Mixing CP Research Articles

Super-Kamiokande — Experimental results and future possibilities of atmospheric neutrino measurements

While neutrino flavor mixing has been established by atmospheric neutrino experiments as well as solar and reactor neutrino experiments, there are still remaining mixing parameters and CP phases to be explored. In this article, sensitivities for measuring these parameters in future atmospheric neutrino experiments are discussed, assuming the same set of systematic uncertainties and the same detector performance as Super-Kamiokande. It was found that there is a possibility of discriminating the octants of θ 23 . Moreover, if θ 13 is close to the current reactor limit, there is a good opportunity for observing nonzero θ 13 and even measuring the CP phase in the lepton sector.

New type of complex neutrino mass texture andμ−τsymmetry

Relying upon the usefulness of the \mu-\tau symmetry, we find a new type of neutrino mass texture with a single phase parameter \delta that describes maximal atmospheric neutrino mixing and Dirac CP violation due to the presence of \delta. The Majorana phase associated with the third massive neutrino turns out to be identical to the Dirac phase while other Majorana phases vanish. The nonvanishing reactor neutrino mixing angle \theta_{13} is induced by a \mu-\tau symmetry breaking effect. Flavor neutrino masses that supply the \mu-\tau symmetry breaking terms become pure imaginary for \delta=\pm \pi/2, leading to maximal CP violation. There is a parameter denoted by \eta, which is either O(\sqrt{\Delta m^2_\odot/\Delta m^2_{atm}}) in the normal mass hierarchy, or O(\Delta m^2_\odot/\Delta m^2_{atm}) in the inverted mass hierarchy. In the inverted mass hierarchy, the contribution of O(\sin^2\theta_{13}) is found to be significant and cannot be neglected. Our texture also leads to quasi degenerate neutrinos with masses of O(\sqrt{\Delta m^2_{atm}}), which serves as the scale for the effective neutrino mass in (\beta\beta)_{0\nu}-decay. This texture does not include \eta, and \Delta m^2_\odot naturally arises from contributions of O(\sin^2\theta_{13}) to give \Delta m^2_\odot/\Delta m^2_{atm}\sim\sin^2\theta_{13}, yielding the prediction of \sin^2\theta_{13}=O(10^{-2}).

Charged lepton corrections to neutrino mixing angles and CP phases revisited

We re-analyze charged lepton corrections to neutrino mixing angles and CP phases, carefully including CP phases from the charged lepton sector. We present simple analytical formulae for including the charged lepton corrections and derive compact new results for small neutrino and charged lepton mixings θ 13 ν and θ 13 e . We find a generic relation θ 12 + 1 2 θ 12 e cos ( δ − π ) ≈ θ 12 ν , which relates the prediction from the neutrino sector θ 12 ν to the charged lepton mixing θ 12 e and to the MNS neutrino oscillation phase δ. We apply our formula to the examples of bimaximal or tri-bimaximal neutrino mixing. One implication is that the so-called quark–lepton complementarity relation θ 12 + θ C = 45 ° can only hold for δ = π and it gets modified in the presence of leptonic CP violation. On the other hand, the lepton mixing θ 13 generated from the charged lepton correction θ 12 e is independent of CP phases and given by θ 13 = 1 2 θ 12 e . Combining these results leads to a model-independent sum rule: θ 12 + θ 13 cos ( δ − π ) ≈ θ 12 ν where θ 12 ν = ( 35.26 ° ) 45 ° in the case of (tri-)bimaximal neutrino mixing, for example.

