We report a measurement of the ratio of the bottom quark production cross section in antiproton-proton collisions at $\sqrt{s}=630\mathrm{}\hspace{0.5em}\mathrm{GeV}$ to 1800 GeV using bottom quarks with transverse momenta greater than 10.75 GeV identified through their semileptonic decays and long lifetimes. The measured ratio $\sigma \mathrm{}\left(630\right)/\sigma \mathrm{}\left(1800\right)=0.171\mathrm{}\pm .024\pm .012$ is in good agreement with next-to-leading order quantum chromodynamics.

The cross section of the process $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0$ was measured in the Spherical Neutral Detector experiment at the VEPP-2M collider in the energy region $\sqrt{s}=980\mathrm{}–1380\hspace{0.5em}\mathrm{MeV}.$ The measured cross section, together with the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0$ and $\omega {\pi }^{+}{\pi }^{-}$ cross sections obtained in other experiments, was analyzed in the framework of the generalized vector meson dominance model. It was found that the experimental data can be described by a sum of $\omega ,$ $\phi$ mesons and two ${\omega }^{\prime }$ and ${\omega }^{″}$ resonances contributions, with masses $m_{{\omega }^{\prime }}\sim 1490,$ $m_{{\omega }^{″}}\sim 1790\hspace{0.5em}\mathrm{MeV}$ and widths ${\Gamma }_{{\omega }^{\prime }}\sim 1210,$ ${\Gamma }_{{\omega }^{″}}\sim 560\hspace{0.5em}\mathrm{MeV}.$ The analysis of the ${\pi }^{+}{\pi }^{-}$ invariant mass spectra in the energy region $\sqrt{s}$ from 1100 to 1380 MeV has shown that for their description one should take into account the $e^{+}{e}^{-}\to \omega {\pi }^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ mechanism also. The phase between the amplitudes corresponding to the $e^{+}{e}^{-}\to \omega \pi$ and $e^{+}{e}^{-}\to \rho \pi$ intermediate states was measured for the first time. The value of the phase is close to zero and depends on energy.

In models with large extra dimensions all gauge singlet fields can in principle propagate in the extra dimensional space. We have investigated possible constraints on Majoron models of neutrino masses in which the Majorons propagate in extra dimensions. It is found that astrophysical constraints from supernovae are many orders of magnitude stronger than previous accelerator bounds. Our findings suggest that unnatural types of the “seesaw” mechanism for neutrino masses are unlikely to occur in nature, even in the presence of extra dimensions.

If we replace the general spacetime group of diffeomorphisms by transformations taking place in the tangent space, general relativity can be interpreted as a gauge theory, and in particular as a gauge theory for the Lorentz group. In this context, it is shown that the angular momentum and the energy-momentum tensors of a general matter field can be obtained from the invariance of the corresponding action integral under transformations taking place, not in spacetime, but in the tangent space, in which case they can be considered as gauge currents.

We examine whether cosmologies with a varying speed of light (VSL) are compatible with the second law of thermodynamics. We find that the VSL cosmology with a varying fundamental constant is severely constrained by the second law of thermodynamics, whereas the bimetric cosmological models are less constrained.

We study the applicability of the mass insertion approximation (MIA) for calculations of neutral meson mixing when squark masses are not degenerate and, in particular, in models of alignment. We show that the MIA can give results that are much better than an order of magnitude estimate as long as the masses are not strongly hierarchical. We argue that, in an effective two-squark framework, $m_q=(m_1+m_1)/2\mathrm{}$ is the best choice for the MIA expansion point, rather than, for example, $m_q^2=(m_1^2+m_2^2)/2.\mathrm{}$

The assignments of the isoscalar scalar mesons $f_0\mathrm{}\left(980\right),$ $f_0\mathrm{}\left(1370\right),$ and $f_0\mathrm{}\left(1500\right)\mathrm{}$ in terms of their flavor substructure is still a matter of heated dispute. Here we employ the weak and electromagnetic decays $D_s^{+}\to f_0{\pi }^{+}$ and $f_0\to \gamma \gamma ,$ respectively, to identify the $f_0\mathrm{}\left(980\right)\mathrm{}$ and $f_0\mathrm{}\left(1500\right)\mathrm{}$ as mostly $\overline{s}s,$ and the $f_0\mathrm{}\left(1370\right)\mathrm{}$ as dominantly $\mathrm{n̄}n,$ in agreement with previous work. The two-photon decays can be satisfactorily described with quark as well as with meson loops, though the latter ones provide a less model-dependent and more quantitative description.

