Dear Collaborator,
Though there is a few more hours left of the Au-Au running let me give you a brief report on run achievements and the near future.
The BRAHMS data taking really picked up once the beam was bunched, and the vertex trigger impleneted, a good 6 weeks ago.
During this time we collected about 9M trigger 6 (eq. 10 inverse micro.barns) for the survey measurement mainly for
central collisions. This covered essentiall from y=0 to 3.5 (pions) and pt ~0.3- 1.5, and should yield a good basis for particle
pt- and rapidity distributions. In the last about 2 weeks we further collected ~5M trigger 6 for two high statistics studies, namely
2.5-3.5 GeV/c at 12 deg, and up to 4 at 90 deg. In the initial part of the run we collected in the order 10 inverse micro barn albeit with wider
vertex, higher background that makes these data somewhat useful.
Though successful, many items hoped for in the RBUP (120-150 inverse microbarns) was not achieved.
-- The high rapidity program did not extend to 2.3 deg. The measurements were probably too few at the low pt (at high y)
C1 was always in place , i.e. not running the BFS in the optimal way.
- The high pt studies were really too short 5M will probably only give resaonable spectra out to ~3 maybe 3.5 GeV/c, data were
only with one polarity etc.
The data we collected should though give us plenty of physics results, as well as a better understanding of the running conditions, and what
is actually achievable with the spectrometer system. They should also be used well to plan for next years runs, as for possible upgrades.
Some words on the near-term running:
The 22 GeV run is on-going until Monday at 6.00 am . The machine actually did much better than anti-cipated with not too bad background, as well as reasonable lifetime(45 min).
On the other hand, as predicted, the Beam-Beam counters seem to be in-efficient as such low energy (at too large eta) , and it is not obvious
if any physics at all will come out of this short run, though we will attempt to confirm the multiplicity measurements with si-tiles-BB and the tpm1.
Also the statistics will not be good. The collision rate is about 20 -> 5 ev /sec maybe enabling us to get ~100k triggers in this period.
Next week is open access to be used for installation of the counters for the pp triggering (FS t0, pp2pp in-elasticity counters), followed by several weeks
of polarized pp commisioning. The official schedule calls for pp running starting Dec. 20 until Jan 24, and we need in the near two three weeks to come with
a plan for our usage of this period. I personally envison an early commisioning period followed by ~ 3-4 weeks solid running in January. This
of course requires a) triggers b) plan for physics and finally also YOU or at least some of you to man the experiment.
I will also remind you that we plan to have a collaboration meeting at BNL on Jan 28-30 following the pp run for which
should focus on a) lessons learned on detectors this run b) analysis plans c) plans for next run (FY2003) in particular for upgrades/ additions
Finally a thanks to all with the contributions to the execution of the experiment by detector maintance, manning the many shifts,
and monitoring and analysing the data.
Best regards
Flemming
------------------------------------------------------
Flemming Videbaek
Physics Department
Brookhaven National Laboratory
tlf: 631-344-4106
fax 631-344-1334
e-mail: videbaek@bnl.gov
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