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Register a new userPositron-neutrino correlation in the 0^+ to 0^+ decay of ^{32}Ar
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The positron-neutrino correlation in the $0^+ to 0^+ beta$ decay of $^{32}$Ar was measured at ISOLDE by analyzing the effect of lepton recoil on the shape of the narrow proton group following the superallowed decay. Our result is consistent with the Standard Model prediction. For vanishing Fierz interference we find $a=0.9989 pm 0.0052 pm 0.0036$, which yields improved constraints on scalar weak interactions.
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We present the results of a Dalitz plot analysis of D^0 to K^0_S pi^0 pi^0 using the CLEO-c data set of 818 inverse pico-barns of e^+ e^- collisions accumulated at sqrt{s} = 3.77 GeV. This corresponds to three million D^0 D^0-bar pairs from which we select 1,259 tagged candidates with a background of 7.5 +- 0.9 percent. Several models have been explored, all of which include the K^*(892), K^*_2(1430), K^*(1680), the f_0(980), and the sigma(500). We find that the combined pi^0 pi^0 S-wave contribution to our preferred fit is (28.9 +- 6.3 +- 3.1)% of the total decay rate while D^0 to K^*(892)^0 pi^0 contributes (65.6 +- 5.3 +- 2.5)%. Using three tag modes and correcting for quantum correlations we measure the D^0 to K^0_S pi^0 pi^0 branching fraction to be (1.059 +- 0.038 +- 0.061)%.
A search for $B_s^0 to overline{D}^{0} f_{0}(980)$ decays is performed using $3.0, {rm fb}^{-1}$ of $pp$ collision data recorded by the LHCb experiment during 2011 and 2012. The $f_{0}(980)$ meson is reconstructed through its decay to the $pi^{+}pi^{-}$ final state in the mass window $900, {rm MeV}/c^{2} < m(pi^{+}pi^{-}) < 1080, {rm MeV}/c^{2}$. No significant signal is observed. The first upper limits on the branching fraction of $mathcal{B}(B_s^0 to overline{D}^{0} f_{0}(980)) < 3.1,(3.4) times 10^{-6}$ are set at $90,%$ ($95,%$) confidence level.
We report first time measurements of the beta-neutrino angular correlation based on the kinetic energy shift of protons emitted in parallel or anti-parallel directions with respect to the positron in the beta decay of $^{32}$Ar. This proof of principle experiment provided simultaneous measurements for the superallowed 0$^+$~$rightarrow$~0$^+$ transition followed by a 3356~keV proton emission and for a Gamow-Teller transition followed by a 2123~keV proton emission. The results, respectively ${tilde a_{beta u}}=1.01(3)_{(stat)}(2)_{(syst)}$ and ${tilde a_{beta u}}=-0.22(9)_{(stat)}(2)_{(syst)}$, are found in agreement with the Standard Model. A careful analysis of the data shows that future measurements can reach a precision level of 10$^{-3}$ for both pure Fermi and pure Gamow-Teller decay channels, providing new constraints on both scalar and tensor weak interactions.
We report a search for charmless hadronic decays of neutral $B$ mesons to $eta K^{*}(892)^{0}$. The results are based on a 711fb$^{-1}$ data sample that contains $772times 10^6 Boverline{B}$ pairs, collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^+e^-$ collider. We observe the decay for the first time with a significance of 5.0 standard deviations and obtain its branching fraction ${cal B}[B^0toeta K^{*}(892)^{0}]=[2.6pm0.7{rm (stat)}pm0.2{rm (syst)}]times 10^{-6}$. We also measure the $CP$ violating asymmetry as ${cal A}_{CP}[B^0toeta K^{*}(892)^{0}]=-0.22pm0.29{rm (stat)}pm0.07{rm syst}$.
Based on an $e^{+}e^{-}$ collision data sample corresponding to an integrated luminosity of 2.93 $mathrm{fb}^{-1}$ collected with the BESIII detector at $sqrt{s}=3.773 mathrm{GeV}$, the first amplitude analysis of the singly Cabibbo-suppressed decay $D^{+}to K^+ K_S^0 pi^0$ is performed. From the amplitude analysis, the $K^*(892)^+ K_S^0$ component is found to be dominant with a fraction of $(57.1pm2.6pm4.2)%$, where the first uncertainty is statistical and the second systematic. In combination with the absolute branching fraction $mathcal{B}(D^+to K^+ K_S^0 pi^0)$ measured by BESIII, we obtain $mathcal{B}(D^+to K^*(892)^+ K_S^0)=(8.69pm0.40pm0.64pm0.51)times10^{-3}$, where the third uncertainty is due to the branching fraction $mathcal{B}(D^+to K^+ K_S^0 pi^0)$. The precision of this result is significantly improved compared to the previous measurement.
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