We use momentum correlations as physical observables in $\overrightarrow{B}{K}^{*}{l}^{+}{l}^{-}$ decays with $K^{*}$ polarized to study the long distance contributions. We show that these observables are sensitive to the scenarios of the long distance parametrizations. We find that the T-odd observable is directly related to the nonfactorizable effect in the standard model.

It is argued that a fundamental time asymmetry could arise from the global structure of the space manifold. The proposed mechanism relies on the $\mathrm{CPT}$ anomaly of certain chiral gauge theories defined over a multiply connected space manifold. The resulting time asymmetry (microscopic arrow of time) is illustrated by a simple thought experiment. The effect could, in principle, play a role in determining the initial conditions of the big bang.

We consider the tensor theory on coincident $E_8$ 5-branes compactified on $T^3.$ Using string theory, we predict that there must be distinct components in the moduli space of this theory. We argue that new superconformal field theories are to be found in these sectors with, for example, global $G_2$ and $F_4$ symmetries. In some cases, twisted $E_8$ 5-branes can be identified with small instantons in nonsimply laced gauge groups. This allows us to determine the Higgs branch for the fixed point theory. We determine the Coulomb branch by using an M theory dual description involving partially frozen singularities. Along the way, we show that a D0-brane binds to two D4-branes, but not to an Sp-type O4-plane (despite the existence of a Higgs branch). These results are used to check various string or string dualities for which, in one case (quadruple versus NVS), we present a new argument. Finally, we describe the construction of new non-BPS branes as domain walls in various heterotic or type I string theories.

The inflaton condensate associated with a global symmetry can fragment into quasistable Q balls, provided the inflaton oscillations give rise to an effective equation of state with negative pressure. We study chaotic inflation with a running inflaton mass and show that, depending on the sign of the radiative mass correction, the process of fragmentation into inflatonic Q balls can actually take place even though no net charge exists. If the main decay channel of the Q ball is to fermions, the universe will be reheated slowly via surface evaporation.

Provided that matter-antimatter domains are present at the onset of big bang nucleosynthesis (BBN), the number of allowed additional relativistic species increases, compared to the standard scenario when matter-antimatter domains are absent. The extra relativistic species may take the form of massless fermions or even massless bosons, such as relic gravitons. The number of additional degrees of freedom compatible with BBN depends, in this framework, upon the typical scale of the domains and the antimatter fraction. Since the presence of matter-antimatter domains allows a reduction of the neutron to proton ratio prior to the formation of ${}^4\mathrm{He},$ large amounts of radiationlike energy density are allowed. Our results are compared with other constraints on the number of supplementary relativistic degrees of freedom and with different nonstandard BBN scenarios where the reduction of the neutron to proton ratio occurs via a different physical mechanism. The implications of our considerations for the upper limits on stochastic gravitational waves backgrounds of cosmological origin are outlined.

The best-known way of stabilizing textures is by Skyrme-like terms, but another possibility is to use gauge fields. The semilocal vortex may be viewed as an example of this, in two spatial dimensions. In three dimensions, however, the idea (in its simplest form) does not work—the link between the gauge field and the scalar field is not strong enough to prevent the texture from collapsing. Modifying the $|D\Phi {|}^2$ term in the Lagrangian (essentially by changing the metric on the $\Phi$ space) can strengthen this link, and lead to stability. Furthermore, there is a limit in which the gauge field is entirely determined in terms of the scalar field, and the system reduces to a pure Skyrme-like one. This is described for the gauge group U(1), in dimensions two and three. The non-Abelian version is discussed briefly, but as yet no examples of texture stabilization are known in this case.

