共查询到20条相似文献,搜索用时 46 毫秒
1.
Haibin Zhang 《The European Physical Journal C - Particles and Fields》2007,49(1):355-358
We report on the measurements of D0 meson production via direct reconstruction through the hadronic decay channel D0→Kπ in minimum bias d+Au and Au+Au collisions at with pT up to ∼3 GeV/c. We derive the charm production total cross-section per nucleon–nucleon collision from a combination of three
measurements: the D0 meson spectra, the non-photonic electron spectra from charm semi-leptonic decays obtained in p+p, d+Au, and Au+Au collisions,
and the charm-decayed single muon (prompt muon) spectra at low pT in Au+Au collisions. The cross-section is found to follow binary scaling, which is a signature of charm production exclusively
at the initial impact. The implications of charm quark energy-loss and thermalization in the strongly interacting matter are
discussed.
PACS 25.75.Dw; 13.20.Fc; 13.25.Ft; 24.85.+p 相似文献
2.
O. Drapier 《The European Physical Journal C - Particles and Fields》2005,43(1-4):201-208
The PHENIX experiment at RHIC measured single electron spectra in p + p, d + Au and Au + Au collisions at
GeV, and in Au + Au collisions at
GeV. In these spectra, electrons from semi-leptonic decays of charmed particles are the dominant contribution after subtraction
of all 'photonic' sources (photon conversions, Dalitz decays, decays of light vector mesons). The p + p open charm production
cross-section is found to be in good agreement with pQCD NLO calculations. The shape of the distributions obtained for p +
p interactions is compared with those observed for nucleus-nucleus collisions. From p + p to d + Au and Au + Au interactions,
open charm production is found to scale with the number of binary collisions
. Au + Au data at
GeV is compatible with the ISR p + p results scaled by
. The elliptic flow parameter v2 of heavy flavor electrons has also been measured, and is found to be non-zero in the intermediate pT range.
Arrival of the final proofs: 29 June 2005
PACS:
.
* Deceased
Spokesperson 相似文献
3.
J. Bielcik 《The European Physical Journal C - Particles and Fields》2007,49(1):375-378
The strong suppression of high pT hadrons observed at RHIC has led to the interpretation that energetic partons lose their energy via induced gluon radiation
in the hot and dense matter before fragmenting into hadrons. The study of heavy quark production can extend our understanding
of this scenario. Due to the dead cone effect, the suppression of heavy quark mesons at high pT is expected to be smaller than that observed for charged hadrons at the same energy. The measurement of non-photonic single
electrons up to high pT provides information on charm and beauty production. The semi-leptonic decays of D and B mesons are the dominant contribution
to the non-photonic electron spectra. The preliminary spectra from p+p, d+Au and Au+Au collisions at =200 GeV have been extracted for mid-rapidity non-photonic electrons in the range 1.5<pT (GeV/c)<10. The corresponding nuclear modification factors (RAA) are presented and show a large suppression in central Au+Au collisions, indicating an unexpectedly large energy loss for
heavy quarks in the hot and dense matter created at RHIC. This observed suppression is compared to recent theoretical models.
PACS 13.85.Qk; 13.20.Fc; 13.20.He; 25.75.Dw 相似文献
4.
Thomas S. Ullrich 《Acta Physica Hungarica A》2004,21(2-4):143-150
Inclusive spectra of charged particles at midrapidity in Au+Au collisions at $\sqrt {s_{NN} } = 130$ GeV and 200 GeV were measured with the STAR detector at RHIC. The measured mean transverse momentum 〈p T 〉 shows a characteristic dependence on charged particle multiplicity and beam energy in Au+Au collisions that is distinctly different from pp, $p\bar p$ and e+e? collisions. A 32%±3%(syst) increase in 〈p T 〉 from pp to Au+Au collisions was observed at 200 GeV. While the charged multiplicity was found to increase by 19%±5%(syst) from $\sqrt {s_{NN} } = 130$ GeV to 200 GeV, no significant difference in 〈p T 〉 was found between the two energies. A comparison with model predictions is discussed. 相似文献
5.
