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The Heavy Photon Search Group at SLAC is collaborating with physicists at Jefferson Lab, Fermilab, UCSC, INFN in Italy, and Orsay and Saclay in France in an experiment aimed at discovering a hidden-sector , or "heavy"  photon. Such a particle would have mass in the range 0.02 01 to 10.0 3 GeV, couple weakly to electrons, and decay to e+e-. It would be produced by in electron bremstrahlung bremsstrahlung on a heavy target, and be identified as a narrow resonance. The very weak couplings of the heavy photon to electrons account for its having not yet having been discovered and can would give rise to separated vertices in its decay, providing a spectacular signature.

Heavy photons have become a hot topic because they may explain the abundance of high energy electrons and positrons in cosmic rays and be intimately linked to hidden sector dark matter and the existence of hidden sectors. Our , an interesting alternative to the SUSY wimps which no one is finding. Our primary effort at SLAC is the Heavy Photon Search experiment (HPS). During 2011 and 2012, we built, installed, commissioned, and ran the HPS Test Run Experiment at JLab during Spring 2012. The experiment used LHC style readout of silicon microstrip detectors for tracking and vertex reconstruction of e+e- pairs and a PbWO₄ crystal calorimeter to deal with the extremely high trigger rates expected. The run successfully demonstrated that backgrounds are manageable and that the apparatus worked works as designed. Following the run and the submission of a new proposal, DOE approved and funded the Heavy Photon Search Experiment. The full experiment, using the same technologies as the test run, has now been installed and JLAB has scheduled running time in 2015. The detector is now installed and running at JLabcommissioned at JLAB, and took its first data during the Spring of 2015. More running is scheduled for 2016 and beyond.

HPS offers many opportunities for rotation students. Simulation studies are needed, tracking pattern recognition and vertexing code is being improved, the data acquisition system for the experiment is being refined and upgraded, a new silicon tracker/vertexer is being designed and built, detector monitoring software is being coded, and the physics analysis is being developed. This experiment is very small We are just analyzing our first data, so calibrations, alignment, and improvements to tracking algorithms are needed and physics analyses need to be developed. We will be running the experiment in 2016 and beyond, so HPS data acquisition and operations need to be mastered. In addition, we have begun considering upgrades to the experiment and new experiments aimed at finding hidden sector particles. HPS is a very small experiment 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. Rotation Projects are available for the 20152016-2016 2017 academic year, outlined below. 

Our SLAC group is also involved in the APEX experiment at JLAB, which has already completed a test run in 2010 and published results of its initial search, excluding a new region of heavy photon parameter space. The experiment makes use of two existing spectrometers in Jlab's experimental Hall A. The experiment hopes to take more data during the 2015-2016 JLab cycle and we hope to contribute. John Jaros.

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