SELECT * FROM feedbackinfo order by ID DESC
| No. |
Author |
Type |
Topic of Presentation： |
Contact Email |
1 |
Yoshiyuki Onuki |
Poster
|
Future Experiments and Facilities |
y.onuki@riken.jp |
| |
\centerline{\bf Pixel detector of Silicon Vertex Tracker for PHENIX at RHIC}
\vspace{12pt}
\centerline{ {\bf Yoshiyuki~Onuki}$^{\rm a}$ and for the PHENIX Collaboaration}
\vspace{12pt}
\centerline{$^{\rm a} Radiation Laboratory,
RIKEN(The Institute of Physical and Chemical Research)}
\centerline{Hirosawa, Wako-city, Saitama, 350198, Japan {\it
y.onuki@riken.jp}}
\vspace{12pt} \vspace{12pt}
The PHENIX at RHIC has been running for investigating hot and high
density matter in heavy ion collisions and nucleon spin structure in
polarized proton-proton collisions.
We have been developing a silicon vertex tracker (VTX), which is
plan to install in PHENIX in 2009. The purpose of this new detector are
mainly identifying bottom and charm quark by measuring the distance
closest approach in both heavy ion collision and pp collisions, and
identifying jet in the relatively larger acceptance.
The VTX will be located surrounding the beam pipe, where the
collision occur. VTX is designed to cover $|eta|<1.2$
with almost full azimuthal angle.
VTX consists of two major parts; the inner
two layers are pixel-type sensors and the outer two layers are
strip-type sensors. The radii of the four layers are 25$mm$,
50$mm$, 100$mm$ and 140$mm$, respectively.
The inner two pixel layers have 10, 20 pixel sensor modules (ladder)
in $\phi$ direction. RIKEN is assigned to fabricate of the all staves.
A stave is formed 4 sensor staves, each sensor stave
consisting of a silicon pixel sensor matrix 256 $\times$ 128 pixels
of 50 $\times$ 425 $\mu m2$ size as a unit.
A sensor stave is a hybrid device consisting of a pixel sensor matrix
and 4 readout chips interconnected by bump bonding with micro solder balls.
We will report to configuration of PIXEL detector part of the VTX and
current status. |
2 |
Su Houng Lee, Y. Park |
Oral
|
New Theoretical Developments |
suhoung@yonsei.ac.kr |
| |
\documentclass[aps,prc,preprint]{revtex4}
\begin{document}
%%%%%%%%%%%%%%%%%%%%% Title %%%%%%%%%%%%%%%%%%%%%%
\title{$J/\psi$ hadron interaction in vacuum and in QGP}
%%%%%%%%%%%%%%%%%%%% Authors %%%%%%%%%%%%%%%%%%%%%
\author{Su Houng Lee}%}
\email{suhoung@phya.yonsei.ac.kr}
\author{Youngjae Park}
\author{Taesoo Song}
\affiliation{Institute of Physics and Applied Physics, Yonsei
University, Seoul 120-749, Korea}
%%%%%%%%%%%%%%%%%%%% Abstract %%%%%%%%%%%%%%%%%%%%%
\begin{abstract}
The dissociation cross section of $J/\psi$ into open charm states
by hadrons in the vacuum are investigated using the perturbative
QCD. We have completed the Next to Leading order perturbative QCD
calculation, which shows that there is a large 2nd order
correction near the threshold, partly explaining the large
discrepancies between the results based on LO perturbative QCD,
first performed by Peskin, and effective hadronic model. Next, we
discuss the dissociation cross section of $J/\psi$ bound state
above $T_c$, which according to recent lattice results seems to
persist even up to $1.6 \times T_c$. The dominant contribution to
the dissociation comes from the thermal gluons, while the effects
due to thermal quarks are suppressed due to suppressed phase
space. The relevance of this result is discussed in the context of
RHIC and signature of QGP.
\end{abstract}
\maketitle
\end{document}
|
3 |
Haijiang Gong |
Poster
|
Direct Photons, Dileptons and Vector Mesons |
haijiang@skipper.physics.sunysb.edu |
| |
Search for direct photons from AuAu collisions using a new pi0
tagging method in the PHENIX experiment at RHIC
Haijiang Gong(Stony Brook University)
Direct photons provide a tool to study the different stages of a heavy
ion collision, especially the formation of a quark-gluon plasma, without being influenced by the strong interaction and hadronization processes.The yield of direct photons can be determined based on the inclusive photon yield and under consideration of the background from hadronic decays. The double-ratio
(\gamma/\gamma(\pi^{0}))_{measured}/(\gamma/\gamma(\pi^{0}))_{simulated}
technique has been used in PHENIX to estimate direct photon production.
A new method to determine the double-ratio is presented, which should lead to smaller systematic errors at low pT. It uses strict photon
identification in the EMCAL and a charged particle veto to extract a clean photon signal. The photons are then tagged with EMCAL photon candidates, which can be reconstructed with high efficiency, to determine the fraction of photons originating from \pi^{0} decays. Many systematic uncertainties and detector effects cancel in this method. The status of this analysis and comparision with previous published results will be discussed. |
4 |
N. Armesto, with J. L. Albacete and J. G. Milhano |
Oral
|
Low-x Parton Dynamics and Parton Saturation |
nestor@fpaxp1.usc.es |
| |
We calculate some O(\alpha_s^2) corrections to the JIMWLK kernel in the framework of the light-cone wavefunction approach to the high energy limit of QCD. The contributions that we consider originate from higher order corrections in the strong coupling and in the density of the projectile to the solution of the classical EOM that determine the Weizs\"acker-Williams fields of the projectile. We study the structure of these corrections in the dipole limit, showing that they are subleading in the large-N limit and that they cannot be fully recast in the form of dipole degrees of freedom, but rather present a complicated color structure. |
5 |
N. Armesto, L. McLerran and C. Pajares |
Oral
|
QCD at High Temperature and Density |
nestor@fpaxp1.usc.es |
| |
Title: Long Range Multiplicity Correlations in the CGC
Abstract: We discuss forward-backward correlations in the mutliplicity of produced particles in heavy ion collisions. We find the Color Glass Condensate generates distinctive predictions for the long range component of this correlation. In particular, we predict the growth of the long range correlation with the centrality of the collision. We argue that the correlation for mesons is stronger than that for baryons. |
6 |
Shingo Sakai |
Oral
|
Strangeness and Heavy Flavor Production |
shingo@bnl.gov |
| |
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%
{\small \it Quark Matter 2006 Conf. - Nov. 14-20, 2006 - Shanghai
- P. R. China}
\textbf{Please select: oral talk}
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\centerline{\bf Elliptic flow of electron from heavy flavor decay by the PHENIX}
\vspace{12pt}
\centerline{ {\bf S.~Sakai}$^{\rm a}$ for the PHENIX collaboration}
\vspace{12pt}
\centerline{$^{\rm a}$Institute of Physics, The University of
Tsukuba} \centerline{Tsukuba, Ibarak, 305-8571, Japan, {\it
shingo@bnl.gov}}
\vspace{12pt}
\vspace{12pt} \vspace{12pt}
Charm and bottom quarks are believed to be produced in initial collisions via gluon fusion and to propagate through the hot and dense medium created in the collisions. Therefore they can be a powerful probe to study the medium created in heavy ion collisions. One of the biggest discoveries at RHIC is that the elliptic flow ($v_{2}$) for light hadrons, such as pions and kaons, scales with the number of constituent quarks. This scaling behavior is consistent with the predictions of the quark coalescence model, which assumes a finite $v_{2}$ of light quarks such as u quark and s quark. Charm and bottom production can be studied by measuring electrons from their semi-leptonic decays in the PHENIX experiment at RHIC. A recent measurement of electron $v_{2}$ from semi-leptonic charm decay at PHENIX shows large $v_{2}$ in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The $v_{2}$ of the electrons is consistent at low $p_{T}$ with the predictions of a model that assumes charm quark flow. This consistency would suggest that the charm quarks also flow. In addition to charm flow, electron yields from charm and bottom decay also suggest that the heavy quark energy loss is larger than expected in the medium created in Au+Au collisions, indicating a stronger than expected interaction of with the medium.