Takao Sakaguchi 《Acta Physica Hungarica A》2006,25(2-4):409-417
Results on direct photon measurements from the PHENIX experiment at RHIC are presented. The direct photon yields for P T >6GeV/c as a function of centrality in Au+Au collisions at $\sqrt {s_{NN} } = 200$ GeV are found to be consistent with NLO pQCD calculation scaled by the number of binary collisions. The results suggest that the photons observed are emitted from the initial stage of hard scattering. Comparisons with several theoretical calculations are also presented. 相似文献
6.
A. M. Hamed 《The European Physical Journal C - Particles and Fields》2009,61(4):597-601
The presented results are the first measurements at RHIC for direct γ-charged hadron azimuthal correlations in heavy ion collisions. We use these correlations to study the color charge density
of the medium through the medium-induced modification of high-p
T
parton fragmentation. Azimuthal correlations of direct photons at high transverse energy (8<p
T
<16 GeV) with away-side charged hadrons of transverse momentum (3<p
T
<6 GeV/c) have been measured over a broad range of centrality for Au+Au collisions and p+p collisions at
GeV in the STAR experiment. A transverse shower shape analysis in the STAR Barrel Electromagnetic Calorimeter Shower Maximum
Detector is used to discriminate between the direct photons and photons from the decays of high p
T
π
0. The per-trigger away-side yield of direct γ is smaller than from π
0 trigger at the same centrality class. Within the current uncertainty the I
CP
of direct γ and π
0 are similar. 相似文献
7.
H. Rauch 《The European physical journal. Special topics》2008,159(1):27-36
Measurements of the π0 and direct photon nuclear modification
factors in p+p and A+A collisions in the PHENIX experiment
at RHIC will be reviewed and
recent results at
GeV will be presented. Using
for the first time the p+p reference measured in the same
experiment instead of averaging world data the π0 suppression
turns out to be almost as large at
GeV as at
GeV, implying gluon densities dNg/dy>800.
Possible origins of photon suppression at high pT in
GeV are discussed in light of the new results on
photon RAA at
GeV. 相似文献
8.
M.J. Russcher 《The European Physical Journal C - Particles and Fields》2007,49(1):231-234
Results are presented of an ongoing analysis of direct photon production in =200 GeV deuteron-gold collisions (d+Au) with the STAR experiment at RHIC. A significant excess of direct photons is observed
near mid-rapidity (0<y<1) and found to be consistent with next-to-leading order pQCD calculations including the contribution
from fragmentation photons.
PACS 25.75.-q 相似文献
9.
Results from RHIC have shown that there is an enhanced baryon/meson ratio in the intermediate transverse momentum range (2<pT<6 GeV/c) in Au+Au collisions at both =130 and 200 GeV. This was initially demonstrated by measurements of the p̄/π- ratio which was then extended in pT by the Λ/K0
S ratio. The data were successfully described by models utilising different hadronization mechanisms: those having recombination
of quarks and others having an interplay between flow, jet quenching and incorporating baryon junction loops. The strange
particle data from the first Au+Au run at =200 GeV gave tantalising hints that the observed enhancement of baryons compared to mesons was diminished by a pT of 6 GeV/c, but a lack of statistics in this range made a definitive statement impossible. Here we present an extended analysis
of identified strange baryons and mesons in Au+Au collisions at =200 GeV using data obtained by the STAR experiment from the 2004 running period. The increase in statistics extends the
measurement of Λ hyperons out to at least 7 GeV/c and K0
S mesons out to 9 GeV/c. This data allows us to place limits on the range where in-vacuum fragmentation functions are applicable
and the effect of baryon dominance is reduced. We also discuss the prospects for making these measurements using multiply-strange
baryons and mesons (Ω and ϕ). 相似文献
10.
