Low Mass Dimuon Production in p-A Collisions at s=27.5\sqrt{s} = 27.5 GeV with NA60

The NA60 experiment has studied low-mass muon pair production in proton-nucleus collisions with a system of Be, Cu, In, W, Pb and U targets using a 400 GeV/$c$ proton beam at the CERN SPS. The mass spectrum is well described by the superposition of the two-body and Dalitz decays of the light neutral mesons $\eta$, $\rho$, $\omega$, $\eta'$ and $\phi$. A new high-precision measurement of the electromagnetic transition form factors of the $\eta$ and $\omega$ mesons is presented, complemented with a measurement of the temperature parameter of the $\rho$ meson in cold nuclear matter. The \pt spectra for the $\omega$ and $\phi$ mesons are extracted in the full \pt range accessible, up to \pt = 2 GeV/$c$. The nuclear dependence of the production cross sections for the $\eta$, $\omega$ and $\phi$ mesons has been investigated in terms of the power law $\sigma_\mathrm{pA} \propto \mathrm{A}^\alpha$, and the $\alpha$ parameter was studied as a function of \pt

Measurement of the η\eta and ω\omega Dalitz decays transition form factors in p-A collisions at 400 GeV/cc with the NA60 apparatus

The NA60 experiment has studied low-mass muon pairs production in proton-nucleus collisions at 400 GeV/$c$ at the CERN SPS. The mass spectrum is well described by the superposition of the two-body and Dalitz decays of the light neutral mesons $\eta$, $\rho$, $\omega$, $\eta'$ and $\phi$. The large collected statistics allows to isolate the contributions due to the Dalitz decays of the $\eta$ and $\omega$ mesons, from which the electromagnetic transition form factors of the two mesons have been extracted. The found values agree with the previous available measurements, improving their uncertainty thanks to the higher statistics. The results thus confirm the discrepancy with the prediction of the Vector Meson Dominance model in the case of the electromagnetic form factor of the $\omega$ meson

J/ψ\psi production in In-In and p-A collisions

The NA60 experiment studies dimuon production in In-In and p-A collisions at the CERN SPS. We report recent results on \jpsi production, measured through its muon pair decay. As a function of centrality, we show that in In-In the \jpsi yield is suppressed beyond expectations from nuclear absorption. We present also for the first time results on \jpsi production in p-A collisions at 158 GeV, the same energy of the nucleus-nucleus data. For both p-A and In-In we show preliminary results on \psip suppression. Finally, we have studied the kinematical distributions of the \jpsi produced in In-In collisions. We present results on transverse momentum and rapidity, as well as on the angular distribution of the \jpsi decay products.Comment: 8 pages, Quark Matter 2006 conference proceeding

In-medium vector mesons and low mass lepton pairs from heavy ion collisions

The rho and omega meson self-energy at finite temperature and baryon density have been analysed for an exhaustive set of mesonic and baryonic loops in the real time formulation of thermal field theory. The large enhancement of spectral strength below the nominal rho mass is seen to cause a substantial enhancement in dilepton pair yield in this mass region. The integrated yield after space-time evolution using relativistic hydrodynamics with quark gluon plasma in the initial state leads to a very good agreement with the experimental data from In-In collisions obtained by the NA60 collaboration.Comment: Invited Talk at the DAE-BRNS Workshop on Hadron Physics, Bhabha Atomic Research Centre, Mumbai, India, October 31-November 4, 201

J/ΨJ/\Psi production in Cu+CuCu+Cu and Au+AuAu+Au collisions measured by PHENIX at RHIC

PHENIX preliminary results on the $J/\Psi$ production in $Cu+Cu$ and $Au+Au$ collisions at $\sqrt{s_{NN}}=200$ GeV are presented. They are compared to results from lower energy experiments NA50 and NA60 at CERN SPS and to expectations from various theoretical models.Comment: 4 pages, 7 figures, Proceedings for the SQM2006 Conference, submitted to "Journal of Physics G: Nuclear and Particle Physics

Baryonic Effect on chi_cJ Suppression in Au+Au Collisions at RHIC Energies

We predict that initially produced chi_cJ mesons at low transverse momentum in the central rapidity region are almost dissociated by nucleons and antinucleons in hadronic matter produced in central Au+Au collisions at RHIC energies sqrt {s_{NN}}= 130 and 200 GeV. In calculations the nucleon and antinucleon distributions in hadronic matter are results of evolution from their freeze-out distributions which well fit the experimental p_T spectra of proton and antiproton. Any measured chi_cJ mesons at low p_T are generated from deconfined matter and give an explicit proof of regeneration mechanism (recombination mechanism).Comment: 10 pages, 3 figures, Latex, a discussion added to the referenc

Strangeness Report

The paper provides a short report on strangeness production in ultrarelativistic nucleus-nucleus collision, with the main stress on strange particle abundances.Comment: Proceedings of Quark Matter 200

NA60 results on pTp_T spectra and the ρ\rho spectral function in In-In collisions

The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 AGeV In-In collisions. A strong excess of pairs is observed above the yield expected from neutral meson decays. The unprecedented sample size of close to 400K events and the good mass resolution of about 2% have made it possible to isolate the excess by subtraction of the decay sources (keeping the $\rho$). The shape of the resulting mass spectrum exhibits considerable broadening, but essentially no shift in mass. The acceptance-corrected transverse-momentum spectra have a shape atypical for radial flow and show a significant mass dependence, pointing to different sources in different mass regions.Comment: 4 pages, 4 figures, Quark Matter 2006 conference proceeding