122827609
The radiance of the gluon spin : constraining the proton spin structure with the direct photon double helicity asymmetry
Although fundamental to the observable universe, the proton is not elementary. Rather the particle is a bound state of three valence quarks and the QCD vacuum that condenses around them, its properties an amalgamation of those underlying degrees of freedom. Naive expectations presume that contributions from the valence quarks dominate these properties, but the deep inelastic scattering (DIS) experiments which first investigated the proton structure in detail revealed the importance of the vacuum. In particular, polarized DIS measurements uncovered a surprisingly inadequate quark polarization, necessitating significant contributions to the proton spin from elsewhere. The total spin of the gluon field confining the quarks is one possibility, but a contribution only weakly constrained by the electromagnetic probes of DIS. An observable far more sensitive to contributions from the gluon field can be found in the collision of two polarized protons. By correlating the incident proton helicities with final-states originating from an initial-state gluon, the double-helicity asymmetry directly probes the underlying gluon polarization and provides much stronger experimental constraints. Asymmetries measured with hadronic final-states have already improved the understanding of the proton spin structure significantly, but with accumulating statistics these measurements will eventually be limited by systematic uncertainties. Although direct photons are rare in the hadronic environment, the simplicity of the resulting asymmetry ultimately promises a more precise probe of the gluon polarization. Located at the Relativistic Heavy Ion Collider (RHIC), the only facility in the world capable of accelerating and colliding polarized proton beams, the Solenoidal Tracker at RHIC (STAR) provides the large acceptance electromagnetic calorimetry and charged particle tracking critical for measuring direct photons and, subsequently, their asymmetry. Utilizing data from the 2009 running period with intricate simulation, state-of-the-art statistical methods have been developed to tease out the rare photon signal from an overwhelming hadronic background to enable the first direct photon measurements at STAR. This thesis details the construction of the unpolarized cross section and an initial double-helicity asymmetry, proving the feasibility of the direct photon program at the experiment. Thesis Supervisor: Robert Redwine Title: Professor of Physics iii
52102076
Toward Characterization Of The Type IIP Supernova Progenitor Population: A Statistical Sample Of Light Curves From Pan-STARRS1
In recent years, wide-field sky surveys providing deep multiband imaging have presented a new path for indirectly characterizing the progenitor populations of core-collapse supernovae (SNe): systematic light-curve studies. We assemble a set of 76 grizy-band Type IIP SN light curves from Pan-STARRS1, obtained over a constant survey program of 4 yr and classified using both spectroscopy and machine-learning-based photometric techniques. We develop and apply a new Bayesian model for the full multiband evolution of each light curve in the sample. We find no evidence of a subpopulation of fast-declining explosions (historically referred to as Type IIL SNe). However, we identify a highly significant relation between the plateau phase decay rate and peak luminosity among our SNe IIP. These results argue in favor of a single parameter, likely determined by initial stellar mass, predominantly controlling the explosions of red supergiants. This relation could also be applied for SN cosmology, offering a standardizable candle good to an intrinsic scatter of 0.2 mag. We compare each light curve to physical models from hydrodynamic simulations to estimate progenitor initial masses and other properties of the Pan-STARRS1 Type IIP SN sample. We show that correction of systematic discrepancies between modeled and observed SN IIP light-curve properties and an expanded grid of progenitor properties are needed to enable robust progenitor inferences from multiband light-curve samples of this kind. This work will serve as a pathfinder for photometric studies of core-collapse SNe to be conducted through future wide-field transient searches.
10534441
New measurements and quantitative analysis of electron backscattering in the energy range of neutron beta-decay
We report on the first detailed measurements of electron backscattering from plastic scintillator targets, extending our previous work on beryllium and silicon targets. The scintillator experiment posed several additional experimental challenges associated with charging of the scintillator target, and those challenges are addressed in detail. In addition, we quantitatively compare the energy and angular distributions of this data, and our previous data, with electron transport simulations based on the GEANT4 and PENELOPE Monte Carlo simulation codes. The PENELOPE simulation is found globally to give a superior description of the data. Such information is crucial for a broad array of weak-interaction physics experiments, where electron backscattering can give rise to the dominant detector-related systematic uncertainty.
55849521
Early Neutrino Data in the NO$\nu$A Near Detector Prototype
NO{nu}A is a long-baseline neutrino experiment using an off-axis neutrino beam produced by the NuMI neutrino beam at Fermilab. The NO{nu}A experiment will study neutrino {nu}{sub {mu}} {yields} {nu}{sub e} oscillations. A short term goal for the NO{nu}A experiment is to develop a good understanding of the response of the detector. These studies are being carried out with the full Near Detector installed on the surface (NDOS) at Fermilab. This detector is currently running and will acquire neutrino data for a year. Using beam muon neutrino data, quasi-elastic charged-current interactions will be studied. Status of the NDOS running and early data will be shown.
199679707
Measurement of muon plus proton final states in $\nu_{\mu}$ Interactions on Hydrocarbon at $ $ = 4.2 GeV