HPS – ECal Detector - TECHNICAL PARAMETERS The experimental apparatus includes two main detectors: a silicon vertex tracker (SVT) for precise momentum vertex determination and and an electromagnetic calorimeter (ECal) to trigger on e + e - pairs produced by A’ decay. The ECal consists of 442 lead-tungstate PbWO4 crystals (16 cm long, tapered, with front/back face of 1.3x1.3/1.6x1.6 cm 2 ) with avalanche photodiode (APD) readout and on-detector amplifiers. The Heavy Photon Search (HPS) is an experiment proposed for Jefferson Laboratory to search for new heavy vector boson(s), "dark photons”, in the mass range of 20 MeV/c2 to 1000 MeV/c2. HPS uses both invariant mass and separated decay vertex signatures using a compact, large acceptance forward spectrometer. After a test run in Spring 2012, the full HPS experiment, capable of searching for heavy photons over a wide and unchartered region in parameter space, is currently running. PARAMETERDESIGN VALUE HPS-ECal Calorimeter typePbWO4, homogeneous Crystal number and size442, tapered 15x15 (front) 16x16 (back) x160 mm 3 Readout sensorsHamamatsu LAAPD s Working Temperature T = 20 o C (  T ≤ 0.5 o C) HPS-SVT Tracking technology Silicon microstrips, single-sided, 60  m sense pitch Detector type6 layers, axial + stereo Spatial resolution  X,  Y ≤ 10  m Expected Performance VALUE Azimuthal angular coverage1.0 o to 5.0 o EM shower energy rangeE max –E min = (0.5 – 5.0) GeV Energy resolution  E /E ≤ 4.5 %/√E(GeV) ⊕ 1% Vertex resolution  X,  Y ≤ 300  m Time resolution≤500 ps

Contact: M. Battaglieri, Detector Co-lead +39 R. De Vita, Detector Co-lead L. Elouadrhiri, Control Account Manager G. Young, Associate Project Manager for Physics V. D. Burkert. Hall B Group Leader ) Construction Strategy and Project Leadership: –Project is lead by INFN-GE (IT) (lead scientists M.Battaglieri and R. De Vita) and includes University of Edinburgh (UK), CEA-Saclay (Fr), Ohio University, James Madison University, Norfolk State University. –The mounting and testing of the three components of the FT will take place in Genova (FT-Cal), Edinburgh (FT-Hodo) and Saclay (FT-Trck). –The whole FT will be assembled in Genova and after testing the full functionality, will be shipped to JLab. Project Status The FT-Cal and FT-Hodo designs are firm, while the FT-Trck design is being finalized. An FT prototype, including a calorimeter and a hodoscope, was tested at JLab and BTF at LNF (Italy). All the main components of the FT-Cal have been procured and tested (PbWO crystals, APD, FE electronics). Procurements of the FT-Hodo components is close to completion. Assembly of the detectors has started. The design of the FT mechanical structure has been completed: parts have already been machined or ordered. A benchmark bed is being set-up in Genova for the full FT functionality tests planned for summer Significant dates –FT-TDR released in December 2012 –First components of the FT delivered in Summer 2013 –FT-Cal crystals QA in May 2014 –Assembly of the FT-Cal and FT-Hodo started in January 2015 –Full FT assembly and test in Genova expected in summer 2015 –FT shipping at JLab expected in fall 2015 Last modified: February 6, 2015