“Study the Low Mass Dielectron Production in Relativistic Heavy-Ion Collisions at RHIC-STAR”

SUPPLEMENTARY PROPOSALTO

“THE EXPERIMENTAL STUDY OF THE PHASE STRUCTURE OF STRONGLY INTERACTING MATTER”

Grant: DE-FG02-88ER40412

Prepared by

Wei Xie

Department of PhysicsPurdue University

West Lafayette, Indiana 47907September, 2010

Project Proposal Period: January 1, 2011 – December 31, 2013

1

Table of Contents

1. INTRODUCTION.................................................................................................................................3

2. RESEARCH PLAN............................................................................................................................5

2.1. SUMMARY OF THE RESEARCH PLAN AND THE TIMELINE OF DELIVERING THE RESULTS.....52.2. MEASUREMENT OF DIELECTRON PRODUCTION IN 200 GEV AU+AU COLLISIONS........................52.3. MEASUREMENT OF DIELECTRON PRODUCTION IN 62.4 GEV ENERGY AU+AU COLLISIONS........92.4. MEASUREMENT OF DIELECTRON PRODUCTION IN 39 GEV ENERGY AU+AU COLLISIONS.........112.5. MEASUREMENT OF DIELECTRON PRODUCTION IN 200 GEV U+U COLLISIONS..........................132.6. MEASUREMENT OF DIELECTRON PRODUCTION IN P+P COLLISIONS............................................142.7. FUTURE PERSPECTIVE...............................................................................................................142.8. BUDGET REQUESTS......................................................................................................................15

3. CURRENT SUPPORT.......................................................................................................................16

4. EXISTING RESOURCES.................................................................................................................16

5. BIOGRAPHICAL SKETCHS...........................................................................................................17

6. STUDENTS.........................................................................................................................................19

8. LIST OF TALKS AND PUBLICATIONS............................................................................................19

8.1. INVITED TALKS IN THE CONFERENCE AND WORKSHOPS IN THE PAST THREE YEARS.........................198.2. LIST OF PUBLICATIONS IN REFERRED JOURNAL IN THE PAST THREE YEARS.............................20

REFERENCES.............................................................................................................................................27

2

1. INTRODUCTION

The objective of this proposal is to measure the enhancement of the dielectron production in the low mass region (mee < 1.2 GeV/c2) in heavy-ion collisions and find out where the enhancement starts to appear as a function of the collision energies using the STAR detector at the Relativistic Heavy Ion Collider (RHIC). Dielectron production is not affected by strong interaction and is therefore considered as an ideal probe to study the chiral symmetry restoration and the properties of the QCD medium during its spacetime evolution. The research will include measuring dielectron yield in Au+Au collisions at √snn=200 GeV and lower energies.

At high temperature (T > Tc, where Tc ~ 170MeV) or high energy density ( > 1GeV/fm3), quarks and gluons were expected to move around like a free gas and to no longer be confined inside the hadrons [1] because of the significantly weakened interactions among them due to the QCD “asymptotic freedom”. In analogy to the conventional plasma in atomic physic, this state of matter with deconfined quarks and gluons is named as the “Quark Gluon Plasma” (QGP). However, lots of evidences suggests that the medium created at RHIC has a ratio of shear viscosity over entropy close to the quantum limit and is therefore more like a “perfect fluid” with strong interactions among the constituents. The future RHIC physics programs will clearly focus on the detailed studies of the medium properties. Direct measurement of medium temperature and understanding chiral symmetry restoration are some of the important steps towards this direction. At around the same time when the phase transition from hadron gas to QGP happens, chiral asymmetry is expected to be restored as a result of the significant reduction of quark condensate masses [2] or broadening of the vector mass spectra with little shift of mass peak position [3]. All detailed studies require progress on theoretical modeling as well as the precision measurements from experiment using different probes. Dielectron is one of the ideal probes to carry on these studies. Compared to hadrons, electrons have little interaction with the medium and can therefore travel through the medium while keeping most of the original information untouched. This feature enables us to study the chiral symmetry restoration as well as the properties of the medium during space-time evolution of the system.

