The Heavy Photon Search test detector

Abstract

a b s t r a c tThe Heavy Photon Search (HPS), an experiment to search for a hidden sector photon in fixed target electroproduction, is preparing for installation at the Thomas Jefferson National Accelerator Facility (JLab) in the Fall of 2014. As the first stage of this project, the HPS Test Run apparatus was constructed and operated in 2012 to demonstrate the experiment's technical feasibility and to confirm that the trigger rates and occupancies are as expected. This paper describes the HPS Test Run apparatus and readout electronics and its performance. In this setting, a heavy photon can be identified as a narrow peak in the e þ e À invariant mass spectrum above the trident background or as a narrow invariant mass peak with a decay vertex displaced from the production target, so charged particle tracking and vertexing are needed for its detection. In the HPS Test Run, charged particles are measured with a compact forward silicon microstrip tracker inside a dipole magnet. Electromagnetic showers are detected in a PbW0 4 crystal calorimeter situated behind the magnet, and are used to trigger the experiment and identify electrons and positrons. Both detectors are placed close to the beam line and split top-bottom. This arrangement provides sensitivity to low-mass heavy photons, allows clear passage of the unscattered beam, and avoids the spray of degraded electrons coming from the target. The discrimination between prompt and displaced e þ e À pairs requires the first layer of silicon sensors be placed only 10 cm downstream of the target. The expected signal is small, and the trident background Contents lists available at ScienceDirect

Lepto-philic 2-HDM + singlet scalar portal induced fermionic dark matter

“…This UV complete model with an extra singlet scalar ∼ < 10 GeV successfully explains the existing 3 σ discrepancy of muon anomalous magnetic moment and is consistent with the constraints on the model parameters from muon and meson decays [14][15][16][17]. These results have been analysed for 0.01 GeV < m S 0 < 10 GeV when compared with those for the singlet neutral vector Z searches at B factories such as BaBar [18], from electron beam dump experiments [19] and electroweak precision experiments [20] etc.…”

Hunting all the hidden photons

“…In addition to the beam dumps discussed above we also consider fixed target experiments [29] such as APEX [32], A1/MAMI [30,38], HPS [39], NA64 [45], VEPP-3 [35] and DarkLight [36,40]. Here, production is typically via Bremsstrahlung, too.…”

A light complex scalar for the electron and muon anomalous magnetic moments

“…1 (a). The JLab experiment HPS [76] projection for scalars [68] is plotted as a region bounded by the dot-dashed dark cyan line as well.…”

“…(a): The parameter space (g e φ I , m φ I ) for ∆a e and the constraints from different experiments. The shaded orange region is from beam dump experiment [67,68] and the dot-dashed dark cyan contour area is from future projection for HPS [68,76]. The collider limits include shaded green region searching for e + e − → γφ at BaBar [78], shaded purple region from KLOE [81,82] and Belle-II projection [68,79] which is shown in dot-dashed green contour region.…”