arXiv subjects

P. C. de Holanda

Publications and source records attributed to P. C. de Holanda.

At least 19 recordsLinked to original sources

arXiv2025

Brazilian Report on Dark Matter 2024

One of the key scientific objectives for the next decade is to uncover the nature of dark matter (DM). We should continue prioritizing targets such as weakly-interacting massive particles (WIMPs), Axions, and other low-mass dark matter candidates to improve our chances of achieving it. A varied and ongoing portfolio of experiments spanning different scales and detection methods is essential to maximize our chances of discovering its composition. This report paper provides an updated overview of the Brazilian community's activities in dark matter and dark sector physics over the past years with a view for the future. It underscores the ongoing need for financial support for Brazilian groups actively engaged in experimental research to sustain the Brazilian involvement in the global search for dark matter particles

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arXiv2021

Updating $ν_{3}$ lifetime from solar antineutrino spectra

We study the production of antineutrinos from the solar neutrinos due the Majorana neutrino decays of neutrino to antineutrino. Using the antineutrino spectra from KamLAND and Borexino, we present newest limits on the lifetime of $ν_{3}$ in this scenario. We consider $ν_{3} \rightarrow \barν_{1} + X$ and $ν_{3} \rightarrow \barν_{2} + X$ channels assuming scalar or pseudo-scalar interactions. For hierarchical mass-splittings, the limits obtained by us are $τ_{3}/m_{3}~\geq 7\times 10^{-5} s/eV$ and $τ_{3}/m_{3}~\geq 1\times 10^{-5} s/eV$ for the two channels at $90\%$ C.L. We found that the newest bound is five orders of magnitude better than the atmospheric and long-baseline bounds.

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arXiv2019

Brazilian Community Report on Dark Matter

This white paper summarizes the activities of the Brazilian community concerning dark matter physics and highlights the importance of financial support to Brazilian groups that are deeply involved in experimental endeavours. The flagships of the Brazilian dark matter program are the Cherenkov Telescope Array, DARKSIDE, SBN and LHC experiments, but we emphasize that smaller experiments such as DAMIC and CONNIE constitute important probes to dark sectors as well and should receive special attention. Small experimental projects showing the potential to probe new regions of parameter space of dark matter models are encouraged. On the theoretical and phenomenological side, some groups are devoted to astrophysical aspects such as the dark matter density profile while others explore the signature of dark matter models at colliders, direct and indirect detection experiments. In summary, the Brazilian dark matter community that was born not long ago has grown tremendously in the past years and now plays an important role in the hunt for a dark matter particle.

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arXiv2019

Is the $H_0$ tension suggesting a 4th neutrino's generation?

Flavour oscillations experiments are suggesting the existence of a sterile, $4$th neutrino's generation with a mass of an eV order. This would mean an additional relativistic degree of freedom in the cosmic inventory, in contradiction with recent results from the Planck satellite, that have confirmed the standard value $N_{eff} \approx 3$ for the effective number of relativistic species. On the other hand, the Planck best-fit for the Hubble-Lemaître parameter is in tension with the local value determined with the Hubble Space Telescope, and adjusting $N_{eff}$ is a possible way to overcome such a tension. In this paper we perform a joint analysis of three complementary cosmological distance rulers, namely the CMB acoustic scale measured by Planck, the BAO scale model-independently determined by Verde {\it et al.}, and luminosity distances measured with JLA and Pantheon SNe Ia surveys. Two Gaussian priors were imposed to the analysis, the local expansion rate measured by Riess {\it et al.}, and the baryon density parameter fixed from primordial nucleosynthesis by Cooke {\it et al.}. For the sake of generality, two different models are used in the tests, the standard $Λ$CDM model and a generalised Chaplygin gas. The best-fit gives $N_{eff} \approx 4$ in both models, with a Chaplygin gas parameter slightly negative, $α\approx -0.04$. The standard value $N_{eff} \approx 3$ is ruled out with $\approx 3σ$.

