Methods for optical calibration of the BigBite hadron spectrometer

Abstract

The techniques for optical calibration of Jefferson Lab's large-acceptance magnetic hadron spectrometer, BigBite, have been examined. The most consistent and stable results were obtained by using a method based on singular value decomposition. In spite of the complexity of the optics, the particles' positions and momenta at the target have been precisely reconstructed from the coordinates measured in the detectors by means of a single back-tracing matrix. The technique is applicable to any similar magnetic spectrometer and any particle type. For 0.55 GeV/c protons, we have established a vertex resolution of 1.2 cm, angular resolutions of 7 mrad and 13 mrad (in-plane and out-of-plane, respectively), and a relative momentum resolution of 1.6 %.

First measurement of unpolarized semi-inclusive deep-inelastic scattering cross sections from a He3 target

“…The scattered electrons were recorded by the BigBite spectrometer [37][38][39] and the electroproduced pions (π ± ) were recorded by the High Resolution Spectrometer (HRS) [40]. To study the unpolarized SIDIS processes, the data with opposite polarization states were combined.…”

“…The trigger was formed by summing the signals from the preshower and shower calorimeters. The preshower and shower energy deposition with the reconstructed momentum were utilized for the particle identification (PID) in the BigBite [37][38][39]42].…”

Measurement of the Target-Normal Single-Spin Asymmetry in Deep-Inelastic Scattering from the Reaction He3↑(e,Katich1, Qian2, Zhao3 et al. 2014Phys. Rev. Lett.Self Cite300180View full textAdd to dashboardCite

“…Scattered electrons were detected using the Hall A BigBite detector package [21] at þ30°(beam-right) and the left Hall A high resolution spectrometer (LHRS) at −16° [22]. The BigBite package includes a dipole magnet for momentum separation, three sets of multiwire drift chambers for track reconstruction, and a lead-glass electromagnetic calorimeter for particle identification (PID) with preshower and shower layers sandwiching a scintillator plane for providing timing information.…”

Measurement of Double-Polarization Asymmetries in the QuasielasticHe→3(e<

“…The total systematic uncertainty (all items added in quadrature) is 7% (relative). The resolution in p m is driven mostly by the relative momentum resolution of BigBite, which is ≈2% for all momenta [29], while the contribution of the ω resolution (2.2 × 10 −4 ) is negligible. Hence, the kinematic dependence of the systematic uncertainties is very small, and the possible smearing of the asymmetries has been excluded.…”

“…The ejected deuterons and protons were detected by the large-acceptance spectrometer BigBite, equipped with a detector package optimized for hadron detection [29], consisting of a pair of multiwire drift chambers used for tracking and two scintillator planes used for triggering, time-of-flight determination, and particle identification.…”