Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Q15: Mini-Symposium: Early Science Results from Jefferson Lab 12 GeV ProgramLive Mini-Symposium
|
Hide Abstracts |
Sponsoring Units: GHP Chair: Richard Trotta, The Catholic University of America |
Monday, April 19, 2021 10:45AM - 11:21AM Live |
Q15.00001: Overview of the Jefferson Lab 12 GeV Program Invited Speaker: Raffaella De Vita The Jefferson Lab 12 GeV upgrade was completed in 2017, including the upgrade of the accelerator to achieve a maximum beam energy of 12 GeV, the upgrade of the detector equipment in the existing experimental halls (Hall A, B, and C), and the construction of a fourth end station, Hall D. A broad experimental program has been developed to use the upgraded facility to study the quark and gluon structure of hadrons in the valence region and deepen our understanding of strong interaction in the confinement regime. This talk will review recent results from this program and plans for the future. [Preview Abstract] |
Monday, April 19, 2021 11:21AM - 11:33AM Live |
Q15.00002: Timelike Compton Scattering with CLAS12 at Jefferson Lab Pierre Chatagnon Generalized Parton Distributions (GPDs) are nowadays the subject of an intense effort of research, in the perspective of understanding nucleon spin and its mechanical properties. This talk will highlight the measurement of Timelike Compton Scattering (TCS), which is the time-reversal conjugate process of Deeply Virtual Compton Scattering (DVCS). TCS is the photoproduction of a virtual timelike photon, which then decays into a lepton pair. Experimental studies of DVCS and TCS are complementary. Helicity/spin observables of DVCS give direct access to the imaginary part of combinations of Compton Form Factors (CFFs, related to GPDs), which is also accessed in the TCS initial photon polarization asymmetry, providing a way to test the universality of GPDs. The angular asymmetry of the decay lepton pairs of TCS is related to the real part of the CFF H, itself linked to the pressure distribution inside the nucleon via the D-term. The CLAS12 detector of Jefferson Lab provides the ideal setting to perform a TCS experiment. CLAS12 took data with a 10.6 GeV electron beam on a liquid-hydrogen target in 2018. This talk presents the first-time measurement of TCS photon polarization asymmetry and angular asymmetry and comparisons to model predictions are made. [Preview Abstract] |
Monday, April 19, 2021 11:33AM - 11:45AM Live |
Q15.00003: Measuring Deeply Virtual Compton Scattering off the Neutron with CLAS12 at Jefferson Lab Adam Hobart A key step towards a better understanding of nucleon structure in terms of Generalized Parton Distributions (GPDs) is the measurement of deeply virtual Compton scattering off the neutron (nDVCS; $ed\to e'n\gamma(p)$). , The experimental measurement of the beam-spin asymmetry (BSA) for this process emphasizes mainly the access to the GPD E, which is so far the least constrained of the four leading-twist quark-helicity-conserving GPDs. The knowledge of E provides information on the quark total angular momentum - via the Ji's sum rule - helping completing our picture of nucleon structure. Moreover, the measurement of nDVCS, combined with complementary pDVCS measurements, allows the flavor separation of relevant quark GPDs, accessible as linear combinations of proton and neutron GPDs. This talk will report on an experiment carried at Jefferson Lab in 2019, utilizing the upgraded 10.6 GeV CEBAF polarized electron beam, the CLAS12 detector, and a liquid deuterium target. Details on the data analysis along with preliminary beam-spin asymmetries for nDVCS will be presented. [Preview Abstract] |
Monday, April 19, 2021 11:45AM - 11:57AM Live |
