ePIC pfRICH mailing list

["Kiselev, Alexander" <ayk AT bnl.gov>]

  Hello colleagues,

  yesterday I incorporated Belle II aerogel parameterizations provided by Luka into the standalone GEANT simulation, and it may happen that an important transition feature from ATHENA to ePIC configuration was overlooked. Here is a qualitative assessment, to trigger a discussion. A detailed quantitative study should better be done by Chandra once he is back.

  Belle II aerogel seems to be much more "transparent" than a CLAS12 one in a deep UV range, in terms of the Rayleigh scattering. Nitrogen is fully transparent. HRPPD quartz windows are UV grade, transparent down to ~170nm. HRPPD photocathode was specifically tuned for the UV range, as we know.

 

  This essentially means that removing the acrylic filter, and using HRPPD UV-enhanced QE curve "as is", without any further "blue shift" tuning, with a single 2cm thick Belle II "Aerogel1" (n ~ 1.045) layer one is getting Cherenkov photons down to ~200nm or so, with <Npe> ~ 15+ and overall Cherenkov angle resolution <1 mrad (sigma of a gaussian fit). Unless I overlook something obvious. Then what would this be, conceptually?

  If this preliminary assessment is correct, pfRICH+HRPPD combination is kind of unique. dRICH would suffer from chromatic effects at small wave lengths. mRICH has a built in acrylic filter, which effectively removes photons below 300-350nm (the actual cutoff is not known yet). SiPMs have QE~0 below ~400nm (unless one can make use of the NUV ones).

  Comments?

  Regards,

    Alexander.