This thesis covers a few successes of the SM and its limitations. The limitations implement that the SM must be expanded to explain the observables which can not be addressed by the SM such as mass of neutrinos, a few of anomalies, DM, DE, etc. In order to extend the SM, we take the model-dependent approach and a minimal extension to the SM. For the minimal extension, we make use of vector-like family, SM-like scalar (plus a singlet flavon), and $U(1)^\prime$ symmetry. A first BSM model in my first work is to explain both the electron and muon anomalous magnetic moments at the same time, while keeping the constraints $μ\rightarrow e γ$ decay and neutrino trident production. Especially, two mass sources, chirality flip and vector-like mass, appear in our analytic prediction for the anomalies and the chirality flip mass between $0$ and $200 \operatorname{GeV}$ is searched and then we show no any value between them can satisfy the anomalies at the same time. A second BSM model in my second work shares the same motivation, to explain both anomalies, however it goes one step further by considering the strong hierarchical structure of the SM into the second BSM model. In this BSM model, the SM appears as an effective theory spontaneously broken from the $U(1)^\prime$ symmetry. Both anomalies are studied in the neutrino sector first and it reveals that the neutrino contributions are too small to explain their experimental bounds, so leading to a conclusion that the neutrinos can not explain both anomalies simultaneously. Next we study the scalar contribution and show that the scalar contributions can explain both anomalies simultaneously. My third work investigate the diverse FCNCs within the same second BSM model to constrain mass range of vector-like fermions.
We study an extended 2 Higgs doublet model (2HDM) in which the Standard Model (SM) Yukawa interactions are forbidden due to a global $U(1)^\prime$ symmetry, but may arise via mixing with vector-like families. In this model, the hierarchical structure of Yukawa couplings of quarks and leptons in the SM arises from the heavy masses of the fourth and fifth vector-like families. Within this model, we consider various non-standard contributions to the electron and muon anomalous magnetic moments. We first consider the $W$ exchange at one-loop level, consistent with the $μ\rightarrow e γ$ constraint…
We discuss the issue of fermion mass hierarchies between lepton and quark families in toy models of dynamical generation of fermion masses through minimal Lorentz Invariance Violation. Realistic hierarchies in chiral theories necessitate an extended gauge structure, which includes both vector and axial-vector interactions.
We consider two distinct classes of Yukawa unified supersymmetric SO(10) models with non-universal and universal soft supersymmetry breaking (SSB) gaugino masses at M_{\rm GUT}. In both cases, we assume that the third family SSB sfermion masses at M_{\rm GUT} are different from the corresponding sfermion masses of the first two families (which are equal). For the SO(10) model with essentially arbitrary (non-universal) gaugino masses at M_{\rm GUT}, it is shown that t-b-τYukawa coupling unification is compatible, among other things, with the 125 GeV Higgs boson mass, the WMAP relic dark matter …
We perform a comprehensive analysis of the most distinctive and important phenomenological implications of the recently proposed mechanism of sequential loop generation of strong hierarchies in the Standard Model (SM) fermion mass spectra. This mechanism is consistently realized at the level of renormalizable interactions in an extended variant of the Inert Higgs Doublet model, possessing the additional $Z_{2}^{(1)}\times Z_{2}^{(2)}$ discrete and $U_{1X}$ gauge family symmetries, while the matter sectors of the SM are extended by means of $SU_{2L}$-singlet scalars, heavy vector-like leptons a…
We show that, within the framework of $SU(5)$ Grand Unified Theories (GUTs), multiple vector-like families at the GUT scale which transform under a gauged $U(1)'$ (under which the three chiral families are neutral) can result in a single vector-like family at low energies which can induce non-universal and flavourful $Z'$ couplings, which can account for the B physics anomalies in $R_{K^{(*)}}$. In such theories, we show that the same muon couplings which explain $R_{K^{(*)}}$ also correct the Yukawa relation $Y_e=Y_d^T$ in the muon sector without the need for higher Higgs representations. To …
