Bulletin of the American Physical Society
2017 Fall Meeting of the APS Division of Nuclear Physics
Volume 62, Number 11
Wednesday–Saturday, October 25–28, 2017; Pittsburgh, Pennsylvania
Session KD: Proton Radius and Short Range Correlations |
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Chair: Michael McCracken, Washington and Jefferson College Room: Salon 4 |
Friday, October 27, 2017 2:00PM - 2:12PM |
KD.00001: Probing Three-Nucleon Short-Range Correlations in High Q2 Electroproduction Reactions Misak Sargsian We study the kinematical and dynamical conditions necessary for probing highly elusive three-nucleon short range correlations (SRCs) in nuclei using high momentum and energy transfer electro-nuclear processes. For inclusive processes kinematic constraints are derived that should be satisfied in order to isolate 3N SRCs. The first analysis of the available data in relation to these constraints is presented which reveals the tantalizing signatures of 3N SRCs. We also study the mechanism of generation of 3N SRCs as a sequence of two short-range NN interactions and based on it estimate the ratio of the inclusive cross sections of 4He and 3He nuclei in the 3N SRC domain. This ratio agrees also with the one obtained from the analysis of the experimental data. For semi-inclusive processes we investigate the effects of proton-neutron SRC dominance on the dynamics of 3N correlations. We demonstrate that experimental study of proton-proton short range correlations in specific kinematic conditions will allow to isolate and probe 3N SRCs. [Preview Abstract] |
Friday, October 27, 2017 2:12PM - 2:24PM |
KD.00002: Extracting The Isospin Dependence of Short Range Correlations Dien Nguyen Short Range Correlations (SRCs) have been recognized as responsible for the high momentum tail of the nucleon momentum distribution.Several experiments at Jefferson Lab have exploited inclusive scattering to study these SRCs. An experiment (E08014) took place in Hall A at Jefferson Lab in Spring 2011 and measured the A(e,e’) cross-section from the Ca isotopes ($^{40}$Ca and $^{48}$Ca). By taking the ratio of the per nucleon cross sections of $^{48}$Ca to $^{40}$Ca in a kinematic region dominated by SRCs we are able to extract their isospin dependence. Data was also collected on $^{3}$He and $^{4}$He at $2 < x<3$ to study 3 nucleon short-range correlations. After a brief discussion of the motivation and of the experimental details, the preliminary results will be presented. [Preview Abstract] |
Friday, October 27, 2017 2:24PM - 2:36PM |
KD.00003: ABSTRACT WITHDRAWN |
Friday, October 27, 2017 2:36PM - 2:48PM |
KD.00004: SeaQuest Studies of the EMC Effect - Present Status Larry Donald Isenhower SeaQuest (E-906) is a fixed target experiment that uses the 120 GeV proton beam from the Main Injector at Fermilab to study the Drell-Yan process from different targets, including liquid hydrogen and deuterium, tungsten, iron, and carbon. The EMC, European Muon Collaboration, effect was the discovery in 1983 of the modification of quark momentum distributions when nucleons are bound into a nucleus compared to when they are independent particles. There have been many studies on this topic since that time and SeaQuest is also making a study of this process via the Drell-Yan production of di-muons. The experiment consists of a two magnet focusing spectrometer with four separate detector sections. SeaQuest will soon have recorded its complete data set, and its analysis is expected to produce an improved measurement of this effect. The most recent results will be presented, along with what conclusions the complete data set should be capable of reaching in verifying if anti-shadowing is not present in the Drell-Yan process as E-772, a previous Fermilab Experiment, found. [Preview Abstract] |
Friday, October 27, 2017 2:48PM - 3:00PM |
KD.00005: Tritium at Jefferson Lab Jason Bane Jefferson Lab's recently upgraded accelerator will provide the perfect opportunity to increase the quality and quantity of the electron scattering world data on tritium. Tritium, the radioactive isotope of hydrogen with a half-life of 12 years, was last used in a large scale electron scattering experiment a few decades ago. This Fall Jefferson Lab will play host to a set of very exciting electron scattering experiments involving tritium. A 25 cm aluminum cell will be filled with 1 kCi of tritium with an internal pressure of approximately 200 psi at 295 kelvin. The tritium target will first see a 10.6 GeV beam to probe the deep inelastic scattering region to study the down to up quark ratio and the EMC effect. Then the beam will be set to 4.3 GeV to investigate SRCs and momentum distributions in the quasi-elastic scattering regime. If time permits, elastic scattering will be used to extract the ratio of the charge radius of tritium and helium3. [Preview Abstract] |
