Search

We analyse the Higgs sector of an $S_3$ model with three Higgs doublets and no CP violation. After electroweak breaking there are nine physical Higgs bosons, one of which corresponds to the Standard Model one. We study the scalar and gauge sectors of this model, taking into account the conditions set by the minimisation and stability of the potential. We calculate the masses, trilinear and quartic Higgs-Higgs, and Higgs-gauge couplings. We consider two possible alignment scenarios, where only one of the three neutral scalars has couplings to the gauge bosons and corresponds to the SM Higgs, and whose trilinear and quartic couplings reduce exactly to the SM ones. We also obtain numerically the allowed parameter space for the scalar masses in each of the alignment scenarios. We use the calculated trilinear and quartic couplings to find the analytical structure of the one-loop neutral scalar mass matrix, without fermionic contributions. We show that it is possible to have a compact mass spectrum where the contribution to the oblique parameters might be small. We explore some scenarios for the loop contributions to the neutral scalar masses., Comment: 48 pages, 3 figures, 2 tables. Improved and extended analysis (sections 2, 3 and 4), includes more detailed discussions with some clarifications and new figures. Introduction and Conclusion were modified accordingly. Text improved, references added, typographical errors corrected. This version corresponds to the one published in EPJC

We discuss $Z$ -production in the deep inelastic process $e + P \to e + Z + X$ in the context of the Standard Model using the Parton Model. In contrast to the deep inelastic $eP$-scattering ($e + P \to e + X$), where the choice of $\tilde{Q}^{2} $ is unambiguous, in this case is not clear since the momentum transfer square, at the quark level, depends on the reaction mechanism. Our aim in this work is to show that the total cross section depends strongly on the prescription used for the scale parameter $\tilde{Q}^{2}$ and on a different option that we have taken for making the convolution of the parton distribution functions and the amplitude of the quark processes. We present results for the total cross section as a function of the total energy $\sqrt{s}$ of the system $eP$, in the range $300 \leq \sqrt{s} \leq 1300$ GeV. We find differences of up to 25\% in the rates of the total cross section for the different prescriptions that we have taken, for $\sqrt{s} \approx 1300$ GeV, which is the expected maximal total energy of the system $eP$ to be reached at the LHeC. Taking an integrated luminosity of $ab^{-1}$, such a difference (25\%) corresponds to $\approx 10^4$ produced $Z$ bosons. Finally, we propose to modify slightly the Parton Model in order to do a simple and practical prescription for the calculation without ambiguities of the $Z$-production in the deep inelastic $eP$ scattering., Comment: 10 pages, 2 figures

In this work we explore a lepton flavor violation effect induced at one loop for a flavor structure in an extended minimal standard supersymmetric model, considering an ansatz for the trilinear term. In particular we find a finite expression which will show the impact of this phenomena in the $h\to \mu \tau$ decay, produced by a mixing in the trilinear coupling of the soft supersymmetric Lagrangian., Comment: 8 pages, 1 figure, To be published in Journal of Physics Conference Series (IOP). Joint Proceedings of the XV Mexican Workshop on Particles and Fields & the XXX Annual Meeting of the Division of Particles and Fields of the Mexican Physical Society

In this work we analyze the possibility to explain the muon anomalous magnetic moment discrepancy within theory and experiment through lepton flavor violation processes. We propose a flavor extended MSSM by considering a hierarchical family structure for the trilinear scalar Soft-Supersymmetric terms of the Lagranagian, present at the SUSY breaking scale. We obtain analytical results for the rotation mass matrix, with the consequence of having non-universal slepton masses and the possibility of leptonic flavour mixing. The one-loop supersymmetric contributions to the leptonic flavour violating process $\tau \to \mu\gamma$ are calculated in the physical basis, with slepton flavour mixed states, instead of using the well known Mass Insertion Method. We present the regions in parameter space where the muon g-2 problem is either entirely solved or partially reduced through the contribution of these flavor violating processes., Comment: 21 pages, 7 figures. Changes on version 3: In order to obtain the complete result for muon g-2 in the limit of non-flavor violation we added the terms given in the appendix. We redid the graphics and numerical analysis including these changes. We also corrected some typos and changed the order of figures