We study a two-Higgs-doublet model with four generalised CP symmetries in the scalar sector. Electroweak symmetry breaking leads automatically to spontaneous breaking of two of them. We require that these four CP symmetries can be extended from the scalar sector to the full Lagrangian and call this requirement the principle of maximal CP invariance. The Yukawa interactions of the fermions are severely restricted by this requirement. In particular, a single fermion family cannot be coupled to the Higgs fields. For two fermion families, however, this is possible. Enforcing the absence of flavour…
In this paper, we consider the Standard Model (SM) with one family of vector-like (VL) leptons, which couple to all three families of the SM leptons. We study the constraints on this model coming from the heavy charged lepton mass bound, electroweak precision data, the muon anomalous magnetic moment, lepton flavor violation, Higgs decay constraints and a recently measured lepton non-universality observable, $R_{K^{*0}}$. We find that the strongest constraints are coming from the muon $g-2, \ R_{μμ}=Γ(h\toμμ)/Γ(h\toμμ)_\text{SM}, \ R_{γγ}$ and $\text{BR}(μ\to eγ)$. Although VL leptons couple to…
The recent measurement of a_μ=\frac{g_μ-2}{2} by the E821 Collaboration at Brookhaven deviates from the quoted Standard Model (SM) central value prediction by 2.6σ. The difference between SM theory and experiment may be easily accounted for in a variety of particle physics models employing weak scale supersymmetry (SUSY). Other supersymmetric models are distinctly disfavored. We evaluate a_μfor various supersymmetric models, including minimal supergravity (mSUGRA), Yukawa unified SO(10) SUSY GUTs, models with inverted mass hierarchies (IMH), models with non-universal gaugino masses, gauge medi…
We discuss the sparticle (and Higgs) spectrum in a class of flavor symmetry-based minimal supersymmetric standard models, referred to here as sMSSM. In this framework the SUSY breaking Lagrangian takes the most general form consistent with a grand unified symmetry such as SO(10) and a non-Abelian flavor symmetry acting on the three families with either a 2+1 or a 3 family assignment. Models based on gauged SU(2) and SO(3) flavor symmetry, as well as non-Abelian discrete symmetries such as S_3 and A_4, have been suggested which fall into this category. These models describe supersymmetry breaki…
The Extended Supersymmetric Standard Model (ESSM), motivated on several grounds, introduces two vectorlike families (16 + 16-bar) of SO(10)) with masses of order one TeV. It is noted that the successful predictions of prior work on fermion masses and mixings, based on MSSM embedded in SO(10), can be retained rather simply within the ESSM extension. These include an understanding of the smallness of V_{cb} ~ 0.04 and the largeness of nu_mu - nu_tau oscillation angle, sin^2 2 theta_{nu_mu nu_tau}^{osc} ~ 1. We analyze the new contributions arising through the exchange of the vectorlike families …
This thesis provides a pedagogical overview of the theoretical foundations of the McMule framework, a Monte Carlo integrator for processes with muons and other leptons. Among other things, we show how the simple infrared structure in QED can be exploited to construct FKS$^\ell$, a subtraction scheme for soft singularities to all orders in perturbation theory. Furthermore, we present the method of massification as a solution to the problem of multi-scale integrals in the presence of large scale hierarchies. Finally, we introduce next-to-soft stabilisation as an elegant tool to stabilise the num…
We extended the standard model with a fourth generation of fermions to explain the discrepancy in the muon magnetic moment and to describe the positron excess observed by AMS-02 experiment. We introduce a gauged $SU(2)_{HV}$ horizontal symmetry between the muon and the 4th generation lepton families and identified the 4th generation right-handed neutrino as the dark matter with mass $\sim 700$ GeV. The dark matter annihilates through $SU(2)_{HV}$ gauge boson into final states $(μ^+ μ^-)$ and $(ν^c_μ~ν_μ)$. The $SU(2)_{HV}$ gauge boson with mass $\sim 1.4$ TeV gives the required contribution to…
Our study starts with a sequence of puzzles that include $(a)$ at which level $μ$ problem involving electroweak symmetry breaking can be solved; $(b)$ in which paradigm masses of superpartners in the third family can be lighter than in the first two families; $(c)$ whether it is possible to accommodate 125 GeV Higgs boson simultaneously; and $(d)$ how natural such paradigm is. These issues are considered in the context of two-site SUSY models. Both the MSSM and NMSSM as low-energy effective theory below the scale of two-site gauge symmetry breaking are investigated. We find that the fine tunin…
