Bulletin of the American Physical Society
2017 Fall Meeting of the APS Prairie Section
Saturday–Sunday, November 11–12, 2017; University of Illinois at Chicago, Chicago, Illinois
Session A1: Session A |
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Chair: Claudio Ugalde, University of Illinois at Chicago Room: UIC Student Center East 302 |
Saturday, November 11, 2017 1:00PM - 1:30PM |
A1.00001: Understanding the Proton’s Spin at STAR Invited Speaker: Adam Gibson A major goal of the proton spin physics program at the Relativistic Heavy Ion Collider (RHIC) is to constrain the gluon polarization distribution $\Delta g (x)$ and thus determine the contribution of gluons to the spin of the proton. Recent global analyses, with major impact from STAR, have demonstrated a positive contribution to the spin of the proton from mid-to-high $x$ gluons (e.g. $x > 0.05$). A variety of measurements at STAR have been recently completed, or are now underway, to better constrain the gluon polarization distribution, particularly at low $x$. Inclusive jet measurements at mid-rapidity (tracking with $|\eta| < 1.3$) remain a core part of the STAR program while measurements with correlated observables like dijets provide more precise information about the initial-state parton kinematics. Moving to forward pseudorapidities (additional calorimetry with $1.09 < \eta < 2.00$ and $2.65 < \eta < 4.0$) with neutral pions allows us to probe lower partonic momenta, as does moving to higher center-of-mass energy. We will present the status of a variety of asymmetry measurements and the results of others using jet, dijet and neutral pion probes with longitudinally polarized $p+p$ datasets at $\sqrt{s} = 200$ GeV (25 pb$^{-1}$) and $\sqrt{s} = 510$ GeV (382 pb$^{-1}$). [Preview Abstract] |
Saturday, November 11, 2017 1:30PM - 1:42PM |
A1.00002: Measurements of J/psi polarization in p+p at $\sqrt{s}$ = 200 GeV by the STAR experiment Siwei Luo Quarkonium production mechanisms in elementary hadron collisions are not yet fully understood. Different models for quarkonium production can describe the measured production cross-section in p+p collisions but have significantly different predictions for polarization. Measurements of J/psi polarization in p+p collisions can distinguish these models and test the fundamental theory on quarkonium production. In this presentation, I will show the measurements of J/psi polarization in p+p collisions at $\sqrt{s}$ = 200 GeV using data taken in 2012 by the STAR experiment. The polarization parameter $\lambda_{\theta}$ in the helicity frame is extracted using 1-dimensional fit in the transverse momentum range of 2-8 GeV/c. Furthermore, I will also discuss the approach to extract the polarization parameters using a 2-dimensional maximum likelihood fit. The new method has the capability to extract the three polarization parameters $\lambda_{\theta}$, $\lambda_{\phi}$ and $\lambda_{\theta\phi}$ simultaneously, which provides a more comprehensive picture for understanding the J/psi polarization. [Preview Abstract] |
Saturday, November 11, 2017 1:42PM - 1:54PM |
A1.00003: Measurements of electron from heavy flavor decays in Au$+$Au collisions at sqrt(s$_{\mathrm{NN}})=$ 200 GeV by the STAR experiment Shenghui Zhang Heavy quarks are predominantly produced at early stages of high-energy heavy-ion collisions due to their large masses. Studies of interactions between heavy quarks and the Quark-Gluon Plasma (QGP) can provide new insights into the properties of the QGP. In particular, the energy loss of charm quarks in the medium is expected to be smaller than that of bottom quarks due to different masses. Since heavy quarks are not directly measurable experimentally, electrons from semi-leptonic decays of heavy flavor hadrons, also known as non-photonic electrons (NPE), can serve as a proxy to the parent partons and provide access to heavy quark energy loss in the medium. In this talk, we will present the latest measurements of the nuclear modification factor (RAA) for NPE production in Au$+$Au collisions at sqrt(s$_{\mathrm{NN}})=$ 200 GeV from the STAR experiment. We will also discuss the first results on separation of contributions from open charm and bottom hadron decays to NPE production via the impact parameter method utilizing the Heavy Flavor Tracker. [Preview Abstract] |
Saturday, November 11, 2017 1:54PM - 2:06PM |
A1.00004: Prospects for Improved Isotopic Reactor Antineutrino Flux Measurement Yonas Gebre, Bryce Littlejohn, Pranava Teja Surukuchi Recent reactor antineutrino experiments have observed a deficit in the antineutrino flux coming from nuclear reactors. Now referred to as the `Reactor Antineutrino Anomaly', this deficit might be caused by a miscalculation of the antineutrino flux from the decay of one or more of the fission isotopes namely $^{\mathrm{235}}$U, $^{\mathrm{238}}$U, $^{\mathrm{239}}$Pu and $^{\mathrm{241}}$Pu in nuclear reactors. This analysis looks at how well we can use current experiments results to determine the antineutrino flux coming from each of the fission isotopes and their contribution to the measured deficit. New short-baseline reactor neutrino efforts can produce unique new flux measurements that can improve constraints on isotopic antineutrino flux contributions beyond those enabled by existing flux measurements conducted over the past three decades. In particular, having the same detector placed at an HEU (Highly Enriched Uranium) and then at an LEU (Low Enriched Uranium) reactor will produce a series of highly-correlated antineutrino flux measurements. This talk will present future achievable constraints on isotopic contributions to the reactor antineutrino flux enabled by the addition of flux measurements at HEU and LEU reactor cores. [Preview Abstract] |
Saturday, November 11, 2017 2:06PM - 2:18PM |
A1.00005: Lorentz-Violating Terms in Gauge Field Theorie Zonghao Li, V. Alan Kostelecky Our best existing description of nature is provided by the Standard Model for particle physics and General Relativity for gravity. The unification of these two theories in a consistent picture of quantum gravity is widely expected to involve modifications that go beyond known physics. One popular modification involves small deviations from Lorentz invariance. In this talk, we present all Lorentz-violating terms that can arise in a gauge field theory coupled to Dirac fermions and briefly outline some experimental implications. [Preview Abstract] |
Saturday, November 11, 2017 2:18PM - 2:30PM |
A1.00006: Lorentz-Violating Particle Motions and Finsler Geometry Benjamin Edwards, V. Alan Kostelecky Deviations from the Lorentz symmetry of relativity arising in unified theories of quantum physics and gravity may lead to observable signals at low energies. The motion of point particles in the presence of Lorentz violation can be derived using lagrangian methods in classical mechanics. It has been conjectured that these particles follow geodesics of Finsler geometry instead of Riemann geometry. This talk summarizes various aspects of the current understanding in this active field. [Preview Abstract] |
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