Identifying spin properties of evaporating black holes through asymmetric neutrino and photon emission

Kerr black holes radiate neutrinos in an asymmetric pattern, preferentially in the lower hemisphere relative to the black hole’s rotation axis, while antineutrinos are predominantly produced in the upper hemisphere. Leveraging this asymmetric emission, we explore the potential of high energy, Eν ≳ 1 TeV, neutrino, and antineutrino detection to reveal crucial characteristics of an evaporating primordial black hole at the time of its burst when observed near Earth. We improve upon previous calculations by carefully accounting for the nonisotropic particle emission, as Earth occupies a privileged angle relative to the black hole’s rotation axis. Additionally, we investigate the angular dependence of primary and secondary photonspectra and assess the evaporating black hole’s time evolution during the final explosive stages of its lifetime. Since photon events outnumber neutrinos by about three orders of magnitude, we find that a neutrino measurement can aid in identifying the initial angular momentum and the black hole hemisphere facing Earth only for evaporating black holes within our solar system, at distances ≲10−4 pc, and observed during the final 100 s of their lifetime

From Dirac to Majorana: The cosmic neutrino background capture rate in the minimally extended Standard Model

We investigate the capture rate of the cosmic neutrino background on tritium within the Standard Model, extended to incorporate three right-handed singlet neutrinos with explicit lepton-number violation. We consider a scenario where the 6 × 6 neutrino mixing matrix factorizes into three independent 2 × 2 pairs and analyze the states produced from weak interactions just before neutrino decoupling. Taking into account the unrestricted Majorana mass scale associated with lepton number violation, spanning from the grand unification scale to Planck-suppressed values, we observe a gradual transition in the capture rate from a purely Majorana neutrino to a purely (pseudo) Dirac neutrino. We demonstrate that the capture rate is modified if the lightest active neutrino is relativistic, and this can be used to constrain the tiniest value of mass-squared difference ∼10−35 eV2, between the active-sterile pair, probed so far. Consequently, thecosmic neutrino capture rate could become a promising probe for discerning the underlying mechanism responsible for generating neutrino masses

Impact of Beyond the Standard Model Physics in the Detection of the Cosmic Neutrino Background

We discuss the effect of Beyond the Standard Model charged current interactions on the detection of the Cosmic Neutrino Background by neutrino capture on tritium in a PTOLEMY-like detector. We show that the total capture rate can be substantially modified for Dirac neutrinos if scalar or tensor right-chiral currents, with strength consistent with current experimental bounds, are at play. We find that the total capture rate for Dirac neutrinos, $\Gamma_{\rm D}^{\rm BSM}$, can be between 0.3 to 2.2 of what is expected for Dirac neutrinos in the Standard Model, $\Gamma_{\rm D}^{\rm SM}$, so that it can be made as large as the rate expected for Majorana neutrinos with only Standard Model interactions. A non-negligible primordial abundance of right-handed neutrinos can only worsen the situation, increasing $\Gamma_{\rm D}^{\rm BSM}$ by 30 to 90\%. On the other hand, if a much lower total rate is measured than what is expected for $\Gamma_{\rm D}^{\rm SM}$, it may be a sign of new physics.Comment: Version published in JHEP. Some comments and references adde

Neutrino Discovery Limit of Dark Matter Direct Detection Experiments in the Presence of Non-Standard Interactions

The detection of coherent neutrino-nucleus scattering by the COHERENT collaboration has set on quantitative grounds the existence of an irreducible neutrino background in direct detection searches of Weakly Interacting Massive Dark Matter candidates. This background leads to an ultimate discovery limit for these experiments: a minimum Dark Matter interaction cross section below which events produced by the coherent neutrino scattering will mimic the Dark Matter signal, the so-called \emph{neutrino floor}. In this work we study the modification of such neutrino floor induced by non-standard neutrino interactions within their presently allowed values by the global analysis of oscillation and COHERENT data. By using the full likelihood information of such global analysis we consistently account for the correlated effects of non-standard neutrino interactions both in the neutrino propagation in matter and in its interaction in the detector. We quantify their impact on the neutrino floor for five future experiments: DARWIN (Xe), ARGO (Ar), Super-CDMS HV (Ge and Si) and CRESST phase III (CaWO$_4$). Quantitatively, we find that non-standard neutrino interactions allowed at the $3\sigma$ level can result in an increase of the neutrino floor of up to a factor $\sim 5$ with respect to the Standard Model expectations and impact the expected sensitivities of the ARGO, CRESST phase III and DARWIN experiments.Comment: 21 pages, 4 figures. Matches version published in the JHEP. Corrected exposure and results for CRESST phase II

JUNO as a probe of the pseudo-Dirac nature using solar neutrinos

It remains a possibility that neutrinos are pseudo-Dirac states, such that a generation is composed of two maximally mixed Majorana neutrinos separated by a very small mass difference. We explore the physics potential of the JUNO experiment in constraining this possibility using the measurement of solar neutrinos. In particular, we investigate cases where one or three sterile states are present in addition to the active states. We consider two scenarios: one where JUNO’s energy threshold allows for the measurement of pp solar neutrinos, and the case where JUNO can only measure 7Be neutrinos and above. We find that JUNO will be able to constrain pseudo-Dirac mass splittings of δm2≳2.9×10−13eV2 for the scenario including pp solar neutrinos, and δm2≳1.9×10−12eV2 when the measurement only considers 7Be monochromatic neutrinos, at the 3σ C.L. Thus, including pp neutrinos will be crucial for JUNO to improve current constraints on the pseudo-Dirac scenario from solar neutrinos

Superradiant leptogenesis

We investigate how superradiance affects the generation of baryon asymmetry in a universe with rotating primordial black holes, considering a scenario where a scalar boson is coupled to the heavy right-handed neutrinos. We identify the regions of the parameter space where the scalar production is enhanced due to superradiance. This enhancement, coupled with the subsequent decay of the scalar into right handed neutrinos, results in the non-thermal creation of lepton asymmetry. We show that successful leptogenesis is achieved for masses of primordial black holes in the range of order O(0.1 g) − O(10 g) and the lightest of the heavy neutrino masses, MN ~ O(1012) GeV. Consequently, regions of the parameter space, which in the case of Schwarzchild PBHs were incompatible with viable leptogenesis, can produce the observed matter-antimatter asymmetry

Evaporation of Primordial Black Holes in the Early Universe: Mass and Spin Distributions

Many cosmological phenomena lead to the production of primordial black holes in the early Universe. These phenomena often create a population of black holes with extended mass and spin distributions. As these black holes evaporate via Hawking radiation, they can modify various cosmological observables, lead to the production of dark matter, modify the number of effective relativistic degrees of freedom, $N_{\rm eff}$, source a stochastic gravitational wave background and alter the dynamics of baryogenesis. We consider the Hawking evaporation of primordial black holes that feature non-trivial mass and spin distributions in the early Universe. We demonstrate that the shape of such a distribution can strongly affect most of the aforementioned cosmological observables. We outline the numerical machinery we use to undertake this task. We also release a new version of FRISBHEE that handles the evaporation of primordial black holes with an arbitrary mass and spin distribution throughout cosmic history.Comment: 16 pages, 6 figures. Numerical codes released in https://github.com/yfperezg/frisbhe