共查询到20条相似文献,搜索用时 10 毫秒
1.
B. K. Srivastava 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):862-867
The study of correlations and fluctuations can provide evidence for the production of the quark-gluon plasma (QGP) in relativistic
heavy-ion collisions. Various theories predict that the production of a QGP phase in relativistic heavy-ion collisions could
produce significant event-by-event correlations and fluctuations in transverse momentum, multiplicity, etc. Some of the recent
results using STAR at RHIC will be presented along with results from other experiments at RHIC. The focus is on forward-backward
multiplicity correlations, balance function, charge and transverse-momentum fluctuations, and correlations. 相似文献
2.
K. Wosińska J. Pluta F. Hanappe L. Stuttge J. C. Angelique B. Benoit E. de Goes Brennand G. Bizard J. Colin G. Costa P. Desesquelles O. Dorvaux D. Durand B. Erazmus S. Kuleshov R. Lednicky M. Marques Th. Materna K. Mikhailov G. Papatheofanous T. Pawlak A. Staranowicz A. Stavinskiy B. Tamain A. Vlasov L. Vorobyev 《The European Physical Journal A - Hadrons and Nuclei》2007,32(1):55-59
The measurement of the two-particle correlation function for different particle species allows to obtain information about
the development of the particle emission process: the space-time properties of emitting sources and the emission time sequence
of different particles. The single-particle characteristics and two-particle correlation functions for neutral and charged
particles registered in forward direction are used to determine that the heavy fragments (deuterons and tritons) are emitted
in the first stage of the reaction (pre-equilibrium source) while the majority of neutrons and protons originates from the
long-lived quasi-projectile. The emission time sequence of protons, neutrons and deuterons has been obtained from the analysis
of non-identical particle correlation functions. 相似文献
3.
M.A. Ivanov P. Santorelli N. Tancredi 《The European Physical Journal A - Hadrons and Nuclei》2000,9(1):109-114
The form factors of the weak currents, which appear in the semileptonic decays of the heavy pseudoscalar mesons are calculated
within the quark confinement model by taking into account, for the first time, the structure of heavy-meson vertex and the
finite quark mass contribution in the heavy-quark propagators. The results are in quite good agreement with the experimental
data.
Received: 9 June 2000 / Accepted: 15 August 2000 相似文献
4.
《The European Physical Journal A - Hadrons and Nuclei》2009,40(1):45-59
We present the results of a study of charged-pion production in 12C + 12C collisions at incident beam energies of 1A GeV and 2A GeV using the HADES spectrometer at GSI. The main emphasis of the
HADES program is on the dielectron signal from the early phase of the collision. Here, however, we discuss the data with respect
to the emission of charged hadrons, specifically the production of mesons, which are related to neutral pions representing a dominant contribution to the dielectron yield. We have performed
the first large-angular-range measurement of the distribution of mesons for the 12C + 12C collision system covering a fairly large rapidity interval. The pion yields, transverse-mass and angular distributions are
compared with calculations done within a transport model, as well as with existing data from other experiments. The anisotropy
of pion production is systematically analyzed. 相似文献
5.
Xin Dong 《The European Physical Journal C - Particles and Fields》2009,61(4):659-664
I report the most recent measurements on open heavy flavor production at RHIC on behalf of the STAR collaboration. The total
charm production cross section in midrapidity at RHIC energy is found to approximately scale by number of binary collisions
in d + Au, Cu + Cu and Au + Au collisions. The nuclear modification factor of non-photonic electrons is strongly suppressed in
central Au + Au collisions, suggesting substantial heavy quark energy loss at RHIC. The bottom decay contribution to non-photonic
electrons was studied via the e–h and e–D
0 azimuthal angular correlations. The bottom contribution is found to be important at p
T
>5 GeV/c, and is consistent with the FONLL calculation within uncertainties. Charm production through gluon jet splitting was measured
by studying the D
*± contents in the fully reconstructed jets in p+p collisions. This rate is consistent with pQCD evaluation of gluon splitting into a pair of charm quarks and subsequent hadronization. 相似文献
6.
A.B. Larionov W. Cassing M. Effenberger U. Mosel 《The European Physical Journal A - Hadrons and Nuclei》2000,7(4):507-518
The proton–charged pion correlated emission is studied in the reactions Au (1.06 AGeV) + Au, Ni (1.06 and 1.93 AGeV) + Ni
and Ni (1.97 AGeV) + Cu within the BUU approach. The associated invariant mass distributions are shifted to smaller energies
with respect to the free Δ(1232) mass distribution due to kinematical reasons. We find that the existing and partly conflicting
experimental data do not allow to draw definite conclusions on the in-medium modification of the Δ(1232).