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arXiv2019

Quantum Decoherence Effects in Neutrino Oscillations at DUNE

In this work we analyze quantum decoherence in neutrino oscillations considering the Open Quantum System framework and oscillations through matter for three neutrino families. Taking DUNE as a case study we performed sensitivity analyses for two neutrino flux configurations finding limits for the decoherence parameters. We also offer a physical interpretation for a new peak which arises at the $ν_{e}$ appearance probability with decoherence. The best sensitivity regions found for the decoherence parameters are $Γ_{21}\le 1.2\times10^{-23}\,\text{GeV}$ and $Γ_{32}\le 7.7\times10^{-25}\,\text{GeV}$ at $90\%$ C. L.

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arXiv2017

Parameter Limits for Neutrino Oscillation with Decoherence in KamLAND

In the framework of quantum open systems we analyze data from KamLAND by using a model that considers neutrino oscillation in a three-family approximation with the inclusion of the decoherence effect. Using a $χ^2$ test we find new limits for the decoherence parameter which we call $γ$, considering the most recent data by KamLAND. Assuming an energy dependence of the type $ γ= γ_0 \left( E/E_0 \right) ^n$, in 95 \% C.L. the limits found are $3.7 \times 10^{-24} GeV$ for $ n=-1$, $6.8 \times 10^{-22} GeV$ for $ n=0$, and $1.5 \times 10^{-19} GeV$ for $ n=1 $ on the energy dependence.

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arXiv2015

Neutrino Decay and Solar Neutrino Seasonal Effect

We consider the possibility of solar neutrino decay as a sub-leading effect on their propagation between production and detection. Using current oscillation data, we set a new lower bound to the $ν_2$ neutrino lifetime at $τ_2\, /\, m_2 \geq 7.2 \times 10^{-4}\,\,\hbox{s}\,.\,\hbox{eV}^{-1}$ at $99\%\,$C.L.. Also, we show how seasonal variations in the solar neutrino data can give interesting additional information about neutrino lifetime.

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arXiv2015

Confronting the Stochastic Neutrino Mixing Mechanism and the sterile neutrino hypothesis as a solution to the short baseline neutrino anomalies

We compare the solutions to the short baseline neutrino anomaly based on oscillations to sterile neutrinos and the Stochastic Neutrino Mixing Mechanism (SNMM) through an analysis of the present neutrino data. The SNMM suggests worse fits than a 3 + 1 sterile neutrino model, although it cannot be discarded by present data. We propose an experiment to distinguish between both solutions, based on placing a $^8$Li source inside a 5kton-yr detector (like SNO). We studied the sensitivity of such an experiment, which makes it possible to discriminate within $2σ$ the SNMM from the 3+1 sterile hypothesis for some particular values of the relevant parameters in 5 kton-years of running.

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arXiv2014

Constraining the Violation of Equivalence Principle with IceCube Atmospheric Neutrino Data

The recent high-statistics high-energy atmospheric neutrino data collected by IceCube open a new window to probe new physics scenarios that are suppressed in lower energy neutrino experiments. In this paper we analyze the IceCube atmospheric neutrino data to constrain the Violation of Equivalence Principle (VEP) in the framework of three neutrinos with non-universal gravitational couplings. In this scenario the effect of VEP on neutrino oscillation probabilities can be parametrized by two parameters $Δγ_{21}\equiv γ_2-γ_1$ and $Δγ_{31}\equiv γ_3-γ_1$, where $γ_i$'s denote the coupling of neutrino mass eigenstates to gravitational field. By analyzing the latest muon-tracks data sets of IceCube-40 and IceCube-79, besides providing the 2D allowed regions in $(ϕΔγ_{21},ϕΔγ_{31})$ plane, we obtain the upper limits $|ϕΔγ_{21}| < 9.1\times 10^{-27}$ (at 90\% C.L.) which improves the previous limit by $\sim4$ orders of magnitude and $|ϕΔγ_{31}| \lesssim 6\times 10^{-27}$ (at 90\% C.L.) which improves the current limit by $\sim1$ order of magnitude. Also we discuss in detail and analytically the effect of VEP on neutrino oscillation probabilities.