The most interesting electrons are the ones coming from the thermal radiation of the QGP as well as those from low mass vector meson decay. In the QGP phase, quark and antiquark in the thermalized medium can annihilate each other to produce thermal photons which carry the direct information of the medium initial temperature. Production of real photons is always accompanied by the production of virtual photons that subsequently decay into dielectrons. We can therefore derive the real photon yield through measuring the yield of virtual-photon-decay dielectrons according to d2 Y ee /dm2=2 α /3 π ∙ L(m)/m ∙ S(m, q) ∙d Y γ, where L (m )=√1−4 me

2/m2 ∙(1+2me2/m2), Yee

and Yγ are respectively the yield of dielectron and photons, me is the electron mass, m is the di-electron mass, α is the fine structure constant and s(m,q) is the ratio of virtual photon yield over that of real photons. Compared to the conventional method of measuring real photons, this method leads to much higher S/B at 1 < pT< 3 GeV/c where hadronic decay photon dominate [4]. Dielectrons decay from light vector mesons, especially ρ meson have long been considered as an ideal tool to study early stage of the medium and the chiral symmetry restoration. The dielectron from ρ meson decay comes

3

mainly from ππ annihilation [5] ( π+¿ π−¿→ρ →e+¿ e−¿¿¿¿ ¿), and is expected to dominate the low mass dielectron production. Because the ρ meson has a lifetime of ~1.3 fm/c, which is much shorter than that of the medium, we can study effect of the chiral symmetry restoration on the reconstructed mass peak position and width of ρ meson and compare with the prediction of different theoretical models.

Large enhancement of the low mass dilepton production in heavy-ion collisions was first discovered by the CERES [6] and HELIOS/3 [7] experiments at CERN SPS and was attributed mainly to the in-medium modification of the ρ meson production in the hadron gas as well as the regeneration of ρ meson from ππ annihilations [8]. This understanding was further strengthened by the new measurements from CERES [9], HADES [10] and especially the high precision measurements of dimuon production in In+In collisions at √snn= 20 GeV from NA60 [11]. NA60 results can be well described by the mechanism of broadened ρ meson from ππ annihilation in the hot and dense hadronic medium, with small contribution from the QGP thermal radiation [12]. At RHIC, with about ten times higher collision energy, the measurements of dielectron production in √snn=200 GeV Au+Au collision from PHENIX experiment shows a large enhancement [13] in the broad region of mee = 0.150.75 GeV/c2. Unlike the results from CERN SPS, this enhancement is consistent with the dielectron production from virtual direct photons [4] indicating the source of the enhancement is dominated by the QGP thermal radiation. The result, however, cannot be understood by any available theoretical models since the QGP thermal radiation is expected to dominate the region of 1.2<mee<2.9GeV/c2 instead of the low mass region [14]. It would be essential to have another independent measurement of this important observation to as a cross check. In the mean time, since the similar effect is not observed in CERN SPS measurements, it would be essential to find out when the enhancement starts to appear through the low energy scan program at RHIC.

We propose to study low mass dielectron production using the STAR detector at RHIC. Since the 2010 RHIC Au+Au run, STAR has completed the implementation of a Time-Of-Flight detector (TOF). TOF has excellent capability of electron identification at pT < 1.0 GeV/c. At pT > 1.0 GeV/c, together with STAR Time-Projection-Chamber (TPC), STAR Electromagnetic Calorimeter (EMC) can be used to identify electron very efficiently. We can therefore measure low mass dielectron production yield at both low and high pT. In the mean time, STAR has been carrying on the low energy scan program to search for the phase transition critical point. We can take this opportunity to study dielectron production in Au+Au collision between √snn=20 GeV and 200 GeV, with the goal to find out where the enhancement starts to appear. We expect that the outcome of these studies will provide crucial inputs to the understanding of QGP medium and the chiral symmetry restorations.

This research will be carried out by the two graduate students requested in this proposal, under the supervision of Wei Xie.

2. RESEARCH PLAN

4

2.1. Summary of the Research Plan and the Timeline of Delivering the Results

In year 2011 and 2012, we plan to recruit two students to work on measuring low mass dielectron production in 200 GeV and 62.4 GeV Au+Au collisions. Both datasets have already been collected by STAR during RHIC 2010 run. The analysis on 200 GeV data is to cross check the PHENIX discovery of the large enhancement in the low mass region, while the analysis on the data from 62.4 GeV collisions, which is in-between the CERN SPS energy (~20 GeV) and RHIC full energy, is the first step to figure out where the enhancement starts to appear as a function of collision energies. With the existing 200 GeV Au+Au dataset, we expect to observe the low mass dielectron enhancement in inclusive invariant mass spectrum and also quantify the enhancement up to pT = 0.5 GeV/c. With the 62.4 GeV Au+Au dataset, we will be able to provide a significant measurement at mee < 0.4GeV/c2 up to pT = 2.0 GeV/c. We plan to accomplish the two data analyses and publish the results in refereed journals in two years taking into account the training time of the students.

