<div><p>Dear APEX collaboration,</p>
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<p>Please read this email carefully. It is long, but contains several important announcements and requests for help. The full text of this email can also be found at: </p>
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<p><a href="http://ntoro.stanford.edu/APEX/wiki/index.php/APEX_update_November_2011">http://ntoro.stanford.edu/APEX/wiki/index.php/APEX_update_November_2011</a></p>
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<p>We have successfully completed the first stage of the APEX experiment: a successful test run leading to the approval of the full experiment and the acceptance of the PRL on the test run science results. We are now preparing for the full experiment. </p>
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<p>While APEX has not yet been scheduled, we would like to be ready to run anytime and as soon JLab's schedule allows. However, there are a few things to do before we can run, and we want to take care of these over the next 2--3 months. Below, we detail the near-term plans and several hardware and software projects for which we would greatly welcome help. These contributions will be very important to the smooth running of the experiment. We especially encourage contributions from collaborators who anticipate having little or no availability for shifts, as significant help with these projects will count toward authorship on APEX papers. Please read these and let us know where you can help out. </p>
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<p><b>1. Rights and Responsibilities of APEX Collaboration Members</b></p>
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<p>We will define more clearly the rights and responsibilities as an APEX collaboration member, and what is required to be on future APEX publications. There will be around 600 shifts to fill, and we will likely ask that anybody who wants to be on a future APEX publication will need to complete at least 10. However, significant contribution to the preparation of the experiment (see below) will decrease or remove the required number of shifts. </p>
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<p><b>2. Where we need your help</b></p>
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<p>The level of expertise needed for the projects below vary, but most are appropriate for a post-doc, or for students with active leadership from a senior scientist. Please contact any of the spokespeople if you would like to lead or join any of these efforts. We anticipate that most will require roughly one month worth of work. </p>
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<p>I) Target Lifter Mechanism: test Waterfall Lifter, investigate options from other halls, and target GUI</p>
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<p>II) VDC analysis/reconstruction</p>
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<p>The APEX run will produce electron singles rates of about 5 MHz. At these singles rates, the existing reconstruction software has an efficiency of 50-60%; we are seeking expertise in modifying the VDC analysis algorithms to optimize the efficiency of this reconstruction. Data is available to test the analysis code. </p>
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<p>III) Online software and GUI</p>
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<p>A standard Online GUI is needed to test performance during the test-run (previous Hall A GUIs can be used as a starting point). </p>
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<p>IV) Optics calibration</p>
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<p>APEX optics calibration will be done using both the sieve-slit method and new scintillating fiber detectors (SciFi, see also below) upstream of the HRS's. We are seeking experts to coordinate with the target group on the design of the Optics Target, helping to devise an optics run-plan, and updating baseline optics calibration software (needed to ensure data quality in optics calibration runs) to use the SciFi detector signals. </p>
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<p>V) Beamline and target alignment </p>
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<p>The target alignment and calibration of the GUI needs to be formulated. Beam line commissioning procedures on the level of MCC requirements need to be formulated, written, and approved.</p>
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<p>VI) Detector electronics</p>
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<p>We are looking for a point-person with Hall A experience to take charge of preparing and testing electronics for the HRSs, including HV units and spare DAQ modules as 1877S TDCs. Buffered readout DAQ configuration needs to be organized and tested. Once the schedule is known, we plan to start installation of the S0 counters and VDC electronics, which will require an additional 5--6 man-weeks.</p>
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<p>VII) Target </p>
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<p>The SLAC target was designed exclusively for the test-run configuration of a 2 GeV beam. We need to finalize the full target, for three different beam configurations, and consider alternate designs for the optics target in light of high rates in SciFi detectors.</p>
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<p>VIII) Trigger Development</p>
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<p>The production trigger scheme will be as for the APEX test run, but detailed schematics for the trigger system will need to be revised. </p>
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<p><b>3. Radiation safety review</b></p>
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<p>The PAC has asked for a review of the neutron radiation damage on the electronics that might be incurred from running APEX. We are working with RadCon and JLab management to complete this review by December 15, 2011. </p>
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<p><b>4. Possible Theses for graduate students</b></p>
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<p>The full APEX run consists of four different beam energies and settings. Using this data, we imagine that between 2--4 theses could be written on the main APEX science result (an A' search) -- the final publication would of course be on the whole data set from all four settings. A high statistics QED trident sample could also allow for other theses to, for example, investigate higher order QED effects. Other suggestions for theses topics are welcome. If you have interested graduate students, especially with some proficiency in GEANT or ROOT, please let us know. </p>
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<p><b>5. Talks at Conferences or Seminars </b></p>
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<p>If you want to give a talk on APEX results at a conference or seminar, please let us know. Preference will be given to collaborators that have made major contributions. We will define more clearly your rights and responsibilities for giving presentations. </p>
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<p>We hope that you will be able to help us on some of the above items. Please let us know if you have any questions, comments, or suggestions. </p>
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<p>Kind regards,</p>
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<p>Rouven Essig, Philip Schuster, Natalia Toro, Bogdan Wojtsekhowski</p>
<p>(APEX spokespeople)</p>
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