<p>We explore the impact of the backreaction of evaporation on the quantum state of primordial black holes (PBHs), known as “memory burden,” on the baryon asymmetry production in the Universe through high-scale leptogenesis. Focusing on PBH masses ranging from 1 to 1000 g, we investigate the interplay between the nonthermal production of heavy sterile neutrinos and the entropy injection within this nonstandard cosmological framework. By assuming appropriate values for the memory-burden parameters, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>q</mi><mo>=</mo><mn>1</mn><mo>/</mo><mn>2</mn></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>k</mi><mo>=</mo><mn>1</mn></math>, we derive mutual exclusion limits between PBHs and thermal leptogenesis in the mixed parameter space. Our analysis reveals that the primary contribution of PBHs to baryon asymmetry stems from entropy injection. Indeed, we find that, different from earlier studies based on the semiclassical Hawking evaporation, the memory-burden effect suppresses the nonthermal source term in the PBH mass range explored. This has significant implications for understanding baryogenesis in such alternative cosmological scenarios.</p>

Italy

Roberta Calabrese

Marco Chianese

Ninetta Saviano

Impact of memory-burdened primordial black holes on high-scale leptogenesis

<p>Cosmic strings radiate detectable gravitational waves in models featuring high-scale symmetry breaking, e.g., high-scale leptogenesis. In this Letter, for the first time, we show that different flavored regimes of high-scale leptogenesis can be tested with the spectral features in cosmic string-radiated gravitational waves. This is possible if the scalar field that makes right-handed neutrinos massive is feebly coupled to the Standard Model Higgs. Each flavored regime, sensitive to low-energy neutrino experiments, leaves a marked imprint on the gravitational waves spectrum. A three-flavor and a two-flavor regime could be probed by a characteristic fall-off of the gravitational wave spectrum at the LISA-DECIGO-ET frequency bands with preceding scale-invariant amplitudes bounded from above and below. We present gravitational waves windows for flavored regimes of leptogenesis testable in the upcoming experiments. We also provide the first construction of a leptogenesis framework where a testable distinction of flavor regimes is possible without constraining the flavor structure of the theory.</p>

China

Satyabrata Datta

Gennaro Miele

Rome Samanta

Probing flavored regimes of leptogenesis with gravitational waves from cosmic strings

We investigate the effects on sub-TeV resonant leptogenesis of primordial black holes with masses from <math><msup><mn>10</mn><mn>6</mn></msup><mtext> </mtext><mtext> </mtext><mi>g</mi></math> to <math><mo>∼</mo><msup><mn>10</mn><mn>9</mn></msup><mtext> </mtext><mtext> </mtext><mi>g</mi></math>. The latter might dominate the energy content of the Universe altering its evolution and, eventually, diluting the final baryon asymmetry. We find that, depending on the mass and abundance of primordial black holes, the parameter space of sub-TeV resonant leptogenesis shrinks towards higher right-handed neutrino masses and smaller active-sterile mixing. Remarkably, this translates into important implications for the experimental searches of heavy neutral leptons. Conversely, we demonstrate that a possible future detection of sub-TeV heavy neutral leptons would disfavor regions of the parameter space of primordial black holes currently allowed.

Jacob Gunn

Stefano Morisi

Impact of primordial black holes on heavy neutral leptons searches in the framework of resonant leptogenesis

We investigate the role that the evaporation of light primordial black holes may have played in the production of the baryon asymmetry of the Universe through high-scale leptogenesis. In particular, for masses of primordial black holes in the range <math><mrow><mo>[</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>6</mn></mrow></msup><mi>–</mi><msup><mrow><mn>10</mn></mrow><mrow><mn>9</mn></mrow></msup><mo>]</mo><mtext> </mtext><mtext> </mtext><mi>g</mi></mrow></math>, we find a dilution of thermally generated lepton asymmetry via entropy injection in the primordial plasma after the sphaleron freeze-out. As a consequence, we can put strong constraints on the primordial black hole parameters, showing the mutual exclusion limits between primordial black holes and high-scale leptogenesis. Remarkably, we point out an interplay between the upper bound on the initial abundance of primordial black holes and the active neutrino mass scale.

Limits on light primordial black holes from high-scale leptogenesis

Primordial black holes are a possible component of dark matter and a most promising way of investigating them is through the product of their Hawking evaporation. As a result of this process, any species lighter than the Hawking temperature is emitted, including possible new particles beyond the Standard Model. These can then be detected in laboratory-based experiments via their interaction with the Standard Model particles. In a previous work, we have first proposed and studied this scenario in the presence of an interaction between the light new species and nucleons. Here we extend this discussion to include the case of interaction with electrons. We show that the simultaneous presence of primordial black holes and species lighter than about 100 MeV can be constrained by the measurements of direct detection experiments, such as XENON1T, and water Cherenkov neutrino detectors, such as Super-Kamiokande. Our results provide a complementary and alternative way of investigation with respect to cosmological and collider searches.

