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Description
Summary
Experiments at the VEPP-2000 e+e- collider with upgraded SND detector have been started in the Budker Institute of Nuclear Physics (Novosibirsk, Russia) in 2010. The designed parameters of VEPP-2000 are the following: center-of-mass energy is up to 2 GeV, luminosity is 10^32 cm^-2s^-1. Development of the new particle identification system based on the threshold aerogel Cherenkov counters was a part of the SND upgrade. The counter design is based on ASHIPH technique (Aerogel, SHifter, PHotomultiplier). Cherenkov light emitted in aerogel is collected by a wavelength shifter, re-emited and transported to the photocathode. A microchannel plate photomultiplier tube (MCP PMT) with multialkali photocathode is chosen as a photodetector.
For the particle identification at different energies two systems with different refractive indexes of aerogel were manufactured: with n=1.13 for the separation of pi and K mesons up to particle energy of 1 GeV and with n=1.05 for e/pi separation up to particle energy of 0.45 GeV.
The system with n=1.13 was calibrated with particles (e, mu, pi, K) produced in e+e- collisions. The signal magnitude from ultrarelativistic electron is 6-8 photoelectrons. This system provides pion suppression by more than two orders of magnitude in the momentum range from 0.35 to 1.00 GeV/c.
The measurements of characteristics of system with n=1.05 have been done using particles from e+e->e+e- and e+e->mu+mu- reactions. The average signal from electrons is 3.5 photoelectrons.