CPasymmetries and branching ratios ofB→Kπin supersymmetric models

We analyze the supersymmetric contributions to the direct and mixing CP asymmetries and also to the branching ratios of the B --> K \pi decays in a model independent way. We consider both gluino and chargino exchanges and emphasize that a large gluino contribution is essential for saturating the direct and mixing CP asymmetries. We also find that combined contributions from the penguin diagrams with chargino and gluino in the loop could lead to a possible solution for the branching ratios puzzle and account for the results of R_c and R_n within b --> s \gamma constraints. When all relevant constraints are satisfied, our result indicates that supersymmetry favors lower values of R_c. Finally we study the correlations between the mixing CP asymmetry S_{K^0 \pi^0} and mixing CP asymmetries of the processes B --> \phi K and B --> \eta' K. We show that it is quite possible for gluino exchanges to accommodate the results of that observables

Bounds on the neutrino mixing angles andCPphase for anSO(10)model with lopsided mass matrices

The bounds on the neutrino mixing angles and CP Dirac phase for an SO(10) model with lopsided mass matrices, arising from the presence of ${\bf 16}_H$ and $\bar{\bf 16}_H$ Higgs representations, are studied by variation of the one real and three unknown complex input parameters for the right-handed Majorana neutrino mass matrix. The scatter plots obtained favor nearly maximal atmospheric neutrino mixing, while the reactor neutrino mixing lies in the range $10^{-5} \lsim \sin^2 \theta_{13} \lsim 1 \times 10^{-2}$ with values greater than $10^{-3}$ most densely populated. A rather compelling scenario within the model follows, if we restrict the three unknown complex parameters to their imaginary axes and set two of them equal. We then find the scatter plots are reduced to narrow bands, as the mixing angles and CP phase become highly correlated and predictive. The bounds on the mixing angles and phase then become $0.45 \lsim \sin^2 \theta_{23} \lsim 0.55$, $0.38 \lsim \tan^2 \theta_{12} \lsim 0.50$, $0.002 \lsim \sin^2 \theta_{13} \lsim 0.003$, and $60^\circ \lsim \pm \delta_{CP} \lsim 85^\circ$. Moreover, successful leptogenesis and subsequent baryogenesis are also obtained, with $\eta_B$ increasing from $(2.7 to 6.3) \times 10^{-10}$ as $\sin^2 \theta_{23}$ increases from 0.45 to 0.55.

The BTeV trigger—recent developments

BTeV is a collider experiment at the Fermilab Tevatron dedicated to precision measurements of CP violation, mixing and rare decays of beauty and charm hadrons. The detector is a forward spectrometer with a pixel vertex detector inside a dipole magnet. A unique feature of BTeV is the trigger, which reconstructs tracks and vertices in every beam crossing. We present here an overview of the BTeV trigger and a description of recent improvements in trigger timing.

Very Long Baseline Neutrino Oscillation Experiments for Precise Measurements of Mixing Parameters and CP Violating Effects

Recent exciting results have shown that neutrinos oscillate between their weak eigenstates and thus must not only be massive but their mass and flavor eigenstates do no coincide. This has opened a whole new area of experimental physics where one strives to precisely measure the mixing parameters, search for potential CP symmetry violation in the lepton sector and understand secondary effects, such as how the oscillations are affected when the neutrinos pass through matter. It is possible to measure all of the oscillation parameters in a single experiment by employing a 1-MW wide-band neutrino super-beam, a very long baseline of ∼2500 km and a 500-kton massive far detector.

Status of BTeV

BTeV is a forward collider experiment at the Fermilab Tevatron dedicated to precision studies of CP violation, mixing and rare decays of beauty and charm hadrons.

Comparative study of CP asymmetries in supersymmetric models

We systematically analyze the supersymmetric contributions to the mixing CP asymmetries and branching ratios of B → ϕ K S and B → η ′ K S processes. We consider both gluino and chargino exchanges in a model independent way by using the mass insertion approximation method. While we adopt the QCD factorization approach for evaluating the corresponding hadronic matrix elements, a critical comparison with predictions in naive factorization one is also provided. We find that pure chargino contributions cannot accommodate the current experimental results on CP asymmetries, mainly due to b → s γ constraints. We show that charged Higgs contributions can relax these constraints making chargino responsible for large asymmetries. On the other hand, pure gluino exchanges can easily saturate both the constraints on B → ϕ K S and B → η ′ K S CP asymmetries. Moreover, we also find that the simultaneous contributions from gluino and chargino exchanges could easily account for the present experimental results on the mentioned asymmetries. Remarkably, large experimentally allowed enhancements of B → η ′ K S branching ratio can easily be achieved by the contribution of two mass insertions in gluino exchanges. Finally, we analyze the correlations between the CP asymmetries of these processes and the direct CP asymmetry in b → s γ decay. When all experimental constraints are satisfied, supersymmetry favors large and positive values of b → s γ asymmetry.

