Bjorrn, Your plots are interesting in more ways than indicated below. a) Why is the p1 coeef in the first plot .93 +-.002 It really should be one since it is a distance beasured both places. Since the ZDC time calibration is probably known to better the 7% (I assume) it sounds like a problme in the tracking - What pad pitch did you use? At some earlier stages we have also seen a small change in the projected y-pos with 'z' so maybe some small geometry problem still exsists? b) Is the deviation in the ZDC-TPM1 vs mult similar to that of the BB? This could help isolate the problem. c) You would probably be better off making a cut on ZDC energies + a rough BB cut to resolve the double value problem. THis should be mainly for conformation. Pong -(: ------------------------------------------------------ Flemming Videbaek Physics Department Brookhaven National Laboratory tlf: 631-344-4106 fax 631-344-1334 e-mail: videbaek@bnl.gov ----- Original Message ----- From: "Bjorn H Samset" <bjornhs@rcf.rhic.bnl.gov> To: "BRAHMS Software list" <brahms-dev-l@bnl.gov> Sent: Wednesday, March 21, 2001 3:29 AM Subject: Re: ZDC Vertex > On Tue, 20 Mar 2001, Michael Murray wrote: > > > Dear Bjorn, > > although the Z vertex distirbution is very > > wide if we have enough events it should be possible to find > > a well defined mean z for the the ZDC and TPM1. Thus a profile > > plot, with option ' ' for error on mean, of Z versus multiplicity > > would be useful. Thanks for helping on this. > > My pleasure :-) > > I have made a few quick plots - have a look at > www.fys.uio.no/~bjornhs/ZDCvsTPM1_profile.ps > www.fys.uio.no/~bjornhs/ZDCvsTPM1_DiffVsMult.ps > > The first one is simply ZDC vs TPM1 showing a nice linear rel. over at > least z=pm35cm. > > The second one is more interesting - as requested, a profile of > Z_ZDC-Z_TPM1 vs multiplicity (I have used BB_Mult because that was easiest > from my tree - if you think that this causes a problem I can redo for some > other mult-version). As you can see there really seems to be a > mult-dependence on the difference - it is well fitted by a 2nd order > poly. As of yet I have no ide as to the reason for this - I'll have a more > thorough look at the TPM1 Vertex output to see if there is anything there > that might cause problems, otherwise I guess slewing corrections are a > good place to start. My data are from runs 2529, 2530, 2531, 2535. > > I'll check this better during the day... Ping :-) > > ------------------------------------------------ > Bjorn H. Samset > Master-student in Heavy Ion physics > Mob: +47 92 05 19 98 Office: +47 22 85 77 62 > Adr: Kri 2A709 Sognsveien 218 0864 Oslo > >
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