Fri·Nov 6, 2015Friday·November 6, 2015

1. 01*

   Revalidation of the isobaric multiplet mass equation for the $A=20$ quintet

   B. E. Glassman🇺🇸 · D. Pérez-Loureiro🇺🇸 · C. Wrede🇺🇸 · J. Allen🇺🇸 · D. W. Bardayan🇺🇸 · M. B. Bennett🇺🇸 · B. A. Brown🇺🇸 · K. A. Chipps🇺🇸 · M. Febbraro🇺🇸 · C. Fry🇺🇸 · M. R. Hall🇺🇸 · O. Hall and 9 other authors

   An unexpected breakdown of the isobaric multiplet mass equation in the $A=20$, $T=2$ quintet was recently reported, presenting a challenge to modern theories of nuclear structure. In the present work, the excitation energy of the lowest $T=2$ state in ${}^{20}$Na has been measured to be $6498.4\pm 0.2_{\text{stat}}\pm 0.4_{\text{syst}}$ keV by using the superallowed $0^{+}\to 0^{+}$ beta decay of ${}^{20}$Mg to access it and an array of high-purity germanium detectors to detect its $\gamma$-ray deexcitation. This value differs by 27 keV (1.9 standard deviations) from the recommended value of $6525\pm 14$ keV and is a factor of 28 more precise. The isobaric multiplet mass equation is shown to be revalidated when the new value is adopted.

   nucl-exPRC(2015)·21 citations
2. 02*

   XYZ Meson Spectroscopy

   Stephen Lars Olsen🇰🇷

   Many candidate multiquark mesons, i.e., mesons with substructures that are more complex than the quark-antiquark prescription that is in the textbooks, have recently been observed. Many of the most recently observed candidate states are electrically charged and have the same spin and parity, namely JP=1+. In this talk I give an overview of the current experimental situation and identify patterns among the recently discovered JP=1+ states, compare these patterns with expectations from proposed theoretical models, and the existence of additional, related states that might be accessible at current and future experiments. In addition, models that attribute the observed states to kinematically induced cusps are discussed.

   ↳ hep-exhep-phnucl-exPoS(2015)·23 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.