Left-right Model Research Articles

Vacuum structure of Alternative Left-Right Model

We investigate an Alternative Left-Right Model (ALRM) with SU(2)L as well as SU(2)R gauge groups, but unlike the traditional left-right symmetric models (LRSM) is not symmetric under the exchange of the fermion content. Interestingly, it can be embedded in E6, while its low energy Higgs structure resembles the LRSM, involving Higgs doublets χL,R and one Higgs bidoublet Φ. We analyze the scalar potential and the vacuum structure of the theory analytically to ensure the stability of scalar potential via bounded from below (BFB) and copositivity criteria, accompanied by a numerical study. We establish the necessary criteria for electric charge-preserving vacua, yielding constraints on various coupling parameters of the theory. Finally we obtain constraints on the parameters of the model from collider data on the masses of the Higgs scalars.

Single top production via FCNC couplings at an $$e^{-}e^{+}$$ collider with center-of-mass energy $$\sqrt{s}=240$$ GeV

Aspects of top quark physics can be studied at a future Circular Electron-Positron Collider. In particular, flavor-changing neutral current interactions (FCNC) of the top quark can be studied even with a center-of-mass energy from \(\sqrt{s}\gtrsim m_t\) to \(\sqrt{s}=240\) GeV, through the production a single top quark in association with a charm quark, which can arise in several scenarios of new physics. We explore here this signal within the Left-Right Mirror Model, which is a Left-Right model that includes mirror fermions; this model is motivated as a possible solution to the strong CP problem and by its rich phenomenology. We find that for particular scenarios of the model parameters, which are in agreement with the most up-to-date experimental constraints, the signal coming from the process \(e^+e^-\rightarrow V \rightarrow tc\) (\(V=Z,\,Z^{\prime }\)) provides a detectable signal and thus, it can give evidence for FCNC interactions; in these scenarios, the mass of a new neutral gauge boson can be as high as \(m_{Z'}=7\) TeV.

Leptogenesis and low-energy CP violation in a type-II-dominated left-right seesaw model

We consider leptogenesis in a left-right-symmetric seesaw scenario in which neutrino mass generation and leptogenesis are dominated by the type-II seesaw term. Motivated by grand unification, we assume that the neutrino Dirac mass matrix is dominated by a single entry of the order of the top-quark mass, which leaves the low-energy phases of the lepton mixing matrix as the only sources of CP violation. Working in a regime where the triplet scalar predominantly decays into leptons, this results in a predictive scenario based on a minimal number of parameters. We perform a detailed analysis of the flavored Boltzmann equations within a revised density matrix framework and demonstrate that the observed baryon asymmetry can be successfully generated in this simple model. We point out that the significance of flavor effects is limited, and we discuss the implications for low-energy observables such as the Dirac CP phase and neutrinoless double beta decay.

Search for a heavy neutral Higgs boson in a left-right model with an inverse seesaw mechanism at the LHC

We develop a low scale left-right symmetric model based on $SU(3)_C\times SU(2)_L\times SU(2)_R\times U(1)_{B-L}\times Z_2$ with a simplified Higgs sector consisting of only one bidoublet and one $SU(2)_R$ doublet. In this model, the tiny values of light neutrino masses are generated through an inverse-seesaw mechanism. We emphasize that in this setup, the tree-level flavor changing neutral current can be strongly suppressed, consistent with the current experimental constraints. We show that the lightest $CP$-even Higgs boson, which is like the standard model Higgs boson, and the next lightest Higgs boson, $h'$, are generated from the neutral components of the bidoublet. We show that the mass of the next lightest Higgs boson can be of an order a few hundred~\text{GeVs}. We analyze the detection of $h'$ at the Large Hadron Collider (LHC) for a center-of-mass energy $\sqrt{s}=14~\text{TeV}$ and integrated luminosity $L_{\text{int}}=300~{\text{fb}}^{-1}$ via di-Higgs channel: $h'\to hh\to b\bar{b}\gamma\gamma$ and also in the $ZZ$ channel: $h'\to ZZ\to 4\ell~(\ell=e,~\mu)$ at an integrated luminosity $L_{\text{int}}=3000~{\text{fb}}^{-1}$. We consider three benchmark points for this analysis with $m_{h'}=250~\text{GeV},~400~\text{GeV}$, and $600~\text{GeV}$. We show that promising signals with good statistical significances can be obtained in di-Higgs channel, with $2\gamma+2b$-jets final states.

