Dirac neutrinos and Neff Luo, Xuheng; Rodejohann, Werner; Xun-Jie Xu
Journal of cosmology and astroparticle physics,
06/2020, Letnik:
2020, Številka:
6
Journal Article
Recenzirano
If neutrinos are Dirac particles the existence of light right-handed neutrinos νR is implied. Those would contribute to the effective number of relativistic neutrino species Neff in the early ...Universe. With pure standard model interactions, the contribution is negligibly small. In the presence of new interactions, however, the contribution could be significantly enhanced. We consider the most general effective four-fermion interactions for neutrinos (scalar, pseudo-scalar, vector, axial-vector and tensor), and compute the contribution of right-handed neutrinos to Neff. Taking the Planck 2018 measurement of Neff, strong constraints on the effective four-fermion coupling are obtained, corresponding to interaction strengths of 10−5∼10−3 in units of the Fermi constant. This translates in new physics scales of up to 43 TeV and higher. Future experiments such as CMB-S4 can probe or exclude the existence of effective 4-neutrino operators for Dirac neutrinos. Ways to avoid this conclusion are discussed.
Neutrino self-interactions (νSI) beyond the Standard Model are an attractive possibility to soften cosmological constraints on neutrino properties and also to explain the tension in late and early ...time measurements of the Hubble expansion rate. The required strength of νSI to explain the 4σ Hubble tension is in terms of a pointlike effective four-fermion coupling that can be as high as 109GF, where GF is the Fermi constant. In this work, we show that such strong νSI can cause significant effects in two-neutrino double beta decay, leading to an observable enhancement of decay rates and to spectrum distortions. We analyze self-interactions via an effective operator as well as when mediated by a light scalar. Data from observed two-neutrino double beta decay are used to constrain νSI, which rules out the regime around 109GF.
Solar neutrino physics Xu, Xun-Jie; Wang, Zhe; Chen, Shaomin
Progress in particle and nuclear physics,
July 2023, 2023-07-00, Letnik:
131
Journal Article
Recenzirano
Odprti dostop
As a free, intensive, rarely interactive, and well directional messenger, solar neutrinos have been driving both solar physics and neutrino physics developments for more than half a century. Since ...more extensive and advanced neutrino experiments are under construction, being planned or proposed, we are striving toward an era of precise and comprehensive measurement of solar neutrinos in the next decades. In this article, we review recent theoretical and experimental progress achieved in solar neutrino physics. We present not only an introduction to neutrinos from the standard solar model and the standard flavor evolution, but also a compilation of a variety of new physics that could affect and hence be probed by solar neutrinos. After reviewing the latest techniques and issues involved in the measurement of solar neutrino spectra and background reduction, we provide our anticipation on the physics gains from the new generation of neutrino experiments.
Dark matter produced from neutrinos Hufnagel, Marco; Xu, Xun-Jie
Journal of Cosmology and Astroparticle Physics,
01/2022, Letnik:
2022, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
In the presence of interactions between neutrinos and dark matter (DM), DM can potentially be produced via freeze-in from the neutrino sector. We investigate the implications of such a ...scenario for the evolution of both DM and neutrinos in the early Universe, and show that the future cosmic neutrino detection experiment
PTOLEMY
might be sensitive to neutrino signals that originate from DM annihilation in this model.
Abstract
One of the few remaining unknowns in the standard three-flavor neutrino oscillation paradigm is the ordering of neutrino masses. In this work we propose a novel method for determining ...neutrino mass ordering using the time information on early supernova neutrino events. In a core-collapse supernova, neutrinos are produced earlier than antineutrinos and, depending on the mass ordering which affects the adiabatic flavor evolution, may cause earlier observable signals in
ν
e
detection channels than in others. Hence, the time differences are sensitive to the mass ordering. We find that using the time information on the detection of the first galactic supernova events at future detectors like DUNE, JUNO and Hyper-Kamiokande, the mass ordering can already be determined at
∼ 2
σ
CL, while (10) events suffice for the discovery. Our method does not require high statistics and could be used within the supernova early warning system (SNEWS) which will have access to the time information on early supernova neutrino events recorded in a number of detectors. The method proposed in this paper also implies a crucial interplay between the mass ordering and the triangulation method for locating supernovae.
A
bstract
Light bosons can mediate long-range forces. We show that light bosonic mediators interacting with a background medium, in particular, with the cosmic neutrino background (C
ν
B), may induce ...medium-dependent masses which could effectively screen long-range forces from detection. This leads to profound implications for long-range force searches in e.g. the Eöt-Wash, MICROSCOPE, and lunar laser-ranging (LLR) experiments. For instance, we find that when the coupling of the mediator to neutrinos is above 3 × 10
−
10
or 5 × 10
−
13
, bounds from LLR and experiments employing the Sun as an attractor, respectively, would be entirely eliminated. Larger values of the coupling can also substantially alleviate bounds from searches conducted at shorter distances.
Abstract Neutrinos are often considered as a portal to new physics beyond the Standard Model (SM) and might possess phenomenologically interesting interactions with dark matter (DM). This paper ...examines the cosmological imprints of DM that interacts with and is produced from SM neutrinos at temperatures below the MeV scale. We take a model-independent approach to compute the evolution of DM in this framework and present analytic results which agree well with numerical ones. Both freeze-in and freeze-out regimes are included in our analysis. Furthermore, we demonstrate that the thermal evolution of neutrinos might be substantially affected by their interaction with DM. We highlight two distinctive imprints of such DM on neutrinos: (i) a large, negative contribution to N eff , which is close to the current experimental limits and will readily be probed by future experiments; (ii) spectral distortion of the cosmic neutrino background (CνB) due to DM annihilating into neutrinos, a potentially important effect for the ongoing experimental efforts to detect CνB.
We derive constraints on all possible general neutrino-electron interactions (scalar, vector, pseudo-scalar, axial-vector and tensor) using the recent real time Borexino event rate measurements of ...pp, pep and Be7 solar neutrinos. Some of the limits improve from TEXONO and CHARM-II for incoming electron and muon neutrinos while the rest remains weaker for Borexino and those for the tau flavor are the first ones. Future improvements by next-generation solar neutrino experiments are also studied. The limits extend the physics reach of solar neutrino measurements to TeV-scale physics. Finally, the different properties of the new interactions for Dirac and Majorana neutrinos are discussed.
The vR-philic scalar dark matter Xun-Jie Xu; Zhou, Siyu; Zhu, Junyu
Journal of cosmology and astroparticle physics,
04/2024, Letnik:
2024, Številka:
4
Journal Article
Recenzirano
Right-handed neutrinos (vR) offer an intriguingportal to new physics in hidden sectors where dark matter (DM) mayreside. In this work, we delve into the simplest hidden sector involvingonly a real ...scalar exclusively coupled to vR, referred toas the vR-philic scalar. We investigate the viability of thevR-philic scalar to serve as a DM candidate, under the constraintthat the coupling of vR to the standard model is determinedby the seesaw relation and is responsible for the observed DM abundance.By analyzing the DM decay channels and solving Boltzmann equations,we identify the viable parameter space. In particular, our study revealsa lower bound (2.6 × 105 GeV) on the mass of vR forthe vR-philic scalar to be DM. The DM mass may vary from sub-MeVto sub-GeV. Within the viable parameter space, monochromatic neutrinolines from DM decay can be an important signal for DM indirect detection.
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