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Register a new userDetermining the photon polarization of the b --> s gamma using the B --> K1(1270) gamma --> (K pi pi) gamma decay
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Recently the radiative B decay to the strange axial-vector mesons, B --> K1(1270) gamma, has been observed with rather large branching ratio. This process is particularly interesting as the subsequent K1 decay into its three body final state allows us to determine the polarization of the photon, which is mostly left- (right-)handed for Bbar (B) in the SM while various new physics models predict additional right- (left-)handed components. A new method is proposed to determine the polarization, exploiting the full Dalitz plot distribution, which seems to reduce significantly the statistical errors. This polarization measurement requires however a detailed knowledge of the K1--> K pi pi strong interaction decays, namely, the various partial wave amplitudes into the several possible quasi two-body channels, as well as their relative phases. The pattern of partial waves is especially complex for the K1(1270). We attempt to obtain the information through the combination of an experimental input and a theoretical one, provided by the 3P0 quark-pair-creation model.
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The first observation of the decay K^+ --> pi^+ gamma gamma is reported. A total of 31 events was observed with an estimated background of 5.1 +- 3.3 events in the pi+ momentum range from 100 MeV/c to 180 MeV/c. The corresponding partial branching ratio, B(K+ -> pi+ gamma gamma, 100 MeV/c < P_pi^+ < 180 MeV/c), is (6.0 +- 1.5 (stat) +- 0.7 (sys)) x 10^{-7}. No K^+ --> pi^+ gamma gamma decay was observed in the pi^+ momentum region greater than 215 MeV/c. The observed pi^+ momentum spectrum is compared with the predictions of chiral perturbation theory.
We investigate the rare radiative eta decay modes eta -> pi+ pi- gamma gamma and eta -> pi0 pi0 gamma gamma within the framework of chiral lagrangians at o(p^4) and present photon spectra for both processes.
In this work we compute the leading logarithmic corrections to the b -> s gamma decay in a dimensional scheme which does not require any definition of the gamma5 matrix. The scheme does not exhibit unconsistencies and it is therefore a viable alternative to the tHooft Veltman scheme, particularly in view of the next-to-leading computation. We confirm the recent results of Ciuchini et al.
A new and simple procedure to measure the angle $gamma$ from $B^{pm} to pi^{pm}pi^+pi^-$ and $B^{pm} to K^{pm}pi^+pi^-$ decays using SU(3) symmetry is presented. It is based on a full Dalitz plot analysis of these decays. All diagrams, including strong and electroweak penguins, are considered in the procedure. The method is also free from final state interaction problems. The theoretical error in the extraction of $gamma$ within the method should be of the order of $10^{rm o}$ or even less. Taking into account the B-meson production in the first generation of B factories and recent measurements from CLEO, this method could bring the best measurement of $gamma$ in the next years.
Within the quasi-two-body decay model, we study the localized $CP$ violation and branching fraction of the four-body decay $bar{B}^0rightarrow [K^-pi^+]_{S/V}[pi^+pi^-]_{V/S} rightarrow K^-pi^+pi^-pi^+$ when $K^-pi^+$ and $pi^-pi^+$ pair invariant masses are $0.35<m_{K^-pi^+}<2.04 , mathrm{GeV}$ and $0<m_{pi^-pi^+}<1.06, mathrm{GeV}$, with the pairs being dominated by the $bar{K}^*_0(700)^0$, $bar{K}^*(892)^0$, $bar{K}^*(1410)^0$, $bar{K}^*_0(1430)$ and $bar{K}^*(1680)^0$, and $f_0(500)$, $rho^0(770)$ , $omega(782)$ and $f_0(980)$ resonances, respectively. When dealing with the dynamical functions of these resonances, $f_0(500)$, $rho^0(770)$, $f_0(980)$ and $bar{K}^*_0(1430)$ are modeled with the Bugg model, Gounaris-Sakurai function, Flatt$acute{mathrm{e}}$ formalism and LASS lineshape, respectively, while others are described by the relativistic Breit-Wigner function. Adopting the end point divergence parameters $rho_Ain[0,0.5]$ and $phi_Ain[0,2pi]$, our predicted results are $mathcal{A_{CP}}(bar{B}^0rightarrow K^-pi^+pi^+pi^-)in[-0.383,0.421]$ and $mathcal{B}(bar{B}^0rightarrow K^-pi^+pi^+pi^-)in[7.36,199.69]times10^{-8}$ based on the hypothetical $qbar{q}$ structures for the scalar mesons in the QCD factorization approach. Meanwhile, we calculate the $CP$ violating asymmetries and branching fractions of the two-body decays $bar{B}^0rightarrow SV(VS)$ and all the individual four-body decays $bar{B}^0rightarrow SV(VS) rightarrow K^-pi^+pi^-pi^+$, respectively. Our theoretical results for the two-body decays $bar{B}^0rightarrow bar{K}^*(892)^0$$f_0(980)$, $bar{B}^0rightarrow bar{K}^*_0(1430)^0$$omega(782)$, $bar{B}^0rightarrow bar{K}^*(892)^0f_0(980)$, $bar{B}^0rightarrowbar{K}^*_0(1430)^0rho$,
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