[Sbs_software] SBS Simulation Meeting Wednesday

Wed Jan 31 08:49:04 EST 2018

Hi everyone,

On second thought, I will postpone my discussion of new g4sbs features until the next meeting, as I won’t have time to attend today’s meeting due to my travel schedule.

Best regards,
Andrew

Sent from my iPhone

> On Jan 30, 2018, at 6:33 PM, Andrew Puckett <puckett at jlab.org> wrote:
> 
> Hi Seamus, 
> I'll give a brief update at the simulation meeting tomorrow on some improvements I've made/am making to the "under-the-hood" machinery of g4sbs: 
> 1) Option to turn on rejection sampling for the built-in event generators, which produces events distributed according to the calculated differential cross section; the code generates a user-specified number of "pre-events" thrown flat in phase space, that aren't tracked through the setup, in order to determine the maximum event weight within the user-defined generation limits. This process is fast, and leads to reasonably good efficiency for the rejection sampling, provided the differential cross section does not vary by too many orders of magnitude within the event generation limits. Then it uses this maximum event weight for a rejection sampling to produce events distributed according to the model cross section. This option is useful in particular for physics analyses where one wishes to avoid the complications of estimating statistical uncertainties for weighted Monte Carlo statistics. This modification is finished, tested, and pushed to the uconn_dev branch of the github repo. 
> 2) Modifying the sensitive detector and hit classes to define a hit time window and energy threshold for "calorimeter" type; i.e.,       showering detectors (or scintillators when we don't want to turn on the optical photon machinery). This modification improves on the existing machinery in that the existing machinery only allows for one "hit" per detector channel per simulated event; i.e., all energy deposition in a given sensitive volume in a given simulated event is summed into a single "hit", regardless of the timing of those energy depositions. The "hit timing" calculated using this machinery would sometimes be distorted by averaging in low-energy secondaries that are significantly delayed relative to the primary particle hits. 
> The new machinery allows more than one hit per sensitive detector channel per simulated event by defining a "hit timing window" analogous to a gate for charge integration in an ADC and/or a sampling window for a Flash ADC type digitization. Starting with the time of the earliest energy deposition in a channel, all energy depositions arriving within a user-configurable timing window of the "hit start time" will be accumulated in the first hit, and any energy depositions occurring later than the hit start time plus the gate width will start a new hit in the same detector channel. For now I do not consider pulse shape/pileup, but I simply assume that the hit timing window will be chosen suitably wide to encompass >~ 99% of the primary signal. Note that the simulation only includes the time dependence of the energy       deposition itself, and does not account for the pulse shaping effects of the PMT multiplication or process and/or amplification/shaping by front-end electrons.  
> This modification gives a more accurate measure of the hit timing and time resolution, and the energy resolution, for simulated hits. I also now allow the user to define an energy threshold for sensitive detector hits on a per-detector basis. Currently, a zero threshold is used, meaning that any non-zero energy deposition in a sensitive volume (that is not an optical photon detector) produces a sensitive detector hit. Allowing the user to define a threshold allows for a more realistic view of detector background rates/occupancies/efficiencies (assuming the threshold is defined in a sensible way) and can in principle reduce the size on disk of simulation output files. But it could also be somewhat redundant with the external digitization libraries and give misleading results if sensible values are not used. 
> I have already finished coding and testing this change for "calorimeter" type detectors that measure energy deposition, but I'm still working on the appropriate machinery for the other detectors, including "GEMs" and "ECALs". I have tried to define sensible default values for each of the detectors in the various experiments, and will add the relevant UI commands for user customization. Time permitting (I have to catch a flight at 1 PM tomorrow), I will show a few slides about my progress on these developments. 
> Best regards,
> 
> Andrew
> 
>> On 1/30/18 9:56 AM, Seamus Riordan wrote:
>> Hi everyone,
>> We will have our next meeting regarding the SBS simulation and DAQ, Wednesday, at 9AM ET.
>> 
>> You can call in at:
>> 
>> +1-888-240-2560
>> (US and Canada) and see international numbers
>> 
>> Access number:  9989030149
>> https://bluejeans.com/9989030149
>> 
>> TED 2561B has been reserved for those attending locally at the lab.
>> 
>> An agenda can be found here:
>> 
>> http://hallaweb.jlab.org/12GeV/SuperBigBite/sbssimwg/20180131/
>> 
>> Please add anything you want to share to this week's page from the CUE
>> 
>> /group/halla/www/hallaweb/html/12GeV/SuperBigBite/sbssimwg
>> 
>> or email me slides or plots that you have to show before the meeting!
>> 
>> Best,
>> Seamus
>> -- 
>> Seamus Riordan                          sriordan at anl.gov
>> Argonne National Laboratory             Office: (630) 252-4101
>> Assistant Physicist                     Fax:    (630) 252-3903
>> 
>> Physics Division Building 203           Room C265
>> Argonne National Laboratory
>> 9700 S. Cass Ave 
>> Argonne, IL  60439
>> 
>> 
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> 
> -- 
> Andrew Puckett
> Assistant Professor, Department of Physics, University of Connecticut
> 2152 Hillside Road, U-3046
> Storrs, CT 06269-3046
> E-mail: puckett at jlab.org, puckett at phys.uconn.edu
> Office phone: 860-486-7137
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