We studied an extension of the standard model with a fourth generation of fermions to explain the discrepancy in the muon $(g-2)$ and explain the positron excess seen in the AMS-02 experiment. We introduce a gauged $SU(2)_{HV}$ horizontal symmetry between the muon and the 4th generation lepton families. The 4th generation right-handed neutrino is identified as the dark matter with mass $\sim 700$ GeV. The dark matter annihilates only to $(μ^+ μ^-)$ and $(ν^c_μ~ν_μ)$ states via $SU(2)_{HV}$ gauge boson. The $SU(2)_{HV}$ gauge boson with mass $\sim 1.4$ TeV gives an adequate contribution to the …
We propose a renormalizable theory with minimal particle content and symmetries, that successfully explains the number of Standard Model (SM) fermion families, the SM fermion mass hierarchy, the tiny values for the light active neutrino masses, the lepton and baryon asymmetry of the Universe, the dark matter relic density as well as the muon and electron anomalous magnetic moments. In the proposed model, the top quark and the exotic fermions do acquire tree-level masses whereas the SM charged fermions lighter than the top quark gain one-loop level masses. Besides that, the tiny masses for the …
We describe a machine-learning system that uses linear vector-space based techniques for inference from observations to extend previous work on model construction for particle physics (Valdes-Perez 96, 94, Kocabas 91). The program searches for quantities conserved in all reactions from a given input set; given current data it rediscovers the family conservation laws: baryon#, electron#, muon# and tau#. We show that these families are uniquely determined by frequent decay data.
We propose an inverse seesaw scenario under hidden $U(1)$ gauge symmetry, having rather natural hierarchies among neutral fermion mass scales. The hierarchies are derived from theory and experimental constraints. The theory requires Majorana exotic masses have to be induced at one-loop level. The experimental side requests that the Dirac mass terms has to be highly suppressed to satisfy the constraints from the lepton flavor violations(LFVs) such as $μ\to eγ$. In order to induce such a small Majorana exotic masses we introduce exotic fermions and bosons that also provide us additional intrigui…
The proposed ICAL experiment at INO aims to identify the neutrino mass hierarchy from observations of atmospheric neutrinos, and help improve the precision on the atmospheric neutrino mixing parameters. While the design of ICAL is primarily optimized to measure muon momentum, it is also capable of measuring the hadron energy in each event. Although the hadron energy is measured with relatively lower resolution, it nevertheless contains crucial information on the event, which may be extracted when taken concomitant with the muon data. We demonstrate that by adding the hadron energy information …
We discuss a simple renormalisable, gauge invariant model with a fermiophobic $Z'$ boson: it has no couplings to the three Standard Model (SM) chiral families, but does couple to a fourth vector-like (VL) family. The SM Higgs couples to the fourth VL lepton, leading to an enhanced contribution to the muon anomalous magnetic moment $\left(g-2\right)_μ$. The latter contribution requires a non-vanishing coupling of $Z'$ to right-handed muons, which arises within this model due to mixing effects between the SM and VL fermions, along with $Z'$ couplings to the second generation SM lepton doublet an…
Effective supersymmetry(SUSY) where stop is the lightest squark may run into a two-loop tachyonic problem in some Z' mediation models. In addition, a large A term or/and a large stop mass are needed to have about a 126 GeV Higgs boson with three families of quarks and leptons. Thus, we suggest an inverted effective SUSY(IeffSUSY) where stop mass is larger compared to those of the first two families. In this case, it is possible to have a significant correction to the anomalous magnetic moment of muon. A three family IeffSUSY in a Z' mediation scenario is explicitly studied with the Z' quantum …
Supersymmetric SU(5) GUT augmented with anomaly free U(1)_F flavor symmetry is presented. Very economical field content and U(1)_F charge assignment are obtained by specific construction. In particular, three families of 10+5* chiral matter, along the SU(5) singlet states (some of which serve as right handed neutrinos) are obtained. Appealing texture zero Yukawa matrices provide natural understanding of hierarchies between charged fermion masses and mixings. The model predicts inverted hierarchical neutrino mass scenario with interesting implications.
