" The relationship between signal-to-noise ratio and b tag efficiency: 
         How long can silicon detectors survive radiation exposure ? "

      J. Albert, R. Culbertson, D. Glenzinski, J. Incandela, E. Kajfasz, 
		N.M. Shaw, F. Snider, D. Stuart, M.J. Wang

				Abstract

In run 1A (1992-93) there was an apparent correlation between reduced b tag 
efficiency and increased radiation damage to the CDF dc-coupled silicon 
detector (SVX). We use the Monte Carlo (MC) simulation created for the new CDF 
ac-coupled detector (SVX') to study this correlation. This is accomplished by 
scaling the signal size and adding noise and pedestal shifts in the MC to 
match the operating characteristics of the SVX at various points throughout 
run 1A. We then compare bb MC tag rates to those measured in run 1A inclusive 
electron data of which an estimated fraction F_b=0.37 +/- 0.08 are bb events. 
We find that the MC reproduces well the silicon detector position resolutions 
and the trend in b tag rates. We measure the run 1A ratio of b tag 
efficiencies in inclusive e data and bb MC to be S(1A) = 0.97 +/- 0.03 (stat). 
We next use parametrizations of the expected noise behavior of the SVX' 
detectors to predict the relative b tag efficiency as a function of further 
integrated luminosity in the current run (run 1B).  We find that SVX' will 
retain full b tag capability down to a signal-to-noise ratio of ~ 5, 
corresponding to an integrated luminosity of at least 250 pb-1 and possibly 
as high as ~ 700 pb-1. A similar calculation for the effect of radiation 
induced shot noise in the planned upgrade detector (SVX II) indicates that 
this component of noise will not be large enough to affect the b tag efficiency 
up to integrated luminosities in excess of ~ 4 fb-1.
 
Posted to CDF$PUB:CDF3338_BTAG_EFF_VS_SNR.PS
Posted by FNALE::INCANDEL