We study the transition of a heavy quark pair from octet to singlet color configurations at next-to-next-to-leading order in heavy quarkonium production. We show that the infrared singularities in this process are consistent with nonrelativistic QCD factorization to all orders in the heavy quark relative velocity $v$. This factorization requires the gauge-completed matrix elements that we introduced previously to prove next-to-next-to-leading-order factorization to order $v^2$.

Using a new result for the first moment of the hadronic production cross section at order $\mathcal{O}({\alpha }_s^3)$, and new data on the $J/\psi$ and ${\psi }^{\prime }$ resonances for the charm quark, we determine the $\overline{\mathrm{MS}}$ masses of the charm and bottom quarks to be ${\overline{m}}_c({\overline{m}}_c)=1.295\pm 0.015\mathrm{GeV}$ and ${\overline{m}}_b({\overline{m}}_b)=4.205\pm 0.058\mathrm{GeV}$. We assume that the continuum contribution to the sum rules is adequately described by pQCD. While we observe a large reduction of the perturbative error, the shifts induced by the theoretical input are very small. The main change in the central value of $m_c$ is related to the experimental data. On the other hand, the value of $m_b$ is not changed by our calculation to the assumed precision.

We analyze the dependence of the rates of the LFV charged-lepton decays $\mu \to e+\gamma$, $\tau \to e+\gamma$, $\tau \to \mu +\gamma$ ($l_i\to l_j+\gamma$) and their ratios, predicted in the class of SUSY theories with see-saw mechanism of $\nu$-mass generation and soft SUSY breaking with universal boundary conditions at the GUT scale, on the Majorana $CP$-violation phases in the PMNS neutrino mixing matrix and the “leptogenesis” $CP$-violating ($CP\mathrm{V}$) parameters. The case of quasidegenerate in mass heavy Majorana neutrinos is considered. The analysis is performed for normal hierarchical (NH), inverted hierarchical (IH) and quasidegenerate (QD) light neutrino mass spectra. We show, in particular, that for NH and IH $\nu$-mass spectrum and negligible lightest neutrino mass, all three $l_i\to l_j+\gamma$ decay branching ratios, $BR(l_i\to l_j+\gamma )$, depend on one Majorana phase, one leptogenesis $CP\mathrm{V}$ parameter and on the 3-neutrino oscillation parameters; if the CHOOZ mixing angle ${\theta }_{13}$ is sufficiently large, they depend on the Dirac $CP\mathrm{V}$ phase in the PMNS matrix. The “double ratios” $\mathrm{R}(21/31)\sim BR(\mu \to e+\gamma )/BR(\tau \to e+\gamma )$ and $\mathrm{R}(21/32)\sim BR(\mu \to e+\gamma )/BR(\tau \to \mu +\gamma )$ are determined by these parameters. The same Majorana phase enters into the NH and IH expressions for the effective Majorana mass in neutrinoless double beta decay, $⟨\mathrm{m}⟩$.

We analyze the potential of the CERN Large Hadron Collider (LHC) to study the structure of quartic vector-boson interactions through the pair production of electroweak gauge bosons via weak boson fusion $qq\to qqWW$. In order to study these couplings we have performed a partonic level calculation of all processes $pp\to jj{e}^{\pm }{\mu }^{\pm }\nu \nu$ and $pp\to jj{e}^{\pm }{\mu }^{\mp }\nu \nu$ at the LHC using the exact matrix elements at $\mathcal{O}({\alpha }_{\mathrm{em}}^6)$ and $\mathcal{O}({\alpha }_{\mathrm{em}}^4{\alpha }_s^2)$ as well as a full simulation of the $t\overline{t}$ plus 0 to 2 jets backgrounds. A complete calculation of the scattering amplitudes is necessary not only for a correct description of the process but also to preserve all correlations between the final-state particles which can be used to enhance the signal. Our analyses indicate that the LHC can improve by more than 1 order of magnitude the bounds arising at the present from indirect measurements.