Received: 18 October 1999 / Revised version: 4 February 2000 相似文献
7.
A. G. Knospe 《The European Physical Journal C - Particles and Fields》2009,62(1):223-227
Heavy-flavor semileptonic decays are expected to dominate the spectrum of non-photonic electrons produced from collisions
at the energies of the Relativistic Heavy Ion Collider. The non-photonic electron yield is suppressed by approximately a factor
of 5 in central Au + Au events at
GeV relative to p+p events with the same collision energy. Most theoretical models predict less non-photonic-electron suppression than is observed
experimentally. We present a preliminary measurement of the yield of non-photonic electrons in Cu + Cu events at
GeV, as well as the nuclear modification factor. 相似文献
8.
The kinetic freeze-out process of a pion gas through a finite layer with time-like normal is considered. The pion gas is described
by a Boltzmann gas with elastic collisions among the pions. Within this model, the impact of the in-medium pion mass modification
on the freeze-out process is studied. A marginal change of the freeze-out variables temperature and flow velocity and an insignificant
modification of the frozen-out particle distribution function has been found. 相似文献
9.
10.
Bin Zhang 《The European Physical Journal C - Particles and Fields》2009,62(1):25-29
The parton-cascade model is a microscopic transport approach in the study of the space-time evolution of the quark–gluon plasma
produced in relativistic heavy-ion collisions and its experimental manifestations. In the following, parton-cascade calculations
on elliptic flow and thermalization will be discussed. Dynamical evolution is shown to be important for the production of
elliptic flow including the scaling and the breaking of the scaling of elliptic flow. The degree of thermalization is estimated
using both an elastic parton-cascade and a radiative transport model. A longitudinal to transverse pressure ratio of P
L
/P
T
≈0.8 is shown to be expected in the central cell in central collisions. This provides information on viscous corrections to
the ideal hydrodynamical approach. 相似文献
11.
《The European Physical Journal A - Hadrons and Nuclei》2008,38(2):163-166
The HADES spectrometer at GSI (Darmstadt) is investigating the e
+
e
- pair production in p+p, p+A and A+A collisions. In this contribution we would like to highlight the physics motivations and the experiments performed so far,
focusing mainly on the first results coming from 12C + 12C collisions at 1 and 2AGeV, and on preliminary results from p+p/d+p collisions at 1.25AGeV.
Original article based on material presented at HADRON 2007. 相似文献
12.
E. Hernández J. Nieves J. M. Verde-Velasco 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):714-717
We evaluate semileptonic and two-meson nonleptonic decays of the B
c
- meson in the framework of a nonrelativistic quark model. The former are done in spectator approximation using one-body current
operators at the quark level. Our model reproduces the constraints of heavy-quark spin symmetry obtained in the limit of infinite
heavy-quark mass. For the two-meson nonleptonic decays we work in factorization approximation. We compare our results to the
ones obtained in different relativistic approaches. 相似文献
13.
K. Tackmann 《The European Physical Journal A - Hadrons and Nuclei》2008,38(2):137-140
Knowing the mass of the b -quark is essential to the study of the structure and decays of B -mesons as well as to future tests of the Higgs mechanism of mass generation. We present recent preliminary measurements
of the b -quark mass and related nonperturbative parameters from moments of kinematic distributions in charmed and charmless semileptonic
B -meson decays. Their determination from charmless semileptonic B -meson decays is the first measurement in this mode. The data were collected by the BABAR detector at the PEP-II asymmetric-energy
e
+
e
- -collider at the Stanford Linear Accelerator Center at a center-of-mass energy of 10.58GeV.
Original article based on material presented at HADRON 2007. 相似文献
14.
M. Csanád T. Csörgő A. Ster B. Lörstad N. N. Ajitanand J. M. Alexander P. Chung W. G. Holzmann M. Issah R. A. Lacey 《The European Physical Journal A - Hadrons and Nuclei》2008,38(3):363-368
Recent PHOBOS measurements of the excitation function for the pseudo-rapidity dependence of the elliptic flow in Au + Au collisions
at RHIC have posed a significant theoretical challenge. Here we show that these differential measurements, as well as the
RHIC measurements on transverse momentum satisfy a universal scaling relation predicted by the Buda-Lund model, based on exact
solutions of perfect fluid hydrodynamics. We also show that the recently found transverse kinetic energy scaling of the elliptic
flow is a special case of this universal scaling. 相似文献
15.
