Charmless $B$ decay modes $B\to \pi \pi ,\pi K$ and $KK$ are systematically investigated with and without flavor SU(3) symmetry. Independent analyses on $\pi \pi$ and $\pi K$ modes both favor a large ratio between color-suppressed tree ($C$) and tree $(T)$ diagram, which suggests that they are more likely to originate from long distance effects. The sizes of QCD penguin diagrams extracted individually from $\pi \pi$, $\pi K$ and $KK$ modes are found to follow a pattern of SU(3) breaking in agreement with the naive factorization estimates. Global fits to these modes are done under various scenarios of SU(3) relations. The results show good determinations of weak phase $\gamma$ in consistency with the standard model (SM), but a large electroweak penguin $(P_{\mathrm{EW}})$ relative to $T+C$ with a large relative strong phase is favored, which requires a big enhancement of color-suppressed electroweak penguin ($P_{\mathrm{EW}}^C$) compatible in size but destructively interfering with $P_{\mathrm{EW}}$ within the SM, or implies new physics. The possibilities of sizable contributions from nonfactorizable diagrams such as $W$ exchange ($E$), annihilation ($A$), and penguin-annihilation diagrams ($P_A$) are investigated. The implications to the branching ratios and $CP$ violations in $KK$ modes are discussed.

We study the ${\Lambda }_{\mathrm{QCD}}/M_B$ corrections from subleading shape functions in inclusive $B$-meson decays. We propose a natural and smooth interpolation from the endpoint region to the full phase space, and derive expressions for the triple differential decay rate in $B\to X_u\ell {\overline{\nu }}_{\ell }$ and the photon energy spectrum in $B\to X_s\gamma$. Our results are valid to order ${\Lambda }_{\mathrm{QCD}}/M_B$ for hadronic invariant masses of order ${\Lambda }_{\mathrm{QCD}}{M}_B$ and to order ${\Lambda }_{\mathrm{QCD}}^2/M_B^2$ for larger hadronic masses. They allow a systematic investigation of the transition between the separate regimes of the local and nonlocal expansions, and can be used to study decay distributions in any kinematic variables. We consider several examples of interest and point out that a combined measurement of hadronic energy and invariant mass provides an alternative to the extraction of $|V_{ub}|$ which is largely independent of shape-function effects and in principle allows a higher accuracy than the combined measurement of leptonic and hadronic invariant masses. We perform the expansion directly in QCD light-cone operators, and give a discussion of the general basis of light-cone operators. Reparametrization invariance under the change of the light-cone direction reduces the number of independent shape functions. We show that differing previous results for the lepton energy spectrum obtained from different choices of light-cone coordinates are in agreement.

We derive analytic expressions for high energy $2\to 2$ off-shell scattering amplitudes of weak vector bosons. They are obtained from six-fermion final states in processes of the type $e^{+}{e}^{-}\to {\overline{\nu }}_e+(WW)+{\nu }_e\to {\overline{\nu }}_e+(l\nu )(l\nu )+{\nu }_e$. As an application we reconsider the unitarity bounds on the Higgs mass. Particular attention is given to the role of the photon exchange which has not been considered in earlier investigations; we find that the photon weakens the bound of the Higgs mass.

The total lowest-order electromagnetic radiative corrections to the observables in Møller scattering of longitudinally polarized electrons have been calculated. The final expressions obtained by the covariant method for the infrared divergency cancellation are free from any unphysical cut-off parameters. Since the calculation is carried out within the ultrarelativistic approximation our result has a compact form that is convenient for computing. Basing on these expressions the FORTRAN code MERA has been developed. Using this code the detailed numerical analysis performed under SLAC (E-158) and JLab kinematic conditions has shown that the radiative corrections are significant and rather sensitive to the value of the missing mass (inelasticity) cuts.

We develop a detailed analysis of synchrotron radiation in the effective Lorentz invariance violating (LIV) model of Myers-Pospelov, considering explicitly both the dynamics of the charge producing the radiation and the dynamics of the electromagnetic field itself. Within the radiation approximation we compute exact expressions in the LIV parameters for the electric and magnetic fields, the angular distribution of the power spectrum, the total emitted power in the $m$th harmonic and the polarization. We also perform expansions of the exact results in terms of the LIV parameters to identify the dominant effects and study the main features of the high energy limit of the spectrum. A very interesting consequence is the appearance of rather unexpected and large amplifying factors associated with the LIV effects, which go along with the usual contributions of the expansion parameter. This opens up the possibility of looking for astrophysical sources where these amplifying factors are important to further explore the constraints imposed upon the LIV parameters by synchrotron radiation measurements. We briefly sketch some phenomenological applications in the case of supernova remnants and gamma ray bursts.

Simple scalar field cosmological models are considered describing gravity assisted crossing of the phantom divide line. This crossing or (de)-phantomization characterized by the change of the sign of the kinetic term of the scalar field is smooth and driven dynamically by the Einstein equations. Different cosmological scenarios, including the phantom phase of matter are sketched.