In this presentation we will show the latest results on $v_{2}$
of heavy flavor semi-leptonic decay electrons measured at PHENIX,
including the final results for 200GeV Au+Au collisions.
\vspace{12pt}
\vspace{12pt}
%\parindent=0pt \textbf{References}
\end{document}
|
7 |
Pibero Djawotho for the STAR Collaboration |
Oral
|
NotSelect |
pibero@indiana.edu |
| |
Quarkonium Production in STAR
Pibero Djawotho for the STAR Collaboration
Indiana University Cyclotron Facility
In the hot and dense matter produced in relativistic heavy-ion collisions, the creation of a quark-gluon plasma is expected to modify the production of quarkonia, significantly suppressing their yields. As a baseline for any estimate of suppression, the production in p+p collisions is mandatory. We present preliminary results on J/psi and Upsilon measurements in p+p collisions at sqrt(s)=200 GeV via the dielectron decay channel in the midrapidity region. A dedicated trigger was used to enhance the quarkonia samples. We compare the results to perturbative calculations and previous measurements. |
8 |
David Blaschke |
Oral
|
Quark Matter in Astro-particle Physics |
david.blaschke@uni-rostock.de |
| |
\documentclass[a4]{article}
\begin{document}
\title{Modern quark matter equations of state vs. compact star observations}
\author{David Blaschke\\
Institute of Physics, Rostock University,
%\\D-18051 Rostock,
Germany\\
Bogoliubov Laboratory for Theoretical Physics, JINR Dubna,
%\\141980 Dubna,
Russia}
\date{ }
\maketitle
\begin{abstract}
Recently, observations of compact stars have provided new data of high
accuracy which put strong constraints on the high-density behaviour of the
equation of state of strongly interacting matter otherwise not accessible in
terrestrial laboratories \cite{Klahn:2006ir}.
The simultaneous measurement of high mass ($M > 2 ~M_\odot$), radius
($R > 12$ km) and surface redshift ($z=0.35$) for EXO 0748-676
\cite{Ozel:2006km} rules out soft equations of state and has provoked a debate
whether the occurence of quark matter in compact stars is excluded as well
\cite{Alford:2006vz}.
In the present contribution it is shown that within modern quantum field
theoretical approaches to quark matter \cite{Blaschke:2005uj} including color
superconductivity and a vector meanfield allow a microscopic description of
hybrid stars which fulfill the new, strong constraints.
For these objects color superconductivity turns out to be essential for a
successful description of the cooling phenomenology in accordance with
recently developed tests \cite{Popov:2005xa}.
Implications for the QCD phase diagram %of symmetric quark matter
to be explored in future generations of nucleus-nucleus collision experiments
at low temperatures and high baryon densities such as CBM @ FAIR are presented.
\end{abstract}
\vspace{-13.5cm}
{\bf \fbox{oral talk}}
\vspace{13.5cm}
\begin{thebibliography}{99}
%\cite{Klahn:2006ir}
\bibitem{Klahn:2006ir}
T.~Kl\"ahn {\it et al.},
%``Constraints on the high-density nuclear equation of state from the
%phenomenology of compact stars and heavy-ion collisions,'
arXiv:nucl-th/0602038.
%%CITATION = NUCL-TH 0602038;%%
%\cite{Ozel:2006km}
\bibitem{Ozel:2006km}
F.~\"Ozel,
Nature {\bf 441}, 1115 (2006)
%``EXO 0748-676 Rules out Soft Equations of State for Neutron Star Matter,'
% arXiv:astro-ph/0605106.
%%CITATION = ASTRO-PH 0605106;%%
%\cite{Alford:2006vz}
\bibitem{Alford:2006vz}
M.~Alford {\it et al.},
%, D.~Blaschke, A.~Drago, T.~Klahn, G.~Pagliara and J.~Schaffner-Bielich,
%``Quark matter and the masses and radii of compact stars,'
arXiv:astro-ph/0606524.
%%CITATION = ASTRO-PH 0606524;%%
%\cite{Blaschke:2005uj}
\bibitem{Blaschke:2005uj}
D.~Blaschke {\it et al.},
%, S.~Fredriksson, H.~Grigorian, A.~M.~Oztas and F.~Sandin,
%``The phase diagram of three-flavor quark matter under compact star
%constraints,'
Phys.\ Rev.\ D {\bf 72} (2005) 065020
%[arXiv:hep-ph/0503194].
%%CITATION = HEP-PH 0503194;%%
%\cite{Popov:2005xa}
\bibitem{Popov:2005xa}
S.~Popov {\it et al.},
%, H.~Grigorian and D.~Blaschke,
%``Neutron star cooling constraints for color superconductivity in hybrid
%stars,'
Phys. Rev. {\bf C 74} (2006) in press; [arXiv:nucl-th/0512098].
%%CITATION = NUCL-TH 0512098;%%
\end{thebibliography}
\end{document} |
9 |
Ivan Vitev |
Oral
|
Strangeness and Heavy Flavor Production |
ivitev@lanl.gov |
| |
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{\small \it Quark Matter 2006 Conf. - November 14-20, 2006 -
Shanghai - P. R. China}
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\centerline{\bf HEAVY QUARK MODIFICATION IN A}
\centerline{\bf COMBINED TRANSPORT + QUENCHING APPROACH }
\vspace{12pt}
\centerline{ {\bf I.~Vitev}$^{\rm a}$, {\bf H.~van Hees}$^{\rm b}$ }
\vspace{12pt}
\centerline{$^{\rm a}$Los Alamos National Laboratory,
Theoretical and Physics Divisions}
\centerline{Los Alamos, NM 87545 USA, {\it ivitev@lanl.gov}}
\centerline{$^{\rm b}$Cyclotron Institute,
Texas A&M University}
\centerline{College Station, TX 77843 USA, {\it hees@comp.tamu.edu}}
\vspace{12pt} \vspace{12pt}
We revisit the question regarding the origin of the nuclear
modification of non-photonic electrons in Au+Au collisions at RHIC
by combining for the first time radiative energy loss, collisional
energy loss and D- and B-resonance interaction calculations to
evaluate the drag and diffusion coefficients for heavy quarks in
the quark-gluon plasma and the mixed phases of heavy ion
reactions. These coefficients are applied in a relativistic
Fokker-Planck equation, which is solved by an equivalent
Langevin simulation to describe heavy-quark quenching and
diffusion within the quark-gluon plasma.
