Search results for "Quark"
showing 10 items of 2905 documents
Search for pair-produced heavy quarks decaying toWqin the two-lepton channel at(s)=7 TeVwith the ATLAS detector
2012
A search is presented for heavy-quark pair production (Q (Q) over bar) under the decay hypothesis Q (Q) over bar -> W(+)qW(-)(q) over bar with q = d, s, b for up-type Q or q = u, c for down-type ...
Heavy Quark Production in pp Collisions
1994
A systematic study of the inclusive single heavy quark and heavy-quark pair production cross sections in pp collisions is presented for RHIC and LHC energies. We compare with existing data when possible. The dependence of the rates on the renormalization and factorization scales is discussed. Predictions of the cross sections are given for two different sets of parton distribution functions.
Single bottom quark production in kT-factorisation
2015
Journal of High Energy Physics 2015.9 (2015): 123 reproduced by permission of Scuola Internazionale Superiore di Studi Avanzati (SISSA)
Heavy quark impact factor in kT-factorization
2013
We present the calculation of the finite part of the heavy quark impact factor at next-to-leading logarithmic accuracy in a form suitable for phenomenological studies such as the calculation of the cross-section for single bottom quark production at the LHC within the kT-factorization scheme.
Spectator Effects in the Heavy Quark Effective Theory
1996
We present a complete analysis of the Heavy Quark Effective Theory Lagrangian at order $1/m^2$ in the leading logarithmic approximation, including effects induced by spectator quarks. At this order new correction terms appear in the effective Lagrangian, as four-quark operators containing both heavy and light quark fields. We compute the coefficients of these operators to one-loop order and in the leading-logarithmic approximation. Two of them break the heavy quark spin symmetry and we estimate their contribution to the hyperfine splitting of the heavy mesons in the factorization approximation. We find that they make a positive contribution to the hyperfine splitting of about 10% of the mea…
Measurement of the W+b-jet and W+c-jet differential production cross sections in pp¯ collisions at s=1.96 TeV
2015
We present a measurement of the cross sections for the associated production of a $W$ boson with at least one heavy quark jet, $b$ or $c$, in proton-antiproton collisions. Data corresponding to an integrated luminosity of 8.7 fb$^{-1}$ recorded with the D0 detector at the Fermilab Tevatron \ppbar Collider at $\sqrt{s}=1.96$ TeV are used to measure the cross sections differentially as a function of the jet transverse momenta in the range 20 to 150 GeV. These results are compared to calculations of perturbative QCD theory as well as predictions from Monte Carlo generators.
Quark effects, meson-exchange currents and background in the d(e,e'p)delta reaction
1994
[EN] We have studied in detail the cross section for the d(e, e'p)Delta reaction leading to the emission of a fast nucleon and a Delta at rest, which has been advocated as a tool to investigate quark effects in nuclei. We find that ordinary meson-exchange currents mechanisms dominate the quark-exchange effects in the region of excitation of the Delta and could be competitive at higher energies. Furthermore, at these higher energies, the small cross sections for the quark signal, together with the presence of a background about one order of magnitude bigger than the quark signal, make in any case the extraction of information about quark-exchange currents effects extraordinarily difficult.
Four-quark spectroscopy within the hyperspherical formalism
2006
We present a generalization of the hyperspherical harmonic formalism to study systems made of quarks and antiquarks of the same flavor. This generalization is based on the symmetrization of the $N-$body wave function with respect to the symmetric group using the Barnea and Novoselsky algorithm. The formalism is applied to study four-quark systems by means of a constituent quark model successful in the description of the two- and three-quark systems. The results are compared to those obtained by means of variational approaches. Our analysis shows that four-quark systems with exotic $0^{+-}$ and non-exotic $2^{++}$ quantum numbers may be bound independently of the mass of the quark. $2^{+-}$ …
Generalized screened potential model
2014
A new non relativistic quark model to calculate the spectrum of heavy quark mesons is developed. The model is based on an interquark potential interaction that implicitly incorporates screening effects from meson-meson configurations. An analysis of the bottomonium spectrum shows the appearance of extra states as compared to conventional non screened potential models.
One-photon decay of the tetraquark stateX(3872)→γ+J/ψin a relativistic constituent quark model with infrared confinement
2011
We further explore the consequences of treating the $X(3872)$ meson as a tetraquark bound state by analyzing its one-photon decay $X\ensuremath{\rightarrow}\ensuremath{\gamma}+J/\ensuremath{\psi}$ in the framework of our approach developed in previous papers which incorporates quark confinement in an effective way. To introduce electromagnetism we gauge a nonlocal effective Lagrangian describing the interaction of the $X(3872)$ meson with its four constituent quarks by using the $P$-exponential path-independent formalism. We calculate the matrix element of the transition $X\ensuremath{\rightarrow}\ensuremath{\gamma}+J/\ensuremath{\psi}$ and prove its gauge invariance. We evaluate the $X\ens…