Tue·Jun 29, 2021Tuesday·June 29, 2021

1. 01*

   Beam-spin asymmetry $\mathbf{\Sigma }$ for ${\Sigma }^{-}$ hyperon photoproduction off the neutron

   Nicholas Zachariou · Edwin Munevar · Barry Berman · Petr Bydzovsky · Ales Cieply · Gerald Feldman · Yordanka Ilieva · Pawel Nadel-Turonski · Dalipor Skoupil · Andrey Sarantsev · Dan Watts

   We report a new measurement of the beam-spin asymmetry $\mathbf{\Sigma }$ for the $\vec{\gamma }n\to K^{+}{\Sigma }^{-}$ reaction using quasi-free neutrons in a liquid-deuterium target. The new dataset includes data at previously unmeasured photon energy and angular ranges, thereby providing new constraints on partial wave analyses used to extract properties of the excited nucleon states. The experimental data were obtained using the CEBAF Large Acceptance Spectrometer (CLAS), housed in Hall B of the Thomas Jefferson National Accelerator Facility (JLab). The CLAS detector measured reaction products from a liquid-deuterium target produced by an energy-tagged, linearly polarised photon beam with energies in the range 1.1 to 2.3 GeV. Predictions from an isobar model indicate strong sensitivity to $N(1720)3/2^{+}$, $\Delta (1900)1/2^{-}$, and $N(1895)1/2^{-}$, with the latter being a state not considered in previous photoproduction analyses. When our data are incorporated in the fits of partial-wave analyses, one observes significant changes in $\gamma$-$n$ couplings of the resonances which have small branching ratios to the $\pi N$ channel.

   nucl-exhep-exPLB(2022)·18 citations
2. 02*

   Monte Carlo simulations of the S-shaped neutron guides with asymmetric concave and convex surface coatings

   Alexandre P.S. Souza🇧🇷 · Luiz P. de Oliveira🇧🇷 · Frederico A. Genezini🇧🇷

   During the last decades, neutron beam transportation has been a well-known and established subject for designing proper neutron guides. However, sometimes unusual adaptation or adjustments are required out of original projects and after operation beginning of facilities. Inter-center transferring of instrument locations also requires a new approach that is not necessarily described in the literature. Inside these situations, the use of S-shaped guides has not been fully discussed in the literature. From a geometrical analysis, we develop a formalism of construction of a minimal S-shaped guide by only considering the exclusion of the Line-of-Sight. We study this guide model through the wavelength cutoff and the neutron transport efficiency analysis. Here, Monte Carlo simulations using MCSTAS software are applied. By intending to optimize these guide systems, simulations of this study also consider scenarios that have different supermirrors. A formalism to determine wavelength cutoff for unique and variable index guide systems is also developed. Simulation results show a good agreement between theoretical and simulated wavelength cutoff values. In addition, we have found specific configurations that combine efficient neutron transport and lower index values on the convex surfaces of curved guides that form the S-shaped guide.

   ↳ physics.ins-detnucl-exnucl-thquant-phNucl.Instrum.Meth.A(2022)·2 citations
3. 03*

   Rise and fall of $\Lambda$ and $\bar{\Lambda }$ global polarization in semi-central heavy-ion collisions at HADES, NICA and RHIC energies from the core-corona model

   Alejandro Ayala🇲🇽 · Isabel Domínguez🇲🇽 · Ivonne Maldonado🇲🇽 · María Elena Tejeda-Yeomans🇲🇽

   We compute the $\Lambda$ and $\overline{\Lambda }$ global polarizations in semi-central heavy-ion collisions using the core-corona model where the source of $\Lambda$'s and $\overline{\Lambda }$'s is taken as consisting of a high-density core and a less dense corona. We show that the overall properties of the polarization excitation functions can be linked to the relative abundance of $\Lambda$s coming from the core versus those coming from the corona. For low collision energies, the former are more abundant whereas for higher energies the latter become more abundant. The main consequence of this reversing of the relative abundance is that both polarizations peak at collision energies $\sqrt{s_{NN}}\lesssim 10$ GeV. The exact positions and heights of these peaks depend not only on this reversal of relative abundances, but also on the centrality class, which is directly related to the QGP volume and lifetime, as well as on the relative abundances of $\Lambda$s and $\overline{\Lambda }$s in the core and corona regions.The intrinsic polarizations are computed from a field theoretical approach that links the alignment of the strange quark spin with the thermal vorticity and modeling the QGP volume and lifetime using a Bjorken expansion scenario. We predict that the $\Lambda$ and $\overline{\Lambda }$ global polarizations should peak at the energy range accessible to NICA and HADES.

   ↳ hep-phnucl-exnucl-thPRC(2022)·29 citations
4. 04*

   Derivations for Locating Photon Emission Points Using Compton Imaging in GRETINA

   Robert Crabbs

   GRETA, the Gamma-Ray Energy Tracking Array, is an array of highly-segmented HPGe detectors designed to track {\gamma}-rays emitted in beam-physics experiments. Its high detection efficiency and state-of-the-art position resolution make it well-suited for imaging applications. In this paper, we derive the expressions for locating a photon emission point using Compton imaging. We also include expressions for corresponding uncertainty calculations.

   ↳ physics.ins-detnucl-exphysics.app-ph0 citations
5. 05*

   Using Compton Imaging to Locate Moving Gamma-Ray Sources in the GRETINA Detector

   Robert Crabbs · I-Yang Lee🇨🇳 · Kai Vetter

   GRETA, the Gamma-Ray Energy Tracking Array, is an array of highly-segmented HPGe detectors designed to track {\gamma}-rays emitted in beam-physics experiments. Its high detection efficiency and state-of-the-art position resolution make it well-suited for Compton imaging applications. In this paper, we use simulated imaging data to illustrate how GRETA can be used to locate the emission points of photons produced during beam experiments. This lays the groundwork for nuclear lifetime measurements using Compton imaging.

   ↳ physics.ins-detnucl-exphysics.app-ph0 citations
6. 06*

   Using Gamma-Ray Imaging to Measure Nuclear Lifetimes in the GRETINA Detector

   Robert Crabbs · I-Yang Lee🇨🇳 · Kai Vetter

   GRETA, the Gamma-Ray Energy Tracking Array, is an array of highly-segmented HPGe detectors designed to track gamma-rays emitted in beam-physics experiments. Its high detection efficiency and state-of-the-art position resolution make it well-suited for imaging applications. In this paper, we use simulated imaging data to illustrate how imaging can be applied to nuclear lifetime measurments. This approach can offer multiple benefits over traditional lifetime techniques such as RDM.

   ↳ physics.ins-detnucl-exphysics.app-ph0 citations
7. 07*

   Simulations of Compton Sequencing with the GRETINA Detector

   Robert Crabbs · I-Yang Lee🇨🇳 · Kai Vetter

   GRETA, the Gamma-Ray Energy Tracking Array, is an array of highly-segmented HPGe detectors designed to track gamma-rays emitted in beam-physics experiments. Its high detection efficiency and state-of-the-art position resolution enable it to reject Compton background and also sequence detected interactions via Compton kinematics. In this paper, we use simulated photon tracks to estimate how well interactions can be sequenced in the GRETA detector. This lays the groundwork for subsequent gamma-ray imaging applications such as nuclear lifetime measurements.

   ↳ physics.ins-detnucl-exphysics.app-ph0 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.