A search for periodic modulations of the solar neutrino flux was performed using the Super-Kamiokande-I data taken from 31 May 1996 to 15 July 2001. The detector’s capability of measuring the exact time of events, combined with a relatively high yield of solar neutrino events, allows a search for short-time variations in the observed flux. We employed the Lomb test to look for periodic modulations of the observed solar neutrino flux. The obtained periodogram is consistent with statistical fluctuation and no significant periodicity was found.

We study type IIB supergravity solutions with four supersymmetries that interpolate between two types widely considered in the literature: the dual of the Becker-Becker compactifications of M theory to three dimensions and the dual of Strominger’s torsion compactifications of heterotic theory to four dimensions. We find that for all intermediate solutions the internal manifold is not Calabi-Yau type, but has an $\mathrm{SU}\left(3\right)\mathrm{}$ holonomy in connection with a torsion given by the 3-form flux. All 3-form and 5-form fluxes, as well as the dilaton, depend on one function appearing in the supersymmetry spinor, which satisfies a nonlinear differential equation. We check that the fields corresponding to a flat bound state of D3- and D5-branes lie in our class of solutions. The relations among supergravity fields that we derive should be useful in studying new gravity duals of gauge theories, as well as possibly compactifications.

We study a formulation and probabilistic interpretation of a simple general-relativistic Hamiltonian quantum system. The system has no unitary evolution in background time. The quantum theory yields transition probabilities between measurable quantities (partial observables). These converge to the classical predictions in the $\overrightarrow{ħ}0$ limit. Our main tool is the kernel of the projector on the solutions of the Wheeler–deWitt equation, which we analyze in detail. It is a real quantity, which can be seen as a propagator that propagates “forward” as well as “backward” in a local parameter time. Individual quantum states, on the other hand, may contain only “forward propagating” components. The analysis sheds some light on the interpretation of background-independent transition amplitudes in quantum gravity.

In this paper we study thick-shell braneworld models in the presence of a Gauss-Bonnet term. We discuss the peculiarities of the attainment of the thin-shell limit in this case and compare them with the same situation in Einstein gravity. We describe the two simplest families of thick-brane models (parametrized by the shell thickness) one can think of. In the thin-shell limit, one family is characterized by the constancy of its internal density profile (a simple structure for the matter sector) and the other by the constancy of its internal curvature scalar (a simple structure for the geometric sector). We find that these two families are actually equivalent in Einstein gravity and that the presence of the Gauss-Bonnet term breaks this equivalence. In the second case, a shell will always keep some nontrivial internal structure, either on the matter or on the geometric sector, even in the thin-shell limit.

The Noether-charge and the Hamiltonian realizations for the $\mathrm{diff}\left(\mathcal{M}\right)$ algebra in diffeomorphism-invariant gravitational theories without a cosmological constant in any dimension are studied in a covariant formalism. We analyze how the Hamiltonian functionals form the $\mathrm{diff}\left(\mathcal{M}\right)$ algebra under the Poisson brackets and show how the Noether charges with respect to the diffeomorphism generated by the vector fields and their variations in n-dimensional general relativity form this algebra. The asymptotic behaviors of vector fields generating diffeomorphism of the manifold with boundaries are discussed. It is shown that the “central extension” for a large class of vector fields is always zero on the Killing horizon. We also check whether choosing the vector fields near the horizon may pick up the Virasoro algebra. The conclusion is unfortunately negative in any dimension.

Recently an alternative description of 2D supergravities in terms of graded Poisson-sigma models (GPSM) has been given. As pointed out previously by the present authors a certain subset of GPSMs can be interpreted as “genuine” supergravity, satisfying the well-known limits of supergravity, albeit deformed by the dilaton field. In our present paper we show that precisely that class of GPSMs corresponds one-to-one to the known dilaton supergravity superfield theories presented a long time ago by Park and Strominger. Therefore, the unique advantages of the GPSM approach can be exploited for the latter: We are able to provide the first complete classical solution for any such theory. On the other hand, the straightforward superfield formulation of the point particle in a supergravity background can be translated back into the GPSM frame, where “supergeodesics” can be discussed in terms of a minimal set of supergravity field degrees of freedom. Further possible applications such as the (almost) trivial quantization are mentioned.

