arXiv subjects

Yu-Feng Li

Publications and source records attributed to Yu-Feng Li.

At least 127 records · Page 7Linked to original sources

arXiv2016

Looking into Analytical Approximations for Three-flavor Neutrino Oscillation Probabilities in Matter

Motivated by tremendous progress in neutrino oscillation experiments, we derive a new set of simple and compact formulas for three-flavor neutrino oscillation probabilities in matter of a constant density. A useful definition of the $η$-gauge neutrino mass-squared difference $Δ^{}_* \equiv ηΔ^{}_{31} + (1-η) Δ^{}_{32}$ is introduced, where $Δ^{}_{ji} \equiv m^2_j - m^2_i$ for $ji = 21, 31, 32$ are the ordinary neutrino mass-squared differences and $0 \leq η\leq 1$ is a real and positive parameter. Expanding neutrino oscillation probabilities in terms of $α\equiv Δ^{}_{21}/Δ^{}_*$, we demonstrate that the analytical formulas can be remarkably simplified for $η= \cos^2 θ^{}_{12}$, with $θ_{12}^{}$ being the solar mixing angle. As a by-product, the mapping from neutrino oscillation parameters in vacuum to their counterparts in matter is obtained at the order of ${\cal O}(α^2)$. Finally, we show that our approximate formulas are not only valid for an arbitrary neutrino energy and any baseline length, but also still maintaining a high level of accuracy.

hep-ph↗

arXiv2016

Getting the Most from Detection of Galactic Supernova Neutrinos in Future Large Liquid-Scintillator Detectors

Future large liquid-scintillator detectors can be implemented to observe neutrinos from a core-collapse supernova (SN) in our galaxy in various reaction channels: (1) The inverse beta decay $\overlineν^{}_e + p \to n + e^+$; (2) The elastic neutrino-proton scattering $ν+ p \to ν+ p$; (3) The elastic neutrino-electron scattering $ν+ e^- \to ν+ e^-$; (4) The charged-current $ν^{}_e$ interaction $ν^{}_e + {^{12}}{\rm C} \to e^- + {^{12}}{\rm N}$; (5) The charged-current $\overlineν^{}_e$ interaction $\overlineν^{}_e + {^{12}}{\rm C} \to e^+ + {^{12}}{\rm B}$; (6) The neutral-current interaction $ν+ {^{12}}{\rm C} \to ν+ {^{12}}{\rm C}^*$. The less abundant $^{13}{\rm C}$ atoms in the liquid scintillator are also considered as a target, and both the charged-current interaction $ν^{}_e + {^{13}}{\rm C} \to e^- + {^{13}}{\rm N}$ and the neutral-current interaction $ν+ {^{13}}{\rm C} \to ν+ {^{13}}{\rm C}^*$ are taken into account. In this work, we show for the first time that a global analysis of all these channels at a single {liquid-}scintillator detector, such as Jiangmen Underground Neutrino Observatory (JUNO), is very important to test the average-energy hierarchy of SN neutrinos and how the total energy is partitioned among neutrino flavors. In addition, the dominant channels for reconstructing neutrino spectra and the impact of other channels are discussed in great detail.

hep-ph↗

arXiv2016

Jiangmen Underground Neutrino Observatory: Status and Prospectives

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kton liquid scintillator (LS) detector, which is planed to determine the neutrino mass hierarchy and measure the oscillation parameters at the sub-percent level using reactor antineutrino oscillations. As a multipurpose neutrino experiment, JUNO is also capable of measuring supernova burst neutrinos, the diffuse supernova neutrino background, geo-neutrinos, solar neutrinos and atmospheric neutrinos. After a brief introduction to the physics motivation, we discuss the status of the JUNO project, including the design of the detector systems. Finally the latest civil progress and future prospectives are also highlighted.

physics.ins-det↗

arXiv2016

Direct detection of relic active and sterile neutrinos

Both active and sterile sub-eV neutrinos can form the cosmic neutrino background in the early Universe. We consider the beta-decaying (e.g., $^3$H) and EC-decaying (e.g., $^{163}$Ho) nuclei as the promising targets to capture relic neutrinos in the laboratory. We calculate the capture rates of relic electron neutrinos and antineutrinos against the corresponding beta decay or electron capture (EC) decay backgrounds in the (3+$N_{\rm s}$) flavor mixing scheme, and discuss the future prospect in terms of the PTOLEMY project. We stress that such direct measurements of hot DM might not be hopeless in the long term.

astro-ph.CO↗

arXiv2016

Terrestrial matter effects on reactor antineutrino oscillations at JUNO or RENO-50: how small is small?

