Mon·May 17, 2021Monday·May 17, 2021

1. 01*

   Deeply virtual Compton scattering using a positron beam in Hall-C at Jefferson Lab

   A. Afanasev🇺🇸 · I. Albayrak🇹🇷 · S. Ali🇺🇸 · M. Amaryan🇺🇸 · J. R. M. Annand🇬🇧 · A. Asaturyan🇦🇲 · V. Bellini🇮🇹 · V. V. Berdnikov🇺🇸 · M. Boer🇺🇸 · K. Brinkmann🇩🇪 · W. J. Briscoe🇺🇸 · A. Camsonne🇺🇸 and 62 other authors

   We propose to use the High Momentum Spectrometer of Hall C combined with the Neutral Particle Spectrometer (NPS) to perform high precision measurements of the Deeply Virtual Compton Scattering (DVCS) cross section using a beam of positrons. The combination of measurements with oppositely charged incident beams is the only unambiguous way to disentangle the contribution of the DVCS${}^2$ term in the photon electroproduction cross section from its interference with the Bethe-Heitler amplitude. This provides a stronger way to constrain the Generalized Parton Distributions of the nucleon. A wide range of kinematics accessible with an 11 GeV beam off an unpolarized proton target will be covered. The $Q^2-$dependence of each contribution will be measured independently.

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

   How Bayesian methods can improve $R$-matrix analyses of data: the example of the $dt$ Reaction

   Daniel Odell🇺🇸 · Carl Brune🇺🇸 · Daniel Phillips🇺🇸

   The ${}^3\mathrm{H}(d,n{)}^4\mathrm{He}$ reaction is of significant interest in nuclear astrophysics and nuclear applications. It is an important, early step in big-bang nucleosynthesis and a key process in nuclear fusion reactors. We use one- and two-level $R$-matrix approximations to analyze data on the cross section for this reaction at center-of-mass energies below 215 keV. We critically examine the data sets using a Bayesian statistical model that allows for both common-mode and additional point-to-point uncertainties. We use Markov Chain Monte Carlo sampling to evaluate this $R$-matrix-plus-statistical model and find two-level $R$-matrix results that are stable with respect to variations in the channel radii. The $S$ factor at 40 keV evaluates to $25.36(19)$ MeV b (68% credibility interval). We discuss our Bayesian analysis in detail and provide guidance for future applications of Bayesian methods to $R$-matrix analyses. We also discuss possible paths to further reduction of the $S$-factor uncertainty.

   ↳ nucl-thnucl-exphysics.data-anPRC(2022)·11 citations
3. 03*

   Radiative corrections of order $O(\alpha E_e/m_N)$ to Sirlin's radiative corrections of order $O(\alpha /\pi )$, induced by the hadronic structure of the neutron

   A. N. Ivanov🇦🇹 · R. Höllwieser🇩🇪 · N. I. Troitskaya🇦🇹 · M. Wellenzohn🇦🇹 · Ya. A. Berdnikov🇷🇺

   We investigate the contributions of the hadronic structure of the neutron to radiative $O(\alpha E_e/m_N)$ corrections (or the inner $O(\alpha E_e/m_N)$ RC) to the neutron beta decay, where $\alpha$, $E_e$ and $m_N$ are the fine-structure constant, the electron energy and the nucleon mass, respectively. We perform the calculation within the effective quantum field theory of strong low-energy pion-nucleon interactions described by the linear $\sigma$-model with chiral $SU(2)\times SU(2)$ symmetry and electroweak hadron-hadron, hadron-lepton and lepton-lepton interactions for the electron-lepton family with $SU(2{)}_L\times U(1{)}_Y$ symmetry of the Standard Electroweak Theory (Ivanov et al., Phys. Rev. D99, 093006 (2019)). We show that after renormalization, carried out in accordance with Sirlin's prescription (Sirlin, Phys. Rev. 164, 1767 (1967)), the inner $O(\alpha E_e/m_N)$ RC are of the order of a few parts of $10^{-5}-10^{-4}$. This agrees well with the results obtained in (Ivanov et al., Phys. Rev. D99, 093006 (2019)).

