We search for the rare leptonic decay $B^{+}\to {\tau }^{+}{\nu }_{\tau }$ in a sample of $232\times {10}^6$ $B\overline{B}$ pairs collected with the BABAR detector at the SLAC PEP-II $B$-Factory. Signal events are selected by examining the properties of the $B$ meson recoiling against the semileptonic decay $B^{-}\to D^{*0}{\ell }^{-}{\overline{\nu }}_{\ell }$. We find no evidence for a signal and set an upper limit on the branching fraction of $\mathcal{B}(B^{+}\to {\tau }^{+}{\nu }_{\tau })<2.8\times {10}^{-4}$ at the 90% confidence level. We combine this result with a previous, statistically independent BABAR search for $B^{+}\to {\tau }^{+}{\nu }_{\tau }$ to give an upper limit of $\mathcal{B}(B^{+}\to {\tau }^{+}{\nu }_{\tau })<2.6\times {10}^{-4}$ at the 90% confidence level.

We analyze the impact of a measurement, or of an improved bound, on ${\theta }_{13}$ for the determination of the effective neutrino mass in neutrinoless double beta decay and cosmology. In particular, we discuss how an improved limit on (or a specific value of) ${\theta }_{13}$ can influence the determination of the neutrino mass spectrum via neutrinoless double beta decay. We also discuss the interplay with improved cosmological neutrino mass searches.

A new measurement of the $b\overline{b}$ production cross section in 920 GeV proton-nucleus collisions is presented by the HERA-B Collaboration. The $b\overline{b}$ production is tagged via inclusive bottom quark decays into $J/\psi$ mesons by exploiting the longitudinal separation of $J/\psi \to l^{+}{l}^{-}$ decay vertices from the primary proton-nucleus interaction point. Both $e^{+}{e}^{-}$ and ${\mu }^{+}{\mu }^{-}$ channels are reconstructed for a total of $83\pm 12$ inclusive $b\to J/\psi X$ events found. The combined analysis yields a $b\overline{b}$ to prompt $J/\psi$ cross section ratio of $\frac{\Delta \sigma (b\overline{b})}{\Delta {\sigma }_{J/\psi }}=0.032\pm {0.005}_{\mathrm{stat}}\pm {0.004}_{\mathrm{sys}}$ measured in the $x_F$ acceptance ($-0.35<x_F<0.15$), extrapolated to $\sigma (b\overline{b})=14.9\pm {2.2}_{\mathrm{stat}}\pm {2.4}_{\mathrm{sys}}\mathrm{\text{nb/nucleon}}$ in the total phase space.

$K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}{\pi }^0$ final states are studied using a sample of $14\times {10}^6$ $\psi (2S)$ decays collected with the Beijing Spectrometer (BESII) at the Beijing Electron-Positron Collider. The branching fractions of $\psi (2S)$ decays to $K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}{\pi }^0$, $\omega K^{+}{K}^{-}$, $\omega f_0(1710)$, $K^{*}(892{)}^0{K}^{-}{\pi }^{+}{\pi }^0+\mathrm{c}.\mathrm{c}.$, $K^{*}(892{)}^{+}{K}^{-}{\pi }^{+}{\pi }^{-}+\mathrm{c}.\mathrm{c}.$, $K^{*}(892{)}^{+}{K}^{-}{\rho }^0+\mathrm{c}.\mathrm{c}.$ and $K^{*}(892{)}^0{K}^{-}{\rho }^{+}+\mathrm{c}.\mathrm{c}.$ are determined. The first two agree with previous measurements, and the last five are first measurements.

We consider supersymmetric models with right-handed neutrinos where neutrino masses are purely Dirac-type. In this model, right-handed sneutrino can be the lightest supersymmetric particle and can be a viable candidate of cold dark matter of the universe. Right-handed sneutrinos are never thermalized in the early universe because of weakness of Yukawa interaction, but are effectively produced by decays of various superparticles. We show that the present mass density of right-handed sneutrino can be consistent with the observed dark matter density.

Using the mixed space representation, we extend our earlier analysis to the case of Dirac and gauge fields and show that in the absence of a chemical potential, the finite temperature Feynman diagrams can be related to the corresponding zero temperature graphs through a thermal operator. At nonzero chemical potential we show explicitly in the case of the fermion self-energy that such a factorization is violated because of the presence of a singular contact term. Such a temperature dependent term which arises only at finite density and has a quadratic mass singularity cannot be related, through a regular thermal operator, to the fermion self-energy at zero temperature which is infrared finite. Furthermore, we show that the thermal radiative corrections at finite density have a screening effect for the chemical potential leading to a finite renormalization of the potential.

