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Register a new userContribution of low-lying vector resonances to polarization observables in bar B_d^0 -> bar K*0 e+ e- decay
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The branching ratio and other observables for the rare flavour-changing neutral current decay bar B_d^0 -> bar K*0 (-> K- pi+) e+ e- are studied below the bar{c} c threshold. The total amplitude for this decay includes the term coming from the standard model effective Hamiltonian and the term generated by the processes bar B_d^0 -> bar K*0 (-> K- pi+) V with intermediate low-lying vector resonances V = rho(770), omega(782), phi(1020) decaying into the e+ e- pair. The resonance contribution to the branching ratio, polarization fractions of the K* meson and coefficients in the angular distribution is calculated. The influence of the resonances on the integrated observables in the region of electron-positron invariant mass up to 1 GeV is studied in view of the planned measurements of the photon polarization at the LHCb.
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Motivated by the experimental measurements of $D^0$ radiative decay modes we have proposed a model to study the $D^0to bar{K}^{*0}gamma$ decay, by establishing a link with $D^0to bar{K}^{*0}V$ $(V=rho^0,, omega)$ decays through the vector meson dominance hypothesis. In order to do this properly, we have used the Lagrangians from the local hidden gauge symmetry approach to account for $Vgamma$ conversion. As a result, we have found the branching ratio $mathcal{B}[D^0to bar{K}^{*0}gamma] =(1.55 - 3.44)times 10^{-4}$, which is in fair agreement with the experimental values reported by Belle and Babar collaborations.
We observe $D^0-bar{D}^0$ mixing in the decay $D^0rightarrow K^+pi^-$ using a data sample of integrated luminosity 976 fb$^{-1}$ collected with the Belle detector at the KEKB $e^+e^-$ asymmetric-energy collider. We measure the mixing parameters ${x}^2 = (0.09pm0.22)times 10^{-3}$ and $y = (4.6pm3.4)times 10^{-3}$ and the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates $R_D = (3.53pm0.13)times 10^{-3}$, where the uncertainties are statistical and systematic combined. Our measurement excludes the no-mixing hypothesis at the 5.1 standard deviation level.
We study the decay processes of $bar{B}^0 to J/psi bar{K}^{*0} K^0$ and $bar{B}^0 to J/psi f_1(1285)$ to analyse the $f_1(1285)$ resonance. By the calculation within chiral unitary approach where $f_1(1285)$ resonance is dynamically generated from the $K^*bar{K}-c.c.$ interaction, we find that the $bar{K}^{*0} K^0$ invariant mass distribution has a clear broad peak. Such broad peak has been understood as the signal of the $f_1(1285)$. Finally, we obtain a theoretical result $R_t=Gamma_{bar{B}^0 to J/psi bar{K}^{*0} K^0}/Gamma_{bar{B}^0 to J/psi f_1(1285)}$ which is expected to be compared with the experimental data.
We report a study of the process $e^{+} e^{-} to (D^{*} bar{D}^{*})^{0} pi^0$ using $e^+e^-$ collision data samples with integrated luminosities of $1092 rm{pb}^{-1}$ at $sqrt{s}=4.23 rm{GeV}$ and $826 rm{pb}^{-1}$ at $sqrt{s}=4.26 rm{GeV}$ collected with the BESIII detector at the BEPCII storage ring. We observe a new neutral structure near the $(D^{*} bar{D}^{*})^{0}$ mass threshold in the $pi^0$ recoil mass spectrum, which we denote as $Z_{c}(4025)^{0}$. Assuming a Breit-Wigner line shape, its pole mass and pole width are determined to be $(4025.5^{+2.0}_{-4.7}pm3.1) rm{MeV}/c^2$ and $(23.0pm 6.0pm 1.0) rm{MeV}$, respectively. The Born cross sections of $e^{+}e^{-}to Z_{c}(4025)^{0} pi^0to (D^{*} bar{D}^{*})^{0}pi^0$ are measured to be $(61.6pm8.2pm9.0) rm{pb}$ at $sqrt{s}=4.23 rm{GeV}$ and $(43.4pm8.0pm5.4) rm{pb}$ at $sqrt{s}=4.26 rm{GeV}$. The first uncertainties are statistical and the second are systematic.
By analyzing 2.93 fb$^{-1}$ data collected at the center-of-mass energy $sqrt s=3.773$ GeV with the BESIII detector, we measure the absolute branching fraction of the semileptonic decay $D^+rightarrowbar K^0 e^{+} u_{e}$ to be ${mathcal B}(D^{+}rightarrowbar K^0 e^{+} u_{e})=(8.59 pm 0.14 pm 0.21)%$ using $bar K^0to K^0_Sto pi^0pi^0$, where the first uncertainty is statistical and the second systematic. Our result is consistent with previous measurements within uncertainties.
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