STAR Newsletter #74 September 2000
	Star Home Page				Editor: Howard Matis

Contents

1. Spokesman's Column
2. STAR Operations
3. Detectors and Subsystems
4. Period Coordinators Report
5. Physics Working Groups
6. People: Comings and Goings
7. Announcments
8. Employment Opportunities

Spokesman's Column (John Harris)

I wish to congratulate the entire collaboration on the successful completion of STAR's first heavy ion data-taking run at RHIC. We were fortunate that the detector components performed well (to the credit of the many who designed, constructed, installed, tested, and operated the detectors, all with much care), that RHIC "rose to the occasion" supplying sufficient luminosity (with credit due to the RHIC Operations Group) in the end to make the run a success, and that the weather cooperated for the most part until the last 10 days of the run (we will need those chillers next year!). In all, STAR took approximately 2.03 M triggers of which 1.52 M were good triggers, which is divided approximately into 844 K central (15% of geometrical cross section) and 761 K min bias. In the end, we have 331 K good events in the most central (5%) data set and 458 K good events in the min bias data set for physics analysis.

As most of you are aware, STAR is within a few days of submitting a paper on our results on elliptic flow for publication in Physical Review Letters. The main result of the paper is that the elliptic flow that we measure at RHIC is significantly larger than that measured at the lower energies of the AGS and SPS. This can be and will definitely be interpreted as the system being more thermalized at RHIC than previously observed. In fact, since our measured result approaches that predicted in hydrodynamical calculations (complete thermalization), the most central collisions may be completely thermalized. Since the flow signal is created and propagated during the early stages (first few fm/c), this is a very important and interesting result, which bodes well for future measurements on a system which may be thermalized at a very early stage. The analysis of data on elliptic flow and the writing of the paper was led by A. Poskanzer, R. Snellings, and S. Voloshin in STAR. The paper has been made public and is presently undergoing some changes in consultation with the appointed Godfather Committee for the paper in STAR, prior to submission.

I wish to relay some information to the collaboration on several of the items discussed in the STAR Council Meeting, held August 4 at BNL.

The interim report of the STAR Graduate Student Thesis Committee is being modified and will be made available again to the collaboration for comment.

The STAR Council accepted the report and recommendation of the STAR Photon Multiplicity Detector (PMD) Review Committee, chaired by H.G. Ritter, to approve the PMD for installation in STAR. Several issues raised in the review committee report will be addressed by the Indian groups proposing to construct the PMD, and the proposal will be modified to reflect these changes prior to STAR's submission of a PMD proposal to Brookhaven Laboratory. This approval is a major step. I wish to congratulate the Indian groups led by Y. Viyogi for the success of their proposal, and to thank the committee for its work.

The Council approved unanimously the proposal made by STAR management to appoint Howard Wieman as the STAR Head of Detector Development and to seek from BNL a detector staging and development laboratory.

After discussion in the collaboration meeting and after Council discussion of the draft Long Range Plan (LRP) Report for STAR, it was agreed that the Spokesman would convene a 1-day STAR meeting to discuss the LRP if necessary (see below).

The Council discussed and approved a proposal to hold a STAR Analysis Meeting at LBNL in the Fall (also see below).

The spokesman will appoint a committee to make a proposal to the Council on how to modify the STAR bylaws to specifically address the issue of appointment of the spokesperson.

The Junior Council members stated a few concerns: a) the move to Building 1005 poses a major concern with onsite transportation and safety (especially after dark); b) the cost of eating onsite at the cafeteria is extremely high for students; c) the diminished quality of RCF computer access, printers, copiers, and basic infrastructure in the STAR user areas at BNL; d) that everyone should keep in mind students and young postdocs for potential talks outside of STAR. Many on the Council took note, including STAR management and members from BNL, in hopes of trying to address some of the concerns.

The Council agreed to hold the next STAR Collaboration Meeting at the University of Texas in Austin on January 7 - 11, 2001.

The U. Nantes group informed the Council of its intent to propose to host a STAR collaboration meeting in Nantes, France, in April 2002, prior to Quark Matter 2002 (to be held in Nantes).

The Sao Paolo group expressed, for the second time at a Council Meeting, its interest and ability to host an inexpensive collaboration meeting in Brazil.

The STAR Long Range Plan Task Force, chaired by R. Bellwied, has been busy this summer with the formulation of a white paper for STAR to consider as our input into the Long Range Planning Process of NSAC. A status report was presented at the collaboration meeting (1 - 5 August). After additional discussions and feedback from STAR, the report will be available for comment and discussion within STAR by September 13. After collaboration feedback, if there are issues which require discussing, a special meeting of the collaboration will be called in the Fall to discuss the Long Range Plan of STAR.

