Session G19: Undergrad Research VII

Exploring Sterile Neutrino Decays in the Adolescent Universe

The early universe provides a unique opportunity for researching neutrinos because in these dense and hot places, neutrinos have significant interactions with each other and everything else in the plasma of the early universe. One issue in the current cosmological paradigm is the lithium problem, where there is a discrepancy between predicted versus observed abundances of lithium produced during Big Bang Nucleosynthesis. In this talk, we look beyond the Standard Model to try and address this discrepancy by using the early universe as a laboratory to study the decay of sterile neutrinos into Standard model particles and its effect on cosmological observables. These decays create nonthermal neutrino spectra as opposed to nearly thermal spectra predicted by standard cosmology. These altered spectra affect the production of primordial elements during BBN and the formation of large scale structure.   

Measuring Atmospheric Neutrinos in Olivine

Cosmic rays are constantly hitting the Earth's surface, carrying information about the cosmos itself and the nature of the particle itself. These cosmic rays have been hitting the Earth since its formation, spanning back to the beginnings of the Solar System itself. In order to study the long history of cosmic ray interatctions at earth, we can exploit atmospheric neutrinos that have been bombarding the Earth and its paleodetectors, or minerals deep underground. By analyzing these paleodetectors, rare-event interactions (atmospheric and supernova neutrino, and dark matter induced nuclear recoils) can be isolated and measured over gigayear timescales. Through measuring tracks in different aged minerals, we can see how the flux of cosmic rays varies over large time scales and relate that to possible transient cosmic events. We will present an overview of recent progress in this field.   

Boosting Neutrino Mass Ordering Sensitivity with Inelasticity for Atmospheric Neutrino Oscillation Measurements

Neutrino telescopes cannot distinguish between neutrinos and antineutrinos on an event-by-event basis. Rather, they can do so on a statistical basis, that is, by considering a large dataset of events and exploiting kinematic variables for which different event distributions emerge between neutrinos and antineutrinos. So far, however, analyses in water(ice)-Cherenkov neutrino telescopes aimed at determining neutrino oscillation parameters have not exploited such kinematic variables. This limits the potential of these telescopes to use atmospheric neutrinos for measuring the different oscillation effects between neutrinos and antineutrinos, which would help in improving their sensitivity to parameters such as the neutrino mass ordering, δ_CP, and △m²₃₁. In this talk, I will share preliminary results of research on the effects of including an event’s inelasticity in the IceCube-Upgrade and ORCA detectors. This inclusion is done by considering muon neutrino charged-current interactions and separately reconstructing the track and cascade energies, thereby inferring an event's inelasticity. We find that the combined mass ordering sensitivity of both experiments increased from ~7σ to ~8.4σ, and we can exclude values of  δ_CP with greater than ~2σ significance (up from ~1σ without the inelasticity). Lastly, we find a ~30% improvement in the resolution of △m²₃₁, achieving a precision for its value below the percent level (~0.7%).   

IsoDar Neutrino Target

The IsoDAR experiment will search for neutrino oscillations and other beyond standard model physics using electron antineutrino induced inverse beta decay (IBD) events. IsoDAR will consist of a high power 60 MeV proton cyclotron and lithium/beryllium target combination as an intense source of electron antineu- trinos. To achieve the lithium/beryllium target we need an injector to create this mixture. This talk will present the design of the target and steps towards creating it.   

Reconstruction of Chargino Decays to $\tau H$ with Missing Transverse Momentum

Tau lepton ($\tau$) is usually the least investigated of all lepton flavors, due to its large missing transverse momentum caused by the undetected tau neutrino in the decay of $\tau$, which makes accurate reconstruction of $\tau$ challenging. Since some R-parity violating supersymmetry models hint at a preference for $\tau$ flavor in lepton decays from charginos, it may be helpful to special accommodate this $\tau$ preference. As part of the ATLAS experiment at the CERN Large Hadron Collider, this research investigates the reconstruction of chargino pairs with R-parity violating decays to $\tau \tau H H$ ($H$ refers to Higgs boson) with special consideration of the missing transverse momentum. This research improves the reconstruction of charginos by separating the missing transverse momentum vector into two components and reverse projecting them onto the directions of the visible particles from $\tau$ decays. This improved reconstruction method leads to an improvement of about 15% in pairing accuracy is achieved across chargino masses from 250 GeV to 1500 GeV using truth-level simulations, and the reconstructed chargino mass peaks closer to the expected mass. Using reconstructed simulations, this method shows improvements in pairing efficiency of about 30% on average, also with the shift in the peak. Cuts are also optimized for this reconstruction method.   

Atomic lithium beamline R&D as a pathfinder toward magnetically cooled atomic tritium

Trapping and storage of atomic tritium (T) is a necessary step for advancing the precision of direct searches for neutrino mass to the 40 meV level. However, techniques for cooling large atom fluxes to the mK temperatures required for trapping in a CRES experiment have yet to be demonstrated. In parallel to ongoing work on atomic hydrogen manipulation, the Project8 collaboration is exploring magnetic cooling methodologies using Lithium as a stand-in for tritium. I will discuss recent developments in the lithium cooling apparatus and the the R&D program that will be taking place in the future. Emphasis will be given to the lithium source and the saturated absorption and fluorescence spectroscopy used for temperature measurement and spatial tomography of the lithium beam. The next stages of the R&D will consist of the integration of a Zeeman slower and magnetic evaporative cooling lithium beamline to achieve temperatures at 10 millikelvin.   

Probing the Proton Target Fragmentation with Jefferson Lab CLAS12 Detector

Studies of the properties and the azimuthal distributions of hadrons produced in the Target Fragmentation Region serve as a test of our complete understanding of the different mechanisms in the SIDIS production of hadrons and provide additional information on the QCD dynamics that are not accessible with single hadron production in the Current Fragmentation Region. We present studies of beam SSA for semi-inclusive protons (ep → e′p'+X), produced in the TFR, that can be related to higher twist Fracture Functions. Such measurements were performed with the CLAS12 detector in Hall B at Jefferson lab using a longitudinally polarized 10.6~GeV electron beam on an unpolarized hydrogen target. Preliminary results of this study captured the transition between the TFR and CFR regions showing a clear sign change of the SSA for protons produced in the backward region in CM, dominated by TFR protons providing a criteria for experimental separation of CFR and TFR regions. These findings are opening a new avenue for studies of nucleon structure.