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Register a new userSearch for $eta$ and $eta^primeto pi^+ e^- bar{ u}_e +c.c.$ decays in $jpsi to phi eta$ and $phi eta^prime$
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Using a sample of 225.3 million $jpsi$ events collected with the BESIII detector at the BEPCII $e^+e^-$ collider in 2009, searches for the decays of $eta$ and $eta^primetopi^+ e^- bar{ u}_e +c.c.$ in $jpsi to phi eta$ and $phieta^prime$ are performed. The $phi$ signals, which are reconstructed in $K^+K^-$ final states, are used to tag $eta$ and $eta^prime$ semileptonic decays. No signals are observed for either $eta$ or $eta^prime$, and upper limits at the 90% confidence level are determined to be $7.3times 10^{-4}$ and $5.0times 10^{-4}$ for the ratios $frac{{mathcal B}(etato pi^+ e^- bar{ u}_e +c.c.)}{{mathcal B}(eta to pippimpiz)}$ and $frac{{mathcal B}(eta^primeto pi^+ e^-bar{ u}_e +c.c.)}{{mathcal B}(eta^prime to pippimeta)}$, respectively. These are the first upper limit values determined for $eta$ and $eta^prime$ semileptonic weak decays.
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We report the first observation of the decay D^+ -> eta e^+ nu_e in two analyses, which combined provide a branching fraction of B(D+ -> eta e nu) = (2.16 +/- 0.53 +/- 0.07) x 10^{-4}. We also provide an improved measurement of B(D+ -> eta e nu) = (11.4 +/- 0.9 +/- 0.4) x 10^{-4}, provide the first form factor measurement, and set the improved upper limit B(D+ -> phi e nu) < 0.9 x 10^{-4} (90% C.L.).
A search for the $C!P$-violating strong decays $eta to pi^+pi^-$ and $eta^prime(958) to pi^+pi^-$ has been performed using approximately $2.5 times 10^{7}$ events of each of the decays $D^+ to pi^+pi^+pi^-$ and $D_s^+ to pi^+pi^+pi^-$, recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0 fb$^{-1}$ of $pp$ collision data recorded during LHC Run 1 and 0.3 fb$^{-1}$ recorded in Run 2. No evidence is seen for $D^+_{(s)} to pi^+ eta^{(prime)}$ with $eta^{(prime)} to pi^+pi^-$, and upper limits at 90% confidence level are set on the branching fractions, $mathcal{B}(eta to pi^+pi^-) < 1.6 times 10^{-5}$ and $mathcal{B}(eta^prime to pi^+pi^-) < 1.8 times 10^{-5}$. The limit for the $eta$ decay is comparable with the existing one, while that for the $eta^prime$ is a factor of three smaller than the previous limit.
A search for the charmless $B^{0}_{s} to eta^{prime}phi$ decay is performed using $pp$ collision data collected by the LHCb experiment at centre-of-mass energies of $7$ and $8$ TeV, corresponding to an integrated luminosity of 3 fb$^{-1}$. No signal is observed and upper limits on the $B^{0}_{s} to eta^{prime}phi$ branching fraction are set to $0.82times 10^{-6}$ at $90%$ and $1.01times 10^{-6}$ at $95%$ confidence level.
A search for the rare decay $eta^{prime} to e^+e^-$ has been performed with the SND detector at the VEPP-2000 $e^+e^-$ collider. The inverse reaction $e^+e^- to eta^{prime}$ and $eta^{prime}$ five decay chains have been used for this search. The upper limit $Gamma_{eta^{prime} to e^+e^-}<0.002$ eV at the 90% confidence level has been set. A sensitivity of SND in a search for $eta to e^+e^-$ decay has been studied. For this perpose we have analyzed a data sample with an integrated luminosity of 108 nb$^{-1}$ collected in the center-of-mass energy range 520-580 MeV. There are no background events for the reaction $e^+e^- to eta$ with decay $eta to pi^0pi^0pi^0$ have been found. In the absence of background, a sensitivity to $B(eta to e^+e^-)$ of 10$^{-6}$ can be reached during two weeks of VEPP-2000 operation.
The hadronic decays eta, eta-prime -> 3 pi and eta-prime -> eta pi pi are investigated within the framework of U(3) chiral effective field theory in combination with a relativistic coupled-channels approach. Final state interactions are included by deriving s- and p-wave interaction kernels for meson-meson scattering from the chiral effective Lagrangian and iterating them in a Bethe-Salpeter equation. Very good overall agreement with currently available data on decay widths and spectral shapes is achieved.
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