In this work we show that the physics reach of a long-baseline (LBL) neutrino oscillation experiment based on a superbeam and a megaton water Cherenkov detector can be significantly increased if the LBL data are combined with data from atmospheric neutrinos (ATM) provided by the same detector. ATM data are sensitive to the octant of ${\theta }_{23}$ and to the type of the neutrino mass hierarchy, mainly through three-flavor effects in $e$-like events. This allows to resolve the so-called ${\theta }_{23}$- and $\mathrm{sign}(\Delta m_{31}^2)$-parameter degeneracies in LBL data. As a consequence it becomes possible to distinguish the normal from the inverted neutrino mass ordering at $2\sigma$ C.L. from a combined $\mathrm{LBL}+\mathrm{ATM}$ analysis if ${sin}^{2}2{\theta }_{13}\gtrsim 0.02$. The potential to identify the true values of ${sin}^{2}2{\theta }_{13}$ and the CP-phase ${\delta }_{\mathrm{CP}}$ is significantly increased through the lifting of the degeneracies. These claims are supported by a detailed simulation of the T2K (phase II) LBL experiment combined with a full three-flavor analysis of ATM data in the HyperKamiokande detector.

We present a measurement of the $t\overline{t}$ production cross section using events with one charged lepton and jets from $p\overline{p}$ collisions at a center-of-mass energy of 1.96 TeV. In these events, heavy flavor quarks from top quark decay are identified with a secondary vertex tagging algorithm. From $162\mathrm{p}{\mathrm{b}}^{-1}$ of data collected by the Collider Detector at Fermilab, a total of 48 candidate events are selected, where $13.5\pm 1.8$ events are expected from background contributions. We measure a $t\overline{t}$ production cross section of ${5.6}_{-1.1}^{+1.2}(\mathrm{stat}.{)}_{-0.6}^{+0.9}(\mathrm{syst}.)\mathrm{pb}$.

Starting from the QCD Lagrangian and the surface tension of QCD bubbles we derive the critical size of bubbles, the nucleation probability and the nucleation site separation distance.

It has recently been observed that the weakly coupled plane-wave matrix model has a density of states which grows exponentially at high energy. This implies that the model has a phase transition. The transition appears to be of first order. However, its exact nature is sensitive to interactions. In this paper, we analyze the effect of interactions by computing the relevant parts of the effective potential for the Polyakov loop operator in the finite temperature plane-wave matrix model to three-loop order. We show that the phase transition is indeed of first order. We also compute the correction to the Hagedorn temperature to order two loops.

We study the alpha vacua of de Sitter space by considering the decay rate of the inflaton field coupled to a scalar field placed in an alpha vacuum. We find an alpha dependent Bose enhancement relative to the Bunch-Davies vacuum and, surprisingly, no nonrenormalizable divergences. We also consider a modified alpha dependent time-ordering prescription for the Feynman propagator and show that it leads to an alpha independent result. This result suggests that it may be possible to calculate in any alpha vacuum if we employ the appropriate causality preserving prescription.

We fully determine a uniformly valid asymptotic behavior for large, real $a\omega$ and fixed $m$ of the angular solutions and eigenvalues of the spin-weighted spheroidal differential equation, which arises from the separation of the Teukolsky equation in Kerr space-time. We complement the analytic work with a numerical study.

Present cosmological data are well explained assuming purely adiabatic perturbations, but an admixture of isocurvature perturbations is also permitted. We use a Bayesian framework to compare the performance of cosmological models including isocurvature modes with the purely adiabatic case; this framework automatically and consistently penalizes models which use more parameters to fit the data. We compute the Bayesian evidence for fits to a data set comprised of WMAP and other microwave anisotropy data, the galaxy power spectrum from 2dFGRS and SDSS, and Type Ia supernovae luminosity distances. We find that Bayesian model selection favors the purely adiabatic models, but so far only at low significance.

