Abstracts, Presentations and Proceedings


This page is maintained by Gang Wang.


#9995# DNP (fall meeting) 2010

 Abstracts for DNP (fall meeting) 2010 (Nov. 2-6, 2010, Santa Fe, NM)

  • Wenqin Xu

Title: Extracting bottom quark production cross section from p+p collisions at RHIC


The STAR collaboration has measured the non-photonic electron (NPE) production at high transverse momentum (pT ) at middle rapidity in p + p collisions at sqrt(s) = 200 GeV at the Relativistic Heavy Ion Collider (RHIC). The relative contributions  of bottom and charm hadrons to NPE have also been obtained through electron hadron azimuthal 
correlation studies. Combining these two,  we are able to determine the high pT mid-rapidity electron spectra 
from bottom and charm decays, separately.

PYTHIA with different tunes and FONLL calculations have been compared  with this measured electron spectrum
from bottom decays to extract the bb-bar differential cross section after normalization to the measured spectrum.
The extrapolation of the total bb-bar production cross section in the whole kinematic range and its dependence
on spectrum shapes from model calculations will also be discussed.


  • Yifei Zhang

Title: Open charm hadron reconstruction via hadronic decays in p+p collisions at $sqrt{s}$ = 200 GeV

Heavy quarks are believed to be an ideal probe to study the properties of the QCD medium produced in the relativistic heavy ion collisions. Heavy quark production in elementary particle collisions is expected to be better calculated in the perturbative QCD. Precision understanding on both the charm production total cross section and the fragmentation in p+p collisions is a baseline to further explore the QCD medium via open charm and charmonium in heavy ion collisions.
Early RHIC measurements in p+p collisions which were carried out via semi-leptonic decay electrons provides limited knowledge on the heavy quark production due to the incomplete kinematics, the limited momentum coverage and the mixed contribution from various charm and bottom hadrons in the electron approach. In this talk, we will present
the reconstruction of open charm hadrons (D0 and D*) via the hadronic decays in p+p collisions at $sqrt{s}$ = 200 GeV in the STAR experiment. The analysis is based on the large p+p minimum bias sample collected in RHIC Run9. The Time-Of-Flight detector, which covered 72% of the whole barrel in Run9, was used to improve the decay daughter
identification. Physics implications from this analysis will be presented.

  • Xin Li

Title: Non-photonic Electron Measurements in 200 GeV p+p collisions at RHIC-STAR


Compared to the light quarks, heavy quarks are produced early in the collisions and interact very differently with the strongly couple QGP(sQGP) created at RHIC. In addition, their large masses are created mostly from the spontaneous symmetry breaking. All these features make heavy quark an ideal probe to study the sQGP. One of the critical references in these studies is the heavy quark production in p+p collisions, which also provides a crucial test to the pQCD. Measuring electrons from heavy quark semi-leptonic decay (non-photonic electron) is one of the major approaches to study heavy quark production at RHIC.

We will present STAR measurements on the mid-rapidity non-photonic electron production at pT>2 GeV/c in 200 GeV p+p collisions using the datasets from the 2008 and 2005 runs, which have dramatically different photonic backgrounds. We will compare our measurements with the published results at RHIC and also report the status of the analysis at pT<2 GeV/c using the dataset from the 2009 run.

  • Jonathan Bouchet

Title: Reconstruction of charmed decays using microvertexing techniques with the STAR Silicon Detectors

Due to their production at the early stages, heavy flavor particles are of interest to study the properties of the matter created in heavy ion collisions. Direct topological reconstruction of $D$ and $B$ mesons, as opposed to indirect methods using semi-leptonic decay channels [1], provides a precise measurement and thus disentangles the $b$ and $c$ quarks contributions [2].

In this talk we present a microvertexing technique used in the reconstruction of $D^{0}$ decay vertex ($D^{0} \rightarrow K^{-}\pi^{+}$) and its charge conjugate. The significant combinatorial background can be reduced by means of
secondary vertex reconstruction and other track cut variables. Results of this method using the silicon detector information of the STAR experiment at RHIC will be presented for the Au+Au system at $\sqrt{s_{NN}}$ = 200 GeV.

[1]A. Abelev et al., Phys. Rev. Lett. {\bf 98} (2007) 192301
[2]N. Armesto et al., Phys. Lett. B{\bf 637} (2006) 362-366.