The single electron data from STAR and PHENIX on the nuclear
suppression $R_{AA}(p_T)$ and the elliptic flow
$v_2(p_T)$ measured at RHIC are compared with our theoretical
model.
\vspace{12pt}
\vspace{12pt}
\parindent=0pt \textbf{References}
[1] H. van Hees, I.~Vitev, in preparation.
\end{document}
|
10 |
C. Zhong |
Oral
|
Strangeness and Heavy Flavor Production |
czhong@bnl.gov |
| |
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\def\Journal#1#2#3#4{{#1} {\bf #2}, #3 (#4)}
\def\PRL{ Phys. Rev. Lett.}
\def\PLB{ Phys. Lett. B}
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Shanghai - P. R. China}
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\centerline{\bf Scaling of charm integrated cross section and}
\centerline{\bf modification of its transverse momentum spectra}
\centerline{\bf in d+Au and Au+Au collisions at RHIC}
\vspace{12pt}
\centerline{{\bf C.~Zhong$^{\rm a}$} for the STAR Collaboration}
\vspace{12pt}
\centerline{\footnotesize $^{\rm a}$Department of Nuclear Physics,
Shanghai Institute of Applied Physics}
\centerline{Shanghai 201800, P. R. China, {\it czhong@bnl.gov}}
\vspace{12pt}
In relativistic heavy-ion collisions, charm quarks are believed to
be produced at early stages via initial gluon fusion and their
production cross section can be evaluated by perturbative
QCD~\cite{cacciari}. Study of the binary collision ($N_{bin}$)
scaling properties for the charm total cross section among p+p,
d+Au to Au+Au collisions can test if heavy-flavor quarks are
produced exclusively at initial impact~\cite{ffcharm}. Due to the
heavy mass of charm quark, charmed hadrons might freeze out
earlier than light flavor hadrons. Their flow velocity might be a
good indicator of light flavor thermalization occurring at the
partonic level~\cite{therm,AMPT,batsouli}.
%Charm energy loss can
%be inferred by the modification factor of its semileptonic decayed
%electron, which is extremely sensitive to the properties of
%medium. %% Fuqiang modify the text to be clear
Charm energy loss, highly sensitive to the properties of medium,
can be inferred by the modification factor of its semileptonic
decayed electron.
Besides the measurement of D meson production from the
analysis of their hadronic ($D^0\rightarrow K\pi$ up to 3 GeV/$c$)
and semileptonic ($D\rightarrow e+X$ at 0.9\textless$p_T$\textless5.0
GeV/$c$) decays in $\sqrt{s_{_{NN}}}=200$ GeV Au+Au collisions, we
proposed and measured $D\rightarrow \mu+X$ at
0.17\textless$p_T$\textless0.27 GeV/$c$, which greatly constrains
the charm total cross section~\cite{ffcharm}. In addition, we are
able to extract freeze-out parameters based on a blast-wave model.
The transverse momentum ($p_T$) spectra and the nuclear modification
factors for $D^0$ and for electron/muon from charm semileptonic
decays will be presented. The differential cross-section
$d\sigma/dy$ of charm production at $\sqrt{s_{_{NN}}}=200$ GeV in
d+Au and Au+Au collisions will be reported.
\vspace{-0.35cm}
\begin{thebibliography}{10}
\bibitem{cacciari} M. Cacciari, P. Nason and R. Vogt,
\Journal{\PRL}{95}{2005}{122001}
\bibitem{ffcharm} H.D. Liu {\it et al.}, \Journal{\PLB}{639}{2006}
{441-446} e-print Arxiv: nucl-ex/0601030
\bibitem{therm}
STAR Collaboration, J. Adams {\it et al.},
\Journal{\PRL}{92}{112301}{2004}
\bibitem{AMPT} B. Zhang {\it et al.}, nucl-th/0502056
\bibitem{batsouli}
S. Batsouli {\it et al.}, \Journal{\PLB}{557}{2003}{26-32} e-print
Arxiv: nucl-th/0212068
\end{thebibliography}
\end{document}
|
11 |
Arkadij Taranenko |
Oral
|
Global and Collective Dynamics in A+A Collisions |
arkadij@rcf.rhic.bnl.gov |
| |
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{\small \it Quark Matter 2006 Conf. - Nov. 14-20, 2006 - Shanghai
- P. R. China}
\textbf{Please select: oral talk}
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\centerline{\bf PHENIX Studies of the Scaling Properties of Elliptic Flow at
RHIC Energies}
\vspace{12pt}
\centerline{ {\bf Arkadij Taranenko}$^{\rm a}$, for the PHENIX Collaboration}
\vspace{12pt}
\centerline{$^{\rm a}$Department of Chemistry, SUNY Stony Brook}
\centerline{Stony Brook, NY, 11794, U.S.A., {\it
arkadij@rcf.rhic.bnl.gov}}
\vspace{12pt} \vspace{12pt}
Elliptic flow measurements provide a sensitive probe of the
thermodynamic and
transport properties of the hot and dense medium created in ultra-
relativistic heavy ion collisions. Recent measurements at RHIC,
have been
found to be compatible with perfect fluid hydrodynamics for several
particle
species measured over a broad range of $p_T$s and centralities.
A detailed test of several scaling predictions of perfect fluid
hydrodynamics
can provide important experimental constraints for the decay
dynamics of the
hot and dense QCD matter produced in such collisions.\\
A comprehensive analysis of the scaling properties of the
fine structure of elliptic flow (i.e its detailed dependence on
transverse
momentum, particle type, centrality, system size, colliding energy,
etc.)
measured by the PHENIX collaboration in Au+Au/Cu+Cu collisions at
$\sqrt{s_{NN}}$= 62.4 - 200 GeV
will be presented. The implications of these scalings as
constraints for
the equation of state and the transport coefficients will also be
discussed.
\end{document}
|
12 |
Baldo Sahlmueller |
Oral
|
Jet Quenching and Medium Modification of Jet Parti |
sahlmul@nwz.uni-muenster.de |
| |
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{\small \it Quark Matter 2006 Conf. - Nov. 14-20, 2006 - Shanghai
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\centerline{\bf Diagnosing energy loss: PHENIX results on high-$p_T$ hadron spectra}
\vspace{12pt}
\centerline{ {\bf B.~Sahlmueller}$^{\rm a}$, for the PHENIX collaboration}
\vspace{12pt}
\centerline{$^{\rm a}$Institut fuer Kernphysik, University of
Muenster} \centerline{48149 Muenster, Germany, {\it
sahlmul@nwz.uni-muenster.de}}
\vspace{12pt} \vspace{12pt}
Measurements of particle yields at high transverse momentum at RHIC
have shown a strong suppression of neutral meson and charged hadron
yields in central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV
compared to a binary scaled p+p reference. A suppression has also been
observed in Cu+Cu collisions at the same energy, similar in strength
to that in Au+Au collisions for an equal number of participants. The
observed suppression has been attributed to the energy loss of partons
in the hot and dense matter created in the collision. The exact
suppression mechanism, however, remains unclear.\\
PHENIX has measured spectra of $\pi^{0}$, $\eta$, and non-identified charged
hadrons in various collision systems and at different energies. These
measurements can provide important information for understanding the
suppression mechanism at play. In particular, a new 62.4 GeV p+p data
set is important as a crucial baseline for understanding particle
production in Au+Au and Cu+Cu collisions at the same energy. New Cu+Cu
data at 22.4 GeV and 62.4 GeV complement the existing data sets
and allow a systematic study of the energy and collision species
depencence over a broad range, including a comparison with CERN SPS
results. We will present the latest results of these measurements.
