Fri·Jul 19, 2019Friday·July 19, 2019

1. 01*

   Pion and Kaon Structure at the Electron-Ion Collider

   Arlene C. Aguilar🇧🇷 · Zafir Ahmed🇨🇦 · Christine Aidala🇺🇸 · Salina Ali🇺🇸 · Vincent Andrieux🇺🇸 · John Arrington🇺🇸 · Adnan Bashir🇲🇽 · Vladimir Berdnikov🇺🇸 · Daniele Binosi🇮🇹 · Lei Chang🇨🇳 · Chen Chen🇩🇪 · Muyang Chen🇨🇳 and 39 other authors

   Understanding the origin and dynamics of hadron structure and in turn that of atomic nuclei is a central goal of nuclear physics. This challenge entails the questions of how does the roughly 1 GeV mass-scale that characterizes atomic nuclei appear; why does it have the observed value; and, enigmatically, why are the composite Nambu-Goldstone (NG) bosons in quantum chromodynamics (QCD) abnormally light in comparison? In this perspective, we provide an analysis of the mass budget of the pion and proton in QCD; discuss the special role of the kaon, which lies near the boundary between dominance of strong and Higgs mass-generation mechanisms; and explain the need for a coherent effort in QCD phenomenology and continuum calculations, in exa-scale computing as provided by lattice QCD, and in experiments to make progress in understanding the origins of hadron masses and the distribution of that mass within them. We compare the unique capabilities foreseen at the electron-ion collider (EIC) with those at the hadron-electron ring accelerator (HERA), the only previous electron-proton collider; and describe five key experimental measurements, enabled by the EIC and aimed at delivering fundamental insights that will generate concrete answers to the questions of how mass and structure arise in the pion and kaon, the Standard Model's NG modes, whose surprisingly low mass is critical to the evolution of our Universe.

   nucl-exhep-exhep-lathep-ph+1EPJA(2019)·210 citations
2. 02*

   Reduced uncertainty of the axial $\gamma Z$-box correction to the proton's weak charge

   Jens Erler🇩🇪 · Mikhail Gorchtein🇩🇪 · Oleksandr Koshchii🇩🇪 · Chien-Yeah Seng🇩🇪 · Hubert Spiesberger🇩🇪

   We present the fully up-to-date calculation of the $\gamma Z$-box correction which needs to be taken into account to determine the weak mixing angle at low energies from parity-violating electron proton scattering. We make use of neutrino and antineutrino inclusive scattering data to predict the parity-violating structure function $F_3^{\gamma Z}$ by isospin symmetry. Our new analysis confirms previous results for the axial contribution to the $\gamma Z$-box graph, and reduces the uncertainty by a factor of~2. In addition, we note that the presence of parity-violating photon-hadron interactions induces an additional contribution via $F_3^{\gamma \gamma }$. Using experimental and theoretical constraints on the nucleon anapole moment we are able to estimate the uncertainty associated with this contribution. We point out that future measurements are expected to significantly reduce this latter uncertainty.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2019)·13 citations
3. 03*

   Search of cluster structure in nuclei via analysis of bremsstrahlung emission

   Sergei P. Maydanyuk (2 and 3)🇨🇳 · Peng-Ming Zhang (1 and 2)🇨🇳 · Li-Ping Zou (2) ((1) School of Physics and Astronomy, Sun Yat-Sen University, Zhuhai, China, (2) Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000, China, (3) Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kiev, 03680, Ukraine)🇨🇳

   We investigate emission of bremsstrahlung photons during scattering of $\alpha$-particles off nuclei. For that, we construct bremsstrahlung model for $\alpha$-nucleus scattering, where a new formalism for coherent and incoherent bremsstrahlung emissions in elastic scattering and mechanisms in inelastic scattering is added. Basing of this approach, we analyze experimental bremsstrahlung cross-sections in the scattering of $\alpha$-particles off the \isotope[59]{Co}, \isotope[116]{Sn}, \isotope[\rm nat]{Ag} and \isotope[197]{Au} nuclei at 50 MeV of $\alpha$-particles beam measured at the Variable Energy Cyclotron Centre, Calcutta. We observe oscillations in the calculated spectra for elastic scattering for each nucleus. But, for \isotope[59]{Co}, \isotope[116]{Sn} and \isotope[\rm nat]{Ag} we obtain good agreement between calculated coherent spectrum with incoherent contribution for elastic scattering with experimental data in the full photon energy region. For heavy nucleus \isotope[197]{Au} we find that (1) Oscillating behavior of the calculated spectrum of coherent emission in elastic scattering is in disagreement with experimental data, (2) Inclusion of incoherent emission improves description of the data, but summarized spectrum is in satisfactory agreement with the experimental data. To understand unknown modification of wave function for scattering, we add new mechanisms of inelastic scattering to calculations and extract information about unknown new amplitude of such mechanisms from experimental data analysis. This amplitude has maxima at some energies, that characterizes existence of states of the most compact structures (clusters) in nucleus-target. We explain origin of oscillations in the bremsstrahlung spectra for elastic scattering (at first time). New information about coherent and incoherent contributions is extracted for studied reactions.

   ↳ nucl-thhep-phnucl-ex2 citations
4. 04*

   Nuclear electric dipole moment in the cluster model with a triton: ${}^7$Li and ${}^{11}$B

   Nodoka Yamanaka🇫🇷 · Taiichi Yamada🇯🇵 · Yasuro Funaki🇯🇵

   We calculate the electric dipole moment (EDM) of the nuclei ${}^7$Li and ${}^{11}$B in the cluster model with $\alpha$ (${}^4$He) and triton (${}^3$H) clusters as degrees of freedom. The ${}^7$Li and ${}^{11}$B nuclei are treated in the two- and three-body problem, respectively, using the Gaussian expansion method, assuming the one-meson exchange P, CP-odd nuclear forces. We find that ${}^7$Li and ${}^{11}$B have larger sensitivity to the CP violation than the deuteron. It is also suggested that the EDMs of ${}^7$Li and ${}^{11}$B, together with those of ${}^6$Li, ${}^9$Be and the $1/2_1^{+}$ excited state of ${}^{13}$C, obey an approximate counting rule accounting for the EDM of the cluster and the $\alpha -N$ polarization. We show their sensitivity on the hadronic level CP violation in terms of the chiral effective field theory, and discuss their role in probing new physics beyond the standard model.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2019)·20 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.