Wed·Feb 24, 2021Wednesday·February 24, 2021

1. 01*

   Elastic Positron-Proton Scattering at Low Q${}^2$

   Tyler J. Hague🇺🇸 · Dipangkar Dutta🇺🇸 · Douglas W. Higinbotham🇺🇸 · Xinzhan Bai🇺🇸 · Haiyan Gao🇺🇸 · Ashot Gasparian🇺🇸 · Kondo Gnanvo🇺🇸 · Vladimir Khachatryan🇺🇸 · Mahbub Khandaker🇺🇸 · Nilanga Liyanage🇺🇸 · Eugene Pasyuk🇺🇸 · Chao Peng🇺🇸 · Weizhi Xiong🇺🇸 · Jingyi Zhou🇺🇸

   Systematic differences in the the proton's charge radius, as determined by ordinary atoms and muonic atoms, have caused a resurgence of interest in elastic lepton scattering measurements. The proton's charge radius, defined as the slope of the charge form factor at Q${}^2$=0, does not depend on the probe. Any difference in the apparent size of the proton, when determined from ordinary versus muonic hydrogen, could point to new physics or need for the higher order corrections. While recent measurements seem to now be in agreement, there is to date no high precision elastic scattering data with both electrons and positrons. A high precision proton radius measurement could be performed in Hall B at Jefferson Lab with a positron beam and the calorimeter based setup of the PRad experiment. This measurement could also be extended to deuterons where a similar discrepancy has been observed between the muonic and electronic determination of deuteron charge radius. A new, high precision measurement with positrons, when viewed alongside electron scattering measurements and the forthcoming MUSE muon scattering measurement, could help provide new insights into the origins of the proton radius puzzle, and also provide new experimental constraints on radiative correction calculations.

   nucl-exEPJA(2021)·7 citations
2. 02*

   Revealing the structure of light pseudoscalar mesons at the Electron-Ion Collider

   John Arrington🇺🇸 · Carlos Ayerbe Gayoso🇺🇸 · Patrick C Barry🇺🇸 · Vladimir Berdnikov🇺🇸 · Daniele Binosi🇮🇹 · Lei Chang🇨🇳 · Markus Diefenthaler🇺🇸 · Minghui Ding🇮🇹 · Rolf Ent🇺🇸 · Tobias Frederico🇧🇷 · Yulia Furletova🇺🇸 · Tim J Hobbs🇺🇸 and 20 other authors

   How the bulk of the Universe's visible mass emerges and how it is manifest in the existence and properties of hadrons are profound questions that probe into the heart of strongly interacting matter. Paradoxically, the lightest pseudoscalar mesons appear to be the key to the further understanding of the emergent mass and structure mechanisms. These mesons, namely the pion and kaon, are the Nambu-Goldstone boson modes of QCD. Unravelling their partonic structure and the interplay between emergent and Higgs-boson mass mechanisms is a common goal of three interdependent approaches -- continuum QCD phenomenology, lattice-regularised QCD, and the global analysis of parton distributions -- linked to experimental measurements of hadron structure. Experimentally, the foreseen electron-ion collider will enable a revolution in our ability to study pion and kaon structure, accessed by scattering from the "meson cloud" of the proton through the Sullivan process. With the goal of enabling a suite of measurements that can address these questions, we examine key reactions to identify the critical detector system requirements needed to map tagged pion and kaon cross sections over a wide range of kinematics. The excellent prospects for extracting pion structure function and form factor data are shown, and similar prospects for kaon structure are discussed in the context of a worldwide programme. Successful completion of the programme outlined herein will deliver deep, far-reaching insights into the emergence of pions and kaons, their properties, and their role as QCD's Goldstone boson modes.

   nucl-exhep-phnucl-thJ.Phys.G(2021)·135 citations
3. 03*

   Determining the jet transport coefficient $\hat{q}$ from inclusive hadron suppression measurements using Bayesian parameter estimation

   S. Cao🇨🇳 · Y. Chen🇺🇸 · J. Coleman🇺🇸 · J. Mulligan🇺🇸 · P. M. Jacobs🇺🇸 · R. A. Soltz🇺🇸 · A. Angerami🇺🇸 · R. Arora🇺🇸 · S. A. Bass🇺🇸 · L. Cunqueiro🇺🇸 · T. Dai🇺🇸 · L. Du🇺🇸 and 35 other authors

