scholarly journals Potential impact of sub-structure on the determination of neutrino mass hierarchy at medium-baseline reactor neutrino oscillation experiments

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Zhaokan Cheng ◽  
Neill Raper ◽  
Wei Wang ◽  
Chan Fai Wong ◽  
Jingbo Zhang
Keyword(s):  
Fine Structure ◽  
Neutrino Oscillation ◽  
Neutrino Mass ◽  
Energy Resolution ◽  
Percent Level ◽  
Mass Hierarchy ◽  
Neutrino Mixing ◽  
Near Detector ◽  
Reactor Neutrino ◽  
The Impact

AbstractIn the past decade, the precise measurement of the lastly known neutrino mixing angle $$\theta _{13}$$ θ 13 has enabled the resolution of neutrino mass hierarch (MH) at medium-baseline reactor neutrino oscillation (MBRO) experiments. Recent calculations of the reactor neutrino flux predict percent-level sub-structures in the $$\bar{\nu }_e$$ ν ¯ e spectrum due to Coulomb effects in beta decay. Such fine structure in the reactor spectrum has been an issue of concern for efforts to determine the neutrino MH for the MBRO approach, the concern being that the sub-dominant oscillation pattern used to discriminate different hierarchies will be obscured by fine structure. The energy resolutions of current reactor experiments are not sufficient to measure such fine structure, and therefore the size and location in energy of these predicted discontinuities has not been confirmed experimentally. There has been speculation that a near detector is required with sufficient energy resolution to resolve the fine structure. This article studies the impact of fine structure on the resolution of MH, based on predicted reactor neutrino spectra, using the measured spectrum from Daya Bay as a reference. We also investigate how a near detector could improve the sensitivity of neutrino MH resolution based on various assumptions of near detector energy resolution.

scholarly journals A Phenomenological Model of Effectively Oscillating Massless Neutrinos and Its Implications

2020 ◽  
Vol 240 ◽  
pp. 02002
Author(s):  
Jianlong Lu ◽  
Aik Hui Chan ◽  
Choo Hiap Oh
Keyword(s):  
Neutrino Oscillation ◽  
Neutrino Mass ◽  
Phenomenological Model ◽  
Double Beta Decay ◽  
Neutrino Masses ◽  
Mass Hierarchy ◽  
Neutrino Mixing ◽  
Open Problems ◽  
Neutrino Mass Hierarchy ◽  
Flavor Changing

We discuss an alternative picture of neutrino oscillation. In this phenomenological model, the flavor-changing phenomena of massless neutrinos arise from scattering processes between neutrinos and four types of undetected spin-0 massive particles pervading throughout the Universe, instead of neutrinos’ own nature. These scattering processes are kinematically similar to Compton scattering. One type of left-handed massless sterile neutrino is needed in order to reproduce the neutrino oscillation modes predicted in the theory of neutrino mixing. Implications of our model include the existence of sterile neu- trinos, the nonconservation of active neutrinos, the possible mismatch among three neutrino mass squared differences ∆m2ij interpreted in the theory of neutrino mixing, the spacetime dependence of neutrino oscillation, and the impossibility of neutrinoless double beta decay. Several important open problems in neutrino physics become trivial or less severe in our model, such as the smallness of neutrino masses, neutrino mass hierarchy, the mechanism responsible for neutrino masses, and the Dirac/Majorana nature of neutrinos.

scholarly journals Physics Potential of Long-Baseline Experiments

2014 ◽  
Vol 2014 ◽  
pp. 1-29 ◽  
Author(s):  
Sanjib Kumar Agarwalla
Keyword(s):  
Neutrino Oscillation ◽  
Neutrino Mass ◽  
New Physics ◽  
Mass Hierarchy ◽  
Neutrino Mixing ◽  
Neutrino Mass Hierarchy ◽  
Mixing Angle ◽  
Long Baseline ◽  
Physics Potential ◽  
Flavor Oscillation

The discovery of neutrino mixing and oscillations over the past decade provides firm evidence for new physics beyond the Standard Model. Recently,θ13has been determined to be moderately large, quite close to its previous upper bound. This represents a significant milestone in establishing the three-flavor oscillation picture of neutrinos. It has opened up exciting prospects for current and future long-baseline neutrino oscillation experiments towards addressing the remaining fundamental questions, in particular the type of the neutrino mass hierarchy and the possible presence of a CP-violating phase. Another recent and crucial development is the indication of non-maximal 2-3 mixing angle, causing the octant ambiguity ofθ23. In this paper, I will review the phenomenology of long-baseline neutrino oscillations with a special emphasis on sub-leading three-flavor effects, which will play a crucial role in resolving these unknowns. First, I will give a brief description of neutrino oscillation phenomenon. Then, I will discuss our present global understanding of the neutrino mass-mixing parameters and will identify the major unknowns in this sector. After that, I will present the physics reach of current generation long-baseline experiments. Finally, I will conclude with a discussion on the physics capabilities of accelerator-driven possible future long-baseline precision oscillation facilities.

