Thu·Apr 25, 2019Thursday·April 25, 2019

1. 01*

   1H(n,el) as a Cross Section Reference in a White Source Neutron Beam With the fissionTPC

   N. I. Walsh🇺🇸 · J. T. Barker · N. S. Bowden🇺🇸 · K. J. Brewster · R. J. Casperson · T. Classen🇺🇸 · N. Fotiadis · U. Greife · E. Guardincerri🇺🇸 · C. Hagmann🇺🇸 · M. Heffner🇺🇸 · D. Hensle🇺🇸 and 24 other authors

   We provide a quantitative description of a method to measure neutron-induced fission cross sections in ratio to elastic hydrogen scattering in a white-source neutron beam with the fission Time Projection Chamber. This detector has measured precision fission cross section ratios using actinide references such as ${}^{235}$U(n,f) and ${}^{238}$U(n,f). However, by employing a more precise reference such as the H(n,el) cross section there is the potential to further reduce the evaluation uncertainties of the measured cross sections. In principle the fissionTPC could provide a unique measurement by simultaneously measuring both fission fragments and proton recoils over a large solid angle. We investigate one method with a hydrogenous gas target and with the neutron energy determined by the proton recoil kinematics. This method enables the measurement to be performed in a white-source neutron beam and with the current configuration of the fissionTPC. We show that while such a measurement is feasible in the energy range of 0.5 MeV to $\sim$10 MeV, uncertainties on the proton detection efficiency and the neutron energy resolution do not allow us to preform a fission ratio measurement to the desired precision. Utilizing either a direct measurement of the neutron time-of-flight for the recoil proton or a mono-energetic neutron source or some combination of both would provide a path to a sub-percent precision measurement.

   nucl-exphysics.ins-det0 citations
2. 02*

   Spectroscopy and lifetime measurements near the proton drip line: ${}^{26,27,28}$P

   B. Longfellow · A. Gade🇺🇸 · B. A. Brown🇺🇸 · D. Bazin🇺🇸 · P. C. Bender🇨🇦 · M. Bowry🇺🇸 · P. D. Cottle🇺🇸 · B. Elman · E. Lunderberg🇺🇸 · A. Magilligan🇺🇸 · M. Spieker🇺🇸 · D. Weisshaar🇺🇸 · S. J. Williams🇨🇦

   We report on the observation of excited states in the neutron-deficient phosphorus isotopes ${}^{26,27,28}$P via in-beam gamma-ray spectroscopy with both high-efficiency and high-resolution detector arrays. In ${}^{26}$P, a previously-unobserved level has been identified at 244(3) keV, two new measurements of the astrophysically-important 3/2${}^{+}$ resonance in ${}^{27}$P have been performed, gamma decays have been assigned to the proton-unbound levels at 2216 keV and 2483 keV in ${}^{28}$P, and the gamma-ray lineshape method has been used to make the first determination of the lifetimes of the two lowest-lying excited states in ${}^{28}$P. The expected Thomas-Ehrman shifts were calculated and applied to levels in the mirror nuclei. The resulting level energies from this procedure were then compared with the energies of known states in ${}^{26,27,28}$P.

   nucl-exPRC(2019)·11 citations
3. 03*

   Measurement of the mass difference and the binding energy of the hypertriton and antihypertriton

   STAR Collaboration: J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson · R. Aoyama · A. Aparin · D. Arkhipkin and 337 other authors

   According to the CPT theorem, which states that the combined operation of charge conjugation, parity transformation and time reversal must be conserved, particles and their antiparticles should have the same mass and lifetime but opposite charge and magnetic moment. Here, we test CPT symmetry in a nucleus containing a strange quark, more specifically in the hypertriton. This hypernucleus is the lightest one yet discovered and consists of a proton, a neutron, and a $\Lambda$ hyperon. With data recorded by the STAR detector{\cite{TPC,HFT,TOF}} at the Relativistic Heavy Ion Collider, we measure the $\Lambda$ hyperon binding energy $B_{\Lambda }$ for the hypertriton, and find that it differs from the widely used value{\cite{B_1973}} and from predictions{\cite{2019_weak, 1995_weak, 2002_weak, 2014_weak}}, where the hypertriton is treated as a weakly bound system. Our results place stringent constraints on the hyperon-nucleon interaction{\cite{Hammer2002, STAR-antiH3L}}, and have implications for understanding neutron star interiors, where strange matter may be present{\cite{Chatterjee2016}}. A precise comparison of the masses of the hypertriton and the antihypertriton allows us to test CPT symmetry in a nucleus with strangeness for the first time, and we observe no deviation from the expected exact symmetry.