Higgs flavor phenomenology in a supersymmetric left-right model with parity

In this paper, we focus on the supersymmetric model with left-right (LR) symmetry, that is especially proposed in our previous work [1]. In this model, there are four Higgs doublets in order to realize the Standard Model (SM) fermion masses and the Cabibbo-Kobayashi-Maskawa matrix. The heavy Higgs doublets unavoidably have flavor changing couplings to the SM fermions and induce flavor-changing neutral currents at tree level. We study broader parameter space than the previous work with including the renormalization group corrections to the Yukawa couplings between the LR breaking scale, mathcal{O} (1013) GeV, and the supersymmetry breaking scales, mathcal{O} (100) TeV. The CP violating observable in K– overline{K} mixing, ϵK, strongly constrains the model, so that heavy Higgs mass should be heavier than mathcal{O} (100) TeV. We study the lepton flavor violating (LFV) processes setting heavy Higgs masses to be 170 TeV. The branching ratios of μ → 3e and the μ–e conversion can be larger than 10−16 that could be covered by the future experiments. We also study the degree of fine-tuning in the parameter region that predicts testable LFV processes.

Universal scotogenic fermion masses in left-right gauge model

In the conventional left-right gauge model, if the Higgs scalar sector consists only of an SU(2)L doublet and an SU(2)R doublet, fermion masses are zero at tree level. There have been many studies on how they would become massive. With the help of a dark sector with U(1)D gauge symmetry, it is shown how all standard-model fermions may acquire realistic masses radiatively, including that of the top quark. In this context, the particle content of the model also implies the automatic conservation of baryon number B and lepton number L as in the standard model. Observable anomalous Higgs couplings are predicted.

CP violating hW+W\u2212 coupling in the Standard Model and beyond

Inspired by the recent development in determining the property of the observed Higgs boson, we explore the CP-violating (CPV) -{c}_{mathrm{CPV}}{hW}^{+mu nu}{tilde{W}}_{mu nu}^{-}/upsilon coupling in the Standard Model (SM) and beyond, where W±μν and {tilde{W}}^{pm mu nu} denote the W-boson field strength and its dual. To begin with, we show that the leading-order SM contribution to this CPV vertex appears at two-loop level. By summing over the quark flavor indices in the two loop integrals analytically, we can estimate the order of the corresponding Wilson coefficient to be {c}_{mathrm{CPV}}^{mathrm{SM}}sim mathcal{O}left({10}^{-23}right) , which is obviously too small to be probed at the LHC and planned future colliders. Then we investigate this CPV hW+W− interaction in two Beyond the Standard Model benchmark models: the left-right model and the complex 2-Higgs doublet model (C2HDM). Unlike what happens for the SM, the dominant contributions in both models arise at the one-loop level, and the corresponding Wilson coefficient can be as large as of mathcal{O} (10−9) in the former model and of mathcal{O} (10−3) for the latter. In light of such a large CPV effect in the hW+W− coupling, we also give the formulae for the leading one-loop contribution to the related CPV hZZ effective operator in the complex 2-Higgs doublet model. The order of magnitude of the Wilson coefficients in the C2HDM may be within reach of the high-luminosity LHC or planned future colliders.

Pembangkitan Massa Medan Skalar dan Boson Tera pada Model Simetri Kiri Kanan Termodifikasi Berdasarkan Grup Tera SU(3)_C⊗SU(2)_L⊗SU(2)_R⊗U(1)_Y

Modified Left-Right Symmetry Model has been constructed based on  the gauge group . In this model there is a left sector consisting of Standard Model particles with the addition of right-handed neutrino  and the doublet scalar , while the particle pairs are in the right sector. In addition, also added scalar fields  and  which can be intermediaries of interaction between the two sectors. Scalar fields masses can be generated via scalar potensial with the result that  . Whereas the mass of charged gauge bosons , the masses of neutral gauge bosons masses and the mass of photon is zero.