#9996# Hard Probe 2010

 Abstracts for 2010 Hard Probe Meeting (Oct. 10-15, 2010, Eilat, Israel)


  •  Wei Xie
Title: Heavy flavor production and heavy flavor induced correlations at RHIC


Heavy quarks are unique probes to study the strongly coupled Quark-Gluon Plasma created at RHIC. Unlike light quarks, heavy quark masses come mostly from spontaneous symmetry breaking, which makes them ideal for studying the medium's QCD properties. Due to their large masses, they are produced early in the collisions and are expected to interact with the medium quite differently from that of light quarks. Detailed studies on the production of open heavy flavor mesons and heavy quarkonium in heavy-ion collisions and the baseline $p+p$ and $d+A$ collisions provide crucial information in understanding the medium's properties. With the large acceptance TPC, Time of Flight, EM Calorimeter and future Heavy-Flavor Tracker, STAR has the capabilities to study heavy quark production in the dense medium in all different directions. In this talk, we will review the current status as well as the future perspectives of heavy quark studies in STAR experiment.


  • Zebo Tang

Title: $J/\psi$ production at high pT at STAR




The $c\bar{c}$ bound state $J/\psi$ provides a unique tool to probe the hot dense medium produced in heavy-ion collisions, but to date its production mechanism is not understood clearly neither in heavy-ion collisions nor in hadron hadron collisions. Measurement of $J/\psi$ production at high $p_T$ is particularly interesting since at high $p_T$
the various models give different predictions. More over some model calculations on $J/\psi$ production are only applicable at intermediate/high $p_T$. Besides, high $p_T$ particles are widely used to study the parton-medium interactions in heavy-ion collisions. In this talk, we will present the measurement of mid-rapidity (|y|<1) $J/\psi \rightarrow
e^+e^-$ production at high $p_T$ in p+p and Cu+Cu collisions at 200 GeV, that used a trigger on electron energy deposited in Electromagnetic Calorimeter. The $J/\psi$ $p_T$ spectra and nuclear modification factors will be compared to model calculations to understand its production mechanism and medium modifications. The $J/\psi$-hadron azimuthal angle correlation will be presented to disentangle $B$-mesons contributions to inclusive $J/\psi$. Progresses
from on-going analyses in p+p collisions at 200GeV taken in year 2009 high luminosity run will be also reported.


  • Rosi Reed

Title: $\Upsilon$ production in p+p, d+Au, Au+Au collisions at $\sqrt{{S}_{NN }} = $ 200 GeV in STAR

Quarkonia is a good probe of the dense matter produced in heavy-ion collisions at RHIC because it is produced early in the collision and the production is theorized to be suppressed due to the Debye color screening of the potential between the heavy quarks. A model dependent measurement of the temperature of the Quark Gluon Plasma (QGP) can be determined by examining the ratio of the production of various quarkonia states in heavy ion collisions versus p+p collisions because lattice calculations indicate that the quarkonia states will be sequentially suppressed. Suppression is quantified by calculating ${R}_{AA}$, which is the ratio of the production in p+p scaled by the number of binary collisions to the production in Au+Au. The $\Upsilon$ states are of particular interest because at 200 GeV the effects of feed down and co-movers are smaller than for J/$\psi$, which decreases the systematic uncertainty of the ${R}_{AA} calculation. In addition to hadronic absorption, additional cold nuclear matter effects, such as shadowing of the PDFs, can be determined from d+Au collisions. We will present our results for mid-rapidity $\Upsilon$ production in p+p, as well as our preliminary results in d+Au and Au+Au at $\sqrt{{S}_{NN }}$ = 200 GeV. These results will then be compared with theoretical QCD calculations.

  • Wei Li

Title: Non$-$Photonic Electron and Charged Hadron Azimuthal Correlation in 500 GeV p+p Collisionsions at RHIC


Due to the dead cone effect, heavy quarks were expected to lose less energy than light quarks since the current theory predicted that the dominant energy loss mechanism is gluon radiation for heavy quarks.  Whereas non-photonic electron from heavy quark decays show similar suppression as light hadrons at high $p_{T}$ in central Au+Au collisions.  It is important to separate the bottom contribution to non-photonic electron for the better understanding of heavy flavor
production and energy loss mechanism in ultra high energy heavy ion collisions. B decay contribution is approximately 50$\%$ at a transverse momentum of $p_{T}$$\geq$5 GeV/c in 200 GeV p+p collisions from STAR results. In this talk, we will present the azimuthal correlation analysis of non-photonic electrons with charged hadrons at $p_{T}$$\geq$6.5 GeV/c in p+p collisions at $\sqrt{s}$  = 500 GeV at RHIC. The results are compared to PYTHIA simulations to disentangle
charm and bottom contribution of semi-leptonic decays to non-photonic electrons.



