RHIC Spin Collaboration Meeting XIX, August 18, 2003

by B. Fox and G. Bunce

Discussion of the details and importances of the R&D efforts in Run04
for the spin program.

To open the meeting, Thomas Roser commented that his recent memo on
guidance for a 5 year plan did not readdress spin R&D, from an earlier
memo which covered just 1 year. He and his group have done that now, and
this was presented yesterday. He plans to write an official memo on to
supplement his existing memos on the machine. Here is the outline of
spin R&D that Thomas presented:

Below is a possible schedule for a pp R&D run for FY04. Maybe I could
show this at the start of today\'s meeting.

Polarized jet installation at IP12 3 days

Set-up of power supplies and get first collisions 14 days

Set-up of minimum luminosity to start R&D 14 days

Beam-beam tests (new working point, \...) 5 days

Polarized jet commissioning parasitic to above

dp/p = 10% measurement with jet 7 days

Spin flipper commissioning 3 days

Tune feed-back commissioning 3 days

\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

Total 49 days (7 weeks)

Following Thomas\'s presentation of this outline, Wolfram Fischer
discussed the beam-beam effect which was observed in pp in 03, and their
work toward defining a new \"working point\" (betatron tune for RHIC)
which would provide more room for the beam-beam tune spread. They are
using simulations to study possible tunes, and this work is in progress.
Two new tunes are being considered. The large bulk of the R&D time above
is for this (basically 4 weeks would be used to set up a new tune and to
study it). Setting up a new tune (ramp and flattop) is described as a
major effort. The goal is to find a stable tune location for both
luminosity and polarization, prior to a long spin run in 05.

Next, Anatoli Zelinski described the preparations of the polarized jet
target. The intensity has been measured at 4x (!) the former record for
atomic beams, using 3 methods of measurement. (The result is 30% higher
than predictions from simulations.) The rf transitions are now being
installed, which are not expected to change the intensity, just provide
polarization. Polarization is to be measured in September. In October
the jet will be installed in RHIC (12 o\'clock), tested, then returned
to the lab. (The vacuum level precludes leaving it in place for the
gold-gold run.). The design plan allows quick installation (3 days,
including pump down), which will be tested in October.

The target would be commissioned parasitically with the beam-beam work.
The 7 days indicated above for a polarization measurement are likely to
be parasitic to, for example, experiment data-taking.

And, finally, Mei Bai discussed the spin flipper. The idea is to flip
the spins in one ring, to decouple crossing dependences of our
measurements from spin. Kiyoshi Tanida has shown, for example, a clear
crossing dependence of the width of the longitudinal vertex distribution
at Phenix which persists through the store. Ultimately, this device
would buy us roughly an order of magnitude on systematic errors due to
crossing effects in measuring asymmetries. (This is my estimate. Kiyoshi
found that spin flipping is not

needed at our present 10\^-3 statistical error in raw asymmetry.
Therefore, I see this as developing a potentially important tool for the
longer term spin program. The device also provides a clean way to
establish the settings for the Siberian Snakes.) The proposed 3 days
includes studies of settings for the spin flipper (rf dipole frequency
and amplitude, at injection and 100 GeV). This work had some success in
the 02 run. In 03 the tests gave beam aborts from Phobos radiation
monitors.

In addition, Waldo showed us a picture of the new AGS Siberian Snake
(5%). It is now wound (at RIKEN in Japan). It is expected to be
installed in the AGS this fall/winter. With it, the polarization
improvement is expected to be 25% (that is, from 0.4 to 0.5 in the AGS.
The machine group plans to commission it and develop AGS polarization in
a 4 week run parasitic to the gold-gold running.

To close the meeting, we had a discussion which focused on a 5 week R&D
effort to study the beam-beam effect and to commission the jet target.

We also discussed potential physics if the figure of merit is improved
from 2003 by a factor of 10 or more. (F.O.M. = P\^4 x LT; stat. errors
\~ sqrt F.O.M.) From polarization improvement to P=0.4 alone, the F.O.M.
improves by a factor of 5. If a factor 10 improvement in F.O.M. is
demonstrated from the 5 week R&D, we could then get a very exciting
measurement of gluon polarization using pi\^0 at PHENIX and jets at
STAR, in a 1 month physics run. This measurement would also be timely,
far better than COMPASS at CERN which expects to run also in 2004.