Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session PG: Hadronic Spectroscopy I |
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Chair: Simon Taylor, JLAB Room: Copley & Kenmore |
Thursday, October 14, 2021 9:30AM - 10:06AM |
PG.00001: Recent Progress in Hadron Spectroscopy and the Path to the EIC Invited Speaker: Sean Dobbs The past two decades have seen a renaisance in hadron spectroscopy, with the identification of dozens of new particles - from expected states, to those beyond the quark model, with more than three quarks or gluonic degrees of freedom contributing to their properties. These discoveries have been driven by new, high-quality data generated by high-luminosity accelerators from a few GeV to multi-TeV in energy, as well as improvements in our theoretical understanding of QCD and these reactions. Now, the challenge is to determine the details of the interactions that lead to the hadrons that we observe. In this talk, I will review some of the recent experimental progress in hadron spectroscopy, particularly coming from experiments at Jefferson Lab, and discuss the prospects from upcoming experiments, particularly those planned for the Electron-Ion Collider (EIC). |
Thursday, October 14, 2021 10:06AM - 10:18AM |
PG.00002: Meson and Baryon Photoproduction using γp→KSKSp at GlueX. Nathaniel D Hoffman, Reinhard A Schumacher The photoproduction of mesons decaying into pairs of neutral kaons is being studied with GlueX at Jefferson Lab via the reaction γp→KS KSp. The combination of two neutral identical kaons is only allowed to have even total angular momentum, constraining the parent particles to the scalar and tensor states such as the a0’s, a2’s, f0’s, and f2’s. Data sets with several tens of thousands of events created in the photon energy range from 6.25 to 11.6 GeV have been obtained using the GlueX Phase 1 data set, allowing for the first significant study of this reaction. Preliminary results show interference patterns characteristic of several known mesonic intermediate states in the Gottfried-Jackson and helicity systems. Additionally, the data also show evidence of reactions in which a K0 is produced in combination with baryons from the family of Σ+ hyperons, which subsequently decay to K̅0 and a proton. Our work describes several mesonic and baryonic states which are obtained after kinematic fitting and a set of selection criteria used to reduce backgrounds from non-strange production. We will evaluate the quantum numbers of the mesonic states to determine if any of them could have hybrid/exotic qualities (forbidden quantum number combinations due to gluonic excitation) and measure cross-sections to ascertain the possibility of glueball mixing in any of the states. |
Thursday, October 14, 2021 10:18AM - 10:30AM |
PG.00003: η Meson Photoproduction with the GlueX Experiment Jonathan Zarling Studies of the production and decay of the η meson in photoproduction offer a wide range of physics opportunities: these include constraining models of hadronic photoproduction, dark sector boson searches, precision tests of QCD effective theories, and tests of fundamental symmetries. GlueX, a high-intensity photoproduction experiment located at Hall D of Jefferson Lab, offers a large and clean sample of η mesons off the proton. We present results for cross sections of η photoproduction at Eγ = 6-11 GeV and find consistent results using the decay modes η→γγ, π+π-π0, and π0π0π0. When studied as a function of Mandelstam |t|, these cross sections can constrain models describing η production in terms of t-channel Reggeon exchange. Such measurements inform future searches for exotic hybrid mesons and serve as a benchmark for the Jefferson Lab Eta Factory, a future upgrade to the existing GlueX facility. |
Thursday, October 14, 2021 10:30AM - 10:42AM |
PG.00004: f1 Meson Production with the GlueX Experiment Tyler Viducic, Moskov Amaryan We present a study of high-energy photoproduction of the f1(1285) and f1(1420) mesons at GlueX in the reaction γp→ KsK± π±p. Measurements of the f1(1285) meson have been performed recently using the 6GeV electron beam at CLAS. The 12GeV upgrade to CEBAF has allowed us to extend cross-section measurements of f1(1285) to higher -t and s Mandelstam variables and expand on the prior measurements. We will present the status of these cross-section measurements and comparison to theoretical predictions for photoproduction of the f1 mesons. |
Thursday, October 14, 2021 10:42AM - 10:54AM |
PG.00005: Photoproduction and lineshape of Λ(1405) → Σ0π0 at GlueX Nilanga I Wickramaarachchi, Grzegorz Kalicy The invariant mass spectrum or the "line shape" of many resonances in hyperon spectroscopy can be modelled by a Breit-Wigner distribution. However, previous measurements of the line shape of Λ(1405) hyperon state are significantly distorted from a Breit-Wigner form and therefore it has a lot of attention from the hyperon physics community. A study of the Λ(1405) line shape would provide more information on how the Σπ and $N\bar{K}$ channels contribute to its production. The Λ(1405) mainly decays to Σ+π-, Σ-π+ and Σ0π0 modes with each having ~33% branching fraction. Studying the Σ0π0 decay mode provides the advantage that the Λ(1405) mass region is not contaminated by Σ0(1385) production, compared to the other two charged decay modes. The GlueX experiment at Jefferson Lab provides an excellent opportunity to study the Λ(1405) → Σ0π0 decay mode with a photon beam in the energy range 6.5–11.6 GeV incident on a liquid hydrogen target and a large acceptance electromagnetic calorimeter. In this talk, we focus on the preliminary results from analyzing the reaction γp → K+Λ(1405) using the data collected during the first phase of the GlueX experiment. |
Thursday, October 14, 2021 10:54AM - 11:06AM |
PG.00006: A study of the γη→pηπ+π- reaction at GlueX Alison J LaDuke The search for exotic hybrid mesons is one of the main goals of the GlueX experiment at Jefferson Lab. Possible decays of the η1 and b2 exotic hybrid mesons could occur through the a2(1320)π, f2(1270)η, and ηρ intermediate states, where all of these can be detected in the ηπ+π- final state. We will present results on the study of the reaction γη→pηπ+π- using 9 GeV linearly polarized photons in GlueX. We will also discuss other contributions to this final state. |
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