We investigate the role of exclusive channels in semi-inclusive electroproduction of pions and kaons. Using the QCD factorization theorem for hard exclusive processes we evaluate the cross sections for exclusive pseudoscalar and vector meson production in terms of generalized parton distributions and meson distribution amplitudes. We investigate the uncertainties arising from the modeling of the nonperturbative input quantities. Combining these results with available experimental data, we compare the cross sections for exclusive channels to that obtained from quark fragmentation in semi-inclusive deep inelastic scattering. We find that ${\rho }^0$ production is the only exclusive channel with significant contributions to semi-inclusive pion production at large $z$ and moderate $Q^2$. The corresponding contribution to kaon production from the decay of exclusively produced $\varphi$ and $K^{*}$ is rather small.

The breaking of conventional linear $k_{\perp }$ factorization for hard processes in a nuclear environment is by now well established. Here we report a detailed derivation of the nonlinear $k_{\perp }$-factorization relations for the production of quark-gluon dijets. This process is the dominant source of dijets in the proton hemisphere of proton-nucleus collisions at energies of the relativistic heavy ion collider (RHIC). The major technical problem is a consistent description of the non-Abelian intranuclear evolution of multiparton systems of color dipoles. Following the technique developed in our early work [N. N. Nikolaev, W. Schäfer, B. G. Zakharov, and V. R. Zoller, J. Exp. Theor. Phys. 97, 441 (2003)], we reduce the description of the intranuclear evolution of the $qgg\overline{q}$ state to the $3\times 3$ system of coupled equations in the space of color-singlet 4-parton states $|3\overline{3}⟩$, $|6\overline{6}⟩$, and $|15\overline{15}⟩$ (and their large-$N_c$ generalizations). At large number of colors $N_c$, the eigenstate $(|6\overline{6}⟩-|15\overline{15}⟩)/\sqrt{2}$ decouples from the initial state $|3\overline{3}⟩$. The resulting nuclear distortions of the dijet spectrum exhibit much similarity to those found earlier for forward dijets in deep inelastic scattering. Still there are certain distinctions regarding the contribution from color-triplet $qg$ final states and from coherent diffraction excitation of dijets. To the large-$N_c$ approximation, we identify four universality classes of nonlinear $k_{\perp }$ factorization for hard dijet production.

We present the calculations of the complete next-to-leading order (NLO) QCD corrections (including supersymmetric QCD) to the inclusive total cross sections of the associated production processes $pp\to A^0{Z}^0+X$ in the minimal supersymmetric standard model at the CERN Large Hadron Collider. Both the dimensional regularization scheme and the dimensional reduction scheme are used to organize the calculations, which yield the same NLO rates. The NLO correction can either enhance or reduce the total cross sections, but it generally efficiently reduces the dependence of the total cross sections on the renormalization/factorization scale. We also examine the uncertainty of the total cross sections due to the parton distribution function uncertainties.

The newly reported Y(4260) becomes the second most massive state in the charmonium family. We argue that it displaces the $\psi (4415)$ as the (largely) $4s$ vector charmonium state, recall $s-d$ wave interference to explain the lack of a signal in $e^{-}{e}^{+}\to \mathrm{hadrons}$ and suggest some further study avenues that can exclude exotic meson assignments. The absence of a $J/\psi KK$ mode can be understood, beyond phase space suppression, to be a consequence of chiral symmetry. We also provide a model calculation in this sector showing that, although forcing the fit somewhat (which suggests a small sea quark wave function component), the state can be incorporated in a standard scheme.

In $e^{+}{e}^{-}$ collisions recorded using the CLEO II.V detector we have studied the Cabibbo suppressed decay of $D^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ with the initial flavor of the $D^0$ tagged by the decay $D^{*+}\to D^0{\pi }^{+}$. We use the Dalitz-plot analysis technique to measure the resonant substructure in this final state and observe $\rho \pi$ and nonresonant contributions by fitting for their amplitudes and relative phases. We describe the $\pi \pi$ $S$ wave with a $K$-matrix formalism and limit this contribution to the rate to be $<2.5\%@95\%$ confidence level, in contrast to the large rate observed in $D^{+}\to {\pi }^{+}{\pi }^{-}{\pi }^{+}$ decay. Using the amplitudes and phases from this analysis, we calculate an integrated $CP$ asymmetry of ${0.01}_{-0.07}^{+0.09}\pm 0.05$.

We study the symmetry breaking pattern of an $O(4)$ symmetric model of scalar fields, with both charged and neutral fields, interacting with a photon bath. Nagasawa and Brandenberger argued that in favorable circumstances the vacuum manifold would be reduced from $S^3$ to $S^1$. Here it is shown that a selective condensation of the neutral fields, that are not directly coupled to photons, can be achieved in the presence of a minimal external dissipation, i.e. not related to interactions with a bath. This should be relevant in the early universe or in heavy-ion collisions where dissipation occurs due to expansion.

