Calibration of MUSE Scattered Particle ScintillatorsOctober 4, 2019Anne Flannery

This work is supported in parts by NSF PHY-1614773

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A. Flannery - Calibration of MUSE scattered-particle scintillators

Outline

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Introduction to Muse

SPS Detectors Overview

Calibration of SPS

Concluding Statement

A. Flannery - Calibration of MUSE scattered-particle scintillators

What is the radius of the proton?

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Mesick, Katherine. (2015). The MUSE Experiment: Studying the Proton Radius Puzzle with muon-proton Elastic Scattering. 091. DOI: 10.22323/1.226.0091.

Introduction to Muse

A. Flannery - Calibration of MUSE scattered-particle scintillators

MUon Proton Scattering experiment

Muse Setup

• an experiment which attempts to address the proton radius puzzle through muon-proton and electron-proton scattering measurements in the same experiment

Target

STT

SPS Walls

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220 cm

Electron, muon beam

Momentum 115, 160, 210 MeV/c

Introduction to Muse

A. Flannery - Calibration of MUSE scattered-particle scintillators

Path of the scattered particle

The SPS bars are fast timing detectors for the experiment

STT University of Jerusalem

SPS Walls University of South Carolina

Target University of Michigan

Beam

Scattered-Particle Scintillators (SPS)

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SPS Detectors Overview

A. Flannery - Calibration of MUSE scattered-particle scintillators

How does a scintillator work?

• A charged particle passing through the bar deposits a certain amount of energy (minimum 2 MeVg-1cm2), causing photon emission.

• A photodectector receives a signal whose strength is determined by the amount of energy deposited.

• The photodetector sends this signal to a charge to digital converter (QDC).

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SPS Detectors Overview

Scintillator

Photodetector

Photodetector

QDC

Beam

A. Flannery - Calibration of MUSE scattered-particle scintillators

Where does the signal go, and what does it mean?

• A Na-22 source is used instead of the beam in order to calibrate SPS bars.

Na-22 Decay scheme7

Calibration of SPS

Na-22

511 keV 511 keV

1275 keV

A. Flannery - Calibration of MUSE scattered-particle scintillators

Three kinds of light-matter interaction

http://electrons.wikidot.com/pair-production-and-annihilation

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• Photoelectric effect (lowest energy)

• Compton scattering (medium energy)

• Pair-production (highest energy)

We use Compton scattering for the calibration method

discussed here

Calibration of SPS

Unlikely

Unlikely for 1275 KeV, and impossible for 511 KeV

A. Flannery - Calibration of MUSE scattered-particle scintillators

0 100 200Pulse Height (MQDC Channels)

0

500

1000

1500

Cou

nts

run701_BM00uData (z = 20 cm)Simulation (fit stat. 5)c = 17.8 keV/Channel

= 7.2 %α = 4.8 %β

Example Na-22 QDC Distribution

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Calibration of SPS

1062 keV0 keV 511 keV

A. Flannery - Calibration of MUSE scattered-particle scintillators

Na-22 Calibration for the SPS Bars

• A Na-22 source was placed at varying heights along the bar, in 20cm increments. Since the PMTs were on both the top and bottom of the bar, signal strength lowered as Na-22 source became further from either the up or the down PMT.

Closer Na-22 sourceFurther Na-22 Source

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Calibration of SPS

A. Flannery - Calibration of MUSE scattered-particle scintillators

Concluding Statement

• Future calibration methods will include room background source, especially focusing on the Compton edge for Thallium 208, which is ever-present for all bars. The following graph shows a QDC histogram which is already pedestal subtracted.

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Concluding Statement

0 200 400QDC geom. mean (Channel)

0

200

400

600

Cou

nts

mqdc_geom_single_SPSLR00

Th-208 Compton Edge