TeV scale universal seesaw, vacuum stability and heavy Higgs

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Abstract:We point out that a class of non-supersymmetric models based on the gauge group SU(3) C × SU(2) L × SU(2) R × U(1) Y L × U(1) Y R possesses an automatic, exact Z 2 symmetry under which the fermions in the SU(2) R × U(1) Y R sector (called R-sector) are odd and those in the SU(2) L ×U(1) Y L sector (called L-sector or the Standard Model sector) are even. This symmetry, which is different from the usual parity symmetry of the leftright symmetric models, persists in the lepton sector even after the gauge symmetry breaks down to SU(3) C × U(1) EM . This keeps the lightest right-handed neutrino naturally stable, thereby allowing it to play the role of dark matter (DM) in the Universe. There are several differences between the usual left-right models and the model presented here: (i) our model can have two versions, one which has no parity symmetry so that the couplings and masses in the L and R sectors are unrelated, and another which has parity symmetry so that couplings are related but with an extra Higgs doublet in each sector so that the fermion mass patterns are different; (ii) the R-sector fermions are chosen much heavier than the Lsector ones in both scenarios; and finally (iii) both light and heavy neutrinos are Majorana fermions with the light neutrino masses arising from a pure type-II seesaw mechanism. We discuss the DM relic density, direct and indirect detection prospects and associated collider signatures of the model. Comparing with current collider and direct detection constraints, we find a lower bound on the DM mass of order of 1 TeV. We also point out a way to relax the DM unitarity bound in our model for much larger DM masses by an entropy dilution mechanism. An additional feature of the model is that the DM can be made very long lived, if desired, by allowing for weak breaking of the above Z 2 symmetry. Our model also predicts the existence of long-lived colored particles which could be searched for at the LHC.

Section: Model Without Parity Symmetrymentioning

confidence: 98%

Section: Effective Theory Atmentioning

confidence: 99%

Section: Jhep11(2016)077mentioning

confidence: 99%

“…, which requires a larger quartic coupling than in SM and thus could possibly help to improve the stability of the EW vacuum, as compared to the SM [61].…”

Section: Jhep11(2016)077mentioning

confidence: 99%

See 2 more Smart Citations

Naturally stable right-handed neutrino dark matter

Dev

Mohapatra

Zhang

2016

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“…Since the minimal version of this model predicts Majorana nature of light neutrinos by virtue of the in built seesaw mechanism, we consider a version of LRSM where the tree level Majorana mass term for the light neutrinos can be forbidden. One such possibility lies in the LRSM without the conventional Higgs bidoublet [57][58][59][60][61] where all the fermions acquire masses through a universal seesaw mechanism due to the presence of additional heavy fermions. Very recently this model was also studied in the context of 750 GeV diphoton excess at LHC [62][63][64] 1 by several authors [67][68][69][70].…”

Section: The Modelmentioning

confidence: 99%

Observable lepton number violation with predominantly Dirac nature of active neutrinos

Borah

Dasgupta

2017

We study a specific version of SU(2) R ×SU(2) L ×U(1) B−L models extended by discrete symmetries where the new physics sector responsible for tiny neutrino masses at leading order remains decoupled from the new physics sector that can give rise to observable signatures of lepton number violation such as neutrinoless double beta decay. More specifically, the dominant contribution to light neutrino masses comes from a one-loop Dirac mass. At higher loop level, a tiny Majorana mass also appears which remains suppressed by many order of magnitudes in comparison to the Dirac mass. Such a model where the active neutrinos are predominantly of Dirac type, also predicts observable charged lepton flavour violation like µ → 3e, µ → eγ and multi-component dark matter.

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

Chauhan¹,

Dev²,

Mohapatra

2019

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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 × U (1) I 3R × 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 v R 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 Z R boson in the left-right model at the LHC, even in the high-luminosity phase, and leaves only a narrow window for the W R boson. A much broader allowed parameter space, with the right-handed scale v R up to 87 TeV, could be probed at the future 100 TeV collider.