Session EJ: Hadronic Structure Measurements and Instrumentation II

Deconvolution of the measured asymmetry at the MOLLER Experiment

The MOLLER experiment is aiming to measure the parity-violating asymmetry A_PV in the scattering of longitudinally polarized electrons off unpolarized electrons with an uncertainty of 0.8 ppb. This measurement can be used to directly determine the weak mixing angle at low Q² with the best precision that matches Z-pole measurements. Such a determination requires very high statistics, meaning a high detector segmentation and integration running mode. The detector segmentation will help to disentangle the Moller asymmetry from different background processes. This talk will focus on the deconvolution of the asymmetry of the Møller scattered electrons from the background processes.   

Design and Prototyping of Gas Electron Multiplier Chambers for the upcoming MOLLER experiment at Jefferson Lab

MOLLER experiment at JLab is set to measure the parity violating asymmetry in the scattering of longitudinally polarized electrons off unpolarized electrons. This measurement will significantly expand the sensitivity reach to discover new physics beyond the standard model both at lower energy scales(~100 MeV) and at high energy(multi-TeV). In this experiment Gas Electron Multiplier(GEM) detectors, arranged in a circular pattern around the beam pipe, will be used to track individual particles during calibration runs. A GEM chamber consists of 3 GEM foils glued on fiberglass frames and a 2D readout board and has a continuous inside gas flow during operation. The frames have to maintain the stability of the chamber and also the uniform distances between layers. In order to maximize electron detection area, the chamber is designed with a unique trapezoidal shape and a thin curvy edge at the beam pipe side. A complete set of stress-strain analysis and Gas flow simulations were done to ensure that this chamber design performs well under above requirements. A MOLLER GEM chamber prototype is under construction; preliminary test results will be presented.   

Energy Calibration of Scintillation Detectors for MUSE

The MUon Scattering Experiment (MUSE) at the Paul Scherrer Institute will measure the muon-proton and electron-proton elastic cross sections in the same experiment. Multiple timing detectors are used in this experiment. This presentation will discuss methods to determine the energy calibration, using Tl-208, Na-22, and Y-88 sources, signal attenuation, and hit-position reconstructions of various timing detectors, as well as their function in the experiment as a whole.   

Tracking detector for the precision measurements of rare pion decays with PIONEER experiment

A state of the art next-generation rare pion decay experiment, PIONEER, has recently been approved at the Paul Scherrer Institute (PSI,CHRISP). The main motivation of the PIONEER experiment is to improve the test of the Standard Model (SM) hypothesis of lepton flavor universality. It will probe non-SM explanations of possible anomalies through sensitivity to quantum effects of new particles at very high mass scales. Further, the experiment will enable determination of the the CKM matrix element Vud with improved sensitivity. The main observables for PIONEER are the branching ratio for pion decays to positrons relative to muons and the rare process π+ → π0 e+ ν(γ) aiming for an order of magnitude improvement in precision in each case. Pioneer will also search for sterile neutrinos and other exotic processes. The PIONEER experiment design contains an active target (ATAR) based on low-gain avalanche detectors (LGADs), where an intense pion beam is brought to rest and a 3π sr, 25 radiation length (X0) liquid Xe electromagnetic calorimeter. This presentation will introduce a new cylindrical tracker design and discuss the simulation studies in the PIONEER environment. It will surround the ATAR, to link the locations of pions stopping in the target to showers in the calorimeter. The compact tracker design proposal is based on μRWELL micro patter gaseous detector (MPGD) to provide high spatial and timing resolutions with very low radiation length and is suitable for high rate pion beams.   

Scattered beam monitors and scanner detectors for the MOLLER experiment

The MOLLER experiment aims to carry out a precise measurement of the parity-violating asymmetry from electron-electron scattering in Hall A at Jefferson Lab. The measured asymmetry results in an ultra-precise determination of the weak mixing angle. Such a precise measurement demands rigorous control over systematic uncertainties and potential background corrections. For this, the experiment will use several auxiliary detector subsystems. Some of these detector subsystems are important to cross-check the helicity-correlated beam correction procedures and some others are used to monitor the possible drifts in the scattered beam profile. In this talk, I will give an overview of the scattered beam monitors and the scanner detectors for the MOLLER experiment.   

