Wed·May 11, 2016Wednesday·May 11, 2016

1. 01*

   Search for Majorana Neutrinos near the Inverted Mass Hierarchy Region with KamLAND-Zen

   KamLAND-Zen Collaboration

   We present an improved search for neutrinoless double-beta ($0\nu \beta \beta$) decay of ${}^{136}$Xe in the KamLAND-Zen experiment. Owing to purification of the xenon-loaded liquid scintillator, we achieved a significant reduction of the ${}^{110m}$Ag contaminant identified in previous searches. Combining the results from the first and second phase, we obtain a lower limit for the $0\nu \beta \beta$ decay half-life of $T_{1/2}^{0\nu }>1.07\times 10^{26}$ yr at 90% C.L., an almost sixfold improvement over previous limits. Using commonly adopted nuclear matrix element calculations, the corresponding upper limits on the effective Majorana neutrino mass are in the range 61-165 meV. For the most optimistic nuclear matrix elements, this limit reaches the bottom of the quasi-degenerate neutrino mass region.

   ↳ hep-exnucl-exphysics.ins-detPRL(2016)·1336 citations
2. 02*

   Complete Study of Hadroproduction of a ${\rm Y}$ Meson Associated with a Prompt $J/\psi$

   Hua-Sheng Shao🇨🇭 · Yu-Jie Zhang🇨🇳

   We present the first complete study of ${\rm Y}$ and prompt $J/\psi$ production from single-parton scattering, including the complete $\mathcal{O}({\alpha }_S^6)$ color-singlet contribution, the $\mathcal{O}({\alpha }_S^2{\alpha }^2)$ electroweak contribution, the complete nonrelativistic S-wave and P-wave color-octet contribution as well as the feeddown contribution. Our study was motivated by the recent evidence reported by D0 Collaboration of prompt $J/\psi$ and ${\rm Y}$ simultaneous production at the Tevatron. With our complete evaluation, we are able to refine the determination of the double parton scattering contribution made by D0 Collaboration. We find that the effective cross section characterizing the importance of double-parton scatterings is ${\sigma }_{\mathrm{eff}}\le 8.2$ mb at $68\%$ confidence level from the D0 measurement.

   ↳ hep-phhep-exnucl-exnucl-thPRL(2016)·45 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.