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arXiv2014

Quantum Dissipation and CP Violation in MINOS

We use the open quantum systems framework to analyze the MINOS data and perform this analysis considering two different dissipative models. In the first model, the dissipative parameter describes decoherence effect and in the second, the dissipative parameter describes other dissipative effects including decoherence. With the second model it is possible to study CP violation since we consider Majorana neutrinos. The analysis from the muon neutrino and antineutrino beam assigns different values to all the parameters of the models, but consistent with each other. Assuming that neutrinos are equivalent to antineutrinos, the global analysis presents nonvanishing Majorana CP phase depending on the energetic parameterization of the dissipative parameter.

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arXiv2014

Mass Varying Neutrinos in Supernovae

We study the consequences on the neutrino oscillation parameter space, mixing angle ($\tan^2θ$) and vacuum mass difference ($Δm^2_0$), when mass varying neutrino (MaVaN) models are assumed in a supernova environment. We consider electronic to sterile channels $ν_e \rightarrow ν_s$ and $\barν_e \rightarrow \barν_s$ in two-flavor scenario. In a given model of MaVaN mechanism, we induce a position-dependent effective mass difference, $Δ\tilde m^2(r)$, where $r$ is the distance from the supernova core, that changes the neutrino and anti-neutrino flavour conversion probabilities. We study the constraints on the mixing angle and vacuum mass difference coming from r-process and the SN1987A data. Our result is the appearance of a new exclusion region for very small mixing angles, $\tan^2θ=10^{-6}-10^{-2}$, and small vacuum mass difference, $Δm^2_0=~1-20$ eV$^2$, due the MaVaN mechanism.

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arXiv2013

Limits in late time conversion of cold dark matter into dark radiation

Structure formation creates high temperature and density regions in the Universe that allow the conversion of matter into more stable states, with a corresponding emission of relativistic matter and radiation. An example of such a mechanism is the supernova event, that releases relativistic neutrinos corresponding to 99% of the binding energy of remnant neutron star. We take this phenomena as a starting point for an assumption that similar processes could occur in the dark sector, where structure formation would generate a late time conversion of cold dark matter into a relativistic form of dark matter. We performed a phenomenological study about the limits of this conversion, where we assumed a transition profile that is a generalized version of the neutrino production in supernovae events. With this assumption, we obtained an interesting modification for the constraint over the cold dark matter density. We show that when comparing with the standard ΛCDM cosmology, there is no preference for conversion, although the best fit is within 1σ from the standard model best fit. The methodology and the results obtained qualify this conversion hypothesis, from the large scale structure point of view, as a viable and interesting model to be tested in the future with small scale data, and mitigate discrepancies between observations at this scale and the pure cold dark matter model.

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arXiv2013

Stochastic Neutrino Mixing Mechanism

We propose a mechanism which provides an explanation of the Gallium and antineutrino reactor anomalies. Differently from original Pontecorvo's hypothesis, this mechanism is based on the phenomenological assumption in which the admixture of neutrino mass eigenstates in the moments of neutrino creation and detection can assume different configurations around the admixture parametrized by the usual values of the mixing angles $θ_{12}$, $θ_{23}$ and $θ_{13}$. For simplicity, we assume a Gaussian distribution for the mixing angles in such a way that the average value of this distribution is given by the usual values of the mixing angles and the width of the Gaussian is denoted by $α$. We show that the proposed mechanism provides a possible explanation for very short-baseline neutrino disappearance, necessary to accommodate Gallium and antineutrino reactor anomalies, which is not allowed in usual neutrino oscillations based on Pontecorvo's original hypotheses. We also can describe high-energy oscillation experiments, like LSND, Fermi and NuTeV, assuming a weakly energy dependent width parameter, $α(E)$, that nicely fits all experimental results.

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arXiv2011

Non-standard neutrinos interactions in a 331 model with minimum Higgs sector

We present a detailed analysis of a class of extensions to the SM Gauge chiral symmetry $SU(3)_{C}\times SU(3)_{L}\times U(1)_{X}$ (331 model), where the neutrino electroweak interaction with matter via charged and neutral current is modified through new gauge bosons of the model. We found the connections between the non-standard contributions on 331 model with non-standard interactions. Through limits of such interactions in cross section experiments we constrained the parameters of the model, obtaining that the new energy scale of this theory should obey $V>1.3$ TeV and the new bosons of the model must have masses greater than 610 GeV.

