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This effects also deteriorates the transverse shape of the energy deposited in teh the calorimeter. The distribution of CalTransRms for events with 1 track and 2 tracks are shown in figures MuonPisaCalTransRms.gif, MuonPisaCalTransRms.ps and MuonPisaCalTransRms.root (gif, ps and root files). Note that the Transverse RMS is substantially smaller than the width of a CsI crystal (26.7mm), as expected.about 3 "crystal widths"; which is definitely not what we should have.
In the case of electron events, there is not a single particle crossing the calorimeter but a bunch (shower) of them distributed over a given region (at least two crystals wide) in the calorimeter. Therefore the impact of this effect on the reconstruction of CalZDir will would be somewhat lower. Yet it will probably be one of the reasons for the broad distributions of CalZDir found for run 700000811 that were shown by Philippe in the past VRVS beam test meeting (2006/08/01).
Additional muon runs
From the list of muon runs in the Beam test data base, only 2 runs are shown as Vertical Muon Runs. I took run number 700000322, which has 10^5 events (5962 seconds of data, taken on 2006/07/15). Before inspecting the data with FRED i applied the same selection criteria used above (vertical events within 5 deg which deposit some energy in teh cal) and ONLY 2 events survived. Later on i noticed that indeed, most events are empty (CalEnergyRaw < 10 MeV). Does anybody know why ?
Anyway, the FRED display for the two events which survived can be found at Evt0 and Evt1. Note that the behaviour is similar to the one described above.
Electrons events @ 5 GeV
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from test beam
Data run used: 700000811
The events discussed below (both distributions and FRED images) were selected with the following criteria:
TCut cut = "TMath::Abs((acos(Tkr1ZDir)*(180./3.14159))-180.) < 5 && CalEnergyRaw>10";
Philippe also shown very broad distributions of CalTransRms in past VRVS beam test meeting (2006/08/01). Yet the origin of this broad distributions seems NOT to be related to the effect which is described above. I do NOT see this effect in the events from run 700000811. Details of this analysis can be found inQuickLookToEventsFromRun700000811.
David please include run numbers
ONGOING ... I 'll do it tomorrow...