# SPE Mean Charge Analysis

## Background Information

• Found another paper that gives further detail; some equations on this page are quoted from here (specifically pages 2-5): https://arxiv.org/pdf/1602.03150v1.pdf

• Total integrated charge spectrum is defined by convolution of two components: the pedestal i.e. background and signal :

• The mean charge for the SPE contribution can be found using the following equation:

• According to the link above, making the assumption that the number of photoelectrons follows a Poissonian distribution, , where,:

where is the estimate for the number of 0PE triggers and is the total number of sample triggers.

• NOTE: this analysis only works for low occupancy data

## SPE Mean Charge Calculation

• Run 12617 (RT124; Detector AARFs, 1 waveform, FWF, RAW 10% occupancy) - specifically focusing on subrun 0, PMTID 0. The spectra are found using SPESpectrumProc.cc

• To calculate , found the numerical mean of the entire spectrum
• To calculate , rerun processor with time window shifted to get histogram of just pedestal - find numerical mean of this histogram
• To calculate :
• Normalised the charge spectrum histogram such that the integral = 1. Hence N = 1, and thus and
• Took integral of part of histogram below and including Q = 2pC (which is assumed to only include 0PE triggers), to obtain
• Repeated this process for other PMTs in this subrun:

## Statistical uncertainty on SPE Mean Charge

• Statistical uncertainty on will be found by comparing the SPE mean charge from data with MC to see how much the value changes
• Plan: make a 'hybrid' charge spectra distribution, with real data noise/pedestal with MC SPE pulses
• Repeat above analysis and recalculate SPE mean charge, see how much they differ to obtain UNCERTAINTY
• Current status: HIT mixing tool in process of being adapted in order to make this hybrid, when it is ready I will have more to update!
-- AshleaKemp - 12 Sep 2016

Topic attachments
I Attachment History Action Size Date Who Comment
png Charge_PMTID_0.png r1 manage 31.5 K 13 Sep 2016 - 01:50 AshleaKemp
png charge_vs_ID.png r1 manage 35.0 K 13 Sep 2016 - 22:30 AshleaKemp

This topic: Public > UserList > AshleaKemp > SPEMeanChargeCalculation
Topic revision: r7 - 09 Nov 2016 - AshleaKemp

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