Wed·Feb 3, 2021Wednesday·February 3, 2021

1. 01*

   Development of a Reference Database for Beta-Delayed Neutron Emission

   P. Dimitriou🇦🇹 · I. Dillmann🇨🇦 · B. Singh🇨🇦 · V. Piksaikin🇷🇺 · K.P. Rykaczewski🇺🇸 · J.L. Tain🇪🇸 · A. Algora🇪🇸 · K. Banerjee🇮🇳 · I.N. Borzov🇷🇺 · D. Cano-Ott🇪🇸 · S. Chiba🇯🇵 · M. Fallot🇫🇷 and 21 other authors

   Beta-delayed neutron emission is important for nuclear structure and astrophysics as well as for reactor applications. Significant advances in nuclear experimental techniques in the past two decades have led to a wealth of new measurements that remain to be incorporated in the databases. We report on a coordinated effort to compile and evaluate all the available beta-delayed neutron emission data. The different measurement techniques have been assessed and the data have been compared with semi-microscopic and microscopic-macroscopic models. The new microscopic database has been tested against aggregate total delayed neutron yields, time-dependent group parameters in 6-and 8-group re-presentation, and aggregate delayed neutron spectra. New recommendations of macroscopic delayed-neutron data for fissile materials of interest to applications are also presented. The new Reference Database for Beta-Delayed Neutron Emission Data is available online at: http://www-nds.iaea.org/beta-delayed-neutron/database.html.

   nucl-exNucl.Data Sheets(2021)·29 citations
2. 02*

   Johnson-Nyquist Noise Effects in Neutron Electric-Dipole-Moment Experiments

   N. J. Ayres (1)🇨🇭 · G. Ban (2)🇫🇷 · G. Bison (3)🇨🇭 · K. Bodek (4)🇵🇱 · V. Bondar (1)🇨🇭 · P.-J. Chiu (1 and 3)🇨🇭 · B. Clement (5)🇫🇷 · C. B. Crawford (6)🇺🇸 · M. Daum (3)🇨🇭 · S. Emmenegger (1)🇨🇭 · M. Fertl (7)🇩🇪 · A. Fratangelo (8)🇨🇭 and 28 other authors

   Magnetic Johnson-Nyquist noise (JNN) originating from metal electrodes, used to create a static electric field in neutron electric-dipole-moment (nEDM) experiments, may limit the sensitivity of measurements. We present here the first dedicated study on JNN applied to a large-scale long-measurement-time experiment with the implementation of a co-magnetometry. In this study, we derive surface- and volume-averaged root-mean-square normal noise amplitudes at a certain frequency bandwidth for a cylindrical geometry. In addition, we model the source of noise as a finite number of current dipoles and demonstrate a method to simulate temporal and three-dimensional spatial dependencies of JNN. The calculations are applied to estimate the impact of JNN on measurements with the new apparatus, n2EDM, at the Paul Scherrer Institute. We demonstrate that the performances of the optically pumped ${}^{133}$Cs magnetometers and ${}^{199}$Hg co-magnetometers, which will be used in the apparatus, are not limited by JNN. Further, we find that in measurements deploying a co-magnetometer system, the impact of JNN is negligible for nEDM searches down to a sensitivity of $4\times 10^{-28}e\cdot \mathrm{cm}$ in a single measurement; therefore, the use of economically and mechanically favored solid aluminum electrodes is possible.

   nucl-exphysics.atom-phPRA(2021)·5 citations
3. 03*

   Deuterium scattering experiments in CTEQ global QCD analyses: a comparative investigation

   A. Accardi🇺🇸 · T. J. Hobbs🇺🇸 · X. Jing🇺🇸 · P. M. Nadolsky🇺🇸

   Experimental measurements in deep-inelastic scattering and lepton-pair production on deuterium targets play an important role in the flavor separation of $u$ and $d$ (anti)quarks in global QCD analyses of the parton distribution functions (PDFs) of the nucleon. We investigate the impact of theoretical corrections accounting for the light-nuclear structure of the deuteron upon the fitted $u,d$-quark, gluon, and other PDFs in the CJ15 and CT18 families of next-to-leading order CTEQ global analyses. The investigation is done using the $L_2$ sensitivity statistical method, which provides a common metric to quantify the strength of experimental constraints on various PDFs and ratios of PDFs in the two distinct fitting frameworks. Using the $L_2$ sensitivity and other approaches, we examine the compatibility of deuteron data sets with other fitted experiments under varied implementations of the deuteron corrections. We find that freely-fitted deuteron corrections modify the PDF uncertainty at large momentum fractions and will be relevant for future PDFs affecting electroweak precision measurements.

