Flavor Eigenstates Research Articles

Gold-plated mode of CP-violation in decays of Bc meson from QCD sum rules

A model-independent method based on the triangle ideology is implemented to extract the CKM-matrix angle γ in the decays of the doubly heavy long-lived meson Bc. We analyse a colour structure of diagrams and conditions to reconstruct two reference triangles by tagging the flavour and CP eigenstates of mesons in the fixed exclusive channels. The characteristic branching ratios are evaluated in the framework of QCD sum rules.

Limits on the decay-rate difference of neutralBmesons and onCP,T, andCPTviolation inB0B0oscillations

Using events in which one of two neutral B mesons from the decay of an Υ(4S) resonance is fully reconstructed, we set limits on the difference between the decay rates of the two neutral B mass eigenstates and on CP, T, and CPT violation in B0B0 mixing. The reconstructed decays, comprising both CP and flavor eigenstates, are obtained from 88 million Υ(4S)→BB¯ decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We determine six independent parameters governing oscillations (Δm,ΔΓ/Γ), CPT and CP violation (Rez,Imz), and CP and T violation (ImλCP,|q/p|), where λCP characterizes B0 and B0 decays to states of charmonium plus KS0 or KL0. The results are sgn(ReλCP)ΔΓ/Γ=−0.008±0.037(stat.)±0.018(syst.)[−0.084,0.068],|q/p|=1.029±0.013(stat.)±0.011(syst.)[1.001,1.057],(ReλCP/|λCP|)Rez=0.014±0.035(stat.)±0.034(syst.)[−0.072,0.101],Imz=0.038±0.029(stat.)±0.025(syst.)[−0.028,0.104].The values inside square brackets indicate the 90% confidence-level intervals. The values of ImλCP and Δm are consistent with previous analyses and are used as cross checks. These measurements are in agreement with standard model expectations.Received 29 February 2004DOI:https://doi.org/10.1103/PhysRevD.70.012007©2004 American Physical Society

Unified graphical summary of neutrino mixing parameters

The neutrino mixing parameters are presented in a number of different ways by the various experiments, e.g. SuperKamiokande, K2K, SNO, KamLAND and Chooz and also by the Particle Data Group. In this paper, we argue that presenting the data in terms of $\sin^2 \theta$, where $\theta$ is the mixing angle appropriate for a given experiment has a direct physical interpretation. For current atmospheric, solar and reactor neutrino experiments, the $\sin^2 \theta$'s are effectively the probability of finding a given flavor in a particular neutrino mass eigenstate. The given flavor and particular mass eigenstate varies from experiment to experiment, however, the use of $\sin^2 \theta$ provides a unified picture of all the data. Using this unified picture we present a graphical way to represent these neutrino mixing parameters which includes the uncertainties. All of this is performed in the context of the present experimental status of three neutrino oscillations.

WAVE PACKETS AND QUANTUM OSCILLATIONS

We give a detailed analysis of the oscillation formula within the context of the wave packet formalism. Particular attention is made to insure flavor eigenstate creation in the physical cases (Δp≠0). This requirement imposes noninstantaneous particle creation in all frames. It is shown that the standard formula is not only exact when the mass wave packets have the same velocity, but it is a good approximation when minimal slippage occurs. For more general situations the oscillation formula contains additional arbitrary parameters, which allows for the unknown form of the wave packet envelope.

Do many-particle neutrino interactions cause a novel coherent effect?

We investigate whether coherent flavor conversion of neutrinos in a neutrino background is substantially modified by many-body effects, with respect to the conventional one-particle effective description. We study the evolution of a system of interacting neutrino plane waves in a box. Using its equivalence to a system of spins, we determine the character of its behavior completely analytically. We find that, if the neutrinos are initially in flavor eigenstates, no coherent flavor conversion is realized, in agreement with the effective one-particle description. This result does not depend on the size of the neutrino wavepackets and therefore has a general character. The validity of the several important applications of the one-particle formalism is thus confirmed.

Possibility of measuring the CP-violation γ-parameter in decays of Ξbc baryons

The model-independent method based on the triangle ideology is implemented to extract the CKM-matrix angle γ in the decays of doubly heavy baryons containing the charmed and beauty quarks. We analyze a color structure of diagrams and conditions for reconstructing two reference-triangles by tagging the flavor and CP eigenstates of D0↔D0 mesons in the fixed exclusive channels. The characteristic branching ratios are evaluated in the framework of a potential model setting a parametric dependence on the hadronic matrix elements for the decay rates.

