Framework Of Left-right Symmetric Model Research Articles

Neutrinoless double beta decay and < η > mechanism in the left-right symmetric model

The neutrinoless double beta decay is studied in the framework of left-right symmetric model. The coexistence of left and right handed currents induces rather complicated interactions between the lepton and hadron sectors, called < λ > mechanism and < η > mechanism in addition to the conventional effective neutrino mass < mν > mechanism. In this letter, we study the possible magnification of < η > mechanism and the relatively vanishing of < λ > mechanism. The importance to survey 0νββ decay of different nuclei for specifying new physics beyond the Standard Model is also discussed.

Search for a right-handed gauge boson decaying into a high-momentum heavy neutrino and a charged lepton in pp collisions with the ATLAS detector at [formula omitted] TeV

A search for a right-handed gauge boson WR, decaying into a boosted right-handed heavy neutrino NR, in the framework of Left-Right Symmetric Models is presented. It is based on data from proton–proton collisions with a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the Large Hadron Collider during the years 2015, 2016 and 2017, corresponding to an integrated luminosity of 80 fb−1. The search is performed separately for electrons and muons in the final state. A distinguishing feature of the search is the use of large-radius jets containing electrons. Selections based on the signal topology result in smaller background compared to the expected signal. No significant deviation from the Standard Model prediction is observed and lower limits are set in the WR and NR mass plane. Mass values of the WR smaller than 3.8–5 TeV are excluded for NR in the mass range 0.1–1.8 TeV.

New physics signature in D^0 (bar{D}^0)rightarrow f effective width asymmetries

Violation of charge conjugation-parity (mathrm CP) symmetry plays a major rule in the dominance of matter in our universe. A kind of mathrm CP violation results from the asymmetry of the life time measured in M^0 and {bar{M}}^0, here M is a heavy meson, decays to final states which is referred in the literature as A_{Gamma }^f. In this paper, we give an estimation of the upper bound on |A_{Gamma }^f| for the Cabibbo Favored D^0 rightarrow K^- pi ^+ decay process in different models. We show that in the standard model, |A_{Gamma }^f| lesssim {mathcal {O}} (10^{-10}). Recently a bound on A_{Gamma }^f has been obtained: (A^f_{Gamma })^{Exp.}= (1.6 pm 1)times 10^{-4}. This result motivates further studies on A_{Gamma }^f in beyond standard model physics. In the framework of two Higgs doublet model with generic Yukawa structure, we show that |A_Gamma ^{f}|lesssim {mathcal {O}} (10^{-7}) which is several orders of magnitude smaller than the current experimental value. Finally, in the framework of left-right symmetric models in which the mixing between the left and the right gauge bosons is allowed and the left-right symmetry is not manifest at unification scale, we find that A_{Gamma }^f can be as large as |A_{Gamma }^f|lesssim {mathcal {O}} (10^{-5}) which is one order of magnitude smaller than the experimentally measured value by LHCb collaborators.

Phenomenology of two texture zero neutrino mass in left-right symmetric model with Z8 \xd7 Z2

We have done a phenomenological study on the neutrino mass matrix Mν favoring two zero texture in the framework of left-right symmetric model (LRSM) where type I and type II seesaw naturally occurs. The type I SS mass term is considered to be following a trimaximal mixing (TM) pattern. The symmetry realizations of these texture zero structures has been realized using the discrete cyclic abelian Z8 × Z2 group in LRSM. We have studied six of the popular texture zero classes named as A1, A2, B1, B2, B3 and B4 favoured by neutrino oscillation data in our analysis. We basically focused on the implications of these texture zero mass matrices in low energy phenomenon like neutrinoless double beta decay (NDBD) and lepton flavour violation (LFV) in LRSM scenario. For NDBD, we have considered only the dominant new physics contribution coming from the diagrams containing purely RH current and another from the charged Higgs scalar while ignoring the contributions coming from the left-right gauge boson mixing and heavy light neutrino mixing. The mass of the extra gauge bosons and scalars has been considered to be of the order of TeV scale which is accessible at the colliders.

Same-sign multilepton signatures of an SU(2)R quintuplet at the LHC

We study in detail the collider signatures of an SU(2)R fermionic quintuplet in the framework of left-right symmetric model in the context of the 13 TeV LHC. Apart from giving a viable dark matter candidate (χ0), this model provides unique collider imprints in the form of same-sign multileptons through the decays of multi-charged components of the quintuplet. In particular, we consider the scenario where the quintuplet carries (B − L) = 4 charge, allowing for the presence of high charge-multiplicity particles with relatively larger mass differences among them compared to (B − L) = 0 or 2. In this paper, we mainly focus on the same-sign n-lepton signatures (nSSL). We show that with an integrated luminosity of 500 fb−1, the mass of the neutral component, {M}_{chi^0} ≤ 480 (800) GeV can be excluded at 95% CL in the 2SSL (3SSL) channel after imposing several selection criteria. We also show that a 5σ discovery is also achievable if {M}_{chi^0} ≤ 390 (750) GeV in the 2SSL (3SSL) channel with 1000 fb−1 integrated luminosity.

