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تسجيل مستخدم جديدInteraction of vector mesons with baryons and vectors in the nuclear medium
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In this talk we present a short review of recent developments concerning the interaction of vector mesons with baryons and with nuclei. We begin with the hidden gauge formalism for the interaction of vector mesons, then review results for vector baryon interaction and in particular the resonances which appear as composite states, dynamically generated from the interaction of vector mesons with baryons. New developments concerning the mixing of these states with pseudoscalars and baryons are also reported. We include some discussion on the $5/2^+$ $Delta$ resonances around 2000 MeV, where we suggest that the $Delta(2000)5/2^+$ resonance, which comes in the PDG from averaging a set of resonances appearing around 1700 MeV and another one around 2200 MeV, corresponds indeed to two distinct resonances. We also report on a hidden charm baryon state around 4400 MeV coming from the interaction of vector mesons and baryons with charm, and how this state has some repercussion in the $J/psi$ suppression in nuclei. The interaction of $K^*$ in nuclei is also reported and suggestions are made to measure by means of the transparency ratio the huge width in the medium that the theoretical calculations predict. The formalism is extended to $J/psi$ interaction with nuclei and the transparency ratio for $J/psi$ photoproduction in nuclei is studied and shown to be a good tool to find possible baryon states which couple to $J/psi N$.
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After some short introductory remarks on particular issues on the vector mesons in nuclei, in this paper we present a short review of recent developments concerning the interaction of vector mesons with baryons and with nuclei from a modern perspecti
ve using the local hidden gauge formalism for the interaction of vector mesons. We present results for the vector baryon interaction and in particular for the resonances which appear as composite states, dynamically generated from the interaction of vector mesons with baryons, taking also the mixing of these states with pseudoscalars and baryons into account. We then venture into the charm sector, reporting on hidden charm baryon states around 4400 MeV, generated from the interaction of vector mesons and baryons with charm, which have a strong repercussion on the properties of the $J/Psi N$ interaction. We also address the interaction of $K^*$ with nuclei and make suggestions to measure the predicted huge width in the medium by means of the transparency ratio. The formalism is extended to study the phenomenon of $J/psi$ suppression in nuclei via $J/psi$ photoproduction reactions.
The light vector mesons ($rho$, $omega$, and $phi$) were produced in deuterium, carbon, titanium, and iron targets in a search for possible in-medium modifications to the properties of the $rho$ meson at normal nuclear densities and zero temperature.
The vector mesons were detected with the CEBAF Large Acceptance Spectrometer (CLAS) via their decays to $e^{+}e^{-}$. The rare leptonic decay was chosen to reduce final-state interactions. A combinatorial background was subtracted from the invariant mass spectra using a well-established event-mixing technique. The $rho$ meson mass spectrum was extracted after the $omega$ and $phi$ signals were removed in a nearly model-independent way. Comparisons were made between the $rho$ mass spectra from the heavy targets ($A > 2$) with the mass spectrum extracted from the deuterium target. With respect to the $rho$-meson mass, we obtain a small shift compatible with zero. Also, we measure widths consistent with standard nuclear many-body effects such as collisional broadening and Fermi motion.
We present dilepton spectra from p+p and p+Nb collisions at a kinetic beam energy of 3.5 GeV, which were simulated with the GiBUU transport model assuming different in-medium scenarios. We compare these spectra to preliminary HADES data and show that
GiBUU can describe the data reasonably well. Our simulations indicate that the intermediate dilepton-mass region is sensitive to the N-Delta electromagnetic transition form factor, which up to now is unmeasured in the time-like region.
We review the recent results of heavy meson diffusion in thermal hadronic matter. The interactions of D and B-bar mesons with other hadrons (light mesons and baryons) are extracted from effective field theories based on chiral and heavy-quark symmetr
ies. When these guiding principles are combined with exact unitarity, physical values of the cross sections are obtained. These cross sections (which contain resonant contributions) are used to calculate the drag and diffusion coefficients of heavy mesons immersed in a thermal and dense medium. The transport coefficients are computed using a Fokker-Planck reduction of the Boltzmann equation.
The suppression of the nuclear modification factor for heavy flavor hadrons is usually attributed to the energy loss of heavy quarks propagating in a QCD plasma. Nevertheless it is puzzling that the suppression is as strong as for light flavors. We s
how that when accounting for the quark momentum shift associated to the opening of the recombination/coalescence channel for hadron production in the plasma, it is not necessary to invoke such strong energy loss. This shift is expressed in terms of an increase of the heavy baryon to meson ratio in nuclear with respect to proton collisions. When this mechanism is included along with a moderate energy loss, data from RHIC and LHC for the nuclear modification factor of electrons coming from heavy flavor decays as well as of charm mesons, can be reasonably described.
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