The nature of dark matter is increasingly constrained by cosmological data. In this paper, we examine the implications of the cosmic microwave background anisotropy limits on the density of cold dark matter under different theoretical assumptions and combinations of data sets. We infer the constraint ${\Omega }_{\mathrm{cdm}}{h}^2=0.12\mathrm{}\pm 0.04$ (at $95\%$ C.L.). The CDM models are compared with the shape of the linear matter power spectrum inferred from the 2dF galaxy redshift survey and with the rms mass fluctuations from recent local cluster observations. We found that a value of ${\sigma }_8\sim 1$ as suggested by recent cosmic shear data is not favored by the CMB data alone nor by combined CMB+SN-Ia, CMB+HST or CMB+2dFGRS analyses. We also extrapolate our bounds on the rms linear mass fluctuations to subgalactic scales and compare them with recent lensing constraints, finding agreement with the standard $\Lambda \mathrm{CDM}$ model.

In this paper we study the possibility of generalizing the classical photoabsorption $\left(\gamma \overrightarrow{a}bc\right)$ sum rules to processes $b\overrightarrow{c}\gamma a$ and crossed helicity amplitudes. In the first case, using detailed balance, the sum rule is written as ${\int }_{{\nu }_{\mathrm{th}}}^{\infty }(d\nu /\nu )K\Delta {\sigma }_{\mathrm{Born}}\left(\nu \right)=0\mathrm{}$ where K is a kinematical constant which depends only on the mass of the particles and the center of mass energy. For other crossed helicity amplitudes, we show that there is a range of values of s and t for which the differential cross section for the process $\gamma \overrightarrow{b}\mathrm{ac}$ or $a\overrightarrow{c}\gamma b,$ in which the helicities of the photon and particle a have specific values, is equal to the differential cross section for the process in which one of these two helicities is reversed (parallel-antiparallel spin correlation).

If the minimal standard model of particle interactions is extended to include a scalar triplet with a lepton number $L=-2$ and a scalar doublet with $L=-1,$ neutrino masses $m_{\nu }\sim {\mu }_{12}^4{v}^2{/M}^5\sim {10}^{-2}\hspace{0.5em}\mathrm{eV}$ are possible, where $v\sim {10}^2\hspace{0.5em}\mathrm{GeV}$ is the electroweak symmetry breaking scale, $M\sim 1\hspace{0.5em}\mathrm{TeV}$ is the typical mass of the new scalars, and ${\mu }_{12}\sim 1\hspace{0.5em}\mathrm{GeV}$ is a soft lepton-number-violating parameter.

We analyze $K_L$ lepton pair decays of $K_L\to l^{+}{l}^{-}\gamma$ and $K_L\to l^{+}{l}^{-}{l}^{\prime +}{l}^{\prime -}(l,l^{\prime }=e,\mu )$ within the framework of the light-front QCD approach (LFQA). With the $K_L\to {\gamma }^{*}{\gamma }^{*}$ form factors evaluated in a model with the LFQA, we calculate the decay branching ratios and find that our results are all consistent with the experimental data. In addition, we study $K_L\to l^{+}{l}^{-}$ decays. We point out that our prediction for $K_L\to e^{+}{e}^{-}$ is about $20\%$ smaller than that in chiral perturbation theory. We also discuss whether one could extract the short-distance physics from $K_L\to {\mu }^{+}{\mu }^{-}.$

The DAMA-NaI Collaboration has observed a $4\sigma$ C.L. model-independent effect investigating the annual modulation signature in the counting rate of an NaI(Tl) setup (total exposure of 57986 kg day) and the implications of this effect have been studied under different model-dependent assumptions. In this paper we extend one of the previous analyses, the case of a WIMP with a purely spin-independent coupling, by discussing in detail the implications on the results of the uncertainties on the dark matter galactic velocity distribution. We study in a systematic way possible departures from the isothermal sphere model, which is the parametrization usually adopted to describe the halo. We specifically consider modifications arising from various matter density profiles, effects due to anisotropies of the velocity dispersion tensor and rotation of the galactic halo. The hypothesis of WIMP annual modulation, already favored in the previous analysis using an isothermal sphere, is confirmed in all the investigated scenarios, and the effects of the different halo models on the determination of the allowed maximum-likelihood region in the WIMP mass and WIMP-nucleon cross section are derived and discussed.