Commensurate lock-in and incommensurate supersolid phases of hardcore bosons on anisotropic triangular lattices

We investigate the interplay between commensurate lock-in and incommensurate supersolid phases of the hardcore bosons at half-filling with anisotropic nearest-neighbor hopping and repulsive interactions on triangular lattice. We use numerical quantum and variational Monte Carlo as well as analytical Schwinger boson mean-field analysis to establish the ground states and phase diagram. It is shown that, for finite size systems, there exist a series of jumps between different supersolid phases as the anisotropy parameter is changed. The density ordering wavevectors are locked to commensurate values and jump between adjacent supersolids. In the thermodynamic limit, however, the magnitude of these jumps vanishes leading to a continuous set of novel incommensurate supersoild phases.Comment: 5 pages, 5 figures, added new results, changed title and conclusio

Search for rare decays of Z and Higgs bosons to J/ψ/\psi and a photon in proton-proton collisions at s=\sqrt{s} = 13 TeV

A search is presented for decays of $\mathrm {Z}$ and Higgs bosons to a ${\mathrm {J}/\psi }$ meson and a photon, with the subsequent decay of the ${\mathrm {J}/\psi }$ to $\mathrm {\mu ^+}\mathrm {\mu ^-}$ . The analysis uses data from proton-proton collisions with an integrated luminosity of 35.9 $\,\text {fb}^{-1}$ at $\sqrt{s}=13\,\text {TeV}$ collected with the CMS detector at the LHC. The observed limit on the $\mathrm {Z}\rightarrow {\mathrm {J}/\psi } \gamma$ decay branching fraction, assuming that the ${\mathrm {J}/\psi }$ meson is produced unpolarized, is $1.4\times 10^{-6}$ at 95% confidence level, which corresponds to a rate higher than expected in the standard model by a factor of 15. For extreme-polarization scenarios, the observed limit changes from $-13.6$ to $+8.6\%$ with respect to the unpolarized scenario. The observed upper limit on the branching fraction for $\mathrm {H} \rightarrow {\mathrm {J}/\psi } \gamma$ where the ${\mathrm {J}/\psi }$ meson is assumed to be transversely polarized is $7.6\times 10^{-4}$ , a factor of 260 larger than the standard model prediction. The results for the Higgs boson are combined with previous data from proton-proton collisions at $\sqrt{s}=8\,\text {TeV}$ to produce an observed upper limit on the branching fraction for $\mathrm {H} \rightarrow {\mathrm {J}/\psi } \gamma$ that is a factor of 220 larger than the standard model value