From: W.J. Llope (llope_at_physics.rice.edu)
Date: Thu Apr 17 2003 - 11:53:15 EDT
hi zhangbu - thats an example of an 'inferential' calibration,
and in tofp we generally try to avoid those in favor of direct
calibrations...
the way i would do this instead (i haven;t tried this but
it may have a shot) is to skip your step #1...
then on the stop side one could employs the usual iterative approach
and try to minimize the dependence of 1/beta for pions on
the trio of variables (tofrADC,Zhit,pvpdADCi), where pvpdADCi
is the ADC value of the single pVPD ch that fired in this
event. messier - but might work almost as well as w/
an actual start correction, *if* theres *lots* of stop-side
hits in each TOFr ch... i.e. you'd need more data per ch than
we got in the dAu run for sure.... worth thinking about though...
it's great that you think the deadtime/rates w/ 1.and.1 are
tolerable... i agree that's probably our best choice..
regards...
At 5:00 PM -0400 4/16/03, Xu, Zhangbu wrote:
>Hi, Bill & Frank:
> I think we should keep the current setting with 1.and.1.
>However, if we want to run 1.OR.1, we can still correct for
>the slewing effect since this effect is carried in the
>TOFr TDC. Here is an example of how we can correct for the
>slewing effect if only one pVPD fires:
>1) select those events which have at least two pVPD hits,
> do the slewing curve from those events for pVPD,
>2) Apply this slewing function to the Delta function
> treated it as if it were a valid TDC.
>3) Do
> TDC_TOFr-(TDC_pVPD)_after_slewing_correction
>
>This will give us the right slewing correction for pVPD.
>
>On the issue of 1.and.1 rate:
>The maximum interaction rate is about 400K Hz, this results
>in pVPD 1.and.1 rate of 40K Hz (1/50us). Our daq fast clear
>is 5us, so we will have 10% deadtime effect. However, I use the
>busy to veto the trigger and this effect will go away. So
>we should not have problem even at the highest pp rate.
>
>Thanks!
> Zhangbu
>-----Original Message-----
>From: W.J. Llope
>To: startof-hn_at_www.star.bnl.gov
>Sent: 2003-4-16 15:16
>Subject: Re: TOFr TDC range
>
>that's becuase running 1.OR.1 is really not that productive....
>this will collect a lot of data w/ a single lit channel in the
>pVPD. this makes the TDC dist for this channel in those events
>a delta function by definition, and a direct start slewing
>corrrection is thus not possible by definition.
>1.AND.1 is the minimum, most open, local trigger we can
>run and still do corrected timing....
>
>there is however the possibility that we will want to run
>2.AND.2 during the TOF-triggered data collection here in run-3
>pp collisions.
>the 1.and.1 rates may be too much for the DAQ (?). 2.and.2
>would drop the rate by a big factor, and also lead to
>somewhat better start resn (because of averaging) over the
>sample of triggered events.... rgds
>
>>
>>cheers,
>>frank
>>
>>
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--W.J. Llope, Ph.D. Res. Assoc. Professor T.W. Bonner Nuclear Laboratory phone: 713-348-4741 Rice University, MS-315 fax: 713-348-5215 6100 S. Main St. Houston, TX 77005-1892 e-mail: llope_at_physics.rice.edu WWW home: http://wjllope.rice.edu/default.html
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