In year 2013, one student is expected to continue measuring dielectron production in 39 GeV Au+Au collisions. This will further narrow down the region where the dielectron enhancement starts to happen. The other student will measure dielectron production in 200 GeV U+U collisions. The 39 GeV datasets has already been collected in STAR in RHIC 2010 run. The RHIC Physics Advisory Committee (PAC) has recommended the 200 GeV U+U collisions in run 2012. In case the U+U program is not possible, the PAC recommends 7 weeks of Au+Au runs which provides higher luminosity than in run2010. In this case, the student will analyze the Au+Au data. With the existing 39 GeV Au+Au datasets, we expect a significant measurement at mee < 0.4GeV/c2 up to pT = 2.0 GeV/c. With the run 2012 U+U or Au+Au collisions, the measurement precision will be better than that of run 2010. We plan to accomplish both analyses and publish the results in about one and half years.

2.2. Measurement of Dielectron Production in 200 GeV Au+Au collisions

In RHIC run 2010, STAR collected 355 million minimum-bias events in 200 GeV Au+Au collisions. Using the HIJING event generator [15], we estimated the statistical significance of the dielectron production in the low mass region. The combinatorial background in the low mass region is dominated by dielectrons from π0, η, η’ Dalitz decays as well as the electrons from photon conversions which are not included in the HIJING simulation. Since the kinematics of electron pairs from photon conversion and π0

Dalitz decay is quite similar, we increase the π0 Dalitz decay branching ratio by a factor of 2.5 to take into account the material thickness in STAR tracking system. The other signals included in the simulation are ρ → e+¿ e−¿ ,ω →e+¿ e−¿ ,ϕ→ e+¿ e−¿¿¿¿ ¿¿¿and electron pairs from the correlated heavy flavor hadron and antihadron production ¿ ). We do not take into account the contribution from ω→ π0 e+¿ e−¿¿¿ and ϕ → ηe+¿e−¿ ¿¿ due to the limitation of the event generator. The electron identification efficiency is assumed to be 100% in all projections of this proposal.

5

Figure 1 upper panel shows the simulated invariant mass spectrum of e+e- pairs using 355 million minimum-bias 200 GeV Au+Au collisions generated from HIJING. The dielectron signal is represented as the red histogram. The spectra of opposite charge signs electron pairs (unlike-sign foreground) and combinatorial background are represented as the black and the blue histograms. The sources of signal from various hadron decays are also included as shown in the figures. The lower panel shows the significance of the dielectron signal as a function of the e+e- mass. At 0.15<mee<0.75 GeV /c2, we expect to have a measurement of significance of 7-15 with the existing dataset. This will

Figure 1: The upper panel shows the dielectron invariant mass spectrum in STAR detector acceptance from 300 million minimum-bias Au+Au collisions at √snn=200 GeV produced from HIJING event generator. Included in the panel are the unlike-sign foreground (back histogram), combinatorial background (blue histogram), dielectron signal (red histogram) and various sources of signals represented by different symbols described in the figure. The low panel shows the significance of the dielectron signal in different electron pair mass region. be further improved after taking into account of the large enhancement of the dielectron production in this mass region in data. Figure 2 upper-left panel shows the PHENIX measurements of the dielectron invariant mass spectrum in 200 GeV Au+Au collisions [13] together with the expectation from normal hadron decays (cocktail). The lower-left panel shows the ratio of the measured dielectron yields over the cocktail. The cocktail can describe the data very well in all mass range except that there is an enhancement of about a factor of 2-10 at 0.15<mee<0.75 GeV /c2 in data. Since the combinatorial

6

background is dominated by electrons from photon conversion and π0 Dalitz decay, the large enhancement will increase the projected signal significance in Figure 1 by a factor of 2-10. We should clearly see the signal enhancement in the inclusive dielectron spectrum using the 200 GeV Au+Au dataset collected at STAR.

