We present measurements of the production of high transverse momentum ${\pi }^0$ and $\eta$ mesons in $\mathrm{pp}$ and $p\mathrm{Be}$ interactions at 530 and $800\mathrm{GeV}/c.\mathrm{}$ The data span the kinematic ranges: $1<\mathrm{}{p}_T<10\mathrm{}\mathrm{GeV}/c$ in transverse momentum and 1.5 units in rapidity. The inclusive ${\pi }^0$ cross sections are compared with next-to-leading order QCD calculations and to expectations based on a phenomenological parton-$k_T$ model.

We consider a simple rescattering mechanism to calculate a leading twist T-odd pion fragmentation function, a favored candidate for filtering the transversity properties of the nucleon. We evaluate the single spin azimuthal asymmetry for a transversely polarized target in semi-inclusive deep inelastic scattering (for HERMES kinematics). Additionally, we calculate the double T-odd $\cos 2\phi$ asymmetry in this framework.

Within the framework of an SU(5) SUSY GUT model, a mechanism which effectively induces R-parity-violating terms below the unification energy scale $M_X$ is proposed. The model has matter fields $5_{L(+)\mathrm{}}{+10\mathrm{}}_{L\left(-\right)}$ and Higgs fields $H_{\left(-\right)}$ and $H_{\mathrm{}(+)\mathrm{}}$ in addition to the ordinary Higgs fields $H_{\mathrm{}(+)\mathrm{}}$ and $H_{\left(-\right)}$ which contribute to the Yukawa interactions, where $(\pm )$ denote the transformation properties under a discrete symmetry $Z_2.$ The $Z_2$ symmetry is only broken by the $\mu$ term $H_{\mathrm{}(+)\mathrm{}}{H}_{\left(-\right)}$ softly, so that the $5_{\mathrm{}(+)\mathrm{}}\leftrightarrow H_{\mathrm{}(+)\mathrm{}}\leftrightarrow H_{\left(-\right)}$ mixing appears at $\mu <m_{\mathrm{SB}},$ and R-parity violating terms $5_L{5}_L{10}_L$ are effectively induced from the Yukawa interactions $H_{\left(-\right)}{5}_{L(+)\mathrm{}}{10}_{L\left(-\right)};$ i.e., the effective coupling constants ${\lambda }_{\mathrm{ijk}}$ of ${\nu }_{\mathrm{Li}}{e}_{\mathrm{Lj}}{e}_{\mathrm{Rk}}^c$ and ${\nu }_{\mathrm{Li}}{d}_{\mathrm{Rj}}^c{d}_{\mathrm{Lk}}$ are proportional to the mass matrices ${(M}_e^{*}{)}_{\mathrm{jk}}$ and ${(M}_d^{†}{)}_{\mathrm{jk}},$ respectively. The parameter regions which are harmless for the proton decay are investigated. Possible forms of the radiatively induced neutrino mass matrix are also investigated.

We demonstrate that the two major complementary pictures of large $N_c$ baryon resonances—as single-quark orbital excitations about a closed-shell core [giving $\mathrm{SU}{(2N}_F)\times \mathrm{O}\mathrm{}(3)\mathrm{}$ multiplets], and as resonances in meson-baryon scattering amplitudes—are completely compatible in a specific sense: Both pictures give rise to a set of multiplets of degenerate states, for which any complete spin-flavor multiplet within one picture fills the quantum numbers of complete multiplets in the other picture. This result is demonstrated by (i) straightforward computation of the lowest multiplets in both pictures, (ii) a study of the nature of quark excitations in a hedgehog picture, and (iii) direct group-theoretical comparison of the constraints in the two pictures.