   ↳ hep-phhep-exnucl-exnucl-thEPJC(2021)·31 citations
4. 04*

   A Standard Model Explanation for the "ATOMKI Anomaly"

   A. Aleksejevs🇨🇦 · S. Barkanova🇨🇦 · Yu.G. Kolomensky🇺🇸 · B. Sheff🇺🇸

   Using the $e^{+}{e}^{-}$ pair spectrometer at the 5 MV Van de Graaff accelerator at the Institute for Nuclear Research, Hungarian Academy of Sciences (ATOMKI), Krasznahorkay et al. have claimed a 6.8$\sigma$ excess at high $e^{+}{e}^{-}$ opening angles in the internal pair creation isoscalar transition ${}^8\mathrm{Be}(18.15)\to {}^8\mathrm{Be}{e}^{+}{e}^{-}$. A hypothetical gauge boson with the mass circa $17$ MeV, "X17", has been proposed as an explanation for the excess. We show that the observed experimental structure can be reproduced within the Standard Model by adding the full set of second-order corrections and the interference terms to the Born-level decay amplitudes considered by Krasznahorkay et al. We implement a detailed model of the ATOMKI detector, and also show how experimental selection and acceptance bias exacerbate the apparent difference between the experimental data and the Born-level prediction.

   ↳ hep-phnucl-exnucl-th36 citations
5. 05*

   Fresh extraction of the proton charge radius from electron scattering

   Zhu-Fang Cui🇨🇳 · Daniele Binosi🇮🇹 · Craig D. Roberts🇨🇳 · Sebastian M. Schmidt🇩🇪

   We present a novel method for extracting the proton radius from elastic electron-proton ($ep$) scattering data. The approach is based on interpolation via continued fractions augmented by statistical sampling and avoids any assumptions on the form of function used for the representation of data and subsequent extrapolation onto $Q^2\simeq 0$. Applying the method to extant modern $ep$ data sets, we find that all results are mutually consistent and, combining them, arrive at $r_p=0.847(8)$fm. This result compares favourably with values obtained from contemporary measurements of the Lamb shift in muonic hydrogen, transitions in electronic hydrogen, and muonic deuterium spectroscopy.

   ↳ hep-phhep-exhep-latnucl-ex+1PRL(2021)·41 citations
6. 06*

   Hyperfine structure of the $2{}^{3}P$ state in ${}^9$Be and the nuclear quadrupole moment

   Mariusz Puchalski🇵🇱 · Jacek Komasa🇵🇱 · Krzysztof Pachucki🇵🇱

   We have performed accurate calculations of the hyperfine structure of the $2{}^{3}P$ state in the ${}^9$Be atom with the help of highly optimized, explicitly correlated functions, accounting for the leading finite nuclear mass, radiative, nuclear structure and relativistic effects. By comparison with measurements, we have determined the ${}^9$Be nuclear quadrupole moment to be $Q_{\mathrm{N}}=0.05350(14)$ barns, which is not only the most accurate result, but also disagrees with previous determinations.

   ↳ physics.atom-phnucl-exPRResearch(2021)·7 citations
7. 07*

   Forces within hadrons on the light front

   Adam Freese🇺🇸 · Gerald A. Miller🇺🇸

   In this work, we find the light front densities for momentum and forces, including pressure and shear forces, within hadrons. This is achieved by deriving relativistically correct expressions relating these densities to the gravitational form factors $A(t)$ and $D(t)$ associated with the energy momentum tensor. The derivation begins from the fundamental definition of density in a quantum field theory, namely the expectation value of a local operator within a spatially-localized state. We find that it is necessary to use the light front formalism to define a density that corresponds to internal hadron structure. When using the instant form formalism, it is impossible to remove the spatial extent of the hadron wave function from any density, and -- even within instant form dynamics -- one does not obtain a Breit frame Fourier transform for a properly defined density. Within the front formalism, we derive new expressions for various mechanical properties of hadrons, including the mechanical radius, as well as for stability conditions. The multipole ansatz for the form factors is used as an example to illustrate all of these findings.

   ↳ hep-phnucl-exnucl-thPRD(2021)·93 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.