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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