Same sign versus opposite sign dileptons as a probe of low scale seesaw mechanisms

We calculate the ratio $R_{\ell\ell}$ of same sign (SS) to opposite sign (OS) dileptons in type I and generalized inverse seesaw models and show that it can be anywhere between 0 and 1 depending on the detailed texture of the right-handed neutrino mass matrix. Measurement of $R_{\ell\ell}$ in hadron colliders can therefore provide a way to probe the nature of seesaw mechanism and also to distinguish between the two types of seesaw mechanisms. We work within the framework of left-right symmetric model as an example. We emphasize that coherence of the final states in the $W_R$ decay is crucial for this discussion and it requires the right-handed neutrinos to be highly degenerate. We isolate the range of parameters in the model where this effect is observable at the LHC and future colliders.

Lepton number violation, lepton flavor violation, and baryogenesis in left-right symmetric model

We did a model independent phenomenological study of baryogenesis via leptogenesis, neutrinoless double beta decay (NDBD) and charged lepton flavour violation (CLFV) in a generic left-right symmetric model (LRSM) where neutrino mass originates from the type I + type II seesaw mechanism. We studied the new physics contributions to NDBD coming from the left-right gauge boson mixing and the heavy neutrino contribution within the framework of LRSM. We have considered the mass of the RH gauge boson to be specifically 5 TeV, 10 TeV and 18 TeV and studied the effects of the new physics contributions on the effective mass and baryogenesis and compared with the current experimental limit. We tried to correlate the cosmological BAU from resonant leptogenesis with the low energy observables, notably, NDBD and LFV with a view to finding a common parameter space where they coexists.

Neutrinoless Double Beta Decay and Lepton Flavour Violation in Broken μ − τ Symmetric Neutrino Mass Models

We have studied neutrinoless double beta decay and charged lepton flavour violation in broken $\mu-\tau$ symmetric neutrino masses in a generic left-right symmetric model (LRSM). The leading order $\mu-\tau$ symmetric mass matrix originates from the type I (II) seesaw mechanism, whereas the perturbations to $\mu-\tau$ symmetry in order for generation of non-zero reactor mixing angle $\theta_{13}$, as required by latest neutrino oscillation data, originates from the type II (I) seesaw mechanism. In our work, we considered four different realizations of $\mu-\tau$ symmetry, viz. Tribimaximal Mixing (TBM), Bimaximal Mixing (BM), Hexagonal Mixing (HM) and Golden Ratio Mixing (GRM). We then studied the new physics contributions to neutrinoless double beta decay (NDBD) ignoring the left-right gauge boson mixing and the heavy-light neutrino mixing within the framework of LRSM. We have considered the mass of the gauge bosons and scalars to be around TeV and studied the effects of the new physics contributions on the effective mass and the NDBD half life and compared with the current experimental limit imposed by KamLAND-Zen. We further extended our analysis by correlating the lepton flavour violation of the decay processes, $\left(\mu\rightarrow 3e\right)$ and $\left(\mu\rightarrow e\gamma\right)$ with the lightest neutrino mass and atmospheric mixing angle $\theta_{23}$ respectively.

Implications of the diphoton excess on left–right models and gauge unification

The recent diphoton excess signal at an invariant mass of 750 GeV can be interpreted in the framework of left-right symmetric models with additional scalar singlets and vector-like fermions. We propose a minimal scenario for such a purpose. Extending the LRSM framework to include these new vector-like fermionic fields, on the other hand, results in interesting phenomenological implications for the LRSM fermion masses and mixing. Furthermore, existence of such vector-like fermions can also have interesting implications for baryogenesis and the dark matter sector. The introduction of a real bi-triplet scalar which contains a potential DM candidate will allow the gauge couplings to unify at $\approx 10^{17.7}$ GeV.

Neutrino masses and leptogenesis in type I and type II seesaw models

The baryon to photon ratio in the present Universe is very accurately measured to be $(6.065\ifmmode\pm\else\textpm\fi{}0.090)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$. We study the possible origin of this baryon asymmetry in the neutrino sector through the generic mechanism of baryogenesis through leptogenesis. We consider both the type I and type II seesaw origin of neutrino masses within the framework of left-right symmetric models (LRSM). Using the latest best-fit global neutrino oscillation data of mass squared differences, mixing angles and Dirac $CP$ phase, we compute the predictions for baryon to photon ratio keeping the Majorana $CP$ phases as free parameters for two different choices of lightest neutrino mass eigenvalue for both normal and inverted hierarchical patterns of neutrino masses. We do our calculation with and without lepton flavor effects being taken into account. We choose different diagonal Dirac neutrino mass matrix for different flavor effects in such a way that the lightest right-handed neutrino mass is in the appropriate range. We also study the predictions for baryon asymmetry when the neutrino masses arise from a combination of both type I and type II seesaw (with dominating type I term) and discriminate between several combinations of Dirac and Majorana $CP$ phases by demanding successful predictions for baryon asymmetry.