scholarly journals Yifang Wang: high energy physics in China

2016 ◽  
Vol 3 (2) ◽  
pp. 252-256 ◽  
Author(s):  
Ling Wang ◽  
Mu-ming Poo
Keyword(s):  
Neutrino Oscillation ◽  
Particle Physics ◽  
Quantum Interference ◽  
High Energy Physics ◽  
High Energy ◽  
Electron Neutrino ◽  
Daya Bay ◽  
Mass Hierarchy ◽  
Neutrino Mixing ◽  
Energy Physics

Abstract On 8 March 2012, Yifang Wang, co-spokesperson of the Daya Bay Experiment and Director of Institute of High Energy Physics, Chinese Academy of Sciences, announced the discovery of a new type of neutrino oscillation with a surprisingly large mixing angle (θ13), signifying ‘a milestone in neutrino research’. Now his team is heading for a new goal—to determine the neutrino mass hierarchy and to precisely measure oscillation parameters using the Jiangmen Underground Neutrino Observatory, which is due for completion in 2020. Neutrinos are fundamental particles that play important roles in both microscopic particle physics and macroscopic universe evolution. The studies on neutrinos, for example, may answer the question why our universe consists of much more matter than antimatter. But this is not an easy task. Though they are one of the most numerous particles in the universe and zip through our planet and bodies all the time, these tiny particles are like ‘ghost’, difficult to be captured. There are three flavors of neutrinos, known as electron neutrino (νe), muon neutrino (νμ), and tau neutrino (ντ), and their flavors could change as they travel through space via quantum interference. This phenomenon is known as neutrino oscillation or neutrino mixing. To determine the absolute mass of each type of neutrino and find out how they mix is very challenging. In a recent interview with NSR in Beijing, Yifang Wang explained how the Daya Bay Experiment on neutrino oscillation not only addressed the frontier problem in particle physics, but also harnessed the talents and existing technology in Chinese physics community. This achievement, Wang reckons, will not be an exception in Chinese high energy physics, when appropriate funding and organization for big science projects could be efficiently realized in the future.

scholarly journals Reactor neutrino experiments: θ13 and beyond

2014 ◽  
Vol 29 (16) ◽  
pp. 1430016 ◽  
Author(s):  
Xin Qian ◽  
Wei Wang
Keyword(s):  
New Physics ◽  
Daya Bay ◽  
Neutrino Experiment ◽  
Mass Hierarchy ◽  
Neutrino Mixing ◽  
Next Generation ◽  
Short Baseline ◽  
Current Generation ◽  
Reactor Neutrino ◽  
Neutrino Experiments

We review the current-generation short-baseline reactor neutrino experiments that have firmly established the third neutrino mixing angle θ13 to be nonzero. The relative large value of θ13 (around 9°) has opened many new and exciting opportunities for future neutrino experiments. Daya Bay experiment with the first measurement of [Formula: see text] is aiming for a precision measurement of this atmospheric mass-squared splitting with a comparable precision as [Formula: see text] from accelerator muon neutrino experiments. JUNO, a next-generation reactor neutrino experiment, is targeting to determine the neutrino mass hierarchy (MH) with medium baselines (~ 50 km). Beside these opportunities enabled by the large θ13, the current-generation (Daya Bay, Double Chooz, and RENO) and the next-generation (JUNO, RENO-50, and PROSPECT) reactor experiments, with their unprecedented statistics, are also leading the precision era of the three-flavor neutrino oscillation physics as well as constraining new physics beyond the neutrino Standard Model.

scholarly journals REVIEW OF REACTOR NEUTRINO OSCILLATION EXPERIMENTS

2012 ◽  
Vol 27 (08) ◽  
pp. 1230010 ◽  
Author(s):  
C. MARIANI
Keyword(s):  
Neutrino Physics ◽  
Neutrino Oscillation ◽  
Current Status ◽  
Daya Bay ◽  
Neutrino Mixing ◽  
Mixing Angle ◽  
Double Chooz ◽  
Reactor Neutrino ◽  
Neutrino Experiments ◽  
Near Future

In this document we will review the current status of reactor neutrino oscillation experiments and present their physics potentials for measuring the θ13 neutrino mixing angle. The neutrino mixing angle θ13 is currently a high-priority topic in the field of neutrino physics. There are currently three different reactor neutrino experiments, DOUBLE CHOOZ, DAYA BAY and RENO and a few accelerator neutrino experiments searching for neutrino oscillations induced by this angle. A description of the reactor experiments searching for a nonzero value of θ13 is given, along with a discussion of the sensitivities that these experiments can reach in the near future.

scholarly journals Towards determining the neutrino mass hierarchy: weak lensing and galaxy clustering forecasts with baryons and intrinsic alignments

