Mixing Matrix Elements Research Articles

Enhanced mixing of intrinsic states in deformed Hf nuclei

Excited low-spin, nonyrast states in Hf170,172,174 were populated in β+/ε decay and studied through off-beam γ-ray spectroscopy. New coincidence data allowed for a substantial revision of the level schemes of Hf170,172 and a confirmation of the level scheme of Hf174. The Hf isotopes represent a unique situation in which a crossing of collective intrinsic excitations occurs, enhancing significantly the effects of mixing. Using branching ratios from excited 2+ states, this mixing is followed and studied. The resulting mixing matrix elements are found to be ~30 keV—an order of magnitude larger than estimated previously for nearby nuclei. In the case of Hf170, the 2β+ and 2γ+ level are shown to be completely mixed.8 MoreReceived 19 February 2008DOI:https://doi.org/10.1103/PhysRevC.77.054304©2008 American Physical Society

BOUNDS ON QUARK MASS MATRICES ELEMENTS DUE TO MEASURED PROPERTIES OF THE MIXING MATRIX AND PRESENT VALUES OF THE QUARK MASSES

We obtain constraints on possible structures of mass matrices in the quark sector by using as experimental restrictions the determined values of the quark masses at the MZ energy scale, the magnitudes of the quark mixing matrix elements V ud , V us , V cd and V cs , and the Jarlskog invariant J(V). Different cases of specific mass matrices are examined in detail. The quality of the fits for the Fritzsch- and Stech-type mass matrices is about the same with χ2/ d.o.f. = 4.23/3 = 1.41 and χ2/ d.o.f. = 9.10/4 = 2.28, respectively. The fit for a simple generalization (one extra parameter) of the Fritzsch type matrices, in the physical basis, is much better with χ2/ d.o.f. = 1.89/4 = 0.47. For comparison we also include the results using the quark masses at the 2 GeV energy scale. The fits obtained at this energy scale are similar to that at MZ energy scale, implying that our results are unaffected by the evolution of the quark masses from 2 to 91 GeV.

Novel statistical approach to blind recovery of earth signal and source wavelet using independent component analysis

This paper provides a new statistical approach to blind recovery of both earth signal and source wavelet given only the seismic traces using independent component analysis (ICA) by explicitly exploiting the sparsity of both the reflectivity sequence and the mixing matrix. Our proposed blind seismic deconvolution algorithm consists of three steps. Firstly, a transformation method that maps the seismic trace convolution model into multiple inputs multiple output (MIMO) instantaneous ICA model using zero padding matrices has been proposed. As a result the nonzero elements of the sparse mixing matrix contain the source wavelet. Secondly, whitening the observed seismic trace by incorporating the zero padding matrixes is conducted as a pre-processing step to exploit the sparsity of the mixing matrix. Finally, a novel logistic function that matches the sparsity of reflectivity sequence distribution has been proposed and fitted into the information maximization algorithm to obtain the demixing matrix. Experimental simulations have been accomplished to verify the proposed algorithm performance over conventional ICA algorithms such as Fast ICA and JADE algorithm. The mean square error (MSE) of estimated wavelet and estimated reflectivity sequence shows the improvement of proposed algorithm.

High-j single-particle neutron states outside the [formula omitted] core

The behaviour of the i13/2 and h9/2 single-neutron strength was studied with the (α,He3) reaction on 138Ba, 140Ce, 142Nd and 144Sm targets at a beam energy of 51 MeV. The separation between the single-neutron states i13/2 and h9/2 was measured in N=83 nuclei with changing proton number. To this end spectroscopic factors for states populated in high-ℓ transfer were extracted from the data. Some mixing of ℓ=5 and 6 strength was observed with states that are formed by coupling the f7/2 state to the 2+ and 3− vibrational states and the mixing matrix elements were found to be remarkably constant. The centroids of the strength indicate a systematic change in the energies of the i13/2 and h9/2 single-neutron states with increasing proton number that is in quantitative agreement with the effects expected from the tensor interaction.

