Primordial non-Gaussianity as a probe of seesaw and leptogenesis. (arXiv:2307.07550v1 [hep-ph])

Primordial non-Gaussianity as a probe of seesaw and leptogenesis. (arXiv:2307.07550v1 [hep-ph])
<a href="http://arxiv.org/find/hep-ph/1/au:+Fong_C/0/1/0/all/0/1">Chee Sheng Fong</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Ghoshal_A/0/1/0/all/0/1">Anish Ghoshal</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Naskar_A/0/1/0/all/0/1">Abhishek Naskar</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Rahat_M/0/1/0/all/0/1">Moinul Hossain Rahat</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Saad_S/0/1/0/all/0/1">Shaikh Saad</a>

We present the possibility that the seesaw mechanism and nonthermal
leptogenesis can be probed via primordial non-Gaussianities in the context of a
majoron curvaton model. Originating as a massless Nambu-Goldstone boson from
the spontaneous breaking of the global baryon ($B$) minus lepton ($L$) number
symmetry at a scale $v_{B-L}$, majoron becomes massive when it couples to a new
confining sector through anomaly. Acting as a curvaton, majoron produces the
observed red-tilted curvature power spectrum without relying on any inflaton
contribution, and its decay in the post-inflationary era gives rise to a
nonthermal population of right-handed neutrinos that participate in
leptogenesis. A distinctive feature of the mechanism is the generation of
observable non-Gaussianity, nontrivially linked to the scale of seesaw and
leptogenesis. Identifying the viable parameter space, we show that the
non-Gaussianity parameter $f_{rm NL} gtrsim mathcal{O} (0.1)$ is produced
for high-scale seesaw ($v_{B-L}$ at $mathcal{O}(10^{14-17})$ GeV) and
leptogenesis ($M_1 gtrsim mathcal{O}(10^6)$ GeV) where the latter represents
the lightest right-handed neutrino mass. While the current bounds on local
non-Gaussianity excludes some part of parameter space, the rest can be fully
probed by future experiments like CMB-S4, LSST, and 21 cm tomography.

We present the possibility that the seesaw mechanism and nonthermal
leptogenesis can be probed via primordial non-Gaussianities in the context of a
majoron curvaton model. Originating as a massless Nambu-Goldstone boson from
the spontaneous breaking of the global baryon ($B$) minus lepton ($L$) number
symmetry at a scale $v_{B-L}$, majoron becomes massive when it couples to a new
confining sector through anomaly. Acting as a curvaton, majoron produces the
observed red-tilted curvature power spectrum without relying on any inflaton
contribution, and its decay in the post-inflationary era gives rise to a
nonthermal population of right-handed neutrinos that participate in
leptogenesis. A distinctive feature of the mechanism is the generation of
observable non-Gaussianity, nontrivially linked to the scale of seesaw and
leptogenesis. Identifying the viable parameter space, we show that the
non-Gaussianity parameter $f_{rm NL} gtrsim mathcal{O} (0.1)$ is produced
for high-scale seesaw ($v_{B-L}$ at $mathcal{O}(10^{14-17})$ GeV) and
leptogenesis ($M_1 gtrsim mathcal{O}(10^6)$ GeV) where the latter represents
the lightest right-handed neutrino mass. While the current bounds on local
non-Gaussianity excludes some part of parameter space, the rest can be fully
probed by future experiments like CMB-S4, LSST, and 21 cm tomography.

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