BBC-EPD correlations (or lack thereof) in the pre-beam cosmic running
Updated on Wed, 2018-02-28 16:08. Originally created by lisa on 2018-02-28 16:08.
The EPD has been in the cosmic run, and a special trigger (BBC+TOF) has been run and sent to a dedicated "EPD stream".
At our 26 Feb Monday meeting, Rosi posted a first look at ADC distributions from EPD tiles, corresponding to these runs. The post is here: drupal.star.bnl.gov/STAR/system/files/CosmicAdc_small_Day056.pdf
Those plots seem to indicate that most of the time, when there is a TOF-BBC trigger, there is nothing in the EPD!
I have begun to look at the data offline, as the files have been processed to muDsts. There are thousands of events, but so far I have only looked at a few hundred, for non-interesting reasons. However, my study thus far, confirms the finding above.
In every event, there is always one (and only one) BBC tile that fires (i.e. ADC>20). In most events, there are no EPD tiles that fire (ADC>5). Sometimes one or more East EPD tiles fire, and sometimes one or more West EPD tiles fire. Never (in the limited set I've looked at so far) do East and West EPD tiles fire simultaneously.
The two plots below show the multiplicity of East (negative x-axis) and West (positive x-axis) EPD tiles that fire, when it is an East (top plot) or West (bottom plot) BBC tile that fired. At least there seems to be a mild correlation-- when a signal is seen in the East (West) EPD, it is usually associated with a signal in the East (West) BBC. But
I will look at this with higher statistics and in a little more detail, but there is clearly a problem. It must be one of timing. No way is this an "efficiency."
At our 26 Feb Monday meeting, Rosi posted a first look at ADC distributions from EPD tiles, corresponding to these runs. The post is here: drupal.star.bnl.gov/STAR/system/files/CosmicAdc_small_Day056.pdf
Those plots seem to indicate that most of the time, when there is a TOF-BBC trigger, there is nothing in the EPD!
I have begun to look at the data offline, as the files have been processed to muDsts. There are thousands of events, but so far I have only looked at a few hundred, for non-interesting reasons. However, my study thus far, confirms the finding above.
In every event, there is always one (and only one) BBC tile that fires (i.e. ADC>20). In most events, there are no EPD tiles that fire (ADC>5). Sometimes one or more East EPD tiles fire, and sometimes one or more West EPD tiles fire. Never (in the limited set I've looked at so far) do East and West EPD tiles fire simultaneously.
The two plots below show the multiplicity of East (negative x-axis) and West (positive x-axis) EPD tiles that fire, when it is an East (top plot) or West (bottom plot) BBC tile that fired. At least there seems to be a mild correlation-- when a signal is seen in the East (West) EPD, it is usually associated with a signal in the East (West) BBC. But
- even that correlation is not perfect! There are a couple of events in which EPD sees East and BBC sees West and vice-versa
- more importantly, usually the EPD sees nothing at all!
I will look at this with higher statistics and in a little more detail, but there is clearly a problem. It must be one of timing. No way is this an "efficiency."
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