First Lattice Calculation of the Electromagnetic Operator Amplitude <pi0|Q+|K0>

We present the first lattice calculation of the matrix element of the electromagnetic operator , where Q+ = (Q_d e/16 pi^2)* (\bar s_L sigma{mu,nu} F{mu,nu} d_R + \bar s_R sigma{mu,nu} F{mu,nu} d_L). This matrix element plays an important role, since it contributes to enhance the CP violating part of the K_L -> pi0 e+ e- amplitude in supersymmetric extensions of the Standard Model.Comment: 12 pages, 3 figure

Effective Hamiltonian Approach to Hyperon Beta Decay with Final-State Baryon Polarization

Using an effective Hamiltonian approach, we obtain expressions for hyperon beta decay final-state baryon polarization. Terms through second order in the energy release are retained. The resulting approximate expressions are much simpler and more compact than the exact expressions, and they agree closely with them.Comment: 1 Figure Will appear in Phys Rev D 60 Article 117505 (Dec 1, 1999

Rare K decays in a model of quark and lepton masses

An extension of a model of neutrino masses to the quark sector provides an interesting link between these two sectors. A parameter which is important to describe neutrino oscillations and masses is found to be a crucial one appearing in various ``penguin'' operators, in particular the so-called Z penguin. This parameter is severely constrained by the rare decay process $K_{L} \to \mu^{+} \mu^{-}$. This in turn has interesting implications on the decay rates of other rare processes such as $K_{L} \to \mu e$, etc..., as well as on the masses of the neutrinos and the masses of the vector-like quarks and leptons which appear in our model.Comment: 34 pages, 10 figures, corrected some typos in the introductio

Binary systems of neutral mesons in Quantum Field Theory

Quasi-degenerate binary systems of neutral mesons of the kaon type are investigated in Quantum Field Theory (QFT). General constraints cast by analyticity and discrete symmetries P, C, CP, TCP on the propagator (and on its spectral function) are deduced. Its poles are the physical masses; this unambiguously defines the propagating eigenstates. It is diagonalized and its spectrum thoroughly investigated. The role of ``spurious'' states, of zero norm at the poles, is emphasized, in particular for unitarity and for the realization of TCP symmetry. The K_L-K_S mass splitting triggers a tiny difference between their CP violating parameters \epsilon_L and \epsilon_S, without any violation of TCP. A constant mass matrix like used in Quantum Mechanics (QM) can only be introduced in a linear approximation to the inverse propagator, which respects its analyticity and positivity properties; it is however unable to faithfully describe all features of neutral mesons as we determine them in QFT, nor to provide any sensible parameterization of eventual effects of TCP violation. The suitable way to diagonalize the propagator makes use of a bi-orthogonal basis; it is inequivalent to a bi-unitary transformation (unless the propagator is normal, which cannot occur here). Problems linked with the existence of different ``in'' and ``out'' eigenstates are smoothed out. We study phenomenological consequences of the differences between the QFT and QM treatments. The non-vanishing of semi-leptonic asymmetry \delta_S - \delta_L does not signal, unlike usually claimed, TCP violation, while A_TCP keeps vanishing when TCP is realized. We provide expressions invariant by the rephasing of K0 and K0bar.Comment: 44 pages, 2 figures. Version to appear in Int. J. Mod. Phys.

Direct CP, T and/or CPT violations in the K^0-\bar{K^0} system - Implications of the recent KTeV results on 2π2\pi decays -

The recent results on the CP violating parameters Re(e'/e) and \Delta\phi = \phi_{00}-\phi_{+-} reported by the KTeV Collaboration are analyzed with a view to constrain CP, T and CPT violations in a decay process. Combining with some relevant data compiled by the Particle Data Group, we find Re(e_2-e_0) = (0.85 +- 3.11)*10^{-4} and Im(e_2-e_0) = (3.2 +- 0.7)*10^{-4}, where Re(e_I) and Im(e_I) represent respectively CP/CPT and CP/T violations in decay of K^0 and \bar{K^0} into a 2\pi state with isospin I.Comment: 7 pages, No figure

