2008 RHIC/AGS PAC Meeting
By Steve Vigdor
June 25, 2008
The RHIC/AGS Program Advisory Committee met at BNL on May 8-9, 2008 to consider Run 9 Beam Use Requests and five-year run plans from STAR and PHENIX, as well as a full proposal to mount a new storage ring experiment using polarized deuteron beams from the AGS to measure an intrinsic electric dipole moment of the deuteron with sensitivity at the 10-29 e.cm level. Because of budget uncertainties, I asked PAC to concentrate for RHIC on priority recommendations for FY2009 and FY2010 combined, and then separately for the FY2011-2013 period. Their considerations took into account judgments on scientific priority, detector and luminosity upgrade timelines, and worldwide competition in evaluating the proposals from the two RHIC experiments. I also asked for their evaluation of the updated RHIC Spin plan, which was not yet available as a document but was summarized in a presentation by Bernd Surrow of MIT.
The PAC Report is now released, and can be downloaded from the NPP website. Let me try to summarize the scheduling impact of the PAC recommendations, as I see them currently in light of budget expectations and the latest available information about upgrade timelines.
1) RHIC Run 9 is most likely to consist of a single-energy polarized proton run, with the energy to be determined by the timing of our receiving an FY09 budget. If we determine that we cannot begin Run 9 by March 1, 2009, then we would likely run 500 GeV p+p in the Spring, for about 5-6 production weeks. If we can start by March 1, then we would try to have a long 200 GeV p+p run with about 12 physics production weeks. It looks as though the current power contract for BNL will be extended for one year, reducing power costs from the assumptions we used in planning the FY09 budget. This may influence our judgment of when we can begin the Spring run. In the case of a 500 GeV run, it might allow time for an additional short measurement of a p+p reference set for Au+Au data already acquired at 22.4 GeV. In any case, the p+p run will afford an opportunity to work on beam polarization and luminosity, in addition to addressing RHIC Spin physics goals.
2) RHIC Run 10 would include the p+p energy we do not run during Spring 2009, as well as a full-energy Au+Au run. PAC placed the latter run, with the PHENIX HBD still installed, at high priority, in order to map the low-mass dilepton spectrum in greater detail than previous runs allowed. STAR should also reap considerable benefit from another long full-energy Au+Au run, now that the DAQ1000 and TOF upgrades should be essentially complete. I am assuming, if we run 500 GeV p+p in Run 9, that carry-forward funds from FY09 to FY10 will help to permit a sufficiently long Run 10 to do justice to both 200 GeV p+p and full-energy Au+Au.
3) While PAC is excited about the prospects of a critical point search at RHIC, they also emphasized the need for more detailed and better supported arguments regarding the philosophy and length of the low-energy runs. In particular, what signals would the measurements focus on, what statistical precision would be needed to go qualitatively beyond SPS measurements at similar energies, what is the optimal strategy in terms of number of energies probed in a first run, etc.? PAC would like to see such improved arguments, hopefully fueled by discussions at the INT Workshop planned for this summer, presented next year. At the present stage of the considerations, the PAC judged the low-energy scan to be less urgent than the full-energy run with HBD still installed. I consider it unlikely that RHIC operating budgets in FY09-10 would be sufficient to include more than the runs described in points (1) and (2) above in Runs 9 and 10. Therefore, in the table below I show the first low-energy scan to be scheduled for Run 11. On this time scale, it is not possible to have low-energy electron cooling implemented, so that low-energy Au+Au luminosities would be improved (hopefully, by a factor of ~2-3 over what is achievable with the present RHIC configuration) by implementing the capability to inject during a RHIC store to “top-off” the decaying stored luminosity.
4) A tentative schedule for the out-years, assuming budgets sufficient to run two beam species per year, is indicated in the table below. Obviously, we will revisit this schedule at subsequent PAC meetings and as operating budgets are clarified. But for now, it incorporates my best guesses about timelines of detector and machine upgrades. For example, I view Run 11 as, at best, an engineering run for the PHENIX VTX upgrade, which postpones a long full-energy Au+Au run emphasizing heavy flavor identification until Run 12. By Run 12, the full envisioned stochastic cooling upgrade (with one transverse plane per ring) should be installed, and luminosities should be enhanced by an additional factor of 4-5 over Run 7. It is conceivable that the STAR HFT prototype might be installed by then, although that project does not yet have CD-0 approval.
5) The table below also indicates a run schedule capable of meeting the various heavy-ion and spin DOE performance milestones, including those new ones presently under consideration by NSAC. This aspect of the plan is important for our upcoming S&T review. In this context, I have indicated a possible scenario even for 2014, though that is beyond the scope of the recent PAC presentations and considerations. I have also indicated for Run 14 some relevant accelerator improvement and R&D goals we have set for ourselves.
It will be a challenge for all of us to make the attached program happen on the indicated timeline, but if we succeed, RHIC’s scientific impact will remain very strong during this period when the LHC heavy-ion program is starting up.
Tentative RHIC Run Plan Following 2008 PAC Recommendations
(assumes 6-month CR in FY09, then FY10-14 budgets sufficient to support 2-species runs each year; incorporates best available information on detector upgrade schedules as of 6/20/08)
Colliding Beam Species/Energy
|2009||500 GeV p+p||Assuming ~April 1 start, about 5-6 physics weeks to commission collisions, work on polarization & luminosity and obtain first W production signal to meet RIKEN milestone|
|2010||200 GeV p+p||~12 physics weeks to complete 200 GeV ALL measurements – could be swapped with 500 GeV Run 9 if Run 9 can start by March 1, 2009; STAR DAQ1000 fully operational|
|200 GeV Au+Au||9-10 physics weeks with PHENIX HBD, STAR DAQ1000 & TOF permits low-mass dilepton response map and 1st collision test of transverse stochastic cooling (installed in one ring)|
|2011||Au+Au at assorted low E||1st energy scan for critical point search, using top-off mode for luminosity improvement – energies and focus signals to be decided; commission PHENIX VTX (at least prototype)|
|200 GeV U+U||1st U+U run with EBIS, to increase energy density coverage|
|2012||500 GeV p+p||1st long 500 GeV p+p run, with PHENIX muon trigger and STAR FGT upgrades, to reach ~100 pb-1 for substantial statistics on W production and ΔG measurements|
|200 GeV Au+Au||Long production run with full stochastic cooling upgrade implemented, PHENIX VTX and prototype STAR HFT installed; focus on RHIC-II science goals: heavy flavor, γ-jet, quarkonium, multi-particle correlations|
|2013||500 GeV p+p||Reach ~300 pb-1 to address 2013 DOE performance milestone on W production and sea antiquark polarizations|
|200 GeV Au+Au or 2nd low-E scan||To be determined by results from 1st low-E scan and 1st upgraded luminosity runs, progress on low-E electron cooling, and on installation/commissioning of PHENIX FVTX and NCC and full STAR HFT|
|2014||200 GeV Au+Au or 2nd low-E scan||Run option not chosen for 2013 run – low-E scan addresses 2015 DOE milestone on critical point, full-E run addresses 2014 (γ-jet) and 2016 (identified heavy flavor) milestones. Proof of principle test of coherent electron cooling.|
|200 GeV p+p||Address 2015 DOE performance milestone on transverse SSA for γ-jet; provide reference data for HI runs with new detector subsystems; test electron lenses for p+p beam-beam tune spread reduction|