<p>We explore constraints on the parameter space of the alternative left-right model originating from the leptonic sector. Our analyses focuses on both lepton-flavor-conserving observables, particularly the anomalous magnetic moment of the muon, and lepton-flavor-violating processes like <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>μ</mi><mo stretchy="false">→</mo><mi>e</mi><mi>γ</mi></math> decay and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>μ</mi><mo>−</mo><mi>e</mi></math> conversions in nuclei. While contributions to the anomalous magnetic moment fall below the measured values at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>2</mn><mi>σ</mi></mrow></math>, current and future experimental sensitivities to flavor-violating branching rations of the Standard Model leptons are expected to impose lower bounds on the mass of the peculiar <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>2</mn><msub><mo stretchy="false">)</mo><mi>R</mi></msub></math> gauge boson of the model. This provides complementary constraints relative to existing limits, which are indirect and derived from collider bounds on the mass of the associated neutral gauge boson <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mo>′</mo></msup></math>.</p>

Canada

Mariana Frank

France

India

Benjamin Fuks

Sumit K. Garg

United Kingdom

Chayan Majumdar

Poulose Poulose

United States

Supriya Senapati

Leptonic probes of alternative left-right symmetric models

The Alternative Left-Right Model is an attractive variation of the usual Left-Right Symmetric Model because it avoids flavour-changing neutral currents, thus allowing the additional Higgs bosons in the model to be light. We show here that the model predicts several dark matter candidates naturally, through introduction of an R-parity similar to the one in supersymmetry, under which some of the new particles are odd, while all the SM particles are even. Dark matter candidates can be fermionic or bosonic. We present a comprehensive investigation of all possibilities. We analyze and restrict the parameter space where relic density, direct and indirect detection bounds are satisfied, and investigate the possibility of observing fermionic and bosonic dark matter signals at the LHC. Both the bosonic and fermionic candidates provide promising signals, the first in LHC at 300 fb −1, the second at higher luminosity, 3000 fb −1. Signals from bosonic candidates are indicative of the presence of exotic d′ quarks, while fermionic candidates imply the existence of charged Higgs bosons, all with masses in the TeV region.

Türkiye

Urjit Yajnik

Dark matter in the Alternative Left Right model

We consider an <math><mi>U</mi><msub><mrow><mo>(</mo><mn>1</mn><mo>)</mo></mrow><mrow><msub><mrow><mi>L</mi></mrow><mrow><mi>μ</mi></mrow></msub><mo>−</mo><msub><mrow><mi>L</mi></mrow><mrow><mi>τ</mi></mrow></msub></mrow></msub></math> extended left-right symmetric gauge theory where the neutrino masses are generated through inverse seesaw mechanism. In this model the muon <math><mo>(</mo><mi>g</mi><mo>−</mo><mn>2</mn><mo>)</mo></math> anomaly is accounted for by the mediation of <math><msub><mrow><mi>Z</mi></mrow><mrow><mi>μ</mi><mi>τ</mi></mrow></msub></math>, the gauge boson of <math><mi>U</mi><msub><mrow><mo>(</mo><mn>1</mn><mo>)</mo></mrow><mrow><msub><mrow><mi>L</mi></mrow><mrow><mi>μ</mi></mrow></msub><mo>−</mo><msub><mrow><mi>L</mi></mrow><mrow><mi>τ</mi></mrow></msub></mrow></msub></math> symmetry. The symmetries of the model require the light neutrino mass matrix to have a particular two-zero texture, which leads to non-trivial constraints in the minimum neutrino mass. In addition, the model predicts observable charged lepton flavor violation in <math><mi>μ</mi><mo>−</mo><mi>τ</mi></math> sector.

S. Uma Sankar

Urjit A. Yajnik

Neutrino mass and charged lepton flavor violation in an extended left-right symmetric 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 E 6, while its low energy Higgs structure resembles the LRSM, involving Higgs doublets χ  L,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.

Vacuum structure of Alternative Left-Right Model

We investigate the possibility of neutrinoless double beta decay (<math><mn>0</mn><mi>ν</mi><mi>β</mi><mi>β</mi></math>) 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 <math><mn>0</mn><mi>ν</mi><mi>β</mi><mi>β</mi></math> through vector-scalar (<math><mi>W</mi><mi>H</mi></math>) mediation. For moderate masses of the relevant charged Higgs boson (<math><msub><mi>M</mi><msubsup><mi>H</mi><mn>1</mn><mo>±</mo></msubsup></msub><mo>∼</mo><mn>200</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>), the half-life of <math><msubsup><mi>T</mi><mfrac><mn>1</mn><mn>2</mn></mfrac><mrow><mi>W</mi><mi>H</mi></mrow></msubsup></math> is <math><mo>∼</mo><mn>3</mn><mo>×</mo><msup><mn>10</mn><mn>26</mn></msup><mtext> </mtext><mtext> </mtext><mi>yrs</mi></math> for both the case of <math><mrow><mmultiscripts><mrow><mi>Ge</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>76</mn></mrow></mmultiscripts></mrow></math> and <math><mrow><mmultiscripts><mrow><mi>Xe</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>136</mn></mrow></mmultiscripts></mrow></math>, well within the sensitivity expected by future experiments. Invoking the resonant leptogenesis, <math><mi>C</mi><mi>P</mi></math> violation arising from the right-handed neutrino decay could be the required order to generate the correct baryogenesis, <math><mi>ε</mi><mo>∼</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>6</mn></mrow></msup></math>, for small Dirac phases and without any fine tuning.

