نتایج جستجو برای: quark scattering
تعداد نتایج: 142144 فیلتر نتایج به سال:
We study the low energy part of the nucleon and ∆ spectra by solving the Schrödinger equation for the three-quark system in the hyperspherical harmonic approach. The quark-quark hamiltonian considered includes, besides the usual one-gluon exchange, pion and sigma exchanges generated by the chiral symmetry breaking. This quark-quark potential reproduces, in a Resonating Group Method calculation,...
Charm production from the quark-gluon plasma created in the midrapidity of central heavy ion collisions at the Large Hadron Collider (LHC) is studied in the next-to-leading order in QCD. Using a schematic longitudinally boost-invariant and transversally expanding fire-cylinder model, we find that charm production could be appreciably enhanced at LHC as a result of the high temperature that is e...
The CP violating Dashen phase in QCD is predicted by chiral perturbation theory to occur when the up-down quark mass difference becomes sufficiently large at fixed down-quark mass. Before reaching this phase, all physical hadronic masses and scattering amplitudes are expected to behave smoothly with the up-quark mass, even as this mass passes through zero. In Euclidean space, the topological su...
The chiral SU(3) quark model is extended to include coupling between vector chiral field and quarks. By using this model, the phase shifts of NN scattering for different partial waves are studied. The results are very similar to those of the chiral SU(3) quark model calculation, in which one gluon exchange (OGE) plays dominate role in the short range part of the quark-quark interactions. Only i...
The single-flavour quark condensate 〈0 |qq| 0〉 is a fundamental parameter of χPT , determining the relative size of mass and momentum terms in the expansion. Since it can not be predicted theoretically, its value must be determined experimentally, e.g. by measuring the ππ scattering lengths, whose values are predicted very precisely within the framework of χPT , assuming a big quark condensate ...
We have completed the next-to-leading order perturbative QCD corrections to the virtual-photon exclusive differential cross sections for heavy quark production in deep-inelastic electron-proton scattering, i.e. e + P → Q +Q +X . Using these results, we have computed distributions which are sensitive to correlations among the heavy quark, the heavy antiquark, and the associated jet. Some predict...
It is shown that the euclidean origin of the instanton leads to the appearence of a large imaginary part in some diagrams for hadron production in quark-quark scattering. This phenomenon and instanton–induced quark spin-flip give the fundamental QCD mechanism for the observed large single-spin asymmetries in hadron-hadron and lepton-hadron interactions. 1 Talk presented at the Workshop ”Polariz...
A large data set of charged-pion (pi+/-) electroproduction from both hydrogen and deuterium targets has been obtained spanning the low-energy residual-mass region. These data conclusively show the onset of the quark-hadron duality phenomenon, as predicted for high-energy hadron electroproduction. We construct several ratios from these data to exhibit the relation of this phenomenon to the high-...
We present the two-loop helicity amplitudes for the scattering of massless quarks in QCD. We use projector techniques to compute the coefficients of the general four-quark amplitude at up to two-loops in conventional dimensional regularisation and use these coefficients to derive the helicity amplitudes in the ’t Hooft-Veltman scheme. The structure of the infrared divergences agrees with that p...
We consider heavy quark and antiquark off-shell spinorial currents with emission of an arbitrary number of gluons of positive helicity. From this results we calculate the corresponding on-shell scattering amplitude and the quark-antiquark vector current. Then, we show that in the heavy top quark effective theory the holomorfic component of the Higgs → qq̄ + n-gluon amplitude vanish for helicity ...
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