arXiv subjects

Gaber Faisel

Publications and source records attributed to Gaber Faisel.

32 records · Page 2Linked to original sources

arXiv2015

A Simple Model of Dynamical Supersymmetry Breaking with the Generation of Soft Mass(es)

We introduce a simple model of dynamical supersymmetry breaking. It is like a supersymmetric version of a Nambu--Jona-Lasinio model with a spin one composite. The simplest version of the model as presented here has a single chiral superfield (multiplet) with a four-superfield interaction. The latter has the structure of the square of the superfield magnitude square. A vacuum condensate of the latter is illustrated to develop giving rise to supersymmetry breaking with a soft mass term for the superfield. We report also the effective theory picture with a real superfield composite, illustrating the matching effective potential analysis and the vacuum solution conditions for the components. The nature of its fermionic part as the Goldstone mode is presented. Phenomenological application to the supersymmetric standard model is plausible.

hep-ph↗

arXiv2014

Exploring X-Ray Lines as Scotogenic Signals

We consider some implications of X-ray lines from certain astronomical objects as potential effects of dark matter decay in the context of the scotogenic model, where neutrinos acquire mass radiatively via one-loop interactions with dark matter. As an example, we focus on the 3.5 keV line recently detected in the X-ray spectra of galaxy clusters, assuming that it stands future scrutiny. We explore the scenario in which the line originates from the slow decay of fermionic dark matter in the model. After obtaining a number of benchmark points representing the parameter space consistent with the new data and various other constraints, we make predictions on several observables in leptonic processes. They include the effective Majorana mass in neutrinoless double-beta decay, the sum of neutrino masses, and the rate of flavor-changing decay mu -> e gamma, as well as the cross sections of e+e- collisions into final states containing nonstandard particles in the model. These are testable in ongoing or future experiments and thus offer means to probe the scotogenic scenario studied.

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arXiv2014

New Physics effects in D^+ \rightarrow K^- π^+ π^+

In this paper, we study the Cabibbo favored three body non-leptonic D^+ \rightarrow K^- π^+ π^+ decay. We show that the corresponding direct CP asymmetry is so tiny in the framework of the Standard Model and is out of the experimental range. Motivated by this result we extend the study of the CP asymmetry to include a toy model with CP violating weak phase equals 20 degrees in a_2, a model with extra gauge bosons within Left-Right Grand Unification models and a model with charged Higgs boson. We show that the toy model can strongly improve the SM prediction of the CP asymmetry to be about 30%. The largest CP asymmetry can be achieved in the non-manifest Left-Right models where a CP asymmetry up to 25% can be reached. For the two Higgs doublets models the CP asymmetry is of order 10^{-3}.

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arXiv2014

Charged Higgs contribution to $\bar{B}_s \rightarrow ϕπ^0 $ and $\bar{B}_s \rightarrow ϕρ^0 $

We study the decay modes $\bar{B}_s\to ϕπ^0$ and $\bar{B}_s\to ϕρ^0$ within the frameworks of two-Higgs doublet models type-II and typ-III. We adopt in our study Soft Collinear Effective Theory as a framework for the calculation of the amplitudes. We derive the contributions of the charged Higgs mediation to the weak effective Hamiltonian governing the decay processes in both models. Moreover we analyze the effect of the charged Higgs mediation on the Wilson coefficients of the electrowek penguins and on the branching ratios of $\bar{B}_s\to ϕπ^0$ and $\bar{B}_s\to ϕρ^0$ decays. We show that wthin two-Higgs doublet models type-II and type-III the Wilson coefficients corresponding to the electroweak penguins can be enhanced due to the contributions from the charged Higgs mediation leading into enhancement in the branching ratios of $ \bar{B}_s\to ϕπ^0$ and $\bar{B}_s\to ϕρ^0 $ decays. We find that, within two-Higgs doublet models type-II, the enhancement in the branching ratio of $\bar{B}_s\to ϕπ^0$ can not exceed $18\%$ with respect to the SM predictions. For the branching ratio of $\bar{B}_s\to ϕρ^0$, we find that the charged Higgs contribution in this case is small where the branching ratio of $\bar{B}_s\to ϕρ^0$ can be enhanced or reduced by about $4\% $ with respect to the SM predictions. For the case of the two-Higgs doublet models type-III we show that the branching ratio of $\bar{B}_s\to ϕπ^0$ can be enhanced by about a factor $2$ of its value within two-Higgs doublet models type-II. However no sizable enhancement with respect to the SM predictions can be obtained for both $\bar{B}_s\to ϕπ^0$ and $\bar{B}_s\to ϕρ^0$ decays.

hep-ph↗

arXiv2013

Constraining Nonstandard Neutrino-Electron Interactions due to a New Light Spin-1 Boson

