The long-standing anomaly in the anomalous magnetic moment of the muon indicates the presence of chirality violating new physics contributions. A possible solution involves scalar leptoquarks with left-and right-handed couplings to the top quark. Two such representations of scalar leptoquarks exist for which the contribution to (g − 2)µ can possess an mt/mµ enhancement compared to the Standard Model. The leptoquarks also induce loop corrections to Z couplings to muons which probe as well new physics contributions which possess sources of SU (2) symmetry breaking and we find that this effect should be observable at future experiments as GigaZ or TLEP. Furthermore, once interactions of the leptoquark with tau leptons and electrons are present, additional correlated effects in anomalous magnetic moments, Z → and → γ arise, which can be used to test the model and to determine the flavour structure of the couplings. We find that the two representations of leptoquarks can be distinguished also from low energy experiments: one representation predicts constructive interference with the Standard Model in Z couplings to leptons and effects in B → K ( ) νν, while the other representation interferes destructively with the Standard Model in Z couplings to leptons and gives a C9 = C10-like contribution to b → s + − processes.

We study the possibility of detecting New Physics (NP) phenomena at the LHC through a new search strategy looking at the monotop (top plus missing energy) signature which is common to a variety of NP models. We focus on the leptonic top decay mode and study the discovery or exclusion reach of the 2012 LHC data for three example models. Contrary to the hadronic mode, in this case the problematic QCD multijet background can be safely neglected. We find that the key kinematic variable to suppress most of the remaining SM backgrounds is the transverse mass of the charged lepton and missing energy. In fact, one could expect that the single-top production measurements already address the monotop signature in this mode. This is however not the case because in the SM single-top production the transverse mass has an end point determined by the W mass, while the NP signals typically have an additional source of missing energy. We compare, under the same conditions, our monotop search strategy with existing single-top measurements and find a considerable improvement in the monotop signature reach.

have proposed a large Nc method to evaluate hadronic weak matrix elements to attack for instance the determination of the ∆I = 1 /2-rule and Re ( ǫ ′ /ǫ). Here we test this method to the determination of the form factor parameters a+ and b+ in the decays K + → π + ℓ + ℓ − and KS → π 0 ℓ + ℓ − . The results are encouraging: in particular after a complete treatment of Vector Meson Dominance (VMD).

We propose a charged, electrically neutral, and flavor-changing Z 0 model to conciliate the apparent disagreement between the important excess found in the t " t Tevatron forward-backward asymmetry and the null-compatible with negative-results found in the LHC charge asymmetry. We show that this model contributes positively to the forward-backward asymmetry, whereas naturally a new cancellation is turned on at the LHC, yielding a null, or even negative, charge asymmetry. We find the region in parameter space that is simultaneously allowed by the stringent Tevatron and LHC observables. We show that the model is safe to atomic parity violation constraints and propose a possible increase in the Z 0 width to avoid restrictions coming from tj= " tj resonance searches and t " tj cross section. We evaluate the constraints to the model, as well as distinctive features in the forecoming experimental results.