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New polarized gluon distributions in Pythia

So we now have access to a wide variety of gluon polarization parameterizations in our Pythia afterburner covering the regions between GRSV -std and -max and between GRSV -zero and -min.  Dave Staszak documents the details of the new distributions at

http://www.star.bnl.gov/protected/spin/staszak/2006/Sims/trigBias/trigBias.html

Here are plots of the raw charged pion asymmetries obtained from these grids (p070 excluded because of a bug on my part):

I suspect the problem with the pi-minus asymmetries can be traced to a lack of gg contributions.  For more information see Agreement Between "Polarized" Pythia and NLO pQCD.  In the remainder of this document I'll stick to analyzing pi-plus data.

I've attached multi-page PDF at the bottom of the page.  Each page of the PDF plots, for a give input gluon polarization distribution A_{LL}(trigger) - A_{LL}(no trigger) as a function of pion p_T.  There are six plots on each page; one for each trigger in (minbias, HT1, HT2, JP1, JP2) and then the raw A_{LL}(no trigger) distribution itself in the bottom right.  I believe one way we can obtain a systematic uncertainty from plots such as these is to calculate a double-sided max( delta A_{LL}, uncertainty on triggered A_{LL} ) for each pT bin we use to make our measurement.

One question is which grids are appropriate ones to use for calculating the systematic.  GRSV-max has been excluded in other measurements, so I don't think it's appropriate.  All other grids are fair game, which means the systematic will likely be derived from GRSV-min and p070 (once I rerun; use p060 for now).

Agreement Between "Polarized" Pythia and NLO pQCD

We're using an afterburner framework that turns Pythia into something like a LO polarized event generator to study any biases introduced by our triggers on A_LL measurements.  This page compares the asymmetries generated by Pythia to theoretical predictions from GRSV.

Cuts

  • MC and reco vz positions inside 60 cm
  • |eta| of reco primary track < 1.0
  • dca of associated global < 1.0
  • fit points > 25
  • select pions using geant ID 8 (pi-plus) or 9 (pi-minus)

No trigger requirements are imposed.

Weighting

I combined MC samples 3_4 through 55_65 using the following cross sections and event counts

xsec = {
'3_4' : 1.287, 384593
'4_5' : 3.117*10**-1, 586568
'5_7' : 1.360*10**-1, 380791
'7_9' : 2.305*10**-2, 404272
'9_11' : 5.494*10**-3, 413651
'11_15' : 2.228*10**-3, 418547
'15_25' : 3.895*10**-4, 407427
'25_35' : 1.016*10**-5, 99998
'above_35' : 5.299*10**-7, 119995
'45_55' : 2.830*10**-8, 119995
'55_65' : 1.433*10**-9 119998
}

Plots

First off, here are the asymmetries integrated over all subprocesses.  The left column is pi-plus, the right column is pi-minus.  The agreement for postive charges seems basically acceptable to me, but pi-minus is off by quite a lot:

If I restrict to g-g, q-g, and q-q subprocesses individually, the difference between the two is obviously in the q-g subprocess contribution (as expected):

It seems to me that the lack of agreement between our Monte Carlo and the theoretical predictions could be due in part to a lack of gg / over-abundance of qg in the subprocess mix.  Here are plots of the subprocess mix from Pythia:

compare that to the prediction from Vogelsang et al. for inclusive pi0 production, where gg is the primary contributor until ~3 GeV:

In particular, only the 3_4 GeV partonic sample has more g-g than q-g at any pion p_T.  I'm going to try including the 2_3 GeV sample in my studies and see if that bolsters the gg contribution.

Paper proposal : Pion HBT in AuAu@19.6 GeV

Title : Pion HBT in AuAu@19.6 GeV
PWG:
HBT
PAs: Z. Chajecki, M. Lisa
Target Journal: PRC

Efficiency for StGammaPointMaker

The question of why the pion maker is so inefficient came up this morning in the photon group.  I'm posting this to try and shed a little light on where these inefficiencies arise.

StGammaPointMaker

I have been working on developing a point maker to work in conjunction with StGammaMaker.  The idea (from my end) was that you would input gamma candidates to the point maker and you would get ou

Summary of Technical Details for Run 5 analysis

Data Collection

  • MB || JP1 || JP2
  • BBC timebin in {7, 8, 9} -- roughly equivalent to 60 cm offline vertex cut (see BBC Vertex)

Conformal String Breaking in QCD: Dima Kharzeev

I'm attaching a pdf of the talk given by Dima Kharzeev and sent to the BES list by Helen Caines:

http://www.star.bnl.gov/HyperNews-star/protected/get/bescan/26/1/2.html

Radiation estimates for TOF rings

Here I give rough estimates for the radiation we can expect for the inner ring on the currently considered forward TOF rings. Rates are taken from run 7.

2007 BEMC Calibration check with stgamma production electrons

To perform a check on the BEMC calibration for run 7, I began by looking over the electrons from the StGamma production. 

TPC DV Test Production

Following the analysis in 2006 TPC Drift Velocity Investigation we did a test production with the new interpolated DV values.  Here's a plot as the magnitude of the global DCA for primary tracks from run 7142036 (pt>2,