September 5, 2012
Dear NSAC Subcommittee:
We are writing you to express our commitment to the ongoing science program at the Relativistic Heavy Ion Collider (RHIC), and to request full support for its running in the next decade.
Since the first collisions of gold beams in 2000, and polarized proton beams in 2001, RHIC has experienced an era of unparalleled scientific productivity, with major advances for nuclear physics from nearly every experimental run, and many major discoveries about the properties of hot, dense nuclear matter. This began with the earliest observations of jet quenching and collective flow, which led to a breakthrough when it was realized that the quark-gluon plasma formed at RHIC is best described as a near-perfect liquid. It has been shown to be one of the most perfect liquids found in nature, and its temperature was recently measured to reach an astounding seven trillion degrees Fahrenheit, with conditions similar to those of the early universe, just microseconds after the Big Bang.
The results at RHIC have found widespread acclaim in the scientific community as well as with the general public, and sparked surprising connections with seemingly unrelated fields such as ultra-cold atomic physics and string theory. RHIC data have also provided the essential context for new results from the collisions of lead beams at the Large Hadron Collider (LHC).
The RHIC scientific community is a large, international group of experimental and theoretical physicists, and we feel strongly that the future of the study of hot, dense quark-gluon matter worldwide relies on continuing US leadership. While the recent LHC data have provided important new insights to the field, it is clear that only RHIC can produce the widest range of initial conditions necessary to characterize how the nearly perfect liquid is created and how it behaves. These questions are of clear relevance to understanding the strong interaction at a deep level as well as for providing insight into how the very early universe may have evolved. RHIC is also the world’s only polarized proton collider, an essential tool for investigating the origin of proton spin, an ongoing mystery in physics.
These programs exploring various aspects of nuclear physics at RHIC serve as a major resource for training the next generation of nuclear and accelerator physicists. Since 2000, about 350 graduate students have performed their PhD research at RHIC. These students have gone on to contribute to our society and economy in a variety of useful roles, both in science and other fields. Society also benefits significantly from the use of beams from the RHIC complex for a wide range of scientific and medical applications: the development of cancer treatments, radioisotopes, radiation detectors for national security, and assessing the feasibility of long-term space travel.
The next five years will see the full exploitation of RHIC's capabilities: the wide range of beam energies, the wide variety of colliding systems using the new EBIS ion source, and the high luminosities provided by stochastic cooling for ions and electron lenses for polarized protons. The recent (and imminent) upgrades to both the PHENIX and STAR detectors will allow us to take full advantage of these new capabilities. For the years beyond 2018, the RHIC collaborations are planning major upgrades to their systems. These will both dramatically enhance their performance for jets and quarkonia, which are important tools for characterizing the underlying physics of the quark-gluon plasma, and for a wide array of measurements in the forward direction, which will give unique insight into the deep structure of the nuclear wave-function.
We are convinced that continuing the RHIC program is essential to produce world-leading science from the US nuclear physics program -- using the only remaining collider in the United States -- and it is critical to our own research, and that of our students, in the next decade.
For these reasons, we urge your support for RHIC, as its most productive years are still to come.
The RHIC complex scientific community
Please note: This letter was signed by 740 plus individual's supporting the RHIC scientific community