Contents

1. Spokesman's Column
2. STAR Operations
3. STAR Software and Computing
4. Physics Working Groups
5. People: Service Jobs and more
6. Announcements, Papers and Notes
7. Ten Years Ago in STAR
8. Employment Opportunities

Spokesman's Column (Tim Hallman)

This month, despite snowy cold weather, STAR has made considerable progress on its goals for the d + Au run, both in accumulating statistics for min- bias events, and commissioning our high pt trigger.

Initial analysis of data taken with the high pt trigger (based on a high tower in the barrel calorimeter) looks very encouraging, and suggests this trigger improves our efficiency for acquiring high pt events by a very large factor. With stable running, we should be able to easily extend our pt range in a short period of time. Unfortunately, a short period may be what we have, as the lack of a budget in the U.S. Congress continues to cloud the prospects for completion of the run.

A first production analysis of d+Au data will begin shortly, and first physics results may be available by the time of the Collaboration meeting.

If the run continues, we can look forward to several other milestones, including a possible measurement of D mesons in d+Au events, and testing to develop level III software for a possible J/Psi trigger using information from the barrel electromagnetic calorimeter. We are very much looking forward to the data the FPD will provide on spin asymmetries and (potentially) the gluon distribution in the Au nucleus. Work is ongoing to utilize the prototype tray of MRPC TOF (TOFr) for important physics from the d+Au run. The STAR photon multiplicity detector is also being commissioned. The FTPC's are working very well, and first results on the difference in particle multiplicity in the d and Au directions should be available soon.

The Collaboration meeting is approaching soon, and there will be many exciting talks on new data, draft papers, and ongoing technical/construction work. One item that will be discussed is STAR's proposal to build a barrel TOF detector. The proposal is now finished, and can be found in the protected area at:

http://www.star.bnl.gov/protected/tof/proposal_newcontrib/wjl/TOF_021003.pdf

The proposal is being reviewed at present by an internal STAR committee chaired by Dick Majka. The committee will provide comments to the Advisory Board, and the Council which is expected to take a decision on the proposal at it meeting on February 26th. I encourage everyone to take a few moments to take a look at the proposal and discuss it with their institutional representative. I would also like to thank everyone who worked hard putting together this proposal on behalf of STAR. The additional PID this detector will provide will enable a number of key physics studies which are not possible otherwise.

Next month, STAR will have a large number of talks at the upcoming Strange Quark Matter meeting. The Collaboration meeting will provde a great opportunity to take a look at the many new and interesting results on strangeness production in STAR and see what will be presented at the Conference.

Status of STAR Commissioning for the FY03 d-Au physics run

Greetings from Long Island. As I write this newsletter contribution (Monday Feb. 10) it is snowing again on Long Island, adding to the ~ 6 inches of snow that we received last Friday.

As discussed in last month's Newsletter, we've been continuing the commissioning of some aspects of the STAR detector system in parallel with the ongoing accumulation of physics data. I don't have an up to the minute count of the min-bias data that we've collected so far, but I believe that we've accumulated about 13 million events. Just under 4 million of these events were taken with what is known as "Reversed full magnetic field", and just over 9 million were taken with "Full magnetic field". In our ongoing goal to roughly balance the event statistics between the two STAR magnetic field polarities, we just switched the polarity of the magnet back to "Reversed magnetic field" this morning.

For calibration/analysis purposes there were ~ 500,000 min bias events taken with the forward polarity field, at half field strength (i.e 0.25T) taken over the weekend. We'll accumulate a similar half field strength data set for the Reversed field polarity soon. The following detector subsystems are now typically in all of our physics data runs: TPC, FTPC, SVT, TOFr, TOFp, CTB, BBC, BEMC towers, BEMC SMAX, L3, and the ZDCs. Detector subsystems that are in the Engineering/Commissioning phase are the FPDs, the single ladder SSD, and the partial installation of the PMD. Les and crew have been continuing in their tuning and studies of the BBC detector sub system, and have started investigating the use of the BBC as a collision trigger. Indications so far are that the majority of events triggered by a BBC collision trigger are a subset of the events triggered with the ZDC East based trigger. Indications are also that the BBC collision trigger is less prone to triggering on beam related backgrounds than the ZDC East based trigger. After a bit more tuning it is anticipated that a Trigger Identifier for the BBC collision trigger will be added to the min-bias trigger configuration. An estimate is that this will happen within the next day or so. Once this has been done it will be important for off-line analysis to look at the data and provide some feedback on the yield of "good" events for each of the min-bias Trigger Identifiers. Based on this feedback the min-bias Trigger Configuration could be optimized to increase the "good" event yield.