Requiring the two-Higgs-doublet model II to accommodate the $3\sigma$ deviation in the muon anomalous magnetic moment imposes specific constraints on the Higgs spectrum. We analyze the combination of all the relevant available constraints on the model parameter space. The use of constraints from $\overrightarrow{b}s\gamma ,$ the precision electroweak measurements of $R_b,$ and the $\rho$ parameter, together with exclusions from direct searches at CERN LEP, gives extremely severe restrictions on the model parameters. That is “almost enough” to destroy the model altogether. The exclusion would be even stronger if the direct searches could be optimized to complement the other constraints, as will be discussed in detail in this work.

We report results on the decay $B^{-}\to D_{\mathrm{CP}}{K}^{-}$ and its charge conjugate using a data sample of $85.4\times {10}^6$ $B\overline{B}$ pairs recorded at the ${\rm Y}\mathrm{}\left(4S\right)\mathrm{}$ resonance with the Belle detector at the KEKB asymmetric $e^{+}{e}^{-}$ storage ring. Ratios of branching fractions of Cabibbo-suppressed to Cabibbo-favored processes are determined to be $\mathcal{B}{(B}^{-}\to D^0{K}^{-})/\mathcal{B}{(B}^{-}\to D^0{\pi }^{-})=0.077\mathrm{}\pm 0.005\left(\mathrm{stat}\right)\pm 0.006\left(\mathrm{syst}\right),$ $\mathcal{B}{(B}^{-}\to D_1{K}^{-})/\mathcal{B}{(B}^{-}\to D_1{\pi }^{-})=0.093\mathrm{}\pm 0.018\left(\mathrm{stat}\right)\pm 0.008\left(\mathrm{syst}\right)$ and $\mathcal{B}{(B}^{-}\to D_2{K}^{-})/\mathcal{B}{(B}^{-}\to D_2{\pi }^{-})=0.108\mathrm{}\pm 0.019\left(\mathrm{stat}\right)\pm 0.007\left(\mathrm{syst}\right)$ where the indices 1 and 2 represent the $CP=+1\mathrm{}$ and $CP=-1$ eigenstates of the $D^0-D^0$ system, respectively. We find the partial-rate charge asymmetries for $B^{-}\to D_{\mathrm{CP}}{K}^{-}$ to be ${\mathcal{A}}_1=0.06\mathrm{}\pm 0.19\left(\mathrm{stat}\right)\pm 0.04\left(\mathrm{syst}\right)$ and ${\mathcal{A}}_2=-0.19\pm 0.17\left(\mathrm{stat}\right)\pm 0.05\left(\mathrm{syst}\right).\mathrm{}$

Spontaneous symmetry breaking in noncommutative cutoff $\lambda {\Phi }^4$ theory has been analyzed by using the formalism of the effective action for composite operators in the Hartree-Fock approximation. It turns out that there is no phase transition to a constant vacuum expectation of the field and the broken phase corresponds to a nonuniform background. By considering $〈\phi \mathrm{}\left(x\right)\mathrm{}〉=A\cos \left(\overrightarrow{Q}\cdot \overrightarrow{x}\right)$ the generated mass gap depends on the angles among the momenta $\overrightarrow{k}$ and $\overrightarrow{Q}$ and the noncommutativity parameter $\overrightarrow{\theta }.$ The order of the transition is not easily determinable in our approximation.

Quantum gauge theory on anti–de Sitter space is studied. The quantum Killing metric and the quadratic quantum Casimir operator are defined. The quantum metrics on the quantum AdS group and the linear transformations leading to them, for both $|q|=1\mathrm{}$ and q real, are found explicitly. The quantum Chern-Simons model and its quantum gauge invariance are discussed.

The gravitational collapse of a high-density null charged matter fluid, satisfying the Hagedorn equation of state, is considered in the framework of the Vaidya geometry. The general solution of the gravitational field equations can be obtained in an exact parametric form. The conditions for the formation of a naked singularity, as a result of the collapse of the compact object, are also investigated. For an appropriate choice of the arbitrary integration functions the null radial outgoing geodesic, originating from the shell focussing central singularity, admits one or more positive roots. Hence a collapsing Hagedorn fluid could end either as a black hole, or as a naked singularity. A possible astrophysical application of the model, to describe the energy source of gamma-ray bursts, is also considered.

