ﻻ يوجد ملخص باللغة العربية
We present a new determination of the parity of the neutral pion via the double Dalitz decay pi^0 -> e+ e- e+ e-. Our sample, which consists of 30511 candidate decays, was collected from K_L -> pi0 pi0 pi0 decays in flight at the KTeV-E799 experiment at Fermi National Accelerator Laboratory. We confirm the negative pi^0 parity, and place a limit on scalar contributions to the pi^0 -> e+ e- e+ e- decay amplitude of less than 3.3% assuming CPT conservation. The pi^0 gamma* gamma* form factor is well described by a momentum-dependent model with a slope parameter fit to the final state phase space distribution. Additionally, we have measured the branching ratio of this mode to be B(pi^0 -> e+ e- e+ e-) = (3.26 +- 0.18) x 10^(-5).
The spin and parity of the $Z_c(3900)^pm$ state are determined to be $J^P=1^+$ with a statistical significance larger than $7sigma$ over other quantum numbers in a partial wave analysis of the process $e^+e^-to pi^+pi^-J/psi$. We use a data sample of
Using a $3.19~mathrm{fb}^{-1}$ data sample collected at an $e^+e^-$ center-of-mass energy of $E_{rm cm}=4.178$ GeV with the BESIII detector, we measure the branching fraction of the leptonic decay $D_s^+tomu^+ u_mu$ to be $mathcal{B}_{D_s^+tomu^+ u_m
The interference between the K+K- S-wave and P-wave amplitudes in B_s -> J/psi K+K- decays with the K+K- pairs in the region around the phi(1020) resonance is used to determine the variation of the difference of the strong phase between these amplitu
The E815 (NuTeV) neutrino experiment has performed a search for a 33.9 MeV/c^2 weakly-interacting neutral particle produced in pion decay. Such a particle may be responsible for an anomaly in the timing distribution of neutrino interactions in the KA
We report a precision measurement of the parity-violating asymmetry $A_{PV}$ in the elastic scattering of longitudinally polarized electrons from $^{208}$Pb. We measure $A_{PV}=550pm 16 {rm (stat)}pm 8 {rm (syst)}$ parts per billion, leading to an ex