Q values of the superallowed beta emitters 26Alm, 42Sc, and 46V and their impact on Vud and the unitarity of the Cabibbo-Kobayashi-Maskawa matrix

The beta-decay Q(EC) values of the superallowed beta emitters 26Alm, 42Sc, and 46V have been measured with a Penning trap to a relative precision of better than 8 x 10(-9). Our result for 46V, 7052.72(31) keV, confirms a recent measurement that differed from the previously accepted reaction-based Q(EC) value. However, our results for 26Alm and 42Sc, 4232.83(13) keV and 6426.13(21) keV, are consistent with previous reaction-based values. By eliminating the possibility of a systematic difference between the two techniques, this result demonstrates that no significant shift in the deduced value of Vud should be anticipated.     

First experimental determination of the charge radius of 74Rb and its application in tests of the unitarity of the Cabibbo-Kobayashi-Maskawa matrix

Collinear-laser spectroscopy with the bunched-beams technique was used for the study of neutron deficient Rb isotopes, out to (74)Rb (N = Z = 37) at TRIUMF. The measured hyperfine coupling constants of (76,78m)Rb were in agreement with literature values. The nuclear spin of (75)Rb was confirmed to be I = 3/2, and its hyperfine coupling constants were measured for the first time. The mean-square charge radius of (74)Rb was determined for the first time. This result has improved the isospin symmetry breaking correction term used to calculate the Ft value, with implications for tests of the unitarity of the Cabibbo-Kobayashi-Maskawa matrix.     

The isospin mixing and the superallowed Fermi beta decay

In the present work, the isospin admixtures in the nuclear ground states of the parent nuclei and isospin structure of the isobar analog resonance (IAR) states have been investigated by studying the 0^?+???0^?+? superallowed Fermi ?? decays using Pyatov??s restoration method. Within the random phase approximation (RPA), in this method, the effect of isospin breaking due to the Coulomb forces has been evaluated, taking into account the effect of pairing correlations between nucleons.     

Measurement of the Cabibbo-Kobayashi-Maskawa matrix element V(ub) with B-->rhoenu decays

We present a measurement of the branching fraction for the rare decays B-->rhoenu and extract a value for the magnitude of V(ub), one of the smallest elements of the Cabibbo-Kobayashi-Maskawa quark-mixing matrix. The results are given for five different calculations of form factors used to para-metrize the hadronic current in semileptonic decays. Using a sample of 55 x 10(6) BB meson pairs recorded with the BABAR detector at the PEP-II e(+)e(-) storage ring, we obtain B(B0-->rho(-)e(+)nu)=(3.29+/-0.42+/-0.47+/-0.55) x 10(-4) and |V(ub)|=(3.64+/-0.22+/-0.25(+0.39)(-0.56)) x 10(-3), where the uncertainties are statistical, systematic, and theoretical, respectively.     

Quark mixing and exponential form of the Cabibbo-Kobayashi-Maskawa matrix

Various forms of representation of the mixing matrix are discussed. An exponential parametrization e ^ of the Cabibbo-Kobayashi-Maskawa matrix is considered in the context of the unitarity requirement, this parametrization being the most general form of the mixing matrix. An explicit representation for the exponential mixing matrix in terms of the first and second degrees of the matrix  exclusively is obtained. This representation makes it possible to calculate this exponential mixing matrix readily in any order of the expansion in the small parameter λ. The generation of new unitary parametric representations of the mixing matrix with the aid of the exponential matrix is demonstrated.     

Experimental constraints on the phase in the Cabibbo-Kobayashi-Maskawa matrix

Using experimental results on |V _ub /V _cb |, (K⁰), (B⁰) and two experimental limits onm _t , and assuming that these five observations are fully described by standard physics, we determine values and errors for the two CKM matrix parameters and with a maximum-likelihood fit. The results depend strongly onf _B ; (, ) lies in the first quadrant forf _B >180 MeV and in the second forf _B <180 mev.=" as=" functions=">f _B , we present also values and errors onm _t , ₁₃, |V _td |, arg(V _td ), and M(B _s )/(B _s ).     

Overlapping resonances and unitarity of the scattering matrix

An automatically unitary product expansion for a scattering matrix with arbitrary over-lapping resonances is discussed and used to derive sum rules for the resonance parameters. Problems with the implementation of time-reversal invariance are pointed out.     