Q15.00004: The First Results From CLAS12 on Inclusive Electron Scattering Nikolay Markov Studies of inclusive electron scattering offer an effective tool for the exploration of the structure of the nucleon. The first results on inclusive electron scattering with CLAS12 at invariant masses of the final state hadrons W\textless 2.5 GeV and photon virtualities 1.0 GeV$^{\mathrm{2}}$ \textless Q$^{\mathrm{2}}$ \textless 9.0 GeV$^{\mathrm{2}}$ will be presented. Owing to the almost 4$\pi $ acceptance of the CLAS12 detector, data have been collected within the broad W-range, from the meson electroproduction threshold up to 2.5 GeV, for any given bin of Q$^{\mathrm{2}}$. This feature is of particular importance for the studies of the inclusive p(e,e')X process in the nucleon resonance region, where the resonance peaks make the data interpolation problematic over the finite bins of W and Q$^{\mathrm{2}}$. The CLAS results on the N* electrocouplings of most resonances with masses \textless 1.8 GeV allow us to evaluate the resonant contributions in the inclusive p(e,e')X process and thus gain insight into the nucleon parton distribution function (PDF) at large x-Bjorken. This p(e,e')X data will also serve as a tool to understand the CLAS12 performance and as a benchmark for the studies of exclusive channels with the CLAS12 detector. [Preview Abstract] |
Monday, April 19, 2021 11:57AM - 12:09PM Live |
Q15.00005: DVCS Cross Section Measurement on Proton at CLAS12 Sangbaek Lee A progress report of the Deeply Virtual Compton Scattering (DVCS) cross-section measurement with a liquid hydrogen target at CLAS12 is presented. The proton DVCS data has been collected and analyzed since Jefferson Laboratory's recent upgrades of the CEBAF accelerator and the CLAS12 detector in Hall-B. The upgrades allow this scattering experiment to be equipped with a continuous wave electron beam of 10.6 GeV and a large acceptance detector with efficient particle tracking and identification that covers a wide range of kinematics. A proton DVCS process is defined as an exclusive electroproduction of a photon on the target proton in the Bjorken limit. This process has access to proton's Compton form factors (CFFs) and thus to proton's generalized parton distributions (GPDs). This work will provide a valuable data set of GPDs and the three-dimensional imaging of proton in the valence quark region. [Preview Abstract] |
Monday, April 19, 2021 12:09PM - 12:21PM Live |
Q15.00006: Study of $a_0(980)$ and $a_2(1320)$ in $\gamma p \rightarrow \eta \pi^0 p$ at GlueX Lawrence Ng The GlueX experiment at Jefferson Lab is searching for hybrid mesons in the light meson spectrum using a 9 GeV photon beam on a liquid hydrogen target. The lightest exotic hybrid meson, the $\pi_1$, has been previously observed by other experiments as a broad enhancement peaking around 1.4 GeV in the $\eta \pi$ channel. Two strong resonances populate the observed $\eta \pi^0$ spectrum with well known parameters and decay channels, namely the $a_0(980)$ and $a_2(1320)$ mesons. Therefore, studying these mesons are important in extracting and understanding results related to the $\pi_1$. A study of the features in the mass range of the $a_0(980)$ and $a_2(1320)$ mesons is presented where the $\eta \pi^0$ final state decays into $4\gamma$. [Preview Abstract] |
Monday, April 19, 2021 12:21PM - 12:33PM Live |
Q15.00007: Compton Scattering Cross Section Measurement in Hall D at Jefferson Lab Andrew Smith The PrimEx-eta fixed-target experiment in Hall D at Jefferson Lab (E12-10-011\footnote{Spokespersons: A. Gasparian (contact), L. Gan, I. Larin, A. Somov}) will measure the $\eta\rightarrow\gamma\gamma$ decay width using the Primakoff method with a projected uncertainty of 3.2$\%$. In order to achieve this goal, Compton scattering from the atomic electrons in the target is being used as a reference process. Because of its similar kinematics to the $\eta\rightarrow\gamma\gamma$ decay, the total Compton scattering cross section can be measured using the same experimental configuration as the $\eta$ decay width measurement. Consequently, it can be used to verify the systematic uncertainties for the $\eta$ decay width measurement and monitor the luminosity, detection efficiency, and overall experimental stability. The first phase of the PrimEx-eta data was collected in 2019, corresponding to roughly one-third of the total proposed statistics. In this talk, I will discuss the preliminary results for the total Compton scattering cross section measured on a $^{9}$Be target. This will provide the first experimental data for Compton scattering in the energy range 6-11 GeV. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700