections of polarized quarks in the annihilation process ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}qq\ifmmode\bar\else\textasciimacron\fi{}(g) for bottom, top, and charm quarks. From the full analytical expressions for the production cross sections, Schwinger-type interpolation formulas for all parity-parity combinations (VV, VA, AA) are derived. The parity-odd interpolation formula contains the correct limit for vanishing quark masses taking into account a residual coupling of left- and right-chiral states in the massless theory. Numerical results for the total cross section and …
First Measurement of Boson Production in Association with a Single Charm Quark in Collisions at
2008
The authors present the first measurement of the production cross section of a W boson with a single charm quark (c) in p{bar p} collisions at {radical}s = 1.96 TeV, using soft muon tagging of c jets. In a data sample of {approx} 1.8 fb{sup -1}, recorded with the CDF II detector at the Fermilab Tevatron, they select events with W + 1 or 2 jets. They use the charge correlation between the W and the muon from the semileptonic decay of a charm hadron to extract the We signal. They measure {sigma}{sub Wc} (p{sub Tc} > 20 GeV/c, |{eta}{sub c}| < 1.5) x BR(W {yields} {ell}{nu}) = 9.8 {+-} 3.2 pb, in agreement with theoretical expectations.
In depth analysis of the combined HERA data in the dipole models with and without saturation
2018
We present an updated impact parameter dependent saturation model (IPsat) determined trough a fit to the combined HERA I and I+II reduced cross section data. The same HERA data are used to fit the linearized (IPnonsat) version of the applied dipole amplitude, which makes it possible to estimate the magnitude of the saturation effects in various experiments. We find that both parametrizations provide comparable descriptions of the considered data when an effective confinement scale dynamics is incorporated with quark masses. Moreover, it is possible to consistently determine the light and charm quark masses. The role of potentially non-perturbatively large dipoles is examined in detail, with…
Narrow Bound States of the DNN System
2012
We report on a recent calculation of the properties of the $DNN$ system, a charmed meson with two nucleons. The system is analogous to the $\bar K NN$ system substituting a strange quark by a charm quark. Two different methods are used to evaluate the binding and width, the Fixed Center approximation to the Faddeev equations and a variational calculation. In both methods we find that the system is bound by about 200 MeV and the width is smaller than 40 MeV, a situation opposite to the one of the $\bar K NN$ system and which makes this state well suited for experimental observation.
Search for the Decay of the Higgs Boson to Charm Quarks with the ATLAS Experiment
2018
A direct search for the standard model Higgs boson decaying to a pair of charm quarks is presented. Associated production of the Higgs and Z bosons, in the decay mode ZH→ℓ+ℓ−c¯c is studied. A data set with an integrated luminosity of 36.1 fb−1 of pp collisions at √s=13TeV recorded by the ATLAS experiment at the LHC is used. The H→c¯c signature is identified using charm-tagging algorithms. The observed (expected) upper limit on σ(pp→ZH)×B(H→c¯c) is 2.7 (3.9+2.1−1.1) pb at the 95% confidence level for a Higgs boson mass of 125 GeV, while the standard model value is 26 fb.