Dear BRAHMS friends
Below are my comments (following a converstion with Ian) on the run plan as
a follow up of earlier mails
and also Flemmings latest.
0) Strongly suggest that we move the BFS to 12 degrees so that for the
current data talking we have the full FS operational.
Agree that 12 degrees is an intersting setting (sin(12) =0.2 = > high
pt)
1) Suggest that we concentrate on 3,4,8, and 12 degress. 2.3 and 20 are
lesser priorities and should be reserved for later.
2) Suggest that after 12 degrees that we go back to 4 deg and collect
various field settings and then proceed to map out 3,8,12 at higher
fields.
The rational is that right now we have a ' bit of everything'. Should
concentrate on having complete data around 4 deg,
ensuring that we have overlapping rapidities for pi,K and p.
3) Vertex trigger is agood way to cut down on rates. it also ensures that
practically all events have a TPM1 vertex
4) I would argue that the peripheral runs have a lower priority, noit leat
because they eat up a lot of beam time The best would
be to implement a (clean) spec. trigger (f.ex H1) before we do this.
Finally I would like to appeal to all BRAHMS collaborators to communicate
the status of the various ongoing analyses to the collaboration.
I am getting increasingly worried that we are falling behind in this area.
Over half a year ago we had working ( although only for a short time)
systematic analysis reports that were widely circulated so that all could
follow the current status, appreciate and assess the problems and contribute
to solutions and work.
regards
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: "Flemming Videbaek" <videbaek@sgs1.hirg.bnl.gov>
To: <brahms-l@bnl.gov>
Sent: Monday, October 08, 2001 1:05 AM
Subject: run and analysis plan
>
> Dear Collaborator,
>
> We have now entered the 8'Th week of the Au running, the beam is steadily
> improving though occasionally there are hiccups. There are two issues for
> the plan for the remaining part of the run. The aim of this mail to get
> feedback from the collaboration particularly on the overall goal, so the
> more routine execution of the data-taking can be carried out with this
clear
> goal in mind.
>
> One issue is the strategic overall goal: what physics do we want to obtain
> in the 2001 run? The other is the practical issue of how we obtain this
> goal, i.e. how many settings and how much time at each of them, and
> scheduling of runs? At the end of the mailing are added information about
> the present status of the machine. Please comment on the plans put forward
> here.
>
>
>
> The primary goal is to ensure that we measure hadron
> spectra (with good statistics) at a number of rapidities. Initial
> measurements should be around the expected mean pt of pion/proton, then
> extending these measurements to higher pt. With the current and expected
> luminosity it is not possible to achieve continuous rapidity
distributions,
> though we can do pt spectra for a few selected rapidities (y=0,1, and at
> large y, 2-3).
> A plan that would cover this reasonable well is to collect data for
> Theta = 2.3, 3, 4, 8, 12 and 20 deg with the 2.3-8 in 2-3 field settings
> (and two polarities)
> and the 12 and 20, 1 setting (2 polarity) with the forward spectrometer,
and
> at 90, 35,40,45
> with the MRS with two field settings (and two polarities) with minimum
goal
> of collecting > 2,000
> protons for the 0-10% centrality bin in a ~30 % region around the
reference
> momentum.
> A more extended goal is to get good statistics for less central
collisions,
> which easily
> requires 5-8 times the running time per setting. The strategy should be to
> ensure the
> coverage and statistics for central collisions before moving on to longer
> run needed
> for less central collisions.
>
> The actual running up to this point has been to a) ensure we get data at
> higher rapidities
> both to overlap last years settings, b) and to explore a wider y and pt
> range by taken
> data at 8 and 3 degrees and c) collect high statistics data for mainly the
> 90 deg,
> but also 45 degree.
> For the day-to day data taking other considerations come into play as a)
> detector conditions,
> b) machine background, need for calibration runs etc, specific requests
for
> zero-field,
> voltage settings. A practical consideration is that the 2.3 deg running,
as
> well as low to
> intermediate momentum runs where the full FS are in use should be done
with
> C1 out
> of acceptance. Such runs should be done at a time where background
> (hopefully)
> are less since the T5, H2 and RICH has to work well for such runs. Access
is
> required
> before and after such switch over. Tactically we also need to know about
the
> performance
> of detectors, quality of runs, good information about actual 'tracks'
> particle, collected.
>
>
> This brings us to the second issue. As discussed at collaboration meeting
a
> long time ago,
> and brought up by Jens Jorgen recently with a specific proposal we need to
> analyze data
> as we go along. We are also at a point in time where this has become
> feasible. A lot of
> effort has taken place to develop code to perform calibrations, overall
> tracking, and
> particle identification using TOF and Cherenkov systems. Truly these will
> have to be further
> developed, but are in such shape that it should be used in a combined way
> for several purposes
> a) Get feedback to experiment on quality and quantity, and to help
detect
> problems with detector components, performance.
> b) Further check quality of data, code and calibrations
> c) Create output data, (root files, trees (ntuple) and histograms, log
> files) that can be used be the collaboration for further though most
likely
> preliminary analysis, and code development.
>
> The plan brought forward is to have this routine data processing occur
> ongoing with the
> experiment, and with the help of people at their home institution having
> responsibility for
> a given period (in the order of a week at a time) to process the data
using
> the RCF farms,
> and storing the output on the data disks. The necessary programs and
scripts
> are being
> put together by Ian; the system has been checked out. The next step is to
> make the
> more detailed plan including which other institutions are involved, how
the
> output is
> made available to all etc, and to process in a systematic way.
>
> This kind of coordinated effort is also a model for how we can later
perform
> 'final'
> calibration and analysis passes on the data. I have talked to Ian and
> and he is preparing a detailed implementation plan for data reduction and
> calibration.
> Just as the efforts from all collaborators are needed to take the data,
> such an efforts
> is needed for the analysis with the hopefully much more data to come in
the
> coming weeks.
>
>
> // status ..
>
> The machine is now improving a lot, particular in regard to
reproducibility.
> RHIC may
> have reached a limit on ions per bunch with a max current around 25-30
> 10**9 ions,
> so the focus is on the beta* of 2 acc, and increasing to 120(112)
bunches.
> Presently
> RHIC fairly routinely gets to 300 ZDC/sec and can go to ~700 with beta*=2.
> This
> implies that in the operating conditions with 1h re-fill time one can
> achieve ~300-400K /hour,
> and with 50% availability for beam 5M/day, which will be sufficient for
the
> program.
> With such rates it is necessary to impose more stringent triggers. My
> suggestion is to
> implement the vertex trigger, rather than the centrality trigger. The
> vertex trigger will
> sample in a region +-20 cm with high efficiency, rather than attempting to
> utilize a
> wide vertex which can results in quite varying normalizations from run to
> run.
>
> 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 : Mon Oct 08 2001 - 09:50:38 EDT