S. Sakai 《The European Physical Journal C - Particles and Fields》2007,49(1):383-387
The PHENIX experiment has measured the azimuthal anisotropy parameter v2, the second harmonic of the azimuthal distribution, for electrons at mid-rapidity (|η|<0.35) as a function of transverse
momentum (0.5<pT (GeV/c)<5.0) in Au+Au collisions at =200 GeV. From the result we have calculated the non-photonic electron v2, which is expected to reflect charm quark azimuthal anisotropy, by subtracting the v2 of electrons from other sources such as photon conversions and Dalitz decays. 相似文献
11.
《The European Physical Journal C - Particles and Fields》2008,58(4):531-541
The production of two high-p
T
jets in the interactions of quasi-real photons in e
+
e
− collisions at
from 189 GeV to 209 GeV is studied with data corresponding to an integrated e
+
e
− luminosity of 550 pb−1. The jets reconstructed by the k
⊥
-cluster algorithm are defined within the pseudo-rapidity range −1<η<1 and with jet transverse momentum, p
T
, above 3 GeV/c. The differential di-jet cross-section is measured as a function of the mean transverse momentum
of the jets and is compared to perturbative QCD calculations.
Deceased 相似文献
12.
H. Buesching The PHENIX Collaboration 《The European Physical Journal C - Particles and Fields》2007,49(1):41-45
Over the first five years of operation the PHENIX experiment at RHIC has collected a wealth of data for various systems and
collision energies that is providing valuable information for the understanding of the suppression pattern observed in central
Au+Au collisions at . An overview on transverse-momentum (pT) spectra of π0 and η in different collision energies and systems is presented. 相似文献
13.
Xin Dong 《Acta Physica Hungarica A》2006,25(2-4):435-442
We report recent measurements on the open charm production in d+Au and p+p collisions at $\sqrt {s_{NN} } = 200$ GeV from the STAR detector at RHIC. The two independent measurements — direct open charm hadron (D0, D* etc.) reconstruction and non-photonic single electron spectrum — provide consistent results. The mid-rapidity charm differential cross section per nucleon-nucleon collision from d+Au collisions at RHIC is $d\sigma _{c\bar c}^{NN} /dy = 0.30 \pm 0.04(stat.) \pm 0.09(syst.)$ mb, which is higher than predictions from most of the NLO pQCD calculations. Implications for charmonium production in Au+Au collisions will also be discussed. 相似文献
14.
J. Bielcikova 《The European Physical Journal C - Particles and Fields》2007,49(1):321-326
We present results on two-particle azimuthal correlations of neutral strange baryons (Λ, Λ̄) and mesons (KS
0) for pT=2–6 GeV/c associated with non-identified charged particles in d+Au and Au+Au collisions at =200 GeV measured by the STAR experiment. We investigate in detail the associated yield of charged particles as a function
centrality of the collision and transverse momentum of trigger and associated particles to look for possible flavor, baryon/meson
and particle/anti-particle differences. We compare our results to the proton and pion triggered correlations as well as to
a fragmentation and recombination model.
PACS 25.75.-q; 25.75.Gz 相似文献
15.
David d’Enterria 《Acta Physica Hungarica A》2004,21(2-4):221-228
Two of the most interesting experimental results of heavy-ion reactions at RHIC collider energies are in the hard scattering sector where central Au+Au data show a very different behaviour compared to p+p and peripheral Au+Au collisions. The so-called “high p T π 0 suppression” and the “anomalous” baryon/meson ratio observed by PHENIX in central Au+Au collisions at $\sqrt {s_{NN} } = 200$ GeV are reviewed and compared to various theoretical calculations based on different strongly interacting medium scenarios. 相似文献
16.
