[Olympus] Summary from OLYMPUS collaboration meeting at Mainz

[Douglas Kenneth Hasell]

Dear Colleagues,

	The OLYMPUS collaboration meeting held at Mainz earlier this week was very successful.  On behalf of the collaboration I would like to thank Frank, Roberto, Jürgen, and Dmitry for organising this meeting, dinner, BBQ, workshop, and generally making it a success.

	The following is intended to be a brief summary of where we stand.  The presentations are of course available on the Wiki.

- Jürgen will give the DPG talk on OLYMPUS on Monday

- Rebecca (radiative corrections) and Roberto (SYMB) will also present at DPG

- We have received a list of question from the PRC which they would like to discuss on Wednesday, April 23 before the next PRC meeting at DESY.  The questions are not difficult and I think we can quickly prepare answers.

- Uwe will give the next PRC talk in the open session.  We should plan on preparing things for Uwe by April 14 and reviewing his talk on April 21.

- The outcome of the discussion on the author list for technical papers will be described in a subsequent E-mail.

- Richard has proposed that we hold the next collaboration meeting in Dublin, Ireland.  The range of possible dates is September 15-25.  I will query the group leaders on this with another E-mail.

- Work on the SYMB is progressing nicely.  Roberto has the DNL, 3 sigma cut, and pedestal correction (small) in hand.  Dmitry is almost ready with digitization.  Charles Epstein, an MIT graduate student, has written a radiative Møller/Bhabha/annihilation generator which we can implement. Colton has done a lot on explaining the various features in the coincidence and master/slave histograms and investigated loose cuts.  This will help in determining the background.

- Brian, Denis, and Yury presented studies with the 12 degree detectors.  The MWPC are working well with just 3 bad wires.  The efficiency of the individual GEM planes are problematic and need detailed simmulation.  The GEM efficiency affects studies requiring 6 planes as opposed to 4 planes.  Comparison with slow control luminosity shows a 20% difference which could be in SC.  Comparison with SYMB is a few percent.  Reconstructed track features are reasonably well reproduced in simulation.  There is an alignment/offset issue in the right sector which could be an error in the survey.

- Uwe and Jan described the beam position monitor measurements, calibration, and analysis.  These appear to be in good shape and should be implemented into the analysis framework in the next few weeks.

- Axel and Rebecca described the MIT radiative generator which is available and basically finalised.

- Gevorg described the status of the cosmic ray generator.  Energy deposited in the ToF bars is well described by a combination of Landau and gaussian distributions.

- Rebecca gave an update on the ToF energy and efficiency studies.  With an improved determination of the attenuation length and energy cuts there are new gains for each PMT.  Digitization includes all attenuation, efficiency, energy smearing, and threshold obtained from data.

- Lauren showed new timing offsets and speed of light results.  The comparison between data and MC mean time is quite good (< 1 ns) but vertical position differs by ~50 mm.

- Jan showed the latest results from the track reconstruction.  Brian's TDC distributions from MagBoltz may be able to reproduce the TDC distributions from data to help in determining the time to distance relationship.  Various improvements to the algorithm.  Will redo tracking and release new data but blinded.

- Doug explained an alternative approach to determining the time to distance algorithm.  This still needs improvement but possibly can be used either directly for track reconstruction or in Jan's EAA or as a method for digitizing the WC in the MC.

- Axel showed the results of his analysis of the tracked data.  His analysis selected groomed tracks and then combined pairs of tracks in opposing sectors to yield ep elastic scattering candidates. Using vertex, coplanarity, lepton and proton angles, and deposited ToF energy he produced yield for electron and positron scattering as a function of Q^2.  There is considerable background that becomes significant at backward angles where the yield is small.

- Finally, Michael gave a short talk on the proton radius puzzle, 2 photon exchange, and MUSE. 

- Wednesday we had the workshop on luminosity issues which I will summarize in another E-mail.

                                                    Cheers,
                                                            Douglas

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