During the last scheduled access to the experiments (Wednesday Jan. 29th) th ere was some new code loaded into the trigger to enable us to implement "prescales" in the STAR trigger system. There was a problem with a portion of the scaler system which was resolved by the trigger group during an access last Thursday (Feb. 6th). With these two additional features (prescales and scalers) operational we were able to setup and start testing a candidate "High Pt" trigger this past weekend. The test high pt trigger setup that we tried was configured to include both the min-bias trigger and a BEMC high tower trigger. The min-bias trigger was downscaled so that it would accept approximately 30 events per second. This results in a "live-time" for the trigger of something like 50 to 60% to select the high tower events. The high tower threshold was set at approximately 4.4 GeV equivalent Electromagnetic energy. With the luminosities that the collider was delivering during these tests, this high tower trigger generated approximately a 1 Hz event rate.

One of the many nice features that have been setup for this years runs is the accounting of the "trigger identifiers" that the Run Control program generates and passes off to the Run Browser data base. Using this information one can investigate not only the number of events in a run that satisfy the various Trigger Identifiers, but the overlap of the Trigger Identifiers (i.e. number of events that satisfy more than one Trigger Identifier) is also calculated and presented in the Run Browser. A quick and rough look that I took at the test events that were acquired with this test trigger early this past Saturday showed the following: For a subset of the test runs taken, there were 250,891 min-bias events written, 2710 High tower (.ge. ~4.4 GeV) events taken, and 32 events taken that satisfied both the min-bias (downscaled) and high tower Trigger Identifiers. This indicates that ~ 32/250,891 ( or ~13/100,000 min-bias events) satisfy the high tower trigger with a threshold of ~4.4 GeV.

One inference that one can draw from this quick look at the Trigger Identifiers is that we'll probably desire more overlap with our high tower triggers so that we have sufficient statistics to determine the relative cross section of our high tower trigger to our min-bias .trigger To address this issue we plan to try running a new test configuration where we include a lower high tower threshold (e.g. ~2.5 GeV) which is prescaled down by some appropriate factor, along with the min-bias and high tower (~4.4 GeV) trigger Identifiers. With the appropriate adjustments of the prescale factors, this should result in reasonable numbers of events that satisfy both the min-bias and lower high tower threshold conditions, as well as the lower and high tower trigger conditions, and allow us to determine the relative cross section of our high pt data set.

Once we finalize the parameters for this combined trigger configuration, it is anticiipated that we will run this configuration for the bulk of the remainder of this years physics run. This will allow us to accumulate our min-bias and high pt data samples in parallel. A key parameter that will have to be determined to best meet the collaboration's goals is what live time we want to run at. Increasing the live time will increase the effective integrated luminosity sampled by the high tower triggers, but will decrease the number of min-bias events ultimately collected. With the combined Trigger Configurations commissioning expected to be finished soon, efforts will start to ramp up on trigger studies. The highest priority trigger study will be to investigate the J/Psi trigger schemes that Thomas/Manuel/Tonko et al. have been working on. These trigger studies promise to be interesting, and I'm eager to see what they find. Greetings from Long Island, Bill Christie

Dear STAR Collaborators,

The past few months have been important for the Software & Computing group. But first, we would like to mention and thank the FTPC and EMC sub-system group and their respective Software coordinator.

• For the past few month, the FTPC Software group made outstanding progress on the calibration front and are mainly ready for a production pass. Other efforts are also being made on the embedding and more work on understanding the subtle effects of calibration (temperature gradient adjustment, Z vertex position puzzle) for a later refined production pass.

• The EMC sub-systems also went through several milestones with the release of the first version of an embedding code and making their data available in the common MicroDST by default.

We hope to soon hear from the SVT sub-system for similar good news and progress ...

A call for an official production has been made last week and we hope to be able to start soon with a first pass of data production including TPC and FTPC as the two ready-to-go detectors. Although our FastOffline system has been going through, to date, 90% of our data, we should not forget that being able to start a production pass has been made possible by the effort of many people. Amongst all, I would like to especially thank Lidia Didenko for carrying along several calibration and trigger tests mini-production passes which were necessary for a faster convergence. Also, I would like to thank the offline QA team whose work and identification of problems has made this convergence possible and all the period coordinators who have given regular updates at the weekly S&C meeting and brought to us their major issues and concerns.

The simulation front has seen several massive production passes all taking place at the RCF and at PDSF. First, we finished the first pass of d+Au simulation using the standard Hijing 1.35 and finishing a new pass of equivalent statistics using Hijing 3.82. The latest implements the Hulthen wave-function for the deuteron (a courtesy of Brian Cole of PHENIX). We would like to also mention that a production mode data transfer from PDSF o BNL was also tested and made available for the first time. This completes the true meaning of data safety and data replication. Back on simulation, work was also done in updating the geometry description and a re-assessment of the SVT material map initiated. In this regard, I would like to thank Ian Johnson for his unconditional support of our efforts to correct for this known simulation deficiency. His help and time was truly appreciated and we hope it will be noted.

