Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session B12: Hadron Tomography |
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Sponsoring Units: DNP GHP Chair: Ian Cloet, Argonne National Lab Room: Roosevelt 4 |
Saturday, January 28, 2017 10:45AM - 10:57AM |
B12.00001: Nucleon Parton Structure from Continuum QCD Kyle Bednar, Ian Cloet, Peter Tandy The parton structure of the nucleon is investigated using QCD's Dyson-Schwinger equations (DSEs). This formalism builds in numerous essential features of QCD, for example, the dressing of parton propagators and dynamical formation of non-pointlike di-quark correlations. All needed elements of the approach, including the nucleon wave function solution from a Poincar\'e covariant Faddeev equation, are encoded in spectral-type representations in the Nakanishi style. This facilitates calculations and the necessary connections between Euclidean and Minkowski metrics. As a first step results for the nucleon quark distribution functions will be presented. The extension to the transverse momentum-dependent parton distributions (TMDs) also be discussed. [Preview Abstract] |
Saturday, January 28, 2017 10:57AM - 11:09AM |
B12.00002: A Euclidean bridge to the relativistic constituent quark model Timothy Hobbs, Mary Alberg, Gerald Miller We explore the potential of a {\it Euclidean constituent quark model} (ECQM) to bridge the lingering gap between Euclidean and Minkowski field theories in studies of nucleon structure. Specifically, we develop our ECQM using a simplified quark-scalar diquark picture of the nucleon as a first calculation. Our treatment in Euclidean space necessitates a hyperspherical formalism involving polynomial expansions of diquark propagators in order to marry our ECQM with results from Bethe-Salpeter Equation (BSE) analyses. From this framework, we define and compute a new quantity --- a {\it Euclidean density function} (EDF) --- an object that characterizes the nucleon's various charge distributions as functions of the quark's Euclidean momentum. Applying this technology and incorporating information from BSE analyses, we find the quenched dressing effect on the proton's axial-singlet charge to be small in magnitude and consistent with zero, while use of recent determinations of unquenched BSEs results in a large suppression. The substantial effect we obtain for the impact on the axial-singlet charge of the unquenched dressed vertex compared to the quenched demands further investigation. [Preview Abstract] |
Saturday, January 28, 2017 11:09AM - 11:21AM |
B12.00003: Studies of the energy-momentum tensor in extreme-instability systems Filip Bergabo, Michael Cantara, Manuel Mai, Peter Schweitzer The $D$-term is, like mass and spin, a fundamental property related to the energy-momentum tensor. Yet it is not known experimentally for any particle. In all theoretical studies so far the $D$-terms of various particles were found to be negative. Early works gave rise to the assumption that the negative sign could be related to stability. The emerging question is whether it is possible to find a field-theoretical system with a positive $D$-term. To shed some light on this question we investigate $Q$-clouds, an extreme parametric limit in the $Q$-ball system. $Q$-clouds are classically unstable solutions which delocalize, spread out over all space forming an infinitely dilute gas of free quanta, and are even energetically unstable against tunneling to plane waves. These extremely unstable field configurations provide an ideal candidate system for our purposes. By studying the energy-momentum tensor we show that at any stage of the $Q$-cloud limit one deals with perfectly well-defined and, when viewed in appropriately scaled coordinates, non-dissipating non-topological solitonic solutions. In particular, we show that $Q$-cloud solutions have negative $D$-terms, indicating that it is unlikely to realize a positive $D$-term in a consistent physical system. [Preview Abstract] |
Saturday, January 28, 2017 11:21AM - 11:33AM |
B12.00004: Studies of the Strange Sea-Quarks Spin with Kaons. Fatiha Benmokhtar, Andrew Voloshin, Justin Goodwill, Andrew Lendacky It is well known that quarks and gluons give the substructure to the nucleons. and understanding of the spin structure of the nucleon in terms of quarks and gluons has been the goal of intense investigations during the last decades. The determination of strangeness is challenging and the only way of determining the strange distribution accurately from data is to improve the semi-inclusive information. This talk is focused on the determination of the strange sea contribution to the nucleon spin through the pseudo-scalar method using semi-inclusive Kaon detection technique with CLAS12 at Jefferson Lab. A Ring Imaging CHerenkov (RICH) detector is under construction and will be used for pion-kaon-proton separation. [Preview Abstract] |
Saturday, January 28, 2017 11:33AM - 11:45AM |