We present a toy model that exhibits clash-of-symmetries style Higgs field kink configurations in a Randall-Sundrum-like spacetime. The model has two complex scalar fields ${\Phi }_{1,2}$, with a sextic potential obeying global $\mathrm{U}(1)\otimes \mathrm{U}(1)$ and discrete ${\Phi }_1\leftrightarrow {\Phi }_2$ interchange symmetries. The scalar fields are coupled to $4+1$ dimensional gravity endowed with a bulk cosmological constant. We show that the coupled Einstein-Higgs field equations have an interesting analytic solution provided the sextic potential adopts a particular form. The $4+1$ metric is shown to be that of a smoothed-out Randall-Sundrum type of spacetime. The thin-brane Randall-Sundrum limit, whereby the Higgs field kinks become step functions, is carefully defined in terms of the fundamental parameters in the action. The “clash-of-symmetries” feature, defined in previous papers, is manifested here through the fact that both of the U(1) symmetries are spontaneously broken at all nonasymptotic points in the extra dimension $w$. One of the U(1)’s is asymptotically restored as $w\to -\infty$, with the other U(1) restored as $w\to +\infty$. The spontaneously broken discrete symmetry ensures topological stability. In the gauged version of this model we find new flat-space solutions, but in the warped metric case we have been unable to find any solutions with nonzero gauge fields.

Recently, a global phenomenological fit to high energy data has included charge symmetry breaking terms, leading to limits on the allowed magnitude of such effects. We discuss two possible experiments that could search for isospin violation in valence parton distributions. We show that, given the magnitude of charge symmetry violation consistent with existing global data, such experiments might expect to see effects at a level of several percent. Alternatively, such experiments could significantly decrease the upper limits on isospin violation in parton distributions.

We calculate squared helicity amplitudes for nondiagonal and mixed squark pair production at hadron colliders, taking into account not only loop-induced QCD diagrams, but also previously unconsidered electroweak channels, which turn out to be dominant. Mixing effects are included for both top and bottom squarks. Numerical results are presented for several SUSY benchmark scenarios at both the CERN LHC and the Fermilab Tevatron, including the possibilities of light stops or sbottoms. The latter should be easily observed at the Tevatron in associated production of stops and sbottoms for a large range of stop masses and almost independently of the stop mixing angle. Asymmetry measurements for light stops at the polarized BNL Relativistic Heavy Ion Collider are also briefly discussed.

Expected event rates for a number of dark matter nuclear targets were calculated in the effective low-energy minimal supersymmetric standard model, provided the lightest neutralino is the dark matter Weakly Interacting Massive Particle (WIMP). These calculations allow direct comparison of sensitivities of different dark matter detectors to intermediate mass WIMPs expected from the measurements of the DArk MAtter (DAMA) experiment.

The double-lepton polarization asymmetries in $B\to \rho {\ell }^{+}{\ell }^{-}$ decay are analyzed in a model independent framework. The general expressions for nine double-polarization asymmetries are calculated. It is shown that the study of the double-lepton polarization asymmetries proves to be a very useful tool in looking for new physics beyond the standard model.

We study weighted azimuthal single spin asymmetries in hadron-hadron scattering using the diagrammatic approach at leading order and assuming factorization. The effects of the intrinsic transverse momenta of the partons are taken into account. We show that the way in which $T$-odd functions, such as the Sivers function, appear in these processes does not merely involve a sign flip when compared with semi-inclusive deep inelastic scattering, such as in the case of the Drell-Yan process. Expressions for the weighted scattering cross sections in terms of distribution and fragmentation functions folded with hard cross sections are obtained by introducing modified hard cross sections, referred to as gluonic-pole cross sections.

Geo-neutrino detection can determine the amount of long-lived radioactive elements within our planet, thus providing a direct test of the bulk silicate Earth (BSE) model and fixing the radiogenic contribution to the terrestrial heat. We present a prediction for the geo-neutrino signal at KamLAND as a function of the uranium mass in the Earth. The prediction is based on global mass balance, supplemented by a detailed geochemical and geophysical study of the region near the detector. The prediction is weakly dependent on mantle modeling. If BSE is correct, uranium geo-neutrinos will produce between 25 and 35 events per year and ${10}^{32}$ protons at Kamioka.

We discuss to what extent future precision measurements of neutrino mixing observables will influence the information we can draw from a measurement of (or an improved limit on) neutrinoless double beta decay. Whereas the $\Delta m^2$ corresponding to solar and atmospheric neutrino oscillations are expected to be known with good precision, the parameter ${\theta }_{12}$ will govern a large part of the uncertainty. We focus, in particular, on the possibility of distinguishing the neutrino mass hierarchies and on setting a limit on the neutrino mass. We give the largest allowed values of the neutrino masses which allow to distinguish the normal from the inverted hierarchy. All aspects are discussed as a function of the uncertainty stemming from the involved nuclear matrix elements. The implications of a vanishing, or extremely small, effective mass are also investigated. By giving a large list of possible neutrino mass matrices and their predictions for the observables, we finally explore how a measurement of (or an improved limit on) neutrinoless double beta decay can help to identify the neutrino mass matrix if more precise values of the relevant parameters are known.