Plaquette invariants and the flavour symmetric description of quark and neutrino mixings

We present a complete set of new flavour-permutation-symmetric mixing observables. We give expressions for these “plaquette invariants”, both in terms of the mixing matrix elements alone, and in terms of manifestly Jarlskog-invariant functions of fermion mass matrices. While these quantities are unconstrained in the Standard Model, we point out that remarkably, in the case of leptonic mixing, the values of most of them are consistent with zero, corresponding to certain phenomenological symmetries. We give examples of their application to the flavour-symmetric description of both lepton and quark mixings, showing for the first time how to construct explicitly weak-basis invariant constraints on the mass matrices, for a number of phenomenologically valid mixing ansätze.

Systematic parameter space search of extended quark–lepton complementarity

We systematically investigate the parameter space of neutrino and charged lepton mass matrices for textures motivated by an extended quark–lepton complementarity. As the basic hypothesis, we postulate that all mixing angles in U ℓ and U ν be either maximal or described by powers of a single small quantity ϵ ≃ θ C . All mass hierarchies are described by this ϵ as well. In this study, we do not assume specific forms for U ℓ and U ν , such as large mixing coming from the neutrino sector only. We perform a systematic scan of the 262 144 generated mixing matrices for being compatible with current experimental data, and find a sample of 2468 possibilities. We then analyze and classify the effective charged lepton and neutrino mass textures, where we especially focus on a subset of models getting under pressure for small θ 13 . In addition, we predict the mixing angle distributions from our sample of all valid textures, and study the robustness of this prediction. We also demonstrate how our procedure can be extended to predictions of the Dirac and Majorana phases in U PMNS . For instance, we find that CP conservation in neutrino oscillations is preferred, and we can impose a lower bound on the mixing matrix element for 0 ν β β decay.

Matrix elements of the complete set ofΔB=2andΔC=2operators in heavy meson chiral perturbation theory

Using heavy meson chiral perturbation theory, we consider the light quark mass and spatial volume dependence of the matrix elements of ΔB = 2 and AC = 2 four-quark operators relevant for B 0 (s) - B 0 (s) and D 0 - D 0 mixing, and the B s meson width difference. Our results for these matrix elements are obtained in the N f = 2 + 1 partially quenched theory, which becomes full QCD in the limit where sea and valence quark masses become equal. They can be used in extrapolation of lattice calculations of these matrix elements to the physical light quark masses and to infinite volume. An important conclusion of this paper is that the chiral extrapolations for matrix elements of heavy-light meson mixing beyond the standard model, and those relevant for the B s width difference are more complicated than that for the standard model mixing matrix elements.

PMNS Matrix Elements Without Assuming Unitarity

We study how strongly the determination of the elements of the leptonic mixing matrix relies in assuming its unitarity. We show that oscillation experiments are only sensitive to half of the matrix elements, while the other half are usually derived from them imposing unitarity. We also find that the constraints on unitarity deviations from weak decays combined with the matrix elements measured in oscillations is enough to bound all the matrix elements. Precision improvements within future facilities are discussed as well.

γ-ray multipolarimetry between low-spin states ofCe136: Search for the21,ms+one-phonon mixed-symmetry state

An experiment was performed on $^{136}\mathrm{Ce}$ to measure $E2/M1$ multipole mixing ratios using the method of $\ensuremath{\gamma}\ensuremath{\gamma}$ angular correlations. The low-spin states of interest were populated by \ensuremath{\beta} decay from the ${2}^{+}$ ground state of $^{136}\mathrm{Pr}$ that has a half-life of 13.1 min. Emitted \ensuremath{\gamma} rays were detected with the Stony Brook cube germanium detector array. Five $E2/M1$ multipole mixing ratios were measured for the first time and two spin and parity quantum numbers were assigned. Candidates for the ${2}_{1,\mathrm{ms}}^{+}$ state of $^{136}\mathrm{Ce}$ were identified from large $M1$ fractions in the $E2/M1$ multipole mixing ratios. The ${2}_{1,\mathrm{ms}}^{+}$ state is suggested to be fragmented between the closely lying ${2}_{3}^{+}$ and ${2}_{4}^{+}$ states. A two state mixing scenario is employed for deducing an $F$-spin mixing matrix element of 43(5) keV.