B12.00005: Deeply Virtual Compton Scattering (DVCS) Run (E12-06-114) in Hall A of Thomas Jefferson National Accelerator Facility (TJNAF) Bishnu Karki Generalized Parton Distributions (GPDs) provide a information about transverse position and longitudinal momentum distribution of partons in the nucleon along with the correlation between transverse position and longitudinal momentum of partons. GPDs also provide access to the contribution of orbital momentum of partons to nucleon total spin. The DVCS is one of the favorite reaction to measure the GPDs because it is simplest process that can be described in terms of GPDs. DVCS refers to scattering of virtual photon off the nucleon ($\gamma^* N \rightarrow \gamma N$). The DVCS experiment (E12-06-114) in Hall A will be running again in Fall 2016, to complete proposed DVCS kinematics. We use the polarized electron beam from CEBAF with energy ranging from 8 GeV to 11 GeV and measure high statistics polarized and unpolarized cross section of H(e,e'$\gamma$)p and map it to extract GPDs of proton. The wide range of $Q^2$ scan (2.7$\leq Q^2\geq$9 $GeV^2$) for $x_B$ ranging from 0.3 to 0.6 are performed. The $Q^2$ dependence of the cross section allows one to quantify the contribution of higher twist terms. In this talk the status of experiment will be presented. [Preview Abstract] |
Saturday, January 28, 2017 11:45AM - 11:57AM |
B12.00006: ABSTRACT WITHDRAWN |
Saturday, January 28, 2017 11:57AM - 12:09PM |
B12.00007: Confirming the Potential of Systems Containing Strangeness for 3D Structure Studies of the Proton Salina Ali, Tanja Horn, Marco Carmignotto The additional flavor degree of freedom in kaon electroproduction provides a unique opportunity to study the mechanism underlying strangeness production and the transition from hadronic to partonic degrees of freedom in exclusive processes. At sufficiently high energies, where soft non-perturbative and hard physics have been shown to factorize, the Generalized Parton Distributions provide a spatial tomography of the nucleon. The applicability of this formalism can be experimentally verified. The E12-09-011 experiment at the 12 GeV Jefferson Lab aims to test the expected approach of the hard scattering regime through precision measurements of the fully separated exclusive kaon production cross section, and in particular the relative contributions and kinematic dependencies of the longitudinal and transverse cross sections. The longitudinal cross section also allows one to test the kaon pole dominance and could allow for kaon form factor extractions. In this talk, I will present the current status and discuss the outlook on future studies of strange quarks with kaon production as well as the particle identification requirements, and possible kaon form factor extractions at a 12-GeV Jefferson Lab. [Preview Abstract] |
Saturday, January 28, 2017 12:09PM - 12:21PM |
B12.00008: Pion and kaon structure functions at 12 GeV JLab and EIC Tanja Horn Pions and kaons are, along with protons and neutrons, the main building blocks of nuclear matter. They are connected to the Goldstone modes of dynamical chiral symmetry breaking, the mechanism thought to generate all hadron mass in the visible universe. The distribution of the fundamental constituents, the quarks and gluons, is expected to be different in pions, kaons, and nucleons. However, experimental data are sparse. As a result, there has been persistent doubt about the behavior of the pion's valence quark structure function at large Bjorken-x and virtually nothing is known about the contribution of gluons. A 12 GeV JLab experiment using tagged DIS may contribute to the resolution of the former. The Electron-Ion Collider with an acceptance optimized for forward physics could provide access to structure functions over a larger kinematic region. This would allow for measurements testing if the origin of mass is encoded in the differences of gluons in pions, kaons, and nucleons, and measurements testing assumptions used in the extraction of structure functions and the pion and kaon form factors. Electroweak measurements at an EIC would also potentially allow to disentangle the role of quark flavors at high x. In this talk we will discuss the prospects of such measurements. [Preview Abstract] |
Saturday, January 28, 2017 12:21PM - 12:33PM |
B12.00009: $\bar{{d}}/\bar{{u}}$ Ratio in the Proton at Seaquest Daniel Morton The Fermilab E906 SeaQuest experiment measures muons produced from a 120 GeV proton beam incident on liquid Hydrogen, Deuterium and solid C, Fe and W targets. Muons produced through the Drell Yan process are used to measure nuclear effects, in particular for light sea quarks that the SeaQuest spectrometer is optimized to measure. The ratio of $\bar{{d}}$to $\bar{{u}}$ quarks was expected to be one when only considering gluon splitting, but was found to deviate from that significantly in past experiments. Using the ratios of deuterium to hydrogen cross sections, the ratio of $\bar{{d}}/\bar{{u}}$ quarks will be extracted for Bj\"{o}rken x values up to .45. This probes a higher x region than previous experiments. [Preview Abstract] |
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