\end{document} |
13 |
DongJo Kim |
Poster
|
Strangeness and Heavy Flavor Production |
djkim@bnl.gov |
| |
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{\small \it Quark Matter 2006 Conf. - Nov. 14-20, 2006 - Shanghai
- P. R. China}
\textbf{Please select: ( "poster")}
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\centerline{\bf Heavy flavor production from single muon measurement in Cu+Cu collisions at RHIC}
\vspace{12pt}
\centerline{ {\bf DongJo Kim}$^{\rm a}$ for the PHENIX Collaboration}
\vspace{12pt}
\centerline{$^{\rm a}$Department of Physics, University of Jyvaskyla}
\centerline{P.O.Box 35, FI-40014 Jyvaskyla Finland, {\it
djkim@phys.jyu.fi}}
\vspace{12pt} \vspace{12pt}
\begin{abstract}
The measurement of open charm production in various collision species
at different energies is important to study the properties of matter
formed in the early stage of relativistic heavy ion collisions, especially
to understand charm energy loss.
The RHIC facility provided Cu+Cu collisions at $\sqrt{s_{NN}}$ = 200, 62 and 22 GeV in 2005.
This lighter colliding system compared with Au+Au can give
much better $N_{part}$ and $N_{coll}$ precision in the lower $N_{part}$
region, and the comparison between two different colliding energies
may give us a better systematic understanding of charm production.
PHENIX detectors measure muons in the rapidity range $1.2 < | \eta |
< 2.4$, thus enabling us to study open charm as well as light
meson production at forward rapidity.
The status of the analysis regarding centrality, transverse momentum and rapidity dependence
of single muon production from open heavy flavor and light mesons decay in Cu+Cu collisions
at $\sqrt{s_{NN}}$=200 GeV and 62.4GeV will be presented.
\end{abstract}
\end{document}
|
14 |
Rashmi Raniwala, Sudhir Bhardwaj and Sudhir Raniwa |
Poster
|
Global and Collective Dynamics in A+A Collisions |
rashmi.raniwala@cern.ch |
| |
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{\small \it Quark Matter 2006 Conf. - Nov. 14-20, 2006 - Shanghai
- P. R. China}
\textbf{poster}
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\centerline{\bf Elliptic flow of inclusive photons and charged particles in CuCu collisions at 200 GeV}
\vspace{12pt}
\centerline{ {\bf Rashmi ~Raniwala}, {\bf Sudhir ~Bhardwaj} and {\bf Sudhir ~Raniwa}}
\vspace{6pt}
\centerline{ \bf for the STAR Collaboration}
\vspace{12pt}
\centerline{Department of Physics, University of
Rajasthan} \centerline{Jaipur 302004, India}\centerline{\it
rashmi.raniwala@cern.ch}
\vspace{12pt} \vspace{12pt}
One of the major successes of the hydrodynamic description of relativistic heavy ion collisions
is the observation of flow. Particles are emitted anisotropically in the azimuthal plane due to
pressure gradients in azimuthally asymmetric collision zone. The second coefficient in the Fourier
expansion of the observed azimuthal distribution, $v_2$, characterises the elliptic flow. Results
at SPS and at RHIC have shown a scaling of elliptic flow in eccentricity of the initial system and
the particle density in the transverse plane, validating the low density limit. The large values of
$v_2/\epsilon$ at large multiplicities approach the hydrodynamic limit, indicating complete
thermalisation. Models have had limited success in explaining the observed differential flow of
identified particles. It therefore becomes necessary, and advantageous, to measure the flow for
different particle species in different phase space regions. In the present work, we shall present
results on the observed flow in inclusive photons in CuCu collisions at 200 GeV. The inclusive
photons are measured in the preshower Photon Multiplicity Detector (PMD) where the photons are
identified by applying cuts on the cluster ADC and the cluster size. The choice of cluster parameters
determines the efficiency and the purity of the detected photon sample. The PMD is sensitive to
photons of very low momentum (p$_T \sim$ 30 MeV/c) and hence measures the true p$_T$ integrated flow.
To avoid non- flow correlations the event plane has been determined using charged particles
measured in the TPC, and also in the FTPC. The stability of the results is investigated by
obtaining the event planes in different $\eta$ regions, where a slight systematic dependence
has been observed. Further, the effect of changing the PMD cluster parameters on the observed
$v_2$ is also being investigated. The preliminary results will be compared to results of simulated
data where a p$_T$ dependent flow is introduced in Hijing events, and the $v_2$ is obtained for
the simulated clusters in the PMD using the known event plane. The preliminary results will also
be compared with similar results for charged particles in different $\eta$ regions measured in
the same experiment. Any systematic effect of changing the region where the event plane is
determined is also studied, and the effect of non-flow correlations is determined.
\vspace{12pt}
\end{document}
|
15 |
Rudolph C. Hwa |
Oral
|
Hadron Correlations and Fluctuations |
hwa@uoregon.edu |
| |
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\centerline{\bf Suppression of Statistical Background in Event-Structure Analysis Using Factorial Moments}
\vspace{12pt}
\centerline{ {\bf C.B.~Chiu}$^{\rm a}$ and {\bf R.C.~Hwa}$^{\rm b}$}
\vspace{12pt}
\centerline{$^{\rm a}$Center for Particle Physics and Department of Physics, University of Texas at Austin} \centerline{Austin, TX 78712, USA, {\it
chiu@physics.utexas.edu}}
\vspace{12pt}
\centerline{$^{\rm b}$Institute of Theoretical Science and Department of Physics, University of Oregon} \centerline{Eugene, OR 97403-5203, USA, {\it hwa@uoregon.edu}}
\vspace{12pt} \vspace{12pt}
In the study of event structure of jet production in heavy-ion collisions the conventional approach is to subtract the background after summing over all events. It is meaningless to make background subtraction event by event. However, summing over all events is a process in analysis that often degrades the signal. To enhance the signature we propose a measure based on factorial moments that largely filter out the statistical fluctuation in every event. The factorial moments are sensitive to the jet characteristics without the necessity of background subtraction. We have applied the method successfully to the analysis of azimuthal distribution of events triggered by high $p_T$ particles. Asymmetry moments can well separate one-jet and two-jet recoil scenarios. Application of this method to the analysis of the RHIC data on jet correlation may provide a common framework to compare results from widely different experimental conditions and various subtraction schemes.
\end{document}
|
16 |
Monika Sharma for the STAR collaboration |
Oral
|
Global and Collective Dynamics in A+A Collisions |
monika@rcf.rhic.bnl.gov |
| |
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\centerline{\bf Energy and system size dependence of photon production}
\centerline{\bf at forward rapidities at RHIC}
\vspace{12pt}
\centerline{ {\bf Monika Sharma}$^{\rm a}$ for the STAR Collaboration}
\vspace{12pt}
\centerline{$^{\rm a}$Department of Physics, Panjab University}
\centerline{Chandigarh, India, {\it monika@rcf.rhic.bnl.gov}}
\vspace{12pt} \vspace{12pt}
In relativistic heavy ion collisions, global observables like
particle multiplicity and their spatial distribution provide
information on particle production mechanisms and the
evolution of the system formed in the collisions.