Getting Information on|Ue3|2from Neutrinoless Double Beta Decay

We consider the possibility to gain information on the lepton mixing matrix element|Ue3|from an improved experimental limit on the effective neutrino mass governing neutrinoless double beta decay. We show that typically a lower limit on|Ue3|as a function of the smallest neutrino mass can be set. Furthermore, we give the values of the sum of neutrino masses and|Ue3|which are allowed and forbidden by an experimental upper limit on the effective mass. Alternative explanations for neutrinoless double beta decay, Dirac neutrinos or unexplained cosmological features would be required if future measurements showed that the values lie in the respective regions. Moreover, we show that a measurement of|Ue3|from neutrinoless double beta decay is very difficult due to the expected errors on the effective mass and the oscillation parameters.

Unitarity of the leptonic mixing matrix

We determine the elements of the leptonic mixing matrix, without assuming unitarity, combining data from neutrino oscillation experiments and weak decays. To that end, we first develop a formalism for studying neutrino oscillations in vacuum and matter when the leptonic mixing matrix is not unitary. To be conservative, only three light neutrino species are considered, whose propagation is generically affected by non-unitary effects. Precision improvements within future facilities are discussed as well.

Anomalous Isomeric Decays inLu174as a Probe ofKMixing and Interactions in Deformed Nuclei

A K(pi)=13+, 280 ns four-quasiparticle isomer in the odd-odd nucleus 174Lu has been identified and characterized. The isomer decays to both K(pi)=7(+) and K(pi)=0(+) rotational bands obtained from the parallel and antiparallel coupling of the proton 7/2+[404] and neutron 7/2+[633] orbitals. K mixing caused by particle-rotation coupling explains the anomalously fast transition rates to the 7+ band but those to the 0+ band are caused by a chance degeneracy between the isomer and a collective state, allowing the mixing matrix element for a large K difference to be deduced.

What fraction of boron-8 solar neutrinos arrive at the Earth as aν2mass eigenstate?

We calculate the fraction of $^{8}\mathrm{B}$ solar neutrinos that arrive at the Earth as a ${\ensuremath{\nu}}_{2}$ mass eigenstate as a function of the neutrino energy. Weighting this fraction with the $^{8}\mathrm{B}$ neutrino energy spectrum and the energy dependence of the cross section for the charged current interaction on deuteron with a threshold on the kinetic energy of the recoil electrons of 5.5 MeV, we find the integrated weighted fraction of ${\ensuremath{\nu}}_{2}$'s to be $(91\ifmmode\pm\else\textpm\fi{}2)%$ at the 95% CL. This energy weighting procedure corresponds to the charged current response of the Sudbury Neutrino Observatory (SNO). We have used SNO's current best fit values for the solar mass squared difference and the mixing angle, obtained by combining the data from all solar neutrino experiments and the reactor data from KamLAND. The uncertainty on the ${\ensuremath{\nu}}_{2}$ fraction comes primarily from the uncertainty on the solar $\ensuremath{\delta}{m}^{2}$ rather than from the uncertainty on the solar mixing angle or the standard solar model. Similar results for the Super-Kamiokande experiment are also given. We extend this analysis to three neutrinos and discuss how to extract the modulus of the Maki-Nakagawa-Sakata mixing matrix element ${\mathrm{U}}_{e2}$ as well as place a lower bound on the electron number density in the production region for $^{8}\mathrm{B}$ solar neutrinos.