We study the impact of a generalized Chaplygin gas as a candidate for dark energy on density perturbations and on cosmic microwave background (CMB) anisotropies. The generalized Chaplygin gas is a fluid component with an exotic equation of state $p=-A/{\rho }^{\alpha }$ (a polytropic gas with negative constant and exponent). Such a component interpolates in time between dust and a cosmological constant, with an intermediate behavior as ${p=A}^{1/(1+\alpha )}+\alpha \rho .$ Perturbations of this fluid are stable on small scales but behave in a very different way with respect to standard quintessence. Moreover, a generalized Chaplygin gas could also represent an archetypal example of the phenomenological unified models of dark energy and dark matter. The results presented here show how CMB anisotropies and density perturbations in this class of models differ from those of a cold dark matter model with a cosmological constant.

The generalized dynamics describing the propagation of neutral kaons in randomly fluctuating media is derived and analyzed. It takes into account possible matter-induced effects leading to loss of phase coherence and dissipation. The study of selected neutral kaon observables indicates that these nonstandard effects are amenable to a direct experimental analysis.

We calculate the decay couplings and first two Gegenbauer moments of the leading twist light-cone distribution amplitudes of K and $K^{*}$ from QCD sum rules, including NLO perturbative effects.

Hadronic B decays containing an even-parity charmed meson in the final state are studied. Specifically we focus on the Cabibbo-allowed decays $\overline{B}\to D^{**}\pi \left(\rho \right),D^{**}{D}_s^{\left(*\right)},$ $D_s^{**}{D}^{\left(*\right)}$ and $B_s\to D_s^{**}\pi \left(\rho \right),$ where $D^{**}$ denotes generically a p-wave charmed meson. The $\overrightarrow{B}{D}^{**}$ transition form factors are studied in the improved version of the Isgur-Scora-Grinstein-Wise quark model. We apply heavy quark effective theory and chiral symmetry to study the strong decays of p-wave charmed mesons and determine the magnitude of the $D_1^{1/2}-D_1^{3/2}$ mixing angle (the superscript standing for the total angular momentum of the light quark). Except for the decay to $D_1{\mathrm{}\left(2427\right)\mathrm{}}^0{\pi }^{-}$ the predictions of $\mathcal{B}{(B}^{-}\to D^{**0}{\pi }^{-})$ agree with experiment. The sign of the $D_1^{1/2}-D_1^{3/2}$ mixing angle is found to be positive in order to avoid a severe suppression of the production of $D_1{\mathrm{}\left(2427\right)\mathrm{}}^0{\pi }^{-}.$ The interference between color-allowed and color-suppressed tree amplitudes is expected to be destructive in the decay $B^{-}\to D_1{\mathrm{}\left(2427\right)\mathrm{}}^0{\pi }^{-}.$ Hence, an observation of the ratio $D_1{\mathrm{}\left(2427\right)\mathrm{}}^0{\pi }^{-}{/D}_1{\mathrm{}\left(2427\right)\mathrm{}}^{+}{\pi }^{-}$ can be used to test the relative signs of various form factors as implied by heavy quark symmetry. Although the predicted $B^{-}\to D_1{\mathrm{}\left(2420\right)\mathrm{}}^0{\rho }^{-}$ at the level of $3\times {10}^{-3}$ exceeds the present upper limit, it leads to the ratio $D_1\mathrm{}\left(2420\right)\mathrm{}{\rho }^{-}{/D}_1\mathrm{}\left(2420\right)\mathrm{}{\pi }^{-}\approx 2.6,$ as expected from the factorization approach and from the ratio $f_{\rho }{/f}_{\pi }\approx \mathrm{1.6.}$ Therefore, it is crucial to have a measurement of this mode to test the factorization hypothesis. For $\overline{B}\to D_s^{**}D$ decays, it is expected that $D_{s0\mathrm{}}^{*}D\gtrsim D_{s1\mathrm{}}D$ as the decay constants of the multiplet ${(D}_{s0\mathrm{}}^{*}{,D}_{s1\mathrm{}})$ become the same in the heavy quark limit. The preliminary Belle observation of fairly less abundant production of $D_{s0\mathrm{}}^{*}D$ than $D_{s1\mathrm{}}D$ is thus a surprise. What is the cause for the discrepancy between theory and experiment remains unclear. Meanwhile, it is also important to measure the B decay into $D_{s1\mathrm{}}{\mathrm{}\left(2536\right)D}^{\left(*\right)}$ to see if it is suppressed relative to $D_{s1\mathrm{}}{\mathrm{}\left(2463\right)D}^{\left(*\right)}$ to test the heavy quark symmetry relation $f_{D_{s1\mathrm{}}\mathrm{}\left(2536\right)\mathrm{}}\ll f_{D_{s1\mathrm{}}\mathrm{}\left(2463\right)\mathrm{}}.$ Under the factorization hypothesis, the production of $D_{s2\mathrm{}}^{*}D$ is prohibited as the tensor meson cannot be produced from the $V-A$ current. Nevertheless, it can be induced via final-state interactions or nonfactorizable contributions and hence an observation of $\overline{B}\to D_{s2\mathrm{}}^{*}{D}^{\left(*\right)}$ could imply the importance of final-state rescattering effects.

