Occupancy and energy deposition estimations

We have studied Crystal Detector response at AuAu200 collisions with the following centralities:

Centrality	Range of impact parameter	number of events
central	0 - 3	~5k, jobs running
midcentral	3 - 6	3.5k events used
midperipheral	6 - 9	~4k, jobs running
peripheral	9 - 12	3.8k events used

Detailed explanation of MC centrality by Lidia : http://www.star.bnl.gov/STAR/comp/prod/EvCentrality.html

For each centrality bin we calculate occupancy and energy deposition for :

1. all sources : albedo + non-photonic + photonic to get overall picture
2. albedo from BEMC
3. non-photonic sources, all particles but photons hitting our supercubes
4. photonic sources, mostly photons from Pi0 decays - considered as signal (along with direct photons)

Common path for all files at RCAS : /star/u/dmitry/AFS_WWW/2006/crystaldetector/root/...

1. Download link: peripheral events
2. Download link: midcentral events [1] midcentral events [2] midcentral events [3] midcentral events [4] midcentral events [5]

1. Crystal Detector geometry is fully implemented within STARSIM framework (g2t tables) and BFC chain (St_geant_Maker, StMcEventMaker, StMcEvent)
2. 3 supercubes composed of 9x20 CsI crystals, crystal dimensions: 2.54 x 2.54 x 25.0 cm, crystals wrapped in thin mylar.
3. Preliminary acceptance: -0.66 < pseudorapidity < 0.0, -3.0^o < phi < 3.0^o. Effective acceptance still has to be studied.
4. Full BEMC installed, SVT is NOT removed from geometry (HFT is not installed also). It is up to Maxim to decide what exactly STAR geometry should look like in 2008.
5. single BEMC tower at eta=0 roughly equals to 4x4 CRD crystals
6. AuAu 200 GeV events simulated in four main centrality bins: central, midcentral, midperipheral, peripheral.
7. We used default hijing pi0s (i.e. no PHENIX points) because most of our photons come from pi0 < 1.0 GeV and PHENIX points start from 1.25 GeV and go up to 11.75 GeV. See http://www.phenix.bnl.gov/WWW/info/data/ppg014_data.html for details on PHENIX pi0 published yields.

1. Selected events images
2. Crystal Detector STARSIM images
3. Pi0 decay angle

Occupancy definition: number of hits with deposited energy over 1 MeV per cube per event (180 hits max. per cube, 3 cubes).

Albedo definition: CRD hits from particles which have bigger energy deposition in BEMC than CRD

Peripheral Events

Source	Occupancy	Occupancy RMS	Occupancy, %
all sources	10.3	9.8	5.7 %
albedo	1.9	2.3	1.1 %
non-photonic	5.3	6.7	2.9 %
photonic	3.2	5.9	1.7 %

Midperipheral Events

Source	Occupancy	Occupancy RMS	Occupancy, %
all sources	29.6	15.7	16.4 %
albedo	5.7	3.8	3.2 %
non-photonic	15.2	11.4	8.4 %
photonic	9.7	10.3	5.4 %

Midcentral Events

Source	Occupancy	Occupancy RMS	Occupancy, %
all sources	51.2	18.0	28.4 %
albedo	10.6	5.1	5.9 %
non-photonic	27.2	14.0	15.1 %
photonic	17.6	13.3	9.8 %

Central Events

Source	Occupancy	Occupancy RMS	Occupancy, %
all sources	67.9	18.4	37.7 %
albedo	14.5	5.5	8.0 %
non-photonic	35.8	15.0	19.9 %
photonic	23.7	15.1	13.2 %
neutrons + antineutrons	5.1	6.6	2.83 ± 3.6 %

Energy deposition definition: deposited energy per cube per event from selected source.

Albedo definition: CRD hits from particles which have bigger energy deposition in BEMC than CRD

Peripheral Events

Source	Energy deposition, GeV	Energy deposition RMS, GeV
all sources	0.17	0.23
albedo	0.009	0.01
non-photonic	0.08	0.16
photonic	0.07	0.16

Midperipheral Events

Source	Energy deposition, GeV	Energy deposition RMS, GeV
all sources	0.50	0.41
albedo	0.03	0.02
non-photonic	0.26	0.29
photonic	0.22	0.29

Midcentral Events

Source	Energy deposition, GeV	Energy deposition RMS, GeV
all sources	0.93	0.54
albedo	0.05	0.03
non-photonic	0.48	0.36
photonic	0.40	0.39

Central Events

Source	Energy deposition, GeV	Energy deposition RMS, GeV
all sources	1.26	0.63
albedo	0.07	0.03
non-photonic	0.65	0.43
photonic	0.54	0.45

Zoom on [0..0.2] GeV region for fotonic energy deposition

Calculations: every event is checked for photons with 95% energy deposition, which do not overlap with hits from albedo or hadrons (no background removal required at this stage).

Rates are pretty much the same for central and peripheral events. In central events it is harder to find a photon which does not overlap with background, and in peripheral events we see clear photons but they are rare...

Summary: we need ~1M minbias events to perform descent energy scan in [0.020 .. 0.200] GeV region. Pessimistic guess that ~10M minbias will be needed, so real number should be somewhere within these numbers.

Please, see the following link : rate estimations