Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session CB: Deep Inelastic Scattering, Structure Functions, and Double Spin Asymmetries |
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Chair: Michael McCracken, Washington and Jefferson College Room: Sweeny B |
Thursday, November 4, 2010 8:30AM - 8:42AM |
CB.00001: Nuclear Scaling and the EMC Effect Douglas Higinbotham For over a quarter century, scientists have tried to understand the unexpected structure in the deep-inelastic electron scattering cross section ratios of heavy nuclei to deuterium: a phenomenon known as the EMC effect. Results of recent Jefferson Lab EMC effect measurements, as well as recent nuclear scaling measurements, have both been attributed to the local nuclear environment and not properties of the bulk nuclear system. Motivated by this observation, we have found a phenomenological relationship between the magnitude of the nuclear scaling (Q$^2 > 1$ [GeV/c]$^2$ and $x_B > 1$) and slope of the EMC effect in valence quark region $(0.3 < x_B < 0.7)$. [Preview Abstract] |
Thursday, November 4, 2010 8:42AM - 8:54AM |
CB.00002: Drell-Yan Processes and the Flavor-dependent EMC Effect Jen-Chieh Peng, Dipangkar Dutta, Ian Cloet, David Gaskell Recently, a new calculation of the modifications of nucleon quark distributions in nuclear medium has been reported by Clo\"{e}t, Bentz and Thomas. This calculation, based on the Nambu-Jona-Lasinio model for describing the coupling of the quarks in the bound nucleons to the scalar and vector mean fields inside a nucleus, has a novel prediction that the $u$ and $d$ quarks have distinct nuclear modifications for $N\neq Z$ nuclei. We discuss the possibility to test this calculation using the pion-induced Drell-Yan processes. Calculations for various experimental observables in pionic Drell-Yan processes using the model by Clo\"{e}t et al. are compared with existing data. It is shown that pion-induced Drell-Yan experiments on nuclear targets can provide a very stringent test. Predictions for possible future pion-induced Drell-Yan experiments are also presented. [Preview Abstract] |
Thursday, November 4, 2010 8:54AM - 9:06AM |
CB.00003: Quasielastic to Deep Inelastic Scattering: Results from Jefferson Lab E02-019 Donal Day, Nadia Fomin, John Arrington Jefferson Lab experiment E02-019 measured inclusive cross-sections at momentum transfers from 2.5 to 9 GeV/c$^2$ for several light and heavy nuclei. The transition from quasielastic to deep inelastic scattering is observed. We have applied target mass corrections to the extracted $F_2$ structure functions for all nuclei and obtained the structure function fall-off at $x>1$, which has previously only been determined for a limited range in $x$ and for much larger values of $Q^2$. The analysis procedure will be detailed and results presented. We have also obtained measurements of 2N correlations in nuclei via cross section ratios to deuterium. Additionally, ratios to $^3He$ will be presented, measured at higher $Q^2$ values than the most recent results from CLAS. Plans for future measurements will briefly be discussed. [Preview Abstract] |
Thursday, November 4, 2010 9:06AM - 9:18AM |
CB.00004: Neutron Structure Functions at Large $x$ from CLAS Measurements on Deuterium Sebastian Kuhn The CLAS collaboration has measured inclusive structure functions in the resonance region and at large $x$ in electron scattering on polarized and unpolarized deuterium targets. In the unpolarized case, we have used a novel spectator tagging method to extract, for the first time, the neutron structure function $F_{2n(x,Q^2)}$ nearly free of kinematic smearing and nuclear model uncertainties. In the polarized case, the spin structure functions $g_1$ and $A_1$ of the neutron were extracted using a new unfolding procedure, yielding the first data of this kind in the resonance region. In this talk, the techniques employed will be discussed and the results of both experiments will be presented. [Preview Abstract] |
Thursday, November 4, 2010 9:18AM - 9:30AM |
