An alternative approach to b->s\gamma in the unconstrained MSSM

The gluino contributions to the $C'_{7,8}$ Wilson coefficients for b->s\gamma are calculated within the unconstrained MSSM. New stringent bounds on the \dRLbs and \dRRbs mass insertion parameters are obtained in the limit in which the SM and SUSY contributions to $C_{7,8}$ approximately cancel. Such a cancellation can plausibly appear within several classes of SUSY breaking models. Assuming this cancellation takes place, we perform an analysis of the b->s\gamma decay. We show that, in the unconstrained MSSM such an alternative is reasonable and it is possible to saturate the b->s\gamma branching ratio and produce a CP asymmetry of up to 20%, from only the gluino contribution to $C'_{7,8}$ coefficients. Using photon polarization a LR asymmetry can be defined that in principle allows the $C_{7,8}$ and $C'_{7,8}$ contributions to the b->s\gamma decay to be disentangled.Comment: 6 pages, 4 eps figure, talk given at the XXXVIIth Rencontres de Moriond (ELECTROWEAK

One-loop Weak Dipole Form Factors and Weak Dipole Moments of Heavy Fermions

The one-loop weak-magnetic and weak-electric dipole form factors of heavy fermions in a generic model are derived. Numerical predictions for the $\tau$ lepton and $b$ quark Weak Anomalous Magnetic and Electric Dipole Moments (AWMDM and WEDM) in the SM and MSSM are reviewed. The MSSM contribution to the $\tau$ ($b$) AWMDM could be, in the high $\tan\beta$ scenario, four (thirty) times larger than the Electroweak SM one, but still a factor five below the QCD contribution (in the $b$ case). More interesting is the CP-odd sector where the contribution to the $\tau$ ($b$) WEDM in the MSSM could be up to twelve orders of magnitude larger than in the SM.Comment: 6 pages, 1 Postscript figure, uses epsfig.sty. Talk given at the XXXIIIrd Rencontre de Morion

Winding Modes and Large Extra Dimensions

We review briefly the main features of the Large Extra Dimensions scenario in the framework of weakly coupled Type I string theory. Kaluza-Klein (KK) excitations of the graviton are expected, whereas no KK modes for the gauge bosons arise if the gauge group is tied to a D3-brane. In this scenario, typical signatures such as direct production of KK modes of the graviton at high-energy colliders could test the size of the compactified dimensions. We point out that contrary to what considered in the literature on the subject, in the general case of anisotropic compactification Winding Modes of the Standard Model gauge bosons could also be directly observable, thus further constraining the model

Sigma decomposition: the CP-odd Lagrangian

Journal of High Energy Physics 2016.4 (2016): 016 reproduced by permission of Scuola Internazionale Superiore di Studi Avanzati (SISSA)Artículo escrito por un elevado número de autores, sólo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiera, y los autores pertenecientes a la UAMIn Alonso et al., JHEP 12 (2014) 034, the CP-even sector of the effective chiral Lagrangian for a generic composite Higgs model with a symmetric coset has been constructed, up to four momenta. In this paper, the CP-odd couplings are studied within the same context. If only the Standard Model bosonic sources of custodial symmetry breaking are considered, then at most six independent operators form a basis. One of them is the weak-θ term linked to non-perturbative sources of CP violation, while the others describe CP-odd perturbative couplings between the Standard Model gauge bosons and an Higgs-like scalar belonging to the Goldstone boson sector. The procedure is then applied to three distinct exemplifying frameworks: the original SU (5) /SO (5) Georgi-Kaplan model, the minimal custodial-preserving SO (5) /SO (4) model and the minimal SU (3) / (SU (2) × U (1)) model, which intrinsically breaks custodial symmetry. Moreover, the projection of the high-energy electroweak effective theory to the low-energy chiral effective Lagrangian for a dynamical Higgs is performed, uncovering strong relations between the operator coefficients and pinpointing the differences with the elementary Higgs scenarioThe work of I.M.H. is supported by an ESR contract of the European Union network FP7 ITN INVISIBLES (Marie Curie Actions, PITN-GA-2011-289442). L.M. acknowledges partial support of the European Union network FP7 ITN INVISIBLES, of CiCYT through the project FPA2012- 31880, of the Spanish MINECO’s “Centro de Excelencia Severo Ochoa” Programme under grant SEV-2012-0249, and by a grant from the Simons Foundation. S.R. acknowledges partial support of the European Union network FP7 ITN INVISIBLES and of the COFIN program PRIN 2010. This work was partially performed at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-106629

The minimal linear sigma model for the Goldstone Higgs

In the context of the minimal SO(5) linear {\sigma}-model, a complete renormalizable Lagrangian -including gauge bosons and fermions- is considered, with the symmetry softly broken to SO(4). The scalar sector describes both the electroweak Higgs doublet and the singlet {\sigma}. Varying the {\sigma} mass would allow to sweep from the regime of perturbative ultraviolet completion to the non-linear one assumed in models in which the Higgs particle is a low-energy remnant of some strong dynamics. We analyze the phenomenological implications and constraints from precision observables and LHC data. Furthermore, we derive the d <= 6 effective Lagrangian in the limit of heavy exotic fermions

Bounds on heavy chiral fermions

We derive the low-energy electroweak effective lagrangian for the case of additional heavy, unmixed, sequential fermions. Present data still allow for the presence of a new quark and/or lepton doublet with masses greater than M_Z/2, provided that these multiplets are sufficiently degenerate. Deviations of the effective lagrangian predictions from a full one-loop computation are sizeable only for fermion masses close to the threshold M_Z/2. Some of the constraints on new sequential fermions coming from accelerator results and cosmological considerations are presented. We point out that the new fermions can significantly affect the production and decay rate into \gamma \gamma of the intermediate Higgs at LHC

On the IR/UV flavour connection in non-universal axion models

Non-universal axion models, with the Peccei-Quinn (PQ) symmetry acting on Standard Model (SM) fermions in a generation-dependent way, are typically accompanied by two different sources of flavour violation, dubbed here as infrared (IR) and ultraviolet (UV). The former is due to the flavour violating axion couplings to SM fermions, while the latter arises from the heavy degrees of freedom that UV complete the axion effective field theory. We point out that these two sources of flavour violation are directly related and exemplify this connection in a general class of non-universal axion model, based on a renormalizable DFSZ-like setup with two Higgs doublets (PQ-2HDM). We next discuss the interplay of axion flavour phenomenology with the signatures stemming from the heavy radial modes of the PQ-2HDM, including meson oscillation observables and charged lepton flavour violating decays. We emphasize the strong complementarity between flavour observables, LHC direct searches and standard axion physics.Comment: 33 pages, 5 figure