Photon multiplicity measurements at forward rapidity
have been carried out using a Photon Multiplicity Detector (PMD) [1]
in the STAR experiment. First results from this detector
have provided useful insight into the mechanism of particle production
at RHIC [2].
\\In the present talk we discuss the energy and system size dependence
of pseudorapidity ($\eta$) and multiplicity distributions of photons
measured in the region $2.3 \leq \eta \leq 3.7$ for Au+Au and Cu+Cu
collisions at $\sqrt{s_{NN}}$ = 200 and 62.4 GeV.
The results on the system size and energy dependence of
longitudinal scaling for photons will be discussed.
Comparison of pseudorapidity distributions to
various particle production models will be presented.\\
\vspace{12pt}
\parindent=0pt \textbf{References}
[1] M.M. Aggarwal {\it et al.}, \textit{Nucl. Instrum. Meth. A\/} 499, 751 (2003).
\vspace{12pt}
[2] J. Adams {\it et al.}, (STAR collaboration), \textit{Phys. Rev. Lett.\/} 95, 062301 (2005).
\end{document}
|
17 |
Jinhui Chen |
Oral
|
Global and Collective Dynamics in A+A Collisions |
jhchen@physics.ucla.edu |
| |
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\centerline{\bf Spin alignment of vector mesons ($k^{*0}$,$\phi$)
in Au+Au and p+p collisions at $\sqrt{s_{NN}}$ = 200 GeV}
\vspace{12pt}
\centerline{ {\bf Jin~Hui~Chen}~(For STAR Collaboration)}
\vspace{12pt}
\centerline{Nuclear Physics Division, Shanghai Institute of
Applied Physics, CAS} \centerline{Shanghai, 201800, P. R. China,
{\it jhchen@physics.ucla.edu}}
\vspace{12pt}
\vspace{12pt} \vspace{12pt}
%%%
Spin alignment of vector mesons is a unique probe of particle
production mechanism. References[1,2,3] showed that deviation of
spin density matrix $\rho_{00}$ from 1/3 could shed light on
particle production from coalescence or fragmentation of polarized
quarks. In non-central collisions bulk partonic matter with large
angular momentum can be produced and the angular momentum may be
coupled to the spin of the vector mesons. Measurements of
$k^{*0}$, $\phi$ spin alignment allow us to understand particle
production and spin-orbital coupling from bulk partonic matter to
individual particles at intermediate transverse momentum. We will
report the STAR measurement of $k^{*0}$, $\phi$ spin alignment up
to transverse momentum $p_{T}$ = 5 GeV/c at mid-rapidity in Au+Au
and p+p collisions at $\sqrt{s_{NN}}$ = 200 GeV. The production
mechanism of $k^{*0}$ and $\phi$ will be discussed.
\vspace{12pt}
\vspace{12pt}
\vspace{12pt}
\parindent=0pt \textbf{References}
[1] Z.T. Liang, X.N. Wang, \textit{Phys. Lett. B\/}, 629 (2005)
20-26.
[2] Z.T. Liang, X.N. Wang, \textit{Phys. Rev. Lett.\/}, 94 (2005)
102301.
[3] S.A. Voloshin nuch-th/0410089.
\end{document} |
18 |
Tatsuya Chujo |
Oral
|
Global and Collective Dynamics in A+A Collisions |
chujo@sakura.cc.tsukuba.ac.jp |
| |
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\centerline{\bf Excitation functions of baryon anomaly and freeze-out properties at RHIC-PHENIX}
\vspace{12pt}
\centerline{ {\bf T.~Chujo}$^{\rm a}$ for the PHENIX Collaboration}
\vspace{12pt}
\centerline{$^{\rm a}$Institute of Physics, University of Tsukuba}
\centerline{Tsukuba, Ibaraki, 305-8571, Japan, {\it
chujo@sakura.cc.tsukuba.ac.jp}}
\vspace{12pt} \vspace{12pt}
The baryon anomaly is one of the surprising discoveries at the Relativistic
Heavy Ion Collider (RHIC).
It brought us new ideas of hadronization processes and
in-medium effects at the extreme condition, such
as a quark recombination, a hydrodynamical collective flow with jet quenching,
and a baryon junction in central Au+Au collisions at $\sqrt{s_{NN}} = $ 200 GeV.
The measurements of (anti)proton to pion ratios and the nuclear modification
factors $R_{AA}$ for identified hadrons, as a function of beam energies
in different collision systems, provide an important information to study the
onset effect of baryon anomaly at RHIC and its evolution in detail.
In 2004 and 2005 RHIC runs, the PHENIX experiment has accumulated the first
intensive lower beam energy data sets in Au+Au 62.4 GeV, and in Cu+Cu 22.5, 62.4 GeV.
\\
\\
We present the preliminary results of $p_T$ spectra, $dN/dy$, particle ratios, and $R_{AA}$
for $\pi^{\pm}/K^{\pm}/p/\overline{p}$ in Cu+Cu at $\sqrt{s_{NN}}$ = 22.5 and 62.4 GeV,
and in Au+Au at 62.4 GeV, measured by the high resolution Time-of-Flight detector
in PHENIX. We also show the beam energy and system size dependences of hadron kinetic
and chemical freeze-out properties at RHIC by performing the blast wave fit and statistical
thermal model fit for all available identified spectra results in PHENIX; i.e. p+p (200 GeV),
d+Au (200 GeV), Cu+Cu (22.5, 62.4, 200 GeV), and Au+Au (62.4, 200 GeV). The excitation
function of the collective radial flow, baryon chemical potential, yields, particle ratios
will be reviewed. We will also report the latest status of $p_T$ spectra measurement in p+p
at 62.4 GeV, which was newly taken in 2006 RHIC run by PHENIX and will gives an
important reference spectra for $R_{AA}$ in both Au+Au and Cu+Cu at 62.4 GeV with less
ambiguities.
\vspace{12pt}
\end{document}
|
19 |
chun zhang |
Oral
|
Jet Quenching and Medium Modification of Jet Parti |
zhangc@rcf.rhic.bnl.gov |
| |
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\centerline{\bf Study of Parton-Medium Interactions via Two- Three- Particle Jet Correlations in PHENIX }
\vspace{12pt}
\centerline{ {\bf Chun ZHANG for the PHENIX collaboration}$^{\rm a}$}
\vspace{12pt}
\centerline{$^{\rm a}$ Oak Ridge National Lab.} \centerline{Oak Ridge, TN, 37831, US, {\it
zhangc@rcf.rhic.bnl.gov}}
\vspace{12pt} \vspace{12pt}
Jet quenching[1], one of the key pieces of evidence supporting the discovery of
strongly coupled quark-gluon plasma at RHIC, is a result of strong interactions
between hard-scattered partons and the medium created in relativistic heavy
ion collisions. Studying the medium modifications of jets by comparing the
jet yield and shape in heavy ion collisions with those in $p+p$ at
different transverse momenta ($p_T$) and collision geometries can help us
to answer questions such as how the energy carried by hard-scattered partons
is dissipated in the medium. Experimental results from RHIC experiments have
already shown various intriguing features of jet modification[2,3]. Particularly,
the double-peaked away-side profile at modest $p_T$ in central and mid-central
heavy ion collisions has inspired several very different theoretical scenarios
including Bending-Jet and Color-Cerenkov-Radiation to describe the interactions
between partons and the medium.
