Beyond oblique contributions: Δ\Deltar and W-mass in models with scalar leptoquarks

We study the dominant non-universal contributions to muon decay for the five scalar leptoquarks (LQs) allowed by the Standard Model gauge symmetries. By using a common computational framework, we isolate the new-Physics (NP) one-loop corrections over the observable $\Delta r$ and explore the connection with the $W$ boson mass. We highlight the role of non-universal terms considering, for the $SU(2)$ doublet and triplet LQs, a completely degenerate scenario, thus cancelling/moderating the effects of the oblique parameters S,T and U . We determine simple formulas that exhibit the leading non-universal behaviour generated by the introduction of extra Yukawa terms, and confront them against a present tension in $M_W$ and the projected FCC-ee accuracy.Comment: 11 pages, 12 figures . v2: added references and one figure missed in compiling v1. Few typos remove

Conformal anomaly actions for dilaton interactions

We discuss, in conformally invariant field theories such as QCD with massless fermions, a possible link between the perturbative signature of the conformal anomaly, in the form of anomaly poles of the 1-particle irreducible effective action, and its description in terms of Wess-Zumino actions with a dilaton. The two descriptions are expected to capture the UV and IR behaviour of the conformal anomaly, in terms of fundamental and effective degrees of freedom respectively, with the dilaton effective state appearing in a nonlinear realization. As in the chiral case, conformal anomalies seem to be related to the appearance of these effective interactions in the 1PI action in all the gauge-invariant sectors of the Standard Model. We show that, as a consequence of the underlying anomalous symmetry, the infinite hierarchy of recurrence relations involving self-interactions of the dilaton is entirely determined only by the first four of them. This relation can be generalized to any even space-time dimension.Comment: 6 pages, 2 figure

Stability constraints of the scalar potential in extensions of the Standard Model with TeV scale right handed neutrinos

We investigate the stability of the scalar potential in a minimal $U(1)'$ extension of the Standard Model augmented by an extra complex scalar and three right handed neutrinos. We consider a type-I seesaw scenario for the generation of the small neutrino masses. Moreover, we focus our analysis on a class of models potentially accessible at the LHC experiment, in which the vacuum expectation value of the extra scalar is chosen in the TeV range. We show that the requirements of stability of the potential within the perturbative evolution under the renormalization group impose significant constraints on the Yukawa couplings of the right handed neutrinos.Comment: 6 pages, 2 figures, Presented at NOW 2014, 7-14 September 2014, Conca Specchiulla (Otranto-Italy

Vacuum Stability in U(1)-Prime Extensions of the Standard Model with TeV Scale Right Handed Neutrinos

We investigate a minimal $U(1)'$ extension of the Standard Model with one extra complex scalar and generic gauge charge assignments. We use a type-I seesaw mechanism with three heavy right handed neutrinos to illustrate the constraints on the charges, on their mass and on the mixing angle of the two scalars, derived by requiring the vacuum stability of the scalar potential. We focus our study on a scenario which could be accessible at the LHC, by selecting a vacuum expectation value of the extra Higgs in the TeV range and determining the constraints that emerge in the parameter space. To illustrate the generality of the approach, specific gauge choices corresponding to $U(1)_{B-L}, U(1)_R$ and $U(1)_\chi$ are separately analyzed. Our results are based on a modified expression of one of the $\beta$ functions of the quartic couplings of the scalar potential compared to the previous literature. This is due to a change in the coefficient of the Yukawa term of the right handed neutrinos. Differently from previous analysis, we show that this coupling may destabilize the vacuum.Comment: 15 pages, 16 figures, accepted for publication on PL

The Dilaton Wess-Zumino Action in 6 Dimensions from Weyl Gauging: Local Anomalies and Trace Relations

We extend a previous analysis on the derivation of the dilaton Wess-Zumino (WZ) action in $d=4$, based on the method of Weyl gauging, to $6$ dimensions. As in the previous case, we discuss the structure of the same action in dimensional regularization using 6-dimensional Weyl invariants, extracting the dilaton interactions in the most general scheme, with the inclusion of the local anomaly terms. As an application, we present the WZ action for the (2,0) tensor multiplet, which has been investigated in the past in the context of the $AdS_7/CFT_6$ holographic anomaly matching. We then extend to $d=6$ the investigation of fully traced correlation functions of EMT's, formerly presented in $d=4$, showing that their hierarchy is functionally related only to the first 6 correlators. We give the explicit expressions of these in the most general scheme, up to rank-4.Comment: 33 pages. arXiv admin note: text overlap with arXiv:1306.424

Conformal Trace Relations from the Dilaton Wess-Zumino Action

We use the method of Weyl-gauging in the determination of the Wess-Zumino conformal anomaly action, to show that in any even ($d = 2 k$) dimensions all the hierarchy of correlation functions involving traces of the energy-momentum tensor is determined in terms of those of lower orders, up to $2 k$. We work out explicitly the case $d=4$, and show that in this case in any conformal field theory only the first 4 traced correlators are independent. All the remaining correlators are recursively generated by the first 4. The result is a consequence of the cocycle condition which defines the Wess-Zumino action and of the finite order of its dilaton interactions.Comment: 18 page

Phase transition and vacuum stability in the classically conformal B-L model

Within classically conformal models, the spontaneous breaking of scale invariance is usually associated to a strong first order phase transition that results in a gravitational wave background within the reach of future space-based interferometers. In this paper we study the case of the classically conformal gauged B-L model, analysing the impact of this minimal extension of the Standard Model on the dynamics of the electroweak symmetry breaking and derive its gravitational wave signature. Particular attention is paid to the problem of vacuum stability and to the role of the QCD phase transition, which we prove responsible for concluding the symmetry breaking transition in part of the considered parameter space. Finally, we calculate the gravitational wave signal emitted in the process, finding that a large part of the parameter space of the model can be probed by LISA.Comment: 11 pages, 6 figures. Minor changes to match the published versio