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 FE: Mini-symposium: Photoproduction and Electroproduction of Hadrons II |
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Chair: Kyungseon Joo, University of Connecticut Room: Hilton King's 1 |
Friday, October 26, 2018 9:00AM - 9:15AM |
FE.00001: Di-hadron correlations in SIDIS at CLAS12 Anselm Vossen The observation of azimuthal correlations in di-hadron production in SIDIS provides for a versatile probe of the nucleon structure. |
Friday, October 26, 2018 9:15AM - 9:30AM |
FE.00002: SIDIS Pion Beam Spin Asymmetries with CLAS 12 at 10.6 GeV Stefan Diehl The CLAS12 detector started data taking with a polarized 10.6 GeV electron beam at Jefferson Laboratory (JLab) this February. One of the first quantities which could be extracted from the new data is the moment ALUsin(φ) corresponding to the polarized electron beam spin asymmetry in semi-inclusive deep inelastic scattering. ALUsin(φ) is a twist-3 quantity which provides information about the quark gluon correlations. The study was performed with a 10.6 GeV longitudinally polarized electron beam and an unpolarized liquid hydrogen target. The talk will present a simultaneous study of all three pion channels (π+, π0 and π-) over a large kinematic range with virtualities Q² ranging from 1 GeV² up to 8 GeV². The measurement in a large range of z, xB, pT and Q², including up to now not measured kinematic regions, enables a comparison with different reaction models. The results will be compared to previous studies at an electron beam energy of 5.5 GeV with CLAS6. |
Friday, October 26, 2018 9:30AM - 9:45AM |
FE.00003: Neutral Pion SIDIS Multiplicity with CLAS12 Giovanni Angelini, Harut Avagyan
The CLAS12 spectrometer (JLab) is an ideal detector for the study of nucleon’s imaging via the analysis of multidimensional distributions of final-state hadrons in semi-inclusive deep inelastic scattering (SIDIS). In the current fragmentation region, the structure functions parametrizing the cross-section can be expressed in terms of the convolution of universal functions. These universals functions are the so-called transverse momentum dependent partonic distribution functions and the fragmentation functions. The former describes quarks distribution in terms of their momenta while the latter describes the hadronization process of quarks. |
Friday, October 26, 2018 9:45AM - 10:00AM |
FE.00004: Exclusive neutral pion electro-production cross-sections from experiment E12-06-114 at JLab 12 GeV Julie Roche Generalized Parton Distribution (GPDs) functions describe the correlation between the spatial distribution of the quarks and its longitudinal momentum fraction. Their definition in the mid 1990's has revolutionized our approach to the description of the internal structure of the nucleon. The study of the GPDs together with the study of similar quantities are at the fore-front of today hadronic physics enterprise. In consequences, deeply virtual photon (DVCS) and meson (DVMP) electroproduction have attracted much interest. In this talk, I will present neutral pion production cross-sections measured in Hall A at Jefferson Lab with the newly updated electro beam. These data will extend the Q2 range at xBjorken=0.36 up to 4.5 GeV2. They will further test the limits of factorization concepts essential to the introduction of the GPD concept. They will also further test model that uses transversity GPDs to describe data at lower Q2.