There will be a STAR Physics Analysis Workshop at LBNL on November 15 - 19. LBNL will host the meeting and provide assistance for the stay in Berkeley of some students and postdocs (application for assistance will be via workshop web page). There will be presentations within STAR of the data analysis with associated discussions including physics. These will take place every morning with afternoons reserved for smaller working group discussions and work on issues. There will be a large number of computers available for use and connections to the net. On one day theorists will be invited to discuss physics with us. This would involve presentation of public STAR data to theorists with time for discussion. This will be interleaved with presentations from theorists on subjects relevant to understanding our data. A separate announcement will be made to STAR with details on registration, reservations, and the agenda.

STAR Operations (from Bill Christie)

Due to a very intense effort by a number of people in the Operations groups (sub-system managers, experts, support personnel, etc.), the staffing and running of shifts by collaboration members, and in the later part of the run Physics oversight by the period coordinators, STAR has successfully finished its first Physics run.

The intermittent availability of colliding beams from RHIC during June, July, and into August made completing the year one commissioning of the STAR detector a fairly arduous task; although one that was ultimately quite successful. We made great strides forward during the commissioning in understanding the inner workings of the various sub systems, as well as the interfaces between the sub systems. A few areas that required quite a bit of effort were the interface and timing issues between STAR and the RHIC collider, the various internal timing considerations for the trigger system, and finally the optimization of the Physics triggers for the year one data run.

In an effort to build on the solid foundation for STAR operations that was established during this first year's run, a meeting is being organized to assess in detail where things stand, lessons learned, and where to direct our efforts in preparing for the next Physics run. It looks like this meeting will be held here at BNL at the beginning of October. Final dates should be announced soon.

The latest schedule for the next RHIC running period is that it will start on about March 1st of 2001. From what I understand, the length of the run is a bit uncertain at this point, awaiting a final Congressional budget for FY2001. Unfortunately, at least from an operational perspective, we will be running during the summer again next year.

Detectors and Subsystems

FTPC (from Volker Eckardt)

Further tests were done with the first FTPC in the tent in the Assembly Hall. We observed and recorded cosmic ray particles and all 15 laser tracks . In spite of the reduced shielding, the noise is only in the range of 1 ADC count. With the gas system operating in purge mode and flowing one l/min, we have an oxygen level of 7 ppm. In the recirculation mode, this value rose a little. While we were doing these tests on the first FTPC, the second FTPC was completed and successfully tested at MPI. It will be prepared for the transport to BNL later this month.

TPC (from Blair Stringfellow)

The TPC ran extremely well during the summer run. We finished the run with all sectors still operating and all readout boards active. The only casualties were a few FEE's and the occasional anode trip. Anode wire loading remained low even for 56 X 56 bunches. There is some indication that the background in the chamber from beam-gas is higher than expected, which may cause space charge effects. This needs further study.

Thanks to the TPC operators who were responsible for maintaining our 100% uptime: Mike Anderson, Dan Cebra, Eric Hjort, Alexei Lebedev, Dick Majka, Jim Thomas, Howard Wieman and Geno Yamamoto. Thanks also to Dennis Reichhold for keeping slow controls going and to Leonid Kotchenda and Peter Kravtsov for designing a solid gas system (no alarms in 2 months!)

Level 3 (from Jens Sören Lange)

In the last few weeks, the level-3 (L3) trigger system, had a successful commissioning for real events. In the first stage, it has been equipped with 12 ALPHA DS-10 track finder CPUs.

Besides the L3 event display, which has been used for all data taking since June, two "real" trigger applications were tested, both vertex cuts, the vertices being extrapolated from online reconstructed TPC track helices.

xyz vertex cut for peripheral Au + Au for reject of cosmic events
For this trigger, at the same time an n_track < 100 cut was applied, in order to reject beam-gas interactions (total rejection factor ~20). With the L3 event display it was even possible to identify the first pomeron --> rho --> pi + pi candidates online. Congratulations to the peripheral group, it has been an exciting co-project.

z vertex cut for central collision
The STAR z collision point has a rather wide sigma = 70-90 cm, and it turned out that events with |z| > 60-75 xm are not used for micro DST's by several physics working groups. Therefore, in the last week of data taking, the period coordinator encouraged the usage of a L3 cut |z| < 80 cm for the beginning of every beam spill, when the rate is too high to write each central event (ZDC coincidence rates 75 Hz< R < 120 Hz). The rejection factor was 35-45%, thus providing an enrichment of "TPC-centered", RCF-written central events of a factor 1.5-1.8. Detailed checks (e.g. Pt slope) were done for short test runs, indicating no bias for later analysis.

