Fri·Aug 16, 2019Friday·August 16, 2019

1. 01*

   Beam Asymmetry $\mathbf{\Sigma }$ for the Photoproduction of $\eta$ and ${\eta }^{\prime }$ Mesons at ${\mathbf{E}}_{\gamma }=8.8$GeV

   The GlueX Collaboration: S. Adhikari🇺🇸 · A. Ali🇩🇪 · M. Amaryan🇺🇸 · A. Austregesilo🇺🇸 · F. Barbosa🇺🇸 · J. Barlow🇺🇸 · A. Barnes🇺🇸 · E. Barriga🇺🇸 · R. Barsotti🇺🇸 · T. D. Beattie🇨🇦 · V. V. Berdnikov🇷🇺 · T. Black🇺🇸 and 121 other authors

   We report on the measurement of the beam asymmetry $\Sigma$ for the reactions $\vec{\gamma }p\to p\eta$ and $\vec{\gamma }p\to p{\eta }^{\prime }$ from the GlueX experiment, using an 8.2--8.8 GeV linearly polarized tagged photon beam incident on a liquid hydrogen target in Hall D at Jefferson Lab. These measurements are made as a function of momentum transfer $-t$, with significantly higher statistical precision than our earlier $\eta$ measurements, and are the first measurements of ${\eta }^{\prime }$ in this energy range. We compare the results to theoretical predictions based on $t$--channel quasi-particle exchange. We also compare the ratio of ${\Sigma }_{\eta }$ to ${\Sigma }_{{\eta }^{\prime }}$ to these models, as this ratio is predicted to be sensitive to the amount of $s\bar{s}$ exchange in the production. We find that photoproduction of both $\eta$ and ${\eta }^{\prime }$ is dominated by natural parity exchange with little dependence on $-t$.

   nucl-exhep-exPRC(2019)·33 citations
2. 02*

   Toward an accurate strongly-coupled many-body theory within the equation of motion framework

   Elena Litvinova🇺🇸 · Peter Schuck🇫🇷

   Non-perturbative aspects of the quantum many-body problem are revisited, discussed and advanced in the equation of motion framework. We compare the approach to the two-fermion response function truncated on the two-body level by the cluster expansion of the dynamical interaction kernel to the approach known as time blocking approximation. Such a comparison leads to an extended many-body theory with non-perturbative treatment of high-order configurations. The present implementation of the advanced theory introduces a new class of solutions for the response functions, which include explicitly beyond-mean-field correlations between up to six fermions. The novel approach, which includes configurations with two quasiparticles coupled to two phonons (2q$\otimes$2phonon), is discussed in detail for the particle-hole nuclear response and applied to medium-mass nuclei. The proposed developments are implemented numerically on the basis of the relativistic effective meson-nucleon Lagrangian and compared to the models confined by two-fermion and four-fermion configurations, which are considered as state-of-the-art for the response theory in nuclear structure calculations. The results obtained for the dipole response of ${}^{42,48}$Ca and ${}^{68}$Ni nuclei in comparison to available experimental data show that the higher configurations are necessary for a successful description of both gross and fine details of the spectra in both high-energy and low-energy sectors.

   ↳ nucl-thnucl-exPRC(2019)·48 citations
3. 03*

   Probing $\Omega \Omega$ and $p\Omega$ dibaryons with femtoscopic correlations in relativistic heavy-ion collisions

   Kenji Morita🇯🇵 · Shinya Gongyo🇯🇵 · Tetsuo Hatsuda🇯🇵 · Tetsuo Hyodo🇯🇵 · Yuki Kamiya🇨🇳 · Akira Ohnishi🇯🇵

   The momentum correlation functions of baryon pairs, which reflects the baryon-baryon interaction at low energies, are investigated for multi-strangeness pairs ($\Omega \Omega$ and $N\Omega$) produced in relativistic heavy-ion collisions. We calculate the correlation functions based on an expanding source model constrained by single-particle distributions. The interaction potentials are taken from those obtained from recent lattice QCD calculations at nearly physical quark masses. Experimental measurements of these correlation functions for different system sizes will help to disentangle the strong interaction between baryons and to unravel the possible existence of strange dibaryons.

   ↳ nucl-thhep-lathep-phnucl-exPRC(2020)·80 citations
4. 04*

   Ab Initio Treatment of Collective Correlations and the Neutrinoless Double Beta Decay of ${}^{48}$Ca

   J. M. Yao🇺🇸 · B. Bally🇺🇸 · J. Engel🇺🇸 · R. Wirth🇺🇸 · T. R. Rodríguez🇪🇸 · H. Hergert🇺🇸

   Working with Hamiltonians from chiral effective field theory, we develop a novel framework for describing arbitrary deformed medium-mass nuclei by combining the in-medium similarity renormalization group with the generator coordinate method. The approach leverages the ability of the first method to capture dynamic correlations and the second to include collective correlations without violating symmetries. We use our scheme to compute the matrix element that governs the neutrinoless double beta decay of ${}^{48}$Ca to ${}^{48}$Ti, and find it to have the value $0.61$, near or below the predictions of most phenomenological methods. The result opens the door to ab initio calculations of the matrix elements for the decay of heavier nuclei such as ${}^{76}$Ge, ${}^{130}$Te, and ${}^{136}$Xe.

   ↳ nucl-thhep-phnucl-exPRL(2020)·195 citations
5. 05*

   Muon Identification Using Deep Neural Networks with the Muon Telescope Detector at STAR

   J. D. Brandenburg · Frank Geurts

   The installation of the muon telescope detector opened new possibilities for studying dimuon production at STAR. However, backgrounds from hadron punch-through and weak decays of pions and kaons make the identification of primary muons challenging. In this paper we present a study of shallow and deep neural networks trained as classifiers for the purpose of muon identification using information from the muon telescope detector at STAR. The performance of shallow neural networks is presented as a function of the number of neurons in their hidden layer. A hyperparameter optimization for determining the optimal deep neural network classifier architecture is presented. The optimized deep neural network is compared with shallow neural networks, boosted decision trees, likelihood ratios, and traditional cut-based PID techniques. The superiority of the deep neural network based muon identification technique is demonstrated and compared with traditional PID through the measurement of the $\varphi$ meson and the $\psi (2S)$ in p+p collisions at $\sqrt{s}$ = 200 GeV. The deep neural network based PID simultaneously provides higher signal efficiency, signal-to-background ratio, and significance of the $\varphi$ peak compared to traditional PID techniques. Finally, a deep neural network assisted technique for measuring the muon purity in data is presented and discussed.

   ↳ physics.ins-detnucl-exNPA(2019)·0 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.