The polarization of the cosmic microwave background (CMB) is widely recognized as a potential source of information about primordial gravitational waves. The gravitational wave contribution can be separated from the dominant CMB polarization created by density perturbations at the times of recombination and reionization because it generates both $E$ and $B$ polarization modes, whereas the density perturbations create only $E$ polarization. The limits of our ability to measure gravitational waves are thus determined by statistical and systematic errors from CMB experiments, foregrounds, and nonlinear evolution effects such as gravitational lensing of the CMB. Usually it is assumed that most foregrounds can be removed because of their frequency dependence, however Thomson scattering of the CMB quadrupole by electrons in the Galaxy or nearby structures shares the blackbody frequency dependence of the CMB. If the optical depth from these nearby electrons is anisotropic, the polarization generated can include $B$ modes even if no tensor perturbations are present. We estimate this effect for the Galactic disk and nearby extragalactic structures, and find that it contributes to the $B$ polarization at the level of $\sim (1–2)\times {10}^{-4}\mu \mathrm{K}$ per logarithmic interval in multipole $\ell$ for $\ell <30$. This is well below the detectability level even for a future CMB polarization satellite and hence is negligible. Depending on its structure and extent, the Galactic corona may be a source of $B$-modes comparable to the residual large-scale lensing $B$-mode after the latter has been cleaned using lensing reconstruction techniques. For an extremely ambitious post-Planck CMB experiment, Thomson scattering in the Galactic corona is thus a potential contaminant of the gravitational wave signal; conversely, if the other foregrounds can be cleaned out, such an experiment might be able to constrain models of the corona.

Theoretical predictions for the production cross sections of leptoquarks at the CERN LHC are presented including higher-order QCD corrections. These corrections reduce the dependence on the renormalization/factorization scales significantly. Moreover, they are required to exploit the leptoquark mass reach of the LHC experiments. In this sequel to an earlier analysis performed for the Tevatron collider we extend the leptoquark analysis to the LHC energy.

We analyze two-loop gluino corrections to the neutron electric dipole moment (EDM) in the minimal supersymmetry extension of the standard model (MSSM). The dependence of two-loop corrections on the relevant CP violating phases differs from that of the one-loop contributions, and there is a region in the parameter space where the two-loop contributions are comparable with the one-loop contributions. Our numerical results show that the two-loop corrections can be as large as $30\%$ of the one-loop results.

We present a new method for the experimental determination of the top quark mass that is based upon the mean distance of travel of $b$ hadrons in top quark events. The dominant systematic uncertainties of this method are not correlated with those of other methods, but a large number of events is required to achieve small statistical uncertainty. Large $t\overline{t}$ event samples are expected from Run II of the Fermilab Tevatron and the CERN Large Hadron Collider (LHC). We show that by the end of Run II, a single experiment at the Tevatron could achieve a top quark mass uncertainty of $\sim 5\mathrm{GeV}/c^2$ by this method alone. At the CERN LHC, this method could be comparable to all other methods, which are expected to achieve an uncertainty of $\sim 1.5\mathrm{GeV}/c^2$ per experiment. This new method would provide a useful cross-check to other methods and could be combined with them to obtain a substantially reduced overall uncertainty.

We use dimensional regularization to calculate the $\mathcal{O}({\epsilon }^2)$ expansion of all scalar one-loop one-, two-, three-, and four-point integrals that are needed in the calculation of hadronic heavy quark production. The Laurent series up to $\mathcal{O}({\epsilon }^2)$ is needed as input to that part of the next-to-next-to-leading order corrections to heavy flavor production at hadron colliders where the one-loop integrals appear in the loop-by-loop contributions. The four-point integrals are the most complicated. The $\mathcal{O}({\epsilon }^2)$ expansion of the three- and four-point integrals contains in general polylogarithms up to ${\mathrm{Li}}_4$ and functions related to multiple polylogarithms of maximal weight and depth four.

The ratio of nuclear modification factors of high-$p_T$ heavy-flavored mesons to light-flavored hadrons (“heavy-to-light ratio”) in nucleus-nucleus collisions tests the partonic mechanism expected to underlie jet quenching. Heavy-to-light ratios are mainly sensitive to the mass and color-charge dependences of medium-induced parton energy loss. Here, we assess the potential for identifying these two effects in $D$ and $B$ meson production at RHIC and at the LHC. To this end, we supplement the perturbative QCD factorized formalism for leading hadron production with radiative parton energy loss. For $D$ meson spectra at high but experimentally accessible transverse momentum ($10\lesssim p_T\lesssim 20\mathrm{GeV}$) in Pb-Pb collisions at the LHC, we find that charm quarks behave essentially like light quarks. However, since light-flavored hadron yields are dominated by gluon parents, the heavy-to-light ratio of $D$ mesons is a sensitive probe of the color-charge dependence of parton energy loss. In contrast, due to the larger $b$ quark mass, the medium modification of $B$ mesons in the same kinematical regime provides a sensitive test of the mass dependence of parton energy loss. At RHIC energies, the strategies for identifying and disentangling the color charge and mass dependence of parton energy loss are more involved because of the smaller kinematical range accessible. We argue that at RHIC, the kinematical regime best suited for such an analysis of $D$ mesons is $7\lesssim p_T\lesssim 12\mathrm{GeV}$, whereas the study of lower transverse momenta is further complicated due to the known dominant contribution of additional, particle species dependent, nonperturbative effects.