The wavelength of neutrino and neutral kaon oscillations

Neutral kaons, and probably also neutrinos, exhibit oscillations between flavor eigenstates, as a result of being produced in a superposition of mass eigenstates. Several recent papers have addressed the question of the energies and momenta of the components of these states, and their effect on the coherence of the states and on the wavelength of the oscillations. We point out that the mass eigenstates need have neither equal momentum nor equal energy, but can nevertheless be coherent, and that a correct treatment of the kinematics recovers the usual result for the wavelength of the flavor oscillations.

μ–τ reflection symmetry in lepton mixing and neutrino oscillations

We examine the possibility that the lepton mixing matrix may exhibit a strong form of μ–τ universality, in which corresponding elements of the μ- and τ-neutrino flavour eigenstates have equal moduli, and find that it is consistent with present data on neutrino oscillations. We point out that in the Dirac case, this is equivalent to symmetry under μ–τ reflection, i.e., the combined operation of μ–τ flavour exchange in the MNS matrix with a CP transformation on the whole leptonic sector. We give the most general form for such a mixing matrix, examine the lepton mass matrices under such a symmetry, and explore the observable manifestations of the symmetry in neutrino oscillations.

Study of time-dependentCP-violating asymmetries and flavor oscillations in neutralBdecays at theΥ(4S)

We present a measurement of time-dependent CP-violating asymmetries in neutral B meson decays collected with the BABAR detector at the PEP-II asymmetric-energy e+e− collider at the Stanford Linear Accelerator Center. The data sample consists of 29.7 fb−1 recorded at the Υ(4S) resonance and 3.9 fb−1 off resonance. One of the neutral B mesons, which are produced in pairs at the Υ(4S), is fully reconstructed in the CP decay modes J/ψKS0, ψ(2S)KS0, χc1KS0, J/ψK*0 (K*0→KS0π0) and J/ψKL0, or in flavor-eigenstate modes involving D(*)π/ρ/a1 and J/ψK*0 (K*0→K+π−). The flavor of the other neutral B meson is tagged at the time of its decay, mainly with the charge of identified leptons and kaons. A neural network tagging algorithm is used to recover events without a clear lepton or kaon tag. The proper time elapsed between the decays is determined by measuring the distance between the decay vertices. Wrong-tag probabilities, the time-difference resolution function, and the B0−B0 oscillation frequency Δmd are measured with a sample of about 6350 fully-reconstructed B0 decays in hadronic flavor-eigenstate modes. A maximum-likelihood fit to this flavor eigenstate sample finds Δmd=0.516±0.016(stat)±0.010(syst)ps−1. The value of the asymmetry amplitude sin2β is determined from a simultaneous maximum-likelihood fit to the time-difference distribution of the flavor-eigenstate sample and about 642 tagged B0 decays in the CP-eigenstate modes. We find sin2β=0.59±0.14(stat)±0.05(syst), demonstrating that CP violation exists in the neutral B meson system. We also determine the value of the CP violation parameter |λ|=0.93±0.09(stat)±0.03(syst), which is consistent with the expectation of |λ|=1 for no direct CP violation.Received 10 January 2002DOI:https://doi.org/10.1103/PhysRevD.66.032003©2002 American Physical Society

Improved search for $B_{s}^{0} - \overline{B}_{s}^{0}$ oscillations

An improved search for B s 0 oscillations is performed in the ALEPH data sample collected during the first phase of LEP, and reprocessed in 1998. Three analyses based on complementary event selections are presented. First, decays of B s 0 mesons into hadronic flavour eigenstates are fully reconstructed. This selection yields a small sample of candidates with excellent decay length and momentum resolution and hi gh average B s 0 purity. Semileptonic decays with a reconstructed D s - meson provide a second sample with larger statistics, high average B s 0 purity, but a poorer momentum and decay length resolution due to the partial decay reconstruction. Finally, semileptonic b-hadron decays are inclusively selected and yield the data sample with the highest sensitivity to B s 0 oscillations, as the much higher statistics compensate for the low average B s 0 purity and poorer time resolution. A lower limit is set at $\Delta m_{s} > 10.9$ ps-1 at 95% C.L., significantly lower than the expected limit of 15.2 ps-1.

