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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 {html}e<sup>+</sup>e<sup>&ndash;</sup>{html}. It would be produced by electron bremstrahlung on a heavy target, and be identified as a narrow {html}e<sup>+</sup>e<sup>&ndash;</sup>{html} 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 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 {html}e<sup>+</sup>e<sup>&ndash;</sup>{html} pairs and a PbWO{~}4~ crystal calorimeter to deal with the extremely high trigger rates expected. The run suiccessfullysuccessfully demonstrated the technical feasibility of the experiment, so the JLAB program committee rewarded hasus approvedwith a 6 week data taking run at the end of 2014. An extended run in 2015 is possiblelikely as well. Both these runs will use a new apparatus, just now in the design phase, but based on the technologies and techniques we demonstrated in the Test Run. 

HPS offers many opportunities for rotation students. Experimental design and simulation studies willare continueneeded, tracking pattern recognition and vertexing code is being refinedimproved, the data acquisition system for the experiment is being refined and upgraded, a new silicon tracker/vertexer willmust be designed and 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 previousof the previous HPS rotation projects are listed below. New projects will be added.

Our SLAC group is also involved in the APEX experiment, which has already completed a test run lastin Summer2010 and presentedpublished 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 2013-2014 JLab cycle. SLACand had responsibility for constructing the target for the experiment, taking shifts, and helping to develop the data analysis. We will continue collaborating on APEXwe hope to contribute. [John Jaros|mailto:john@slac.stanford.edu].

h2. Fall/Winter 2011 Projects

|| *Project Title* || *Contact Person* || Student ||
| [Silicon Tracker Module and DAQ Development|Project Description - Silicon Tracker Module and DAQ Development] | [Tim Nelson|mailto:tkelson@slac.stanford.edu] |
| [HPS Trigger Simulation |hpsg:HPS trigger simulation] | [Takashi Maruyama|mailto:tvm@slac.stanford.edu] | |
| [Simulating HPS performance in a photon beam |hpsg:Simulating HPS performance in a photon beam] | [Takashi Maruyama|mailto:tvm@slac.stanford.edu] | |
| [hpsg:Magnetic Field Map for Track Reconstruction] | [Matt Graham|mailto:mgraham@slac.stanford.edu] | |
| [hpsg:Tracker Alignment Procedures] | [Matt Graham|mailto:mgraham@slac.stanford.edu] | |
| [hpsg:Optimizing HPS Design] | [Matt Graham|mailto:mgraham@slac.stanford.edu] | |


h2. Spring/Summer 2012 Projects

|| *Project Title* || *Contact Person* || Student ||
| Test Run Occupancy Studies | [Tim Nelson|mailto:tknelson@slac.stanford.edu] | |
| Determine Test Run Tracker Alignment | [Matt Graham|mailto:mgraham@slac.stanford.edu] | |
| Test Run Trigger Studies | [Takashi Maruyama|mailto:tvm@slac.stanford.edu] |