Search results for "Nucleon"
showing 10 items of 1041 documents
Strangeness and charm in nuclear matter
2012
The properties of strange (K, (K) over bar and (K) over bar*) and open-charm (D, (D) over bar and D*) mesons in dense matter are studied using a unitary approach in coupled channels for meson-baryon scattering. In the strangeness sector, the interaction with nucleons always comes through vector-meson exchange, which is evaluated by chiral and hidden gauge Lagrangians. For the interaction of charmed mesons with nucleons we extend the SU(3) Weinberg-Tomozawa Lagrangian to incorporate spin-flavor symmetry and implement a suitable flavor symmetry breaking. The in-medium solution for the scattering amplitude accounts for Pauli blocking effects and meson self-energies. On one hand, we obtain the …
Charged kaon production by coherent scattering of neutrinos and antineutrinos on nuclei
2013
With the aim of achieving a better and more complete understanding of neutrino interactions with nuclear targets, the coherent production of charged kaons induced by neutrinos and antineutrinos is investigated in the energy range of some of the current neutrino experiments. We follow a microscopic approach which, at the nucleon level, incorporates the most important mechanisms allowed by the chiral-symmetry-breaking pattern of QCD. The distortion of the outgoing K ((K) over bar) is taken into account by solving the Klein-Gordon equation with realistic optical potentials. Angular and momentum distributions, as well as the energy and nuclear dependence of the total cross section, are studied.
Single pion production in neutrino-nucleus scattering
2013
We study 1 pi production in both charged and neutral current neutrino-nucleus scattering for neutrino energies below 2 GeV. We use a theoretical model for one pion production at the nucleon level that we correct for medium effects. The results are incorporated into a cascade program that apart from production also includes the pion final state interaction inside the nucleus. Besides, in some specific channels coherent pi production is also possible and we evaluate its contribution as well. Our results for total and differential cross sections are compared with recent data from the MiniBooNE Collaboration. The model provides an overall acceptable description of the data, better for neutral-c…
Rate Equation Network for Baryon Production in High Energy Nuclear Collisions
2003
We develop and solve a network of rate equations for the production of baryons and anti-baryons in high energy nuclear collisions. We include all members of the baryon octet and decuplet and allow for transformations among them. This network is solved during a relativistic 2+1 hydrodynamical expansion of the of the hot matter created in the collision. As an application we compare to the number of protons, lambdas, negative cascades, and omega baryons measured at mid-rapidity in central collisions of gold nuclei at 65 GeV per nucleon at the Relativistic Heavy Ion Collider (RHIC).
Eta and Etaprime Photoproduction on the Nucleon with the Isobar Model EtaMAID2018
2019
The isobar model EtaMAID has been updated with new and high precision data for eta and etaprime photoproduction on protons and neutrons from MAMI, ELSA, GRAAL and CLAS. The background is described in a recently developed Regge-cut model, and for the resonance part the whole list of nucleon resonances has been investigated with 21 N* states contributing to eta photoproduction and 12 N* states contributing to etaprime photoproduction. A new approach is discussed to avoid double counting in the overlap region of Regge and resonances. A comparison is done among four newly updated partial waves analyses for observables and partial waves. Finally, the possibility of a narrow resonance near W=1900…
Photon emission in neutral-current interactions at intermediate energies
2013
Neutral current photon emission reactions with nucleons and nuclei are studied. These processes are important backgrounds for nu_mu to nu_e (bar(nu)_mu to bar(nu)_e) appearance oscillation experiments where electromagnetic showers instigated by electrons (positrons) and photons are not distinguishable. At intermediate energies, these reactions are dominated by the weak excitation of the Delta(1232) resonance and its subsequent decay into Ngamma There are also non-resonant contributions that, close to threshold, are fully determined by the effective chiral Lagrangian of strong interactions. In addition, we have also included mechanisms mediated by nucleon excitations (N*) from the second res…
Quark-model based study of the triton binding energy
2001
The three-nucleon bound state problem is studied employing a nucleon-nucleon potential obtained from a basic quark-quark interaction in a five-channel Faddeev calculation. The obtained triton binding energy is comparable to those predicted by conventional models of the $NN$ force.
Can One Distinguish Tau Neutrinos from Antineutrinos in Neutral-Current Pion Production Processes?
2007
A potential way to distinguish tau-neutrinos from antineutrinos, below the tau-production threshold, but above the pion production one, is presented. It is based on the different behavior of the neutral current pion production off the nucleon, depending on whether it is induced by neutrinos or antineutrinos. This procedure for distinguishing tau-neutrinos from antineutrinos neither relies on any nuclear model, nor it is affected by any nuclear effect (distortion of the outgoing nucleon waves, etc...). We show that neutrino-antineutrino asymmetries occur both in the totally integrated cross sections and in the pion azimuthal differential distributions. To define the asymmetries for the latte…
Longitudinal double spin asymmetries in single hadron quasi-real photoproduction at high $p_T$
2015
We measured the longitudinal double spin asymmetries $A_{LL}$ for single hadron muo-production off protons and deuterons at photon virtuality $Q^2$ < 1(GeV/$\it c$)$^2$ for transverse hadron momenta $p_T$ in the range 0.7 GeV/$\it c$ to 4 GeV/$\it c$ . They were determined using COMPASS data taken with a polarised muon beam of 160 GeV/$\it c$ or 200 GeV/$\it c$ impinging on polarised $\mathrm{{}^6LiD}$ or $\mathrm{NH_3}$ targets. The experimental asymmetries are compared to next-to-leading order pQCD calculations, and are sensitive to the gluon polarisation $\Delta G$ inside the nucleon in the range of the nucleon momentum fraction carried by gluons $0.05 < x_g < 0.2$. We measured the longi…
Nuclear-mass dependence of azimuthal beam-helicity and beam-charge asymmetries in deeply virtual Compton scattering
2009
The nuclear-mass dependence of azimuthal cross section asymmetries with respect to charge and longitudinal polarization of the lepton beam is studiedfor hard exclusive electroproduction of real photons. The observed beam-charge and beam-helicity asymmetries are attributed to the interference between the Bethe-Heitler and deeply virtual Compton scattering processes. For various nuclei, the asymmetries are extracted for both coherent and incoherent-enriched regions, which involve different (combinations of) generalized parton distributions. For both regions, the asymmetries are compared to those for a free proton, and no nuclear-mass dependence is found.