Solar neutrino results and violation of the equivalence principle: An analysis of the existing data and predictions for SNO

Violation of the Equivalence Principle (VEP) can lead to neutrino oscillation through the non-diagonal coupling of neutrino flavor eigenstates with the gravitational field. The neutrino energy dependence of this oscillation probability is different from that of the usual mass-mixing neutrino oscillations. In this work we explore, in detail, the viability of the VEP hypothesis as a solution to the solar neutrino problem in a two generation scenario with both the active and sterile neutrino alternatives, choosing these states to be massless. To obtain the best-fit values of the oscillation parameters we perform a chi square analysis for the total rates of solar neutrinos seen at the Chlorine (Homestake), Gallium (Gallex and SAGE), Kamiokande, and SuperKamiokande (SK) experiments. We find that the goodness of these fits is never satisfactory. It markedly improves, especially for VEP transformation to sterile neutrinos, if the Chlorine result is excluded from the analysis. The 1117-day SK data for recoil electron spectrum are also examined for signals of VEP oscillations. For these fits, we consider variations of the Standard Solar Model by allowing the absolute normalizations of the 8B and hep neutrinos to vary. Here the fits are quite good but the best fit values of the parameters are rather different from those from the total rates fits. A combined fit to the total rates and recoil electron spectrum data is also performed. We present the 90% confidence limit contours for all the three analyses mentioned above. The best-fit parameters obtained from the recoil electron spectrum and the combined analysis of rate and spectrum are used to predict the charge current and scattering electron spectrum at SNO.

Neutrino oscillations in non-inertial frames and the violation of the equivalence principle Neutrino mixing induced by the equivalence principle violation

Neutrino oscillations are analyzed in an accelerating and rotating reference frame, assuming that the gravitational coupling of neutrinos is flavor dependent, which implies a violation of the equivalence principle. Unlike the usual studies in which a constant gravitational field is considered, such frames could represent a more suitable framework for testing if a breakdown of the equivalence principle occurs, due to the possibility to modulate the (simulated) gravitational field. The violation of the equivalence principle implies, for the case of a maximal gravitational mixing angle, the presence of an off-diagonal term in the mass matrix. The consequences on the evolution of flavor (mass) eigenstates of such a term are analyzed for solar (oscillations in the vacuum) and atmospheric neutrinos. We calculate the flavor oscillation probability in the non-inertial frame, which does depend on its angular velocity and linear acceleration, as well as on the energy of neutrinos, the mass-squared difference between two mass eigenstates, and on the measure of the degree of violation of the equivalence principle ( $\Delta\gamma$ ). In particular, we find that the energy dependence disappears for vanishing mass-squared difference, unlike the result obtained by Gasperini, Halprin, Leung, and other physical mechanisms proposed as a viable explanation of neutrino oscillations. Estimations on the upper values of $\Delta\gamma$ are inferred for a rotating observer (with vanishing linear acceleration) comoving with the earth, hence $\omega \sim 7\cdot 10^{-5}$ rad/sec, and all other alternative mechanisms generating the oscillation phenomena have been neglected. In this case we find that the constraints on $\Delta\gamma$ are given by $\Delta\gamma\leq 10^2$ for solar neutrinos and $\Delta\gamma\leq 10^6$ for atmospheric neutrinos.

Atmospheric neutrino anomaly without maximal mixing?

We consider a pattern of neutrino masses in which there is an approximate mass degeneracy between the two mass eigenstates most coupled to the $\nu_\mu$ and $\nu_\tau$ flavour eigenstates. Earth-matter effects can lift this degeneracy and induce an effectively maximal mixing between these two generations. This occurs if $\nu_e$'s contain comparable admixtures of the degenerate eigenstates, even rather small ones. This provides an explanation of the atmospheric neutrino anomaly in which the {\it ab initio} introduction of a large mixing angle is not required. To test this possibility we perform a novel and detailed analysis of the 52 kiloton-year SuperKamiokande data, and we find that in a large region of parameter space the corresponding confidence levels are excellent. The most recent results from the Chooz reactor experiment, however, severely curtail this region, so that the conventional scenario with nearly maximal mixing angles --which we also analyse in detail-- is supported by the data.

