Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session E13: Minisymposium: Spin Structure of the NucleonFocus
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Sponsoring Units: DNP GHP Chair: Xiaochao Zheng, University of Virginia Room: Roosevelt 5 |
Saturday, January 28, 2017 3:30PM - 4:06PM |
E13.00001: Chiral effective-field theory of the nucleon spin structure Invited Speaker: Vladimir Pascalutsa I will review the recent chiral EFT calculations of the nucleon (spin) structure functions at low $Q^2$, confronted with the Jefferson Lab measurements. The moments of the structure functions correspond with various polarizabilities, and I will explain why one of them --- $\delta_{LT}$ --- is especially interesting. I will also discuss how the spin structure functions at low $Q$ enter in the atomic calculations of the hyperfine splittings and how they are impacting the ongoing experimental program at PSI (Switzerland) to measure the ground-state hyperfine splitting of muonic hydrogen. [Preview Abstract] |
Saturday, January 28, 2017 4:06PM - 4:18PM |
E13.00002: ABSTRACT WITHDRAWN |
Saturday, January 28, 2017 4:18PM - 4:30PM |
E13.00003: Incorporating metal into polarized $^3$He target cells Sumudu K. Katugampola, Daniel J. Matyas, Yunxiao Wang, William A. Tobias, Vladimir Nelyubin, Gordon D. Cates An upcoming measurement at Jefferson Laboratory (JLab) of the electric form factor of the neutron will utilize a polarized $^3$He target at high luminosity. While polarized $^3$He targets at JLab have previously been made entirely of glass, we describe progress toward incorporating metal windows for the electron beam. Under the conditions of our targets, very few studies have been done on the spin-relaxation of nuclear-polarized $^3$He on metal surfaces. We have found good performance by using Oxygen Free High Conductivity (OFHC) copper substrates electroplated with gold. The glass-to-metal transitions within our test cells were based on Housekeeper seals. We have further established that Uranium glass (Canary glass) has excellent spin-relaxation properties, and can serve as a transition glass from Pyrex to Aluminosilicate glass (GE180). Another finding was that spin-relaxation properties were sensitive to the manner in which cells were annealed, an important issue because of constraints when annealing cells containing both metal and glass. [Preview Abstract] |
Saturday, January 28, 2017 4:30PM - 4:42PM |
E13.00004: New results on spin structure functions at very low momentum transfers from Hall B in Jefferson Lab Krishna Adhikari In this talk, I will present new results from the Jefferson Lab's EG4 experiment with CLAS detector, which measured the double polarized cross section difference on NH3 and ND3 (with both electron beam and targets longitudinally polarized) down to Q$^{2}$ = 0.02 GeV$^{2}$. From this high precision, and low momentum transfer data, the spin structure $g_{1}$ and its moments are extracted. The new results help us shed more light on the nucleon spin structure in the region of quark-confinement as well as in the transition region between hadronic and partonic degrees of freedom by providing data to test various predictions for moments of structure functions from sum rules and QCD based effective theories such as Chiral Perturbation Theory ($\chi$PT) as well as from phenomenological models. At very low momentum transfers (Q$^{2} \rightarrow 0$), the first moment ($\Gamma_{1}$) of structure function g$_{1}$ is constrained by the GDH sum rule and its $\chi$PT extensions, which makes measurements of g$_{1}$ in this region uniquely interesting. [Preview Abstract] |
Saturday, January 28, 2017 4:42PM - 4:54PM |
E13.00005: The Nucleon Spin Structure Program with CLAS and CLAS12 Sebastian Kuhn Collinear spin structure functions of protons and neutrons (deuterons) have been measured by several high-precision experiments with the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B during Jefferson Lab's 6-GeV era. These experiments have led to new insights on polarized parton distribution functions, higher-twist effects, parton-hadron duality and extensions of real photon sum rules. In my talk, I will show a few highlights of the most recent experimental results and then focus on the program planned for CLAS12 and the 12 GeV era. [Preview Abstract] |