In third quantization the origin of fermion families is easy to understand: the electron field, the muon field and the tau field are identical fields in precisely the same sense as three electrons are identical and undistinguishable particles of a theory of second quantization. In both cases, the permutation of these fields or particles leaves the lagrangian invariant. One can also extend the concept of family to gauge bosons. This can be obtained through the semidirect product of the gauge group with the group of permutations of n objects. In this paper we have studied the group E_6^4 x S_4. …
We analyse the structure of Yukawa couplings in local SU(5) F-theory models with $E_8$ enhancement. In this setting the $E_8$ symmetry is broken down to SU(5) by a 7-brane configuration described by T-branes, all the Yukawa couplings are generated in the vicinity of a point and only one family of quarks and leptons is massive at tree-level. The other two families obtain their masses when non-perturbative effects are taken into account, being hierarchically lighter than the third family. However, and contrary to previous results, we find that this hierarchy of fermion masses is not always appro…
The deviation of the measured value of the muon anomalous magnetic moment from the standard model prediction can be completely explained by mixing of the muon with extra vectorlike leptons, L and E, near the electroweak scale. This mixing simultaneously contributes to the muon mass. We show that the correlation between contributions to the muon mass and muon g-2 is controlled by the mass of the neutrino originating from the doublet L. Positive correlation, simultaneously explaining both measured values, requires this mass below 200 GeV. The decay rate of the Higgs boson to muon pairs is modifi…
We propose a possible particle physics explanation of the non-observation of muon neutrino events at IceCube coincident with GRB gamma ray at the rates predicted by the standard Bahcall-Waxman model, in terms of neutrino oscillations. Our model is based on assuming that (a) all neutrinos are pseudo-Dirac particles and (b) there exists a mirror world interacting gravitationally with the observed world. This scenario has three sterile neutrinos associated with each flavour of ordinary neutrinos. Very tiny mass splitting between these neutrinos is assumed to arise from lepton number violating dim…
You have probably often set hbar=1; but for what particle? I revisit here the possibility of a non-universal Planck-constant. Anomaly cancellation suggests that all particles in the same family perceive the same hbar at fixed charges e, g_w, g_s; the difference between the muon's and the electron's (and thus the first and second families) can be tightly constrained by the muon's anomalous magnetic moment,but constraints are weaker for the third family. Neutrino mixing could have proceeded a priori not only by the Lagrangian neutrino mass-term, but also by the kinetic term if Planck's constant …
The flavour puzzle is an open problem both in the Standard Model and in its possible supersymmetric or grand unified extensions. In this thesis, we discuss possible explanations of the origin of fermion mass hierarchies and mixings by the use of non-Abelian discrete flavour symmetries. We present a T'- and an S4-based realisations in which the spontaneous breaking of the symmetry produces realistic fermion mass hierarchies, the quark mixing matrix comparable to the Wolfenstein parametrisation and the lepton mixing matrix close to the so-called tribimaximal pattern. We also present an alternati…
We consider a four flavour scenario for the neutrinos where an extra sterile neutrino is introduced with the three families of active neutrinos and study the deviation from three flavour scenario in the ultra high energy (UHE) regime. We calculate the possible muon and shower yields at a 1 Km$^2$ detector such as ICECUBE for these neutrinos from distant UHE sources namely Gamma Ray Bursts (GRBs) etc. Similar estimations for muon and shower yields are also obtained for three flavour case. Comparing the two results we find considerable differences of the yields for these two cases. This can be u…
We study an Abelian gauge extension of the standard model with fermion families having non-universal gauge charges. The gauge charges and scalar content are chosen in such an anomaly-free way that only the third generation fermions receive Dirac masses via renormalisable couplings with the Higgs boson. Incorporating additional vector like fermions and scalars with appropriate $U(1)$ charges can lead to radiative Dirac masses of first two generations with neutral fermions going in the loop being dark matter candidates. Focusing on radiative muon mass, we constrain the model from the requirement…
In the context of the recent (79.5 kTy) Super-Kamiokande atmospheric neutrino data, we concisely review the status of muonic-tauonic flavor oscillations and of the subdominant electron or sterile neutrino mixing, in schemes with three or four families and one dominant mass scale. In the three-family case, where we include the full CHOOZ spectral data, we also show, through a specific example, that ``maximal'' violations of the one-dominant mass scale approximation are not ruled out yet.