Both L3 triggers were running stably for several 10.000 events, giving us confidence for operation of more complicated algorithms next year. In winter, the system will be upgraded, 24 more ALPHA CPUs have already been delivered. Moreover, plans for L3 integration of other sub detectors (besides TPC) are starting. A student just joined the group and will work on L3 cluster and track finding for SVT. Summarizing, the level-3 group is looking forward to the first physics triggers next year !

TOFp (from Bill Llope)

The construction of the TOFp tray, pVPD detectors, and rack components is proceeding on schedule. All components save the HVSys cells are in hand. The twelve FEE v.7 boards for the TOFp and pVPDs, plus four spares, are complete and have been successfully tested for resolution, cross-talk, and threshold sensitivity. The approximately five miles of TOFp/pVPD signal cable has all been cut to length, connectored, and tested for actual delay, pulse area attenuation, and rise-time attenuation. The individual lengths of the cables in the eight different length groups are precise to approximately ~50 ps, which is well better than necessary. The low voltage distribution system, remote threshold system, and thermocouple systems are nearly complete. A new feature of the thermocouple and threshold systems allows the insertion of the 3 demand and 3 actual FEE thresholds (1 for TOFp and 1 each for the pVPDs) into the TOFp data stream via the Kinetics 3516 A/D used for the thermocouple digitization. The development of the mechanical structures continues. The total material thickness of TOFp and the complexity of the mechanical structures inside the tray have been simplified via the replacement of specific bronze or SS fasteners with aluminum machine screws and aluminum to aluminum welds. The schedule calls for major construction during the month of September, local testing throughout October, and the arrival at BNL of the 3 detectors and the rack components on November 1, 2000.

Members of the TOFp DAQ team from China are arriving for extended visits to BNL. Office space in building 510 is being filled with the TOFp CAMAC crate, ADC and TDC modules, and the TOFp DAQ PC to allow the continued development of the TOF DAQ code.

On the offline software side, progress continues on two fronts. At Rice, work on the GSTAR geometry descriptions for the TOFp and pVPD is largely complete, and the attention has shifted to updating the detector response description ("/cts"). The latest pVPD description was provided to the PMD team to allow progress on open issues related to the integration of the PMD and pVPD detectors. At Kent State, the development of the 'maker' for TOFp data analyses is underway again after an August pause. The goal here is to implement the (updated) detector response package to allow the continued development of the code needed to extrapolate specific tracks and extract the velocity information following the various timing corrections. For any details, see http://mac8.rice.edu/~TOF/default.html.

Period Coordinator Reports

Tom Trainor (August 15 - 28)

Early in this period we encountered several timing problems, as reviewed in my interim report of August 21. These problems have been resolved either in RHIC or in STAR trigger/DAQ, and data taken since August 18 are unaffected. The reconstruction software is being slightly modified to repair affected data. The resulting impact to physics seems to be negligible.

At this point we have accumulated about 1.3M events, and we are about 40% of the way toward our goal for central(5%) and minbias events as stated in the beam-use document. It is likely that we will achieve about 70% of this goal in the remaining 7 days. A trigger has been successfully tested for the peripheral-collisions program, and the planned allotment of 5% of integrated luminosity should be available for this program over the next several days.

Gary Westfall (August 29 - September 5)

The Au +Au run officially ended at 8 am, Tuesday, September 5, 2000. The last Au beam was delivered at 6:06 PM on Monday, September 4, 2000. During the week we took the following data:

Trigger Type	kilo events
Central collisions (15%)	384.7
Minimum bias	356.7
Peripheral collisions	20.1

These data provided: 5% central events Good minimum bias events

Trigger Type	This Period (kilo events)	This Summer (kilo events)
5% central events	128.2	331
Good minimum bias events	214.0	458

During this week we instituted a level 3 trigger to suppress central events with event vertices outside +/- 80 cm. This trigger provided 50% more analyzable central events during the high luminosity portions of the fills, when we were bandwidth limited. I also have prepared a slide which summarizes the Summer run.

We successfully ran the peripheral collision physics trigger. We wrote 20k events to tape from 200k triggers. Preliminary analysis showed an invariant mass peak around the rho mass. We carried out a series of crucial checks including trigger tests and zero field running with data and lasers. We ran the STAR magnet at full field and completed cooling system adjustments early in the week. However, the high temperatures and dew points during the week prevented us from running the magnet for extended periods at full field. On Monday night the weather cleared and the magnet was brought up to full field and was held there for several hours. However there was no beam.

Physics Working Groups

People

	Coming Gene Van Buren, BNL Going Gene Van Buren, UCLA

Announcements

Employment Opportunities