Friday, October 27, 2017 3:00PM - 3:12PM |
KD.00006: The proton radius puzzle Gil Paz In 2010 the proton charge radius was extracted for the first time from muonic hydrogen, a bound state of a muon and a proton. The value obtained was five standard deviations away from the regular hydrogen extraction. Taken at face value, this might be an indication of a new force in nature coupling to muons, but not to electrons. It also forces to reexamine our understanding of the structure of the proton. In this talk I will describe an ongoing theoretical research effort that seeks to address and resolve this "proton radius puzzle". In particular, I will present a reevaluation of the proton structure effects, correcting 40 years of such calculations, and the development of new effective field theoretical tools that would allow to directly connect muonic hydrogen and muon-proton scattering. [Preview Abstract] |
Friday, October 27, 2017 3:12PM - 3:24PM |
KD.00007: Addressing the Proton Radius Puzzle Using QED-NRQED Effective Field Theory Steven Dye The proton radius puzzle, i.e. the large discrepancy in the extraction of the proton charge radius between regular and muonic hydrogen, challenges our understanding of the structure of the proton. It can also be an indication of a new force that couples to muons, but not to electrons. An effective field theory analysis using Non Relativistic Quantum Electrodynamics (NRQED) indicates that the muonic hydrogen result can be interpreted as a large, compared to some model estimates, muon-proton spin-independent contact interaction. The muonic hydrogen result can be tested by a muon-proton scattering experiment, MUSE, that is planned at the Paul Scherrer Institute in Switzerland. The typical momenta of the muons in this experiment are of the order of the muon mass. In this energy regime the muons are relativistic but the protons are still non-relativistic. The interaction between the muons and protons can be described by a hybrid QED-NRQED effective field theory. [Preview Abstract] |
Friday, October 27, 2017 3:24PM - 3:36PM |
KD.00008: Extraction of the Proton Radius from Electron Scattering Data Douglas Higinbotham The proton radius is commonly extracted from elastic electron scattering data from fits that attempt to determine the slope of the cross section via extrapolations to zero momentum transfer. From the collection of published fits, it is clear that it is possible for different radii to be extracted from exactly the same data depending on how exactly the extraction is done. To understand the source of these differences, we review older fitting techniques and apply them to the modern data. This allows us to effectively make use of the idea of training data and then validation data. We also make use of statistical techniques such as cross validation and statistical bootstrapping to try to understand if certain data points in the world data are the source of these seemingly discrepant results. We will also discuss the interplay between bias and variance. [Preview Abstract] |
Friday, October 27, 2017 3:36PM - 3:48PM |
KD.00009: Data Analysis and Preliminary Results of the Proton Charge Radius Experiment (PRad) at JLab Weizhi Xiong, Chao Peng In order to investigate the proton radius puzzle, the PRad experiment (E12-11-106\footnote{Spokespersons: A. Gasparian (contact), H. Gao, M. Khandaker, D. Dutta}) was performed in 2016 in Hall B at Jefferson Lab, with 1.1 and 2.2 GeV unpolarized electron beam on a windowless H$_2$ gas flow target. The experiment aims to extract the electric form factor of the proton in an unprecedented low squared momentum transfer region ($\rm{Q}^2 = 2\times10^{-4} - 0.06~\rm{(GeV/c)}^2$), with a sub-percent precision. The PRad experiment utilizes a non-magnetic calorimetric method with a large acceptance and high resolution calorimeter (HyCal), and two large area, high spatial resolution Gas Electron Multiplier (GEM) detectors. To control the systematic uncertainties, the absolute $e-p$ elastic scattering cross section is normalized to that of the well-known M$\o$ller scattering process, which is measured simultaneously within similar kinematics and experimental acceptances. Both the luminosity and the energy independent part of the detector acceptance and efficiency are canceled out in the ratio. In this talk, we will discuss details of the data analysis and present the preliminary physics results from the 2.2 GeV data. [Preview Abstract] |
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