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The Heavy Photon Search Group at SLAC is collaborating with physicists at Jefferson Lab, Fermilab, and UCSC in two experiments aimed at discovering a hidden-sector, heavy photon. Such a particle would have mass in the range 0.02 to 1.0 GeV, couple weakly to electrons, and decay to e^e⁺e^-. It would be produced by electron bremstrahlung on a heavy target, and be identified as a narrow e⁺e^-^ resonance. Weak couplings of this heavy photon to electrons account for its having not yet been discovered and can give rise to separated vertices in its decay, providing a spectacular signature. Heavy photons have become a hot topic recently because they may explain high energy electrons and positrons in cosmic rays and be intimately linked to dark matter annihilation.

Our primary effort at SLAC is the Heavy Photon Search experiment (HPS). During the past year, we proposed the HPS Experiment to JLab. Its first stage, the HPS Test Run, has been approved and funded. The HPS Collaboration is hard at work completing designs, building electronics, and beginning construction of the experiment, which will be installed March 2012 at JLab. The experiment will use LHC style readout of silicon microstrip detectors for tracking and vertex reconstruction of e^e⁺e^-^ pairs and a PbWO₄ crystal calorimeter to deal with the extremely high trigger rates expected. HPS offers many opportunities for rotation students. Experimental design and simulation studies will continue, tracking pattern recognition and vertexing code is being refined, the data acquisition system for the experiment is being designed and tested, a silicon tracker/vertexer is being built, and the physics analysis is being developed. This experiment is very small by modern standards, but exploits cutting edge detection and readout technologies to address a very fascinating piece of physics. It provides a perfect opportunity for a thesis student, offering all aspects of experimental work, from design to hardware implementation to data analysis. Some specific proposals for Fall 2011 HPS rotation projects are listed below.

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