The right panel of Figure 2 shows the PHENIX measurement of delectron invariant mass spectra in 200 GeV minimum bias Au + Au collisions in different dielectron pT

regions. The large enhancement appears in all pT up to 5GeV/c, beyond which the data is out of statistics. The projections of the similar measurements using STAR data are shown in Figure 3, where each panel presents the simulated dielectron invariant mass spectrum (upper) as well as the signal significance as a function of electron pair mass (lower) in different pT region in STAR detector acceptance from 300 million minimum-bias Au+Au collisions at √snn=200 GeV produced from HIJING event generator. At mee < 0.4GeV/c2, the projected signal significance at pT < 4 GeV/c are above 5.0. The large enhancement of data will boost the significance above 10. At mee > 0.4GeV/c2, the projected significance is smaller than 5.0 at pT > 2.0 GeV/c, making it difficult to obtain a conclusive measurement. At pT > 5GeV/c, the current dataset runs out of statistics.

Figure 2: The upper left panel shows the PHENIX measurement of dielectron invariant mass spectrum in PHENIX detector acceptance in minimum-bias Au+Au collisions at √snn=200 GeV . The cocktail spectra from the decays of light hadrons and correlated decays of charm, bottom and Drell-Yan are also included and are represented by different symbols described in the figure. The bottom panel shows the ratio of data over the cocktail spectra. The systematic uncertainties of the data are shown as boxes. The uncertainty of the cocktail spectrum is shown as band around one. The right panel shows the delectron invariant mass spectra in 200 GeV minimum bias Au + Au collisions in different pT ranges. The solid curves represent the cocktail spectrum, where the contribution from charm is calculated through pythia using the cross section from [16] scaled by Ncoll.

7

Figure 3: Each panel shows the dielectron invariant mass spectrum (upper) as well as the signal significance as a function of electron pair mass (lower) in different pT region in STAR detector acceptance from 300 million minimum-bias Au+Au collisions at √snn=200 GeV produced from HIJING event generator. The unlike-sign foreground and combinatorial background are represented as the black and blue histograms, respectively. The dielectron signal is represented as the red histogram. The pT regions are indicated in each panel.

8

2.3. Measurement of Dielectron Production in 62.4 GeV Energy Au+Au collisions

In RHIC run 2010, STAR also collected 140 million minimum-bias events in Au+Au collisions at √s=62.4 GeV . We estimated the statistical significance of the dielectron production in the low mass region using HIJING event generator following the same procedure as described in Sec.2.2.

Figure 4: The upper panel shows the dielectron invariant mass spectrum in STAR detector acceptance from 140 million minimum-bias Au+Au collisions at √snn=62.4 GeV produced from HIJING event generator. Included in the panel are the unlike-sign foreground (back histogram), combinatorial background (blue histogram), dielectron signal (red histogram) and various sources of signals represented by different symbols described in the figure. The low panel shows the significance of the dielectron signal in different electron pair mass region.

Figure 4 upper panel shows the simulated invariant mass spectrum of e+e- pairs using 140 million minimum-bias 62.4 GeV Au+Au collisions generated from HIJING. The dielectron signal is represented as the red histogram. The spectra of opposite charge signs electron pairs (unlike-sign foreground) and combinatorial background are represented as the black and the blue histograms. The sources of signal from various hadron decays are also included as shown in the figures. The lower panel shows the significance of the dielectron signal as a function of the e+e- mass. At 0.15<mee<0.75GeV /c2, we expect to have a measurement of significance of 3-10 with the existing dataset. This will be further improved if there is a enhancement of the low mass dielectron production at 62.4 GeV/c. In either case, we should be able to have a significant measurement on the enhancement at mee =0.2 0.4GeV/c.

The projections of the pT dependent dielectron spectrum using STAR data are shown in Figure 5, where each panel shows the simulated dielectron invariant mass spectrum (upper) as well as the signal significance as a function of electron pair mass (lower) in

9

different pT region in STAR detector acceptance from 140 million minimum-bias Au+Au collisions at √snn=62.4 GeV produced from HIJING event generator. At mee < 0.4GeV/c2, the projected signal significance at pT < 2.0 GeV/c are above 5.0. This can be further improved if the enhancement also appears in the 62.4 GeV Au+Au collisions. For example, in case the enhancement factor is two, the measurement will be 5 standard deviations above the cocktail. At mee > 0.4GeV/c2, the projected significance is smaller than 3.0 and it’s not likely to have a significant measurements.