We propose parametrizations of the neutrino mixing matrix. We discuss several Ansätze: in some of them $V_{e3\mathrm{}}=0\mathrm{}$ but in others $V_{e3\mathrm{}}$ typically “comes out” to be of the order $\simeq \mathrm{0.05.}$

We report the observation of $823\pm 57$ $B^0$ and $970\pm 65$ $B^{+}$ decays to doubly charmed final states $D^{\left(*\right)}{D}^{\left(*\right)}K,$ where $D^{\left(*\right)}$ and $D^{\left(*\right)}$ are fully reconstructed and K is either a $K^{\pm }$ or a $K^0.$ We use a sample of $82.3\pm 0.9$ million $B\overline{B}$ events collected between 1999 and 2002 with the BABAR detector at the PEP-II storage ring at the Stanford Linear Accelerator Center. The 22 possible B decays to $D^{\left(*\right)}{D}^{\left(*\right)}K$ are reconstructed exclusively and the corresponding branching fractions or limits are determined. The branching fractions of the $B^0$ and of the $B^{+}$ to $D^{\left(*\right)}{D}^{\left(*\right)}K$ are found to be $\mathcal{B}{(B}^0\to D^{\left(*\right)}{D}^{\left(*\right)}K)=[4.3\pm 0.3\left(\mathrm{stat}\right)\pm 0.6\left(\mathrm{syst}\right)]\%,$ $\mathcal{B}{(B}^{+}\to D^{\left(*\right)}{D}^{\left(*\right)}K)=[3.5\pm 0.3\left(\mathrm{stat}\right)\pm 0.5\left(\mathrm{syst}\right)]\%.\mathrm{}$ A search for decays to orbitally excited $D_s$ states, $\overrightarrow{B}{D}^{\left(*\right)}{D}_{\mathrm{sJ}}^{+}$ ${(D}_{\mathrm{sJ}}^{+}\to D^{\left(*\right)0\mathrm{}}{K}^{+}),$ is also performed. No statistically significant contributions from $D_{s1\mathrm{}}^{+}\mathrm{}\left(2536\right)\mathrm{}\to D^{*0}{K}^{+}$ and $D_{\mathrm{sJ}}^{+}\mathrm{}\left(2573\right)\mathrm{}\to D^0{K}^{+}$ to the $D^{\left(*\right)}{D}^{\left(*\right)0\mathrm{}}{K}^{+}$ final state are found and we set 90% C.L. limits on their production rates.

The model of a spinning particle, based on the Kerr-Newman solution with $|a|\gg m,$ is discussed. It is shown that the Kerr singular ring can be considered as a string with an orientifold world sheet. The orientifold adds a peculiar extra point to the Kerr ring: the fixed point of the world-sheet parity operator $\Omega .$ It is shown that the Kerr string represents a new type of folded string solution taking the form of an open D-string with joined ends which are in circular lightlike motion along the Kerr ring.

