Flavor Mixing Scheme Research Articles

The Curious Early History of the Cabibbo–Kobayashi–Maskawa Matrix: Miracles Happen!

Abstract The 1973 Kobayashi–Maskawa paper proposed a compelling link between Cabibbo’s flavor mixing scheme and ${\mathcal {C}}$${\mathcal {P}}$ violation but, since it required the existence of six quarks at a time when the physics community was happy with only three, it received zero attention. However, two years after the paper appeared—at which time it had received a grand total of two citations—the charmed quark was discovered and it finally got some notice and acceptance. After this stumbling start, it subsequently emerged as the focal point of an enormous amount of experimental and theoretical research activity. In an invited talk at a KEK symposium to celebrate the 50th anniversary of the KM paper, I reviewed some of the less well known circumstances that occurred in the years preceding and following the paper’s appearance. Some spoilers: (i) Kobayashi and Maskawa (and a number of other Japanese physicists) were convinced about the existence of the charmed quark nearly three years before its “discovery” at Brookhaven and SLAC. (ii) The matrix provided in their seminal 1973 paper was mathematically incorrect. Another version that was in common use for the following 12 years was technically correct, but not really a rotation matrix. (iii) The CKM matrix ${\mathcal {C}}$${\mathcal {P}}$ phase was only measurable because of the very specific hierarchy of the flavor mixing angles and meson masses. (iv) Similarly, the neutrino mixing discovery, and the PMNS matrix measurability were only possible because of favorable values of the neutrino mass differences and mixing angles. In addition I include some speculations about what may be in store for the future.

Impact of CP violation searches at MOMENT experiment with sterile neutrino

We examine the scope of the MOMENT experiment in the context of CP violation searches with the presence of extra eV scale sterile neutrino. MOMENT is a proposed medium baseline neutrino oscillation experiment using muon beams for neutrinos production, making it advantageous over π0 background and other technical difficulties. We work over the first oscillation maxima which matches the peak value of flux with a run time of 5 years for both neutrino and anti-neutrino modes. We perform the bi-probability studies for both 3 and 3+1 flavor mixing schemes. The CP violation sensitivities arising from the fundamental CP phase δ13 and unknown CP phase δ14 are explored at the firm footing. Slight deteriorations are observed in CP violations induced by δ13 as the presence of sterile neutrino is considered. We also look at the reconstruction of CP violations phases δ13 and δ14 and the MOMENT experiment shows significant capabilities in the precise measurement of δ13 phase.

Asymmetric tri-bi-maximal mixing and residual symmetries

Asymmetric tri-bi-maximal mixing is a recently proposed, grand unified theory (GUT) based, flavor mixing scheme. In it, the charged lepton mixing is fixed by the GUT connection to down-type quarks and a [Formula: see text] flavor symmetry, while neutrino mixing is assumed to be tri-bi-maximal (TBM) with one additional free phase. Here we show that this additional free phase can be fixed by the residual flavor and CP symmetries of the effective neutrino mass matrix. We discuss how those residual symmetries can be unified with [Formula: see text] and identify the smallest possible unified flavor symmetries, namely [Formula: see text] and [Formula: see text]. Sharp predictions are obtained for lepton mixing angles, CP violating phases and neutrinoless double beta decay.

Analysis of the Results of the Neutrino-4 Experiment on the Search for the Sterile Neutrino and Comparison with Results of Other Experiments

We present new results of measurements of reactor antineutrino flux and spectrum dependence on the distance in the range 6-12 meters from the center of the reactor core at SM-3 reactor (Dimitrovgrad, Russia). Additional measurements were carried out and set of data to perform statistical analysis was almost doubled since the previous report. Using all collected data we performed the model independent analysis on the oscillation parameters $\Delta m^2_{14}$ and $\sin^2(2\theta_{14})$. The method of coherent summation of results of measurements allows us to directly observe the effect of oscillations. We observed an oscillation effect in vicinity of $\Delta m^2_{14} = (7.25\pm0.13_{st}\pm1.08_{sys}) \text{eV}^2$ and $\sin^2(2\theta_{14}) =0.26\pm0.08_{st}\pm 0.05_{sys}$. We provide a comparison of our results with results of other experiments on search for sterile neutrino. Combining the result of the Neutrino-4 and the results of measurements of the gallium anomaly and reactor anomaly we obtained value $\sin^2(2\theta_{14})\approx 0.19\pm0.04(4.6\sigma)$. Also was performed comparison of Neutrino-4 experimental results with results of other reactor experiments NEOS, DANSS, STEREO, PROSPECT and accelerator experiments MiniBooNE, LSND and the IceCube experiment also. Sterile neutrino mass which can be calculated using the Neutrino-4 data in assumption that $m^2_4 \approx \Delta m^2_{14}$ is $m_4 = (2.68 \pm 0.13)\text{eV}$. Considering estimations of mixing angles obtained in other experiments we can calculate masses of electron neutrino, muon neutrino and tau neutrino: $m^{\text{eff}}_{\nu_e} = (0.58 \pm 0.09)\text{eV}, m^{\text{eff}}_{\nu_{\mu}} = (0.42 \pm 0.24)\text{eV}, m^{\text{eff}}_{\nu_{\tau}} \leq 0.65\text{eV}$. Extended PMNS matrix for (3 + 1) model with one sterile neutrino is provided, neutrino flavor mixing scheme with sterile neutrino and global fit of reactor experiments.