Figure 5: Each panel shows the dielectron invariant mass spectrum (upper) as well as the signal significance as a function of electron pair mass (lower) in different pT region in STAR detector acceptance from 140 million minimum-bias Au+Au collisions at √snn=62.4 GeV produced from HIJING event generator. The unlike-sign foreground and combinatorial background are represented as the black and blue histograms, respectively. The dielectron signal is represented as the red histogram. The pT regions are indicated in each panel.

10

2.4. Measurement of Dielectron Production in 39 GeV Energy Au+Au collisions

In RHIC run 2010, STAR also collected 250 million minimum-bias events in Au+Au collisions at √s=39 GeV . We estimated the statistical significance of the dielectron production in the low mass region using the HIJING event generator following the same procedure as described in Sec.2.2.

Figure 6: The upper panel shows the dielectron invariant mass spectrum in STAR detector acceptance from 250 million minimum-bias Au+Au collisions at √snn=39 GeV produced from HIJING event generator. Included in the panel are the unlike-sign foreground (back histogram), combinatorial background (blue histogram), dielectron signal (red histogram) and various sources of signals represented by different symbols described in the figure. The low panel shows the significance of the dielectron signal in different electron pair mass region.

Figure 6 upper panel shows the simulated invariant mass spectrum of e+e- pairs using 250 million minimum-bias 39 GeV Au+Au collisions generated from HIJING. The dielectron signal is represented as the red histogram. The spectra of opposite charge signs electron pairs (unlike-sign foreground) and combinatorial background are represented as the black and the blue histograms. The sources of signal from various hadron decays are also included as shown in the figures. The lower panel shows the significance of the dielectron signal as a function of the e+e- mass. At 0.15<mee<0.75 GeV /c2, we expect to have a measurement of significance of 5-13 with the existing dataset. Therefore, whether there is a enhancement of low mass dielectron or not, we should be able to have a significant measurement in the low mass region.

11

The projections of the pT dependent dielectron spectrum using STAR data are shown in Figure 7, where each panel shows the simulated dielectron invariant mass spectrum (upper) as well as the signal significance as a function of electron pair mass (lower) in different pT region in STAR detector acceptance from 300 million minimum-bias Au+Au collisions at √snn=39 GeV produced from HIJING event generator. The situation is similar as in 62.4 GeV measurements, i.e. at mee < 0.4GeV/c2, the projected signal significance at pT < 2.0 GeV/c are above 5.0. At mee > 0.4GeV/c2, the projected significance is smaller than 3.0, making it difficult to provide a significant measurement.

Figure 7: Each panel shows the dielectron invariant mass spectrum (upper) as well as the signal significance as a function of electron pair mass (lower) in different pT region in STAR detector acceptance from 250 million minimum-bias Au+Au collisions at √snn=39 GeV produced from HIJING event generator. The unlike-sign foreground and combinatorial background are

12

represented as the black and blue histograms, respectively. The dielectron signal is represented as the red histogram. The pT regions are indicated in each panel.2.5. Measurement of Dielectron Production in 200 GeV U+U collisions

The current recommendation from RHIC PAC is that in run 2012, RHIC will run 200 GeV U+U or Au+Au collisions for 7 weeks. Compared to the gold nucleus, Uranium nucleus has a larger A value and a prolate shape. This will enable RHIC to produce a matter with higher densities through U+U collisions than that from Au+Au collisions. Figure 8 shows the energy density (ε0) as a function of the centrality [17] in Au+Au and U+U collisions. The peak energy density in U+U collisions will be 62% higher than that of Au+Au. It would be very interesting how the low dielectron changes with higher energy density. If the enhancement is indeed coming from the QGP thermal radiation, we expect a measurement of higher temperature from low mass dielectrons.

Figure 8: Energy density (ε0) in full-overlap U+U collisions and in different centrality of Au+Au collisions.

In run 2012, the current projection of the weekly integrated luminosity in U+U collisions from RHIC Collider-Accelerator department is 400-1250 μb-1/week. In one 7-week run, the delivered luminosity will be 2-8 nb-1, which is ~1.5-6 time higher than that of the Au+Au collisions in 2010. We therefore expect a very good dielectron measurement in U+U collisions from run 2012.

In case RHIC decide to run Au+Au collisions, the projection on the weekly delivered luminosity is 650-1300 μb-1/week. In a 7-week run, RHIC will deliver 2-5nb-1 of Au+Au

13

collision which is 1.5-4.0 times better than that of run2010. This will enable us to measure the low mass dielectron in Au+Au collisions with better accuracy.