Exploring 0νββ and leptogenesis in the alternative left-right model

We investigate the possibility of neutrinoless double beta decay ($0\nu\beta\beta$) and leptogenesis within the Alternative Left-Right Model (ALRM). Unlike the usual left-right symmetric model, ALRM features a Majorana right-handed neutrino which does not carry any charge. Further, in this picture the down-type quark and the charged leptons receive mass through the additional left-handed scalar field, rather than the usual doublet. Together, these features conspire to generate significant contributions to the $0\nu\beta\beta$ through vector-scalar ($WH$) mediation. For moderate masses of the relevant charged Higgs boson ($M_{H_1^\pm}\sim 200$ GeV), the half-life of $T_{\frac{1}{2}}^{WH}$ is $\sim 3\times 10^{26}~{\rm yrs}$ for both the case of $^{76}$Ge and $^{136}$Xe, well within the sensitivity expected by future experiments. Invoking the resonant leptogenesis, CP violation arising from the right-handed neutrino decay could be the required order to generate the correct baryogenesis, $\epsilon\sim 10^{-6}$, for small Dirac phases and without any fine tuning.

Constraining the gauge and scalar sectors of the doublet left-right symmetric model

We consider a left-right symmetric extension of the Standard Model where the spontaneous breakdown of the left-right symmetry is triggered by doublets. The electroweak ρ parameter is protected from large corrections in this Doublet Left-Right Model (DLRM), contrary to the triplet case. This allows in principle for more diverse patterns of symmetry breaking. We consider several constraints on the gauge and scalar sectors of DLRM: the unitarity of scattering processes involving gauge bosons with longitudinal polarisations, the radiative corrections to the muon ∆r parameter and the electroweak precision observables measured at the Z pole and at low energies. Combining these constraints within the frequentist CKMfitter approach, we see that the fit pushes the scale of left-right symmetry breaking up to a few TeV, while favouring an electroweak symmetry breaking triggered not only by the SU(2)L×SU(2)R bi-doublet, which is the case most commonly considered in the literature, but also by the SU(2)L doublet.

The Left-Right Symmetry Breaking Mechanism for the New Left-Right Symmetry Model

We added a mechanism for breaking the left-right (LR) symmetry in the new variant of the left-right symmetry model. We added to the modela new scalar field ϕ that transforms oddly under the new LR transformation. The mechanism can provide different values for the vacuum expectation values of the left and right Higgs scalar, ν L , and ν R . A simple numerical analysis was performed to make sure that the parameters space in this model can satisfy some constraints of the model. It is shown that for some parameter values, this mechanism can fulfill the constraint of ν L = 246 GeV and the ratio ν R ⁄ν L >30. DOI: http://dx.doi.org/10.17977/um024v5i12020p001

Observing left-right symmetry in the cosmic microwave background

We consider the possibility of probing left-right symmetric model (LRSM) via cosmic microwave background (CMB). We adopt the minimal LRSM with Higgs doublets, also known as the doublet left-right model (DLRM), where all fermions including the neutrinos acquire masses only via their couplings to the Higgs bidoublet. Due to the Dirac nature of light neutrinos, there exist additional relativistic degrees of freedom which can thermalise in the early universe by virtue of their gauge interactions corresponding to the right sector. We constrain the model from Planck 2018 bound on the effective relativistic degrees of freedom and also estimate the prospects for planned CMB Stage IV experiments to constrain the model further. We find that $W_R$ boson mass below 4.06 TeV can be ruled out from Planck 2018 bound at $2\sigma$ CL in the exact left-right symmetric limit which is equally competitive as the LHC bounds from dijet resonance searches. On the other hand Planck 2018 bound at $1\sigma$ CL can rule out a much larger parameter space out of reach of present direct search experiments, even in the presence of additional relativistic degrees of freedom around the TeV corner. We also study the consequence of these constraints on dark matter in DLRM by considering a right handed real fermion quintuplet to be the dominant dark matter component in the universe.

A comparative study of 0νββ decay in symmetric and asymmetric left-right model

We study the new physics contributions to neutrinoless double beta decay (0νββ) in a TeV scale left-right model with spontaneous D-parity breaking mechanism where the values of the SU(2)L and SU(2)R gauge couplings, gL and gR are unequal. Neutrino mass is generated in the model via gauge extended inverse seesaw mechanism. We embed the model in a non-supersymmetric SO(10) GUT with a purpose of quantifying the results due to the condition gL≠gR. We compare the predicted numerical values of half life of 0νββ decay, effective Majorana mass parameter and other lepton number violating parameters for three different cases; (i) for manifest left-right symmetric model (gL=gR), (ii) for left-right model with spontaneous D parity breaking (gL≠gR), (iii) for Pati-Salam symmetry with D parity breaking (gL≠gR). We show how different contributions to 0νββ decay are suppressed or enhanced depending upon the values of the ratio gRgL that are predicted from successful gauge coupling unification.

