Bulletin of the American Physical Society
2016 Fall Meeting of the APS Division of Nuclear Physics
Volume 61, Number 13
Thursday–Sunday, October 13–16, 2016; Vancouver, BC, Canada
Session DC: Mini-symposium on Light Meson Spectroscopy: First Results from GlueX IIMini-Symposium
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Chair: Matt Shepherd, Indiana University Room: Junior Ballroom B |
Friday, October 14, 2016 10:30AM - 10:42AM |
DC.00001: A survey of multi-photon final states using the GlueX detector Simon Taylor The primary focus of the GlueX experiment is the search for evidence for hybrid mesons. Models suggest that these mesons are likely to decay to final states containing at least one $\pi^0$ or $\eta$ and are thereby likely to produce multiple photons. In addition, the conditionally-approved Jefferson Lab Eta Factory (JEF) experiment plans to explore the rare $\eta\rightarrow\pi^0\gamma\gamma$ decay, which most of the time produces four photons in the final state. The final-state photons are detected in the Forward and Barrel Calorimeters of the GlueX detector. A overview will be presented of the excellent data quality from the Spring 2016 run for the exclusive reactions $\gamma p \rightarrow p + N\gamma$ with N=2-6. [Preview Abstract] |
Friday, October 14, 2016 10:42AM - 10:54AM |
DC.00002: Exclusive $\omega$(782) photoproduction at GlueX Michael Staib The GlueX experiment at Jefferson Lab aims to explore the gluonic degrees of freedom in QCD by studying light meson photoproduction off of a hydrogen target using a tagged, linearly-polarized photon beam. We will present measurements of exclusive $\omega$(782) photoproduction at a photon beam energy of 9 GeV in both the hadronic and radiative decay channels. Preliminary results for spin observables describing the reaction are presented and compared with earlier measurements. [Preview Abstract] |
Friday, October 14, 2016 10:54AM - 11:06AM |
DC.00003: $\eta’-\pi$ production and search for exotic mesons at COMPASS and JLab12 Vladyslav Pauk, Adam Szczepaniak, Vincent Mathieu In the exclusive production of $\eta\pi$ and $\eta’\pi$ pairs with a 191 GeV/c pion beam at COMPASS resonance-like enhancement in the P-wave was observed. Such a resonance would carry exotic quantum numbers therefore, cannot be associated with the conventional quark-antiquark states. To examine the observed behavior we examine the properties of reaction amplitude using analyticity, unitarity and high-energy constraints. Following Regge prediction, for sufficiently large incident energy the five-particle amplitude for the reaction $p\pi\to p\pi\eta$ is proportional to the reggeon-particle scattering amplitude $R\pi\to\eta\pi$. In the resonance region, the reggeon-particle amplitudes are parametrized within N/D formalism supplemented by elastic unitarity constraints. At higher values of $\eta\pi$ invariant masse, the amplitude is reggeized similarly to normal four-particle amplitudes. Matching between the two parametrizations in the transition region is implemented via finite energy sum rules. To constrain the parameters of reggeon and decay vertices we employ the Regge factorization as well as SU(3) constraints and use data from other high-energy experiments. Finally, we consider the extension of the developed formalism for the photoproduction of $\eta\pi$ meson systems at GlueX. [Preview Abstract] |
Friday, October 14, 2016 11:06AM - 11:18AM |
DC.00004: Study of the $\ensuremath{\eta}(\ensuremath{'})\ensuremath{\rightarrow}e^{+}e^{-}\ensuremath{\gamma}$ decay at GlueX and Transition Form Factors Cristiano Fanelli, Michael Williams Radiative decays of mesons are powerful probes of the hadron structure. The GlueX experiment will produce and record huge samples of light mesons. In this talk, we discuss the potential for GlueX to study radiative decays of light mesons. For example, the possibility of measuring the transition form factor of the $\ensuremath{\eta}$ and $\ensuremath{\eta}\ensuremath{^{'}}$ mesons will be explored. The low Q$^{2}$ slope of the TFF provides a unique method to measure the pseudo-scalar meson radius, whose physical interpretation has still not comprehensively explored. [Preview Abstract] |
Friday, October 14, 2016 11:18AM - 11:30AM |
DC.00005: Partial wave analysis of $3\pi$ with pion and photon beams Andrew Jackura, Mikhail Mikhasenko, Adam Szczepaniak, Bernhard Ketzer We present some results on the analysis of $3\pi$ resonances from peripheral scattering of pions off of nuclear targets. The analysis is motivated by the recent release of the largest data set on diffractively produced three pions by the COMPASS collaboration. The model emphasizes the $3\pi$ production process and their final state interactions which satisfy $S$-matrix principles. We apply our model to fit partial wave intensities and relative phases from COMPASS in the $J^{PC}=2^{-+}$ sector and search for resonances. We then discuss the extension of our formalism to photon beams to be used in the GlueX experiment. [Preview Abstract] |
Friday, October 14, 2016 11:30AM - 11:42AM |
DC.00006: Leptophobic Boson Searches John Hardin, Cristiano Fanelli, Michael Williams The GlueX data set has the potential to improve the sensitivity to leptophobic bosons, including the so called B boson which couples to baryon number, by a factor of O(100) between 450 and 900MeV. We present the expected reach of the limits on the coupling of $\gamma p->pB$ from the data already taken in Spring 2016 and of the full data set. These results will also set limits on other dark sector models and motivate ep-$>$pB searches at CLAS. [Preview Abstract] |
Friday, October 14, 2016 11:42AM - 11:54AM |
DC.00007: 3pi resonance poles from COMPASS data Mikhail Mikhasenko, Andrew Jackura, Adam Szczepaniak, Bernhard Ketzer High-energy peripheral reactions provide an excellent opportunity to study the excitation spectrum of hadrons. The COMPASS experiment at CERN has measured the diffractive scattering of pions to the 3-pion final state with unprecedented statistical precision. Partial wave analysis technique has been employed to obtain an expansion of the reaction cross section in terms of partial waves with quantum numbers $J^{PC}\,M^\varepsilon$, which is differential in the $3\pi$ invariant mass and the squared transverse momentum. The aim of our analysis is the interpretation of the mass-dependence of the spin-density matrix in terms of short- and long-range interactions using analyticity and unitarity constraints. Using the K-matrix approach, we build the amplitude for scattering of a quasi-two-body final state ($\pi\pi$-subchannnel resonance + pion), and include a unitarization procedure to incorporate non-resonant long-range production processes via pion exchange. The talk is focused on a demonstration of the approach on the $2^{-+}$ sector of COMPASS data. A global fit over $3\pi$ invariant mass up to $2.2\,$GeV and $0.1\,$GeV$^2 < t' < 1\,$GeV$^2$ is performed. We explore a presence and positions of poles and discuss the long standing puzzle about $\pi_2(1670)-\pi_2(1880)$ interplay. [Preview Abstract] |
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