Revisiting constraints on 3 + 1 active-sterile neutrino mixing using IceCube data

Recent IceCube search results for sterile neutrino increased tension between the combined appearance and disappearance experiments. On the other hand, MiniBooNE latest data confirms at 4.9σ CL the short-baseline oscillation anomaly. We analyze published IceCube data based on two different active-sterile mixing schemes using one additional sterile neutrino flavor. We present exclusion regions in the parameter ranges 0.01 ≤ sin2θ24 ≤ 0.1 and 0.1 eV2 ≤ Δm422 ≤ 10 eV2 for the mass-mixing and flavor-mixing schemes. Under the more conservative mass-mixing scheme, 3σ CL allowed regions for the appearance experiment and MiniBooNE latest result are excluded at ≳ 3σ CL. In case of less-restrictive flavor-mixing scheme, results from the appearance experiments are excluded at ≳ 2σ CL. We also find that including prompt component of the atmospheric neutrino flux relaxes constraints on sterile mixing for Δm422 ≳ 1 eV2.

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., 3H) and EC-decaying (e.g., 163Ho) 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+Ns) 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.

Neutrino magnetic moment,CPviolation, and flavor oscillations in matter

We consider collective oscillations of neutrinos, which are emergent nonlinear flavor evolution phenomena instigated by neutrino-neutrino interactions in astrophysical environments with sufficiently high neutrino densities. We investigate the symmetries of the problem in the full three flavor mixing scheme and in the exact many-body formulation by including the effects of CP violation and neutrino magnetic moment. We show that, similar to the two flavor scheme, several dynamical symmetries exist for three flavors in the single-angle approximation if the net electron background in the environment and the effects of the neutrino magnetic moment are negligible. Moreover, we show that these dynamical symmetries are present even when the CP symmetry is violated in neutrino oscillations. We explicitly write down the constants of motion through which these dynamical symmetries manifest themselves in terms of the generators of the SU(3) flavor transformations. We also show that the effects due to the CP-violating Dirac phase factor out of the many-body evolution operator and evolve independently of nonlinear flavor transformations if neutrino electromagnetic interactions are ignored. In the presence of a strong magnetic field, CP-violating effects can still be considered independently provided that an effective definition for neutrino magnetic moment is used.

Direct detection of hot dark matter including light sterile neutrinos

Both active and sterile sub-eV neutrinos can serve for hot dark matter (DM) in the Universe. We consider the beta-decaying (e.g., 3H) and EC-decaying (e.g., 163Ho) nuclei as the most promising targets to capture hot DM 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 different flavor mixing schemes. We stress that such direct measurements of hot DM might not be hopeless in the long term.

Neutrinos as Hot or Warm Dark Matter

Both active and sterile sub-eV neutrinos can serve for hot dark matter (DM). On the other hand, keV sterile neutrinos could be a good candidate for warm DM. The beta-decaying (e.g., H-3 and Ru-106) and EC-decaying (e.g., Ho-163) nuclei are considered as the most promising targets to capture those extremely low energy neutrinos and antineutrinos, respectively. We calculate the capture rates of relic electron neutrinos and antineutrinos against the corresponding beta-decay or EC-decay backgrounds in different flavor mixing schemes. We stress that such direct laboratory measurements of hot or warm DM might not be hopeless in the long term.

Vector mesonω−ϕmixing and their form factors in the light-cone quark model

The vector meson $\omega$-$\phi$ mixing is studied in two alternative scenarios with different numbers of mixing angles, i.e., the one-mixing-angle scenario and the two-mixing-angle scenario, in both the octect-singlet mixing scheme and the quark flavor mixing scheme. Concerning the reproduction of experimental data and the $Q^2$ behavior of transition form factors, one-mixing-angle scenario in the quark flavor scheme performs better than that in the octet-singlet scheme, while the two-mixing-angle scenario works well for both mixing schemes. The difference between the two mixing angles in the octet-singlet scheme is bigger than that in the quark flavor scheme.

B-->sZ0, b-->s gamma, and b-->sg supersymmetry-induced couplings.

All the possible supersymmetric flavor-changing couplings are considered in a simplified flavor-mixing scheme. We compute the ${d}_{j}\ensuremath{\rightarrow}{d}_{i}{Z}^{0}$, ${d}_{j}\ensuremath{\rightarrow}{d}_{i}\ensuremath{\gamma}$, and ${d}_{j}\ensuremath{\rightarrow}{d}_{i}g$ supersymmetry-induced couplings mediated by (i) a charged Higgs boson, (ii) charginos, (iii) neutrinos, and (iv) gluinos. We give the general expression of the coupling, computed to second order in external momenta, which is applicable to any one vertex induced by a scalar-fermion pair as virtual particles.

μ+polarization in proton decay: A probe of flavor mixing in unified models

Measurements of ..mu../sup +/ polarizations from proton decay will give valuable insight into the nature of unification theories. We discuss the ..mu../sup +/ polarizations expected in a class of O(10) models for two plausible flavor-mixing schemes.