   We report a new determination of $\hat{q}$, the jet transport coefficient of the Quark-Gluon Plasma. We use the JETSCAPE framework, which incorporates a novel multi-stage theoretical approach to in-medium jet evolution and Bayesian inference for parameter extraction. The calculations, based on the MATTER and LBT jet quenching models, are compared to experimental measurements of inclusive hadron suppression in Au+Au collisions at RHIC and Pb+Pb collisions at the LHC. The correlation of experimental systematic uncertainties is accounted for in the parameter extraction. The functional dependence of $\hat{q}$ on jet energy or virtuality and medium temperature is based on a perturbative picture of in-medium scattering, with components reflecting the different regimes of applicability of MATTER and LBT. In the multi-stage approach, the switch between MATTER and LBT is governed by a virtuality scale $Q_0$. Comparison of the posterior model predictions to the RHIC and LHC hadron suppression data shows reasonable agreement, with moderate tension in limited regions of phase space. The distribution of $\hat{q}/T^3$ extracted from the posterior distributions exhibits weak dependence on jet momentum and medium temperature $T$, with 90\% Credible Region (CR) depending on the specific choice of model configuration. The choice of MATTER+LBT, with switching at virtuality $Q_0$, has 90\% CR of $2<\hat{q}/T^3<4$ for $p_{\mathrm{T}}^{\mathrm{jet}}>40$ GeV/c. The value of $Q_0$, determined here for the first time, is in the range 2.0-2.7 GeV.

   ↳ nucl-thhep-phnucl-exPRC(2021)·196 citations
4. 04*

   $\beta$-Delayed Neutron and Fission Calculations with Relativistic QRPA and Statistical Model

   Futoshi Minato🇯🇵 · Tomislav Marketin · Nils Paar🇭🇷

   A role of \beta-delayed neutron emission and fission in r-process nucleosynthesis attracts a high interest. Although the number of study on them covering r-process nuclei is increasing recently, uncertainties of \beta-delayed neutron and fission are still large for r-process simulations. Our purpose is to make a new database on \beta-delayed neutron emission and fission rates. To this end, the data that are not investigated experimentally have to be predicted. Microscopic theoretical approaches based on a nuclear energy density functional and statistical models are one of the competent tools for the prediction. To obtain \beta strength function, p-n relativistic QRPA is adopted. Particle evaporations and fission from nuclear highly excited states are estimated by the Hauser-Feshbach statistical model. \beta-delayed neutron branching ratios (P_n) are calculated and compared with experimental data. \beta-delayed fission branching ratio (P_f) are also assessed by using four different fission barrier data. Calculated P_n values are in a good agreement with experimental data. It is found that energy withdrawal by \beta-delayed neutron emission sensitively varies P_n values for nuclei near the neutron drip line. P_f are sensitively dependent on fission barrier data. Newly calculated data on \beta-delayed neutron emission and fission are summarized as a table in supplement material. They are provided for studies of r-process as well as other fields such as nuclear engineering.

   ↳ nucl-thnucl-ex0 citations
5. 05*

   High-precision determination of the electric and magnetic radius of the proton

   Yong-Hui Lin🇩🇪 · Hans-Werner Hammer🇩🇪 · Ulf-G. Meißner🇩🇪

   Using dispersion theory with an improved description of the two-pion continuum based on the precise Roy-Steiner analysis of pion-nucleon scattering, we analyze recent data from electron-proton scattering. This allows for a high-precision determination of the electric and magnetic radius of the proton, $r_E=(0.838_{-0.004}^{+0.005}{}_{-0.003}^{+0.004})$fm and $r_M=(0.847\pm 0.004\pm 0.004)$fm, where the first error refers to the fitting procedure using bootstrap and the data while the second one refers to the systematic uncertainty related to the underlying spectral functions.

   ↳ hep-phhep-exhep-latnucl-ex+1PLB(2021)·49 citations
6. 06*

   $K_1/K^{\ast }$ enhancement as a signature of chiral symmetry restoration in heavy ion collisions

   Haesom Sung🇰🇷 · Sungtae Cho🇰🇷 · Juhee Hong🇰🇷 · Su Houng Lee🇰🇷 · Sanghoon Lim🇰🇷 · Taesoo Song🇩🇪

   Based on the fact that the mass difference between the chiral partners is an order parameter of chiral phase transition and that the chiral order parameter reduces substantially at the chemical freeze-out point in ultra-relativistic heavy ion collisions, we argue that the production ratio of $K_1$ over $K^{\ast }$ in such collisions should be substantially larger than that predicted in the statistical hadronization model. We further show that while the enhancement effect might be contaminated by the relatively larger decrease of $K_1$ meson than $K^{\ast }$ meson during the hadronic phase, the signal will be visible through a systematic study on centrality as the kinetic freeze-out temperature is higher and the hadronic life time shorter in peripheral collisions than in central collisions.

