By Steve Vigdor
As most of you are aware, there is currently a Subpanel of NSAC, chaired by Bob Tribble, which is charged to make recommendations aimed to “optimize the overall nuclear science program over the next five years (FY 2014-2018)” under funding scenarios far more constrained than those assumed in the 2007 Long Range Plan. It is unlikely that the funding scenarios in the charge could support operations at RHIC and at CEBAF in parallel with construction of FRIB, leading to a very challenging dilemma for the U.S. nuclear science community. In preparation for the considerations by this Subpanel, we have written a White Paper presenting the case for continuing operations of RHIC, emphasizing the facility’s past successes, the vision for its compelling future science program, its clear complementarity to the heavy-ion collision program at LHC, and its importance to the U.S. nuclear science program by virtue of scientific impact, Ph.D.’s produced and faculty positions created worldwide. This document is available at www.bnl.gov/npp. Many of you have already provided invaluable feedback during the process of getting to the current version, and there will be another opportunity for further feedback at a Town Meeting on Oct. 25 at the Newport Beach DNP meeting.
The Tribble Subpanel held open hearings on Sept. 7-9 in Rockville, Maryland. There was a series of presentations on relativistic heavy ion physics the morning of Sept. 7, begun by an overview talk from Bill Zajc. Talks on RHIC were presented by Sam Aronson, Steve Vigdor, Urs Wiedemann, Paul Sorensen and Yasuyuki Akiba. We will soon be posting copies of the slides presented on the same npp website (above link) as the White Paper. The essence of the case we have made is summarized in the opening paragraph of the RHIC White Paper: “RHIC is in its prime: it is poised to address a host of compelling science questions that remain or have been raised by the important discoveries to date; the facility performance continues to improve dramatically; the user base remains energized and committed; the Nuclear Physics community’s visions for the long-term future of QCD-related research are best realized using RHIC as a primary base.” The major emphasis in the White Paper and in our presentations to the Tribble Subpanel is on the compelling open science questions that can only be addressed at RHIC, or by the combination of RHIC and LHC, and on RHIC’s clear plans to answer these questions over the coming decade by exploiting recent, ongoing and proposed facility upgrades. We stressed that the major luminosity upgrade for RHIC high-energy heavy-ion collisions has now been completed, very cost-effectively, and it is time to reap the science rewards. Tables of the compelling science questions from the past decade, for the coming decade and of the sequence of runs, and future upgrades, needed to address them, are copied below from the RHIC White Paper.
Table 1. Basic questions going into the RHIC era and answers from RHIC to date
a) “Hints” implies that significant data have been collected, hinting at a definitive answer. However, questions of interpretation remain, with clear follow-up measurements proposed (and outlined in Section 6 of the White Paper) to resolve the ambiguities.
Table 2. Second-decade questions and the facilities needed to address them.
Table 3. Approximate timeline for next-decade RHIC science program. The science goals are illustrative; many others will also be pursued with same colliding beam species and energies. Species, goals and subsystems in blue are aimed primarily at the spin program, in red at the p+A program, and in magenta at the combination of the two. The timeline assumes 15-20 cryoweek runs per year.
The science arguments are necessary, but probably not sufficient to overcome the perceived self-interest of proponents of the other major nuclear science facilities. Thus, we also tried to drive home several essential additional points:
As summarized at the end of the RHIC White Paper, “The most sensible approach to a several-year budget crisis is to find creative ways to exploit the resources that have been built up by past investments, as long as they are still operating at full efficiency.”
As expected, the questioning by Tribble Subpanel members for the RHIC presentations was pointed, but focused on the real issues. From what I have heard from others who remained for presentations by other facilities, there was similarly pointed questioning for FRIB. The Tribble Subpanel will now work on preparation of sections of their report, but they will not meet face-to-face again until the second half of November. There will be an opportunity for more community input in the coming two months, and especially at the DNP Town Meetings in Newport Beach. The RHIC Users Executive Committee prepared a letter to the Tribble Subpanel that many of you signed, expressing the importance of continuing RHIC operations to your own research and education plans going forward. This support letter is much appreciated, and I urge you also to act individually to make your views known via the Subpanel’s web page: http://cyclotron.tamu.edu/nsac-subcommittee-2012/. The recommendations of this Subpanel are critical to the future of U.S. nuclear science; there is a daunting possibility to greatly diminish U.S. leadership in this field, and the collective wisdom of the entire community, not just the Tribble Subpanel members, must be brought to bear on the outcome.
The Subpanel’s report is due to DOE and NSF in January 2013.