STAR run 2013 pp510 GeV BEMC Calibration

Introduction

This page outline a summary of STAR run 2013 510 GeV  BEMC Calibration which is the first STAR pp 500 GeV energy calibration of the STAR BEMC detector. The Calibration was performed in two steps similar to previous BEMC Calibrations that was performed at STAR. ( STAR 2012 pp200 GeV BEMC Calibration, STAR 2009 pp200 GeV BEMC Calibration, STAR 2006 pp200 GeV BEMC Calibration). During the STAR 2013 pp500 W AL analysis the requiremnet of the BEMC detector calibration was urged due to following reasons.

• Reconstructed Z invarient mass peak from STAR 2013 data is shifetd by ~ 4.6 % towards low mass in comparison to embedded MC.
• Reconstructed W Jacobean peak position from STAR 2013 data is shifetd towards low ET  in comparison to embedded MC and Run 12 data.

EMC -meeting-Calibration request - 03-03-2015 (slides)

Relative Calibration using MIPs (ADC) 

Absoulte Calibration using Electron/Positrons ( E / p )

• Method

The idea used here is that since electrons deposit all of their energy in the calorimeter towers, to compare that energy to the momentum of the electron track from the TPC. For a perfect calorimeter E=p = 1 assuming electrons to be massless which is a  fine assumption for the tracks with momentum of order of GeV=c. First Trigger requirment was imposed based on the stability of the electrons E /p over the momentum region which was considered. Since no abundent electrons find tower by tower they were grouped in to "eta rings" and then E /p distrubutions of each ring was fitted using "gaussin + exponential" functions to assure that BG wer properly considered. A Gaussian mean of  <E/p> was extracted from the fitted funtion and then used to ajust the relative calibarion constant henase obtain abosoulte gain constant for each tower.

• Electron Selection Cuts

1. Rank < 1e6 
2. -60 < Z_vertex<+60

1. 1.5 < Track P < 15  :               Studies  done on track momentum => Click (here)
2. Tower QA cuts (Tower Status = 1, mip Status =1, )
3. Track nHits > 25  :                   Studies  done on track nHits => Click (here)
4.  

• Trigger Options

  Run 2013 Trigger Information (BHT , HT)
   

• Energy and Momentum distributions 

• Energy vs Momentum 2D distributions

• E / p vs Momentum 2D distributions 

• <E / p > in Momentum slices distributions 

• Energy and Momentum distributions 

• Energy vs Momentum 2D distributions

• E / p vs Momentum 2D distributions 

• <E / p > in Momentum slices distributions 

Distributions considering only  tracks which matched to triggered Tower

EMC -meeting-updates - 03-29-2016 (slides)

• Accessing non HT triggers may introduce biases due to veto ing on HT did fire() conditions, can't really tell exactly what triggers are considered. [obtain truth tables to understand various trigger conditions of accessing non HT triggers].
• Understandand clearly the syaytamtic differnece of E /p between JP2 (or other non HT for that matter) and HT below the HT thershold. May be consider HT (BHT3)  below the thershold and fold the differnces in to systamatics.
• Check out the distribution of E /p for HT triggers after removing tracks which matched to a triggerd tower

2x2 Cluster Method  

EMC -meeting-updates - 05-10-2016  (slides)

Systamatic Error Calcualtions

EMC -meeting-updates - 06-21-2016 (slides)

Summary 

Spin PWG -meeting-summary report - 07-11-2016 (slides)

Run 13 BEMC Calibration Gain Constants 

Momentum Dependance for E / p for HT trigger [ E / p drop study]

Analysis Note

References