We derive the cross section of neutrino-nucleon scatterings in supernova magnetic fields, including weak-magnetism and recoil corrections. Since the weak interaction violates parity, the scattering cross section depends asymmetrically on the directions of the neutrino momenta with respect to the magnetic field; the origin of pulsar kicks may be explained by the mechanism. An asymmetric neutrino emission (a drift flux) due to neutrino-nucleon scattering is absent at the leading level of $O({\mu }_{B}B/T),$ where ${\mu }_B$ is the nucleon magneton, B is the magnetic field strength, and T is the matter temperature at a neutrino sphere. This is because at this level the drift flux of the neutrinos is exactly canceled by that of the antineutrinos. Hence, the relevant asymmetry in the neutrino emission is suppressed by a much smaller coefficient of $O({\mu }_{B}B/m),$ where m is the nucleon mass; a detailed form of the relevant drift flux is also derived from the scattering cross section, using a simple diffusion approximation. It appears that the asymmetric neutrino emission is too small to induce the observed pulsar kicks. However, we note the fact that the drift flux is proportional to the deviation of the neutrino distribution function from the value of thermal equilibrium at the neutrino sphere. Since the deviation can be large for nonelectron neutrinos, it is expected that there occurs a cancellation between the deviation and the small suppression factor of $O({\mu }_{B}B/m).\mathrm{}$ Using a simple parametrization, we show that the drift flux due to neutrino-nucleon scattering may be comparable to the leading term due to beta processes with nucleons, which has been estimated to give a relevant kick velocity when the magnetic field is as strong as ${10}^{15}–{10}^{16}\mathrm{G}.$

We study the fermionic zero modes of BPS semilocal magnetic vortices in $N=2\mathrm{}$ supersymmetric QED with a Fayet-Iliopoulos term and two matter hypermultiplets of opposite charge. There is a one-parameter family of vortices with arbitrarily wide magnetic cores. Contrary to the situation in pure Nielsen-Olesen vortices, new zero modes are found which get their masses from Yukawa couplings to scalar fields that do not wind and are nonzero at the core. We clarify the relation between fermion mass and zero modes. The new zero modes have opposite chiralities and therefore do not affect the net counting (left minus right) of zero modes coming from index theorems but do manage to evade other index theorems in the literature that count the total number (left plus right) of zero modes in simpler systems.

An exact solution of the domain wall junction is obtained in $\mathcal{N}=2\mathrm{}$ supersymmetric (SUSY) QED with three massive hypermultiplets. The junction preserves two out of eight SUSYs. Both a (magnetic) Fayet-Iliopoulos term and complex masses for hypermultiplets are needed to obtain the junction solution. There are zero modes corresponding to the spontaneously broken translation, SUSY, and $U\left(1\right).$ All broken and unbroken SUSY charges are explicitly worked out in the Wess-Zumino gauge in $\mathcal{N}=1\mathrm{}$ superfields as well as in components. The relation to models in five dimensions is also clarified.

Closed string tachyon condensation in spacetime generates potentials on the worldsheet that model two-dimensional inflationary cosmology. These models illustrate and elucidate a variety of aspects of inflation, in particular the generation of quantum fluctuations and their back reaction on geometry. We exhibit a class of Liouville gravity models coupled to matter that can exhibit, for example, (a) pure de Sitter gravity, (b) slow-roll inflation, (c) topological inflation, and (d) graceful exit into a Friedmann-Robertson-Walker (FRW) phase. The models also provide a quantitative testing ground for ideas about the origin of inflation, such as the various “no-boundary or tunnelling” proposals, and the “eternal or chaotic” inflationary scenario. We suggest an alternative mechanism for quantum creation of cosmological spacetimes which, in the context of the model, provides a natural explanation for why the typical FRW cosmology at large scales underwent a period of inflation at small scale.