We present measurements of ${\nu }_{\mu }$ disappearance in K2K, the KEK to Kamioka long-baseline neutrino oscillation experiment. One-hundred and twelve beam-originated neutrino events are observed in the fiducial volume of Super-Kamiokande with an expectation of ${158.1}_{-8.6}^{+9.2}$ events without oscillation. A distortion of the energy spectrum is also seen in 58 single-ring muonlike events with reconstructed energies. The probability that the observations are explained by the expectation for no neutrino oscillation is 0.0015% ($4.3\sigma$). In a two-flavor oscillation scenario, the allowed $\Delta m^2$ region at ${sin}^{2}2\theta =1$ is between 1.9 and $3.5\times {10}^{-3}{\mathrm{eV}}^2$ at the 90% C.L. with a best-fit value of $2.8\times {10}^{-3}{\mathrm{eV}}^2$.

In this paper we thermalize the type II superstrings in the GS formulation by applying the Thermo Field Dynamics formalism. The thermal boundary conditions on the thermal Hilbert space are obtained from the Bogomol’nyi-Prasad-Sommerfield $D$-brane boundary conditions at zero temperature. We show that thermal boundary states can be obtained by thermalization from the Bogomol’nyi-Prasad-Sommerfield $D$-branes at zero temperature. These new states can be interpreted as thermal $D$-branes. Next, we discuss the supersymmetry breaking of the thermal string in the Thermo Field Dynamics formalism approach. We identify the broken supersymmetry with the $ϵ$-transformation while the $\eta$-transformation is preserved. Also, we compute the thermal partition function and the entropy of the thermal string.

We express the heavy quark diffusion coefficient as the temporal variation of a Wilson line along the Schwinger-Keldysh contour. This generalizes the classical formula for diffusion as a force-force correlator to a non-Abelian theory. We use this formula to compute the diffusion coefficient in strongly coupled $\mathcal{N}=4$ Yang-Mills theory by studying the fluctuations of a string in ${\mathrm{AdS}}_5\times S_5$. The string solution spans the full Kruskal plane and gives access to contour correlations. The diffusion coefficient is $D=2/\sqrt{\lambda }\pi T$ and is therefore parametrically smaller than momentum diffusion, $\eta /(e+p)=1/4\pi T$. The quark mass must be much greater than $T\sqrt{\lambda }$ in order to treat the quark as a heavy quasiparticle. The result is discussed in the context of the Relativistic Heavy Ion Collider (RHIC) experiments.

We solve the one loop effective scalar field equations for spatial plane waves in massless, minimally coupled scalar quantum electrodynamics on a locally de Sitter background. The computation is done in two different gauges: a non-de Sitter invariant analogue of Feynman gauge, and in the de Sitter invariant, Lorentz gauge. In each case our result is that the finite part of the conformal counterterm can be chosen so that the mode functions experience no significant one loop corrections at late times. This is in perfect agreement with a recent, all orders stochastic prediction.

We study the possibility that dark energy is a manifestation of the Casimir energy on extra dimensions with the topology of $S^2$. We consider our universe to be $M^4\times S^2$ and modify the geometry by introducing noncommutativity on the extra dimensions only, i.e. replacing $S^2$ with the fuzzy version $S_F^2$. We find the energy density as a function of the size of the representation $M+1$ of the algebra of $S_F^2$, and we calculate its value for the $M+1=2$ case. The value of the energy density turns out to be positive, i.e. provides dark energy, and the size of the extra dimensions agrees with the experimental limit. We also recover the correct commutative limit as the noncommutative parameter goes to zero.

We discuss specific heat and neutrino emissivity due to direct Urca processes for quark matter in the color superconductive Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase of quantum chromodynamics. We assume that the three light quarks $u$, $d$, $s$ are in a color and electrically neutral state and interact by a four-fermion Nambu–Jona-Lasinio coupling. We study a LOFF state characterized by a single plane wave for each pairing. From the evaluation of neutrino emissivity and fermionic specific heat, the cooling rate of simplified models of compact stars with a quark core in the LOFF state is estimated.

The equation of motion of a massive scalar field obtained by W. T. Kim et al. [Phys. Rev. D 66, 044017 (2002)] in the black hole limit is rederived. Some relevant aspects of this equation are then discussed.