2.6. Measurement of Dielectron Production in p+p collisions To quantify the dielectron enhancement in Au+Au collision, we need to do the same

measurements in p+p collisions as a reference to make sure our calculation of cocktail is correct. Figure 9 shows the STAR measurement of dielectron invariant mass spectrum in 200 GeV p+p collisions using data from run 2009 [18]. The result is from 107 million minimum-bias p+p collisions and can be further improve by analyzing all 300 million minimum-bias events accumulated in the run. We can clearly see ω and ϕ signals, except that the accuracy at 0.3 < mee < 0.75 GeV/c2 need much improvements. There is no long p+p runs in 200 GeV, 62.4 GeV and 39 GeV before run 2012 from the PAC recommendation. However, if our results show that long p+p runs in different collisions energies are essential, we will put forward our request to the PAC through the collaboration management.

Figure 9: dielectron invariant mass spectrum in STAR detector acceptance from 107 million minimum-bias p+p collisions at √snn=200 GeV

2.7. Future Perspective

In run 2014, STAR will accomplish the Heavy Flavor Tracker (HFT) [19] silicon vertex detector. We will then be able to reject photon conversions outside of beam-pipe by requiring electron tracks to consist of hits from all silicon layers. This will significantly reduce the combinatorial background and therefore increase the signal significance in the low mass dielectron measurements. In the mean time, the HFT will

STAR Preliminary

14

enable us to directly measure electron pairs from the c c /b b which is the main background to measure the QGP thermal radiation at the intermediate mass region (1.2 < mee < 2.9 GeV/c2), which will be our next focus of study.2.8. Budget Requests

The total budget request from this supplementary proposal for 3 years including Purdue University indirect charges is $207,183.74

We request two students in this proposal. The University will cost share one graduate student throughout the three-year duration of this project. The requested funding is planned to cover the following costs in 3 years: Salaries and wages of one of the two requested students. Travel cost for the two requested students Computer purchase for the two requested students.

Salary & Graduate fee remissions: $105,289.89 The cost for one student for 3 years including salary, Graduate fee remissions and employee benefits is $105,289.89

Travel: $36K The two students are expected to attend STAR collaboration meeting and analysis

meeting. These meetings discuss details of the data analysis and STAR collaboration issues and are very beneficial to students. There are usually two collaboration meetings and two analysis meetings each year. Each trip will cost $1000. Each student will attend two of these meetings each year. In 3 years, the total cost for the two students is $1000 X 2 trips X 2 students X 3 year = $12 K

Each student will take one shift during RHIC option each year. Each trip will cost $1000. In 3 years, the total cost is $1000 X 2 students X 3 year = $6 K.

Starting from the second year, each student is expected to attend one domestic workshop every year. Each trip will cost $2000. So the total cost is $2000 X 2 students X 2 year = $8 K.

Each student is expected to attend one Quark Matter International conference during the 3 years. Each trip will cost $5000 including the collaboration meeting right before the conference. The total cost is $5000 X 2 = $10 K.

The total travel request in the 3 years is $36K including $26K for domestic and $10K for international travel.

Equipment: $4KEach student need one computer which costs $2000. The total cost is $2000 X 2 students = $4K.

University indirect costs: $61,893.85

15

3. CURRENT SUPPORT

The current support is used to support two students to study heavy quark production at RHIC.

The title of the support is

“THE EXPERIMENTAL STUDY OF THE PHASE STRUCTURE OF HADRONIC MATTER”

January 1, 2009 – December 31, 2011

Department Of Energy (DOE), Grant: DE-FG02-88ER40412

PI: Rolf Scharenberg, Co-PI’s: Andrew Hirsch, Fuqiang Wang, Wei Xie

4. EXISTING RESOURCES The proposed analysis will be carried on mainly in the RHIC Computing Facilities.

The Purdue PC farm will also be used. Our share of the farm consists of 8 dual-CPU nodes (total of 16 CPUs) and disk storage of about 2 TB. Each dual-CPU node consists of Dual 1.5 GHz Athlon processors, 1 GB of memory, Gigabit Ethernet, a 20 GB local hard disk, and a 73 GB SCSI hard disk which is integrated in RAID for large-scale disk storage. The storage space is mainly provided by two SnapAppliance Guardian 4400 NAS Servers which serve as a cross-mounted storage device. The PC-farm is supported by the IT group funded by the Physics Department .