Tests of the Standard Model Using Muon Polarization Asymmetries in Kaon Decays

We have examined the physics and the experimental feasibility of studying various kaon decay processes in which the polarization of a muon in the final state is measured. Valuable information on CP violation, the quark mixing (CKM) matrix, and new physics can be obtained from such measurements. We have considered muon polarization in K_L to mu+ mu- and K to pi mu+ mu- decays. Although the effects are small, or difficult to measure because of the small branching ratios involved, these studies could provide clean measurements of the CKM parameters. The experimental difficulty appears comparable to the observation of K to pi nu barnu. New sources of physics, involving non-standard CP violation, could produce effects observable in these measurements. Limits from new results on the neutron and electron electric dipole moment, and epsilon-prime over epsilon in neutral kaon decays, do not eliminate certain models that could contribute to the signal. A detailed examination of muon polarization out of the decay plane in KMU3 and radiative KMU2 decays also appears to be of interest. With current kaon beams and detector techniques, it is possible to measure the T-violating polarization for KMU3 with uncertainties approaching 0.0001. This level of sensitivity would provide an interesting probe of new physics.Comment: 24 pages, 3 figures, To be published in the International Journal of Modern Physics

Perturbative Matching of the staggered four-fermion operators for e'/e

Using staggered fermions, we calculate the perturbative corrections to the bilinear and four-fermion operators that are used in the numerical study of weak matrix elements for $\epsilon'/\epsilon$. We present results for one-loop matching coefficients between continuum operators, calculated in the Naive Dimensional Regularization (NDR) scheme, and gauge invariant staggered fermion operators. These results, combined with existing results for penguin diagrams, provide the complete one-loop renormalization of the staggered four-fermion operators.Comment: 36 pages. will appear in physical review

Aspects of radiative K^+_e3 decays

We re-investigate the radiative charged kaon decay K+- --> pi0 e+- nu_e gamma in chiral perturbation theory, merging the chiral expansion with Low's theorem. We thoroughly analyze the precision of the predicted branching ratio relative to the non-radiative decay channel. Structure dependent terms and their impact on differential decay distributions are investigated in detail, and the possibility to see effects of the chiral anomaly in this decay channel is emphasized.Comment: 15 pages, 6 figure

Measurements of Direct CP Violation, CPT Symmetry, and Other Parameters in the Neutral Kaon System

We present a series of measurements based on K -> pi+pi- and K -> pi0pi0 decays collected in 1996-1997 by the KTeV experiment (E832) at Fermilab. We compare these four K -> pipi decay rates to measure the direct CP violation parameter Re(e'/e) = (20.7 +- 2.8) x 10^-4. We also test CPT symmetry by measuring the relative phase between the CP violating and CP conserving decay amplitudes for K->pi+pi- (phi+-) and for K -> pi0pi0 (phi00). We find the difference between the relative phases to be Delta-phi = phi00 - phi+- = (+0.39 +- 0.50) degrees and the deviation of phi+- from the superweak phase to be phi+- - phi_SW =(+0.61 +- 1.19) degrees; both results are consistent with CPT symmetry. In addition, we present new measurements of the KL-KS mass difference and KS lifetime: Delta-m = (5261 +- 15) x 10^6 hbar/s and tauS = (89.65 +- 0.07) x 10^-12 s.Comment: Submitted to Phys. Rev. D, August 6, 2002; 37 pages, 32 figure

Vector-meson contributions do not explain the rate and spectrum in K_L -> pi0 gamma gamma

We analyze the recent NA48 data for the reaction K_L -> pi0 gamma gamma with and without the assumption of vector meson dominance (VMD). We find that the data is well described by a three-parameter expression inspired by O(p^6) chiral perturbation theory. We also find that it is impossible to fit the shape of the decay distribution and the overall rate simultaneously if one imposes the VMD constraints on the three parameters. We comment on the different fits and their implications for the CP-conserving component of the decay K_L -> pi0 e+ e-.Comment: Version accepted for publication on Phys. Rev. D. 19 pages, LaTeX, 8 figures, uses epsf.st