The GlueX Start Counter Detector

Abstract

The design, simulation, fabrication, calibration, and performance of the GlueX Start Counter detector is described. The Start Counter was designed to operate at integrated rates of up to 9 MHz with a timing resolution in the range of 500 to 825 ps (FWHM). The Start Counter provides excellent solid angle coverage, a high degree of segmentation for background rejection, and can be utilized in the level 1 trigger for the experiment. It consists of a cylindrical array of 30 thin scintillators with pointed ends that bend towards the beam line at the downstream end. Magnetic field insensitive silicon photomultiplier detectors were used as the light sensors.

First Measurement of Near-Threshold J/ψ Exclusive Photoproduction off the Proton

“…A 30 cm-long liquid hydrogen target is placed inside the solenoid. A scintillating start counter surrounding the target helps to select the beam bunch [18]. Charged particle reconstruction around the target is performed by the Central Drift Chamber (CDC), consisting of straw tubes grouped in 28 layers with axial and stereo orientation.…”

Beam asymmetry Σ for the photoproduction of η and η′ mesons at EγAdhikari1, Ali2, Amaryan3 et al. 2019Phys. Rev. CSelf Cite19270View full textAdd to dashboardCite

“…Inside the bore of the solenoid, the incident photons interact in a 30-cm-long liquid-hydrogen target that is located 65 cm from the upstream end of the solenoid. The target is surrounded by a scintillator-based start counter (ST) that records the time of charged particles [16] and a central drift chamber (CDC) that contains 28 layers of 1.5-m-long 1.6-cm-diameter straws arranged in axial and stereo orientations [17]. Downstream of the CDC and at forward angles are four planar packages of forward drift chambers [18,19].…”

Measurement of the photon beam asymmetry in γ⃗p→K+Σ0 at EγAdhikari1, Ali2, Amaryan3 et al. 2020Phys. Rev. CSelf Cite6060View full textAdd to dashboardCite

“…The photon beam passes through a collimator in order to suppress the incoherent part, a triplet polarimeter [13] and a pair spectrometer [14], which provide continuous, non-invasive measurements of the photon beam polarization and the relative flux, respectively, before reaching the liquid hydrogen target. The target is surrounded by a scintillator start counter [15], a straw-tube central drift chamber [16] and a lead and scintillating-fiber barrel calorimeter [17], all inside the bore of a superconducting solenoid. Four sets of planar wire drift chambers [18] are also located inside the solenoid, downstream of the central drift chamber.…”