Fri·Jul 3, 2015Friday·July 3, 2015

1. 01*

   First measurement of the helicity asymmetry $E$ in $\eta$ photoproduction on the proton

   I. Senderovich · B.T. Morrison · M. Dugger · B.G. Ritchie · E. Pasyuk · R. Tucker · J. Brock · C. Carlin · C.D. Keith · D.G. Meekins · M.L. Seely · D. R and 139 other authors

   Results are presented for the first measurement of the double-polarization helicity asymmetry E for the $\eta$ photoproduction reaction $\gamma p\to \eta p$. Data were obtained using the FROzen Spin Target (FROST) with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of center-of-mass energy W from threshold to 2.15 GeV and a large range in center-of-mass polar angle. As an initial application of these data, the results have been incorporated into the Jülich model to examine the case for the existence of a narrow $N^{\ast }$ resonance between 1.66 and 1.70 GeV. The addition of these data to the world database results in marked changes in the predictions for the E observable using that model. Further comparison with several theoretical approaches indicates these data will significantly enhance our understanding of nucleon resonances.

   nucl-exPLB(2016)·48 citations
2. 02*

   Low Q^2 Weak Mixing Angle Measurements and Rare Higgs Decays

   Hooman Davoudiasl🇺🇸 · Hye-Sung Lee🇨🇭 · William J. Marciano🇺🇸

   A weighted average weak mixing angle theta_W derived from relatively low Q^2 experiments is compared with the Standard Model prediction obtained from precision measurements. The approximate 1.8 sigma discrepancy is fit with an intermediate mass (~ 10-35 GeV) "dark" Z boson Z_d, corresponding to a U(1)_d gauge symmetry of hidden dark matter, which couples to our world via kinetic and Z-Z_d mass mixing. Constraints on such a scenario are obtained from precision electroweak bounds and searches for the rare Higgs decays H -> Z Z_d -> 4 charged leptons at the LHC. The sensitivity of future anticipated low Q^2 measurements of sin^2 theta_W(Q^2) to intermediate mass Z_d is also illustrated. This dark Z scenario can provide interesting concomitant signals in low energy parity violating measurements and rare Higgs decays at the LHC, over the next few years.

   ↳ hep-phhep-exnucl-exPRD(2015)·62 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.