   ↳ nucl-thhep-phnucl-exPLB(2021)·13 citations
7. 07*

   alpha clustering and neutron-skin thickness of carbon isotopes

   Q. Zhao🇯🇵 · Y. Suzuki🇯🇵 · J. He🇨🇳 · B. Zhou🇯🇵 · M. Kimura🇯🇵

   The interplay between the formation of neutron skin and alpha cluster at the dilute surface of neutron-rich nuclei is one of the interesting subjects in the study of neutron-rich nuclei and nuclear clustering. A theoretical model has predicted that the growth of neutron skin will prevent the alpha clustering at the nuclear surface. Quite recently, this theoretical perspective; the suppression of alpha clustering by the neutron-skin formation was first confirmed experimentally in Sn isotopes as the reduction of the (p, p alpha) reaction cross-section. Motivated by the novel discovery, in this work, we have investigated the relationship between the neutron-skin thickness and alpha clustering in C isotopes. Based on the analysis by the antisymmetrized molecular dynamics, we show that the alpha spectroscopic factor at nuclear exterior decreases in neutron-rich C isotopes, and the clustering suppression looks correlated with the growth of the neutron-skin thickness.

   ↳ nucl-thnucl-exEPJA(2021)·17 citations
8. 08*

   Newly Evaluated Neutron Reaction Data on Chromium Isotopes

   G.P.A. Nobre🇺🇸 · M.T. Pigni🇺🇸 · D.A. Brown🇺🇸 · R. Capote🇦🇹 · A. Trkov🇸🇮 · K.H. Guber🇺🇸 · R. Arcilla🇺🇸 · J. Gutierrez🇺🇸 · A. Cuadra🇺🇸 · G. Arbanas🇺🇸 · B. Kos🇸🇮 · D. Bernard🇫🇷 · P. Leconte🇫🇷

   Neutron reaction data for the set of major chromium isotopes were reevaluated from the thermal energy range up to 20 MeV. In the low energy region, updates to the thermal values together with an improved $R$-matrix analysis of the resonance parameters characterizing the cluster of large $s$-wave resonances for ${}^{50,53}$Cr isotopes were performed. In the intermediate and high energy range up to 20 MeV, the evaluation methodology used statistical nuclear reaction models implemented in the EMPIRE code within the Hauser-Feshbach framework to evaluate the reaction cross sections and angular distributions. Exceptionally, experimental data were used to evaluate relevant cross sections above the resonance region up to 5 MeV in the major ${}^{52}$Cr isotope. Evaluations were benchmarked with Monte Carlo simulations of a small suite of critical assemblies highly sensitive to Chromium data, and with the Oktavian shielding benchmark to judge deep penetration performance with a 14-MeV D-T neutron source. A significant improvement in performance is demonstrated compared to existing evaluations.

   ↳ nucl-thnucl-exNucl.Data Sheets(2021)·10 citations
9. 09*

   Beam-normal single-spin asymmetry in elastic scattering of electrons from a spin-0 nucleus

   Oleksandr Koshchii🇩🇪 · Mikhail Gorchtein🇩🇪 · Xavier Roca-Maza🇮🇹 · Hubert Spiesberger🇩🇪

   We study the beam-normal single-spin asymmetry (BNSSA) in high-energy elastic electron scattering from several spin-0 nuclei. Existing theoretical approaches work in the plane-wave formalism and predict the BNSSA to scale as $\sim A/Z$ with the atomic number $Z$ and nuclear mass number $A$. While this prediction holds for light and intermediate nuclei, a striking disagreement in both the sign and the magnitude of BNSSA was observed by the PREX collaboration for ${}^{208}$Pb, coined the "PREX puzzle". To shed light on this disagreement, we go beyond the plane-wave approach which neglects Coulomb distortions known to be significant for heavy nuclei. We explicitly investigate the dependence of BNSSA on $A$ and $Z$ by i) including inelastic intermediate states' contributions into the Coulomb problem in the form of an optical potential, ii) by accounting for the experimental information on the $A$-dependence of the Compton slope parameter, and iii) giving a thorough account of the uncertainties of the calculation. Despite of these improvements, the PREX puzzle remains unexplained. We discuss further strategies to resolve this riddle.

   ↳ nucl-thhep-phnucl-exPRC(2021)·15 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.