The TOFW is a time-of-flight (TOF) detector in the west (W) arm of the PHENIX central spectrometer. It was designed, developed, and assembled at Vanderbilt University with Julia Velkovska as the project lead. It was installed prior to the beginning of Run7 and was successfully operated for all running periods thereafter.
The individual component of the TOFW detector is the mult-gap resistive plate chamber (MRPC). Each MRPC has six 230 micron gaps separated by glass plates. The gaps are filled with a gas mixture.
At either side (longitudinally) of the gaps are electrodes held at +/- 7 kV for a total potential difference of 14 kV across the gaps. Outside of the electrodes on either side (longitudinally) are sets of four copper strips that are read out on either side, for a total of 8 readout channels per MRPC. When charged particles cross the gap, the gas is ionized. The charge in the gas is imaged in the strips. The induced charge in the strips is read out on either end (transversely). Each strip is about 37 cm long and 2.8 cm wide. The lengthwise location of the hit in the strip is determined via the difference in time on either end. Since the strip is only 1 inch wide, the widthwise location of the hit is taken to be the center of the strip.
The TOFW system consists of four boxes. Each box subtends 11.5 degrees in azimuth and 0.35 units in pseudorapidity. There are two boxes in sector 1 and two boxes in sector 2, with each sector receiving full coverage in pseudorapidity and half coverage in azimuth. Each box has four high voltage busses in two rows. Each high voltage buss powers 8 MRPCs, for a total of 32 per box and 128 total, meaning there are 1024 readout channels in total.
These “get” methods give access to the TOFW variables used for analysis. The variable type, name of the get method, and a brief description are given below.
|short||get_tofwid||Ron needs to double check|
|float||get_ptofwx||x-component of the projection of the cgl track onto the TOFW|
|float||get_ptofwy||y-component of the projection of the cgl track onto the TOFW|
|float||get_ptofwz||z-component of the projection of the cgl track onto the TOFW|
|float||get_pltofw||pathlength of the track from the collision to the TOFW|
|float||get_tofwdphi||difference between track projection and the track hit in the phi direction (viz dphi means delta phi)|
|float||get_tofwdz||difference between track projection and the track hit in the z direction (viz dz means delta z)|
|int||get_striptofw||the unique id number of the strip of the track hit|
|float||get_tofwx||x-component of the TOFW track hit|
|float||get_tofwy||y-component of the TOFW track hit|
|float||get_tofwz||z-component of the TOFW track hit|
|float||get_ttofw||time of flight from the vertex to the TOFW (the BBC start time for the event is subtracted)|
|float||get_qtofw||the total charge (ADC) of the TOFW track hit|
|float||get_tofwadcup||the charge (ADC) from the upper side of the TOFW track hit|
|float||get_tofwadcdw||the charge (ADC) from the lower side of the TOFW track hit|
|float||get_tofwtdcup||the raw time (TDC) from the upper side of the TOFW track hit|
|float||get_tofwtdcdw||the raw time (TDC) from the lower side of the TOFW track hit|
|float||get_tofwsdz||the sigmalized version of tofwdz|
|float||get_tofwsdphi||the sigmalized version of tofwdphi|
|float||get_m2tofw||the calculated mass squared of the TOFW track (using ttofw, pltofw, and mom)|
|int||get_idtrk_tofw||Ron needs to double check|
|short||get_stofwid||Ron needs to double check|
|float||get_sptofwx||swapped version of ptofwx|
|float||get_sptofwy||swapped version of ptofwy|
|float||get_sptofwz||swapped version of ptofwz|
|float||get_stofwdphi||swapped version of tofwdphi|
|float||get_stofwdz||swapped version of tofwdz|
|float||get_stofwsdphi||swapped version of tofwsdphi|
|float||get_stofwsdz||swapped version of tofwsdz|