We use a particle azimuthal correlation technique to construct jet signals
statistically. In two-particle correlations, a high pT trigger particle
is used to tag jet events and the near- and away-side jet shape and yield
are studied. In addition, 3-particle correlations, which can more powerfully
test the various novel theories of the double-peaked away-side profile,
are also studied. The PHENIX experiment has collected a large dataset
in $Au+Au$ and $Cu+Cu$ that enables us to systematically scan the jet
modification for different pT bins and different collision geometries
using unidentified charged hadrons. In this talk the latest results from
these studies will be reviewed and discussed
\vspace{12pt}
\vspace{12pt}
\parindent=0pt \textbf{References}
%\vspace{6pt}
[1] PHENIX, K.~Adcox et. al., \textit{Nucl. Phys.} A~757, p.184 (2005).
%\vspace{6pt}
[2] PHENIX, S. S. ~Adler et. al., \textit{Phys. Rev. Lett.} v~97, p.052301 (2006).
%\vspace{6pt}
[3] F.~Wang, \textit{J. Phys.} G~90, p.S1299 (2004).
\end{document}
|
20 |
Anders Knospe |
Oral
|
Strangeness and Heavy Flavor Production |
anders.knospe@yale.edu |
| |
Non-photonic electron yields from Cu+Cu collisions at $\sqrt{s_{NN}} = 200$ GeV at STAR.
Anders Knospe (for the STAR Collaboration)
Yale University
All partons are thought to lose energy through gluon radiation as they pass through the hot and dense medium produced in high-energy nucleus-nucleus collisions. It is expected that heavy quarks lose less energy in the medium than light quarks due to the suppression of small-angle gluon radiation (the dead cone effect). Thus, heavy quarks should be a sensitive probe of the medium. Heavy-quark production can be measured through the spectrum of non-photonic electrons, which is dominated by the semileptonic decays of heavy-flavor mesons.
Preliminary non-photonic electron spectra are extracted for Cu+Cu collisions at $\sqrt{s_{NN}} = 200$ GeV and are compared to the non-photonic electron yields from p+p and Au+Au collisions at the same energy. This provides a valuable test of the dependence of the non-photonic electron yield on system size. |
21 |
Paul Chung |
Oral
|
Hadron Correlations and Fluctuations |
pchung@mail.chem.sunysb.edu |
| |
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\centerline{\bf Probing the nature of the long-range structure observed in the pion emission source at RHIC-PHENIX}
\vspace{12pt}
\centerline{ {\bf Paul Chung}$^{\rm a}$ }
\centerline{ {\bf for the PHENIX collaboration} }
\vspace{12pt}
\centerline{$^{\rm a}$Department of Chemistry, SUNY Stony Brook} \centerline{Stony Brook, New York, 11794, USA, {\it
pchung@mail.chem.sunysb.edu}}
\vspace{12pt} \vspace{12pt}
A deconfined phase of nuclear matter is expected to be formed at the
high energy densities created in relativistic heavy ion collisions. It is
widely believed that important signatures for the formation of such a phase
are reflected in the space-time extent and the shape of particle emission
source functions.
Recently, 1-Dimensional source imaging techniques have revealed a
non-trivial long range structure in the two-pion emission source at RHIC
energies. In order to determine the origins of this long range structure,
it is necessary to carry out a 3-Dimensional source imaging analysis of the
pion emission source shape, possibly for several different transverse momentum
($k_T$) values of the pion pairs and colliding systems.
The PHENIX Collaboration at RHIC has acquired $\sim$ 1.5 billion
Au+Au events at $\sqrt{s_{NN}}$=200GeV during the year-2004.
This large data set allows for the extraction of the 3-Dimensional shapes for pion emission
sources as a function of transverse momentum with very high resolution.
These 3-Dimensional source images will be discussed in the context of
Gaussian shape assumption and compared with model calculations in order to
assess the role of resonances. Also, the latest status of 3D pion source
images from Cu+Cu events at $\sqrt{s_{NN}}$=200GeV will be reported.
\end{document}
|
22 |
Mark J. Horner |
Oral
|
Jet Quenching and Medium Modification of Jet Parti |
mjhorner@lbl.gov |
| |
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\centerline{\bf Low- and intermediate-$p_T$ azimuthal di-hadron correlations from }
\centerline{\bf $\sqrt{s_{NN}}=200 \rm{GeV}$ AuAu collisions measured in STAR.}
\vspace{12pt}
\centerline{ {\bf M.J.~Horner}$^{\rm a}$$^{\rm b}$ }
\vspace{12pt}
\centerline{ for the STAR Collaboration. }
\vspace{12pt}
\centerline{$^{\rm a}$Nuclear Science Division, Lawrence Berkeley National Laboratory} \centerline{Berkeley, California, 94720, USA, {\it
mjhorner@lbl.gov}}
\vspace{12pt}
\centerline{$^{\rm b}$UCT-CERN Research Centre, Physics Department} \centerline{University of Cape Town, Rondebosch, Western Cape,
7701, South Africa}
\vspace{12pt} \vspace{12pt}
Low- and intermediate-$p_T$ di-hadron correlations have already been used to uncover novel and exciting results at RHIC, tying together hard processes with bulk properties. Using the full Run IV high statistics dataset, we present systematic studies of di-hadron correlations for various trigger $p_T$ selections, starting in the coalesence dominated region and extending up into the domain of fragmentation dominated triggers. By studying these selections as a function of centrality we vary the in-medium path lengths traversed by the hard partons, providing an additional systematic to discriminate different contributions. In addition we study the associated $p_T$ dependence to distinguish between various radiative and hydrodynamic scenarios. A first study of near-side, long-range $\Delta\eta$ correlations at low-$p_T$ is also presented.
These studies probe the significance of hydrodynamic, coalescence/recombination and radiative contributions to the correlation shapes as the contributions vary with $p_T$ and centrality and need to be considered simultaneously to describe correlation shapes. The only way to deconvolute contributions is to study di-hadron correlations as differentially and systematically as possible.
The complete set of systematic results are discussed in light of the interplay between radiative, hydrodynamic and recombination scenarios, placing significant constraints on complete theoretical treaments of energy loss and bulk evolution scenarios.
\vspace{12pt}
\end{document} |
23 |
I. Selyuzhenkov for the STAR Collaboration |
Oral
|
Global and Collective Dynamics in A+A Collisions |
seluzhen@physics.wayne.edu |
| |
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\centerline{\bf Global polarization of Lambda hyperons in Au+Au collisions at RHIC}
\vspace{12pt}
\centerline{ {\bf I.~Selyuzhenkov}$^{\rm a}$ for the STAR Collaboration}
\vspace{12pt}
\centerline{$^{\rm a}$Department of Physics and Astronomy, Wayne State University
} \centerline{Detroit, MI, 48201, USA, {\it
seluzhen@physics.wayne.edu}}
\vspace{12pt} \vspace{12pt}
The system created
in a non-central nucleus-nucleus collision
possesses large angular orbital momentum.