SUPERSYMMETRIC CONTRIBUTIONS TO THE CP ASYMMETRY OF THE B→ϕKS AND B→η'KS

We analyse the CP asymmetry of the B→ϕKS and B→η'KS processes in general supersymmetric models. We consider both gluino and chargino exchanges in a model-independent way by using the mass insertion approximation method. We adopt the QCD factorization method for evaluating the corresponding hadronic matrix elements. We show that chromomagnetic type of operator may play an important role in accounting for the deviation of the mixing CP asymmetry between B→ϕKS and B→J/ψKS processes observed by Belle and BaBar experiments. We also show that due to the different parity in the final states of these processes, their supersymmetric contributions from the R-sector have an opposite sign, which naturally explain the large deviation between their asymmetries.

Beauty and charm physics at CDF Run II

Using the data samples collected with the CDF Run II detector during the year 2002 and early 2003, new measurements of the production cross-sections and the masses, lifetimes and branching fractions of beauty and charm hadrons are presented. New measurements of the {Lambda}{sub b} mass, lifetime, and branching fractions have greatly improved the current knowledge of bottom baryon properties and decay dynamics. the large charm signals made available by the silicon vertex track trigger have enabled the establishment of key measurements using rare charm decays that are sensitive to new physics beyond the Standard Model. The decay signals B{sub s} {yields} D{sub s}{pi} and the two body charmless decays of B{sup 0} and B{sub s} have been established. These decay channels are important milestones towards the measurement of B{sub s} mixing and direct CP violation in the B system.

Neutrino mixing from the charged lepton sector with sequential right-handed lepton dominance

We systematically analyze the possibility that bi-large lepton mixing originates from the charged lepton sector in models with sequential dominance for the right-handed charged leptons. We derive analytical expressions for the mixing angles and CP phases of the MNS matrix for the case of zero mixing from the neutrino sector, which is arranged for with the help of sequential dominance for the right-handed neutrinos. For small θ13, the two large mixing angles θ12 and θ23 are determined by the Yukawa couplings to the dominant right-handed tau. The mixing angle θ13 is then governed by the subdominant right-handed muon Yukawa couplings. Naturally small θ13 and sequential right-handed lepton dominance can be realized in type I see-saw models and their type II upgrades via spontaneously broken SO(3) flavour symmetry and real vacuum alignment. We discuss the prediction for θ13 in this scenario and corrections to it including the dependence on the neutrino mass scale.

The BTeV experiment

BTeV is an approved forward collider experiment at the Fermilab Tevatron dedicated to precision studies of CP violation, mixing, and rare decays of beauty and charmed hadrons. The BTeV detector has been designed to achieve these goals. Pixel detectors cover the interaction region and vertex computation is included in the lowest level trigger.

Possible supersymmetric solution to the discrepancy between B-->phiK(S) and B-->eta'K(S) CP asymmetries.

We present a possible supersymmetric solution to the discrepancy between the observed mixing CP asymmetries in B-->phiK(S) and B-->eta(')K(S). We show that, due to the different parity in the final states of these processes, their supersymmetric contributions from the R sector have opposite signs, which naturally leads to S(phiK(S)) not equal Seta(')(K(S)). We also consider the proposed mechanisms to solve the puzzle of the observed large branching ratio of B-->eta'K and their impact on Seta(')(K(S)).