D.J. Kim 《The European Physical Journal C - Particles and Fields》2007,49(1):359-364
The PHENIX experiment has studied open heavy flavor production in =200 GeV p+p and d+Au collisions using the semi-leptonic decay into single muons. The results from these measurements and
the details of the analysis technique are presented. The results from p+p collisions obtained at mid-rapidity are compared
to perturbative QCD calculations. The production of light mesons is the major background source for the open flavor measurement
using muons. The nuclear modification factor for light mesons were measured in Cu+Cu collisions at =200 GeV is presented. 相似文献
17.
A. K. Chaudhuri 《The European Physical Journal C - Particles and Fields》2009,61(2):331-338
In a hydrodynamic model, we have studied J/ψ production in Au+Au/Cu+Cu collisions at RHIC energy,
GeV. At the initial time, J/ψ’s are randomly distributed in the fluid. As the fluid evolves in time, the free streaming J/ψ’s are dissolved if the local fluid temperature exceeds a threshold temperature T
J/ψ
. Sequential melting of charmonium states (χ
c
, ψ
′ and J/ψ), with melting temperatures
, T
J/ψ
≈2T
c
and feed-down fraction F≈0.3, explains the PHENIX data on the centrality dependence of J/ψ suppression in Au+Au collisions. J/ψ
p
T
spectra and the nuclear modification factor in Au+Au collisions are also well explained in the model. The model however overpredicts
the centrality dependence of J/ψ suppression in Cu+Cu collisions by 20–30%. The J/ψ
p
T
spectra are underpredicted by 20–30%. The model predicts that in central Pb+Pb collisions at LHC energy,
GeV, J/ψ’s are suppressed by a factor of ∼10. The model predicted a J/ψ
p
T
distribution in Pb+Pb collisions at LHC is similar to that in Au+Au collisions at RHIC. 相似文献
18.
J. C. Dunlop 《Acta Physica Hungarica A》2004,21(2-4):215-220
We report high statistics measurements of inclusive charged hadron production in Au+Au collisions at $\sqrt {s_{NN} } = 200$ GeV and 130 GeV. A large, approximately constant hadron suppression is observed in central Au+Au collisions for 5 ‖p T ‖ 12 GeV/c. The collision energy dependence of the yields and the centrality and p T dependence of the suppression provide stringent constraints on theoretical models of suppression. Models incorporating initial-state gluon saturation or partonic energy loss in dense matter are largely consistent with observations. The p T -dependent suppression expected from models incorporating jet attenuation in cold nuclear matter or absorption of fragmentation hadrons is not observed. 相似文献
19.
Yichun Xu 《The European Physical Journal C - Particles and Fields》2009,62(1):187-190
We report the transverse momentum (p
T
) distributions for identified charged pions, protons and anti-protons using events triggered by high deposit energy in the
Barrel Electro-Magnetic Calorimeter (BEMC) from p+p collisions at
GeV. The spectra are measured around mid-rapidity (|y|<0.5) over the range of 3<p
T
<15 GeV/c with particle identification (PID) by the relativistic ionization energy loss (rdE/dx) in the Time Projection Chamber (TPC) of the Solenoidal Tracker at RHIC (STAR). The charged pion, proton and anti-proton
spectra at high p
T
are compared with published results from minimum bias triggered events and the Next-Leading-Order perturbative quantum chromodynamic
(NLO pQCD) calculations (DSS, KKP and AKK 2008). In addition, we present the particle ratios of π
−/π
+,
, p/π
+ and
in p+p collisions. 相似文献
20.
F. Benedosso 《The European Physical Journal C - Particles and Fields》2007,49(1):61-64
We present measurements of azimuthal correlations between photons (from π0 decay) and charged hadrons in d+Au collisions at =200 GeV. We use di-hadron correlations to study parton fragmentation in d+Au collisions at RHIC. Specifically, the near-side
and away-side peaks of the azimuthal angular difference distribution are used to measure the root-mean-squared (RMS) fragmentation
transverse momentum and the mean intrinsic parton transverse momentum . The measurements with leading photons are compared to results using leading charged particles.
PACS 25.75.-q 相似文献