CP violating effects in heavy neutrino oscillations: implications for colliders and leptogenesis

Two of the important implications of the seesaw mechanism are: (i) a simple way to understand the small neutrino masses, and (ii) the origin of matter-anti-matter asymmetry in the universe via the leptogenesis mechanism. For TeV-scale seesaw models, successful leptogenesis requires that the right-handed neutrinos (RHNs) must be quasi-degenerate and if they have CP violating phases, they also contribute to the CP asymmetry. We investigate this in the TeV-scale left-right models for seesaw and point out a way to probe the quasi-degeneracy possibility with CP violating mixings for RHNs in hadron colliders using simple observables constructed out of same-sign dilepton charge asymmetry (SSCA). In particular, we isolate the parameter regions of the model, where the viability of leptogenesis can be tested using the SSCA at the Large Hadron Collider, as well as future 27 TeV and 100 TeV hadron colliders. We also independently confirm an earlier result that there is a generic lower bound on the WR mass of about 10 TeV for leptogenesis to work.

Anatomy of heavy gauge bosons in a left-right supersymmetric model

We perform a detailed study of the various decay channels of the heavy charged and neutral gauge bosons ($W_R$ and $Z_R$ respectively) in a left-right supersymmetric (LRSUSY) framework. The decay branching ratios of the $W_R$ and $Z_R$ bosons depend significantly on the particle spectrum and composition of the SUSY states. We show several combinations of mass spectrum for the SUSY particles to facilitate the decay of these heavy gauge bosons into various combinations of final states. Finally, we choose two benchmark points and perform detailed collider simulations for these heavy gauge bosons in the context of the high energy and high luminosity run of the large hadron collider. We analyze two SUSY cascade decay channels -- mono-$W$ + $\slashed{E}_T$ and mono-$Z$ + $\slashed{E}_T$ along with the standard dilepton and dijet final states. Our results show that the existence of these heavy gauge bosons can be ascertained in the direct decay channels of dilepton and dijet whereas the other two channels will be required to establish the supersymmetric nature of this model.

Muon g-2 anomaly confronted with the higgs global data in the left-right twin Higgs models

We will examine the muon g-2 anomaly with the background of the Higgs global fit data in the framework of the Left-Right Twin Higgs (LRTH) Models. The joint constrains of the precision electroweak data, the 125 GeV Higgs data, the leptonic flavor changing decay mu rightarrow egamma decays, and the mass requirement of the right-handed neutrino nu _R, the vector-like top partner T and the heavy gauge boson W_H, m_{nu _R}>m_T>m_{W_H}, are all considered in our calculation. Furthermore, since the neutral scalar phi ^0 may be lighter than the 125 GeV Higgs, the direct searches from the hrightarrow phi ^0phi ^0 channels can impose stringent upper limits on Br(hrightarrow phi ^0phi ^0), which will reduce the allowed region of m_{phi ^0} and f, the vacuum expectation value of the SM right-handed Higgs H_R. It is concluded that the muon g-2 anomaly can be explained in the region of 700 GeV le fle 1100 GeV, 13 GeV le m_{phi ^0}le 55 GeV, 100 GeV le m_{phi ^pm }le 900 GeV, m_{nu _R}ge 15 TeV, and 200 GeV le Mle 800 GeV, after imposing all the constraints mentioned above, where M here means the mass mixing coefficient M bar{q}_Lq_R, allowed by gauge invariance.