Running neutrino masses, mixings and CP phases: analytical results and phenomenological consequences

We derive simple analytical formulae for the renormalization group running of neutrino masses, leptonic mixing angles and CP phases, which allow an easy understanding of the running. Particularly for a small angle θ 13 the expressions become very compact, even when non-vanishing CP phases are present. Using these equations we investigate: (i) the influence of Dirac and Majorana phases on the evolution of all parameters, (ii) the implications of running neutrino parameters for leptogenesis, (iii) changes of the mass bounds from WMAP and neutrinoless double β decay experiments, relevant for high-energy mass models, (iv) the size of radiative corrections to θ 13 and θ 23 and implications for future precision measurements.

The BTeV trigger architecture

BTeV is a high-statistics B-physics experiment that will achieve new levels of sensitivity in testing the Standard Model explanation of CP violation, mixing, and rare decays in the b and c quark systems by operating in the unique environment of a hadron collider. In order to achieve its goals, it will make use of a state-of-the-art Si-pixel vertex detector and a novel three-level hierarchical trigger that will look at every single beam crossing to detect the presence of heavy quark decays. This talk will describe the trigger architecture focusing on key design aspects that allow the use of commercially available technology in a highly feasible and practical solution that meets the demanding physics requirements of the BTeV experiment.

Prediction of | V13| andt he dirac phase in the neutrino mixing matrix

We considered a model where |V_{13}|=0 so that delta=0 at M_R and analyzed mixing angles and CP violation angles at the low energy scale by using the renormalization group in the MSSM model. In this model, parameters at M_R scale are two mixing angles (theta_{12} and theta_{23}), three neutrino masses, and two Majorana phases. We found that (1) sin^2 2 theta_{12} at the low energy scale must be less than that at $M_R$ scale, (2) the induced |V_{13}| can be as large as 0.05 if masses of neutrinos are around 0.05 eV.

CP violation, mixing and lifetime results from BaBar

The BaBar collaboration has analysed 60M B B pairs collected at the υ(4 S) resonance at the PEP II asymetric collider at SLAC. Using this data sample we have measured the CP violation parameters sin(2β) = 0.75 ± 0.09 STAT ± 0.04 SYST and |λ| = 0.92 ± 0.06 STAT ± 0.02 SYST from B 0 → c c → K 0( ∗) + c.c. decays. From charmless 2-body B decays we measure A Kπ = −0.05 ± 0.06 ± 0.01(−0.14, + 0.05), S ππ = −0.01 ± 0.37 ± 0.07(−0.66, + 0.62), C ππ = −0.02 ± 0.29 ± 0.07(−0.54, +0.48). A number of B lifetime and mixing parameters, extracted from subsamples of this data set, are also presented.

Measurements of CP violation, mixing and lifetimes of B mesons with the BaBar detector

We report the observation of CP violation in the B 0 meson system. Using a novel technique for time-dependent measurements, we measure a non-zero value for the CP-violating amplitude sin(2β) at the 4.1σ level. We also report on precision measurements of the B + and B 0 lifetimes and the B 0 B 0 mixing frequency Δm d obtained with the same technique.

Study of theCPproperty of the Higgs boson at a photon collider usingγγ→tt¯→lX

We study the possible effects of CP violation in the Higgs sector on tt - production at a γγ collider. These studies are performed in a model-independent way in terms of six form factors {R(S γ ),I(S γ ),R(P γ ),I(P γ ),S t ,P t } which parametrize the CP mixing in the Higgs sector, and a strategy for their determination is developed. We observe that the angular distribution of the decay lepton from t/t - produced in this process is independent of any CP violation in the tbW vertex and hence best suited for studying CP mixing in the Higgs sector. Analytical expressions are obtained for the angular distribution of leptons in the c.m. frame of the two colliding photons for a general polarization state of the incoming photons. We construct combined asymmetries in the initial state lepton (photon) polarization and the final state lepton charge. They involve CP even (x's) and odd (y's) combinations of the mixing parameters. We study limits up to which the values of x and y, with only two of them allowed to vary at a time, can be probed by measurements of these asymmetries, using circularly polarized photons. We use the numerical values of the asymmetries predicted by various models to discriminate among them. We show that this method can be sensitive to the loop-induced CP violation in the Higgs sector in the minimal supersymmetric standard model.