Improved calculation of electroweak radiative corrections and the value of Vud

A new method for computing hadronic effects on electroweak radiative corrections to low-energy weak interaction semileptonic processes is described. It employs high order perturbative QCD results originally derived for the Bjorken sum rule along with a large QCD-motivated interpolating function that matches long- and short-distance loop contributions. Applying this approach to the extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element Vud from superallowed nuclear beta decays reduces the theoretical loop uncertainty by about a factor of 2 and gives Vud=0.97377(11)(15)(19). Implications for CKM unitarity are briefly discussed.     

Quantum-mechanical tunnelling and the unitarity of the scattering matrix

The one-dimensional tunnel effect is discussed within the framework of Weyl's theory of differential equations. A two-channel scattering experiment is formulated in terms of Riccati's differential equation, and the fundamental quantities are evaluated by means of Wronskians, logarithmic derivatives and the Weyl-Titchmarsh m-coefficient. No approximations are invoked. It is also demonstrated that the scattering matrix S is characterized by SS* = 1 and is unitary if and only if flux is conserved.     

Determination of the (76)Ge double beta decay Q value

The Q value of the (76)Ge double beta decay has been determined by measuring the masses of (76)Ge and (76)Se in a Penning trap using neon- and fluorinelike ions. The obtained masses are 75.921 402 758(96) u and 75.919 213 795(81) u, respectively. The systematic errors of these two determinations are nearly equal, and therefore, the remaining systematic uncertainty of the Q value is drastically reduced. A Q value of 2 039.006(50) keV was obtained improving the accuracy of the accepted value by a factor of 6.     

Experimental validation of the largest calculated isospin-symmetry-breaking effect in a superallowed Fermi decay

A precision measurement of the γ yields following the β decay of (32)Cl has determined its isobaric-analogue branch to be (22.47(-0.18)(+0.21))%. Since it is an almost pure-Fermi decay, we can also determine the amount of isospin-symmetry breaking in this superallowed transition. We find a very large value, δ(C) = 5.3(9)%, in agreement with a shell-model calculation. This result sets a benchmark for isospin-symmetry-breaking calculations and lends support for similarly calculated, yet smaller, corrections that are currently applied to 0+ → 0 + transitions for tests of the standard model.     

Q EC value and Gamow-Teller strength of the102CdEC/gb+ decay

Within the framework of a systematic study of 0⁺→1⁺ Β-transitions in the¹⁰⁰Sn region, the decay of the neutrondeficient isotope¹⁰²Cd was investigated. This isotope was produced in¹⁶O+⁹²Mo and⁵⁸Ni+⁵⁰Cr heavy-ion reactions and in proton-induced spallation of^natSn, and mass-separated samples were prepared by means of the GSI and the ISOLDE on-line mass separators, respectively. Observations of X-rays,γ-rays, and conversion-electrons studies have led to an improved¹⁰²Cd→¹⁰²Ag decay scheme which includes six 0⁺→1⁺ Gamow-Teller transitions. The half-life of¹⁰²Cd was redetermined with higher accuracy to be 345±8 s. Using a Si(Li)-BGO-Ge spectrometer, theΒ ⁺ endpoint energy of the main decay component was measured, yielding aQ _EC value of 2587±8 keV. This very small uncertainty ofQ _EC, combined with the improved knowledge of half-life and decay scheme, allows an accurate determination of the observed Gamow-Teller decay strengthB _Σ (GT)=1.513±0.055 for¹⁰²Cd. This result is discussed in comparison with predictions from model calculations.     

A determination of the Cabibbo-Kobayashi-Maskawa parameter |V us| using KL decays

We present a determination of the Cabibbo-Kobayashi-Maskawa parameter |V(us)| based on new measurements of the six largest K(L) branching fractions and semileptonic form factors by the KTeV (E832) experiment at Fermilab. We find |V(us)|=0.2252+/-0.0008(KTeV)+/-0.0021(ext), where the errors are from KTeV measurements and from external sources. We also use the measured branching fractions to determine the CP violation parameter |eta(+-)|=(2.228+/-0.005(KTeV)+/-0.009(ext))x10(-3).