Natural quark mixing and inverse seesaw in a left-right model with an axion

We consider a minimal left-right model with a Peccei-Quinn symmetry, where generalised charge conjugation plays the role of the left-right symmetry. We show how the spontaneous breaking of the Peccei-Quinn symmetry by a scalar singlet can provide us with solutions not only to the strong CP and dark matter problems but can also help to generate naturally suppressed off-diagonal CKM elements and small neutrino masses via the inverse seesaw mechanism. For this, we make use of an economical scalar sector composed of a bi-doublet, two doublets and a singlet only. As a result of the new gauge bosons and neutrinos, the neutrinoless double beta decay, as well as lepton flavour violating processes, receives new contributions which can, in principle, become relevant due to the low-scale nature of the inverse seesaw mechanism. The model can easily accommodate all the current data on fermion masses and mixing even if the left-right scale is only high enough to evade the current experimental constraints.

Flavor changing in the flipped trinification

The flipped trinification, a framework for unifying the 3-3-1 and left-right symmetries, has recently been proposed in order to solve profound questions, the weak parity violation and the number of families, besides the implication for neutrino mass generation and dark matter stability. In this work, we argue that this gauge-completion naturally provides flavor-changing neutral currents in both quark and lepton sectors. The quark flavor changing happens at the tree-level due to the nonuniversal couplings of $Z'_{L,R}$, while the lepton flavor changing $l\rightarrow l'\gamma$ starts from the one loop level contributed significantly by the new charged currents of $Y_{L,R}$, which couple ordinary to exotic leptons. These effects disappear in the minimal left-right model, but are present in the framework characterizing a flipped trinification symmetry.

Perturbativity constraints on U(1)B\u2212L and left-right models and implications for heavy gauge boson searches

We derive perturbativity constraints on beyond standard model scenarios with extra gauge groups, such as SU(2) or U(1), whose generators contribute to the electric charge, and show that there are both upper and lower limits on the additional gauge couplings, from the requirement that the couplings remain perturbative up to the grand unification theory (GUT) scale. This leads to stringent constraints on the masses of the corresponding gauge bosons and their collider phenomenology. We specifically focus on the models based on SU{(2)}_L times U{(1)}_{I_{3R}} times U{(1)}_{B-L} and the left-right symmetric models based on SU(2)L × SU(2)R × U(1)B − L, and discuss the implications of the perturbativity constraints for new gauge boson searches at current and future colliders. In particular, we find that the stringent flavor constraints in the scalar sector of left-right model set a lower bound on the right-handed scale vR ≳ 10 TeV, if all the gauge and quartic couplings are to remain perturbative up to the GUT scale. This precludes the prospects of finding the ZR boson in the left-right model at the LHC, even in the high-luminosity phase, and leaves only a narrow window for the WR boson. A much broader allowed parameter space, with the right-handed scale vR up to ≃ 87 TeV, could be probed at the future 100 TeV collider.

Probing TeV scale origin of neutrino mass at future lepton colliders via neutral and doubly-charged scalars

We point out how future lepton colliders can provide unique insight into the scalar sector of TeV scale models for neutrino masses with local $B-L$ symmetry. Our specific focus is on the TeV scale left-right model, which naturally embeds this $B-L$ symmetry. In particular, we make a detailed study of the lepton collider implications of the neutral ($H_3$) and doubly-charged ($H^{\pm\pm}$) scalars from the right-handed triplet Higgs that is responsible for the spontaneous breaking of the $B-L$ symmetry and implementing the seesaw mechanism. Due to mixing with other scalars, the neutral scalar $H_3$ could acquire sizable flavor violating couplings to the charged leptons. Produced on-shell or off-shell at the planned $e^+e^-$ colliders, it would induce distinct lepton flavor violating signals like $e^+e^- \to \mu^\pm \tau^\mp ~ (+H_3)$, with the couplings probed up to $\sim 10^{-4}$ for a wide range of neutral scalar mass, which is well beyond the reach of current searches for charged lepton flavor violation. The Yukawa couplings of the doubly-charged scalar $H^{\pm\pm}$ to the charged leptons might also be flavor-violating, which is correlated to the heavy right-handed neutrino masses and mixings. With a combination of the pair, single and off-shell production of $H^{\pm\pm}$ like $e^+e^- \to H^{++} H^{--},\, H^{\pm\pm} e^\mp \mu^\mp,\, \mu^\pm \tau^\mp$, the Yukawa couplings can be probed up to $10^{-3}$ at future lepton colliders, which is allowed by current lepton flavor data in a large region of parameter space. For both the neutral and doubly-charged cases, the scalar masses could be probed up to the few-TeV range in the off-shell channel.