From: Flemming Videbaek (videbaek@sgs1.hirg.bnl.gov)
Date: Fri Aug 22 2003 - 10:16:06 EDT
Hi
I enclose FYI the minutes from the Rhic Spin Group meeting last Monday.
regards
Flemming
------------------------------------------------------
Flemming Videbaek
Physics Department
Brookhaven National Laboratory
tlf: 631-344-4106
fax 631-344-1334
e-mail: videbaek@bnl.gov
Sent: Thursday, August 21, 2003 5:55 PM
Subject: Monday RSC Summary - Discussion of Spin R&D in Run-04
|
| Hi y'all,
|
| Gerry put together a summary of the Monday RHIC Spin Meeting in which we
| discussed 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 measuements 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 extimate. 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.
|
| Gerry
|
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