Thu·Sep 19, 2019Thursday·September 19, 2019

1. 01*

   Baryon -- anti-Baryon Photoproduction

   Hao Li🇺🇸 · Reinhard A. Schumacher🇺🇸

   Baryon - anti-baryon photoproduction off a proton target is being studied in detail at Jefferson Lab with the GlueX Experiment. We observe $p\bar{p}$ and, for the first time, $\Lambda \bar{\Lambda }$ photoproduction (with $\Lambda \to {\pi }^{-}p$, $\bar{\Lambda }\to {\pi }^{+}\bar{p}$) from thresholds up to $E_{\gamma }=11.4$ GeV. Preliminary spectra from data accumulated during the GlueX Phase-I period are shown. Angular distributions of the photoproduced hyperons indicate more than one production mechanism in the reaction channel $\gamma p\to \Lambda \bar{\Lambda }p$. A Monte Carlo simulation with four mechanisms, tested through comparison between simulation and experimental data, is presented.

   nucl-exhep-exAIP Conf.Proc.(2020)·5 citations
2. 02*

   Cyclotron Radiation Emission Spectroscopy Signal Classification with Machine Learning in Project 8

   A. Ashtari Esfahani🇺🇸 · S. Boser🇩🇪 · N. Buzinsky🇺🇸 · R. Cervantes🇺🇸 · C. Claessens🇩🇪 · L. de Viveiros🇺🇸 · M. Fertl🇺🇸 · J. A. Formaggio🇺🇸 · L. Gladstone🇺🇸 · M. Guigue🇺🇸 · K. M. Heeger🇺🇸 · J. Johnston🇺🇸 and 23 other authors

   The Cyclotron Radiation Emission Spectroscopy (CRES) technique pioneered by Project 8 measures electromagnetic radiation from individual electrons gyrating in a background magnetic field to construct a highly precise energy spectrum for beta decay studies and other applications. The detector, magnetic trap geometry, and electron dynamics give rise to a multitude of complex electron signal structures which carry information about distinguishing physical traits. With machine learning models, we develop a scheme based on these traits to analyze and classify CRES signals. Understanding and proper use of these traits will be instrumental to improve cyclotron frequency reconstruction and help Project 8 achieve world-leading sensitivity on the tritium endpoint measurement in the future.

   nucl-exhep-exNew J.Phys.(2020)·15 citations
3. 03*

   New data on $\vec{\gamma }\vec{p}\to \eta p$ with polarized photons and protons and their implications for $N^{\ast }\to N\eta$ decays

   J. Müller · J. Hartmann · M. Grüner · F. Afzal · A. V. Anisovich · B. Bantes · D. Bayadilov · R. Beck · M. Becker · Y. Beloglazov · M. Berlin · M. Bichow and 77 other authors

   The polarization observables $T,E,P,H$, and $G$ in photoproduction of $\eta$ mesons off protons are measured for photon energies from threshold to $W=2400$MeV ($T$), 2280 MeV ($E$), 1620 MeV ($P,H$), or 1820 MeV ($G$), covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, JüBo, and BnGa partial-wave analyses. A refit within the BnGa approach including further data yields precise branching ratios for the $N\eta$ decay of nucleon resonances. A $N\eta$-branching ratio of $0.33\pm 0.04$ for $N(1650)1/2^{-}$ is found, which reduces the large and controversially discussed $N\eta$-branching ratio difference of the two lowest mass $J^P=1/2^{-}$-resonances significantly.

   nucl-exPLB(2020)·34 citations
4. 04*

   The DireXeno Experiment -- Measuring Correlated Scintillation Signatures in Liquid Xenon

   R. Itay🇮🇱 · P. Z. Szabo🇮🇱 · G. Koltman🇮🇱 · M.M. Devi🇮🇱 · M. Shutman🇮🇱 · H. Landsman🇮🇱 · R. Budnik🇮🇱

   We present a detector apparatus, DireXeno (DIRectinal Xenon), designed to measure the spatial and temporal properties of scintillation in liquid xenon to very high accuracy. The properties of scintillation are of primary importance for dark matter and neutrinoless double beta decay experiments, however the complicated microphysics involved limits theoretical predictions. We will explore the possibility that scintillation emission exhibits correlation in light emission such as super-radiance, which depends on the type of interaction. Such properties of scintillation light may open a new window for background rejection as well as directionality measurements. We present the technical design and the concepts driving it, and demonstrate that statistical treatment will enable detecting anisotropy of as little as 10% of the photons. We show results from commissioning runs in which the detector operated for over 44 days in stable conditions. The time resolution for individual photons in different PMTs was measured to be $\lesssim 1.3$ ns FWHM, corresponding to $\lesssim 0.55$ ns (1 $\sigma$).

   ↳ physics.ins-detnucl-exJINST(2020)·1 citation
5. 05*

   Pion Valence Structure from Ioffe Time Pseudo-Distributions

   Bálint Joó🇺🇸 · Joseph Karpie🇺🇸 · Kostas Orginos🇺🇸 · Anatoly V. Radyushkin🇺🇸 · David G. Richards🇺🇸 · Raza Sabbir Sufian🇺🇸 · Savvas Zafeiropoulos🇩🇪

   We present a calculation of the pion valence quark distribution extracted using the formalism of reduced Ioffe time pseudo-distributions or more commonly known as pseudo-PDFs. Our calculation is carried out on two different 2+1 flavor QCD ensembles using the isotropic-clover fermion action, with lattice dimensions $24^3\times 64$ and $32^3\times 96$ at the lattice spacing of $a=0.127$ fm, and with the quark mass equivalent to a pion mass of $m_{\pi }\simeq 415$ MeV. We incorporate several combinations of smeared-point and smeared-smeared pion source-sink interpolation fields in obtaining the lattice QCD matrix elements using the summation method. After one-loop perturbative matching and combining the pseudo-distributions from these two ensembles, we extract the pion valence quark distribution using a phenomenological functional form motivated by the global fits of parton distribution functions. We also calculate the lowest four moments of the pion quark distribution through the "OPE without OPE". We present a qualitative comparison between our lattice QCD extraction of the pion valence quark distribution with that obtained from global fits and previous lattice QCD calculations.

   ↳ hep-lathep-phnucl-exnucl-thPRD(2019)·159 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.