2020 ◽  
Vol 493 (2) ◽  
pp. 1640-1661 ◽  
Author(s):  
David Copeland ◽  
Andy Taylor ◽  
Alex Hall
Keyword(s):  
Neutrino Mass ◽  
Stage Iv ◽  
Double Beta Decay ◽  
Weak Lensing ◽  
Small Scale ◽  
Mass Hierarchy ◽  
Neutrino Mass Hierarchy ◽  
Galaxy Clustering ◽  
The Impact ◽  
Adiabatic Contraction

ABSTRACT The capacity of Stage IV lensing surveys to measure the neutrino mass sum and differentiate between the normal and inverted mass hierarchies depends on the impact of nuisance parameters describing small-scale baryonic astrophysics and intrinsic alignments. For a Euclid-like survey, we perform the first combined weak lensing and galaxy clustering Fisher analysis with baryons, intrinsic alignments, and massive neutrinos for both hierarchies. We use a matter power spectrum generated from a halo model that captures the impact of baryonic feedback and adiabatic contraction. For weak lensing, we find that baryons cause severe degradation to forecasts of the neutrino mass sum, Σ, approximately doubling σΣ. We show that including galaxy clustering constraints from Euclid and BOSS, and cosmic microwave background (CMB) Planck priors, can reduce this degradation to σΣ to 9 per cent and 16 per cent for the normal and inverted hierarchies, respectively. The combined forecasts, $\sigma _{\Sigma _{\rm {NH}}}=0.034\, \rm {eV}$ and $\sigma _{\Sigma _{\rm {IH}}}=0.034\, \rm {eV}$, preclude a meaningful distinction of the hierarchies but could be improved upon with future CMB priors on ns and information from neutrinoless double beta decay to achieve a 2σ distinction. The effect of intrinsic alignments on forecasts is shown to be minimal, with σΣ even experiencing mild improvements due to information from the intrinsic alignment signal. We find that while adiabatic contraction and intrinsic alignments will require careful calibration to prevent significant biasing of Σ, there is less risk presented by feedback from energetic events like AGN and supernovae.

scholarly journals GERDA and LEGEND: Probing the Neutrino Nature and Mass at 100 meV and beyond

Universe ◽  
2021 ◽  
Vol 7 (9) ◽  
pp. 314
Author(s):  
Carla Maria Cattadori ◽  
Francesco Salamida
Keyword(s):  
Beta Decay ◽  
Neutrino Mass ◽  
Phase Ii ◽  
Energy Resolution ◽  
Average Energy ◽  
Double Beta Decay ◽  
Mass Hierarchy ◽  
Inverted Hierarchy ◽  
Sensitivity Experiment ◽  
Background Index

The Gerda (GERmanium Detector Array) project, located at Laboratori Nazionali del Gran Sasso (LNGS), was started in 2005, a few years after the claim of evidence for the neutrinoless double beta decay (0νββ) of 76Ge to the ground state of 76Se: it is an ultra-rare process whose detection would directly establish the Majorana nature of the neutrino and provide a measurement of its mass and mass hierarchy. The aim of Gerda was to confirm or disprove the claim by an increased sensitivity experiment. After establishing the new technology of Ge detectors operated bare in liquid Argon and since 2011, Gerda efficiently collected data searching for 0νββ of 76Ge, first deploying the 76Ge-enriched detectors from two former experiments and later new detectors with enhanced signal-to-background rejection, produced from freshly 76Ge-enriched material. Since then, the Gerda setup has been upgraded twice, first in 2013–2015 and later in 2018. The period before 2013 is Phase I and that after 2015 is Phase II. Both the Gerda setup and the analysis tools evolved along the project lifetime, allowing to achieve the remarkable average energy resolution of ∼3.6 and ∼2.6 keV for Coaxial Germanium (Coax) detectors and for Broad Energy Germanium (BEGe), respectively, and the background index of 5.2−1.3+1.6 · 10−4 cts/(keV·kg·yr) in a 230 keV net range centered at Qββ. No evidence of the 0νββ decay at Qββ = 2039.1 keV has been found, hence the limit of 1.8·1026 yr on the half-life (T1/20ν) at 90% C.L. was set with the exposure of 127.2 kg·yr. The corresponding limit range for the effective Majorana neutrino mass mee has been set to 79–180 meV. The Gerda performances in terms of background index, energy resolution and exposure are the best achieved so far by 76Ge double beta decay experiments. In Phase II, Gerda succeeded in operating in a background free regime and set a world record. In 2017, the Legend Collaboration was born from the merging of the Gerda and Majorana Collaborations and resources with the aim to further improve the Gerda sensitivity. First, the Legend200 project, with a mass of up to 200 kg of 76Ge-enriched detectors, aims to further improve the background index down to <0.6 · 10−3 cts/(keV·kg·yr) to explore the Inverted Hierarchy region of the neutrino mass ordering, then the Legend1000 (1 ton of 76Ge-enriched) will probe the Normal Hierarchy. In this paper, we describe the Gerda experiment, its evolution, the data analysis flow, a selection of its results and technological achievements, and finally the design, features and challenges of Legend, the Gerda prosecutor.

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