We study the constraints of the generic two-Higgs-doublet model (2HDM) type-III and the impacts of the new Yukawa couplings. For comparisons, we revisit the analysis in the 2HDM type-II. To understand the influence of all involving free parameters and to realize their correlations, we employ $\chi$-square fitting approach by including theoretical and experimental constraints, such as S, T, and U oblique parameters, the production of standard model Higgs and its decay to $\gamma\gamma$, $WW^*/ZZ^*$, $\tau^+\tau^-$, etc. The errors of analysis are taken at $68\%$, $95.5\%$, and $99.7\%$ confidence levels. Due to the new Yukawa couplings being associated with $\cos(\beta-\alpha)$ and $\sin(\beta -\alpha)$, we find that the allowed regions for $\sin\alpha$ and $\tan\beta$ in the type-III model can be broader when the dictated parameter $\chi_F$ is positive; however, for negative $\chi_F$, the limits are stricter than those in the type-II model. By using the constrained parameters, we find that the deviation from the SM in the $h\to Z\gamma$ can be of ${\cal O}(10\%)$. Additionally, we also study the top-quark flavor-changing processes induced at the tree level in the type-III model and find that when all current experimental data are considered, we get $Br(t\to c(h, H) )< 10^{-3}$ for $m_h=125.36$ and $m_H=150$ GeV and $Br(t\to cA)$ slightly exceeds $10^{-3}$ for $m_A =130$ GeV., Comment: 22 pages, 11 figures. v3: Slight change in the abstract, Figure.1 added and commented, the conclusion remains unchanged

We confront the discovery of a boson decaying to two photons}, as reported recently by ATLAS and CMS, with the corresponding predictions in the Minimal Supersymmetric Standard Model (MSSM) and the Next-to-Minimal Supersymmetric Standard Model (NMSSM). We perform a scan over the relevant regions of parameter space in both models and evaluate the MSSM and NMSSM predictions for the dominant Higgs production channel and the photon photon decay channel. Taking into account the experimental constraints from previous direct searches, flavour physics, electroweak measurements as well as theoretical considerations, we find that a Higgs signal in the two photon channel with a rate equal to, or above, the SM prediction is viable over the full mass range $123\gev \lsim M_H \lsim 127\gev$, both in the MSSM and the NMSSM. We find that besides the interpretation of a possible signal at about $125\gev$ in terms of the lightest $\cp$-even Higgs boson, both the MSSM and the NMSSM permit also a viable interpretation where an observed state at about $125\gev$ would correspond to the second-lightest $\cp$-even Higgs boson in the spectrum, which would be accompanied by another light Higgs with suppressed couplings to $W$ and $Z$ bosons. We find that a significant enhancement of the $\ga\ga$ rate, compatible with the signal strenghts observed by ATLAS and CMS, is possible in both the MSSM and the NMSSM, and we analyse in detail different mechanisms in the two models that can give rise to such an enhancement. We briefly discuss also our predictions in the two models for the production and subsequent decay into two photons of a $\cp$-odd Higgs boson., Comment: 37 pages

Effects of universal extra dimensions on Standard Model observables first arise at the one-loop level. The quantization of this class of theories is therefore essential in order to perform predictions. A comprehensive study of the Standard Model defined in a space-time manifold with one universal extra dimension, compactified on the oribifold $S^1/Z_2$, is presented. The fact that the four-dimensional Kaluza-Klein theory is subject to two types of gauge transformations is stressed and its quantization under the basis of the BRST symmetry discussed. A $SU_C(3) x SU_L(2) x U_Y(1)$-covariant gauge-fixing procedure for the Kaluza-Klein excitations is introduced. The connection between gauge and mass eigenstates fields is established in an exact way. An exhaustive list of the explicit expressions for all physical couplings induced by the Yang-Mills, Currents, Higgs, and Yukawa sectors is presented. The one-loop renormalizability of the standard Green's functions, which implies that the Standard Model observables do not depend on a cutoff scale, is stressed., Comment: 51 pages

