25 research outputs found
Ultrarelativistic nucleus-nucleus collisions and the quark-gluon plasma
We present an overview of selected aspects of ultrarelativistic
nucleus-nucleus collisions, a research program devoted to the study of strongly
interacting matter at high energy densities and in particular to the
characterization of the quark-gluon plasma (QGP). The basic features of the
phase diagram of nuclear matter, as currently understood theoretically, are
discussed. The experimental program, carried out over a broad energy domain at
various accelerators, is briefly reviewed, with an emphasis on the global
characterization of nucleus-nucleus collisions. Two particular aspects are
treated in more detail: i) the application of statistical models to a
phenomenological description of particle production and the information it
provides on the phase diagram; ii) the production of hadrons carrying charm
quarks as messengers from the QGP phase.Comment: Based on lectures given by P.Braun-Munzinger at the VIII Hispalensis
International Summer School, Oromana (Seville, Spain), June 9-21, 2003 32
pages, 20 figures. A clickable list of references available at
http://www-linux.gsi.de/~andronic/qgp/qgp.htm
Energy Loss Effect in High Energy Nuclear Drell-Yan Process
The energy loss effect in nuclear matter, which is another nuclear effect
apart from the nuclear effect on the parton distribution as in deep inelastic
scattering process, can be measured best by the nuclear dependence of the high
energy nuclear Drell-Yan process. By means of the nuclear parton distribution
studied only with lepton deep inelastic scattering experimental data, measured
Drell-Yan production cross sections for 800GeV proton incident on a variety of
nuclear targets are analyzed within Glauber framework which takes into account
energy loss of the beam proton. It is shown that the theoretical results with
considering the energy loss effect are in good agreement with the FNAL E866
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Au+Au reactions at the AGS: Experiments E866 and E917
Particle production and correlation functions from Au+Au reactions have been measured as a function of both beam energy (2--10.7 AGeV) and impact parameter. These results are used to probe the dynamics of heavy-ion reactions, confront hadronic models over a wide range of conditions and to search for the onset of new phenomena
Exploring the Partonic Structure of Hadrons through the Drell-Yan Process
The Drell-Yan process is a standard tool for probing the partonic structure
of hadrons. Since the process proceeds through a quark-antiquark annihilation,
Drell-Yan scattering possesses a unique ability to selectively probe sea
distributions. This review examines the application of Drell-Yan scattering to
elucidating the flavor asymmetry of the nucleon's sea and nuclear modifications
to the sea quark distributions in unpolarized scattering. Polarized beams and
targets add an exciting new dimension to Drell-Yan scattering. In particular,
the two initial-state hadrons give Drell-Yan sensitivity to chirally-odd
transversity distributions.Comment: 23 pages, 9 figures, to appear in J. Phys. G, resubmission corrects
typographical error
Effective role of unpolarized nonvalence partons in Drell-Yan single spin asymmetries
We perform numerical simulations of the Sivers effect from single spin
asymmetries in Drell-Yan processes on transversely polarized protons. We
consider colliding antiprotons and pions at different kinematic conditions of
interest for the future planned experiments. We conventionally name "framework
I" the results obtained when properly accounting for the various flavor
dependent polarized valence contributions in the numerator of the asymmetry,
and for the unpolarized nonvalence contribution in its denominator. We name
"framework II" the results obtained when taking a suitable flavor average of
the valence contributions and neglecting the nonvalence ones. We compare the
two methods, also with respect to the input parametrization of the Sivers
function which is extracted from data with approximations sometimes
intermediate between frameworks I and II. Deviations between the two approaches
are found to be small except for dilepton masses below 3 GeV. The Sivers effect
is used as a test case; the arguments can be generalized to other interesting
azimuthal asymmetries in Drell-Yan processes, such as the Boer-Mulders effect.Comment: 13 pages, 9 figures in eps forma
Re-evaluation of the LHC potential for the measurement of Mw
We present a study of the LHC sensitivity to the W boson mass based on
simulation studies. We find that both experimental and phenomenological sources
of systematic uncertainties can be strongly constrained with Z measurements:
the lineshape is robustly predicted, and its analysis provides an accurate
measurement of the detector resolution and absolute scale, while the
differential cross-section analysis absorbs most of the strong interaction
uncertainties. A sensitivity \delta Mw \sim 7 \MeV for each decay channel (W
--> e nu, W --> mu nu), and for an integrated luminosity of 10 fb-1, appears as
a reasonable goal
Centrality and dE_{T}/d\etadN_{ch}/d\eta$ in Heavy Ion Collisions at Mid-Rapidity
The PHENIX experiment at RHIC has measured transverse energy and charged
particle multiplicity at mid-rapidity in Au + Au collisions at
= 19.6, 130, 62.4 and 200 GeV as a function of centrality. The presented
results are compared to measurements from other RHIC experiments, and
experiments at lower energies. The dependence of
and per pair of participants is consistent with logarithmic
scaling for the most central events. The centrality dependence of
and is similar at all measured incident
energies. At RHIC energies the ratio of transverse energy per charged particle
was found independent of centrality and growing slowly with . A
survey of comparisons between the data and available theoretical models is also
presented.Comment: Proccedings of the Workshop: Focus on Multiplcity at Bari, Italy,
June 17-19,2004. To be submitted to the Jornal of Physics, "Conference
series". Includes: 20 Pages, 15 figures, 3 Tables, 80 Referencie