Saturday, January 28, 2017 4:54PM - 5:06PM |
E13.00006: Probing for high momentum protons in $^{\mathrm{4}}$\textit{He} via the $^{\mathrm{4}}$\textit{He(e,e'p)}$^{\mathrm{3}}H$ reaction. Fatiha Benmokhtar, Sophia Iqbal, Nathalian See, Drew Finton, Konrad A. Aniol, Martin Ivanov, Jose M. Udias, Douglas Higinbotham The structure and dynamics of $^{\mathrm{4}}$\textit{He} can be studied through $^{4}$\textit{He(e,e'p)} coincidence measurements at high momentum transfers. Using the Hall A high resolution spectrometers and a cryogenic $^{4}$\textit{He} target, the short range correlation E07-006 and E08-009 experiments held in Hall A of Jefferson Lab measured the entire range of missing momentum from 0.0 GeV/$c$ to 0.9 GeV/$c$. Experimental cross sections for the 3-body breakup $^{4}$\textit{He(e,e'p)}$^{3}H$ up to $P_{miss} \quad =$ 0.632GeV/$c$ at $x_{B} \quad =$ 1.24 and $Q^{\mathrm{2}} \quad =$ 2(GeV/$c)^{\mathrm{2}}$ are reported. The data are compared to Relativistic Distorted Wave Impulse Approximation (RDWIA) calculations. [Preview Abstract] |
Saturday, January 28, 2017 5:06PM - 5:18PM |
E13.00007: Measurement of $W^{\pm}$ single spin asymmetries in polarized $p+p$ collisions at $\sqrt{s}=510$ GeV at RHIC Devika Gunarathne The STAR experiment at RHIC has provided significant contributions to our understanding of the structure of the proton. The STAR experiment is well equipped to measure $W^\pm\rightarrowe^\pm+\nu$ in $\sqrt{s}=510$ GeV longitudinally polarized $p+p$ collisions. The longitudinal single spin asymmetry in W production, $A_L$, measured as a function of decay positron (electron) pseudo-rapidity $\eta$ for $W^+(W^-)$ is sensitive to the individual helicity polarizations of $u$ and $\bar{d}$ ($d$ and $\bar{u}$) quarks. Due to maximal violation of parity during the production, $W$ bosons couple to left-handed quarks and right-handed anti-quarks and hence offer direct probes of their respective helicity distributions in the nucleon. The published STAR $A_L$ results (2011, 2012 data combined) have been used by several theoretical analyses suggesting a significant impact in constraining the helicity distributions of $\bar{u}$, and $\bar{d}$ quarks. In 2013 STAR collected a dataset at $\sqrt{s}=510$ GeV with a total integrated luminosity of $\sim$300 pb$^{-1}$ with an average beam polarization of $\sim$54\%, a figure of merit three times larger than the dataset used by previous analyses. We will present preliminary results of STAR 2013 W $A_L$ measurement at mid-rapidity ($|\eta|<1$) region. [Preview Abstract] |
Saturday, January 28, 2017 5:18PM - 5:30PM |
E13.00008: Measurement of Longitudinal Single-Spin Asymmetries at Forward Rapidity for W Boson Production in Polarized proton+proton Collisions at √s=510 GeV at STAR Amani Krishna The production of W$^{-(+)}$ bosons in polarized proton collisions provides an ideal tool to study the spin-flavor structure of the proton sea quark distributions profiting from the parity violating nature of weak interactions. W$^{-(+)}$ bosons are produced in ${\bar{u}+d}$ (${\bar{d}+u}$) annihilation and can be detected through their leptonic decay mode. The STAR experiment has the ability to detect charged leptons e$^{-(+)}$ at mid and forward rapidity regions. In this analysis we focus on the forward region ($1< $ $\eta$ $< 2$) . The analysis status of the measurement of the longitudinal single-spin asymmetries at forward rapidity for W boson production will be presented based on a data sample collected in 2013 corresponding to an integrated luminosity $\sim$ 250 pb$^{-1}$ with an average beam polarization $\sim$ 54 \%. [Preview Abstract] |
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