CP Phase Research Articles

Neutrino oscillations and Leptogenesis

The symmetry breaking of left right symmetric model around few TeV range permits the existence of massive right handed neutrinos or gauge bosons. In this work the decay of lightest right handed neutrinos in a class of minimal left right symmetric model is analysed for the generation of adequate lepton asymmetry. An analytical expression for the lepton asymmetry is developed. In an attempt to achieve the required baryogenesis, we have imposed certain constrains on the parameter space corresponding to low energy neutrino oscillation parameters (especially {\theta} 13 ) and the three phases ( CP, majorana and higher energy phase).

Fermion masses and flavor mixings and strong CP problem

For all the success of the Standard Model (SM), it is on the verge of being surpassed. In this regard we argue, by showing a minimal flavor-structured model based on the non-Abelian discrete SL2(F3) symmetry, that U(1) mixed-gravitational anomaly cancellation could be of central importance in constraining the fermion contents of a new chiral gauge theory. Such anomaly-free condition together with the SM flavor structure demands a condition k1X1/2=k2X2 with Xi being a charge of U(1)Xi and ki being an integer, both of which are flavor dependent. We show that axionic domain-wall condition NDW with the anomaly free-condition depends on both U(1)X charged quark and lepton flavors; the seesaw scale congruent to the scale of Peccei–Quinn symmetry breakdown can be constrained through constraints coming from astrophysics and particle physics. Then the model extended by SL2(F3)×U(1)X symmetry can well be flavor-structured in a unique way that NDW=1 with the U(1)X mixed-gravitational anomaly-free condition demands additional Majorana fermion and the flavor puzzles of SM are well delineated by new expansion parameters expressed in terms of U(1)X charges and U(1)X-[SU(3)C]2 anomaly coefficients. And the model provides remarkable results on neutrino (hierarchical mass spectra and unmeasurable neutrinoless-double-beta decay rate together with the predictions on atmospheric mixing angle and leptonic Dirac CP phase favored by the recent long-baseline neutrino experiments), QCD axion, and flavored-axion.

Improving the prediction of the Atmospheric neutrino flux using the atmospheric muon flux

It is well known that the correlation of atmospheric neutrinos and muons are simply correlated in the energy region of 1–10 GeV, and used for the test bench of the hadronic interaction model used for the calculation of the atmospheric neutrino flux. However, the correlation becomes unclear for neutrinos in the energy range below 1 GeV, which is important for the study of mass ordering of neutrino and CP phase of the neutrino mass. We extend the study of the correlation to the lower neutrino energies and find that the atmospheric muon flux observed at high altitude shows a good correlation to the atmospheric neutrino flux, and could be used to calibrate the hadronic interaction model.

Linear seesaw for Dirac neutrinos with A4 flavour symmetry

We propose a linear seesaw model to realise light Dirac neutrinos within the framework of A4 discrete flavour symmetry. The additional fields and their transformations under the flavour symmetries are chosen in such a way that naturally predicts the hierarchies of different elements of the seesaw mass matrix and also keeps the unwanted terms away. For generic choices of flavon alignments, the model predicts normal hierarchical light neutrino masses with the atmospheric mixing angle in the lower octant. Apart from predicting interesting correlations between different neutrino parameters as well as between neutrino and model parameters, the model also predicts the leptonic Dirac CP phase to lie in a specific range −π/2≲δ≲−π/5 and π/5≲δ≲π/2 that includes the currently preferred maximal value. The predictions for the absolute neutrino masses in one specific version of the model can also saturate the cosmological upper bound on sum of absolute neutrino masses.

Predicting \u03b4PMNS, \u03b823PMNS and fermion mass ratios from flavour GUTs with CSD2

Constrained Sequential neutrino Dominance of type 2 (referred to as CSD2) is an attractive building block for flavour Grand Unified Theories (GUTs) because it predicts a non-zero leptonic mixing angle θ13PMNS, a deviation of θ23PMNS from π/4, as well as a leptonic Dirac CP phase δPMNS which is directly linked to the CP violation relevant for generating the baryon asymmetry via the leptogenesis mechanism. When embedded into GUT flavour models, these predictions are modified in a specific way, depending on which GUT operators are responsible for generating the entries of fermion Yukawa matrices. In this paper, we systematically investigate and classify the resulting predictions from supersymmetric SU(5) based flavour models by fitting the known fermion mass and mixing data, in order to provide a roadmap for future model building. Interestingly, the promising models predict the lepton Dirac CP phase δPMNS between 230° and 290°, and the quark CP phase δCKM in accordance with a right-angled unitarity triangle (αUT = 90°). Also, our model setup predicts the quantities θ23PMNS and md/ms with less uncertainty than current experimental precision, and allowing with future sensitivity to discriminate between them.

