Timing Properties of T0 Detectors At PHOBOS. Saba Zuberi, Erik Johnson , Nazim Khan, Frank Wolfs, Wojtek Skulski University of Rochester. OUTLINE. Brief introduction to PHOBOS Particle ID and why the timing properties of T0s are important? Time of Flight (TOF) Detector
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Erik Johnson, Nazim Khan, Frank Wolfs, Wojtek Skulski
University of Rochester
PHOBOS Physics Aim: To investigate properties of hadron
production at extreme energy densities.
(eg. p/K separation: 0.6GeV/c)
TOF detector extends particle ID to higher momentum region.
With TOF: p/K separation: 0.6GeV/c to 1.2GeV, K/p separation: 1.2Gev/c to 2GeV (L=1.7m,sTOF=100ps)
TOF Wall determines time of arrival.
Accuracy of arrival time and collision time measurements determine sTOF.Determining Time-of-Flight
Each TOF wall consists of 120 scintillation slats 0.8x0.8x20cm3, coupled to two PMTs (top and bottom).
Position of incident particles is determined and allows spectrometer tracks to be matched with TOF hits.
Cerenkov radiators, 50mm in diameter, coupled to fast PMTs.
Cerenkov radiation is produced when charged particles in a medium have a velocity faster than the speed of light in that medium.
Ten detectors in a ring on either side of collision point.
Can determine the collision point to within 50mm.
T0 DetectorsTOF Walls
T0 Counters installed at RHIC
TOF Wall installed at RHIC
For larger supply voltage, T0 detectors have larger gain and provide larger signals.
Expect timing resolution, sTO to improve with increased voltage.
To avoid saturation of PMTs operate at as low a voltage as possible without sacrificing sTO.
Determine dependence of T0 timing resolution, sTO on supply voltage and optimum operating voltage.Dependence of T0 Timing Resolution on Supply Voltage
Dependence of T0 Timing Resolution on Position of Incident Particles
Timing properties were studied using cosmic rays. provide larger signals.
Two 0.8x0.8x0.8cm3 plastic scintillating detectors used to confine position of incidence and provide start time in timing measurements.
Supply voltage of the start detectors is kept constant and T0 voltage is varied.
Position scan conducted in two ways:
The vertical distance between the detectors remained constant.Experimental Setup
At -2700V achieved a 55ps resolution.
The testing system has an intrinsic resolution of ~50ps.Result: Timing Resolution vs. Supply Voltage
No significant variation in T0 timing resolution was observed either across the diameter of the detector, or around its circumference.Result: Timing Resolution vs. Position of Incident particles
The timing resolution of the TOF subsystem limits the particle id capabilities in high momentum region.
The T0 timing resolution is found to have little dependence on the position of incident particles.
Verified that the most effective operating voltage for the T0s is -2700V, where sT0 = 55ps.
Beyond –2700V the supply voltage does not influence the timing resolution of the T0 counters.Summary