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Friday, October 26, 2018 10:00AM - 10:15AM |
FE.00005: First Observation of Beam Spin Asymmetries in $K^+$ SIDIS David Riser, Kyungseon Joo Beam spin asymmetry (BSA) measurements of semi-inclusive deeply inelastic scattering (SIDIS) for charged and neutral pions have already shown that $A_{LU}^{\sin\phi_h}$ is not consistent with zero at JLab 6 GeV kinematics. |
Friday, October 26, 2018 10:15AM - 10:30AM |
FE.00006: Exclusive $\phi$ Meson Electroproduction with CLAS12 Brandon A Clary The CLAS12 detector completed in May 2018 its first data taking following the Jefferson Laboratory 12 GeV upgrade. About 3 months of longitudinally polarized electron beam were gathered on a 5 cm long liquid hydrogen target, at beam energies of up to 10.6 GeV and currents up to 75 nA. First rounds of calibration, data quality monitoring, and full reconstruction were achieved. We analyze the exclusive electroproduction of a $\phi$ meson in the Bjorken regime, using its decay into charged Kaons $ep\rightarrow epK^+K^-$. The main goal of this study is the extraction of the longitudinal cross section $t$-slopes as a function of $x_{B}$, which is sensitive to the gluon generalized parton distribution. The analysis strategy consists in two steps: first to establish the approach to the small-size regime by testing model-independent features of the reaction mechanism, such as the $Q^2$-independence of the t-slopes; then in a second step, extracting the gluonic size in the valence region as a function of $x_{B}$. We aim to present preliminary results on the reaction selection using cuts on exclusivity variables, compared to design expectations. |
Friday, October 26, 2018 10:30AM - 10:45AM |
FE.00007: Deeply Virtual Compton scattering with CLAS12 at Jefferson Laboratory (on behalf of the CLAS Collaboration) Guillaume Christiaens While it has been known since the 60s that nucleons are composed of quarks and gluons, very little is understood about the mechanisms responsible for the emergence of nucleons from these partons. Defined in the 90s, Generalized Parton Distributions (GPDs) provide the opportunity to obtain a 3-dimensional, tomographic picture of a nucleon. Moreover, GPDs are related, via QCD-based sum rules, to total angular momentum, mass and pressure distributions inside the nucleon. GPDs are experimentally accessible via the deeply virtual Compton scattering (DVCS), i.e. the absorption of a highly virtual photon by the proton and the subsequent emission of a high-energy photon. At Jefferson Lab, the brand new CLAS12 spectrometer has been commissioned and has collected its first DVCS data with a 10.6 GeV continuous electron beam in winter 2017 - spring 2018. Its central part, containing the cylindrical silicon and micromegas trackers within a 5T-solenoidal field surrounding the liquid hydrogen target, is ideal to detect the recoil proton. The forward detectors, placed in a toroidal magnetic field, detect the associated scattered electron and high energy photon. We will present a first look at the DVCS data collected so far with CLAS12, and will show projections for the full run. |
Friday, October 26, 2018 10:45AM - 11:00AM |
FE.00008: Deeply Virtual Compton Scattering with Jefferson Lab’s CLAS12 at 6.4 GeV Polarized Electron Beam Joshua Artem Diaz Tan By correlating a nucleon constituent's momentum fraction to its position in the transverse plane, Generalized Parton Distributions (GPDs) provide a comprehensive framework for describing the nucleon structure. Deeply Virtual Compton Scattering (DVCS) provides the cleanest access to the 3D imaging of the nucleon structure encoded in the GPDs. In the DVCS process, a quark's interaction in the nucleon with the virtual photon from the scattered electron results in the nucleon’s emission of a real photon. The high luminosity, highly polarized electron beam accelerator of Jefferson Lab and the recently completed CLAS12 detector system in Hall B offer an ideal environment for DVCS experiment. With a large acceptance, CLAS12 is equipped with detectors optimally sensitive to DVCS final state particles. First DVCS data were collected with CLAS12 during the spring of 2018 at 6.4 GeV and at 10.6 GeV electron beam energies, using liquid hydrogen target. We will present a first look at DVCS data collected from this run period at 6.4 GeV beam energy, which serve as the checkpoint for evaluating the quality of the corrections and analysis for CLAS12 DVCS when compared with the well-established results of the previous CLAS DVCS experiments performed close to 6.4 GeV electron beam energy. |
Friday, October 26, 2018 11:00AM - 11:15AM |
FE.00009: Timelike Compton Scattering with CLAS12 at Jefferson Lab Pierre Chatagnon Generalized Parton Distributions (GPDs) describe the correlations between the longitudinal momentum and the transverse spatial position of the partons inside the nucleon. They give access to the contribution of the orbital momentum of the quarks to the nucleon spin. |
Friday, October 26, 2018 11:15AM - 11:30AM |
FE.00010: Imaging quark transverse spin distributions via exclusive pseudoscalar meson electroproducton with CLAS at Jefferson Lab. Paul Stoler, Valery Kubarovsky One of the major experimental research programs of the Jefferson Lab CLAS Collaboration is deeply virtual pseudoscalar meson electroproduction. These reactions are uniquely sensitive to the transversity generalized parton distributions (GPD) ET, and HT, which are related to quark transverse spin densities in the nucleon. By observing different mesons one can obtain distributions for each quark flavor. Experimental results on exclusive π0 and η electroproduction at electron energy near 6 GeV, obtained by the CLAS collaboration, will be presented, and discussed in terms of their separation into generalized form factors (GFF) and GPDs of u and d quark flavors. These in turn can be related to the density of polarized u and d quarks in an unpolarized nucleon. The resulting analysis relating to transversity spin densities of the nucleon’s u and d quark flavors will be presented. Further plans for measurements at higher beam energies at CLAS, and the planned analysis in terms of GFFs, and GPDs will be discussed. |
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