We consider nonstandard interactions of neutrinos with electrons arising from a new light spin-1 particle with mass of tens of GeV or lower and couplings to the neutrinos and electron. This boson is not necessarily a gauge boson and is assumed to have no mixing with standard-model gauge bosons. Adopting a model-independent approach, we study constraints on the flavor-conserving and -violating couplings of the boson with the leptons from a number of experimental data. Specifically, we take into account the (anti)neutrino-electron scattering and e^+ e^- -> nu nubar gamma measurements and keep explicitly the dependence on the new particle mass in all calculations. We find that one of the two sets of data can provide the stronger constraints, depending on the mass and width of the boson. Also, we evaluate complementary constraints on its separate flavor-conserving couplings to the electron and neutrinos from other latest experimental results.

hep-ph↗

arXiv2013

Majorana versus Dirac mass from holomorphic supersymmetric Nambu-Jona-Lasinio Model

We study the theoretical features in relation to dynamical mass generation and symmetry breaking for the recently proposed holomorphic supersymmetric Nambu--Jona-Lasinio model. The basic model has two different chiral superfields (multiplets) with a strongly coupled dimension five four-superfield interaction. In addition to the possibility of generation of Dirac mass between the pair established earlier, we show here the new option of generation of Majorana masses for each chiral superfield. We also give a first look at what condition may prefer Dirac over Majorana mass, illustrating that a split in the soft supersymmetry breaking masses is crucial. In particular, in the limit where one of the soft masses vanish, we show that generation of the Majorana mass is no longer an option, while the Dirac mass generation survives well. The latter is sensitive mostly to the average of the two soft masses. The result has positive implication on the application of the model framework towards dynamical electroweak symmetry breaking with Higgs superfields as composites.

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arXiv2012

Observation of CP violation in $D^0 \rightarrow K^- π^+ $ as a smoking gun for New Physics

In this paper, we study the Cabibbo favored non-leptonic $D^0$ decays into $K^- π^+$ decays. First we show that, within the Standard Model, the corresponding CP asymmetry is strongly suppressed and out of the experimental range even taking into account the large strong phases coming from final state Interactions. We show also that although new physics models with extra sequential generation can enhance the CP asymmetry by few orders of magnitude however the resulting CP asymmetry is still far from experimental range. The most sensitive New Physics Models to this CP asymmetry comes from no-manifest Left-Right models where a CP asymmetry up to 10% can be reached and general two Higgs models extension of SM where a CP asymmetry of order $10^{-2}$ can be obtained without being in contradiction with the experimental constraints on these models.

hep-ph↗

arXiv2012

Dynamical Symmetry Breaking in Supersymmetric Extensions of Nambu-Jona-Lasinio Model

In this paper we discuss Nambu-Jona-Lasinio model as a classical model for dynamical mass generation and symmetry breaking. In addition we discuss the possible supersymmetric extensions of this model resulting from interaction terms with four chiral superfields that may be regarded as a supersymmetric generalization of the four-fermion interactions of the Nambu-Jona-Lasinio model. A four-superfield interaction terms can be constructed as either dimension 6 or dimension 5 operators. Through analyzing solutions to the gap equations, we discuss the dynamical generation of superfield Dirac mass, including a supersymmetry breaking part. A dynamical symmetry breaking generally goes along with the dynamical mass generation, for which a bi-superfield condensate is responsible.

hep-th↗

arXiv2012

Supersymmetric contributions to $\bar{B}_s \to ϕπ^0$ and $\bar{B}_s \to ϕρ^0$ decays in SCET

We study the decay modes $\bar{B}_s\to ϕπ^0$ and $\bar{B}_s\to ϕρ^0$ using Soft Collinear Effective Theory. Within Standard Model and including the error due to the SU(3) breaking effect in the SCET parameters we find that BR $\bar{B}_s\to ϕπ^0 =7_{-1-2}^{+1+2}\times 10^{-8} $ and BR $\bar{B}_s\to ϕπ^0=9_{-1-4}^{+1+3}\times 10^{-8}$ corresponding to solution 1 and solution 2 of the SCET parameters respectively.For the decay mode $\bar{B}_s\to ϕρ^0$, we find that BR $\bar{B}_s\to ϕρ^0 = 20.2^{+1+9}_{-1-12}\times 10^{-8} $ and BR $ \bar{B}_s\to ϕρ^0 = 34.0^{+1.5 + 15}_{-1.5-22}\times 10^{-8} $ corresponding to solution 1 and solution 2 of the SCET parameters respectively. We extend our study to include supersymmetric models with non-universal A-terms where the dominant contributions arise from diagrams mediated by gluino and chargino exchanges. We show that gluino contributions can not lead to an enhancement of the branching ratios of $\bar{B}_s\to ϕπ^0$ and $\bar{B}_s\to ϕρ^0$. In addition, we show that SUSY contributions mediated by chargino exchange can enhance the branching ratio of $\bar{B}_s\to ϕπ^0$ by about 14% with respect to the SM prediction. For the branching ratio of $\bar{B}_s\to ϕρ^0$, we find that SUSY contributions can enhance its value by about 1% with respect to the SM prediction.

