We consider Non-Standard neutrino Interactions (NSI), described by four-fermion operators of the form (ναγν β )(f γf ), where f is an electron or first generation quark. We assume these operators are generated at dimension ≥ 8, so the related vertices involving charged leptons, obtained by an SU (2) transformation ν δ → e δ , do not appear at tree level. These related vertices necessarily arise at one loop, via W exchange. We catalogue current constraints from sin 2 θW measurements in neutrino scattering, from atmospheric neutrino observations, from LEP, and from bounds on the related charged lepton operators. We estimate future bounds from comparing KamLAND and solar neutrino data, and from measuring sin 2 θW at the near detector of a neutrino factory. Operators constructed with νµ and νe should not confuse the determination of oscillation parameters at a νfactory, because the processes we consider are more sensitive than oscillations at the far detector. For operators involving ντ , we estimate similar sensitivities at the near and far detector. * Reference [9] found that NSI induced in the R-parity violating MSSM could not explain the solar neutrino deficit. However, their operators were otherwise constrained to be at least an order of magnitude smaller than the solutions found in [8].

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We analyze the viability of the Zee-Babu model as an explanation of observed neutrino masses and mixings and the possibility that the model is confirmed or discarded in experiments planned for the very close future. The allowed parameter space is studied analytically by using some approximations and partial data. Then, a complete scanning of all parameters and constraints is performed numerically by using Monte Carlo methods. The cleanest signal of the model will be the detection of the doubly charged scalar at the LHC and its correlation with measurements of the branching ratio of µ → eγ at the MEG experiment. In addition, the model offers interesting predictions for τ − → µ + µ − µ − experiments, lepton-hadron universality tests, the θ 13 mixing in neutrino oscillations and the m ν ee parameter of neutrinoless double beta decay.

We consider the most general dimension 5 effective Lagrangian that can be built using only Standard Model fields plus right-handed neutrinos, and find that there exists a term that provides electroweak moments (i.e., couplings to the 𝑍 and photon) for the right-handed neutrinos. Such term has not been described previously in the literature. We discuss its phenomenology and the bounds that can be derived from LEP results and from the observation of the cooling process of red giants and supernovae. MotivationNeutrino physics has been a hot topic of research and discussion in the last thirty years, and especially since we have compelling evidence that the structure of their masses is highly nontrivial (for a review on the subject, see [1,2]). The remarkable smallness of these masses, at least a factor 10 5 lighter than the electron mass, is usually regarded as an indication that new physics should be involved in their generation.The definite nature of this new physics, of course, depends on the specific model one wishes to consider, and there are plenty of them: the seesaw mechanism [2], which is one of the most popular proposals, the several models for radiative generation of masses [3] and many more. Precisely this abundance of proposals makes appealing the possibility of studying the new physics associated to neutrinos in a model-independent way. This can be done most easily if the new particles are very heavy, by eliminating them from our description of low-energy physics; the result is called an effective theory 1 , and has been for long a powerful tool for examining neutrino physics (see, for example, two early but interesting applications in [5,6]).However, in our current situation, and given the present knowledge and unknowns about neutrino masses, a piece of the puzzle has been mainly ignored: as we don't know if the neutrino masses are Dirac or Majorana, right-handed neutrinos might be among the light degrees of freedom of the theory. If they are, they must be included in the effective theory, or otherwise it will be incomplete. In any case, we don't know yet the nature of neutrino masses, so it seems sensible to include them for the sake of generality. This constitutes our starting point: we want to inspect an effective theory which can describe all possible neutrino mass structures, and see what insight it can cast upon new physics effects;1 For an example of the procedure, see, for instance, [4].

We study, at the one loop level, the dominant contributions from a single universal extra dimension to the process Z → bb. By resorting to the gaugeless limit of the theory we explain why the result is expected to display a strong dependence on the mass of the top-quark, not identified in the early literature. A detailed calculation corroborates this expectation, giving rise to a lower bound for the compactification scale which is comparable to that obtained from the ρ parameter.An estimate of the subleading corrections is furnished, together with a qualitative discussion on the difference between the present results and those derived previously for the non-universal case.

We present the first results of next-to-leading order QCD corrections to three jet heavy quark production at LEP including mass effects. Among other applications, this calculation can be used to extract the bottom quark mass from LEP data, and therefore to test the running of masses as predicted by QCD. 12.15.Ff, 12.38.Bx, 12.38.Qk, 13.38.Dg, 13.87.Ce, 14.65.Fy The decay width of the Z gauge boson into three jets has already been computed at the leading order (LO) including complete quark mass effects [1][2][3] where it has been shown that mass effects could be as large as 1% to 6%, depending on the value of the mass and the jet resolution parameter y c . In fact, these effects had already been seen in the experimental tests of the flavor independence of the strong coupling constant [4][5][6][7][8]. In view of that we proposed [3], together with the DELPHI collaboration [9], the possibility of using the ratio [3,6,7] as a means to extract the bottom quark mass from LEP data. In this equation Γ q 3j (y c )/Γ q is the three-jet fraction of Z decays into the quark q and y c is the jet resolution parameter.Since the measurement of R bd 3 is done far away from the threshold of b quark production, it will allow, for the first time, to test the running of a quark mass as predicted by QCD. However, in [3] we also discussed that the leading order calculation does not distinguish among the different definitions of the quark mass, perturbative pole mass, M b , running mass at M b , or running mass at m Z . Therefore in order to correctly take into account mass effects it is necessary to perform a complete next-to-leading order (NLO) calculation of three jet ratios including quark masses [10][11][12].In this letter we sketch the main points of this calculation, leaving the details of the complete calculation for other publications [13,14], and we present the results that have been used by the DELPHI collaboration to measure the running mass of the bottom quark at µ = m Z [15,16].In the last years the most popular definitions of jets are based on the so-called jet clustering algorithms. These algorithms can be applied at the parton level in the theoretical calculations and also to the bunch of real particles observed at experiment. In the jet-clustering algorithms jets are defined as follows: starting from a bunch of particles with momenta p i one computes, for example, a quantity like y ij = 2 min(E 2 i , E 2 j )/s (1 − cos θ ij ) for all pairs (i, j) of particles. Then one takes the minimum of all y ij and if it satisfies that it is smaller than a given quantity y c (the resolution parameter, y-cut) the two particles which define this y ij are regarded as belonging to the same jet, therefore, they are recombined into a new pseudoparticle by defining the four-momentum of the pseudoparticle according to some rule, for example, p k = p i + p j . After this first step one has a bunch of pseudoparticles and the algorithm can be applied again and again until all the pseudoparticles satisfy y ij > y c . The number of pseudop...

We update previous analyses of the Zee-Babu model in the light of new data, e.g., the mixing angle θ 13 , the rare decay µ → eγ and the LHC results. We also analyse the possibility of accommodating the deviations in Γ(H → γγ) hinted by the LHC experiments, and the stability of the scalar potential. We find that neutrino oscillation data and low energy constraints are still compatible with masses of the extra charged scalars accessible to LHC. Moreover, if any of them is discovered, the model can be falsified by combining the information on the singly and doubly charged scalar decay modes with neutrino data. Conversely, if the neutrino spectrum is found to be inverted and the CP phase δ is quite different from π, the masses of the charged scalars will be well outside the LHC reach.