16

5. BIOGRAPHICAL SKETCHS

Name

Wei Xie, Assistant Professor of Physics Department, Purdue University, West Lafayette.

Education

B.S., Physics 1991, Shangdong University, Jinan, Shandong, P.R. China M.S., High Energy Physics 1994, Shangdong University, Jinan, Shandong, P.R.

China Ph.D., High Energy Physics 1997, Institute of High Energy Physics, Academia

Sinica, Beijing, P.R. China

Professional Experience

Assistant Professor, Purdue University Dept. of Physics (2007-Present) Riken-BNL Fellow, Riken-BNL Research Center, BNL (2004-2007) Assistant Physicist, UC Riverside (2004-2004) Postdoctoral Research Fellow, UC Riverside (2000-2004) Postdoctoral Research Fellow, Weizmann Institute of Science, Israel (1997-2000)

Professional Activities

Chairperson of the International Workshop on Heavy Quark Production in Heavy-ion Collisions, West Lafayette, IN, 01/04-01/06, 2011.

Member of STAR Decadal Plan Committee. (2010-present). Member of RHIC/AGS users Executive Committee (2010-present). Member of STAR taskforce on non-photonic electron measurements (2009-present). Committee member of Brookhaven National Lab review on the NSF funded PHENIX

muon trigger upgrade project (Oct. 2008). Session chair of Heavy Quark Workshop at LBNL (Nov. 2007). Member of STAR Heavy Flavor Silicon Detector Upgrade Project (2007-present) Project Manager of PHENIX Reaction Plane Detector (2005-2007) Co-convener of Heavy/Light Physics Working Group in PHENIX collaboration at

RHIC (2004-2007) NSF grant Senior Collaborator of PHENIX forward upgrade project (2004-2007) Co-organizer, Workshop on Heavy Flavor probes in studying the Hot/dense matter

created at RHIC , Brookhaven National Lab (2005) Member, STAR Collaboration at RHIC(2007-present) Member, PHENIX Collaboration at RHIC(1997-2007) Member, CERES Collaboration at CERN(1997-present)

17

Member, American Physical Society (2000-present) Member, Mt. Kanbala and Yang-ba-jing cosmic-ray experiment in Tibet, China

(1991-1997)

Awards and Honors

Co-PI of the Grant: DE-FG02-88ER40412 “THE EXPERIMENTAL STUDY OF THE PHASE STRUCTURE OF STRONGLY INTERACTING MATTER” submitted on October 2009, Proposal Period: January 1, 2009 – December 31, 2011

RIKEN/BNL Research Center Fellowship at Brookhaven National Lab (2004-2007) Feinberg Fellowship at Weizmann Institute of Science, Israel (1997-2000) Guang Hua Fellowship Award for outstanding undergraduate students in Shandong

University, P.R. China (1988)

Selected Publications in the Past Three Years

1. “Measurement of the Bottom contribution to non-photonic electron production in $p+p$ collisions at $\sqrt{s} $=200 GeV.”, M.M. Aggarwal et al. (STAR Collaboration) arXiv:1007.1200.

2. “$\Upsilon$ cross section in $p+p$ collisions at $\sqrt(s) = 200$ GeV”, M.M. Aggarwal et al. (STAR Collaboration) , Phys. Rev. D 82, 012004 (2010).

3. “Balance Functions from Au$+$Au, $d+$Au, and $p+p$ Collisions at $\sqrt{s_{NN}}$ = 200 GeV.”, M.M. Aggarwal et al. (STAR Collaboration) Phys.Rev.C82, 024905 (2010).

4. “Azimuthal Charged-Particle Correlations and Possible Local Strong Parity Violation”, B.I. Abelev et al. (STAR Collaboration) , Phys. Rev. Lett. 103, 251601 (2009).

5. “Long range rapidity correlations and jet production in high energy nuclear collisions.”, B.I. Abelev et al. (STAR Collaboration) , Phys. Rev. C 80, 064912 (2009).

6. “Measurement of D* Mesons in Jets from p+p Collisions at s**(1/2) = 200-GeV” B.I. Abelev et al. (STAR Collaboration) , Phys. Rev. D 79, 112006 (2009).

7. “Observation of Two-source Interference in the Photoproduction Reaction Au Au Au Au + rho0”, B.I. Abelev et al. (STAR Collaboration), Phys. Rev. Lett. 102, 112301 (2009).