P. Poulose

Exploring <math><mrow><mn>0</mn><mi>ν</mi><mi>β</mi><mi>β</mi></mrow></math> and leptogenesis in the alternative left-right model

We consider a gauged   <math> <mi>U</mi> <msub> <mfenced> <mn>1</mn> </mfenced> <mrow> <msub> <mi>L</mi> <mi>μ</mi> </msub> <mo>−</mo> <msub> <mi>L</mi> <mi>τ</mi> </msub> </mrow> </msub> </math>  $$ \mathrm{U}{(1)}_{L_{\mu }-{L}_{\tau }} $$  extension of the left-right symmetric theory in order to simultaneously explain neutrino mass, mixing and the muon anomalous magnetic moment. We get sizeable contribution from the interaction of the new light gauge boson Z  μτ  of the   <math> <mi>U</mi> <msub> <mfenced> <mn>1</mn> </mfenced> <mrow> <msub> <mi>L</mi> <mi>μ</mi> </msub> <mo>−</mo> <msub> <mi>L</mi> <mi>τ</mi> </msub> </mrow> </msub> </math>  $$ \mathrm{U}{(1)}_{L_{\mu }-{L}_{\tau }} $$  symmetry with muons which can individually satisfy the current bounds on muon (g − 2) anomaly (∆a  μ ). The other positive contributions to ∆a  μ  come from the interactions of singly charged gauge bosons W  L , W  R  with heavy neutral fermions and that of neutral CP-even scalars with muons. The interaction of W  L  with heavy neutrino is facilitated by inverse seesaw mechanism which allows large light-heavy neutrino mixing and explains neutrino mass in our model. CP-even scalars with mass around few hundreds GeV can also satisfy the entire current muon anomaly bound. The results show that the model gives a small but non-negligible contribution to ∆a  μ  thereby eliminating the entire deviation in theoretical prediction and experimental result of muon (g − 2) anomaly. We have briefly presented a comparative study for symmetric and asymmetric left-right symmetric model in context of various contribution to ∆a  μ . We also discuss how the generation of neutrino mass is affected when left-right symmetry breaks down to Standard Model symmetry via various choices of scalars.

Sudhanwa Patra

Prativa Pritimita

Neutrino mass, mixing and muon g − 2 explanation in   <math> <mi>U</mi> <msub> <mfenced> <mn>1</mn> </mfenced> <mrow> <msub> <mi>L</mi> <mi>μ</mi> </msub> <mo>−</mo> <msub> <mi>L</mi> <mi>τ</mi> </msub> </mrow> </msub> </math>  $$ \mathrm{U}{(1)}_{L_{\mu }-{L}_{\tau }} $$  extension of left-right theory

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

A comparative study of 0 Decay in Symmetric and Asymmetric Left-right Model

We consider a version of Left-Right Symmetric Model in which the scalar sector consists of a Higgs bidoublet (Φ) with <math><mi>B</mi><mo>−</mo><mi>L</mi><mo>=</mo><mn>0</mn></math>, Higgs doublets (<math><msub><mrow><mi>H</mi></mrow><mrow><mi>L</mi><mo>,</mo><mi>R</mi></mrow></msub></math>) with <math><mi>B</mi><mo>−</mo><mi>L</mi><mo>=</mo><mn>1</mn></math> and a charged scalar (<math><msup><mrow><mi>δ</mi></mrow><mrow><mo>+</mo></mrow></msup></math>) with <math><mi>B</mi><mo>−</mo><mi>L</mi><mo>=</mo><mn>2</mn></math> leading to radiatively generated Majorana masses for neutrinos and thereby, leads to new physics contributions to neutrinoless double beta decay (<math><mn>0</mn><mi>ν</mi><mi>β</mi><mi>β</mi></math>). We show that such a novel framework can be embedded in a non-SUSY <math><mi>S</mi><mi>O</mi><mo>(</mo><mn>10</mn><mo>)</mo></math> GUT leading to successful gauge coupling unification at around 10$^{16}$ GeV with the scale of left-right symmetry breaking around 10$^{10}$ GeV. The model can also be extended to have left-right symmetry breaking at TeV scale, enabling detection of <math><msub><mrow><mi>W</mi></mrow><mrow><mi>R</mi></mrow></msub><mo>,</mo><msub><mrow><mi>Z</mi></mrow><mrow><mi>R</mi></mrow></msub></math> bosons in LHC and future collider searches. In the context of neutrinoless double beta decay, this model can saturate the present bound from GERDA and KamLAND-Zen experiments. Also, we briefly explain how keV-MeV range RH neutrino arising from our model can saturate various astrophysical and cosmological constraints and can be considered as warm Dark Matter (DM) candidate to address various cosmological issues. We also discuss on left-right theories with Higgs doublets without having scalar bidoublet leading to fermion masses and mixings by inclusion of vector like fermions.