Thu·May 31, 2018Thursday·May 31, 2018

1. 01*

   Rapidity scan in heavy ion collisions at $\sqrt{s_{\mathrm{NN}}}=72$~GeV using a viscous hydro + cascade model

   Iurii Karpenko🇫🇷

   In this note we discuss the rapidity dependence of the initial and final conditions for hydrodynamic evolution as well as the resulting basic hadronic observables in heavy ion collisions at $\sqrt{s_{\mathrm{NN}}}=72$ GeV in the framework of a viscous hydro+cascade model vHLLE+UrQMD. The resulting rapidity dependences are driven to a big extent by the initial state, which is simulated with the UrQMD cascade. The results can serve as a prediction for future experiments such as the AFTER@LHC or the BES-II program at STAR.

   ↳ nucl-thhep-phnucl-exActa Phys.Polon.B(2019)·14 citations
2. 02*

   Can Long-Range Nuclear Properties Be Influenced By Short Range Interactions? A chiral dynamics estimate

   G.A. Miller🇺🇸 · A. Beck🇺🇸 · S. May-Tal Beck🇺🇸 · L.B. Weinstein🇺🇸 · E. Piasetzky🇮🇱 · O. Hen🇺🇸

   Recent experiments and many-body calculations indicate that approximately 20\% of the nucleons in medium and heavy nuclei ($A\ge 12$) are part of short-range correlated (SRC) primarily neutron-proton ($np$) pairs. We find that using chiral dynamics to account for the formation of $np$ pairs due to the effects of iterated and irreducible two-pion exchange leads to values consistent with the 20\% level. We further apply chiral dynamics to study how these correlations influence the calculations of nuclear charge radii, that traditionally truncate their effect, to find that they are capable of introducing non-negligible effects.

   ↳ nucl-thhep-phnucl-exPLB(2019)·33 citations
3. 03*

   Design and test of a compact and high-resolution time-of-flight measurement device for cold neutron beams

   Damien Roulier🇫🇷 · Valery Nesvizhevsky🇫🇷 · Benoît Clément🇫🇷 · Guilhem Freche🇫🇷 · Guillaume Pignol🇫🇷 · Dominique Rebreyend🇫🇷 · Francis Vezzu🇫🇷 · Stefan Baeßler🇺🇸 · Alexander Strelkov🇷🇺

   A time-of-flight device was developed to characterize wavelength distribution and uniformity of a cold neutron beam. This device is very compact -- the distance of flight is $60$ cm -- but achieves very high resolution -- the intrinsic resolution $\Delta \lambda /\lambda =2.4\cdot 10^{-3}$ at $\lambda =0.89$ nm. The time-of-flight device is composed of a fixed slit, a disk rotating up to $216$ Hz and a neutron detector with a thin spherical conversion layer with the chopper slit in its focus. The device accepts the complete angular divergence of the initial neutron beam. The efficiency of neutron detection is constant over the detector area. Systematic corrections caused by neutron scattering in air are minimized due to the reduction of the time-of-flight length. Measurements have been performed on the beamline of the GRANIT experiment at ILL (part of the H172 beamline) on level C, and the first order diffraction peak of the crystal monochromator used for the GRANIT beamline was found to be at $\lambda =0.8961(11)$ nm, and having a width of $\sigma =0.0213(13)$ nm.

   ↳ physics.ins-detnucl-exPhys.Rev.Accel.Beams(2019)·0 citations
4. 04*

   A percent-level determination of the nucleon axial coupling from Quantum Chromodynamics

   Chia Cheng Chang🇺🇸 · Amy Nicholson🇺🇸 · Enrico Rinaldi🇺🇸 · Evan Berkowitz🇩🇪 · Nicolas Garron🇬🇧 · David A. Brantley🇺🇸 · Henry Monge-Camacho🇺🇸 · Christopher J. Monahan🇺🇸 · Chris Bouchard🇬🇧 · M.A. Clark🇺🇸 · Bálint Joó🇺🇸 · Thorsten Kurth🇺🇸 and 3 other authors

   The $\text{axial coupling of the nucleon}$, $g_A$, is the strength of its coupling to the $\text{weak}$ axial current of the Standard Model of particle physics, in much the same way as the electric charge is the strength of the coupling to the electromagnetic current. This axial coupling dictates the rate at which neutrons decay to protons, the strength of the attractive long-range force between nucleons and other features of nuclear physics. Precision tests of the Standard Model in nuclear environments require a quantitative understanding of nuclear physics rooted in Quantum Chromodynamics, a pillar of the Standard Model. The prominence of $g_A$ makes it a benchmark quantity to determine theoretically - a difficult task because quantum chromodynamics is non-perturbative, precluding known analytical methods. Lattice Quantum Chromodynamics provides a rigorous, non-perturbative definition of quantum chromodynamics that can be implemented numerically. It has been estimated that a precision of two percent would be possible by 2020 if two challenges are overcome: contamination of $g_A$ from excited states must be controlled in the calculations and statistical precision must be improved markedly. Here we report a calculation of $g_A^{QCD}=1.271\pm 0.013$, using an unconventional method inspired by the Feynman-Hellmann theorem that overcomes these challenges.

   ↳ hep-lathep-exhep-phnucl-ex+1Nature(2018)·237 citations
5. 05*

   $\mathbf{\eta }$-${}^4\mathrm{He}$ interaction from the $\mathbf{dd}\to {\mathbf{\eta }}^4\mathrm{He}$ reaction near threshold

   Ju-Jun Xie🇨🇳 · Wei-Hong Liang🇨🇳 · Eulogio Oset🇪🇸

   We analyze the data on the total cross sections for the $dd\to \eta {}^4\mathrm{He}$ reaction close to threshold and look for possible ${\eta }^4\mathrm{He}$ bound states. We develop a framework in which the ${\eta }^4\mathrm{He}$ optical potential is the key ingredient, rather than parameterizing the scattering matrix, as is usually done. The strength of this potential, together with some production parameters, are fitted to the available experimental data. The relationship of the scattering matrix to the optical potential is established using the Bethe-Salpeter equation and the ${\eta }^4\mathrm{He}$ loop function incorporates the range of the interaction given by the experimental ${}^4\mathrm{He}$ density. However, when we look for poles of the scattering matrix, we get poles in the bound region, poles in the positive energy region or no poles at all. If we further restrict the results with constraints from a theoretical model with all its uncertainties the bound states are not allowed. However, we find a bump structure in $|T{|}^2$ of the ${\eta }^4\mathrm{He}\to {\eta }^4\mathrm{He}$ amplitude below threshold for the remaining solutions.

   ↳ nucl-thhep-phnucl-exEPJA(2019)·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.