The leptonic CP phase from muon decay at rest with two detectors

We propose a novel experimental setup for the determination of the leptonic CP-violating phase δ using the decay at rest (DAR) of μ + from a single source located at distances of 10 and 30 km from two 20 kton organic liquid scintillator detectors. The μ + are created by bombarding a target with a 9 mA beam of 800 MeV protons. With this proposal δ can be determined with a precision of 20 (15) degrees in 6 (12) years. In contrast with the DAE δ ALUS project, only a single source is required and it runs with a duty factor limited only by maintenance requirements. As a result 9 mA is the maximum instantaneous current, greatly reducing both the technological challenges and the costs

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 mν 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 mν < (0.83 ± 0.24) 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 mν < (0.94 ± 0.28) 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

Constraining anisotropy of the universe from different groups of type-Ia supernovae

Recently released Planck data and other astronomical observations show that the universe may be anisotropic on large scales. Inspired by this, anisotropic cosmological models have been proposed. We note that the Finsler–Randers spacetime provides an appropriate framework for the anisotropic cosmology. By adding an arbitrary 1-form to the Friedmann–Robertson–Walker line element, a privileged axis in the universe is picked out. The distance–redshift relation is modified to be direction-dependent. We wish that the anisotropic cosmological model may be tested crossly by independent observations. Type-Ia supernovae (SNe Ia) calibrated from four different light curve fitters are used to constrain the possible anisotropy of the universe. The magnitudes of anisotropy are all between 2–5 %, but the systematic uncertainty cannot be excluded. The directions of the privileged axis seem to differ from each other. The statistical significance is not high enough to make a convincing conclusion. Nevertheless, the <math><mrow><mn>1</mn><mi mathvariant="italic">σ</mi></mrow></math> contours in the <math><mrow><mo stretchy="false">(</mo><mi>l</mi><mo>,</mo><mi>b</mi><mo stretchy="false">)</mo></mrow></math> plane obtained from four groups of SNe Ia have an overlap, centering at <math><mrow><mrow><mo stretchy="false">(</mo><mi>l</mi><mo>,</mo><mi>b</mi><mo stretchy="false">)</mo></mrow><mo>≈</mo><mrow><mo stretchy="false">(</mo><msup><mn>170</mn><mo>∘</mo></msup><mo>,</mo><msup><mn>0</mn><mo>∘</mo></msup><mo stretchy="false">)</mo></mrow></mrow></math> . Monte Carlo simulation shows that the anisotropy is unlikely to be caused by the selection effect

Showering cosmogenic muons in a large liquid scintillator

We present the results of FLUKA simulations of the propagation of cosmogenic muons in a 20 kton spherical liquid scintillator detector underneath 700 to 900 meters of rock. A showering muon is one which deposits at least 3 GeV in the detector in addition to ionization energy. We find that 20 percent of muons are showering and a further 11 percent of muon events are muon bundles, of which more than one muon enters the detector. In this range the showering and bundle fractions are robust against changes in the depth and topography, thus the total shower and bundle rate for a given experiment can be obtained by combining our results with an estimate for the total muon flux. One consequence is that a straightforward adaptation of the full detector showering muon cuts used by KamLAND to JUNO or RENO 50 would yield a nearly vanishing detector efficiency

On the four-zero texture of quark mass matrices and its stability

We carry out a new study of quark mass matrices Mu (up-type) and Md (down-type) which are Hermitian and have four zero entries, and find a new part of the parameter space which was missed in the previous works. We identify two more specific four-zero patterns of Mu and Md with fewer free parameters, and present two toy flavor-symmetry models which can help realize such special and interesting quark flavor structures. We also show that the texture zeros of Mu and Md are essentially stable against the evolution of energy scales in an analytical way by using the one-loop renormalization-group equations