We study flavor violating processes in the production or decay of a neutral pseudoscalar meson $P^0$ in the framework of a general two Higgs Doublet Model type III (2HDM-III). We use a version of the model where Yukawa interactions of neutral Higgs bosons allow for flavor change at the tree-level, but conserves CP symmetry. We focus on all possible $\tau^{\pm} \to l^{\pm}P^0 $ and $P^0 \to l^+l'^-$ decay channels, where $l,l'$ are charged leptons. We find that these processes provide complementary information on quark and lepton FCNC Yukawa couplings. In particular flavor violating parameters in the quark sector, $\chi_{sb}$ and $\chi_{db}$, are significantly constrained by present experimental data, whereas the corresponding parameters in the leptonic sector are less constrained., Comment: 13 pages, 7 figures

In this paper we propose an ansatz that applies to the slepton mass matrices. In our approach these matrices contain a dominant sector that can be diagonalized exactly. We study the numerical results for the slepton mass eigenstates, looking for deviations from universality, which is usually assumed when one evaluates the production of sleptons at future colliders., Comment: 13 pages, 3 figures

We present an introduction to the basic concepts of electroweak symmetry breaking and Higgs physics within the Standard Model and its supersymmetric extensions. A brief overview will also be given on alternative mechanisms of electroweak symmetry breaking. In addition to the theoretical basis, the present experimental status of Higgs physics and prospects at the Tevatron, the LHC and e+e- linear colliders are discussed., Comment: 124 pages, 36 figures, latex, english and spanish versions in succession

We investigate non-perturbative features of a three-dimensional Abelian Higgs model with singly- and doubly-charged scalar fields coupled to a single compact Abelian gauge field. The model is pretending to describe various planar systems of strongly correlated electrons such as high-Tc superconductivity in the overdoped regime and exotic materials possessing excitations with fractionalized quantum numbers. The complicated phase structure of the model is studied thoroughly using numerical tools and analytical arguments. In the three-dimensional space of coupling parameters we identify the Fermi liquid, the spin gap, the superconductor and the strange metallic phases. The behavior of three kinds of topological defects -- holon and spinon vortices and monopoles - is explored in various phases. We also observe a new effect, the strong enhancement of the phase transition strength reflected in a lower order of the transition: at sufficiently strong gauge coupling the two second order phase transitions -- corresponding to spinon-pair and holon condensation lines - join partially in the phase diagram and become a first order phase transition in that region. The last observation may have an analogue in Quantum Chromodynamics at non-zero temperature and finite baryon density. We argue that at sufficiently large baryon density the finite-temperature transition between the (3-flavor paired) color superconducting phase and the quark-gluon plasma phases should be much stronger compared with the transition between 2-flavor paired and 3-flavor paired superconducting phases., Comment: 21 pages, 40 figures, RevTeX 4.0

We study the SUSY flavor problem in the MSSM, we are namely interested in estimating the size of the SUSY flavor problem and its dependence on the MSSM parameters. For that, we made a numerical analysis randomly generating the entries of the sfermion mass matrices and then determinated which percentage of the points are consistent with current bounds on the flavor violating transitions on lepton flavor violating (LFV) decays $l_i \to l_j \gamma$. We applied two methods, mass-insertion approximation method (MIAM) and full diagonalization method (FDM). Furthermore, we determined which fermion masses could be radiatively generated (through gaugino-sfermion loops) in a natural way, using those random sfermion matrices. In general, the electron mass generation can be done with 30% of points for large $\tan\beta$, in both schemes the muon mass can be generated by 40% of points only when the most precise sfermion splitting (from the FDM) is taken into account., Comment: 23 pages, 10 figures

We calculate the branching ratios for the decays of neutral Higgs bosons ($h^{0},H^{0},A^{0}$) into pairs of fermions, including flavor violating processes, in the context of the General Two Higgs Doublet Model III., Comment: 23 pages, 10 figures, 6 tables. Text clarifying equations and references added, typos corrections

Presentamos una introduccion a los conceptos basicos del rompimiento de la simetria electrodebil y la fisica del Higgs dentro del Modelo Estandar y sus extensiones supersimetricas. Se presenta tambien una breve perspectiva general de mecanismos alternativos del rompimiento de la simetria. Ademas de las bases teoricas, se discute el estado actual de la fisica experimental del Higgs y sus implicaciones para futuros experimentos en el LHC y en colisionadores lineales e+e-., Comment: Spanish text, including full English translation. Published in the Proceedings of the XI Mexican School on Particles and Fields, Xalapa, Veracruz, Mexico