Michael Murray wrote: Hi Michael- Please see line 5-6 in this message Dec 20-Jan 24. Kris is planning to come here on Jan 18 I believe. The most difficult time is of course from Dec 22- Jan 2 - surprise. Flemming > Dear Flemming, > could you remind Andrei and I of the time of pp > running? He may be able to come to BNL to help with shifts. > When is the most critcal time? > Yours Michael > > Quoting Flemming Videbaek <videbaek@sgs1.hirg.bnl.gov>: > > > Dear collaborator > > > > I attach and include an update on the pp running discussing changes in > > setup, and run plans. > > > > > > ------------------------------------------------------ > > Flemming Videbaek > > Physics Department > > Brookhaven National Laboratory > > > > tlf: 631-344-4106 > > fax 631-344-1334 > > e-mail: videbaek@bnl.gov > > > > > > Update on pp running / Dec. 7 > > > > The machine commissioning is continuing with machine development so far > > mainly at injection energy, and some colliding beam also injection p=24 > > GeV/c. The major problem so far seem to be a lack of high polarization > > out > > of AGS ~30%. This could mean that the polarized measurements may in fact > > not > > be as feasible as it was forecast. On the other hand this is not a > > stumbling > > block for the pp comparison part of the run. The physics running of the > > pp > > program is still planned to run for 5 weeks from December 20 to January > > 24. > > During the run the pp2pp will have dedicated runs for possible 2 days > > with a > > low number of bunches. Actual machine and run plans are developed at > > the > > weekly coordinations meeting. > > > > Even though it is still not known how to deal with triggering, > > background > > (see more later) we have to take planning for this period seriously if > > we > > want to collect data, this means setting up a plausible program and > > having > > the manpower at RHIC for running the experiment. > > > > > > - Experimental setup > > > > Several modification additions have been made to the setup. > > > > a) A 3- slat trigger counter was put in front of D1. This counter > > in > > connection with H1 and the RC will hopefully give us a good > > spectrometer > > trigger i.e. select with high efficiency events with tracks through D1, > > D2 > > and not have too many false triggers. This is a must because the > > particle > > densities are down by about a factor 170, while the luminosities up by > > a > > factor hundred, but our DAQ rate probably only goes to maybe 150-200 > > /sec up > > from ~80-90/sec. > > b) The pp2pp experiment has installed a set of inelasticity > > detectors > > that will also help BRAHMS in identifying collisions. The detectors > > consist > > of 8 modules each with 4 quadrants and positioned around the beam pipe > > on > > each side of the IR. They were designed to have a high efficiency for > > inelastic pp events (double, and single diffractive events). More > > details on > > the geometry can be found on > > http://www.sdcc.bnl.gov/brahms/private/detectors/pp/index.html . > > Signals > > are split at the PMT level using transformers and fed to our FE-hut. At > > present each signal is connected to a discriminator, and logic setup to > > select pp collision events. We want to feed all signals to TDC. At > > present > > there are not enough delay cables for all 32 channels, so only a single > > tdc > > channel is instrumented from each module (total of 8). > > c) A large slat with two PMT has been build and put in front of > > the > > MRS. This will prevent the MRS to go much more forward than about 60 > > deg, > > unless the D5 platform is moved back as done in part of the Au running. > > Ideal though you would want TPM1 to be as close as possible to the IR > > for > > the pp running (increase solid angle). A set of large slat will also be > > installed behind the TOFW ( so a trigger can be formed (we cannot setup > > a > > trigger based on the 125 slats due to lack of space, and electronics). > > > > - Run plans > > > > There are two basic goals we want to achieve. (see RBUP and > > presentations of > > this) > > One: comparison /reference spectra for pi, K and p at several > > rapidities. > > Two: investigation of feasibility of transverse polarization > > measurements. > > > > The expected pp luminosity will result in an interaction rate of about > > ~50-200K/sec, while at the same time the yield compare with Au-Au is > > down by > > approximately 175. > > If the trigger rejection factor can be brought up to above 50 we will > > get a > > trigger-rate of about 1K/sec still high so the utilization of the beam > > luminosity is not optimal. I am hopeful that the FS trigger can be > > brought > > to work, but it is by now mean assured. So in laying out the program we > > should be careful not over evaluating how much useful data can be > > collected > > at a given luminosity > > It would be very good in addition to spectra at a few angle setting to > > get a > > reference spectrum to the 12 deg setting. > > > > The second goal is one that will help establish if in up-coming run we > > will > > be able to perform an asymmetry measurement at high Xf i.e. at small > > angle > > and high field. This involves trigger studies and learning how to > > record > > polarization information. > > > > > > - shifts > > For the second item first I will like to gather from each institution > > the > > effort that is available in the above mention period for running the > > experiment. I will request to have this in hand by Monday, and will then > > see > > how (bad) the situation turns out to be. > > > > > > Looking forward to hear from you. > > > > Flemming > > > > > > Michael Murray, Cyclotron TAMU, 979 845 1411 x 273, Fax 1899
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