CONSTRAINTS OF MIXING ANGLES FROM LEPTON NUMBER VIOLATING PROCESSES

We discuss the constraints of lepton mixing angles from lepton number violating processes such as neutrinoless double beta decay, μ--e+ conversion and K decay, K-→π+μ-μ- which are allowed only if neutrinos are Majorana particles. The rates of these processes are proportional to the averaged neutrino mass defined by [Formula: see text] in the absence of right-handed weak coupling. Here a, b(j) are flavor(mass) eigenstates and Uaj is the left-handed lepton mixing matrix. We give general conditions imposed on <mν>ab in terms of mi, lepton mixing angles and CP violating phases (three phases in Majorana neutrinos). These conditions are reduced to the constraints among mi, lepton mixing angles and <mν>ab which are irrelevant to the concrete values of CP phases. Given a <mν>ab experimentally, these conditions constrain mi and the lepton mixing angles. Though these constraints are still loose except for neutrinoless double beta decay, they will become helpful through rapid improvements of experiments. By using these constraints we also derive the limits on averaged neutrino masses for μ--e+ conversion and K decay, K-→π+μ-μ-, respectively. We also present the bounds for CP phases in terms of mi, mixing angles and <mν>ab.

Flavor-dependent and basis-independent measures ofRviolation

We construct lepton flavour-dependent and basis-independent measures of R-parity violation in the minimal supersymmetric extension of the Standard Model (MSSM). We work in the context of exact supersymmetry, neglecting the effects of Higgs vacuum expectation values and soft supersymmetry-breaking terms. We devote particular attention to appropriate choices of flavour eigenstates, and to the counting and enumeration of R-violating invariants in two- and three-generation models. We also make an indicative application of our results to derive possible basis-independent cosmological upper bounds on flavour-dependent violation of R parity.

A complete solution to neutrino mixing

Deviations from expectations have been claimed for solar, atmospheric and high energy prompt neutrinos from charm decay. This information, supplemented only by the existing very good upper limits for oscillations of the νμ at accelerator energies, is used as input to a phenomenological three-flavour analysis of neutrino mixing. The solution found is unique and completely determines the mass eigenstates as well as the mixing matrix relating mass and flavour eigenstates. Assuming the mass eigenstates to follow the hierarchy m1 ≪ m2 ≪ m3, their values are found to be m1 ≪ 10−2 eV, m2 = (0. eV, m3 = (19.4 ±0.7) eV. These masses are in agreement with the leptonic quadratic hierarchy of the see-saw model and large enough to render energy-independent any oscillation-induced phenomenon in solar neutrino physics observable on Earth. This possibility is not excluded by the present knowledge of solar neutrino physics. The mixing angles are determined to be θ12 = 0.55 ± 0.08, θ13 = 0.38 ± 0.06, θ23 < 0.03. Small values of θ23 are typical of any solution in which in the cosmological interesting region. The solution found is not in serious contradiction with any of the present limits to the existence of neutrino oscillations. The most relevant implications in particle physics, astrophysics and cosmology are discussed

Correlated Variations in the Solar Neutrino Flux and the Solar Wind and the Relation to the Solar Neutrino Problem

Solar wind parameters from the Massachusetts Institute of Technology (MIT) plasma experiment on the IMP 8 spacecraft overlap ∼19 years of published neutrino flux observations from the Homestake experiment. A strong correlation is found between neutrino flux and solar wind properties, in particular, the solar wind mass flux. The correlation is significantly better than any anticorrelation with sunspot number and is comparable to those previously found with photospheric magnetic flux and shifts in p -mode frequencies. If current notions of solar structure are correct, these observations require new fundamental physics of neutrinos. For a proper choice of neutrino parameters, the level of variations is consistent with resonant conversion of electron neutrinos to a nondetected flavor eigenstate mediated by the magnetic field in the sun's convective zone. The solar wind mass flux may act as a proxy for this field, producing the solar wind-neutrino flux connection.

A three-flavour analysis of neutrino mixing

A comprehensive three-flavour analysis of the existing experimental information on accelerator, atmospheric and solar neutrinos allows to determine the mass eigenstates as well as the complete mixing matrix relating mass and flavour eigenstates. The masses are found to be in agreement with the leptonic quadratic hierarchy of the see-saw model and large enough to render energy-independent any oscillation-induced observable in solar neutrino physics, in agreement with all available data. The solution obtained for the mixing matrix is unique. The most relevant implications are discussed.

Effects of matter oscillations on supernova neutrino flux

Abstract If neutrinos have mass it is likely that, as a result of the effect of matter, neutrino flavor eigenstates are converted to mass eigenstates as they emerge from a supernova. In the case of large neutrino mixing angles there can be a significant increase in the mean energy and detected flux of neutrinos from a supernova.