One of the important features of PHENIX experiment is capability of particle identification (PID). High resolution time-of flight counter (TOF), ring-imaging Cerenkov counter (RICH) and Pb-Sc. electromagnetic calorimeter (EMCal) with timing measurement capability provides PID as shown in upper two rows of Fig.1. TOF is limited to moderately low , while at high RICH provides pion identification. Clearly, within the present TOF & RICH configuration has significant hole of PID.
New features found in the first RHIC data has brought people's attention to an importance of particle identification in the region above 2 GeV/c. The addition of an aerogel Cerenkov counter with an index of refraction of 1.01 will provide PID of pion, kaon, and proton separation seemlessly upto of almost 10 GeV/c as illustrated in Fig.1.
Aerogel Cerenkov counter with limited acceptance will be installed on the West Arm. Geometrical size of the entire counter will be and is segmented to cells. According to current prototype design, each cell has of aerogel (refractive index of ) followed by an integration cube viewed by two 3'' PMT's (left of Fig.2).