Zhangbu Xu Thomas Ullrich 《The European Physical Journal C - Particles and Fields》2009,61(4):687-691
We report results on quarkonium production from the STAR experiment at the Relativistic Heavy-Ion Collider (RHIC). J/ψ spectra in p+p and Cu+Cu collisions at
GeV with transverse momenta in the range of 0.5–14 GeV/c and 5–8 GeV/c, respectively, are presented. We find that for p
T
>5 GeV/c yields in p+p collisions are consistent with those in minimum-bias Cu+Cu collisions scaled with the respective number of binary nucleon-nucleon
collisions. In this range the nuclear modification factor, R
AA
, is measured to be 0.9±0.2 (stat). For the first time at RHIC, high-p
T
J/ψ-hadron correlations were studied in p+p collisions. Implications from our measurements on J/ψ production mechanisms, constraints on open bottom yields, and J/ψ dissociation mechanisms at high-p
T
are discussed. In addition, we give a brief status of measurements of ϒ production in p+p and Au+Au collisions and present projections of future quarkonia measurements based on an upgrades to the STAR detector and
increased luminosity achieved through stochastic cooling of RHIC. 相似文献
16.
We review from the point of view of nonextensive statistics the ubiquitous presence in elementary and heavy-ion collisions
of power law distributions. Special emphasis is placed on the conjecture that this is just a reflection of some intrinsic
fluctuations existing in the hadronic systems considered. These systems are summarily described by a single parameter q playing the role of a nonextensivity measure in the nonextensive statistical models based on Tsallis entropy.
This paper is part of the Topical Issue Statistical Power Law Tails in High-Energy Phenomena. 相似文献
17.
M. K. Kirejczyk 《The European Physical Journal A - Hadrons and Nuclei》2009,41(2):141-143
The -variable, a measure of statistical correlation of particle momenta, introduced by Mrówczyński and Gaździcki, has been calculated
for the events simulated with a simple thermal toy model. It is shown that mixing two thermal sources of unequal temperature
can result in negative values of . 相似文献
18.
R. Vogt 《The European Physical Journal C - Particles and Fields》2009,61(4):793-798
We assess the theoretical uncertainties on the total heavy-quark cross section. We discuss the importance of the quark mass,
the choice of the scale, the number of light flavors and the parton densities on the estimate of the uncertainty. At first
glance, the uncertainty bands on the total charm cross sections obtained by integrating the FONLL inclusive cross section
and by integrating the partonic total cross sections appear to be incompatible. We explain how this apparent difference arises
and describe how the two results can be reconciled. The small mass of the charm quark amplifies the effect of varying the
other parameters in the calculation, making the uncertainty on the total charm cross section difficult to quantify. On the
other hand, the bottom-quark total cross section is under much better theoretical control, and differences between the two
approaches are small. 相似文献
19.
A. Mishra A. Kumar S. Sanyal S. Schramm 《The European Physical Journal A - Hadrons and Nuclei》2009,41(2):205-213
The medium modifications of the energies of kaons and antikaons in isospin asymmetric hyperonic matter are investigated using
a chiral SU(3) model. The isospin-dependent medium effects are important for asymmetric heavy-ion collision experiments, as well as relevant
for the neutron star phenomenology as the bulk matter in the interior of the neutron star is highly isospin asymmetric. The
effects of hyperons on the medium modifications of the kaons and antikaons in the strange hadronic matter are investigated
in the present work and are seen to be appreciable for hadronic matter with large strangeness fractions. The study of the
K -mesons in the asymmetric strange hadronic matter can be especially relevant for the compressed strange baryonic matter which
can result from asymmetric heavy-ion collision experiments in the future accelerator facility FAIR at GSI. 相似文献
20.
M. van Leeuwen 《The European Physical Journal C - Particles and Fields》2009,61(4):569-574
We present selected recent results of multi-hadron correlation measurements in azimuth and pseudorapidity at intermediate
and high p
T
in Au+Au collisions at
, from the STAR experiment at RHIC. At intermediate p
T
, measurements are presented that attempt to determine the origin of the associated near-side (small Δφ) yield at large pseudo-rapidity difference Δη that is found to be present in heavy ion collisions. In addition, results are reported on new multi-hadron correlation measures
at high-p
T
that use di-hadron triggers and multi-hadron cluster triggers with the goal to constrain the underlying jet kinematics better
than in the existing measurements of inclusive spectra and di-hadron correlations. 相似文献