CB.00005: Perturbative and non-perturbative contributions to light flavor asymmetry in the proton sea Mary Alberg, Tyler Matossian We consider both perturbative and non-perturbative contributions to the Bjorken-$x$ dependence of the $\bar{d}$ and $\bar{u}$ distributions in the proton sea. The non-perturbative contribution is described by a meson cloud model which includes a Fock state expansion of the proton in terms of meson-baryon pairs. The perturbative contribution is described by a statistical model which uses Fock states of quarks, antiquarks and gluons to represent the parton distributions of the ``bare'' hadrons in the meson cloud. We compare our results to the E866 data for $\bar{d}(x)-\bar{u}(x)$ and $\bar{d}(x)/\bar{u}(x)$. [Preview Abstract] |
Thursday, November 4, 2010 9:30AM - 9:42AM |
CB.00006: ABSTRACT WITHDRAWN |
Thursday, November 4, 2010 9:42AM - 9:54AM |
CB.00007: Measurement of Double Spin Asymmetry $A_{LT}$ in Semi-Inclusive Pion Electroproduction on a Transversely Polarized $^3$He Target Jin Huang Double spin asymmetry $A_{LT}$ for the neutron was measured for the first time in Hall A at Jefferson Lab in semi-inclusive deep inelastic deep inelastic $^{3}He^{\uparrow}(\overrightarrow{e},e'\pi^{+/-})X$ reactions, using a 6 GeV polarized electron beam on a transversely polarized 3He target. The produced pions were detected in coincidence with the scattered electrons by a high-resolution spectrometer and a BigBite spectrometer. Kinematic coverage was focused on the valence quark region, $x \sim 0.1$-$0.4$, at $Q^2 \sim 1$-$3(\mathrm{GeV}/c)^2$. When combined with the world data, the new data will provide constraints on the $g^{q}_{1T}$ distribution functions, which describe the longitudinal polarization of up and down quarks for a transversely polarized nucleon. Current data analysis progress and preliminary results will be presented. [Preview Abstract] |
Thursday, November 4, 2010 9:54AM - 10:06AM |
CB.00008: Double Spin Asymmetries, $A_{LL}$, for Di-hadrons in PHENIX Cameron McKinney The Relativistic Heavy Ion Collider (RHIC), through its polarized proton-proton collisions, provides leading order access to $\Delta$G, the gluon contribution to the proton spin. Previous measurements have shown $\int\Delta G(x) dx$ to be consistent with zero in the Bjorken-x range of 0.05 to 0.2, whereas there is presently no measurement constraining $\Delta$G (x) for x below or above this range. The Muon Piston Calorimeter provides the opportunity to expand the constrained range by allowing measurements of double spin asymmetries for azimuthally-separated pairs of $\pi^{0}'s$ at forward rapidity, $3.1<=|\eta|<=3.9$, for $\sqrt{s}$=200 GeV and 500 GeV data taken in 2009. We present PYTHIA simulations studying the kinematics and possible asymmetries from di-hadron production at RHIC. [Preview Abstract] |
Thursday, November 4, 2010 10:06AM - 10:18AM |
CB.00009: Measurement of Double Longitudinal Spin Asymmetry, A$_{LL}$, for Inclusive $\pi^{0}$ Production at Forward Rapidity in PHENIX for $\sqrt{s}$=200 and 500 GeV Scott Wolin The Relativistic Heavy Ion Collider (RHIC) is the world's only source of polarized proton-proton collisions which provides access at leading order to $\Delta$ G(x), the gluon contribution to the proton spin. Previously, PHENIX has only been sensitive to truncated moments of $\Delta$ G over the limited Bjorken-x range of 0.05 $<$ x $<$ 0.2, leaving the low and high-x spin contributions unconstrained. While the $\Delta$ G(x)$\approx$ 0 scenario has not been ruled out by the data, the scenario with $\Delta$ G(x)$\ne$ 0 but with vanishing truncated moment, $\int_{0.05}^{0.2}G(x)dx=0$, due to a node in the functional form of $\Delta$ G(x), is also consistent with the data. With the successful commissioning of the Muon Piston Calorimeter (MPC) at forward rapidity, di-hadron measurements with hadrons at both forward and central rapidities are now possible in PHENIX. Two forward hadrons extend the kinematic coverage for gluons down to x$\sim10^{-3}$. Such an asymmetry measurement for di-hadrons and single hadrons at forward rapidity can be used to improve the constraints on $\Delta$ G(x) at small x. Here, we discuss the status of these measurements at forward rapidity in PHENIX using the MPC. [Preview Abstract] |
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