current simulation is inadequate and needs work; discrepancies in CTBCORE probably associated to this (extend of excess unclear but probably large), historical issue with CalTransRms from BT data associated to that
simulation requires implementation of this effect; discussion about implementation, i) adding finer McIntegratingHits closer to xtal edge ii) holding info from every single particle simulated in the shower (computationally unacceptable?) iii) implement average behaviour from data asimmetry (NB each xtal has a specific asimmetry curve that requires calibration)
Path forward: modify McIntegratingHit to include effect of direct light and Brewster angle effect at Xtal ends. Modify Xtal response to incorporate new information available from McIntegratingHit. Observe effects using modified CalValsTool that includes Xtal end-to-end light asymetries. Presently being implemented by Tracy.
handling longitudinal position in data
Bill proposes resolving ambiguity by looking at adjacent layers up/below
Philippe says this can be done when reconstructing shower profiles
Luca B propose empirical method to re-align xtals too far away from shower main axis for EM showers - what happens with MIPs?
Energy scale and BT analysis
historical discrepancy from BT: implications for the LAT not unanimously accepted, existing reservations on different calibrations and environments between data and MC
Grove prefers measurement from CRE cutoff wrt BT as it comes from the LAT and is not affected by rate/T effects
agreement to use BT data to study edge effects with EM showers
Regarding the questions on Tue regarding getting CAL info about ghosts, see my comments on the previous day. But note also that we do have an on-orbit dataset we could explore to confirm that we believe that the range selection works properly. We should look at CNO trigger readouts to verify that first range is truly best range. That's the only sample of 4-range data we have with large pulse heights opening the trigger window. Note that we do get a large range of pulse heights from CNO and heavier as they fragment, so we should be able to explore the LEX1 to LEX8 transition and the LEX8 to HEX1 transition.
Regarding the light collection and modeling xtal response:
Path forward: modify McIntegratingHit to include effect of direct light and Brewster angle effect at Xtal ends. Modify Xtal response to incorporate new information available from McIntegratingHit. Observe effects using modified CalValsTool that includes Xtal end-to-end light asymetries. Presently being implemented by Tracy.
I agree that there is direct light. But I'd be wary of thinking too hard about Brewster angle effects and internal reflection. I hope this sentence doesn't imply that someone is proposing some detailed optical modeling of the xtals. We played with optical models in, oh, 1996-1998 off and on. Saclay came in with an expert in optical modeling in 1998-1999 and created an optical model of xtals that gave entirely incorrect taper curves. I concluded long ago that the xtal surfaces and propagation of optical photons are just too hard to model. The surfaces are not optically smooth anywhere, despite the "polishing" that's done over the entire length of two of the four long surfaces, and the roughening that's applied to each xtal individually by human hand to the other two surfaces extends over a different length of every single xtal. Every single xtal is different.
Sure it's possible to understand the principles of where direct illumination is important.
2 Comments
J. Eric Grove
Regarding the questions on Tue regarding getting CAL info about ghosts, see my comments on the previous day. But note also that we do have an on-orbit dataset we could explore to confirm that we believe that the range selection works properly. We should look at CNO trigger readouts to verify that first range is truly best range. That's the only sample of 4-range data we have with large pulse heights opening the trigger window. Note that we do get a large range of pulse heights from CNO and heavier as they fragment, so we should be able to explore the LEX1 to LEX8 transition and the LEX8 to HEX1 transition.
J. Eric Grove
Regarding the light collection and modeling xtal response:
I agree that there is direct light. But I'd be wary of thinking too hard about Brewster angle effects and internal reflection. I hope this sentence doesn't imply that someone is proposing some detailed optical modeling of the xtals. We played with optical models in, oh, 1996-1998 off and on. Saclay came in with an expert in optical modeling in 1998-1999 and created an optical model of xtals that gave entirely incorrect taper curves. I concluded long ago that the xtal surfaces and propagation of optical photons are just too hard to model. The surfaces are not optically smooth anywhere, despite the "polishing" that's done over the entire length of two of the four long surfaces, and the roughening that's applied to each xtal individually by human hand to the other two surfaces extends over a different length of every single xtal. Every single xtal is different.
Sure it's possible to understand the principles of where direct illumination is important.