Denmark

Damiano F. G. Fiorillo

Electron scattering of light new particles from evaporating primordial black holes

The direct detection of sub-GeV dark matter interacting with nucleons is hampered by the low recoil energies induced by scatterings in the detectors. This experimental difficulty is avoided in the scenario of boosted dark matter where a component of dark matter particles is endowed with large kinetic energies. In this paper, we point out that the current evaporation of primordial black holes with a mass from <math><msup><mn>10</mn><mn>14</mn></msup></math> to <math><msup><mn>10</mn><mn>16</mn></msup><mtext> </mtext><mtext> </mtext><mi>g</mi></math> is a source of boosted light dark matter with energies of tens to hundreds of MeV. Focusing on the XENON1T experiment, we show that these relativistic dark matter particles could give rise to a signal orders of magnitude larger than the present upper bounds. Therefore, we are able to significantly constrain the combined parameter space of primordial black holes and sub-GeV dark matter. In the presence of primordial black holes with masses of <math><msup><mn>10</mn><mn>15</mn></msup><mtext> </mtext><mtext> </mtext><mi>g</mi></math> and abundances compatible with present bounds, the limits on a dark matter-nucleon cross section are improved by four orders of magnitude.

Direct detection of light dark matter from evaporating primordial black holes

We consider relatively heavy neutrinos <math><msub><mi>ν</mi><mi>H</mi></msub></math>, mostly contributing to a sterile state <math><msub><mi>ν</mi><mi>s</mi></msub></math>, with mass in the range <math><mrow><mn>10</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi><mo>≲</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>s</mi></mrow></msub><mo>≲</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>π</mi></mrow></msub><mo>∼</mo><mn>135</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></mrow></math>, which are thermally produced in the early Universe in collisional processes involving active neutrinos and freezing out after the QCD phase transition. If these neutrinos decay after the active neutrino decoupling, they generate extra neutrino radiation but also contribute to entropy production. Thus, they alter the value of the effective number of neutrino species <math><msub><mi>N</mi><mi>eff</mi></msub></math> as, for instance, measured by the cosmic microwave background (CMB), as well as affect primordial nucleosynthesis (BBN), notably <math><mrow><mmultiscripts><mrow><mi>He</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>4</mn></mrow></mmultiscripts></mrow></math> production. We provide a detailed account of the solution of the relevant Boltzmann equations. We also identify the parameter space allowed by current Planck satellite data and forecast the parameter space probed by future stage-4 ground-based CMB observations, expected to match or surpass BBN sensitivity.

Leonardo Mastrototaro

France

Pasquale Dario Serpico

Alessandro Mirizzi

Massive sterile neutrinos in the early Universe: From thermal decoupling to cosmological constraints

We consider the effects of active-sterile secret neutrino interactions, mediated by a new pseudoscalar particle, on high and ultrahigh energy neutrino fluxes. In particular, we focus on the case of three active and one sterile neutrino coupled by a flavor dependent interaction, extending the case of one active and one sterile neutrino we have recently examined. We find that, depending on the kind of interaction of a sterile neutrino with the active sector, new regions of the parameter space for secret interactions are now allowed, with the masses of a sterile neutrino and scalar mediator ranging from 10 MeV to 1 GeV, leading to interesting phenomenological implications on two benchmark fluxes we consider, namely an astrophysical power law flux, in the range below 100 PeV, and a cosmogenic flux, in the ultrahigh energy range. First of all, the final active fluxes can present a measurable depletion observable in future experiments. Especially, in the case of only a <math><msub><mi>ν</mi><mi>τ</mi></msub><mo>−</mo><msub><mi>ν</mi><mi>s</mi></msub></math> interaction, we find that the effects on the astrophysical power law flux can be so large to be already probed by the IceCube experiment. Moreover, we find intriguing features in the energy dependence of the flavor ratio.

Damiano Fiorillo

Observable features in ultrahigh energy neutrinos due to active-sterile secret interactions

Ultra high energy cosmogenic neutrinos may represent a unique opportunity to unveil possible new physics interactions once restricted to the neutrino sector only. In the present paper we study the observable effects of a secret active-sterile interactions, mediated by a pseudoscalar, on the expected flux of cosmogenic neutrinos. The results show that for masses of sterile neutrinos and pseudoscalars of hundreds MeV, necessary to evade cosmological, astrophysical, and elementary particle constraints, the presence of such new interactions can significantly change the energy spectrum of cosmogenic neutrinos at Earth in the energy range from PeV to ZeV. Interestingly, the distortion of the spectrum results to be detectable at apparatus like GRAND or ARIANNA if the mediator mass is around 250 MeV and the UHECRs are dominated by the proton component. Larger mediator masses or a chemical composition of UHECRs dominated by heavier nuclei would require much larger cosmic rays apparatus which might be available in future.