Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session M15: Mini-symposium: Hadron Spectra as Probes of QCDMini-Symposium
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Sponsoring Units: DNP Chair: Jeffery Martin, University of Winnipeg Room: Marquette VI - 2nd Floor |
Monday, April 17, 2023 10:45AM - 11:21AM |
M15.00001: QCD Probes at GlueX and Beyond Invited Speaker: Alexander Austregesilo The GlueX experiment at Jefferson Lab was specifically designed for precision studies of the light-meson spectrum. For this purpose, a photon beam with energies up to 12GeV is directed onto a liquid hydrogen target contained within a hermetic detector with near-complete neutral and charged particle coverage. Linear polarization of the photon beam with a maximum around 9GeV provides additional information about the production process. In 2018, the experiment completed its first phase, recording data with a total integrated luminosity above 400pb-1. We will highlight a selection of results from this world-leading data set with emphasis on the search for light hybrid mesons. In the mean time, the detector underwent significant upgrades and is currently recording data with an even higher luminosity. The future plans of the GlueX experiment to probe QCD with unprecedented precision will be summarized. |
Monday, April 17, 2023 11:21AM - 11:33AM |
M15.00002: Nuclear Physics with Short-Lived Beams John W Price Measurements of the beam flux and target thickness for short-lived beam particles are challenging in nuclear physics. Historically, bubble chamber experiments measured these quantities directly during datataking. While measurements of the kinematic variables were very precise, these experiments were statistics-limited, due to rate limitations of bubble chambers. Modern large-acceptance detectors can overcome this limitation, with data rates several orders of magnitude greater than bubble chambers. The final-state particles are either detected directly or reconstructed from their decay particles. The beam particle is not detected directly, but is inferred via a missing mass calculation. A recent study with the CLAS detector at JLab in Newport News, Virginia used a preliminary version of this technique to measure the cross section for Λp→Λp. The scattered Λ was inferred via its decay to π-p; the presence of two protons in the final state reduced greatly the amount of data to be analyzed. Although the incident momentum range was limited, the number of events in this measurement was far greater than any previous measurement for this process. This talk will present the motivations for the development of short-lived beams, the present status of this project with the CLAS Collaboration, and plans for future improvements to the technique. |
Monday, April 17, 2023 11:33AM - 11:45AM |
M15.00003: Photoproduction of Λ* resonances at CLAS Utsav Shrestha, Kyungseon Joo We present the study of the reaction γp → K+Λ* using the photoproduction data from the CLAS-g12 experiment performed in Hall B of Jefferson Laboratory. The photoproduction of the hyperon resonances Λ(1405)1/2- and Λ(1520)3/2- has been well studied, but little is known about photoproduction to the higher-mass resonances Λ(1670)1/2- and Λ(1690)3/2-. Both pairs of resonances are spin-orbit partners and are rated as 4-star (well-known) by the Particle Data Group. In the quark model, the Λ(1405) and Λ(1520) resonances are assigned to the SU(3) singlet, where the Λ(1670) and Λ(1690) are assigned to the octet. The decay of Λ* resonances, Λ(1520), Λ(1670), and Λ(1690), into two exclusive channels, Σ+π- and Σ-π+, is studied from the detected K+, π+, and π- particles. The Λ(1520) differential cross sections are in good agreement with the previous CLAS measurements and are extended to higher photon energies. We present cross sections for the first time using photoproduction to the higher mass resonances, Λ(1670) and Λ(1690). |
Monday, April 17, 2023 11:45AM - 11:57AM |
M15.00004: Photoproduction of Mesons Decaying into KSKS at GlueX Nathaniel D Hoffman The KSKS channel at GlueX allows for a high-precision study of light unflavored mesons for beam energies between 6.25 and 12 GeV. It provides a convenient filter for intermediate states with JPC = even++ , particularly the isospin-0 f-mesons, which are supernumerary in the quark model and may mix with the scalar glueball or contain other exotic states such as light tetraquarks or molecular mesons. We present a study of the exclusive reaction γp → KSKSp → 2π+2π-p with polarized photons in the GlueX detector to extract the photocouplings of the light scalar and tensor mesons. Using the sPlot method on the rest frame lifetime of both kaons, we are able to efficiently remove non-strange backgrounds in the channel. We perform a model-independent partial-wave analysis to separate S- and D-wave contributions produced in both natural and unnatural parity exchange processes. We also fit a K-matrix amplitude to the data to isolate the contributions from individual mesons.
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Monday, April 17, 2023 11:57AM - 12:09PM |
M15.00005: Proton-anti-Proton Photoproduction at CLAS Diego F Padilla Monroy, Lei Guo, William B Phelps The photoproduction of a state “X” which decays into a proton-anti-proton pair has been studied previously, partially because its production mechanism is to this day largely unknown. This X state is studied generally by looking for narrow resonances in the invariant mass distribution of the proton-anti-proton pair, but results have shown little evidence for it, in part because of the limited statistics that previous analysis had. |
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