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Register a new userUsing kaon regeneration to probe the quark mixing parameter cos(2 beta) in B --> psi K decays
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We suggest a novel method to determine the sign of cos(2 beta) in the decays B --> psi K, by creating interference between KL and KS final states via ``regeneration, that is propagation through a matter target region to convert some KL to KS. The determination of this quantity resolves an ambiguity between beta and (90o - beta) that remains after the standard measurements of sin(2 beta) and may turn out to be important in resolving whether the result is in agreement with Standard Model predictions or indicates the presence of new physics. We find the measurement is feasible at a B-factory, but requires several years of high-luminosity running with a regeneration target affecting a significant fraction of the detector.
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We demonstrate that dispersion theory allows one to deduce crucial information on $pieta$ scattering from the final-state interactions of the light mesons visible in the spectral distributions of the decays $bar{B}^0_d to J/psi(pi^0eta,K^+K^-,K^0bar{K}^0)$. Thus high-quality measurements of these differential observables are highly desired. The corresponding rates are predicted to be of the same order of magnitude as those for $bar{B}^0_d to J/psipi^+pi^-$ measured recently at LHCb, letting the corresponding measurement appear feasible.
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A lattice QCD calculation of the kaon $B$ parameter $B_K$ is carried out with the Wilson quark action in the quenched approximation at $beta=6/g^2=5.9-6.5$. The mixing problem of the $Delta s=2$ four-quark operators is solved non-perturbatively with full use of chiral Ward identities employing four external quarks with an equal off-shell momentum in the Landau gauge. This method, without invoking any effective theory, enables us to construct the weak four-quark operators exhibiting good chiral behavior. Our results for $B_K$ with the non-perturbative mixing coefficients show small scaling violation beyond the lattice cut-off $a^{-1}sim 2.5 $GeV. Our estimate concludes $B_K(NDR, 2 GeV)=0.69(7)$ at $a^{-1}=2.7-4.3$GeV, which agrees with the value obtained with the Kogut-Susskind quark action. For comparison we also calculate $B_K$ with one-loop perturbative mixing coefficients. While this yields incorrect values at finite lattice spacing, a linear extrapolation to the continuum limit as a function of $a$ leads to a result consistent with those obtained with the Ward identity method.
We present a detailed description of the method and results of our calculation of the kaon B parameter using the Wilson quark action in quenched QCD at $beta=5.9-6.5$. The mixing problem of the $Delta s=2$ four-quark operators is solved non-perturbatively with full use of chiral Ward identities. We find $B_K(NDR, 2 GeV)=0.562(64)$ in the continuum limit, which agrees with the value obtained with the Kogut-Susskind quark action.
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.
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