We have carefully examined, in both analytical and numerical ways, how small the terrestrial matter effects can be in a given medium-baseline reactor antineutrino oscillation experiment like JUNO or RENO-50. Taking the ongoing JUNO experiment for example, we show that the inclusion of terrestrial matter effects may reduce the sensitivity of the neutrino mass ordering measurement by Δχ^2_{\rm MO} \simeq 0.6, and a neglect of such effects may shift the best-fit values of the flavor mixing angle θ_{12} and the neutrino mass-squared difference Δ_{21} by about 1σto 2σin the future data analysis. In addition, a preliminary estimate indicates that a 2σsensitivity of establishing the terrestrial matter effects can be achieved for about 10 years of data taking at JUNO with the help of a proper near detector implementation.

hep-ph↗

arXiv2016

Potential of Geo-neutrino Measurements at JUNO

The flux of geoneutrinos at any point on the Earth is a function of the abundance and distribution of radioactive elements within our planet. This flux has been successfully detected by the 1-kt KamLAND and 0.3-kt Borexino detectors with these measurements being limited by their low statistics. The planned 20-kt JUNO detector will provide an exciting opportunity to obtain a high statistics measurement, which will provide data to address several questions of geological importance. This paper presents the JUNO detector design concept, the expected geo-neutrino signal and corresponding backgrounds. The precision level of geo-neutrino measurements at JUNO is obtained with the standard least-squares method. The potential of the Th/U ratio and mantle measurements is also discussed.

physics.ins-det↗

arXiv2016

Mass hierarchy sensitivity of medium baseline reactor neutrino experiments with multiple detectors

We report the neutrino mass hierarchy (MH) sensitivity of medium baseline reactor neutrino experiments with multiple detectors. Sensitivity of determining the MH can be significantly improved by adding a near detector and combining both the near and far detectors. The size of the sensitivity improvement is related to accuracy of the individual mass-splitting measurements and requires strict control on the relative energy scale uncertainty of the near and far detectors. We study the impact of both baseline and target mass of the near detector on the combined sensitivity. A figure-of-merit is defined to optimize the baseline and target mass of the near detector and the optimal selections are $\sim$13~km and $\sim$4~kton respectively for a far detector with the 20~kton target mass and 52.5~km baseline. As typical examples of future medium baseline reactor neutrino experiments, the optimal location and target mass of the near detector are selected for JUNO and RENO-50. Finally, we discuss distinct effects of the neutrino spectrum uncertainty for setups of a single detector and double detectors, which indicate that the spectrum uncertainty can be well constrained in the presence of the near detector.

physics.ins-det↗

arXiv2016

Neutrino Oscillation Probabilities in Matter with Direct and Indirect Unitarity Violation in the Lepton Mixing Matrix

In the presence of both direct and indirect unitarity violation in the lepton mixing matrix, we derive a complete set of series expansion formulas for neutrino oscillation probabilities in matter of constant density. Expansions in the mass hierarchy parameter $α\equiv Δm_{21}^{2} / Δm_{31}^{2}$ and those unitarity violation parameters $s^{2}_{ij}$ (for i = 1, 2, 3 and j = 4, 5, 6) up to the first order are studied in this paper. We analyse the accuracy of the analytical series expansion formulas in different regions of L / E. A detailed numerical analysis is also performed, of which the different effects of the direct and the indirect unitarity violation are particularly emphasized. We also study in this paper the summed $ν^{}_α \rightarrow ν^{}_{e, ν, τ}$ probabilities, whose deviation from the unity provides a definite signal of the unitarity violation.

hep-ph↗

arXiv2015

Electromagnetic neutrinos in laboratory experiments and astrophysics

An overview of neutrino electromagnetic properties, which open a door to the new physics beyond the Standard Model, is given. The effects of neutrino electromagnetic interactions both in terrestrial experiments and in astrophysical environments are discussed. The experimental bounds on neutrino electromagnetic characteristics are summarized. Future astrophysical probes of electromagnetic neutrinos are outlined.