Due to the spin-orbital coupling,
particles produced in such a system could become globally polarized along the
direction of the initial system angular momentum.
Such transformation of the angular orbital momentum
into the particle spin can happen
at different evolution stages of the system created
in nucleus-nucleus collisions.
Measurements of various observable
consequences such as global spin alignment of vector mesons
and global hyperon polarization could be used as an effective
tool to probe the different hadronization mechanisms.
In this talk, we present the results of the global polarization
measurements in Au+Au collisions at $\sqrt{s_{NN}}$=62 GeV and $200$ GeV
performed with the STAR detector at RHIC.
The global polarization of the system is examined by measuring the polarization
of $\Lambda$ hyperons with respect to the system angular orbital momentum,
perpendicular to the collision reaction plane.
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|
24 |
Terence J Tarnowsky |
Poster
|
Hadron Correlations and Fluctuations |
tjt@physics.purdue.edu |
| |
Energy and System size dependence study of percolation phase transition
Terence J Tarnowsky for the STAR Collaboration
Multiparticle production at high energies can be described in terms of color strings stretched between projectile and target nuclei. As the string density increases, overlap among the strings leads to cluster formation. At some critical density, a macroscopic cluster appears that spans the entire system. This marks the percolation phase transition. Transverse momentum distributions of particles produced in pp, d+Au, Cu+Cu, and Au+Au at $\sqrt{s_{NN}}$ = 200 GeV and Cu+Cu and Au+Au at $\sqrt{s_{NN}}$ = 62.4 GeV have been analyzed to determine the string density parameter ($\rho$). In two dimensional percolation theory, the critical value of $\rho$ is $\rho_{c}$ $\simeq$ 1.12-1.20. In high energy collisions, this value is ~1.8 to account for the non-uniform parton distribution. For Au+Au data at $\sqrt{s_{NN}}$ = 200 GeV, the value of $\rho$ is found to be above the critical value for the most central events. In case of Cu+Cu at $\sqrt{s_{NN}}$ = 200 GeV, the most central events are barely above the critical percolation threshold. For all other systems and energies the string density parameter is below the critical value. This supports the idea of string percolation, which at high string density is a possible mechanism to explore the hadronic transition to a Quark Gluon Plasma phase. |
25 |
Brijesh K Srivastava |
Oral
|
Hadron Correlations and Fluctuations |
brijesh@physics.purdue.edu |
| |
Understanding the Particle Production Mechanism with Correlation Studies Using Long and Short Range Correlations and the Balance Function.
Brijesh Srivastava for the STAR Collaboration
The study of correlations among particles produced in different rapidity regions may provide an understanding of particle production mechanisms. Production of particles in the central rapidity region is dominated at all energies by short range correlations. Correlations that extend over a longer range are observed in hadron-hadron interactions only at higher energies. The rapidity correlations between oppositely charged particles, the so called balnce function has also been proposed as a measure of the hadronization time. Results for short and long-range multiplicity correlations (forward-backward) are presented for Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. These correlations are measured with increasing values of a gap in pseudorapidity, from no gap at midrapidity to a separation of 1.6 units (+/- 0.8). A suppression in the correlation strength near midrapidity is observed in central Au+Au data at $\sqrt{s_{NN}}$ = 200 GeV, along with an increase in long-range correlations with larger rapidity gaps. This pattern is seen only for low transverse momentum ($p_{t}$) particles, $p_{t}$ < 1 GeV. For $p_{t}$ > 1 GeV, the suppression in short range correlations is diminished. This result may indicate a reduction in number of particle sources for central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and the possible formation of high density matter. Both string fusion/percolation and color glass condensate can explain the long range correlations observed in data. The balance function (BF) has been measured for identified charged pions and kaons. BF for identified charged pions narrow in central collisions while the BF for charged kaons show no centrality dependence. This difference may indicate that pions and kaons are created at different times. The results from the pseudorapidity, centrality and transverse momentum dependence of BF are also presented. |
26 |
Debasish Das ( for the STAR Collaboration ) |
Oral
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Hadron Correlations and Fluctuations |
ddas@veccal.ernet.in , debasish@rcf.rhic.bnl.gov |
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{\small \it Quark Matter 2006 Conf. - Nov. 14-20, 2006 - Shanghai
- P. R. China}
\textbf{Please select: (`` oral talk ')}
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\centerline{ {\bf Identical Meson Interferometry in STAR Experiment}}
\vspace{12pt}
\centerline{ {\bf Debasish Das} }
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\centerline{ {\bf (for the STAR Collaboration)}}
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\centerline{Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata 700064;}
{\it ~~~~~~~~~~~~~~~~~~~~ddas@veccal.ernet.in; debasish@rcf.rhic.bnl.gov}
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\vspace{12pt}
The influence of Bose-Einstein statistics on multi-particle production
processes characterized for various systems and energies by
the STAR Collaboration provide interesting information about the space-time
dynamics of relativistic heavy-ion collisions at RHIC.
We present the new systematic analysis of the centrality and $m_{T}$
dependence of two-pion interferometry in Au+Au collisions at
$\sqrt{s_{\rm{NN}}}$ = 62.4 GeV and Cu+Cu collisions
at $\sqrt{s_{\rm{NN}}}$ = 62.4 and 200 GeV. We compare the new data
with previous STAR measurements from p+p, d+Au and Au+Au[1] collisions
at $\sqrt{s_{\rm{NN}}}$ = 200 GeV.
In all systems and centralities, HBT radii decrease with $m_{T}$
in a similar manner, which is qualitatively consistent with collective flow[1].
The ratio, $R_{out}$$/$$R_{side}$, shows no sharp behavior with
collision energy, indicating a weak evolution of freeze-out timescales
with energy density.
The scaling of the apparent freeze-out volume[2] with the number of
participants and charged particle multiplicity is studied. Measurements
of Au+Au collisions at same centralities and different energies yield
different freeze-out volumes, which mean that $N_{part}$ is not a
suitable scaling variable. The freeze-out volume estimates for all presented
systems show a linear dependence as a function of charge particle multiplicity.
The multiplicity scaling of the measured HBT radii is found to be
independent of colliding system and collision energy.
\vspace{12pt}
\parindent=0pt \textbf{References}
[1] J. Adams $\it{et}$ $\it{al.}$ (STAR Collaboration) Phys. Rev. C {\bf 71},044906 (2005).
[2] D.Adamova $\it{et}$ $\it{al.}$ (CERES Collaboration) Phys. Rev. Lett.{\bf 90},022301 (2003).
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27 |
Sergei A. Voloshin for the STAR Collaboration |
Oral
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Global and Collective Dynamics in A+A Collisions |
voloshin@wayne.edu |
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{\small \it Quark Matter 2006 Conf. - November 14-20, 2006 -
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\centerline{\bf Energy and system size dependence of elliptic flow
and $v_2 / \varepsilon$ scaling}
\vspace{12pt}
\centerline{ {\bf Sergei A. Voloshin}$^{\rm a}$ for the {\bf STAR Collaboration}
}
\vspace{12pt}
\centerline{$^{\rm a}$Department of Physics and Astronomy, Wayne State
University }
\centerline{Detroit, Michigan, 48201, U.S.A.; E-mail:
{\it voloshin@wayne.edu}}
\vspace{12pt} \vspace{12pt}
Elliptic flow measurements at RHIC are considered to be major tools for
establishing the creation and thermalization of strongly interacting
Quark Gluon Plasma at RHIC. The evolution of elliptic flow with
collision energy and system size provides important information on
the nature of the matter created in nuclear collisions at high energies.
