 


r5  21 Apr 2006  16:11  GeorgSchepers 

r4  20 Apr 2006  16:15  GeorgSchepers 

 








Purpose 

Purpose 



the DIRC provides 

the DIRC provides 



 a positive kaon identification
 a destinction of gammas and relativistic charged particles entering the EMC behind him


 a positive kaon identification
 a destinction of gammas and relativistic charged particles entering the EMC behind him




Working principle 

Working principle 



 Cherenkov Detector
 determination of the mass of the particle by combining his velocity information with momentum information from the tracking detectors


 Cherenkov Detector
 determination of the mass of the particle by combining his velocity information with momentum information from the tracking detectors




Important values 

Important values 



 Polar angle vs. momentum distribution of the kaons in radiative decays of resonances in formation experiments like J/psi > K+K gamma for the search of glueballs (Ref. TPR):


 Polar angle vs. momentum distribution of the kaons in radiative decays of resonances in formation experiments like J/psi > K+K gamma for the search of glueballs (Ref. TPR):




" 

" 



 the barrel DIRC covers the solid angle of 22 to 140 degrees
 the lower momentum threshold for kaons which produce Cherenkov light is for an envisaged refractive index of n=1.47 as low as 460 MeV/c (for single photon producton  for photon numbers bigger than 4 it is more than 200 MeV/c higher)


 the barrel DIRC covers the solid angle of 22 to 140 degrees
 the lower momentum threshold for kaons which produce Cherenkov light is for an envisaged refractive index of n=1.47 as low as 460 MeV/c (for single photon producton  for photon numbers bigger than 4 it is more than 200 MeV/c higher)










FIRST Estimations: 

FIRST Estimations: 



 Single Photon Cherenkov Angle Resulution


 Single Photon Cherenkov Angle Resulution




 with a DIRCBar size of 17x30x2000mm, a distance of l=1.20m of the photomultipiers from the bar exit and a diameter of the photomultiplier cathods of 2cm ( beeing equal to the distance of the centers of the cathods) the geometric contribution of the Single Photon Cherenkov Angle Resulutioncan be calculated and lies in the order of magnitude of 10mrad


 with a DIRCBar size of 17x30x2000mm, a distance of l=1.20m of the photomultipiers from the bar exit and a diameter of the photomultiplier cathods of 2cm ( beeing equal to the distance of the centers of the cathods) the geometric contribution of the Single Photon Cherenkov Angle Resulutioncan be calculated




 to this geometric contribution the resolution contribution (comming from the production and the transmission dispersion) has to be added which has a values of similar size


 to this geometric contribution the resolution contribution (comming from the production and the transmission dispersion) has to be added which has a values of similar size




 GeorgSchepers  20 Apr 2006 

 GeorgSchepers  20 Apr 2006 







 


r5  21 Apr 2006  16:11  GeorgSchepers 

r4  20 Apr 2006  16:15  GeorgSchepers 

 