The inferred value of the relic density from cosmological observations has reached a precision that is akin to that of the LEP precision measurements. This level of precision calls for the evaluation of the annihilation cross sections of dark matter
that goes beyond tree-level calculations as currently implemented in all codes for the computation of the relic density. In supersymmetry radiative corrections are known to be large and thus must be implemented. Full one-loop radiative corrections for many annihilation processes have been performed. It is important to investigate whether the bulk of these corrections can be parameterised through an improved Born approximation that can be implemented as a selection of form factors to a tree-level code. This paper is a second in a series that addresses this issue. After having provided these form factors for the annihilation of the neutralinos into fermions, which cover the case of a bino-like LSP (Lightest Supersymmetric Particle), we turn our attention here to a higgsino-like dark matter candidate through its annihilation into $ZZ$. We also investigate the cases of a mixed LSP. In all cases we compare the performance of the form factor approach with the result of a full one-loop correction. We also study the issue of the renormalisation scheme dependence. An illustration of the phenomenon of non decoupling of the heavy sfermions that takes place for the annihilation of the lightest neutralino into $ZZ$ is also presented.
The $N to Delta$ weak vertex provides an important contribution to the one pion production in neutrino-nucleon and neutrino-nucleus scattering for $pi N$ invariant masses below 1.4 GeV. Beyond its interest as a tool in neutrino detection and their ba
ckground analyses, one pion production in neutrino-nucleon scattering is useful to test predictions based on the quark model and other internal symmetries of strong interactions. Here we try to establish a connection between two commonly used parametrizations of the weak $N to Delta$ vertex and form factors (FF) and we study their effects on the determination of the axial coupling $C_5^A(0)$, the common normalization of the axial FF, which is predicted to hold 1.2 by using the PCAC hypothesis. Predictions for the $ u_{mu} p to mu^- ppi^+$ total cross sections within the two approaches, which include the resonant $Delta^{++}$ and other background contributions in a coherent way, are compared to experimental data.
The neutrino-nucleon --> lepton pion QE reaction on the A-target is used as a signal event or/and to reconstruct the neutrino energy, using two-body kinematics. Competition of another processes could lead to misidentification of the arriving neutrino
s, being important the fake events coming from the CC1-pion background. A precise knowledge of cross sections is a prerequisite in order to make simulations in event generators to substract the fake ones from the QE countings, and in this contribution we analyze the different nuclear effects on the CC1-pion channel. Our calculations also can be extended for the NC case.
The quasielastic charged current (CCQE) $ u_e n rightarrow e^- p$ scattering is the dominant mechanism to detect appearance of a $ u_e$ in an almost $ u_mu$ flux at the 1 GeV scale. Actual experiments show a precision below 1% and between less known
background contributions, but necessary to constraint the event excess, we have the radiative corrections. A consistent model recently developed for the simultaneous description of elastic and radiative $pi N$ scattering, pion-photoproduction and single pion production processes, both for charged and neutral current neutrino-nucleon scattering, is extended for the evaluation of the radiative $ u_l Nrightarrow u_l N gamma$ cross section. Our results are similar to a previous (but inconsistent) theoretical evaluation in the low energy region, and show an increment in the upper region where the $Delta$ resonance becomes relevant.