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arXiv2011

Solar neutrino spectrum, sterile neutrinos and additional radiation in the Universe

Recent results from the SNO, Super-Kamiokande and Borexino experiments do not show the expected upturn of the energy spectrum of events (the ratio $R \equiv N_{obs}/N_{SSM}$) at low energies. At the same time, cosmological observations testify for possible existence of additional relativistic degrees of freedom in the early Universe: $ΔN_{eff} = 1 - 2$. These facts strengthen the case of very light sterile neutrino, $ν_s$, with $Δm^2_{01} \sim (0.7 - 2) \cdot 10^{-5}$ eV$^2$, which mixes weakly with the active neutrinos. The $ν_s$ mixing in the mass eigenstate $ν_1$ characterized by $\sin^2 2α\sim 10^{-3}$ can explain an absence of the upturn. The mixing of $ν_s$ in the eigenstate $ν_3$ with $\sin^2 β\sim 0.1$ leads to production of $ν_s$ via oscillations in the Universe and to additional contribution $ΔN_{eff} \approx 0.7 - 1$ before the big bang nucleosynthesis and later. Such a mixing can be tested in forthcoming experiments with the atmospheric neutrinos as well as in future accelerator long baseline experiments. It has substantial impact on conversion of the supernova neutrinos.

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arXiv2006

Effects of Environment Dependence of Neutrino Mass versus Solar and Reactor Neutrino Data

In this work we study the phenomenological consequences of the environment dependence of neutrino mass on solar and reactor neutrino phenomenology. Such dependence can be induced, for example, by Yukawa interactions with a light scalar particle which couples to neutrinos and matter and it is expected, among others, in mass varying neutrino scenarios. Under the assumption of one mass scale dominance, we perform a global analysis of solar and KamLAND neutrino data which depends on 4 parameters: the two standard oscillation parameters, Delta m^2 and tan^2(theta), and two new coefficients, which parameterize the environment dependence of the neutrino mass. We find that, generically, the inclusion of the environment dependent terms does not lead to a very statistically significant improvement on the description of the data in the most favoured MSW LMA (or LMA-I) region. It does, however, substantially improve the fit in the high-Delta m^2 LMA (or LMA-II) region which can be allowed at 98.9% CL. Conversely the analysis allow us to place stringent constraints on the size of the environment dependence terms, which can be translated on a bound on the product of the effective neutrino-scalar (lambda^ν) and matter-scalar (lambda^N) Yukawa couplings, as a function of the scalar field mass (m_S) in these models.

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arXiv2005

Random magnetic fields inducing solar neutrino spin-flavor precession in a three generation context

We study the effect of random magnetic fields in the spin-flavor precession of solar neutrinos in a three generation context, when a non-vanishing transition magnetic moment is assumed. While this kind of precession is strongly constrained when the magnetic moment involves the first family, such constraints do not apply if we suppose a transition magnetic moment between the second and third families. In this scenario we can have a large non-electron anti-neutrino flux arriving on Earth, which can lead to some interesting phenomenological consequences, as, for instance, the suppression of day-night asymmetry. We have analyzed the high energy solar neutrino data and the KamLAND experiment to constrain the solar mixing angle, and solar mass difference, and we have found a larger shift of allowed values.

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arXiv2004

Toward precision measurements in solar neutrinos

Solar neutrino physics enters a stage of precision measurements. In this connection we present a precise analytic description of the neutrino conversion in the context of LMA MSW solution of the solar neutrino problem. Using the adiabatic perturbation theory we derive an analytic formula for the $ν_e$ survival probability which takes into account the non-adiabatic corrections and the regeneration effect inside the Earth. The probability is averaged over the neutrino production region. We find that the non-adiabatic corrections are of the order $10^{-9}-10^{-7}$. Using the formula for the Earth regeneration effect we discuss features of the zenith angle dependence of the $ν_e$ flux. In particular, we show that effects of small structures at the surface of the Earth can be important.

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