Bulletin of the American Physical Society
2019 Fall Meeting of the APS Division of Nuclear Physics
Volume 64, Number 12
Monday–Thursday, October 14–17, 2019; Crystal City, Virginia
Session FH: Mini-Symposium: New Results from CLAS12 II |
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Chair: Volker Burkert, Jefferson Laboratory Room: Salon B |
Tuesday, October 15, 2019 10:30AM - 10:42AM |
FH.00001: First Measurements of the Inclusive Electron Scattering off Protons with CLAS12 Nikolay Markov Electron scattering data off protons from the CLAS12 detector has recently become available and covers a wide kinematic range in W up to 4 GeV and Q$^{\mathrm{2}}$ up to 10 GeV$^{\mathrm{2}}$, offering new opportunities to explore inclusive, semi-inclusive, and fully exclusive reactions. A study that aims to extract the inclusive electroproduction cross sections from the CLAS12 fall 2018 data collected at a beam energy of 10.6 GeV from an unpolarized liquid-hydrogen target is now in progress. ~Preliminary results will be presented and future work plans discussed. The data on inclusive electron scattering cross sections in the resonance region at high photon virtualities, Q$^{\mathrm{2}}$ \textgreater 5.0 GeV$^{\mathrm{2}}$, will become available. In combination with the existing CLAS results on N* electrocouplings, they will shed light on the behavior of the parton distributions in the resonance region of large x$_{\mathrm{B}}$ and offer valuable input for quark-hadron duality studies. The comparison of inclusive electron scattering data from CLAS12 with the available world data is essential for the understanding and validation of the CLAS12 performance in terms of the electron identification and efficiency evaluation. [Preview Abstract] |
Tuesday, October 15, 2019 10:42AM - 10:54AM |
FH.00002: MesonEx:meson spectroscopy with quasi-real photons in CLAS12 Kenneth Hicks, Marco Battaglieri, Raffaella Devita, Derek Glazier A broad program to study meson spectroscopy in the light quark sector with the CLAS12 experiment in Hall B at Jefferson Laboratory has been proposed with the goal of searching for exotic mesons and studying poorly known and rare states, such as scalars and strange mesons. For this purpose, the experiment uses quasi-real photons produced by 10.6 GeV electrons scattering off a proton target and detected at small angles (2.5-4.5 deg) in the CLAS12 Forward Tagger. In these kinematics the virtual photon that is produced has very low four-momentum transfer, Q2, and can be considered as quasi-real. This photon has a significant degree of linear polarization that can be determined event-by-event from the electron scattering kinematics and exploited in the study of the hadronic final states via Partial Wave Analyses (PWA) to extract the contribution of individual resonances. After completing the commissioning in February 2018, the experiment started the production phase, completing an extensive period of data taking between 2018 and 2019, collecting about 300 mC of charge corresponding to an integrated luminosity of 0.4/pb. In this talk first results from a selection of final states will be presented [Preview Abstract] |
Tuesday, October 15, 2019 10:54AM - 11:06AM |
FH.00003: Excited Nucleon Spectrum and Structure Studies with CLAS12 Daniel Carman The $N^*$ program in Hall B at Jefferson Laboratory studies the spectrum and structure of excited nucleon states employing exclusive electroproduction reactions. This effort is an important avenue to explore strongly interacting systems of QCD. The CLAS detector has provided the dominant part of the available world data on $\pi N$, $\eta N$, $\pi \pi N$, and $K^+Y$ electroproduction in the nucleon resonance region for $Q^2$ up to 5 GeV$^2$. These data have yielded the only results available on the $Q^2$ evolution of the electrocoupling amplitudes for most $N^*$ states up to $W$=1.8 GeV to explore their internal structure. Starting in early 2018, the $N^*$ program using the new CLAS12 spectrometer began. These studies will probe $N^*$ states in the mass range up to $W$ of 3 GeV and $Q^2$ from 0.1 GeV$^2$ to 12 GeV$^2$, thus providing a means to access $N^*$ structure information spanning a broad range of distance scales. Quasi-real photoproduction studies are also planned to search for additional hybrid baryon states, for which the glue serves as an active structural component. In this talk the results of the ongoing analysis of the data collected from CLAS12 associated with the $N^*$ program will be reviewed to highlight the current status and future plans. [Preview Abstract] |
Tuesday, October 15, 2019 11:06AM - 11:18AM |
FH.00004: Exclusive $\phi$ Meson Electroproduction with CLAS12 Brandon Clary The Continuous Electron Accelerator Facility Large Angle Spectrometer detector (CLAS12) at Jefferson Lab in Virginia has completed a successful period of data acquisition starting in early 2018 of a longitudinally polarized 10.6 GeV electron beam on a 5 cm unpolarized liquid hydrogen target. A program to study exclusive $\phi$ meson electroproduction is now underway as this is an ideal channel for quantifying the gluonic properties of the nucleon. This analysis focuses on the exclusive reaction $e p \to epK^+K^-$. The analysis strategy consists of 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 $x_{B}$. This talk will focus on reviewing the current state of the analysis and future plans for the exclusive $\phi$ meson channel with CLAS12. [Preview Abstract] |
