33 research outputs found
Low Mass Dimuon Production in p-A Collisions at 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/ 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 , , , and . A new
high-precision measurement of the electromagnetic transition form factors of
the and mesons is presented, complemented with a measurement of
the temperature parameter of the meson in cold nuclear matter. The \pt
spectra for the and mesons are extracted in the full \pt
range accessible, up to \pt = 2 GeV/. The nuclear dependence of the
production cross sections for the , and mesons has been
investigated in terms of the power law , and the parameter was studied as a function of
\pt
Measurement of the and Dalitz decays transition form factors in p-A collisions at 400 GeV/ with the NA60 apparatus
The NA60 experiment has studied low-mass muon pairs production in
proton-nucleus collisions at 400 GeV/ 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 , , , and . The large
collected statistics allows to isolate the contributions due to the Dalitz
decays of the and 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 meson
J/ 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
production in and collisions measured by PHENIX at RHIC
PHENIX preliminary results on the production in and
collisions at 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 spectra and the 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 ).
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