Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session CF: Mini-symposium on Studying Quantum Chromodynamics at an Electron-Ion Collider I |
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Chair: Shoichi Sasaki, Tohoku University Room: Hilton King's 2 |
Wednesday, October 24, 2018 7:00PM - 7:30PM |
CF.00001: The electron-ion collider as a next-generation facility for the study of QCD Invited Speaker: Ralf Seidl The electron-ion collider, EIC, has been identified as the top new construction project by the 2016 long range plan of the nuclear science advisory council in the US. Since then the US department of energy office of science has ordered a review of the science case by the national academy of sciences. The report is expected to be made public before the DNP/JPS fall meeting and is generally expected to be quite favorable. This will then lead to the mission need statement by the DOE and start the formal process to build an EIC. At present there are two proposals either augmenting the existing polarized proton and heavy Ion accelerator at Brookhaven National Lab with a polarized electron ring or add a polarized hadron machine to the existing CEBAF facility. The physics goals of an EIC are versatile, from precision measurements of the spin structure of the nucleon, over the three dimensional position and momentum picture of the nucleon to the potential discovery of a new regime at very high gluon densities in nucleii. |
Wednesday, October 24, 2018 7:30PM - 7:45PM |
CF.00002: The BONuS12 Experiment Measuring the Neutron Structure Function at large Bjorken-x JIWAN POUDEL The BONuS experiment using Jefferson Lab’s CLAS detector studied the nearly free neutron structure by using the spectator tagging technique. The backscattered spectator protons in d(e, e′p)X deep-inelastic scattering with momenta <100 MeV/c are detected by a Radial Time Projection Chamber (RTPC), thereby selecting electron-scattering events off nearly free neutrons. The recent upgrade of Jefferson Lab to 11 GeV electron beam energy will extend the kinematic range to a higher Bjorken x of ∼ 0.85. The collaboration is presently preparing the BONuS12 experiment, which is expected to take data in early 2020 using the upgraded CLAS12 detector. A new and enlarged RTPC is being built which utilizes a new drift gas and a new data acquisition system, and new simulation and particle tracking software is being developed. This presentation includes a status update of the BONuS12 experiment with an overview of the spectator tagging technique to study the free neutron structure function. |
Wednesday, October 24, 2018 7:45PM - 8:00PM |
CF.00003: Investigating the EMC Effect in Highly-Virtual Nucleons at Jefferson Lab Efrain P Segarra The EMC effect, the phenomenon by which quark distributions are modified in bound nucleons, has defied explanation since its discovery over 30 years ago. Recently, there have been indications, experimentally and theoretically, that the EMC effect may be linked to high-momentum nucleons. Rather than the EMC effect being caused by a modest modification in all nucleons, it is possible that highly virtual nucleons are modified substantially. BAND (Backward Angle Neutron Detector) is an experiment in early 2019 with Run Group B at Jefferson Lab Hall B to search for medium-modification in high-momentum nucleons. By using a method of spectator-tagging, one can tag on the virtuality of the struck proton to study modification in deep inelastic scattering. In my talk, I will present the EMC effect, discuss its possible connection to high momentum nucleons, and describe how the BAND will select on these nucleons (spectator-tagging) to extract medium-modification effects. Finally, I will discuss the construction and calibration phase of the BAND, which is ongoing in Hall B, as well as expected sensitivities based on Geant4 simulation package. |
Wednesday, October 24, 2018 8:00PM - 8:15PM |
CF.00004: Abstract Withdrawn
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Wednesday, October 24, 2018 8:15PM - 8:30PM |
CF.00005: Quark contribution to the proton spin from 2+1+1-flavor lattice QCD Huey-Wen Lin We present the first high-statistics chiral-continuum extrapolated up, down and strange quark spin contribution to the proton spin using lattice QCD. We use up to eleven ensembles of 2+1+1-flavors of Highly Improved Staggered Quarks (HISQ) generated by the MILC collaboration, which covers 4 lattice spacings covering \{0.15,0.12,0.09,0.06\} fm and two the physical pion mass. High-statistics estimates on each ensemble allow us to quantify systematic uncertainties and perform a simultaneous chiral-continnum extrapolation in the lattice spacing and light-quark masses. Our final results are $\Delta u = 0.777(25)$, $\Delta d = -0.438(18)$, and $\Delta s = -0.053(8)$, adding up to a total quark contribution to proton spin of $\sum_{q=u,d,s} (\frac{1}{2} \Delta q) = 0.143(31)(29)$. |
Wednesday, October 24, 2018 8:30PM - 8:45PM |
CF.00006: First Monte Carlo Global Analysis of Nucleon Transversity with Lattice QCD Constraints Wally Melnitchouk, Huey-Wen Lin, Alexei Prokudin, Nobuo Sato, Harvey F Shows III We report on the first global QCD analysis of the quark transversity distributions in the nucleon from semi-inclusive deep-inelastic scattering (SIDIS), using a Monte Carlo method based on nested sampling and constraints on the isovector tensor charge gT from lattice QCD. A simultaneous fit to the available SIDIS Collins asymmetry data is compatible with gT values extracted from a comprehensive reanalysis of existing lattice simulations, in contrast to previous analyses, which found significantly smaller gT values. |
Wednesday, October 24, 2018 8:45PM - 9:00PM |
CF.00007: Iso-vector axial, scalar and tensor charges of the nucleon from 2+1 flavor domain wall QCD Natsuki Tsukamoto, Shoichi Sasaki We present results for the nucleon iso-vector charges from dynamical lattice QCD with domain-wall quarks. |
Wednesday, October 24, 2018 9:00PM - 9:15PM |
CF.00008: Gluon structure of hadrons and nuclei from lattice QCD Phiala Shanahan The construction of an electron-ion collider (EIC) designed to reveal new information about the gluon structure of hadrons and nuclei is planned, with data taking expected within the next decade. I will describe recent lattice QCD studies of the gluon generalised form factors of both hadrons and light nuclei, motivated by providing Standard Model predictions for quantities to be measured for the first time at the future EIC. I will focus in particular on the transversity gluon structure quantities which are of interest since they are purely gluonic and do not mix with quark distributions. In light nuclei these quantities moreover provide a clean signature of non-nucleonic gluon degrees of freedom, which have not yet been observed experimentally but are cleanly resolved in the lattice calculations. |
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