Twin modular S4 with SU(5) GUT King, Stephen F.; Zhou, Ye-Ling
The journal of high energy physics,
04/2021, Volume:
2021, Issue:
4
Journal Article
Peer reviewed
Open access
A
bstract
We discuss the SU(5) grand unified extension of flavour models with multiple modular symmetries. The proposed model involves two modular
S
4
groups, one acting in the charged fermion ...sector, associated with a modulus field value
τ
T
with residual
Z
3
T
symmetry, and one acting in the right-handed neutrino sector, associated with another modulus field value
τ
SU
with residual
Z
2
SU
symmetry. Quark and lepton mass hierarchies are naturally generated with the help of weightons, which are SM singlet fields, where their non-zero modular weights play the role of Froggatt-Nielsen charges. The model predicts TM
1
lepton mixing, and neutrinoless double beta decay at rates close to the sensitivity of current and future experiments, for both normal and inverted orderings, with suppressed corrections from charged lepton mixing due to the triangular form of its Yukawa matrix.
A
bstract
We show how the generation of right-handed neutrino masses in Majoron models may be associated with a first-order phase transition and accompanied by the production of a stochastic ...background of gravitational waves (GWs). We explore different energy scales with only renormalizable operators in the effective potential. If the phase transition occurs above the electroweak scale, the signal can be tested by future interferometers. We consider two possible energy scales for phase transitions below the electroweak scale. If the phase transition occurs at a GeV, the signal can be tested at LISA and provide a complementary cosmological probe to right-handed neutrino searches at the FASER detector. If the phase transition occurs below 100 keV, we find that the peak of the GW spectrum is two or more orders of magnitude below the putative NANOGrav GW signal at low frequencies, but well within reach of the SKA and THEIA experiments. We show how searches of very low frequency GWs are motivated by solutions to the Hubble tension in which ordinary neutrinos interact with the dark sector. We also present general calculations of the phase transition temperature and Euclidean action that apply beyond Majoron models.
A
bstract
The
CP
violation in the neutrino transition electromagnetic dipole moment is discussed in the context of the Standard Model with an arbitrary number of right-handed singlet neutrinos. A ...full one-loop calculation of the neutrino electromagnetic form factors is performed in the Feynman gauge. A non-zero
CP
asymmetry is generated by a required threshold condition for the neutrino masses along with non-vanishing
CP
violating phases in the lepton flavour mixing matrix. We follow the paradiagm of
CP
violation in neutrino oscillations to parametrise the flavour mixing contribution into a series of Jarlskog-like parameters. This formalism is then applied to a minimal seesaw model with two heavy right-handed neutrinos denoted
N
1
and
N
2
. We observe that the
CP
asymmetries for decays into light neutrinos
N → νγ
are extremely suppressed, maximally around 10
−
17
. However the
CP
asymmetry for
N
2
→ N
1
γ
can reach of order unity. Even if the Dirac
CP
phase
δ
is the only source of
CP
violation, a large
CP
asymmetry around 10
−
5
–10
−
3
is comfortably achieved.
A
bstract
The idea of modular invariance provides a novel explanation of flavour mixing. Within the context of finite modular symmetries Γ
N
and for a given element
γ
∈ Γ
N
, we present an algorithm ...for finding stabilisers (specific values for moduli fields
τ
γ
which remain unchanged under the action associated to
γ
). We then employ this algorithm to find all stabilisers for each element of finite modular groups for
N
= 2 to 5, namely, Γ
2
≃
S
3
, Γ
3
≃
A
4
, Γ
4
≃
S
4
and Γ
5
≃
A
5
. These stabilisers then leave preserved a specific cyclic subgroup of Γ
N
. This is of interest to build models of fermionic mixing where each fermionic sector preserves a separate residual symmetry.
A
bstract
Grand Unified Theories (GUT) predict proton decay as well as the formation of cosmic strings which can generate gravitational waves. We determine which non-supersymmetric SO(10) breaking ...chains provide gauge unification in addition to a gravitational signal from cosmic strings. We calculate the GUT and intermediate scales for these SO(10) breaking chains by solving the renormalisation group equations at the two-loop level. This analysis predicts the GUT scale, hence the proton lifetime, in addition to the scale of cosmic string generation and thus the associated gravitational wave signal. We determine which SO(10) breaking chains survive in the event of the null results of the next generation of gravitational waves and proton decay searches and determine the correlations between proton decay and gravitational waves scales if these observables are measured.
A
bstract
The radiative decay of neutral fermions has been studied for decades but
CP
violation induced within such a paradigm has evaded attention.
CP
violation in these processes can produce an ...asymmetry between circularly polarised directions of the radiated photons and produces an important source of net circular polarisation in particle and astroparticle physics observables. The results presented in this work outlines the general connection between
CP
violation and circular polarisation for both Dirac and Majorana fermions and can be used for any class of models that produce such radiative decays. The total
CP
violation is calculated based on a widely studied Yukawa interaction considered in both active and sterile neutrino radiative decay scenarios as well as searches for dark matter via direct detection and collider signatures. Finally, the phenomenological implications of the formalism on keV sterile neutrino decay, leptogenesis-induced right-handed neutrino radiative decay and IceCube-driven heavy dark matter decay are discussed.
A
bstract
We borrow the general idea of renormalization-group equations (RGEs) to understand how neutrino masses and flavor mixing parameters evolve when neutrinos propagate in a medium, highlighting ...a meaningful possibility that the genuine flavor quantities in vacuum can be extrapolated from their matter-corrected counterparts to be measured in some realistic neutrino oscillation experiments. Taking the matter parameter
a
≡
2
2
G
F
N
e
E
to be an arbitrary scale-like variable with
N
e
being the net electron number density and
E
being the neutrino beam energy, we derive a complete set of differential equations for the effective neutrino mixing matrix
V
and the effective neutrino masses
m
˜
i
(for
i
= 1
,
2
,
3). Given the standard parametrization of
V
, the RGEs for
θ
˜
12
,
θ
˜
13
,
θ
˜
23
,
δ
˜
in matter are formulated for the first time. We demonstrate some useful differential invariants which retain the same form from vacuum to matter, including the well-known Naumov and Toshev relations. The RGEs of the partial
μ
-
τ
asymmetries, the off-diagonal asymmetries and the sides of unitarity triangles of
V
are also obtained as a by-product.
A
bstract
In this work we provide a detailed study of the CP violating phase transition (CPPT) which is a new mechanism proposed to produce a baryon asymmetry. This mechanism exploits the Weinberg ...operator whose coefficient is dynamically realised from the vacuum expectation values (VEVs) of new scalars. In the specific case of the first order phase transition, the scalar VEVs vary in the bubble wall which separates the two phases. This results in a spacetime varying coefficient for the Weinberg operator. The interference of two Weinberg operators at different spacetime points generates a CP asymmetry between lepton and anti-lepton production/annihilation processes, which eventually results in an asymmetry between baryon and anti-baryon number densities in the early Universe. We present the calculation of the lepton asymmetry, based on non-equilibrium quantum field theory methods, in full. We consider the influence of the bubble wall characteristics and the impact of thermal effects on the lepton asymmetry and draw a comparison between the CPPT mechanism and electroweak baryogenesis.
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