hep-ph↗

arXiv2012

Dynamical Symmetry Breaking with Four-Superfield Interactions

We investigate the dynamical mass generation resulted from interaction terms with four chiral superfields. The kind of interactions maybe considered a supersymmetric generalization of the four-fermion interactions of the classic Nambu--Jona-Lasinio model. A four-superfield interaction that contains a four-fermion interaction as one of its component terms has been the standard supersymmetrization of the NJL model for decades. Recently, we introduced a holomorphic variant with a dimension five interaction term instead. The latter is a main target of the present analysis. With the introduction of a new perspective on the superfield gap equation, we derive it for each one of the four-superfield interactions, using the supergraph technique. Through analyzing solutions to the gap equations, we illustrate the dynamical generation of superfield Dirac mass, including a supersymmetry breaking part. A dynamical symmetry breaking generally goes along with the dynamical mass generation, for which a bi-superfield condensate is responsible. The explicit illustration of dynamical symmetry breaking from the holomorphic dimension five interaction is reported for the first time. It has rich and novel features, which would be easily missed without the superfield approach developed here. We also discuss the nature of the bi-superfield condensate and its role of the effective Higgs superfield picture for both cases, illustrating their difference. Note that such a holomorphic quark superfield interaction term can successful account for the electroweak symmetry breaking with Higgs superfields as composites.

hep-th↗

arXiv2011

B -> rho K and B -> pi K^* decays in SCET

Exploring hints of New Physics in the decay modes B -> pi K^* and B -> rho K can shed light on the B -> K pi puzzle. In this talk we discuss supersymmetric contributions to the direct CP asymmetries of the decays B -> pi K^* and B -> rho K within Soft Collinear Effective Theory. We consider non-minimal flavor SUSY contributions mediated by gluino exchange and apply the Mass Insertion Approximation in the analysis. We show that gluino contributions can enhance the CP asymmetries and accommodate the experimental results.

hep-ph↗

arXiv2011

Supersymmetric contribution to B to rho K and B to pi K^* decays in SCET

We analyze the supersymmetric contributions to the direct CP asymmetries of the decays $B \to πK^*$ and $B\toρK$ within Soft Collinear Effective Theory. We extend the Standard Model analysis of these asymmetries to include the next leading order QCD corrections. We find that, even with QCD correction, the Standard Model predictions can not accommodate the direct CP asymmetries in these decay modes. Using Mass Insertion Approach, we show that non-minimal flavor SUSY contributions mediated by gluino exchange can enhance the CP asymmetries significantly and thus can accommodate the experimental results.

hep-ph↗

arXiv2011

Axigluon on like-sign charge asymmetry ${\cal A}^b_{s\ell}$, FCNCs and CP asymmetries in B decays

A non-universal axigluon in generalized chiral color models leads to flavor changing neutral currents (FCNCs) at tree level. We analyze phenomenologically the new contributions to $B_{q}$ (q=d, s) mixing and the related CP asymmetries (CPAs) that are generated by axigluon exchange. We find that although $Δm_{B_q}$ can give a strict constraint on the parameters of $b\to q$ transition, the precise measurement of $\sin2β_{J/ΨK^0}$ can further exclude the parameter space of $b\to d$ transition. The axigluon-mediated effects can enhance the like-sign dimuon charge asymmetry ${\cal A}^{b}_{s\ell}$ by one order of magnitude larger than the standard model prediction. Accordingly, large CPA $\sin2β^{J/Ψϕ}_s$ and CPA difference $\sin2β_{JΨK^0}-\sin2β_{ϕK^0}$ are achieved.

hep-ph↗

arXiv2010

Lepton Flavour Violating tau and mu decays induced by scalar leptoquark

We show that the scalar leptoquark Yukawa couplings generate a significant lepton flavour violation. We compute the light scalar leptoquark contributions to the branching ratios (Br) of the lepton flavour violating (LFV) decays $\ell \to \ell_i \ell_j \bar{\ell}_j$ and $\ell \rightarrow \ell^{\prime} γ$ with (i,j = e,$μ$). We discuss the role of the relevant input parameters to these decay rates which are the Yukawa couplings ($h_{a\ell}$) with ($a=u,c,t$), the light scalar mass $M_{S_{1}}$ and the mixing angle $\sin2θ_{LQ}$. We investigate the experimental limits from $(g-2)_μ$, $μ-e$ conversion and $π\to e ν_e, μν_μ$ to get constraint on the input parameter space. We predict that the upper limits on the branching ratios of $τ\to \ell_i \ell_j \bar{\ell}_j $ can reach the experimental current limits. We also show that it is possible to accommodate both $τ\to \ell_i \ell_j \bar{\ell}_j$ and $τ\to \ellγ$ branching ratios for certain choices of LQ parameters.

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