Acceptance of ET_8 tagger in 2000.

V.Andreev, 10-November-2000

     The acceptance of ET_8 calorimeter was calculated with the same
 procedure which was used in previous years for this purpose. More
 details about the calorimeter design, performance, procedure of
 acceptance determination and obtained results during 1998-1999  HERA
 Luminosity Runs are described in the H1 note.  

     The 2000 H1 running period was divided on 14 data sets differed
 mainly by the X_off position and the tilt of the electron beam
 in the interaction point. The list of these samples is shown below:

 TransActID  Rtyp  Dtyp  1.Run     Words    Author      Date
    
    2647939  e-p   data  262200     103    vladimir    001107  
    2647940  e-p   data  263381     103    vladimir    001107
    2647941  e-p   data  264001     103    vladimir    001107   
    2647942  e-p   data  264901     103    vladimir    001107  
    2647943  e-p   data  266031     103    vladimir    001107 
    2647944  e-p   data  267101     103    vladimir    001107   
    2647945  e-p   data  267801     103    vladimir    001107  
    2647946  e-p   data  269681     103    vladimir    001107  
    2647947  e-p   data  272200     103    vladimir    001107  
    2647948  e-p   data  272317     103    vladimir    001107   
    2647949  e-p   data  274881     103    vladimir    001107  
    2647950  e-p   data  275801     103    vladimir    001107    
    2647951  e-p   data  277601     103    vladimir    001107   
    2647952  e-p   data  278641     104    vladimir    001107    

 After the DB was updated with these new set of LET2 banks.
 The y-dependence of ET8 acceptance for the different run range
 is shown on the next picture.

     The systematic error is formed by the next sources:

     a) precision of the electron energy scale          --> 4.5 % ,
    
     b) uncertainty in the ET-8 position with respect
        to the electron beam                            --> 4.0 % ,
     
     c) trigger efficiency determination                --> 1.0 % ,

     d) fitting procedure and averaging of the
        calibration samples                             --> 1.5 % .

 So the overall systematic error in the acceptance determination
 of the ET-8 in 2000 could be taken as 6.3 % .

P.S.   One could  point out that starting from 272317 up to 278641 H1 runs
       the degradation of ET_8 response was observed. This led to 
       the essential increasing of effective trigger threshold and 
       decreasing ET_8 trigger rate. Take into account this at 
       your analysis.

P.P.S. The background events from p-bunches  and "useful" events from
       ep-collided bunches are differed by response time in ET_8 tagger. 
       It is possible to reduce this  background only up to few percent
       level by the hardware. The reconstruction procedure removed this
       weakness to put negative value to the error of reconstructed
       energy of ET_8 in this kind of events.