A discussion of the modification of the phase-space commutators in a quantum mechanical relativistic theory with an invariant length scale (DSR) is presented. Two examples are discussed where a classical behavior is approached in one case when the energy approaches the inverse of the invariant length which appears as a cutoff in the energy and in the second case when the mass is much larger than the inverse of the invariant length.

We study conditions for the existence of asymptotic observables in cosmology. With the exception of de Sitter space, the thermal properties of accelerating universes permit arbitrarily long observations, and guarantee the production of accessible states of arbitrarily large entropy. This suggests that some asymptotic observables may exist, despite the presence of an event horizon. Comparison with decelerating universes shows surprising similarities: Neither type suffers from the limitations encountered in de Sitter space, such as thermalization and boundedness of entropy. However, we argue that no realistic cosmology permits the global observations associated with an $\mathrm{S}$ matrix.

The evolution of the quintessence field during a phase of chaotic inflation is studied. The inflaton $\varphi$ and the quintesssence field $Q$ are described in a supergravity framework where the coupling between the inflaton and quintessence is induced by nonrenormalizable operators suppressed by the Planck mass. We show that the resulting quintessence potential during inflation possesses a time-dependent minimum playing the role of an attractor. The presence of this attractor forces the quintessence field to be small during inflation. These initial conditions are such that the quintessence field is on track now.

We compute the radiative corrections to the mass of a test boson field in an inflating spacetime. The calculations are carried out in case of a boson part of a supersymmetric chiral multiplet. We show that its mass is preserved up to logarithmic divergences both in ultraviolet and infrared domains. Consequences of these results for inflationary models are discussed.

Detection of gamma rays from dark matter annihilation in the galactic center is one of the feasible techniques to search for dark matter. We evaluate the gamma-ray flux in the case that the dark matter has an electroweak $\mathrm{S}\mathrm{U}(2{)}_L$ charge. Such dark matter is realized in the minimal supersymmetric standard model (MSSM) when the lightest SUSY particle is the Higgsino- or Wino-like neutralino. When the dark matter is heavy compared to the weak gauge bosons, the leading-order calculation of the annihilation cross sections in perturbation breaks down due to a threshold singularity. We take into account nonperturbative effects by using the nonrelativistic effective theory for the two-body states of the dark matter and its $\mathrm{S}\mathrm{U}(2{)}_L$ partner(s), and evaluate precise cross sections relevant to the gamma-ray fluxes. We find that the annihilation cross sections may be enhanced by several orders of magnitude due to resonances when the dark matter mass is larger than 1 TeV. Furthermore, the annihilation cross sections in the MSSM may be changed by factors even when the mass is about 500 GeV. We also discuss sensitivities to gamma-ray signals from the galactic center in the GLAST satellite detector and the large Air Cerenkov Telescope arrays.

One of the robust features found in simulations of core-collapse supernovae (SNe) is the prompt neutronization burst, i.e., the first $\sim 25$ milliseconds after bounce when the SN emits with very high luminosity mainly ${\nu }_e$ neutrinos. We examine the dependence of this burst on variations in the input of current SN models and find that recent improvements of the electron capture rates as well as uncertainties in the nuclear equation of state or a variation of the progenitor mass have only little effect on the signature of the neutronization peak in a megaton water Cherenkov detector for different neutrino mixing schemes. We show that exploiting the time structure of the neutronization peak allows one to identify the case of a normal mass hierarchy and large 13-mixing angle ${\vartheta }_{13}$, where the peak is absent. The robustness of the predicted total event number in the neutronization burst makes a measurement of the distance to the SN feasible with a precision of about 5%, even in the likely case that the SN is optically obscured.