We propose a bottom-up approach that a structure of a high-energy physics is explored by accumulating existence proofs and/or no-go theorems in the standard model or its extension. As an illustration, we study fermion mass hierarchies based on an extension of the standard model with vector-like fermions. It is shown that a magnitude of elements of Yukawa coupling matrices can become $O(1)$ and a Yukawa coupling unification can be realized in a theory beyond the extended model, if vector-like fermions mix with three families. In this case, small Yukawa couplings in the standard model can be hig…
We discuss how realistic supersymmetric models can be constructed by employing an anomalous ${\cal U}(1)$ flavor symmetry which also mediates supersymmetry breaking. A judicious choice of ${\cal U}(1)$ charges enables the first two squark families to be sufficiently heavy ($\stackrel{>}{_\sim}10$ TeV), so that flavor changing neutral currents as well as dimension five nucleon decay are adequately suppressed. Using the SU(5) example, the charged fermion mass hierarchies, magnitudes of the CKM matrix elements, as well as the observed neutrino oscillations are simultaneously accommodated. We esti…
We consider the collider signature of right-handed neutrinos propagating in $δ$ (large) extra dimensions, and interacting with Standard Model fields only through a Yukawa coupling to the left-handed neutrino and the Higgs boson. These theories are attractive as they can explain the smallness of the neutrino mass, as has already been shown. We show that if $δ$ is bigger than two, it can result in an enhancement in the production rate of the Higgs boson, decaying either invisibly or to a $b$ anti-$b$ quark pair, associated with an isolated high $p_T$ charged lepton and missing transverse energy …
We compare theoretical and experimental predictions of two main classes of models addressing fermion mass hierarchies and flavour changing neutral currents (FCNC) effects in supersymmetry: Froggatt-Nielsen (FN) U(1) gauged flavour models and Nelson-Strassler/extra dimensional models with hierarchical wave functions for the families. We show that whereas the two lead to identical predictions in the fermion mass matrices, the second class generates a stronger suppression of FCNC effects. We prove that, whereas at first sight the FN setup is more constrained due to anomaly cancelation conditions,…
We propose a model with two Higgs doublet where quark and charged-lepton masses in the first and second families are induced at one-loop level, and neutrino masses are induced at the two-loop level. In our model we introduce an extra $U(1)_R$ gauge symmetry that plays a crucial role in achieving desired terms in no conflict with anomaly cancellation. We show the mechanism to generate fermion masses, the resultant mass matrices and Yukawa interactions in mass eigenstates, and discuss several interesting phenomenologies such as muon anomalous magnetic dipole moment and dark matter candidate that…
We propose a gauged $U(1)_{B-L}$ extended two Higgs doublet model to explain both neutrino mass and lepton anomalous magnetic moments ($g-2$). Neutrino mass is generated via an inverse seesaw mechanism by introducing singlet fermions. Especially, we update the result of muon $g-2$ in light of the very recent report by E989 experiment at Fermilab, indicating $a_μ^{\rm FNAL}=116592040(54)\times 10^{-11}$. Combining BNL result, we have the following deviation from the standard model prediction $Δa_μ=(2.51\pm 5.9)\times10^{-10}$ at 4.2 $σ$. Thanks to an appropriate assignment for $U(1)_{B-L}\times…
We investigate collider signatures of standard model extensions featuring vector-like leptons and a flavorful scalar sector. Such a framework arises naturally within asymptotically safe model building, which tames the UV behavior of the standard model towards the Planck scale and beyond. We focus on values of Yukawa couplings and masses which allow to explain the present data on the muon and electron anomalous magnetic moments. Using a CMS search based on $77.4 \, \rm{fb}^{-1}$ at the $\sqrt{s}=13$ TeV LHC we find that flavorful vector-like leptons are excluded for masses below around $300$ Ge…