LOCAL DEMANDS ON STERILE NEUTRINOS

In a model-independent manner, we explore the local implications of a single neutrino oscillation measurement which cannot be reconciled within a three-neutrino theory. We examine this inconsistency for a single region of baseline to neutrino energy L/E. Assuming that sterile neutrinos account for the anomaly, we find that the local demands of this datum can require the addition to the theory of one to three sterile neutrinos. We examine the constraints which can be used to determine when more than one neutrino would be required. The results apply only to a given region of L/E. The question of the adequacy of the sterile neutrinos to satisfy a global analysis is not addressed here. Finally, using the results of a 3+2 analysis, we indicate values for unknown mixing matrix elements which would require two sterile neutrinos due to local demands only.

Measurement of the absolute branching ratio for the [formula omitted] decay with the KLOE detector

We have measured the fully inclusive K+→μ+ν(γ) absolute branching ratio with the KLOE experiment at DAΦNE, the Frascati ϕ-factory. From some 865 283 K+→μ+ν(γ) decays obtained from a sample of ∼5.2×108, ϕ-meson decays, we find BR(K+→μ+νμ(γ))=0.6366±0.0009stat.±0.0015syst., corresponding to an overall fractional error of 0.27%. Using recent lattice results on the decay constants of pseudoscalar mesons one can obtain an estimate for the CKM mixing matrix element |Vus|=0.2223±0.0026.

Large lepton mixing and nonsymmetric mass matrices with flavor2↔3symmetry

We analyze the lepton sector of a recently proposed nonsymmetric mass matrix model. Our model gives a unified description of quark and lepton with the same texture form based on an extended flavor $2\ensuremath{\leftrightarrow}3$ symmetry with a phase. By investigating possible types of assignment for masses, we find that the model can lead to large lepton mixings which are consistent with experimental values. We also find that the model predicts a very small value, $1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$, for the lepton mixing matrix element square $|{U}_{13}{|}^{2}$. The $CP$-violating phases in the lepton mixing matrix and a suppression of the averaged neutrino mass in the neutrinoless double beta decay also are predicted.

EXPERIMENTAL NEUTRINO PHYSICS

The current experimental status of neutrino physics is reviewed. It contains the evidences for a non-vanishing neutrino rest mass from neutrino oscillation searches. In addition an outlook is given on determining the various mixing matrix elements and mass differences more precisely with new experiments. Of special interest is the value of the mixing angle θ13 determining the possibility of detecting leptonic CP violation in the future. The prospect for absolute mass measurements using beta and double beta decay as well as cosmological observations is presented.

CP violation, an experimental perspective

I present a review of current and near-future experimental investigations of CP violation. In this review, I cover limits on particle electric dipole moments (EDMs) and CP violation studies in the K and B systems. The wealth of results from the new B factories provide impressive constraints on the CKM quark mixing matrix elements. Current and future measurements are focusing on processes dominated by loop diagrams, which probe physics at high mass scales in low-energy experiments.

Reconstruction of the neutrino mixing matrix and leptonic unitarity triangles from long-baseline neutrino oscillations

We derive a new set of sum rules between the neutrino mass and mixing parameters in vacuum and their effective counterparts in matter. The moduli of nine genuine lepton mixing matrix elements can then be calculated in terms of the matter-corrected ones, and the latter can directly be determined from a variety of long-baseline neutrino oscillations. We show that it is possible to reconstruct the leptonic unitarity triangles and CP violation in a similar parametrization-independent way.

Prediction for quark mixing from universal quark and lepton mass matrices with flavor2↔3symmetry

We propose a mass matrix model that gives a unified description of a quark and lepton with the same texture form based on a flavor $2\ensuremath{\leftrightarrow}3$ symmetry. The model is in contrast with the conventional picture that the mass matrix forms in the quark sector will take somewhat different structures from those in the lepton sector. By investigating possible types of assignment for masses, we find that our quark mass matrices can lead to small CKM quark mixings which are consistent with experimental values. We also find some phase-parameter-independent relations among CKM quark mixing matrix elements.