Modern Physics Letters A

We present results on semileptonic B-decays obtained with the BABAR detector. The large data set accumulated at the PEP-II asymmetric-energy B-factory allows a new measurement technique, where the hadronic decay of one B-meson is fully reconstructed and the semileptonic decay of the recoiling B-meson is studied. Traditional analysis techniques of inclusive and exclusive B-decays complement this approach with very high statistics data samples. These measurements play an important role in the tests of the description of CP violation in the Standard Model: The determinations of the Cabibbo-Kobayashi-Maskawa matrix elements |V_cb| and |V_ub| provide constraints on the unitarity of the CKM triangle. Furthermore, the experimental measurement of parameters of Heavy Quark Effective Theory test the consistency of the theoretical description of semileptonic B-decays.

The standard model of leptons is extended to accommodate a discrete Z₃×Z₂ family symmetry. After rotating the charged-lepton mass matrix to its diagonal form, the neutrino mass matrix reveals itself as very suitable for explaining atmospheric and solar neutrino oscillation data. A generic requirement of this approach is the appearance of three Higgs doublets at the electroweak scale, with observable flavor violating decays.

In this paper we analyse the possibility of constructing singularity-free inhomogeneous cosmological models with a pure radiation field as matter content. It is shown that the conditions for regularity are very easy to implement and therefore there is a huge number of such spacetimes.

We examine the compatibility in predicted masses and the decay constants of mesons in terms of two-quark contents. We find that the results of a specific model, which is governed by heavy quark limit, will encounter a challenge to fit both spectra and decay constants simultaneously.

In a recent paper we presented a calculation of NNLL virtual corrections to the forward–backward asymmetries in b→X_sℓ⁺ℓ^- decay. That result does not include bremsstrahlung corrections which are free from infrared and collinear singularities. In the present paper we include the remaining bremsstrahlung corrections to the forward–backward asymmetries in b→X_sℓ⁺ℓ^- decay. The numerical effect of the calculated contributions is found to be below 1%.

Using the associated Jacobi differential equation, we obtain exactly bound states of the generalization of Woods–Saxon potential with the negative energy levels based on the analytic approach. According to the supersymmetry approaches in quantum mechanics, we show that these bound states by four pairs of the first-order differential operators, represent four types of the laddering equations. Two types of these supersymmetry structures, suggest the derivation of algebraic solutions by two different approaches for the bound states.

We discuss the modified gravity which may produce the current cosmic acceleration of the universe and eliminate the need for dark energy. It is shown that such models where the action quickly grows with the decrease of the curvature define the FRW universe with the minimal curvature. Infinite time is required to reach the minimal curvature during the universe evolution. It is demonstrated that quantum effects of conformal fields may strongly suppress the instabilities discovered in modified gravity. We also briefly speculate on the modification of gravity combined with the presence of the cosmological constant dark energy.

Variable speed of light (VSL) theories may lead to large violations of charge conservation that can be written in terms of a dimensionless parameter λ. Similarly, charge non-conservation can arise in theories that break down Einstein's Equivalence Principle, parametrized in terms of Γ₀. It is shown that for such theories, the motion of the Earth with respect to the Sun would produce a seasonal variation for the SAGE and GALLEX–GNO experiments. Analyzing the reported counting rates for these experiments, a very stringent bound |λ|≤2×10^-19 is obtained, some 10⁹ times smaller than previous ones. For the second example, the corresponding bound is |Γ₀|<10^-18, which represents an improvement of 10⁷ on the previous result. Furthermore, assuming that the previous conditions apply, the existing bound for the lifetime of the ⁷¹Ga→⁷¹Ge charge-nonconserving decay is improved as: τ_CNC≥1.4×10²⁷ years. Similarly a new upper limit for the ratio of the charge-nonconserving to the normal weak decay of the neutron is obtained: .