Singlet Dirac fermion dark matter with mediators at loop

We study the phenomenology of singlet Dirac fermion dark matter in the simplified models where the dark matter interacts with the Standard Model particles at loop-level with the help of either colored or non-colored mediators. We especially focus on the implications of non-zero CP phases in the dark sector, which induce the electric dipole moments of the Dirac fermion dark matter as well as those of electron and nucleon. It is then found that the dark matter direct detection searches and the measurements of the electric dipole moments are able to test the singlet Dirac fermion dark matter scenario in the forthcoming experiments.

Disentangling Genuine from Matter-Induced CP Violation in Neutrino Oscillations.

We prove that, in any flavor transition, neutrino oscillation CP-violating asymmetries in matter have two disentangled components: (i)a CPT-odd T-invariant term, non-vanishing iff there are interactions with matter, and (ii)a T-odd CPT-invariant term, non-vanishing iff there is genuine CP violation. As function of the baseline, these two terms are distinct L-even and L-odd observables to separately test (i)matter effects sensitive to the neutrino hierarchy and (ii)genuine CP violation in the neutrino sector. For the golden ν_{μ}→ν_{e} channel, the different energy distributions of the two components provide a signature of their separation. At long baselines, they show oscillations in the low and medium energy regions, with zeros at different positions and peculiar behavior around the zeros. We discover a magic energy E=(0.91±0.01) GeV at L=1300 km with vanishing CPT-odd component and maximal genuine CP asymmetry proportional to sinδ, with δ the weak CP phase. For energies above 1.5GeV, the sign of the CP asymmetry discriminates the neutrino hierarchy.

Influence of milk protein concentrates with modified calcium content on enteral dairy beverage formulations: Storage stability

Control of calcium-mediated storage defects, such as age gelation and sedimentation, were evaluated in enteral high-protein dairy beverages during storage. To investigate the effects of reduced-calcium ingredients on storage stability, 2 batches each of milk protein concentrates (MPC) with 3 levels of calcium content were acquired [control, 20% calcium-reduced (MPC-20), and 30% calcium-reduced (MPC-30)]. Control and calcium-reduced MPC were used to formulate 8% (wt/wt) protein enteral dairy beverages. The formulation also consisted of other ingredients, such as gums, maltodextrin, potassium citrate, and sucrose. The pH-adjusted formulation was divided into 2 parts, one with 0.15% sodium hexametaphosphate (SHMP) and the other with 0% SHMP. The formulations were homogenized and retort sterilized at 121°C for 15 min. The retort-sterilized beverages were stored at room temperature for up to 90 d and particle size and apparent viscosity were measured on d 0, 7, 30, 60, and 90. Beverages formulated using control MPC with 0 and 0.15% SHMP exhibited sedimentation, causing a decrease in apparent viscosity by approximately 10 cP and clear phase separation by d 90. The MPC-20 beverages with 0% SHMP exhibited stable particle size and apparent viscosities during storage. In the presence of 0.15% SHMP, particle size increased rapidly by 40 nm on d 90, implying the start of progressive gelation. On the other hand, highest apparent viscosities leading to gelation were observed in MPC-30 beverages at both concentrations of SHMP studied. These results suggested that beverages formulated with MPC-20 and 0% SHMP would have better storage stability by maintaining lower apparent viscosities. Further reduction of calcium using MPC-30 resulted in rapid gelation of beverages during storage.

A grand-unified Nelson\u2013Barr model

We argue that the Nelson–Barr solution to the Strong CP Problem can be naturally realized in an E_6 grand-unified theory. The chiral SM fermions reside in three generations of E_6 fundamentals together with heavy vectorlike down quarks, leptons doublets and right-handed neutrinos. CP is imposed on the Lagrangian and broken only spontaneously at high scales, leading to a mixing between chiral and vectorlike fields that allows to solve the Strong CP Problem through the Nelson–Barr mechanism. The main benefit of the E_6 GUT structure is the predictivity in the SM fermion sector, and a perfect fit to all SM observables can be obtained despite being over-constrained. Definite predictions are made for the neutrino sector, with a Dirac CP phase that is correlated to the CKM phase, allowing to test this model in the near future.

