The STAR experiment

A schematic view of a cross section is:

Requests #1154003721 and #1154003633 (Upsilon and J/psi into Pythia+pp)

Data Cuts:
L2Gamma Triggered Events
BBC timebin 6 - 9
Pt > 5.2
No Charged Track Association
1 SMD strip good in each plane

There's been quite some discussion about the saturation of the BSMD ADCs around 850.  We don't have this feature in the simulator, so here's my attempt to put it in.

Here's a plot of the ADC and energy distributions from the slow simulator in DEV without any reconfiguration.  This is the output of testSimulatorMaker.C using 1000 events from photon MC (photon_25_35_10.geant.root):

Note the sharp ADC peaks at 1023 for the SMDs and the PRS.  Now if I configure the simulator with the options (not yet in CVS)

Update

These changes were checked into CVS on October 08 2007

Prompted by the recent discussion of the BSMD energy I looked at some histograms for hits from 2005 data. Currently I don't have individual strip energies, I only have SMD clusters saved.

The cross-section requires the following components:

• Jobs finished successfully
• MiniMc was generated (new feature as of Friday)

In order to get the most realistic performance possible out of the FGT Slow Simulator, all important physical effects have to be incorporated.

BSMD

The SMDs can be simulated in one of two modes.  In a rewrite of the slow simulator I call them kTestMode and kSimpleMode.  kTestMode doesn't do anything interesting, so let's focus on kSimpleMode.  Here are the steps to generate an ADC:

1. ADC = energy deposit * sampling fraction(eta) / calib
2. ADC += mRandom.Gaus(pedMean, pedRMS)
3. ADC *= mRandom.Gaus(1.0 + calibOffset, calibSpread)
4. force ADC between 0 and maxADC

The energy is then calculated from this ADC is the usual way:  energy = (ADC - pedMean) * calib.  Remember the BEMC calibration coefficients are stored as GeV/ADC.

BTOW - BPRS

The simulators for these two detectors have some additional modes (kPrimaryOnlyMode, kPrimarySecondaryFastMode, kPrimarySecondaryFullMode).  Here's the setup for the kPrimaryMode:

1. photoElectrons = energy deposit * (MIP photo electrons / MIP energy deposit)
2. smear using Poisson distribution
3. ADC = photoElectrons * sampling fraction(eta) * (MIP energy deposit / MIP photo electrons) / calib
4. follow steps 2-4 of simple simulator to add pedestals, smear calibration, and check for valid range

The other two modes also take the secondary photostatistics from the PMT amplification into account.  I'll focus on the full mode, as it's slightly easier to understand:

1. build a set of secondary electron conversion coefficients (1 / dynode) using the relative voltage distribution among the dynodes and an approximate value for the total PMT amplification.
2. Loop through dynodes and at each step
   1. nElectrons = mRandom.PoissonD( mSecondaryCoeff[i] * nElectrons + mDynodeNoise );
3. ADC =  nElectrons * mTotalDynodeGain *sampling fraction(eta) * (MIP energy deposit / MIP photo electrons) / calib
4. follow steps 2-4 of simple simulator above

The mTotalDynodeGain in step 3 is the inverse of the product of the secondary electron conversion coefficients.