Radiation measurements at the site boundary for the MOLLER Experiment Vassu Doomra (for the MOLLER Collaboration)

For the safety of the personnel working at Jefferson Lab, it’s important to ensure that the shielding around the experiment is reducing the radiation levels to an acceptable limit set by the DOE/JLab (100/10 mrem/year). Absorbed Dose is a crucial parameter in quantifying these radiation levels. However, for discussing biological effects, the nonspecificity of the absorbed dose proves to be inconvenient. Studies have shown that the biological damage caused by irradiation is a strong function of the specific radiation type. To account for this effect, the absorbed dose is multiplied by a quality factor measuring the relative biological effectiveness (specific for each radiation type) and that gives the equivalent dose (measured in rem).

 The monitors measuring the equivalent dose at Jefferson Lab are located at the periphery of the lab ( 200 m away from the center of Hall A) and hence the name boundary dose monitors. Full GEANT4 simulations have been performed to determine the origin of particles (from within the experimental hall) contributing the most towards boundary dose. The results of these simulations suggest that neutrons are the largest contributors to the boundary dose. And that these neutrons are mainly originating from the target and the upstream region.   

The Tracking System and Kinematics Measurement for the MOLLER Experiment

MOLLER (Measurement Of a Lepton-Lepton Electroweak Reaction) is a parity-violating experiment set to start running in Jefferson Laboratory's experimental Hall A in 2025. The parity-violating asymmetry of M\o ller scattered electrons, A_PV, will be measured and used to probe the weak charge of the electron, Q_W^e, to never before seen levels of precision. At tree level, the overall factor that correlates Q_W^e to A_PV is called the kinematic factor, Α, and is dependent on the incoming beam energy and center of mass scattering angle of the electron. A vital component of MOLLER will be its tracking system which will be used for kinematics measurements and will allow us to determine the kinematic factor.

Calibration of our tracking system and verification of our kinematics must be completed in order to calculate Q_W^e​​​​​​​ to the desired level of precision. The ongoing effort to prepare for this involves using Monte Carlo based Geant-4 simulations to optimize the design of our tracking system. This talk will overview the tracking system and the plan for our kinematics measurement.   

Optical Simulation Studies of Particle Detector Design For Efficient Functioning

We have investigated and compared the effectiveness of two different particle detectors based on the light guide material and geometrical design to be utilized in MOLLER experiment at Jefferson Lab. This is done with a view of marking out the most efficient structure that can deliver optimum number of photoelectrons from the scattered electrons passing through the detector. Simulations are carried out with the plastic scintillator coupled to the photomultiplier tube (PMT) separately via polymethyl metacrylate (PMMA) based flat trapezoidal and optical fiber light guides. In the design of the former, PMT is mounted on the light-guide firmly attached to the polyvinyl-toluene based scintillator. For optical fiber coupled scintillator type, two strands of wavelength shifting fibers, terminated by pmt at both of their ends and with separation distance of 100mm between them, were thrusted into the grooves created across the back of the optical scintillator. From the preliminary results obtained, measurements conducted with plastic scintillator coupled through optical fiber to the PMT suggested the betterment of this technique in terms of photoelectron yield than measurement carried out when connected to PMT via flat trapezoidal light guide.   

The Spectator Reaction Plane Detector for CMS

The Spectator Reaction Plane Detectors (SRPDs) are the latest addition to the CMS Zero Degree Calorimeters (ZDCs), designed to produce a reaction plane by mapping spectator neutrons produced in heavy ion collisions at the CERN LHC. There are two ZDCs each positioned 140-m from the interaction point in the positive and negative z-direction. Each ZDC contains an electromagnetic (EM) section and a hadronic (HAD) section with the SRPDs placed between these elements. Both SRPDs are utilized for reaction plane reconstruction, making it important to inter-calibrate the electronic gains of the corresponding quartz blocks. Correlating the output of the SRPD with the 5 sections of the EM in the x-direction gives a combined x-position resolution of ~ 2 mm. It has been recognized that blocks located around the beam position sustained significant radiation damage during the 2018 PbPb run, requiring calibration factors to account for diminished light transmission to the PMTs. This radiation effect is being studied using an electron linac at the University of Maryland (UMD).