Tuesday, October 15, 2019 11:18AM - 11:30AM |
FH.00005: Study of Kaon Identification for Hyperon Photoproduction in JLab's Hall B CLAS12 Isabella Illari, William Phelps The CLAS12 physics program is involved in the study of baryon spectroscopy in quasi-real photoproduction of a large variety of final states, and includes the photoproduction of singly, doubly and triply strange hyperons. The photoproduction of the very strange hyperon, the $\Omega^-$, is of particular interest. Its photoproduction cross section is unknown. Furthermore, the dynamics of the $\Omega^-$ photoproduction is unclear, as there are no strange quarks in the initial state while there are three in the final state. The available theoretical predictions for the $\Omega^-$ hyperon photo- and electroproduction cross section vary from 1 to 300 pb. As of today, there is only an upper limit of the cross section ($\sigma_{tot} < 17$ nb at 20 GeV) reported by SLAC. To identify the final state for $\gamma p \to \Omega^- K^+ K^+K^0$ the minimal requirement is to detect three kaons: two $K^+$ and one $K^0_s$. The latter is identified by its decay to $\pi^+\pi^-$. We will discuss our study of kaon identification in CLAS12 based on Monte Carlo simulations and real data collected by Run Group A, which used a $\sim$11 GeV beam incident on a liquid hydrogen target. [Preview Abstract] |
Tuesday, October 15, 2019 11:30AM - 11:42AM |
FH.00006: ABSTRACT WITHDRAWN |
Tuesday, October 15, 2019 11:42AM - 11:54AM |
FH.00007: Deeply virtual Compton scattering with CLAS12 Angela Biselli The Generalized Parton Distributions (GPDs) have emerged as a universal tool to describe hadrons in terms of their elementary constituents, the quarks and the gluons. Deeply Virtual Compton Scattering (DVCS) on nucleons or nuclei ($N$), $e N \rightarrow e' N' \gamma$, is one of the simplest processes that can be described in terms of GPDs. The amplitudes of DVCS and Bethe-Heitler, process where a photon is emitted by the incident or scattered electron, can be accessed via cross section measurements or exploiting their interference which give rise to spin asymmetries. Spin asymmetries, cross sections and cross-section differences can be connected to different combinations of GPDs. This talk focuses on data currently being taken at 11 GeV in Hall B with the CLAS12 detector, with polarized beam and a liquid deuterium target. Preliminary analysis of the data towards the extraction of coherent DVCS asymmetries on the deuteron will be presented. Completion of this work will contribute to our understanding of the 3D partonic structure of nuclei. [Preview Abstract] |
Tuesday, October 15, 2019 11:54AM - 12:06PM |
FH.00008: Measuring Deeply Virtual Compton Scattering on the Neutron with CLAS12 at Jefferson Lab Katheryne Price A key step towards understanding nucleon structure in terms of generalized parton distributions (GPDs) is the measurement of deeply virtual Compton scattering on the neutron (nDVCS). This talk will report on a new experiment, currently ongoing at Jefferson Lab, utilizing the upgraded 11 GeV CEBAF polarized electron beam, the CLAS12 detector, and a liquid deuterium target. We aim to measure beam-spin asymmetries for nDVCS ($ed\to e'n\gamma(p)$). The status of the data taking and of the nDVCS analysis, as well as the performances of the detectors and the quality of the data will be presented. This beam-spin asymmetry measurement, when taken with complementary pDVCS measurements, gives us access to quark total angular momentum. As quark GPDs are only accessible in linear combinations within proton and neutron GPDs, measurement of E via nDVCS will also allow us to perform quark flavor separation of GPDs, resulting in a more complete GPD picture of nucleon structure. [Preview Abstract] |
Tuesday, October 15, 2019 12:06PM - 12:18PM |
FH.00009: Experimental Determination of the Free Neutron F$_{2}$ at Large Bjorken-x: The BONuS12 Proton Recoil Detector Sooriyaarachchilage Nadeeshani While the proton F$_{2}$ structure function has been studied extensively through inelastic electron-proton scattering, much less is known about neutron structure due to the unavailability of high density, free neutron targets. The BONuS12 experiment was proposed to measure the neutron F$_{2}$ on a nearly free neutron within a weakly bound deuteron target via the spectator tagging method. Tagging the slow backward moving spectator protons minimizes both off-shell and final-state interaction effects with the measured proton momentum used to correct for the initial-state momentum of the struck neutron. The recoil detector will be used to detect spectator protons with momenta 70 $<$ P$_{s}$ $<$ 150 MeV/c and the CEBAF Large Acceptance Spectrometer (CLAS12) to detect the scattered electrons. In this talk, I will present the design and construction of the recoil detector (RTPC), which was lead by Hampton University. [Preview Abstract] |
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