  • Gang Wang

Title: B/D Contribution to Non-Photonic Electrons and Status of Non-Photonic Electron $v_2$ at RHIC

In contrast to the expectations due to the dead cone effect, non-photonic electrons from decays of heavy quark carrying hadrons show a similar suppression as light hadrons at high $p_{T}$ in central 200 GeV Au+Au collisions at RHIC. It is important to separate the charm and bottom contributions to non-photonic electrons to better understand the heavy flavor production and energy loss mechanism in high energy heavy ion collisions. Heavy quark energy loss and heavy quark evolution in the QCD medium can also lead to an elliptic flow $v_2$ of heavy quarks which can be studied through $v_2$ of non-photonic electrons.


In this talk, we present the azimuthal correlation analysis of non-photonic electrons with charged hadrons at 1.5 GeV/c < $p_{T}$ < 9.5 GeV/c in p+p collisions at $\sqrt{s}$ = 200 GeV at RHIC, with the removal of J/$\Psi$ contribution to non-photonic electrons. The results are compared with PYTHIA simulations to disentangle charm and bottom contributions of semi-leptonic decays to non-photonic electrons. B decay contribution is approximately 50$\%$ at the electron transverse momentum of $p_{T}$ > 5 GeV/c in 200 GeV p+p collisions from STAR results. Incorporating the spectra and energy loss information of non-photonic electrons, we further estimate the spectra and energy loss of the electrons from B/D decays. Status of $v_2$ measurements for non-photonic electrons will also be discussed for 200 GeV Au+Au collisions with RHIC run2007 data.



#9997# APS 2010 April Meeting

 Abstracts for 2010 APS April Meeting (Feb. 13-17, 2010, Washington DC)

  • Jonathan Bouchet

Title: Performance studies of the Silicon Detectors in STAR towards microvertexing of rare decays

Abstract: Heavy quarks production ($b$ and $c$) as well as their elliptic flow can be used as a probe of the thermalization of the medium created in heavy ions collisions. Direct topological reconstruction of charmed and bottom decays is then needed to obtain this precise measurement. To achieve this goal the silicon detectors of the STAR experiment are explored. These detectors, a Silicon Drift (SVT) 3-layer detector[1] and a Silicon Strip one-layer detector[2] provide tracking very near to the beam axis and allow us to search for heavy flavour with microvertexing methods. $D^{0}$ meson reconstruction including the silicon detectors in the tracking algorithm will be presented for the Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, and physics opportunities will be discussed.

[1]R. Bellwied et al., Nucl. Inst. Methods A499 (2003) 640.

[2]L. Arnold et al., Nucl. Inst. and Methods A499 (2003) 652.


  • Matt Cervantes

Title: Upsilon + Hadron correlations at the Relativistic Heavy-Ion Collider (RHIC)

Abstract: STAR has the capability to reconstruct the heavy quarkonium states of both the J/Psi and Upsilon particles produced by the collisions at the Relativistic Heavy Ion Collider (RHIC).  The systematics of prompt production of heavy quarkonium is not fully described by current models, e.g. the Color Singlet Model (CSM) and the Color Octect Model.  Hadronic activity directly around the heavy quarkonium has been proposed [1] as an experimental observable to measure the radiation emitted off the coloured heavy quark pair during production.  Possible insight into the prompt production mechanism of heavy quarkonium can be obtained from this measured activity.  Using STAR data from dAu collisions at sqrt(s_NN)= 200 GeV, the high S/B ratio found in Upsilon reconstruction [2] can enable us to perform an analysis of Upsilon + Hadron correlations.  We will present our initial investigation of such an analysis.

[1] Kraan, A. C., arXiv:0807.3123.

[2] Liu, H., STAR Collaboration, arXiv:0907.4538.

PWG convener to press the approval button

 On this page, we collect the information about which PWG convener to press the final approval button for which conference.  

Conference Convener
2018 Hot Quarks Rongrong Ma
2018 Hard Probes Petr Chaloupka
2018 EJC Petr Chaloupka
2018 ATHIC Zebo Tang
2018 Zimanyi School Petr Chaloupka
2019 Bormio Rongrong Ma
2019 IIT Indore Zebo Tang
2019 QCD Moriond Petr Chaloupka
2019 APS April Meeting Sooraj Radhakrishnan
2019 QWG Zebo Tang
2019 FAIRness Zebo Tang
2019 SQM Petr Chaloupka
2019 AUM Sooraj Radhakrishnan


This page is maintained by Gang Wang.

#9997# WWND2010

Jan 2-9, 2010 Winter Workshop on Nuclear Dynamics (Ocho Rios, Jamaica)



#9999# SQM 2009 meeting

 Sept. 27-Oct. 2, 2009 SQM 2009 meeting (Buzios, Brazil)