We discuss the bounds on the cosmological lepton number from Big Bang Nucleosynthesis (BBN), in light of recent evidences for a large value of the neutrino mixing angle theta13. The largest asymmetries for electron and muon or tau neutrinos compatible with 4He and 2H primordial yields are computed versus the neutrino mass hierarchy and mixing angles. The flavour oscillation dynamics is traced till the beginning of BBN and neutrino distributions after decoupling are numerically computed. The latter contains in general, non thermal distortion due to the onset of flavour oscillations driven by so…
We implement a symmetry violation guideline into a two-Higgs-doublet model embedded with three right-handed neutrinos, and exploit the generic Yukawa structures of the model via a hypothetical symmetry restoration of a global $U_Q(1)^3\times U_L(1)^3$ symmetry. We then apply a mass-powered parametrization to construct the phenomenologically motivated Yukawa interactions, which enables us to incorporate correlatively the neutrino mass, dark matter, as well as the lepton-flavor universality violations in $R_{K^{(*)}}$ and $R_{D^{(*)}}$. Specifically, two atmospheric-scale neutrino masses are gen…
Nonabelian discrete groups are an attractive tool to describe fermion masses and mixings. They have nonsinglet representations which seem particularly suitable for distinguishing the lighter generations from the heavier ones. Also, they do not suffer from the extra constraints a continuous group must obey, e.g. limits on extra particles. Some of the simplest groups are the nonabelian discrete subgroups of SO(3) and SU(2), the so called dihedral groups D_n and dicyclic groups Q_2n, which both have only singlet and doublet representations. After studying which vacuum expectation value (VEV) dire…
We build a renormalizable theory where the inverse seesaw mechanism explains the pattern of SM fermion masses. To the best of our knowledge, our model corresponds to the first implementation of the inverse seesaw mechanism for the charged fermion sector. In our theory, the inverse seesaw mechanism is implemented at the tree and one-loop levels in order to generate the masses for the second and first families of the SM charged fermions, respectively. The third family of SM charged fermions obtain tree-level masses from the Higgs doublets $ϕ_{1}$ (for the top quark) and $ϕ_{2}$ (for the bottom q…
A Roadmap for neutrino charge assignments in $U(2)_F$ Flavor Models: Implications for LFV processes and leptonic anomalous magnetic moments
Universitá di Roma Tre（罗马三大学）；INFN Sezione di Roma Tre（意大利国家核物理研究所罗马三分部）；Instituto de Física Corpuscular (IFIC), Universitat de València-CSIC（瓦伦西亚大学-西班牙国家科研委员会粒子物理研究所）
We propose an extension to the Standard Model accommodating two families of Dirac neutral fermions and Majorana fermions under additional ${U(1)_{e-μ} \times Z_3\times Z_2}$ symmetries where ${U(1)_{e-μ}}$ is a flavor dependent gauge symmetry related to the first and second family of the lepton sector, which features a two-loop induced neutrino mass model. The two families are favored by minimally reproducing the current neutrino oscillation data and two mass difference squares and canceling the gauge anomalies at the same time. As a result, we have a prediction for neutrino masses. The lighte…
It is proposed that supersymmetry (SUSY) maybe used to understand fermion mass hierarchies. A family symmetry Z_{3L} is introduced, which is the cyclic symmetry among the three generation SU(2) doublets. SUSY breaks at a high energy scale ~ 10^{11} GeV. The electroweak energy scale ~ 100 GeV is unnaturally small. No additional global symmetry, like the R-parity, is imposed. The Yukawa couplings and R-parity violating couplings all take their natural values which are about (10^0-10^{-2}). Under the family symmetry, only the third generation charged fermions get their masses. This family symmetr…