hep-ph↗

arXiv2015

Constraining Absolute Neutrino Masses via Detection of Galactic Supernova Neutrinos at JUNO

A high-statistics measurement of the neutrinos from a galactic core-collapse supernova is extremely important for understanding the explosion mechanism, and studying the intrinsic properties of neutrinos themselves. In this paper, we explore the possibility to constrain the absolute scale of neutrino masses $m^{}_ν$ via the detection of galactic supernova neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO) with a 20 kiloton liquid-scintillator detector. In assumption of a nearly-degenerate neutrino mass spectrum and a normal mass ordering, the upper bound on the absolute neutrino mass is found to be $m^{}_ν< (0.83 \pm 0.24)~{\rm eV}$ at the 95% confidence level for a typical galactic supernova at a distance of 10 kpc, where the mean value and standard deviation are shown to account for statistical fluctuations. For comparison, we find that the bound in the Super-Kamiokande experiment is $m^{}_ν< (0.94 \pm 0.28)~{\rm eV}$ at the same confidence level. However, the upper bound will be relaxed when the model parameters characterizing the time structure of supernova neutrino fluxes are not exactly known, and when the neutrino mass ordering is inverted.

hep-ph↗

arXiv2015

Detection Prospects of the Cosmic Neutrino Background

The existence of the cosmic neutrino background (CnuB) is a fundamental prediction of the standard Big Bang cosmology. Although current cosmological probes provide indirect observational evidence, the direct detection of the CnuB in a laboratory experiment is a great challenge to the present experimental techniques. We discuss the future prospects for the direct detection of the CnuB, with the emphasis on the method of captures on beta-decaying nuclei and the PTOLEMY project. Other possibilities using the electron-capture (EC) decaying nuclei, the annihilation of extremely high-energy cosmic neutrinos (EHEC\nus) at the Z-resonance, and the atomic de-excitation method are also discussed in this review.

hep-ph↗

arXiv2015

Shifts of neutrino oscillation parameters in reactor antineutrino experiments with non-standard interactions

We discuss reactor antineutrino oscillations with non-standard interactions (NSIs) at the neutrino production and detection processes. The neutrino oscillation probability is calculated with a parametrization of the NSI parameters by splitting them into the averages and differences of the production and detection processes respectively. The average parts induce constant shifts of the neutrino mixing angles from their true values, and the difference parts can generate the energy (and baseline) dependent corrections to the initial mass-squared differences. We stress that only the shifts of mass-squared differences are measurable in reactor antineutrino experiments. Taking Jiangmen Underground Neutrino Observatory (JUNO) as an example, we analyze how NSIs influence the standard neutrino measurements and to what extent we can constrain the NSI parameters.

hep-ph↗

arXiv2014

Tests of Lorentz and CPT Violation in the Medium Baseline Reactor Antineutrino Experiment

Tests of Lorentz and CPT violation in the medium baseline reactor antineutrino experiment are presented in the framework of the Standard Model Extension (SME). Both the spectral distortion and sidereal variation are employed to derive the limits of Lorentz violation (LV) coefficients. We do the numerical analysis of the sensitivity of LV coefficients by taking the Jiangmen Underground Neutrino Observatory (JUNO) as an illustration, which can improve the sensitivity by more than two orders of magnitude compared with the current limits from reactor antineutrino experiments.

hep-ph↗

arXiv2014

MOMENT: a muon-decay medium-baseline neutrino beam facility

Neutrino beam with about 300 MeV in energy, high-flux and medium baseline is considered a rational choice for measuring CP violation before the more powerful Neutrino Factory will be built. Following this concept, a unique neutrino beam facility based on muon-decayed neutrinos is proposed. The facility adopts a continuous-wave proton linac of 1.5 GeV and 10 mA as the proton driver, which can deliver an extremely high beam power of 15 MW. Instead of pion-decayed neutrinos, unprecedentedly intense muon-decayed neutrinos are used for better background discrimination. The schematic design for the facility is presented here, including the proton driver, the assembly of a mercury-jet target and capture superconducting solenoids, a pion/muon beam transport line, a long muon decay channel of about 600 m and the detector concept. The physics prospects and the technical challenges are also discussed.

