After achieving first collisions of gold ion beams on the night of 12 June (July p5), the gleaming new Relativistic Heavy Ion Collider (RHIC) facility at
Brookhaven wasted no time in ramping up in energy and intensity and
starting the process of analysing data.
A few days after the first gold
ions collided at a collision energy of 56 GeV/nucleon, all four of the RHIC
detectors (BRAHMS, PHENIX, PHOBOS and STAR) began recording data
at a collision energy of 130 GeV/nucleon. By the end of July the first physics
result – a measurement of charged particle density at mid-rapidity for central
gold-gold collisions at these two energies – was submitted for publication by
the PHOBOS collaboration.
With these data points in hand, and
further analysis results in the pipeline from each of the four experiments,
theorists who were at Brookhaven to attend a series of summer workshops
immediately began to ponder the first glimpse of high-density matter in this
new energy regime.
In the meantime the machine staff shifted focus
from first collisions to achieving sustained collider operation. The goal for
machine operation over the summer was to bring the collider and its injector
complex, consisting of tandem Van de Graaff, booster and AGS synchrotron,
to the level at which all of the experiments would obtain an initial data run
with event rates approaching 10% of the final design luminosity.
mid-August, RHIC’s two superconducting rings were routinely colliding
stored beams of gold ions, with the full complement of 55 ion bunches in
each ring, beam lifetimes of more than 4 h and some storage cycles lasting
10 h and more. The four experiments simultaneously recorded data
throughout these runs, transferring data to the RHIC Computing Facility at
peak rates of more than 40 Mbyte/s.
RHIC ran through
mid-September, with continued data taking as well as accelerator physics
work to complete the commissioning of the collider systems. A
comprehensive look at the first physics results from this year’s run will take
place at the Quark Matter 2001 meeting on 15-20 January, which is being
jointly hosted by the State University of New York at Stony Brook and
Brookhaven. It is expected that the collider will start up again early in 2001
and begin operating soon after at the full design energy of 200 GeV/nucleon
for gold-gold collisions.
Tom Ludlam, Brookhaven.