Spontaneous parity breaking, gauge coupling unification, and consistent cosmology with transitory domain walls

The formation of transitory domain walls is quite generic in theories with spontaneous breaking of discrete symmetries. Since these walls are in conflict with cosmology, there has to be some mechanism which makes them disappear. We study one such mechanism by incorporating Planck-scale suppressed operators within the framework of left-right symmetric models where left-right parity (D parity) is spontaneously broken. We find that this mechanism cannot make the walls disappear in minimal versions of left-right symmetric models. We propose two viable extensions of this model and show that Planck-scale suppressed operators can give rise to the successful disappearance of domain walls provided the scale of parity breaking obeys certain limits. We also constrain the scale of parity breaking by demanding successful gauge-coupling unification and make a comparison of the unification and cosmology bounds.

Limits on right-handed charged weak currents from a polarization-asymmetry correlation experiment with 107In.

A new technique, based on relative measurements of the longitudinal polarization (P) of positrons emitted in two opoosite directions with respect to the nuclear polarization (R=${\mathit{P}}^{\mathrm{\ensuremath{-}}}$/${\mathit{P}}^{+}$), is used to provide constraints on extensions of the standard model (${\mathit{R}}_{0}$). The first result, i.e., R/${\mathit{R}}_{0}$=0.926\ifmmode\pm\else\textpm\fi{}0.041, was obtained with $^{107}\mathrm{In}$. Interpreted in the framework of left-right symmetric models and assuming no mixing, it provides a 90% C.L. lower limit of 225 GeV/${\mathit{c}}^{2}$ for the mass of a possible right-handed charged W gauge boson, reducing the mass range allowed by other semileptonic experiments.

Search for right handed coupling in nu -N scattering.

The relative absence of \ensuremath{\nu}${\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}_{\mathrm{\ensuremath{\mu}}}$-induced charged current events with respect to ${\ensuremath{\nu}}_{\mathrm{\ensuremath{\mu}}}$-induced events at large (g0.45) and large y (g0.70) enables us to limit the right handed coupling of the weak current. Our data restrict \ensuremath{\Vert}\ensuremath{\eta}${\mathrm{\ensuremath{\Vert}}}^{2}$=\ensuremath{\Vert}${\mathit{g}}_{\mathit{R}}$/${\mathit{g}}_{\mathit{L}}$${\mathrm{\ensuremath{\Vert}}}^{2}$0.0 015 with 90% C.L. Within the framework of left-right symmetric models, this measurement imposes a limit upon the mixing angle of the left and right handed bosons. Unlike the limits imposed by the \ensuremath{\mu}-decay and nuclear \ensuremath{\beta}-decay experiments, our limit is valid irrespective of the mass of the right handed neutrino.

Is there an indication for the existence of right-handed weak currents in nuclear beta decay?

The authors examine recent claims that experiments on neutron-decay are at variance with the standard V-A helicity structure of the standard model. The analysis presented here combines the neutron data with other recent experimental results and theoretical elaborations in the field of nuclear beta decay. If interpreted in the framework of left-right symmetric models, the data favour the existence of a right-handed weak gauge boson with mass between 207 and 369 GeV c2 at 95% CL. The fit using the standard V-A helicity structure has a chi 2 of 8.52 for four degrees of freedom and excludes the V-A solution at 2.53 standard deviations. This exclusion is due mainly to the new neutron asymmetry data and is in disagreement with the conclusions drawn from muon decay and from the KL-KS mass difference in the framework of manifest left-right symmetric models.

Lorentz structure of weak current in ν interactions and inverse muon decay

Neutrino interactions uniquely convey the Lorentz structure of weak current. Two studies that probe this structure are reviewed: structure functions from ν μ − and ν μ − induced charged current events; and the inverse muon decay process, ν μ +e −→ μ −+ ν e. In the first study, the relative absence of ν μ -induced charged current events with respect to ν μ -induced events at large z (> 0.45) and large y (> 0.70) (investigated by CDHS and CCFR) restricts |η| 2 = |g R/g L| 2 < 0.0015 with 90 % CL (CCFR). Within the framework of left-right symmetric models, this measurement imposes a limit upon the mixing angle of the left and right handed bosons. Unlike the limits imposed by the μ-decay and the nuclear β-decay experiments, the present limit is valid irrespective of the mass of the right handed neutrino. In the second study, recent high statistics measurements of inverse muon decay by CCFR and CHARM II yield a total cross section, σ( ν μ +e −→ μ −+ ν e) = (17.3±0.72(stat)±0.39(syst)]E ν 10 −42 cm 2/GeV. This restricts the scalar coupling of the muon | g LL S | < 0.25 with 90% CL.