The scalar spectral index n is an important parameter describing the nature of primordial density perturbations. Recent data, including those from the Wilkinson Microwave Anisotropy Probe satellite, show some evidence that the index runs (changes as a function of the scale k at which it is measured) from $n>\mathrm{}1\mathrm{}$ (blue) on long scales to $n<\mathrm{}1\mathrm{}$ (red) on short scales. We investigate the extent to which inflationary models can accommodate such significant running of n. We present several methods for constructing large classes of potentials which yield a running spectral index. We show that within the slow-roll approximation, the fact that $n-1$ changes sign from blue to red forces the slope of the potential to reach a minimum at a similar field location. We also briefly survey the running of the index in a wider class of inflationary models, including a subset of those with nonminimal kinetic terms.

The magnetic moment $\mu$ of the $\rho$ meson is studied in QCD light cone sum rules, and it is found that $\mu =(2.3\mathrm{}\pm 0.5),$ in units of ${e/2m}_{\rho }.$ A comparison of our result on the magnetic moment of the $\rho$ meson with the predictions of the other approaches is presented.

This paper describes unification of the Higgs doublet in the standard model and the Higgs field to break the grand unified theory group to stabilize the sliding singlet mechanism which can solve the doublet-triplet splitting problem. This attractive mechanism has been generalized to apply it to many unified scenarios. This research attempts to build various concrete $E_6$ unified models by using the generalized sliding singlet mechanism.

A direct connection can be made between mixing angles in negative parity baryons and the spin coupling of constituent quarks. The mixing angles do not depend on spectral data. These angles are recalculated for gluon exchange and pion exchange between quarks. The mixing determined for pion exchange is in disagreement with a calculation in the literature [Phys. Rep. 268, 263 (1996)], but consistent with the results of another calculation [Phys. Rev. C 65, 045209 (2002)] and with experiment. The experimental data on mixing are very similar to those derived from gluon exchange but substantially different from the values obtained for pion exchange. A preliminary estimate of spin orbit forces is found to give only small changes in these angles.

We stress the point that massive neutrinos may be Majorana particles even if the effective mass of the neutrinoless double beta decay $〈m{〉}_{\mathrm{ee}}$ vanishes. We show that current neutrino oscillation data do allow $〈m{〉}_{\mathrm{ee}}=0\mathrm{}$ to hold, if the Majorana CP-violating phases lie in two specific regions. Strong constraints on the neutrino mass spectrum can then be obtained. A possible texture of the neutrino mass matrix is also illustrated under the $〈m{〉}_{\mathrm{ee}}=0\mathrm{}$ condition.

In this paper, we discuss how thermal fluctuations can effect the stability of charged black holes when close to certain critical points. Our novel treatment utilizes the black hole area spectrum (taken to be evenly spaced) and makes an important distinction between fixed and fluctuating charge systems. The discussion begins with a summary of a recent technical paper. We then go on to consider the issue of stability when the system approaches the critical points of interest. These include the Hawking-Page phase transition, a transition that is relevant to Reissner-Nordström black holes and various extremal-limiting cases.

The equations of motion and boundary conditions for the fluctuations around a classical open string, in a curved space-time with torsion, are considered in compact and world-sheet covariant form. The rigidly rotating open strings in anti–de Sitter space with and without torsion are investigated in detail. By carefully analyzing the tangential fluctuations at the boundary, we show explicitly that the physical fluctuations (which at the boundary are combinations of normal and tangential fluctuations) are finite, even though the world-sheet is singular there. The divergent 2-curvature thus seems less dangerous than expected in these cases. The general formalism can be straightforwardly used also to study the (bosonic part of the) fluctuations around the closed strings, recently considered in connection with the AdS/conformal field theory duality, on ${\mathrm{AdS}}_5\times {\mathrm{S}}^5$ and ${\mathrm{AdS}}_3\times {\mathrm{S}}^3\times {\mathrm{T}}^4.$