Session B18: Undergrad Research I

Holographic Reconstruction of Electron Momenta for the Detection of Muon-to-Electron Conversion via Synchrotron Radiation Emission

The detection of charged lepton flavor violating (CLFV) processes would be a major development, signifying new physics beyond the Standard Model. Muon transitions have established stringent constraints on CLFV processes, and the upcoming generation of experiments will improve current limits by four orders of magnitude [1,2]. Mu2e will measure momentum-dependent electron trajectories using an array of straw tubes, and COMET will use a cylindrical drift chamber, but the momentum resolutions of these technologies are limited by multiple scattering in the detector material. We explore the feasibility of using the emitted synchrotron radiation of the conversion electrons in a magnetic field for momentum reconstruction. Depending on the magnetic field, some of the synchrotron radiation from a 105 MeV electron will lie in the visible band, so a detector composed of a hollow cylinder of pixelated photodetector panels arranged around the electron production point would leave electron paths unobstructed. In this talk, I will present the likelihood-based reconstruction techniques used to extract electron parameters from a sparse track of photon hits. Also, the dependence of physics-sensitive momentum resolutions on the detector parameters will be discussed.

References

[1] Bernstein, R. H. (2019). The Mu2e experiment. Frontiers in Physics, 7(JAN), 421268.

[2] Lee, M. J. (2018). COMET muon conversion experiment in J-PARC. Frontiers in Physics, 6(NOV), 415345.   

Simulation of Synchrotron Radiation Emission for Holographic Reconstruction of Electron Momenta from Muon-to-Electron Conversion

Detecting charged lepton flavor violation (CLFV) would demonstrate physics beyond the Standard Model. The rate of muon transitions (μ → e) is an important bound on CLFV processes. Upcoming experiments such as Mu2e and COMET aim to tightly constrain its branching ratio. These constraints require precise momentum reconstructions for conversion electrons near 105 MeV. Mu2e uses many straw tubes[1] and COMET uses a cylindrical drift chamber[2]. Yet, both tracking techniques are limited by multiple scattering in their detector materials. We hope to avoid this problem, instead using emitted photons from synchrotron radiation for reconstruction. After emission due to synchrotron radiation, these photons are projected onto the detector, forming a 2D track, from which we need to reconstruct the particle momentum. Pixelated photodetectors such as LAPPDs[3] promise excellent time and position resolution and when arranged on the outside of the detector solenoid and do not interrupt the electron path. In this talk, I focus on the simulations used to demonstrate the feasibility of the project. The number, location, and energy of these photons are all important considerations for detector evaluation and must be simulated for varying detector setups.   

Feasibility Study of a Slow Moving Track Search at a 10 TeV Muon Collider

A future 10 TeV muon collider presents fantastic opportunities to search for new fundamental particles. This study focuses on the direct detection of charged long-lived particles (LLPs) via a time of flight measurement in the inner tracker, by identifying tracks that are more slowly moving than those of Standard Model particles. However, beam-induced background (BIB) from muon decays presents a challenge for accurately reconstructing tracks and serves as a potential source of out-of-time background. Presented here is a study of long-lived staus. Analysis of stau lifetime and mass gives insight into which constraints may be imposed to reject BIB while maintaining high efficiency for LLPs, and how to distinguish LLPs from Standard Model particles.   

Feasibility Study of a Displaced Track Search at a 10 TeV Muon Collider

A future 10 TeV muon collider offers enormous potential to search for new fundamental particles. This study focuses on direct detection of charged long-lived particles (LLPs) via displaced tracks in the inner tracker. However, beam-induced-background (BIB) from muon decays makes accurately reconstructing tracks challenging and can lead to background displaced tracks. We show here a study of long-lived staus by studying the stau lifetime, mass, and other kinematic properties. This work gives insight into a potential analysis strategy to reject BIB and SM background while maintaining high efficiency for LLPs.   

Exploring the performance of GPU-based optical photon simulations in Geant4

For future high energy physics (HEP) detectors, dual readout calorimeters (DRC) provide optimal energy resolution by allowing independent measurements of energy deposited via electromagnetic and hadronic interactions. Precise simulations of optical photons from scintillation and Cherenkov processes are essential for the design and calibration of DRCs. Because the number of optical photons generated in DRC simulations is immense and their simulation is impractical on single-threaded CPUs, HEP detector simulations have historically relied on parameterized rather than real-time simulations of optical photons. However, recent advances in Graphical Processing Units (GPUs) and CPU multithreading allow efficient simulation of optical photons in real-time, thus significantly improving the accuracy of DRC simulations. In this project, we explore the performance of the HEP-standard Geant4 simulation software using multithreading and GPUs. The GPU-based simulation relies on the CaTS (Calorimetry and Tracker Simulation) framework, which uses Opticks to translate Geant4 physics to NVIDIA® Optix to run on the GPU and the Geant4 geometry into ray-tracing optimized geometry for GPUs. We observe a speedup of upwards to one hundred times in performance in liquid argon TPC experiments.   

The Search for the X17 boson: Analyzing e+e- pair production processes with the prototype AT-TPC using Geant4

In 2016, a group of scientists discovered a possible candidate for a dark fifth-force carrier of the Universe during an experiment in ATOMKI in Debrecen, Hungary. This hypothetical boson would come from an internal pair creation of the decay of 8Be. In particular, scientists had measured the angular correlations of e+e- pairs and observed that at large angles, a neutral particle with a mass of 16.70 0.35(stat) 0.5(syst) MeV/c2 and J = 1+ was created, hence the name, X17.

The prototype Active-Target Time-Projection Chamber (pAT-TPC) was used to conduct an experiment at the tandem facility of Notre Dame to search for the X17 resonance via the 7Li(p,g)8Be reaction. The angular distribution of the produced e+e- pair from the g conversion will be reconstructed to identify the possible existence of this boson. Preliminary analysis of the data indicates a relatively high identification of triple tracks of two electrons and one positron. A realistic Geant4 Monte Carlo simulation was developed to describe the experimental setup, understand the background, and provide information on the efficiency and resolution of the system. In this presentation, I will discuss and present results from this study. This research is part of PING - Physicists Inspiring the Next Generation: Exploring the Nuclear Matter 2023.   

Pair Production and Hadron Photoproduction Backgrounds at the Cool Copper Collider

Electron-positron pair production and hadron photoproduction are the most important beam-induced backgrounds at linear electron-positron colliders. Predicting them accurately governs the design and optimization of detectors at these machines and, ultimately, their physics reach. With the proposal, adoption, and first specification of the C3 collider concept, it is of primary importance to estimate these backgrounds and begin the process of tuning existing linear collider detector designs to exploit the parameters of the machine fully. We will report on the status of estimating both of these backgrounds at C3 using the SiD detector concept, and discuss the effects of the machine parameters on preliminary detector and electronics design.