physics.acc-ph↗

arXiv2014

Overview of the Jiangmen Underground Neutrino Observatory (JUNO)

The medium baseline reactor antineutrino experiment, Jiangmen Underground Neutrino Observatory (JUNO), which is being planed to be built at Jiangmen in South China, can determine the neutrino mass hierarchy and improve the precision of three oscillation parameters by one order of magnitude. The sensitivity potential on these measurements is reviewed and design concepts of the central detector are illustrated. Finally, we emphasize on the technical challenges we meet and the corresponding R&D efforts.

physics.ins-det↗

arXiv2013

Convex and Scalable Weakly Labeled SVMs

In this paper, we study the problem of learning from weakly labeled data, where labels of the training examples are incomplete. This includes, for example, (i) semi-supervised learning where labels are partially known; (ii) multi-instance learning where labels are implicitly known; and (iii) clustering where labels are completely unknown. Unlike supervised learning, learning with weak labels involves a difficult Mixed-Integer Programming (MIP) problem. Therefore, it can suffer from poor scalability and may also get stuck in local minimum. In this paper, we focus on SVMs and propose the WellSVM via a novel label generation strategy. This leads to a convex relaxation of the original MIP, which is at least as tight as existing convex Semi-Definite Programming (SDP) relaxations. Moreover, the WellSVM can be solved via a sequence of SVM subproblems that are much more scalable than previous convex SDP relaxations. Experiments on three weakly labeled learning tasks, namely, (i) semi-supervised learning; (ii) multi-instance learning for locating regions of interest in content-based information retrieval; and (iii) clustering, clearly demonstrate improved performance, and WellSVM is also readily applicable on large data sets.

cs.LG↗

arXiv2013

Unambiguous Determination of the Neutrino Mass Hierarchy Using Reactor Neutrinos

Determination of the neutrino mass hierarchy in a reactor neutrino experiment at medium baseline is discussed. Observation of the interference effects between the Δm^2_{31} and Δm^2_{32} oscillations enables a relative measurement independent of the knowledge of the absolute mass-squared difference. With a 20 kton liquid scintillator detector of 3%/\sqrt{E(MeV)} energy resolution, the Daya Bay II Experiment at a baseline of \sim 50 km from reactors of total thermal power 36 GW can determine the mass hierarchy at a confidence level of Δχ^2_{MH} \sim (10-12) (3-3.5 σ) in 6 years after taking into account the real spatial distribution of reactor cores. We show that the unknown residual energy non-linearity of the liquid scintillator detector has limited impact on the sensitivity due to the self-calibration of small oscillation peaks. Furthermore, an extra increase of Δχ^2_{MH} \simeq 4(9) can be obtained, by including the precise measurement of the effective mass-squared difference Δm^2_{μμ} of expected relative error 1.5% (1%) from ongoing long-baseline muon neutrino disappearance experiments. The sensitivities from the interference and from absolute measurements can be cross checked. When combining these two, the mass hierarchy can be determined at a confidence level of Δχ^2_{MH} \sim (15-20) (4 σ) in 6 years.

hep-ex↗

arXiv2012

Improved Bound for the Nystrom's Method and its Application to Kernel Classification

We develop two approaches for analyzing the approximation error bound for the Nyström method, one based on the concentration inequality of integral operator, and one based on the compressive sensing theory. We show that the approximation error, measured in the spectral norm, can be improved from $O(N/\sqrt{m})$ to $O(N/m^{1 - ρ})$ in the case of large eigengap, where $N$ is the total number of data points, $m$ is the number of sampled data points, and $ρ\in (0, 1/2)$ is a positive constant that characterizes the eigengap. When the eigenvalues of the kernel matrix follow a $p$-power law, our analysis based on compressive sensing theory further improves the bound to $O(N/m^{p - 1})$ under an incoherence assumption, which explains why the Nyström method works well for kernel matrix with skewed eigenvalues. We present a kernel classification approach based on the Nyström method and derive its generalization performance using the improved bound. We show that when the eigenvalues of kernel matrix follow a $p$-power law, we can reduce the number of support vectors to $N^{2p/(p^2 - 1)}$, a number less than $N$ when $p > 1+\sqrt{2}$, without seriously sacrificing its generalization performance.

cs.LG↗