Medium baseline reactor neutrino experiments with two identical detectors

In the next 10 years medium baseline reactor neutrino experiments will attempt to determine the neutrino mass hierarchy and to precisely measure θ12 . Both of these determinations will be more reliable if data from identical detectors at distinct baselines are combined. While interference effects can be eliminated by choosing detector sites orthogonal to the reactor arrays, one of the greatest challenges facing a determination of the mass hierarchy is the detector's unknown energy response. By comparing peaks at similar energies at two identical detectors at distinct baselines, one eliminates any correlated dependence upon a monotonic energy response. In addition, a second detector leads to new hierarchy-dependent observables, such as the ratio of the locations of the maxima of the Fourier cosine transforms. A second detector at a distinct baseline also breaks the degeneracy between θ12 and the background neutrino flux from, for example, distant reactors and increases the effective target mass, which is limited by current designs to about 20 kton/detector

How to interpret a discovery or null result of the 0ν2β decay

The Majorana nature of massive neutrinos will be crucially probed in the next-generation experiments of the neutrinoless double-beta ( 0ν2β ) decay. The effective mass term of this process, ⟨m⟩ee , may be contaminated by new physics. So how to interpret a discovery or null result of the 0ν2β decay in the foreseeable future is highly nontrivial. In this paper we introduce a novel three-dimensional description of |⟨m⟩ee| , which allows us to see its sensitivity to the lightest neutrino mass and two Majorana phases in a transparent way. We take a look at to what extent the free parameters of |⟨m⟩ee| can be well constrained provided a signal of the 0ν2β decay is observed someday. To fully explore lepton number violation, all the six effective Majorana mass terms ⟨m⟩αβ (for α,β=e,μ,τ ) are calculated and their lower bounds are illustrated with the two-dimensional contour figures. The effect of possible new physics on the 0ν2β decay is also discussed in a model-independent way. We find that the result of |⟨m⟩ee| in the normal (or inverted) neutrino mass ordering case modified by the new physics effect may somewhat mimic that in the inverted (or normal) mass ordering case in the standard three-flavor scheme. Hence a proper interpretation of a discovery or null result of the 0ν2β decay may demand extra information from some other measurements

Parity violation in pre-inflationary bounce

The power suppression on large scale in the CMB TT-mode power spectrum might imply the occurrence of a pre-inflationary bounce. We calculate the circularly polarized gravitational wave, leaded by the gravitational Chern–Simons term universally appearing in particle physics and string theory, in the inflation model with the pre-inflationary bounce. The circularly polarized gravitational wave will induce TB- and EB-mode correlations at CMB last scatting surface. We find that if the pre-inflationary bounce actually occurs, the TB- and EB-mode correlations on large scale will be enhanced, while the BB-mode correlation on corresponding scales is suppressed

Estimating the mass of the hidden charm 1+(1+) tetraquark state via QCD sum rules

By using QCD sum rules, the mass of the hidden charm tetraquark [cu][c¯d¯] state with IG(JP)=1+(1+) (HCTV) is estimated, which presumably will turn out to be the newly observed charmonium-like resonance Zc+(3900) . In the calculation, contributions up to dimension eight in the operator product expansion (OPE) are taken into account. We find m1+c=(3912-153+306)MeV , which is consistent, within the errors, with the experimental observation of Zc+(3900) . Extending to the b-quark sector, m1+b=(10561-163+395)MeV is obtained. The calculational result strongly supports the tetraquark picture for the “exotic” states of Zc+(3900) and Zb+(10610)

A further study of the Frampton-Glashow-Yanagida model for neutrino masses, flavor mixing and baryon number asymmetry

In light of the latest neutrino oscillation data, we revisit the minimal scenario of type-I seesaw model, in which only two heavy right-handed Majorana neutrinos are introduced to account for both tiny neutrino masses and the baryon number asymmetry in our Universe. In this framework, we carry out a systematic study of the Frampton-Glashow-Yanagida ansatz by taking into account the renormalization-group running of neutrino mixing parameters and the flavor effects in leptogenesis. We demonstrate that the normal neutrino mass ordering is disfavored even in the minimal supersymmetric standard model with a large value of tan β , for which the running effects could be significant. Furthermore, it is pointed out that the original scenario with a hierarchical mass spectrum of heavy Majorana neutrinos contradicts with the upper bound derived from a naturalness criterion, and the resonant mechanism with nearly-degenerate heavy Majorana neutrinos can be a possible way out