Some tests of gravity theories—periastron shift, geodetic precession, change in mean motion and gravitational redshift—are applied in solar and stellar systems to constrain the cosmological constant. We thus consider a length scale range from $\sim {10}^8$ to $\sim {10}^{15}\mathrm{km}$. Best bounds from the solar system come from perihelion advance and change in mean motion of Earth and Mars, $\Lambda \lesssim {10}^{-36}{\mathrm{km}}^{-2}$. Such a limit falls very short to estimates from observational cosmology analyses but a future experiment performing radio ranging observations of outer planets could improve it by 4 orders of magnitude. Beyond the solar system, together with future measurements of periastron advance in wide binary pulsars, gravitational redshift of white dwarfs can provide bounds competitive with Mars data.

We study the process of the association production of chargino and neutralino including the next-to-leading order (NLO) QCD and the complete one-loop electroweak corrections in the framework of the minimal supersymmetric standard model at the Fermilab Tevatron and the CERN Large Hadron Collider. In both the NLO QCD and one-loop electroweak calculations we apply the algorithm of the phase-space slicing method. We find that the NLO QCD corrections generally increase the Born cross sections, while the electroweak relative corrections decrease the Born cross section in most of the chosen parameter space. The NLO QCD and electroweak relative corrections typically have the values of about 32% and $-8\%$ at the Tevatron, and about 42% and $-6\%$ at the Large Hadron Collider, respectively. The results show that both the NLO QCD and the complete one-loop electroweak corrections to the processes $p\overline{p}/pp\to {\tilde{\chi }}_1^{\pm }{\tilde{\chi }}_2^0+X$ are generally significant and should be taken into consideration in precision experimental analysis.

We reconsider the well-known issue of string corrections to supergravity theory. Our treatment is carried out to second order in the string slope parameter. We establish a procedure for solving the Bianchi identities in the nonminimal case, and we solve a long standing problem in the perturbative expansion of $\mathrm{D}=10$, $\mathrm{N}=1$ string corrected supergravity, obtaining the $H$ sector tensors, torsions and curvatures.

In this paper we consider magnetized black holes and black rings in the higher dimensional dilaton gravity. Our study is based on exact solutions generated by applying a Harrison transformation to known asymptotically flat black hole and black ring solutions in higher dimensional spacetimes. The explicit solutions include the magnetized version of the higher dimensional Schwarzschild-Tangherlini black holes, Myers-Perry black holes, and five-dimensional (dipole) black rings. The basic physical quantities of the magnetized objects are calculated. We also discuss some properties of the solutions and their thermodynamics. The ultrarelativistic limits of the magnetized solutions are briefly discussed and an explicit example is given for the $D$-dimensional magnetized Schwarzschild-Tangherlini black holes.

A mass function of small-scale dark matter clumps is calculated in the standard cosmological scenario with an inflationary-produced primordial fluctuation spectrum and with a hierarchical clustering. We take into account the tidal destruction of clumps at early stages of structure formation starting from a time of clump detachment from the Universe expansion. Only a small fraction of these clumps, $\sim 0.1\%–0.5\%$, in each logarithmic mass interval $\Delta \log M\sim 1$ survives the stage of hierarchical clustering. The surviving clumps can be disrupted further in the galaxies by tidal interactions with stars. We performed the detailed calculations of the tidal destruction of clumps by stars in the Galactic bulge and halo and by the Galactic disk itself. It is shown that the Galactic disc provides the dominant contribution to the tidal destruction of small-scale clumps outside the bulge. The results obtained are crucial for calculations of the dark matter annihilation signal in the Galaxy.

We discuss the ordinary, nonsupersymmetric SO(10) as a theory of fermion masses and mixings. We construct two minimal versions of the Yukawa sector based on ${\overline{\mathbf{126}}}_{\mathbf{H}}$ and either ${\mathbf{10}}_{\mathbf{H}}$ or ${\mathbf{120}}_{\mathbf{H}}$. The latter case is of particular interest since it connects the absolute neutrino mass scale with the size of the atmospheric mixing angle ${\theta }_A$. It also relates the smallness of $V_{cb}$ with the largeness of ${\theta }_A$. These results are based on the analytic study of the second and third generations. Furthermore, we discuss the structure of the light Higgs and the role of the Peccei-Quinn symmetry for dark matter and the predictivity of the theory.

We investigate the properties of $Q$-balls in $d$ spatial dimensions. First, a generalized virial relation for these objects is obtained. We then focus on potentials $V(\varphi {\varphi }^{†})=\sum _{n=1}^3{a}_n(\varphi {\varphi }^{†}{)}^n$, where $a_n$ is a constant and $n$ is an integer, obtaining variational estimates for their energies for arbitrary charge $Q$. These analytical estimates are contrasted with numerical results and their accuracy evaluated. Based on the results, we offer a simple criterion to classify large and small $d$-dimensional $Q$-balls for this class of potentials. A minimum charge is then computed and its dependence on spatial dimensionality is shown to scale as $Q_{\min }\sim \exp (d)$. We also briefly investigate the existence of $Q$-clouds in $d$ dimensions.

