Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session J11: Electromagnetic Production of Hadronic Resonances |
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Sponsoring Units: DNP Chair: Reinhard Schumacher, Carnegie Mellon University Room: A220-221 |
Sunday, April 15, 2018 1:30PM - 1:42PM |
J11.00001: Antibaryon Photoproduction using CLAS at Jefferson Lab William Phelps There is little known about the baryon-antibaryon photoproduction mechanism. Three reactions, $\gamma p\rightarrow pp\bar{p}$, $\gamma p\rightarrow pp\bar{n}\pi^{-} $, and $\gamma p\rightarrow pn\bar{p}\pi^{+}$ have been investigated for the photon energy range of 3.95-5.45 GeV. The data were from the g12 experiment taken with the CLAS detector using a liquid hydrogen target in Hall B at Thomas Jefferson National Accelerator Facility. This experiment had high statistics, with an integrated luminosity of 68 pb$^{-1}$. General features of the data and preliminary cross sections for the $p\bar{p}$ system will be discussed. [Preview Abstract] |
Sunday, April 15, 2018 1:42PM - 1:54PM |
J11.00002: Photoproduction of $\omega$ mesons off bounded proton with the CLAS detector at Jlab Olga Cortes, Philip Cole QCD-inspired models have been developed to explain the hadronic spectrum in terms of the underlying QCD degrees of freedom. And while there have been many successes in delineating the significant features of the overall spectrum, many of the resonant states that have been predicted by these models have not yet been found experimentally. Because of the high number of excited states of the nucleon, all of which have large widths causing the resonances to overlap, we need to study the kinematic evolution of the polarization observables for obtaining a ``complete measurement'' towards extracting the pertinent helicity amplitudes. In our work, we are focusing on the photoproduction of $\omega$ mesons off the bound proton which provides information about $N^*$ resonances as $\omega$ is an isospin filter. In this talk, we present preliminary results for the quasi-free $\vec{\gamma}d\rightarrow \omega p(n)$ photon beam asymmetry polarization observable. The data were taken with the CLAS detector in Hall B at the Thomas Jefferson National Accelerator Laboratory (Jlab). The experiment provided a high-quality beam of linearly-polarized photons in the energy range from $1.1$ to $2.3$~GeV. [Preview Abstract] |
Sunday, April 15, 2018 1:54PM - 2:06PM |
J11.00003: Differential Cross Section for $\gamma d \rightarrow \omega d$ using CLAS at Jefferson Lab Taya Chetry, Kenneth Hicks Coherent $\omega$-meson photoproduction from the deuteron has been studied using CLAS at Jefferson Lab, Virginia, as a function of the photon energy and the 4-momentum transfer. Tagged photons with beam energies between 0.8 and 3.6 GeV were produced using the bremsstrahlung process incident on a deuterium target. The final state particles detected are an energetic deuteron and a pair of charged pions. A three-pion decay mode for the vector meson $\omega$ is used to measure differential cross section for $\gamma d \rightarrow \omega d$. The cross sections are measured in the energy range $1.4 < E_{\gamma} < 3.4$ GeV. A model based on rescattering is consistent with the data at intermediate and high momentum transfer, $|t|$. For $2.8 < E_{\gamma} < 3.4$ GeV, the total cross-section of $\omega-N$ scattering is 30-40 mb in the framework of Vector Meson Dominance. This data set dramatically improves the world data on the $\gamma d \rightarrow \omega d$ reaction and opens up the possibility for further study of the $\omega N$ interaction. [Preview Abstract] |
Sunday, April 15, 2018 2:06PM - 2:18PM |
J11.00004: Measuring the Beam Asymmetry for a0(980) Photoproduction on the Proton at GlueX Stuart Fegan The 12 GeV upgrade at Jefferson Lab has opened up new opportunities in intermediate-energy nuclear science, not least in photoproduction, via the GlueX facility. It has been postulated that at JLab upgrade energies, quark systems beyond the three quark and quark-antiquark systems of baryons and mesons, such as hybrid mesons, tetraquarks and glueballs, should exist, and studies of these systems could shed new light on how quarks combine under the Strong force, particularly the role played by gluons. Meticulous study of the spectrum of hadronic states is required to further understand the strong force in the non-perturbative energy regime, and the light scalar meson sector is an area that remains poorly understood in this respect. GlueX has already taken new data encompassing final states at energies where photoproduction of the a0(980) and f0(980) mesons can inform our understanding of meson photoproduction dynamics, and performing detailed measurements of experimental observables for these states is considered a priority of the ongoing research program. The work presented focuses on efforts to measure the beam asymmetry of the a0(980) meson from the reaction $\gamma p \rightarrow p \pi \eta$ using linearly polarized photons of $E_{\gamma} = 9 GeV$. [Preview Abstract] |
Sunday, April 15, 2018 2:18PM - 2:30PM |
