Wed·Sep 25, 2019Wednesday·September 25, 2019

1. 01*

   Search for eta mesic 3He with the WASA-at-COSY facility in the pd-> 3He 2gamma and pd-> 3He 6gamma reactions

   P. Adlarson · W. Augustyniak · W. Bardan · M. Bashkanov · S. D. Bass · M. Berłowski · A. Bondar · M. Büscher · H. Calén · I. Ciepał · H. Clement · E. Czerwiński and 72 other authors

   We report on the experimental search for the bound state of an $\eta$ meson and ${}^3\text{mbox}He$ nucleus performed using the WASA-at-COSY detector setup. In order to search for the $\eta$-mesic nucleus decay, the $pd\to$ ${}^3\text{mbox}He2\gamma$ and $pd\to$ ${}^3\text{mbox}He6\gamma$ channels have been analysed. These reactions manifest the direct decay of $\eta$ meson bound in ${}^3\text{mbox}He$ nucleus. This non-mesonic decay channel has been considered for the first time. When taking into account only statistical errors, the obtained excitation functions reveal a slight indication for a possible bound state signal corresponding to an ${}^3$He-$\eta$ nucleus width $\Gamma$ above 20 MeV and binding energy $B_s$ between 0 and 15 MeV. However, the determined cross sections are consistent with zero in the range of the systematic uncertainty. Therefore, as final result we estimate only the upper limit for the cross section of the $\eta$-mesic ${}^3\text{mbox}He$ nucleus formation followed by the $\eta$ meson decay which varies between $2$ nb and $15$ nb depending on possible bound state parameters.

   nucl-exPLB(2020)·12 citations
2. 02*

   Photoproduction of the $\Lambda$(1520) hyperon with a 9 GeV photon beam at GlueX

   Peter Pauli (for the GlueX collaboration)🇬🇧

   The GlueX experiment is located at the Thomas Jefferson National Accelerator Facility (JLab) in Newport News, VA, USA. It features a hermetic 4$\pi$ detector with excellent tracking and calorimetry capabilities. Its 9 GeV linearly polarized photon beam is produced from the 12 GeV electron beam, delivered by JLab's Continuous Electron Beam Accelerator Facility (CEBAF), via bremsstrahlung on a thin diamond and is incident on a LH2 target. GlueX recently finished its first data taking period and published first results. The main goal of GlueX is to measure gluonic excitations of mesons. These so-called hybrid or exotic mesons are predicted by Quantum Chromodynamics (QCD) but haven't been experimentally confirmed yet. They can have quantum numbers not accessible by ordinary quark-antiquark pairs which helps in identifying them using partial wave analysis techniques. The search for exotic mesons requires a very good understanding of photoproduction processes in a wide range of final states, one of them being $p{K}^{+}{K}^{-}$ which contains many meson and baryon reactions. The $\Lambda$(1520) is a prominent hyperon resonance in this final state and is the subject of this presentation. This talk will give an introduction to the GlueX experiment and show preliminary results for the photoproduction of the $\Lambda$(1520) hyperon. The measurement of important observables like the photon beam asymmetry and spin-density matrix elements will be discussed and an outlook to possible measurements of further hyperon states in the $p{K}^{+}{K}^{-}$ final state will be given.

   nucl-exhep-ex2 citations
3. 03*

   Nucleon strange electromagnetic form factors

   C. Alexandrou (Univ. of Cyprus & The Cyprus Inst.)🇨🇾 · S. Bacchio (The Cyprus Inst.)🇨🇾 · M. Constantinou (Temple Univ.)🇺🇸 · J. Finkenrath (The Cyprus Inst.)🇨🇾 · K. Hadjiyiannakou (The Cyprus Inst.)🇨🇾 · K. Jansen (DESY-Zeuthen)🇩🇪 · G. Koutsou (The Cyprus Inst.)🇨🇾

   The role of the strange quarks on the low-energy interactions of the proton can be probed through the strange electromagnetic form factors. Knowledge of these form factors provides essential input for parity-violating processes and contributes to the understanding of the sea quark dynamics. We determine the strange electromagnetic form factors of the nucleon within the lattice formulation of Quantum Chromodynamics using simulations that include light, strange and charm quarks in the sea all tuned to their physical mass values. We employ state-of-the-art techniques to accurately extract the form factors for values of the momentum transfer square up to 0.8~GeV${}^2$. We find that both the electric and magnetic form factors are statistically non-zero. We obtain for the strange magnetic moment ${\mu }^s=-0.017(4)$, the strange magnetic radius $⟨r_M^2{⟩}^s=-0.015(9)$~fm${}^2$, and the strange charge radius $⟨r_E^2{⟩}^s=-0.0048(6)$~fm${}^2$.

   ↳ hep-lathep-phnucl-exnucl-thPRD(2020)·40 citations
4. 04*

   Suppression of quarkonia in PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

   Vineet Kumar🇮🇳 · Prashant Shukla🇮🇳 · Abhijit Bhattacharyya🇮🇳

   We study different processes responsible for the modification of quarkonia yields in the medium produced in PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. The quarkonia and heavy flavour cross sections are estimated using the measurements in pp collisions at LHC energies and shadowing corrections are obtained using the EPS09 parametrizations. A kinetic model is used which incorporates quarkonia suppression inside the Quark Gluon Plasma (QGP), suppression due to hadronic comovers, and regeneration from recombination of heavy quark pairs. The quarkonia dissociation cross section due to gluon collisions, including both color-electric dipole and color-magnetic dipole transitions, has been employed. The regeneration rate is obtained using the principle of detailed balance. The effect of these processes on the nuclear modification factors for both $\text{Jpsi}$ and ${\rm Y}$ in different ranges of transverse momentum $\text{pT}$ and rapidity has been studied for PbPb collisions at $\text{sNN}=$ 5.02 TeV. The calculations are compared with the available results from LHC experiments. Both the suppression and regeneration due to a QGP are effective in the low and intermediate $\text{pT}$ range. The large observed suppression of $\text{Jpsi}$ at $\text{pT}>$ 10 GeV/$c$ is larger than the suppression expected due to gluon dissociation.

   ↳ hep-phnucl-exnucl-thJ.Phys.G(2020)·5 citations
5. 05*

   Resonance Electroproduction and the Origin of Mass

   Craig D. Roberts🇨🇳

   One of the greatest challenges within the Standard Model is to discover the source of visible mass. Indeed, this is the focus of a "Millennium Problem", posed by the Clay Mathematics Institute. The answer is hidden within quantum chromodynamics (QCD); and it is probable that revealing the origin of mass will also explain the nature of confinement. In connection with these issues, this perspective describes insights that have recently been drawn using contemporary methods for solving the continuum bound-state problem in relativistic quantum field theory and how they have been informed and enabled by modern experiments on nucleon-resonance electroproduction.

   ↳ nucl-thhep-lathep-phnucl-exEPJ Web Conf.(2020)·8 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.