The Integrated Tracking Task Force has made several progress on integrating the code to our main infrastructure. We hope to start a min-test production and be in a position to soon answer the awaited question : are we ready and when.

At last but not least, I would like to mention that our STAR/PPDG Grid effort has been recently re-enforced by three new members. I would like to thank Dave Stampf and his Information and Technology Division (ITD) group for granting me the time to explain our Grid interest and vision and by further trusting us by joining PPDG under the STAR banner. I am hoping we will all learn from this pilot program and go in the direction I firmly believe to be the right one : having ITD provide to all solutions and services and by doing so, increasing trust and communication between our respective Computing departments.

This month featuring the High Pt Group

The High pT Physics Working Group works on a wide range of problems connected to jet production and its use as a probe of the dense medium generated in heavy ion collisions. This topic originated about twenty years ago with Bjorken, who calculated the energy loss (dE/dx) via elastic scattering of a high energy parton passing through a dense region of free quarks and gluons. It turns out that dE/dx due to elastic scattering is too small to distinguish between hadronic matter and a Quark Gluon Plasma, but ten years ago Gyulassy and Pluemer realized that dE/dx due to gluon bremsstrahlung was a factor 10 larger than that due to elastic scattering, and that jet energy loss was indeed a valuable tool in the search for the QGP. Over the past decade there has been an explosion of interest in the problem, both from the theoretical and experimental sides, and it is presently one of the hot topics at RHIC.

STAR can address the jet quenching problem through a number of different observables. This broad-based approach is essential to establish the complete picture of jet production in heavy ion collisions. We have published three high pT papers so far, all accepted to PRL. The first, on 130 GeV data, reported the suppression of inclusive (leading) hadrons, the basic measurement that established the phenomenon. The second paper on 130 GeV data reported the observation of large and constant (vs pT) elliptic flow at high pT, which can arise in non-central collisions due to the different path lengths the jet propagates through, depending on its orientation relative to the reaction plane. This paper also showed the first high pT two-particle correlations, indicating that hadron production in the 2-4 GeV/c range largely comes from jet fragmentation even in the most complex heavy ion collisions. The third paper, on correlations from the 200 GeV Au+Au and p+p data, solidified this result and reported a spectacular new signal, the disappearance of the away-side jet in central collisions.

We currently have several papers in the works, both within High pT and in conjunction with other PWGs. A paper on the 200 GeV Au+Au and p+p inclusive spectra will extend the hadron suppression story to 12 GeV/c, well into the perturbative regime. An important aspect of this analysis is that the comparison of similar measurements taken with the same detector leads to a substantial reduction in many of the systematic uncertainties. This paper is in an advanced state of preparation and will be the benchmark observation for several years. There is another draft that is well along which will describe a measurement of the transverse energy in 200 GeV Au+Au collisions with the BEMC. Recent progress in the 4-particle cumulant analysis means that we can extend it to pT=7 GeV/c or so. A paper will be forthcoming, together with E-by-E, on elliptic flow at very high pT, a capability unique to STAR. Particle identified spectra at high pT is a very hot topic right now, and the High pT group is working with Strangeness and E-by-E to stir the pot where the beautiful new results on inclusive spectra and v2 of Lambdas and K0s are being cooked. Final analysis of RICH data is in progress and will also contribute to this physics.

There is a lot of discussion in the community about these and related results from PHENIX. A surprising development of the past few years is that all of the high pT observations we have made so far may not in fact be manifestations of jet quenching, but rather be due to large modifications of the gluon density at low x in heavy nuclei relative to that in protons, the so-called "saturation" picture. Resolving this central issue and firmly establishing whether or not final-state effects are generating what we see at high pT in Au+Au collisions is one of the main aims of the current d+Au run. The High pT PWG will analyze the d+Au data as soon as they become ready. The first two analyses we will carry out are the inclusive charged hadron spectrum to about 10 GeV (requiring perhaps 5 million minbias d+Au for a robust measurement), and the high pT two-particle correlation studies. We hope that, together, these two analyses will provide decisive evidence for or against the jet quenching picture. The next few months will be exciting!

People

	Service: Jerry's official page is here Jerome's own page in the computing area is here Other: STAR speakers: Recommended list from the Talks Committee can be found here

Announcements, Paper and Notes

Collaboration Meeting, Feb 25 - March 1, BNL

Details about this event can be found here

Publications:

The following papers have been recently published:

1. Azimuthal Anisotropy and Correlations in the Hard Scattering Regime at RHIC
   C. Adler et al. Phys. Rev. Lett. 90, 032301 (2003)
   [nucl-ex/0206006] Published: 24 January 2003