We find giant graviton solutions in Frolov’s three parameter generalization of the Lunin-Maldacena background. The background we study has ${\tilde{\gamma }}_1=0$ and ${\tilde{\gamma }}_2={\tilde{\gamma }}_3=\tilde{\gamma }$. This class of backgrounds provides a nonsupersymmetric example of the gauge theory/gravity correspondence that can be tested quantitatively, as recently shown by Frolov, Roiban, and Tseytlin. The giant graviton solutions we find have a greater energy than the point gravitons, making them unstable states. Despite this, we find striking quantitative agreement between the gauge theory and gravity descriptions of open strings attached to the giant.

We report on a search for gravitational waves from binary black hole inspirals in the data from the second science run of the LIGO interferometers. The search focused on binary systems with component masses between 3 and $20M_{\odot }$. Optimally oriented binaries with distances up to 1 Mpc could be detected with efficiency of at least 90%. We found no events that could be identified as gravitational waves in the 385.6 hours of data that we searched.

We study the processes $e^{+}{e}^{-}\to 3({\pi }^{+}{\pi }^{-})\gamma$, $2({\pi }^{+}{\pi }^{-}{\pi }^0)\gamma$ and $K^{+}{K}^{-}2({\pi }^{+}{\pi }^{-})\gamma$, with the photon radiated from the initial state. About 20 000, 33 000 and 4000 fully reconstructed events, respectively, have been selected from $232{\mathrm{fb}}^{-1}$ of BABAR data. The invariant mass of the hadronic final state defines the effective $e^{+}{e}^{-}$ center-of-mass energy, so that these data can be compared with the corresponding direct $e^{+}{e}^{-}$ measurements. From the $3({\pi }^{+}{\pi }^{-})$, $2({\pi }^{+}{\pi }^{-}{\pi }^0)$ and $K^{+}{K}^{-}2({\pi }^{+}{\pi }^{-})$ mass spectra, the cross sections for the processes $e^{+}{e}^{-}\to 3({\pi }^{+}{\pi }^{-})$, $e^{+}{e}^{-}\to 2({\pi }^{+}{\pi }^{-}{\pi }^0)$ and $e^{+}{e}^{-}\to K^{+}{K}^{-}2({\pi }^{+}{\pi }^{-})$ are measured for center-of-mass energies from production threshold to 4.5 GeV. The uncertainty in the cross section measurement is typically 6%–15%. We observe a structure at 1.9 GeV in both cross sections and a resonance structure with mass $1645\pm 0.008\mathrm{GeV}/{\mathrm{c}}^2$ and width $0.114\pm 0.014\mathrm{GeV}$ when the $\omega (782)\eta$ final state is extracted. We observe the $J/\psi$ in all these final states and measure the corresponding branching fractions.

A group of fuzzy spacetime with $SU(3)$ isometry is studied at the two-loop level in a IIB matrix model. It consists of spacetime from four to six dimensions, namely, from $C{P}^2$ to $SU(3)/U(1)\times U(1)$. The effective action scales in a universal manner in the large $N$ limit as $N$ and $N^{4/3}$ on four- and six-dimensional manifolds, respectively. The four-dimensional spacetime $C{P}^2$ possesses the smallest effective action in this class.

We compute two infinite series of tree-level amplitudes with a massive-scalar pair and an arbitrary number of gluons. We provide results for amplitudes where all gluons have identical helicity, and amplitudes with one gluon of opposite helicity. These amplitudes are useful for unitarity-based one-loop calculations in nonsupersymmetric gauge theories generally, and QCD, in particular.

In this paper, we study the bulk motion of a classical extended charge in flat spacetime. A formalism developed by W. G. Dixon is used to determine how the details of such a particle’s internal structure influence its equations of motion. We place essentially no restrictions (other than boundedness) on the shape of the charge, and allow for inhomogeneity, internal currents, elasticity, and spin. Even if the angular momentum remains small, many such systems are found to be affected by large self-interaction effects beyond the standard Lorentz-Dirac force. These are particularly significant if the particle’s charge density fails to be much greater than its 3-current density (or vice versa) in the center-of-mass frame. Additional terms also arise in the equations of motion if the dipole moment is too large, and when the “center-of-electromagnetic mass” is far from the “center-of-bare mass” (roughly speaking). These conditions are often quite restrictive. General equations of motion were also derived under the assumption that the particle can only interact with the radiative component of its self-field. These are much simpler than the equations derived using the full retarded self-field; as are the conditions required to recover the Lorentz-Dirac equation.