J11.00005: Measurement of Polarization Observables for the $\Lambda$ in the reaction $\gamma p \rightarrow K^{+} \Lambda$. Shankar Adhikari, Brian Raue, Lei Guo Spin observables are important to understand the production mechanisms of hyperons, as well as the contribution of intermediate baryon resonances. $\Lambda$ polarizations observables have been studied extensively in the recent decades using the reaction $\gamma + p \rightarrow K^{+} + \Lambda$. This talk presents the measurement of transferred polarization coefficients $C_{X}$ and $C_{Z}$, and the induced polarization $P$, using a new set of high statistics data, obtained using the CEBAF Large Acceptance Spectrometer(CLAS) detector at Jefferson Lab. The photon beam energy range is 1.117 to 5.45 GeV. These results ($C_{X}$, $C_{Z}$ and $P$) are extracted simultaneously using the Maximum Likelihood Method. The measurements for $C_{X}$ and $C_{Z}$ have nearly an order of magnitude increase in events compared to previously published results and also extend the kinematic range for $W > 2.46$ GeV, important for both, the search for high-mass nucleon states as well as to provide information about non-resonant contributions. [Preview Abstract] |
Sunday, April 15, 2018 2:30PM - 2:42PM |
J11.00006: A study of the $\gamma p \rightarrow K^+ \Lambda^*$ reaction Utsav Shrestha, Taya Chetry, Kenneth Hicks Much is known about the photoproduction of the hyperon resonances $\Lambda(1405)1/2^-$ and $\Lambda(1520)3/2^-$, but little is known about photoproduction to the higher-mass resonances $\Lambda(1670)1/2^-$ and $\Lambda(1690)3/2^-$. 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 $\Lambda(1405)$ and $\Lambda(1520)$ resonances are assigned to the SU(3) singlet, where the $\Lambda(1670)$ and $\Lambda(1690)$ are assigned to the octet. In this presentation, we will present a first look at photoproduction data for these hyperon octet resonances using data from the CLAS detector at Jefferson Lab. Future plans for a partial wave analysis, which will be necessary to resolve the individual cross sections for these two resonances, will be outlined. [Preview Abstract] |
Sunday, April 15, 2018 2:42PM - 2:54PM |
J11.00007: A study of the $\gamma d \rightarrow \pi^+\pi^-d$ reaction Kenneth Hicks, Taya Chetry, Reinhard Schumacher This study investigates a recently-observed $N\Delta$ ($d^*$) resonance decaying to $\pi d$ final state using CLAS at Jefferson Lab, Virginia. Tagged photons with beam energies between 0.8 and 3.6 GeV were produced using the bremsstrahlung process incident on a liquid deuterium target. The final state particles detected were an energetic deuteron and a two oppositely charged pions. The $d^*$ resonance has been seen in other preliminary analyses at CLAS. Partial-wave analysis of pion-deuteron scattering has also shown a resonance at a mass of about 2145 MeV. A preliminary differential cross section measurement of this resonance will be presented. [Preview Abstract] |
Sunday, April 15, 2018 2:54PM - 3:06PM |
J11.00008: The prospect for studying $n\pi^{+}\pi^{0}$ electroproduction off protons with CLAS12 Gleb Fedotov, Kenneth Hicks, Iuliia Skorodumina Investigation of double-pion electroproduction channel is a very efficient tool for exploration of nucleon structure that includes the study of nucleon resonances. The experiments conducted with the CLAS detector have already provided a lot of data on the cross sections of the reaction $\gamma_{v} p \rightarrow p'\pi^{+}\pi^{-}$. Their interpretation within the phenomenological model has delivered valuable information on nucleon resonances electrocouplings. Another promising channel, for the $n\pi^{+}\pi^{0}$ final state, has not yet been investigated using the CLAS detector due to the limited angular coverage of $\pi^{0}$ detection. The cross section of this so far unexplored channel benefits from larger relative resonant contribution comparing to the reaction with the $p\pi^{+}\pi^{-}$ final state. New opportunities for studying the $n\pi^{+}\pi^{0}$ final state are possible with the CLAS12 detector, which has significantly larger angular coverage for $\pi^{0}$ detection than CLAS. The study of a new channel requires an adaptation of the experimental analysis tools and the phenomenological reaction model which were previously established for $\gamma_{v} p \rightarrow p'\pi^{+}\pi^{-}$ channel. The status of this activity will be presented in the talk. [Preview Abstract] |
Sunday, April 15, 2018 3:06PM - 3:18PM |
J11.00009: Polarization Observables from Strangeness Photoproduction on a Frozen Spin Target at Jefferson Lab Igor Strakovsky, Stuart Fegan The FROST experiment at Jefferson Lab used the CLAS detector in Hall B with the intention of performing a complete and over-determined measurement of the polarization observables associated with strangeness photoproduction, in combination with data from previous JLab experiments as part of the N* program. This was achieved by utilizing the FROST polarized target in conjunction with polarized photon beams, allowing direct measurement of beam-target double polarization observables. Sufficient observables have now been measured to enable the associated reaction amplitudes to be determined, facilitating a near model-independent PWA, remaining ambiguities will only be resolved by measuring observables spanning combinations of beam, target, and recoil polarization. With current data on the baryon spectrum dominated by studies of $\pi $N reactions, investigations on strangeness photoproduction reactions, such as $\gamma $p$\to $K$+\Lambda $, may observe previously unseen resonances, due to the different coupling strengths of these states to different reaction channels.The G asymmetry is one of the beam-target double polarization observables, associated with a longitudinally polarized target and a linearly polarized photon beam, and its measurement for the strangeness reaction $\gamma $p$\to $K$+\Lambda $ in the energy range E$\gamma \quad =$ 1.1 -- 2.1 GeV is the focus of the work presented. [Preview Abstract] |
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