The group field theories realizing the sum over all triangulations of all topologies of 3D discrete gravity amplitudes are known to be nonuniquely Borel summable. We modify these models to construct a new group field theory which is proved to be uniquely Borel summable, defining in an unambiguous way a nonperturbative sum over topologies in the context of 3D dynamical triangulations and spin foam models. Moreover, we give some arguments to support the fact that, despite our modification, this new model is similar to the original one, and therefore could be taken as a definition of the sum over topologies of 3D quantum gravity amplitudes.

We present a new class of static axially symmetric solutions of SU(2) Yang-Mills-Higgs theory, where the Higgs field vanishes on rings centered around the symmetry axis. Associating a magnetic dipole moment with each Higgs vortex ring, the dipole moments add for solutions in the trivial topological sector, whereas they cancel for magnetically charged solutions.

In this Brief Report we discuss a determination for the mass of the $D_s{(0\mathrm{}}^{+}{,1\mathrm{}}^{+})$ system recently discovered by the BaBar, CLEO II and Belle Collaborations. The value of the mass is derived by making explicit the prediction obtained in a quark-meson model prior to the discovery of these states.

The lepton-flavor-violating signals $e^{+}{e}^{-}\to {\mathcal{l}}^{+}{e}^{-}$ and $e^{-}{e}^{-}\to {\mathcal{l}}^{-}{e}^{-}(\mathcal{l}=\mu ,\tau )$ are studied in the context of low-energy R-parity-conserving supersymmetry at center-of-mass energies of interest for the next generation of linear colliders. Loop level amplitudes receive contributions from electroweak penguin and box diagrams involving sleptons and gauginos. Lepton flavor violation is due to off-diagonal elements in a ${\mathrm{SU}\left(2\right)\mathrm{}}_L$ doublet slepton mass matrix. These masses are treated as model-independent free phenomenological parameters in order to discover regions in parameter space where the signal cross section may be observable. The results are compared with (a) the experimental bounds from the nonobservation of rare radiative lepton decays $\mu ,\overrightarrow{\tau }e\gamma$ and (b) the general MSUGRA theoretical scenario with the seesaw mechanism where off-diagonal slepton matrix entries are generated by renormalization group evolution of neutrino Yukawa couplings induced by the presence of new energy scales set by the heavy ${\mathrm{SU}\left(2\right)\mathrm{}}_L$ singlet neutrino masses. It is found that in $e^{-}{e}^{-}$ collisions the $\left(e\tau \right)$ signal can be observable with a total integrated luminosity of $100{\mathrm{fb}}^{-1}$ and the background can be easily suppressed. In $e^{+}{e}^{-}$ collisions the cross section is smaller and higher luminosities are needed. The experimental bound on the decay $\overrightarrow{\mu }e\gamma$ prevents the $\left(e\mu \right)$ signal from being observable.

We use the nonrelativistic expansion of QCD (NRQCD) on the lattice to study the lowest hybrid configuration contribution to the ground state of heavy S-wave mesons. Using lowest-order lattice NRQCD to create the heavy-quark propagators, we form a basis of “unperturbed” S-wave and hybrid states. We then apply the lowest-order coupling of the quark spin and chromomagnetic field at an intermediate time slice to create “mixed” correlators between the S-wave and hybrid states. From the resulting amplitudes, we extract the off-diagonal element of our two-state Hamiltonian. Diagonalizing this Hamiltonian gives us the admixture of a hybrid configuration within the meson ground state. The present effort represents a continuation of previous work: the analysis has been extended to include lattices of varying spacings, source operators having better overlap with the ground states, and the pseudoscalar (along with the vector) channel. Results are presented for bottomonium $({\rm Y},{\eta }_b)$ using three different sets of quenched lattices. We also show results for charmonium $(J/\psi ,{\eta }_c)$ from one lattice set, although we note that the nonrelativistic approximation is not expected to be very good in this case.

We describe a calculation using quenched lattice QCD of the connected part of the neutron electric form factor for momentum transfers in the range $0.3{\mathrm{GeV}}^2\lesssim -q^2\lesssim 1.0{\mathrm{GeV}}^2.$ We extract the implied charge radius using a Galster parametrization and consider various ways of extrapolating the neutron charge radius value to the chiral limit. We find that the measured charge radii may be reconciled to experiment by standard phenomenology and lowest or next to lowest order contributions from chiral perturbation theory.