8. “Charged hadron multiplicity fluctuations in Au+Au and Cu+Cu collisions from sqrt(s_NN) = 22.5 to 200 GeV”, A. Adare et al. Phys. Rev. C 78, 044902 (2008).

18

6. STUDENTS

Student Date EnteredGrad. School

Date Joined Group

Degree Program

Date Degree Awarded / (Expected)

Advisor

Xin Li Aug. 2006 Aug. 2007 Ph.D Aug. 2012 Wei XieM. Mustafa Aug. 2009 Jun. 2010 Ph.D Jun. 2014 Wei Xie

Both Xin Li and M. Mustafa are studying heavy quark production at RHIC and are supported by our existing DOE Grant: DE-FG02-88ER40412.

8. LIST OF TALKS AND PUBLICATIONS

8.1. Invited Talks in the Conference and Workshops in the past three years

1. “Measurement of Non-photonic Electron Production at RHIC”, invited seminar in Ohio State University, Physics Department, Columbus, OH, June 3rd, 2010

2. “STAR open Heavy Flavor Measurements”, invited talk at XVIII International Workshop on Deep- Inelastic Scattering and Related Subjects, April 2010. Florence, Italy

3. “Taskforce report on non-photonic electron issue”, invited talk at the STAR collaboration meeting plenary session, March 2010, Brookhaven national lab

4. “STAR heavy flavor measurements”, invited talk at the Strong interaction in the 21st century, Feb. 2010, Mumbai, India.

5. “non-photonic electron in p+p”, invited talk at the STAR Workshop on Non-photonic electron, May 2009, UCLA, LA

6. “B meson measurement using HFT silicon vertex detector”, invited talk at the HFT project collaboration meeting at LBNL, Sep 2008.

19

8.2. List of Publications in Referred Journal in the Past Three Years

20

21

22

23

24

25

26

REFERENCES

27

1[]. E. V. Shuryak, Physics Reports-Review Section of Physics Letters 61, 71 (1980).2[]. G. E. Brown and M. Rho, Phys. Rev. Lett. 66, 2720 (1991). 3[]. C. Gale et al., Nucl. Phys. B 357, 65 (1991); C. Gale et al.,Phys. Rev. D 49, 3338 (1994); R. Rapp et al., Nucl. Phys. A617, 472 (1997) ; R. Rapp et al., Eur. Phys. J. A 6, 415 (1999).4[]. A. Adare et al., (PHENIX Collaboration), Phys. Rev. Lett. 104, 132301 (2010)5[]. J. J. Sakurai, Currents and Mesons (University of Chicago Press, Chicago, USA, 1969), ISBN 978-0-226-73383-8.6[]. G. Agakichiev et al.(CERES Collaboration), Phys. Rev. Lett. 75, 1272 (1995).7[]. M. Masera, (HELIOS/3 Collaboration), Nucl. Phys. A590, 103c (1995).8[]. R. Rapp et al., Adv. Nucl. Phys. 25 (2000) 1; G. E. Brown et al., Phys. Rep. 363, 85 (2002),9[]. G. Agakichiev et al. (CERES Collaboration), Eur. Phy. J. C41, 475 (2005).10[]. G. Agakichiev et al. (HADES Collaboration), Phys. Rev. Lett. 98, 052302 (2007).11[]. R. Arnaldi et al.(NA60 Collaboration), Phys. Rev. Lett.100, 022302 (2008).12[]. H. V. Hees and R. Rapp, Phys. Rev. Lett. 97, 102301 (2006)13[]. A. Adare et al., (PHENIX Collaboration), Phys. Rev. C81, 034911 (2010).14[]. H. V. Hees, J. Phys. G 35, 104034 (2008); R. Rapp, private communication. 15[]. HIJING1.382, http://www-nsdth.lbl.gov/~xnwang/hijing/16[]. A. Adare et al. (PHENIX Collaboration), Phys. Rev. Lett. 97, 252002 (2006).17[]. U.W. Heinz and A.J. Kuhlman, Phys. Rev. Lett. 94, 132301 (2005).18[]. L. Ruan, presentation at the workshop on “Electromagnetic Probes of Strongly Interacting Matter” , ECT* Trento, Itlay, September 13-17, 2010.19[]. J. Bouchet for the STAR Collaboration, Nucl. Phys. A830, 636c-637c (2009); J. Kapitan for the STAR Collaboration, Eur. Phys. J. C 62, 217-221 (2009).