Signatures of the genuine and matter-induced components of the CP violation asymmetry in neutrino oscillations

CP asymmetries for neutrino oscillations in matter can be disentangled into the matter-induced CPT-odd (T-invariant) component and the genuine T-odd (CPT-invariant) component. For their understanding in terms of the relevant ingredients, we develop a new perturbative expansion in both Δm212, |a| ≪ |Δm312| without any assumptions between Δm212 and a, and study the subtleties of the vacuum limit in the two terms of the CP asymmetry, moving from the CPT-invariant vacuum limit a → 0 to the T-invariant limit Δm212 → 0. In the experimental region of terrestrial accelerator neutrinos, we calculate their approximate expressions from which we prove that, at medium baselines, the CPT-odd component is small and nearly δ-independent, so it can be subtracted from the experimental CP asymmetry as a theoretical background, provided the hierarchy is known. At long baselines, on the other hand, we find that (i) a Hierarchy-odd term in the CPT-odd component dominates the CP asymmetry for energies above the first oscillation node, and (ii) the CPT-odd term vanishes, independent of the CP phase δ, at E = 0.92 GeV (L/1300 km) near the second oscillation maximum, where the T-odd term is almost maximal and proportional to sin δ. A measurement of the CP asymmetry in these energy regions would thus provide separate information on (i) the neutrino mass ordering, and (ii) direct evidence of genuine CP violation in the lepton sector.

Leptogenesis via neutrino oscillation magic

The possibility of generating the baryon asymmetry of the Universe via flavor oscillation in the early Universe is discussed. After the inflation, leptons are born in some states, travel in the medium, and are eventually projected onto flavor eigenstates due to the scattering via the Yukawa interactions. By using the Lagrangian of the Standard Model with the Majorana neutrino mass terms, llHH, we follow the time evolution of the density matrices of the leptons in this very first stage of the Universe and show that the CP violation in the flavor oscillation can explain the baryon asymmetry of the Universe. In the scenario where the reheating is caused by the decay of the inflaton into the Higgs bosons, the baryon asymmetry is generated by the CP phases in the Pontecorvo-Maki-Nakagawa-Sakata matrix and thus can be tested by the low energy neutrino experiments.

On the textures of neutrino mass matrix for maximal atmospheric mixing angle and Dirac CP phase

In this paper, we derive in a novel approach the possible textures of neutrino mass matrix that can lead us to maximal atmospheric mixing angle and Dirac CP phase which are consistent with the current neutrino oscillation data. A total of eleven textures are thus found. Interestingly, the specific texture given by the μ-τ reflection symmetry can be reproduced from one of the obtained textures. For these textures, some neutrino mass sum rules which relate the neutrino masses and Majorana CP phases will emerge.

SU(3) \xd7 SO(10) in 6d

We discuss a simple and elegant SU(3) × SO(10) family unified gauge theory in 6d compactified on a torus with the orbifold T2/Z23 and supplemented by a Z6 × Z3 discrete symmetry. The orbifold boundary conditions generate all the desired SU(3) breaking vacuum alignments, including the (0, 1, −1) and (1, 3, −1) alignments of the Littlest Seesaw model for atmospheric and solar neutrino mixing, as well as the usual SO(10) breaking with doublet-triplet splitting. The absence of driving and messenger fields considerably simplifies the field content of the model. It naturally explains why there are three families of quarks and leptons, and accounts for all their masses, mixing angles and CP phases via rather elegant looking Yukawa and Majorana matrices in the theory basis. The resulting model controls proton decay and allows successful Leptogenesis.

Neutrino phenomenology from leptogenesis

Assuming a type-I seesaw mechanism for neutrino mass generation and invoking a baryogenesis via leptogenesis scenario, we consider a reasonable hierarchical structure for Dirac neutrino mass matrix, similar to up-type quark mass matrix. These hypotheses imply a relevant connection between high scale CP violation and low energy one. By requiring a compact heavy neutrino mass spectrum, which allows to circumvent Davidson–Ibarra limit, one can obtain an efficient leptogenesis restricting the allowed region for low energy neutrino parameters. Once the oscillating parameters are taken inside a 3sigma range, through the numerical resolution of the leptogenesis Boltzmann equations one gets the following allowed intervals for the lightest neutrino mass and the Dirac CP phase: -0.90pi<delta <-0.75pi and m_1sim ( 0.002 - 0.004) eV.

