Collinear improvement of the BFKL kernel in the electroproduction of two light vector mesonsCaporale, F.;Papa, A.;Vera, A. Sabio
doi: 10.1140/epjc/s10052-007-0481-6pmid: N/A
Abstract The use of the BFKL kernel improved by the inclusion of subleading terms generated by renormalization group (RG) analysis has been suggested to cure the instabilities in the behavior of the BFKL Green’s function in the next-to-leading approximation (NLA). We test the performance of a RG-improved kernel in the determination of the amplitude of a physical process, the electroproduction of two light vector mesons, in the BFKL approach in the NLA. We find that a smooth behavior of the amplitude with the center-of-mass energy can be achieved, setting the renormalization and energy scales appearing in the subleading terms to values much closer to the kinematical scales of the process than in the approaches based on the unimproved kernel.
Electromagnetic low-energy constants in χPTHaefeli, C.;Ivanov, M.A.;Schmid, M.
doi: 10.1140/epjc/s10052-007-0493-2pmid: N/A
Abstract We investigate three-flavour chiral perturbation theory including virtual photons in the limit in which the strange quark mass is much larger than the external momenta and the up and down quark masses, and where the external fields are those of two-flavour chiral perturbation theory. In particular, we work out the strange quark mass dependence of the electromagnetic two-flavour low-energy constants C and ki. We expect that these relations will be useful for a more precise determination of the electromagnetic low-energy constants.
Corrections to the generalized vector dominance due to diffractive ρ 3 productionIvanov, I.P.;Pacetti, S.
doi: 10.1140/epjc/s10052-007-0488-zpmid: N/A
Abstract The idea of the vector dominance is still in use in various analyses of the experimental data of photon–hadron reactions. It makes sense, therefore, to recast results of microscopic calculations of such reactions in this language. Here we present the diffractive DIS ρ3 production as a specific correction to generalized vector dominance. We perform a coupled channel analysis of spin–orbital excitations in diffractive photoproduction and reiterate the point that ρ3 in diffractive DIS will be sensitive to a novel aspect of diffraction.
Soft-photon corrections in multi-body meson decaysIsidori, G.
doi: 10.1140/epjc/s10052-007-0487-0pmid: N/A
Abstract The effects due to soft-photon emission (and the related virtual corrections) in multi-body decays of B, D, and K mesons are analyzed. We present analytic expressions for the universal \(\mathcal{O}(\alpha)\) correction factors which can be applied to all multi-body decay modes where a tight soft-photon energy cut in the decaying-particle rest frame is applied. All-order resummations valid in the limit of small and large velocities of the final-state particles are also discussed. The phenomenological implications of these correction factors in the distortion of Dalitz plot distributions of K→3π decays are briefly analyzed.
Field-theoretical approach to particle oscillations in absorbing matterNazaruk, V.I.
doi: 10.1140/epjc/s10052-007-0473-6pmid: N/A
Abstract The ab oscillations in absorbing matter are considered. The standard model based on an optical potential does not describe the total ab transition probability as well as the channel corresponding to absorption of the b-particle. We calculate directly the off-diagonal matrix element in the framework of the field-theoretical approach. Contrary to the one-particle model, the final-state absorption does not tend to suppress the channels mentioned above; or, similarly, calculation with a Hermitian Hamiltonian leads to an increase of the corresponding values. Our approach reproduces all the results on the particle oscillations; however, it is oriented to the description of the above-mentioned channels. Also we touch on the general problems of the theory of reactions and decays; in particular, on infrared divergences. The approach in our study is infrared-free. For the correct construction and verification of the models of complicated processes, we propose the use of the low-density limit for the intermediate-state particle.
Neutrino hierarchy from CP-blind observables with high density magnetized detectorsDonini, A.;Fernandez-Martinez, E.;Migliozzi, P.;Rigolin, S.;Lavina, L. Scotto;Selvi, M.;de Fatis, T. Tabarelli;Terranova, F.
doi: 10.1140/epjc/s10052-007-0489-ypmid: N/A
Abstract High density magnetized detectors are well suited to exploit the outstanding purity and intensities of novel neutrino sources like neutrino factories and beta beams. They can also provide independent measurements of leptonic mixing parameters through the observation of atmospheric muon-neutrinos. In this paper, we discuss the combination of these observables from a multi-kT iron detector and a high energy beta beam; in particular, we demonstrate that even with moderate detector granularities the neutrino mass hierarchy can be determined for θ13 values greater than 4°.
Spontaneous CP violating phase as the CKM matrix phaseChen, Shao-Long;Deshpande, N.G.;He, Xiao-Gang;Jiang, Jing;Tsai, Lu-Hsing
doi: 10.1140/epjc/s10052-007-0509-ypmid: N/A
Abstract We propose that the CP violating phase in the CKM mixing matrix is identical to the CP phases responsible for the spontaneous CP violation in the Higgs potential. A multi-Higgs model with Peccei–Quinn (PQ) symmetry is constructed to realize this idea. The CP violating phase does not vanish when all Higgs masses become large. In general, here are flavor changing neutral current (FCNC) interactions mediated by neutral Higgs bosons at the tree level. However, unlike general multi-Higgs models, the FCNC Yukawa couplings are fixed in terms of the quark masses and CKM mixing angles. Implications for meson–anti-meson mixing, including recent data on D–D̄ mixing, and the electric dipole moment (EDM) of the neutron are studied. We find that the neutral Higgs boson masses can be at the order of one hundred GeV. The neutron EDM can be close to the present experimental upper bound.