Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session T07: Hadron Spectroscopy and Exotics IRecordings Available
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Sponsoring Units: GHP Chair: Phiala Shanahan, Massachusetts Institute of Technology MI Room: Salon 4 |
Monday, April 11, 2022 3:45PM - 3:57PM |
T07.00001: Study of the Reaction γp → ηη'p Jason Barlow The motivation behind the GlueX experiment is to search for hybrid mesons. There is evidence for an exotic π1(1600) that decays to η'π. The π1(1600) should have an isoscalar partner, the η1, that can be observed in the η'η channel. The preliminary analysis presented here considers photoproduction of the final state η'η which decays to 4γπ+π-. The experiment uses a beam of linearly polarized photons with a peak near 9 GeV incident on a hydrogen target that produces these particles. General features of the data including mass spectra and data selection with a focus on removing backgrounds due to photon combinatorics will be shown. |
Monday, April 11, 2022 3:57PM - 4:09PM |
T07.00002: A study of the γp→pηππ 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 ρη intermediate states, all of which can be detected in the ηπ+π- final state. We will present results on the study of the reaction γp→pηπ+π- using 9-GeV linearly-polarized photons in GlueX data. In particular, we will discuss contributions to this final state from f1(1285) and ρη states, and we will compare these to the final state γp→pηπ0π0 , which does not couple to ρη. |
Monday, April 11, 2022 4:09PM - 4:21PM |
T07.00003: Resonances in the ωη System at GlueX Edmundo S Barriga The GlueX experiment has produced the world's largest data sample for peripheral photoproduction of mesons with a goal to unambiguously identify new and exotic mesons. In this talk, we will presents the current status of the search for possible intermediate resonances which decay to ωη, such as the known ω(1650), exotics with JPC=0--,2+-, and elusive ones with JPC=2--. The ω, in this reaction, is identified via the π+ π- π0 decay mode and the η and π0 are identified via the decay to 2γ. The data set was obtained at the Thomas Jefferson National Accelerator Facility utilizing the GlueX detector and a tagged linearly polarized photon beam that peaks between 8 - 9 GeV incident on a liquid hydrogen target. With over 100k events, an initial amplitude analysis of the data will be presented along with plans for future studies. |
Monday, April 11, 2022 4:21PM - 4:33PM |
T07.00004: Double-Regge Physics in ηπ0 at the GlueX Experiment Rebecca Barsotti The GlueX experiment is a photoproduction experiment based at Jefferson Lab in Newport News, Virginia. A major aim of GlueX is to look for hybrid mesons, which are a quark and an anti-quark bound by an excited gluonic field that contributes to the quantum numbers. The reaction γp → ηπp is of particular interest since ηπ is a potential decay mode of states with exotic quantum numbers JPC=1-+, which are forbidden in the constituent quark model. Finding such a resonance would be a clear sign of non-quark model physics. We have been working with members of the Joint Physics Analysis Center to develop and validate a model for the double-Regge interactions in this channel. These non-resonant processes generate asymmetries in the distributions of decay angles, which could be falsely attributed to the interference between exotic odd partial waves and even partial waves. We will present the current status of the development and validation of this double-Regge model and its importance. |
Monday, April 11, 2022 4:33PM - 4:45PM |
T07.00005: Triangle Singularity in the Production of $T_{cc}^+(3875)$ and a Soft Pion Eric Braaten, Kevin C Ingles, Li-Ping He, Jun Jiang The double-charm tetraquark meson $T_{cc}^+(3875)$ can be produced in high-energy proton-proton collisions by the creation of the charm mesons $D^{*+} D^0$ at short distances followed by their binding into $T_{cc}^+$. The $T_{cc}^+$ can also be produced by the creation of $D^{*+} D^{*+}$ at short distances followed by their rescattering into $T_{cc}^+ \pi^+$. nA charm-meson triangle singularity produces a narrow peak in the $T_{cc}^+ \pi^+$ invariant mass distribution 6.1~MeV above the threshold with a width of about 1~MeV. Beyond the peak, the differential cross section decreases with the invariant kinetic energy $E$ of $T_{cc}^+ \pi^+$ as $E^{-1/2}$. Estimates of the fraction of $T_{cc}^+$ events accompanied by a soft $\pi^+$ and the fraction of $T_{cc}^+$ events with $T_{cc}^+\, \pi^+$ in the narrow peak from the triangle singularity suggest that they may be observable in the existing LHCb data. |
Monday, April 11, 2022 4:45PM - 4:57PM |
T07.00006: From Lattice QCD Potentials to the Heavy-Quark Meson Spectrum: the Diabatic Approach Roberto Bruschini Understanding the hadron spectrum from the fundamental QCD Lagrangian is possibly the ultimate challenge in hadronic physics. As a matter of fact, the Born-Oppenheimer approximation provides a description of heavy-quark mesons firmly based on quenched (without sea quarks) Lattice QCD, where they are identified as bound states of a heavy quark-antiquark pair in effective potentials. However, the incorporation of unquenched (including sea quarks) Lattice potentials requires to take into account the effect of meson-meson components as well. This can be done in the diabatic framework, a formalism first introduced in molecular physics, where the dynamics is governed by a potential matrix treating the confining quark-antiquark interaction on equal grounds with the string breaking one, responsible for the coupling with meson-meson. Heavy-quark mesons are then identified as either bound states or scattering resonances containing both quark-antiquark and meson-meson components. A unified spectrum of quark-antiquark and molecular states comes out, which may accommodate many of the experimental charmoniumlike and bottomoniumlike mesons, including the notoriously "unconventional" ones like X(3872). |
Monday, April 11, 2022 4:57PM - 5:09PM |
T07.00007: The reaction NN → dπ studied by target rescattering at CLAS Kenneth H Hicks, Nicholas Compton, Nicholas Zachariou Using rescattering in exclusive meson photoproduction (γp → Nπ), the reaction cross sections for np → d π0 and pp → d π+ have been measured using the CLAS detector. The total cross sections, as a function of the center-of-mass energy, W, show a peak in the invariant mass of the deuteron-pion system at about 2145 MeV, which corresponds to the known resonance from the attractive N△ channel with isospin I=1. Results for the pp → d π+ reaction agree well with previous measurements, whereas the np → d π0 cross sections have not been previously determined. The ratio between these two total cross sections at the resonance peak is expected to follow predictions from isospin symmetry. Because both reactions are measured simultaneously, some systematic uncertainties cancel. Our preliminary results on these ratios indicate a deviation from predictions, which suggests that the reaction mechanism might be more complicated. |
Monday, April 11, 2022 5:09PM - 5:21PM |
T07.00008: Studying Tcc+ decays using effective field theory Reed Hodges, Sean P Fleming, Thomas C Mehen, Lin Dai The LHCb collaboration recently discovered a doubly charm tetraquark, Tcc+. We study its strong and electromagnetic decays in a molecular interpretation using a nonrelativistic effective field theory. This requires solving a coupled channel problem to account for both the D*0D+ and the D*+D0 channels. We also compute differential spectra as a function of the invariant mass of the final state meson pair. These results are in good agreement with the experimental analysis by LHCb. We discuss the effect of other shallow bound states of two pseudoscalar charm mesons on the decay of Tcc+, as well as next-leading-order contributions from pion exchange and final state rescattering. |
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