Light vectorlike fermions in a minimal<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>S</mml:mi><mml:mi>U</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>5</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:math>setup

Doršner, Ilja; Fajfer, Svjetlana; Mustać, Ivana

doi:10.1103/physrevd.89.115004

Cited by 30 publications

(20 citation statements)

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“…(35), but multiplied by 2 since there are two VLF Dirac sets as argued above, and changing the coupling to y tỹ 2 instead of y 3 t , which then gives us the β V LF yt in Eq. (19). Next, consider the evolution of either the hψ 1ψ1 coupling, or the hψ 2ψ2 coupling, either of which isỹ.…”

Section: Discussionmentioning

confidence: 99%

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Higgs vacuum stability with vectorlike fermions

Gopalakrishna

Velusamy

2019

Phys. Rev. D

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We present the effects of vector-like fermions (VLF) on the stability of the Higgs electroweak vacuum, using the renormalization group improved Higgs effective potential. We review the calculation of the one-loop beta-functions of the standard model couplings paying particular attention to the fermion contributions. From this, we derive the VLF contributions to the betafunctions. We also include the significant two-loop contributions to the beta-functions. Using these beta-functions, we determine the scale at which the effective Higgs quartic-coupling becomes zero and goes negative, signaling vacuum instability. We find that for certain VLF masses and Yukawa couplings, the Higgs quartic stays positive for field values all the way up to the Planck scale, implying that the meta-stable vacuum of the standard model can be rendered absolutely stable if VLFs are present with certain parameters. For other values of VLF parameters, the Higgs vacuum is metastable as in the standard model. For cases where the vacuum is metastable, we compute the probability of quantum tunneling from the false electroweak vacuum into a deeper true vacuum in our Hubble volume by numerically solving for the bounce configuration in Euclidean space-time and computing the bounce action for it. We compare our numerical solution with the analytical approximation for the bounce action commonly used in the literature, and comment on when the latter may be used. * shri@imsc.res.in † arunprasath@imsc.res.in arXiv:1812.11303v3 [hep-ph] 13 Jul 2019Denoting the field value as h ≡ µ and denoting λ eff (µ) as just λ(µ), it can be shown (see for example Ref. [41]) that λ(µ) obeys a renormalization group equation (RGE) of the formThe RGE is interpreted now as an evolution with field value h = µ, and the β-function β λ is the usual β-function for the coupling λ, governed by the RGE. The λ(µ) obtained by integrating the RGE has the leading logs of the form log n (µ/M ) resummed. β λ is shown as a function of λ itself, and also of the other couplings that contribute significantly, which, in the SM, are the top Yukawa coupling y t and the SU (3), SU (2), U (1) gauge couplings g a = {g 3 , g 2 , g 1 }. All these couplings also evolve with µ via analogous RGE equations with their corresponding β-functions β yt , β ga . We neglect the contributions of the other SM couplings to the β-functions as they contribute insignificantly. From Eq.(3) we see that for h m h , the instability is signalled by the Higgs quartic effective coupling λ(µ) becoming negative.As we show explicitly later, β λ obtains a negative contribution from y t , while it obtains a positive contribution from λ(µ) itself and from gauge couplings. Thus, the top quark has the important effect of decreasing λ(µ), and for y t as large as in the SM, for the observed m h , it drives λ(µ) negative at higher energies, signaling vacuum instability. The effect of fermions coupled to the Higgs is generally to destabilize the electroweak vacuum, although in this work we show that this statement is not so definit...

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Section: Discussionmentioning

confidence: 99%

“…[10,11,12,13,14], gauge-coupling unification in Refs. [15,16,17,18,19], neutrino mass generation and vacuum stability in Refs. [20,21,22,23,24,25], universal extra dimension model in Ref.…”

Section: Introductionmentioning

confidence: 99%

Higgs vacuum stability with vectorlike fermions

Gopalakrishna

Velusamy

2019

Phys. Rev. D

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“…Extensive investigations with number of SU(5) GUT extensions have been carried out with proton lifetime predictions consistent with experimental limits [143][144][145][146][147][148][149][150][151][152]. But implementation of type-II seesaw dominance due to type-I seesaw cancellation resulting in dominant LFV and LNV decays as dicussed below is new especially in the context of non-SUSY SU(5).…”

Section: Coupling Unification Gut Scale and Proton Lifetimementioning

confidence: 99%

High Scale Type-II Seesaw, Dominant Double Beta Decay within Cosmological Bound and LFV Decays in SU(‎5)

Parida

Satpathy

2019

Advances in High Energy Physics

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Very recently a novel implementation of type-II seesaw mechanism for neutrino mass has been proposed in SU(5) grand unified theory with a number of desirable new physical phenomena beyond the standard model. Introducing heavy right-handed neutrinos and extra fermion singlets, in this work we show how the type-I seeaw cancellation mechanism works in this SU(5) framework. Besides predicting verifiable LFV decays, we further show that the model predicts dominant double beta decay with normal hierarchy or inverted hierarchy of active light neutrino masses in concordance with cosmological bound. In addition a novel right-handed neutrino mass generation mechanism, independent of type-II seesaw predicted mass hierarchy, is suggested in this work. †

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“…The issue of gauge coupling unification in the presence of VL fermions is not a new idea and it received a lot of attention in the literarture, both before the launch of the LHC [14,15,16,17,18,19,20,21,22,23], and after [24,25,26,27,28,10]. Similar analyses within the SUSY framework were performed as well [29,30,31,32,33,34,35,36].…”

Section: Introductionmentioning

confidence: 98%

Road map through the desert: unification with vector-like fermions

Kowalska

Kumar

2019

J. High Energ. Phys.

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In light of null results from New Physics searches at the LHC, we look at unification of the gauge couplings as a model-building principle. As a first step, we consider extensions of the Standard Model with vector-like fermions. We present a comprehensive list of spectra that feature fermions in two distinct SU (3) C × SU (2) L × U (1) Y representations, in which precise gauge coupling unification is achieved. We derive upper and lower limits on vector-like masses from proton decay measurements, running of the strong gauge coupling, heavy stable charged particle searches, and electroweak precision tests. We demonstrate that due to a particular hierarchy among the mass parameters required by the unification condition, complementarity of various experimental strategies allows us to probe many of the successful scenarios up to at least 10 TeV.

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Light vectorlike fermions in a minimalSU(5)setup

Cited by 30 publications

References 103 publications

Higgs vacuum stability with vectorlike fermions

Higgs vacuum stability with vectorlike fermions

High Scale Type-II Seesaw, Dominant Double Beta Decay within Cosmological Bound and LFV Decays in SU(‎5)

Road map through the desert: unification with vector-like fermions

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