Hi, in my previous vote I was arguing for a choice that implies dropping plans to study high Pt and to concentrate on surveying one point in forward rapidity. I think we make a great contribution if we collect data that can be fitted with an statistical model to see what value of baryon chemical potential can be achieved with BRAHMS tools, are we above cold nuclear matter? If that is the case BRAHMS would became a window to another system and that would certainly validate our existence. My understanding of the statistical models implies the extraction of T from Pt distributions and fits to particle ratios. The extraction of T needs a good understanding of efficiencies and acceptances and that is where my vote density drops precipitously unless we put some numbers on our best wishes. Ramiro Jens Jørgen Gaardhøje wrote: > Hi Ramiro > The motivation for the 12 deg is to study jet-(or no jet) quenching. This > requires high pt. > Sin(12)=0.2 and makes this possible (pt up to 4GeV). > 12 deg is sufficiently forward that the physics might be different from that > at the mid-rap plateau. > Obviously we would also like to do this closer to midrap, but I feel that it > is more important to see a deviation from the PHENIX-STAR story at the > present time than it is to validate it. > If we validate it , we are just one in the crowd, if we don't see it we have > validated our existence. > cheers > JJ > > ________________________________ > Jens Jørgen Gaardhøje > Assoc. prof. Dr. Scient. > Chair Ph.D: school of Physics NBI.f.AFG. > (secretariat. 35 32 04 41) > Chair science committee. UNESCO Natl. Commission. > (secretariat. 33 92 52 16) > Office: Niels Bohr Institute, Blegdamsvej 17, > 2100, Copenhagen, Denmark. > Tlf: (+45) 35 32 53 09 > Fax: (+45) 35 32 50 16 > ________________________________ > ----- Original Message ----- > From: "Ramiro Debbe" <debbe@sgs1.hirg.bnl.gov> > To: <brahms-l@bnl.gov> > Sent: Tuesday, November 13, 2001 1:48 PM > Subject: Re: 12 degrees is GOOD, was: RE: run plans and rates... > > > I want to add my vote to the choice of forward angles. If Ian's optimism > > is accepted, why not go even further and think about 3 or 4 degrees, after > > all the community is expecting BRAHMS to study the highest rapidities as > > possible and that doesn't require high Pt. > > > > Ramiro > > > > On Tue, 13 Nov 2001, Ian Bearden wrote: > > > > > Hi All, > > > I would like to add a strong second to Flemming suggestion to run at 12 > > > degrees for as long as possible. > > > I think, though, that we should not be so pessimistic as to say that the > BFS > > > has only T4 and 2 of 3 T5 modules. > > > We can certainly use T2 tracks as a 'seed' to find tracks in T3, rather > than > > > relying on T3 alone (that is, one uses T3 to validate and extend T2 > tracks) > > > and this will increase the T3 efficiency by a large factor that I don't > know > > > yet (but which Pawel and Radek are working on). We can play the same > game > > > using T4 and T5, with the small added complication that we have to rely > on > > > the momentum from D2 and D3 and lose the third momentum determination. > > > In fact, even without T5 at all we could do this by matching tracks from > > > FFS+T3+T4 to hits on H2 and rings in the > > > (extremely beautiful!) RICH. Since this is only necessary at high p > where > > > there are few tracks per event on average, there should not be large > losses > > > due to double hits on H2. Again, we lose a little momentum resolution, > but > > > probably not enough that we should lose a lot of sleep over it. > > > > > > Summary: 12 degree high field is GOOD. > > > > > > Ian > > > -----Original Message----- > > > From: owner-brahms-l@bnl.gov [mailto:owner-brahms-l@bnl.gov]On Behalf > Of > > > Flemming Videbaek > > > Sent: Tuesday, November 13, 2001 2:47 AM > > > To: brahms-l@bnl.gov > > > Subject: run plans and rates... > > > > > > > > > Dear Collaborator, > > > > > > I think the question on settings to measdure in the last (1.5 week- > taken > > > into account the STAR problems) of the run comes to a choice, not so > much > > > related to rates for higher pt values but as a matter of detector > > > performance vs. physics goals. > > > > > > Ian has mentioned rates vs pt /triggers in a couple of e-mails. My own > > > evaluation are very close to his. It should be noted that for the same > pt- > > > range and dy bin the rates per trigger 6 are not so different. > > > - the covered dy range gets wider at more forward angles. > > > - the effective p range covered at any angle setting is ~ Pref > 60%-200% > > > with Pref= 23 GeV* Field fraction. > > > Some typical values are > > > 20 deg ~ 12 per 75 MeV/c pt bin at 2 GeV/ce > > > 30 deg ~6 per 100 MeV/c pt bin at 2 GeV/c (outside Pref range) > > > 12 deg ~14 per 100 MeV/c pt bin at 2GeV/c > > > all for 70K triggers 6. > > > > > > So the choice of angles is much more governed by other factor as PID > than > > > rate > > > > > > 30 deg K/p (H1) 6 GeV --> 3.0 GeV/c > > > K/pi (C1) 9 --> 4.5 GeV/c > > > > > > 20 deg 1.5 > > > 3.0 > > > > > > 12-15 deg (p*.2-.25) K/p H1 1.5 > > > k/pi C1 2.0 > > > H2,RiCH K/P 5.0 > > > H2/rich pi/K 3.5-4. > > > > > > At theta < 12 the pt range just get less. > > > Thus to get to the highest pt for identified particles with FS there > are > > > two choices > > > a) 30 deg with well working C1, H1 -> 4.0 GeV/c > > > b) 12-15 deg using the full spectrometer -> 4 GeV/c too. > > > The rates in the BFS are ~ 1`/3 just for solid angle/accpt , with the > > > added problem that > > > we have only T4 + 2/3T5 working at present. > > > > > > The physics issue is briefly that 30 deg is approximately like 90 > (i.e. on > > > the plateau) while the > > > 12-15 deg is actually on the edge/turn over , and might show real > > > diference. Have we enought time the choice is clearly to do both > settings, > > > but with an expected 40h*60k*1.6== 6M events this is not expected to be > > > enough for both settings, including others that will have to be redone . > > > > > > I will point out that my personal physics preference is to do the 12 > deg, > > > as I have advocated for several years), but is concerned that the lack > of > > > tracking in FFS (T5 problems, no T3 and less than 100% eff) will make it > a > > > not guarenteed measurement and thus carries a risk of not getting a > result. > > > > > > I will finally point out that the present 30 deg 2*300k trigger 6 are > for > > > valuable cross chekcs with the MRS data. > > > > > > My suggestion will be in the near term to complete the 30 deg > > > measurements, move to 12 deg, take data at the 1/2 field setting ~500k > > > trigger and get at the same time documented feedback in terms of actuall > > > tracks reconstructed in full FFS (for 12 deg) with PID , as well as for > the > > > 30 deg data so we can judge rates etc for the last week or so > > > > > > best regards > > > Flemming > > > > > > ------------------------------------------------------ > > > Flemming Videbaek > > > Physics Department > > > Brookhaven National Laboratory > > > > > > tlf: 631-344-4106 > > > fax 631-344-1334 > > > e-mail: videbaek@bnl.gov > > > > > > > > >
This archive was generated by hypermail 2b30 : Tue Nov 13 2001 - 11:14:30 EST