   ↳ hep-exnucl-exnucl-thNat.Phys.(2020)·155 citations
4. 04*

   Comment on "Search for an axion-induced oscillating electric dipole moment for electrons using atomic magnetometers"

   P.-H. Chu🇺🇸 · Y. J. Kim🇺🇸 · I. Savukov🇺🇸

   In the recent work arXiv:1809.02446, the authors proposed a new method measuring the electron oscillating electric dipole moment (eOEDM) using atomic magnetomaters. This eOEDM is induced by the interaction between the electron magnetic dipole moment, electric field and axion field. The result is sensitive to the axion-photon coupling according to [Hill, PRD 91, 111702 (2015)]. Here we want to describe that the same experimental method can be also sensitive to the axion-electron coupling according to [Alexander and Sims, PRD 98, 015011 (2018)]. In this article, we will show the corresponding sensitivity plot and compare with other constraints.

   ↳ hep-phnucl-ex5 citations
5. 05*

   Quantifying Correlated Truncation Errors in Effective Field Theory

   J. A. Melendez🇺🇸 · R. J. Furnstahl🇺🇸 · D. R. Phillips🇺🇸 · M. T. Pratola🇺🇸 · S. Wesolowski🇺🇸

   Effective field theories (EFTs) organize the description of complex systems into an infinite sequence of decreasing importance. Predictions are made with a finite number of terms, which induces a truncation error that is often left unquantified. We formalize the notion of EFT convergence and propose a Bayesian truncation error model for predictions that are correlated across the independent variables, e.g., energy or scattering angle. Central to our approach are Gaussian processes that encode both the naturalness and correlation structure of EFT coefficients. Our use of Gaussian processes permits efficient and accurate assessment of credible intervals, allows EFT fits to easily include correlated theory errors, and provides analytic posteriors for physical EFT-related quantities such as the expansion parameter. We demonstrate that model-checking diagnostics---applied to the case of multiple curves---are powerful tools for EFT validation. As an example, we assess a set of nucleon-nucleon scattering observables in chiral EFT. In an effort to be self contained, appendices include thorough derivations of our statistical results. Our methods are packaged in Python code, called gsum, that is available for download on GitHub.

   ↳ nucl-thhep-phnucl-exphysics.data-anPRC(2019)·189 citations
6. 06*

   Development of an "$\alpha$-ToF" detector for correlated measurement of atomic masses and decay properties

   T. Niwase🇯🇵 · M. Wada🇺🇸 · P. Schury🇯🇵 · H. Haba🇯🇵 · S. Ishizawa🇯🇵 · Y. Ito🇯🇵 · D. Kaji🇯🇵 · S. Kimura🇯🇵 · H. Miyatake🇯🇵 · K. Morimoto🇯🇵 · K. Morita🇯🇵 · M. Rosenbusch🇩🇪 and 3 other authors

   We have developed a novel detector, referred to as an "$\alpha$-ToF detector", for correlated measurements of atomic masses and decay properties of low-yield, short-lived radioactive isotopes using a multi-reflection time-of-flight mass spectrograph. By correlating measured time-of-flight signals with decay events, it will be possible to suppress background events and obtain accurate, high-precision mass values even in cases of very low event rates. An offline test of the $\alpha$-ToF detector has shown that the time-of-flight detection efficiency for 5.48~MeV $\alpha$-rays is more than 90\% and yields a time resolution of 251.5(68)~ps and an energy resolution of 141.1(9)~keV. Using a two-dimensional spectrum of the correlated $\alpha$-ray energy and time-of-flight, the $\alpha$-rays from mixed $\alpha$ sources could be fairly well resolved.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2020)·14 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.