Updates on RHIC Run 8 and Beyond
By Steve Vigdor
This week, I attempt to bring you up to date on several recent and planned events that bear on the science programs at RHIC and the AGS, and more generally on Nuclear and Particle Physics plans at BNL. These plans cover a broad range of exciting science, and our challenge going forward is in providing sufficient funding to realize a major fraction of these opportunities.
Conclusion of Run 8
The run ended, as planned, on March 12, 2008. The pp collision portion of the run – though drastically shortened to 3.4 physics production weeks in the wake of the FY08 Omnibus Funding Bill – was able finally to provide the integrated luminosity needed to meet what we set as the highest priority goal for the shortened run: collection of a robust baseline data set to compare with d+Au forward hadron production and correlations relevant to test predictions of the Color Glass Condensate. Reaching that goal required some tradeoff between bunch intensity and beam polarization, so that the figure of merit achieved for transverse polarization asymmetries was somewhat smaller than hoped. There was important progress on the β* squeeze needed to enhance pp luminosities, but not on operations at the new, near-integer tune proposed for future pp collisions. Thus, Runs 7 and 8 combined leave a number of critical science and beam development goals for the spin program undone, with the hope of accomplishing them in Run 9. Plans for improving pp performance will be discussed in depth, along with other machine topics, at the upcoming annual RHIC Retreat scheduled for March 31-April 2.
The last two days of Run 8 were devoted to a low-energy test of Au+Au collisions, needed to determine achievable luminosities in planning for a future low-energy scan in search of the QCD critical point. A previous attempt in 2007 to deliver collisions below injection energy had produced ambiguous results, but this time robust evidence for collisions was clearly obtained. At a center of mass energy √sNN = 9.2 GeV, the experiments were able to acquire data for tens of thousands of valid collision events. However, problems in one ring during the last few hours of the run prevented a meaningful test of collisions at the even more challenging energy of 5 GeV.
Overall, we were able to squeeze 19 weeks of cryo-operation out of the FY08 budget, and the run was quite successful. Machine availability exceeded our target of 80% throughout the run, and the secondary goal of 60% time in store was met during the latter portion of the run (and very nearly met earlier).
RHIC/AGS PAC Meeting
The PAC meeting to discuss planning for Run 9 and beyond is scheduled for May 8-9, 2008 at BNL. The deadline for submission of proposals is April 18. Run 9 is likely to be impacted seriously by an anticipated Continuing Resolution in this election year. We will not be able to launch the run early, as we did in FY08, because we will have no carry-forward funds from FY08 and monthly budgets at the FY08 level would not keep up with the anticipated costs of running. While the President’s Budget Request for FY09 has sufficient RHIC funding for 25 weeks of cryo-operation, it will be difficult to fit in that many weeks, given that we can’t anticipate starting before February 1, 2009 at the very earliest. I have thus asked the experiment spokespersons to present Beam Use Proposals aimed at 25 cryo-weeks, but with priorities for shorter runs delineated as clearly as possible.
I am also asking the spokespersons to provide their Collaboration’s priorities for beam species and energies over the coming 5 years, in light of their scientific priorities, anticipated upgrade schedules, likely luminosity evolution and worldwide competition. I will seek the PAC’s advice on an overall 5-year plan optimized to produce the greatest science impact from RHIC. In particular, we will need to decide which potential machine upgrades, beyond the stochastic cooling development already under way, we should push first to meet the lab’s science priorities. I have provided a strawperson 5-year run plan, the most recent version of which can be found in my Quark Matter 2008 talk on the “Status and Evolution of the RHIC Facility”, posted at: qm2008.bnl.gov.
We are continuing to give highest priority to the ongoing stochastic cooling development, in order to ensure that, even under less than optimal budgets, we attain RHIC-II-like luminosities for high-energy heavy-ion running by 2011 or (under bleaker funding scenarios) 2012. By reaching RHIC-II so much earlier than envisioned in the recently completed Nuclear Physics Long Range Plan, we open up opportunities for new initiatives aimed for the 2015-2020 time period. I encourage you to think creatively about detector and/or machine upgrades that could facilitate compelling new physics measurements on that time scale.
P5 Planning Process in High Energy Physics
As most of you know, the U.S. High Energy Physics community has been undergoing a painful and time-compressed re-evaluation of its own priorities and budget planning for a long-range plan. The process has been highlighted by a series of three meetings of the Particle Physics Project Prioritization Panel (P5), the most recent of which occurred at BNL March 6-8, 2008. The agendas and presentations for all three meetings are accessible from http://hepwww.physics.yale.edu/P5/. In particular, at the BNL meeting I presented the Brookhaven outlook for particle physics over the coming decade. Among a number of projects, I included two potential AGS experiments: an upgraded measurement of the muon anomalous magnetic moment, and a new storage ring search for an intrinsic electric dipole moment of the deuteron, the latter of which will be presented as a proposal at the upcoming PAC meeting. The coexistence at Brookhaven of forefront programs in particle, as well as nuclear, physics produces intellectual and technical cross-fertilization that benefits both programs.