   ↳ hep-phnucl-exnucl-thPRD(2021)·5 citations
4. 04*

   The Radius of PSR J0740+6620 from NICER and XMM-Newton Data

   M. C. Miller🇺🇸 · F. K. Lamb🇺🇸 · A. J. Dittmann🇺🇸 · S. Bogdanov🇺🇸 · Z. Arzoumanian🇺🇸 · K. C. Gendreau🇺🇸 · S. Guillot🇫🇷 · W. C. G. Ho🇺🇸 · J. M. Lattimer🇺🇸 · M. Loewenstein🇺🇸 · S. M. Morsink🇨🇦 · P. S. Ray🇺🇸 and 16 other authors

   PSR J0740$+$6620 has a gravitational mass of $2.08\pm 0.07M_{\odot }$, which is the highest reliably determined mass of any neutron star. As a result, a measurement of its radius will provide unique insight into the properties of neutron star core matter at high densities. Here we report a radius measurement based on fits of rotating hot spot patterns to Neutron Star Interior Composition Explorer (NICER) and X-ray Multi-Mirror (XMM-Newton) X-ray observations. We find that the equatorial circumferential radius of PSR J0740$+$6620 is $13.7_{-1.5}^{+2.6}$ km (68%). We apply our measurement, combined with the previous NICER mass and radius measurement of PSR J0030$+$0451, the masses of two other $\sim 2M_{\odot }$ pulsars, and the tidal deformability constraints from two gravitational wave events, to three different frameworks for equation of state modeling, and find consistent results at $\sim 1.5-3$ times nuclear saturation density. For a given framework, when all measurements are included the radius of a $1.4M_{\odot }$ neutron star is known to $\pm 4$% (68% credibility) and the radius of a $2.08M_{\odot }$ neutron star is known to $\pm 5$%. The full radius range that spans the $\pm 1\sigma$ credible intervals of all the radius estimates in the three frameworks is $12.45\pm 0.65$ km for a $1.4M_{\odot }$ neutron star and $12.35\pm 0.75$ km for a $2.08M_{\odot }$ neutron star.

   ↳ astro-ph.HEgr-qcnucl-exnucl-thApJL(2021)·1580 citations
5. 05*

   Constraints on the dense matter equation of state and neutron star properties from NICER's mass-radius estimate of PSR J0740+6620 and multimessenger observations

   G. Raaijmakers🇳🇱 · S. K. Greif🇩🇪 · K. Hebeler🇩🇪 · T. Hinderer🇳🇱 · S. Nissanke🇳🇱 · A. Schwenk🇩🇪 · T. E. Riley🇳🇱 · A. L. Watts🇳🇱 · J. M. Lattimer🇺🇸 · W. C. G. Ho🇺🇸

   In recent years our understanding of the dense matter equation of state (EOS) of neutron stars has significantly improved by analyzing multimessenger data from radio/X-ray pulsars, gravitational wave events, and from nuclear physics constraints. Here we study the additional impact on the EOS from the jointly estimated mass and radius of PSR J0740+6620, presented in Riley et al. (2021) by analyzing a combined dataset from X-ray telescopes NICER and XMM-Newton. We employ two different high-density EOS parameterizations: a piecewise-polytropic (PP) model and a model based on the speed of sound in a neutron star (CS). At nuclear densities these are connected to microscopic calculations of neutron matter based on chiral effective field theory interactions. In addition to the new NICER data for this heavy neutron star, we separately study constraints from the radio timing mass measurement of PSR J0740+6620, the gravitational wave events of binary neutron stars GW190425 and GW170817, and for the latter the associated kilonova AT2017gfo. By combining all these, and the NICER mass-radius estimate of PSR J0030+0451 we find the radius of a 1.4 solar mass neutron star to be constrained to the 95% credible ranges 12.33^{+0.76}_{-0.81} km (PP model) and 12.18^{+0.56}_{-0.79} km (CS model). In addition, we explore different chiral effective field theory calculations and show that the new NICER results provide tight constraints for the pressure of neutron star matter at around twice saturation density, which shows the power of these observations to constrain dense matter interactions at intermediate densities.

   ↳ astro-ph.HEastro-ph.SRnucl-exnucl-thApJL(2021)·454 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.