Related papers: Unitarity and vector meson contributions to K^+ ->…
We present a semi-recursive method for calculating the rational parts of one-loop gravity amplitudes which utilises axial gauge diagrams to determine the non-factorising pieces of the amplitude. This method is used to compute the one-loop…
We calculate the important next-to-leading-order contributions to the B -> pi K, pi pi decays from the vertex corrections, the quark loops, and the magnetic penguins in the perturbative QCD approach. It is found that the latter two reduce…
It is well known that in low energy supersymmetry the ratio of the gaugino mass to the gauge coupling squared, M/alpha, is renormalization group invariant to one-loop. We present a systematic analysis of the corrections to this ratio,…
Recent studies based on unitary chiral perturbation theory (U$\chi$PT) found that the low-lying axial vector mesons can be dynamically generated due to the interaction of the pseudoscalar octet of the pion and the vector nonet of the rho.…
The newly introduced Transition Distribution Amplitudes (TDAs) are discussed for the $\pi$-$\gamma$ transitions. Relations between $\pi$-$\gamma$ and $\gamma$-$\pi$ TDAs for different cases are given. Numerical values for the $\pi$-$\gamma$…
Radiative corrections to the $h\rightarrow Z\gamma$ are evaluated in the one-loop approximation. The unitary gauge gauge is used. The analytic result is expressed in terms of the Passarino-Veltman functions. The calculations are applicable…
We calculate full one-loop corrections to the genuine three-body decays of the light chargino \chi_1^\pm to \chi^0_1 l^\pm \nu in the Minimal Supersymmetric Standard Model. We find that the corrections to the decay width can be of the order…
We present the one-loop helicity amplitudes for processes involving a vector boson V (V=W,Z, or gamma^*) and four massless quarks, 0 to V q-bar q Q-bar Q, where V couples to a massless lepton pair. These amplitudes are required for…
In view of future plans for accurate measurements of the theoretically clean branching ratios Br(K+ -> pi+ nu nu) and Br(KL -> pi0 nu nu), that should take place in the next decade, we collect the relevant formulae for quantities of…
We derive factorization relations for the transverse helicity amplitudes in the rare decays B-> K\pi l+l- at leading order in Lambda/m_b, in the kinematical region with an energetic kaon and a soft pion. We identify and compute a new…
We calculate the ratios $R_{\tau / P}\equiv \Gamma \left( \tau \to P \nu_{\tau}[\gamma] \right) / \Gamma \left(P\to \mu \nu_{\mu}[\gamma]\right)$ ($P=\pi,K$) at one loop following a large-$N_C$ expansion where Chiral Perturbation Theory is…
Lattice QCD studies of hadron-hadron interactions are performed by computing the energy levels of the system in a finite box. The shifts in energy levels proportional to inverse powers of the volume are related to scattering parameters in a…
A representation of the amplitude $\gamma^*(q^2)\to\gamma\pi\pi$ is proposed which combines large $N_c$ chiral resonance Lagrangian modelling with general unitarity and analyticity properties. The amplitude is constrained from…
We present a calculation of the $C$-odd radiative corrections to $e^+e^-\to \pi^+\pi^-$ in a dispersive formalism, concentrating on the leading pion-pole contribution in the virtual box diagrams. In particular, we show how the effect of a…
We calculate O(alpha_s) two-loop virtual corrections to the differential decay width dGamma(B --> X_s l^+ l^-)/ds, where s is the invariant mass squared of the lepton pair. We also include those contributions from gluon bremsstrahlung which…
We show the results for the scattering poles associated to the rho, f0, a0, K*, sigma and kappa resonances in meson-meson scattering. Our amplitudes are obtained from the complete one-loop meson-meson scattering amplitudes from Chiral…
The contribution of the a_1(1260) meson to the amplitudes of the decays rho(770) to 4 pi, omega(782) to 5 pi, and phi(1020) to 5 pi is analyzed in the chiral model of pseudoscalar, vector, and axial vector mesons based on the generalized…
A new unitarization approach is discussed and applied to study the elastic $\pi K$ scattering process. The existence of the light $\kappa$ resonance is firmly established if the scattering length in the I=1/2 channel does not deviate too…
Around $\theta_{\pi}= 90^\circ$, the coupling to the $\rho^\circ N$ channel leads to a good accounting of the charged pion exclusive photoproduction cross section in the energy range 3 $<E_{\gamma}<$ 10 GeV, where experimental data exist.…
We analyse the perturbative contributions from the higher helicity ($\lambda_{1}+\lambda_{1}=\pm 1$) components, which should be naturally contained in the light-cone wave function for the pion as a consequence of the Wigner rotation, in…