In this talk, STAR preliminary results on charged-particle integral
and differential elliptic flow in Au+Au and Cu+Cu collisions at
$\sqrt{s_{NN}}$=200 and 62~GeV will be presented.
Flow fluctuations, their relation to fluctuations in the initial system
eccentricity, and $v_2/\varepsilon$ scaling (dependence of the elliptic flow on
the
initial system eccentricity and particle rapidity density) will be
discussed.
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28 |
Subhasis Chattopadhyay |
Oral
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Direct Photons, Dileptons and Vector Mesons |
sub@veccal.ernet.in |
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{\small \it Quark Matter 2006 Conf. - Nov. 14-20, 2006 - Shanghai
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\centerline{ {\bf Azimuthal $\gamma$-charged-hadron correlations in d+Au and p+p collisions }}
\centerline{{\bf from STAR at $\sqrt{s_{NN}}=200$ GeV}}
\vspace{12pt}
\centerline{ {\bf Subhasis Chattopadhyay } }
\vspace{4pt}
\centerline{ {\bf (for the STAR Collaboration)}}
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\centerline{Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata 700064;}
\vspace{12pt}
\centerline{\it email: sub@veccal.ernet.in}
\vspace{12pt}
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The study of $\gamma$+jet events provides unique information about the fragmentation of hard partons in the hot medium created in heavy ion
collisions. While parton-energy loss is expected to modify the fragmentation of quarks and gluons, photons escape without interacting.
\vspace{12pt}
\par
We present an analysis of azimuthal $\gamma$-hadron correlations using photons detected with the
Barrel Electromagnetic Calorimeter (BEMC) and charged hadrons with the Time Projection Chamber in STAR.
For the first time, we present a method to enrich the sample of direct photons using shower shape analysis
in the fine-grained Shower Maximum Detector. The near-side yield is used to further constrain the
contribution of isolated direct photons to the trigger sample.
\vspace{12pt}
\par
We discuss this separation in detail and extract the away-side yield for gamma-jet events in p+p and d+Au collisions at RHIC. An outlook for similar analyses in Cu+Cu and Au+Au events will also be presented.
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29 |
J.K.Nayak, J.Alam, B. Mohanty, P.Roy, A.K. Mazumde |
Oral
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Strangeness and Heavy Flavor Production |
jajati-quark@veccal.ernet.in |
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{\small \it Quark Matter 2006 Conf. - November 14-20, 2006 -
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\centerline{\bf
\large{$\phi$} Production at RHIC: Characterization of Coexistence Phase
}
\vspace{12pt}
\centerline{{\bf J. K. Nayak}$^{\rm a}$,{\bf J. Alam}$^{\rm a}$
{\bf B. Mohanty}$^{\rm a}$,{\bf P. Roy}$^{\rm b}$
and {\bf A.K. Dutt-Mazumder}$^{\rm b}$}
\vspace{12pt}
\centerline{$^{\rm a}$Variable Energy Cyclotron Centre,
} \centerline{1/AF, Bidhan Nagar Kolkata 700 064, India.
{\it
jajati-quark@veccal.ernet.in}}
\vspace{12pt}
\centerline{$^{\rm b}$ Saha Institute of Nuclear Physics,
Physics} \centerline{1/AF, Bidhan Nagar Kolkata 700 064, India
}
\vspace{12pt} \vspace{12pt}
The production of strangeness in ultra-relativistic heavy ion
collisions
has been considered. Assuming a first order phase transition,
the evolution of strange particles have been studied by using
Boltzmann equation. The results obtained have been
contrasted with the experimental data of the RHIC experiment
presented by the STAR collaboration. Data on $\phi$ at mid
rapidity for Au+Au collision at $\sqrt{s}$=200 GeV is used
to set a lower bound to the critical temperature of quark hadron
phase transition. The effective degrees of freedom that
characterizes the co-existing phase of quark gluon plasma and
hadrons has also been extracted.
\vspace{12pt}
%\parindent=0pt \textbf{References}
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30 |
Supriya Das for the STAR Collaboration |
Poster
|
Hadron Correlations and Fluctuations |
S.Das@gsi.de |
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{\small \it Quark Matter 2006 Conf. - November 14-20, 2006 -
Shanghai - P. R. China}
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\centerline{\bf Strangeness fluctuation at RHIC}
\vspace{12pt}
\centerline{ {\bf Supriya~Das}$^{\rm a},^{\rm b}$ for the STAR Collaboration}
\vspace{12pt}
\centerline{$^{\rm a}$Physics Group, Variable Energy Cyclotron Center} \centerline{1/AF, Bidhannagar, Kolkata - 700064, India, {\it
S.Das@gsi.de}}
\vspace{12pt}
\centerline{$^{\rm b}$Present Address: Gesellschaft f{\"u}r Schwerionenforschung mbH (GSI)} \centerline{Planck Str. 1, 64291 Darmstadt, Germany}
\vspace{12pt} \vspace{12pt}
We present here detailed investigations of the event by event fluctuation of $K/\pi$ ratio in
Au+Au collisions at all available energies at RHIC.
Variation of $K/\pi$ ratio as well as the event by event fluctuation in this ratio have been argued
to carry signals for the production of Quark Gluon Plasma (QGP). Moreover recent observations
of "horn" structure in the excitation function of the $K^+/\pi^+$ ratio [1] and fluctuations in $K/\pi$ ratio [2] at SPS are suggestive of a signal for possible phase transition.
\vspace{12pt}
The results from measurement of event by event fluctuation in $K/\pi$ ratio for Au+Au collisions at
$\sqrt{s_{NN}}$ = 62.4, 200 GeV have already been studied [3]. Here we extend
the analysis towards other collision energies available at RHIC.
Two independent methods have been used for extraction of dynamical fluctuation for the most central collisions at different collisions energies and to study the centrality dependence of the dynamical fluctuation , one based on comparing data with the mixed event reference using the variable $\sigma_{dynamic}$ as was used in SPS and other based on correlation measure using the variable $\nu_{dynamic}$ [4] respectively.
\vspace{12pt}
The excitation function and centrality dependence of the dynamical fluctuation at RHIC
energies will be presented. Comparison of results will be made with SPS and with various models.
\vspace{12pt}
\parindent=0pt \textbf{References}
[1] S.V.~Afanasiev {\it et al.} for NA49 Collaboration {\it Phys. Rev. Lett.} {\bf 86} 1965, 2001.
[2] G.~Roland for NA49 Collaboration {\it J. Phys.} G {\bf 30} S1381, 2004.
[3] S.~Das for STAR Collaboration {\it nucl-ex}/{\bf 0503023}, 2005.
[4] C.~Pruneau, S.~Gavin and S.~Voloshin {\it Phys. Rev.} C {\bf66} 044904, 2002.
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