From: Flemming Videbaek (videbaek@rcf.rhic.bnl.gov)
Date: Wed Jul 30 2003 - 19:44:28 EDT
Hi This mail will not have plots attached. During the investigations of the D4 response I have run into a problem which I belive is sub-performance of the digitization/local tracking of the DC. I setup the reco of geant track->detectortrack as Peter is doing for the acceptance. Further I set the positon resolution in the DC dig. to 0. I therefore expected to get the geanthit/track back with high accuracy, but it is not so. A good fraction has 'bad' xpos,ypos and slopes with momenta difference after matching through D4 (eff ege) of up to 1-2%. I do not know why this happens, but I do not shink it should. At least to me it pu into doubt the accuracy of this stuff.The spectrum is a nice peak on top a rather flat background. I am pretty sure it is connecte to the DC digi/local tracking. If I require that the geant x,alphax .. is close to those of the geant input the reconstructed momenta is precisely what you want that is dp/p. Can anyone look into this and explain the problem? regards Flemming -- Flemming Videbaek Brookhaven National Laboratory Physics Department tlf 631-344-4106 fax 631-344-1334 e-mail: videbaek@bnl.gov
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