Realistic tribimaximal neutrino mixing

We propose a generalized version of the Tri-Bi-Maximal (TBM) ansatz for lepton mixing, leading to non-zero reactor angle $\theta_{13}$ and CP violation. The latter is characterized by two CP phases. The Dirac phase affecting neutrino oscillations is nearly maximal ($\delta_{CP} \sim \pm \pi/2$), while the Majorana phase implies narrow allowed ranges for the neutrinoless double beta decay amplitude. The solar angle $\theta_{12}$ lies nearly at its TBM value, while the atmospheric angle $\theta_{23}$ has the TBM value for maximal $\delta_{CP}$. Neutrino oscillation predictions can be tested in present and upcoming experiments.

Theory of flavors: String compactification

We present a calculating method for the quark and lepton mixing angles. After a general discussion in field theoretic models, we present a working model from a string compactification through $Z_{12-I}$ orbifold compactification. It is beyond presenting just three families of the standard model but is the first example from string compactification successfully fitting to the observed data. Assuming that all Yukawa couplings from string compactification are real, we also comment on a relation between the CP phases in the Jarlskog determinants obtained from the CKM and PMNS matrices. The flipped SU(5) model leads to the doublet-triplet splitting and possible proton decay operators. It is shown that the vacuum expectation values can be tuned such that the proton lifetime is long enough.

Controlled flavor violation in the MSSM from a unified \u0394(27) flavor symmetry

We study the phenomenology of a unified supersymmetric theory with a flavor symmetry Δ(27). The model accommodates quark and lepton masses, mixing angles and CP phases. In this model, the Dirac and Majorana mass matrices have a unified texture zero structure in the (1, 1) entry that leads to the Gatto-Sartori-Tonin relation between the Cabibbo angle and ratios of the masses in the quark sectors, and to a natural departure from zero of the θ13ℓ angle in the lepton sector. We derive the flavor structures of the trilinears and soft mass matrices, and show their general non-universality. This causes large flavor violating effects. As a consequence, the parameter space for this model is constrained, allowing it to be (dis)proven by flavor violation searches in the next decade. Although the results are model specific, we compare them to previous studies to show similar flavor effects (and associated constraints) are expected in general in supersymmetric flavor models, and may be used to distinguish them.

Leptonic CP violation and proton decay in SUSY SO(10)

We study the correlation between proton lifetime and leptonic CP violation in a class of renormalizable supersymmetric SO(10) grand unified theories (GUTs) with 10, 126 and 120 Higgs fields, which provides a unified description of all fermion masses and a possible resolution for the strong CP problem. This specific model is unique in that it can so far be compatible with current proton lifetime limits for a supersymmetry (SUSY) breaking scale as low as 5 TeV due to the presence of a specific Yukawa texture. Our investigation reveals that a discovery of leptonic CP violation in neutrino oscillations would lead to substantial reduction of the parameter space of the model and the potential ruling out of type-II dominance in the neutrino mass seesaw. Furthermore, the previously predicted proton partial lifetimes are sufficiently long for only certain values of the leptonic CP phase.

Mu-tau reflection symmetry with a high scale texture-zero

The μτ -reflection symmetric neutrino mass matrix can accommodate all known neutrino mixing angles, with maximal atmospheric angle fixed, and predicts all the unknown CP phases of the lepton sector but is unable to predict the absolute neutrino mass scale. Here we present a highly predictive scenario where μτ -reflection is combined with a discrete abelian symmetry to enforce a texture-zero in the mass matrix of the heavy right-handed neutrinos that generate the light neutrino masses. Such a restriction reduces the free parameters of the low energy theory to zero and the absolute neutrino mass scale is restricted to few discrete regions, three in the few meV range and one extending up to around 30 meV. The heavy neutrino sector is dependent only on two free parameters which are further restricted to small regions from the requirement of successful leptogenesis. Mass degenerate heavy neutrinos are possible in one case but there is no resonant enhancement of the CP asymmetry.

Exploring NSI degeneracies in long-baseline experiments

One of the main purposes of long-baseline neutrino experiments is to unambiguously measure the CP violating phase in the neutrino sector within the three neutrino oscillation picture. In the presence of physics beyond the Standard Model, the determination of the CP phase will be more difficult, due to the already known degeneracy problem. Working in the framework of non-standard interactions (NSI), we compute the appearance probabilities in an exact analytical formulation and analyze the region of parameters where the confusion problem is present. We also discuss some cases where the falsification of the NSI parameters can be done in long-baseline experiments.