The influence of the gravity acceleration on the regularized energy-momentum tensor of the quantized electromagnetic field between two plane-parallel conducting plates is derived. We use Fermi coordinates and work to first order in the constant acceleration parameter. A perturbative expansion, to this order, of the Green functions involved and of the energy-momentum tensor is derived by means of the covariant geodesic point-splitting procedure. In correspondence to the Green functions satisfying mixed and gauge-invariant boundary conditions, and Ward identities, the energy-momentum tensor is covariantly conserved and satisfies the expected relation between gauge-breaking and ghost parts, while a new simple formula for the trace anomaly is obtained to first order in the constant acceleration. A more systematic derivation is therefore obtained of the theoretical prediction according to which the Casimir device in a weak gravitational field will experience a tiny push in the upwards direction.

We investigate spontaneous symmetry breaking within the linear sigma model with the $\mathrm{SU}(2)\times \mathrm{U}(1)$ internal symmetry at finite chemical potential, which was suggested as a model for kaon condensation in the color-flavor-locked phase of dense quark matter. One-loop corrections to the scalar field effective potential as well as its propagator are calculated. Particular attention is paid to the type-II Goldstone boson that appears in the Bose-Einstein condensed phase. Furthermore, we show that the type-I Goldstone boson—the superfluid phonon—is allowed to decay due to the nonlinearity of its dispersion relation at high momentum, and determine its decay width.

A host of dark energy models and nonstandard cosmologies predict an enhanced Hubble rate in the early Universe: perfectly viable models, which satisfy big bang nucleosynthesis (BBN), cosmic microwave background and general relativity tests, may nevertheless lead to enhancements of the Hubble rate up to many orders of magnitude. In this paper we show that strong bounds on the pre-BBN evolution of the Universe may be derived, under the assumption that dark matter is a thermal relic, by combining the dark matter relic density bound with constraints coming from the production of cosmic-ray antiprotons by dark matter annihilation in the Galaxy. The limits we derive apply to the Hubble rate around the temperature of dark matter decoupling. For dark matter masses lighter than 100 GeV, the bound on the Hubble rate enhancement ranges from a factor of a few to a factor of 30, depending on the actual cosmological model, while for a mass of 500 GeV the bound falls in the range 50–500. Uncertainties in the derivation of the bounds and situations where the bounds become looser are discussed. We finally discuss how these limits apply to some specific realizations of nonstandard cosmologies: a scalar-tensor gravity model, kination models and a Randall-Sundrum D-brane model.

This paper deals with the reconstruction of the direction of a gravitational wave source using the detection made by a network of interferometric detectors, mainly the LIGO and Virgo detectors. We suppose that an event has been seen in coincidence using a filter applied on the three detector data streams. Using the arrival time (and its associated error) of the gravitational signal in each detector, the direction of the source in the sky is computed using a ${\chi }^2$ minimization technique. For reasonably large signals ($\mathrm{SNR}>4.5$ in all detectors), the mean angular error between the real location and the reconstructed one is about 1°. We also investigate the effect of the network geometry assuming the same angular response for all interferometric detectors. It appears that the reconstruction quality is not uniform over the sky and is degraded when the source approaches the plane defined by the three detectors. Adding at least one other detector to the LIGO-Virgo network reduces the blind regions and in the case of 6 detectors, a precision less than 1° on the source direction can be reached for 99% of the sky.

Many models of electroweak symmetry-breaking with an extended Higgs sector exhibit improved naturalness, wherein the new physics scale, at which quadratic divergences of Higgs mass parameters due to top quark loops are cut off, can be pushed beyond the reach of the Large Hadron Collider without unnatural fine-tuning. Such models include examples where the new physics is supersymmetry, implying that supersymmetry may still solve the hierarchy problem, even if it eludes detection at the Large Hadron Collider.

We extend the resummation of dimensionally regulated amplitudes to next-to-next-to-leading poles. This requires the calculation of two-loop anomalous dimension matrices for color mixing through soft gluon exchange. Remarkably, we find that they are proportional to the corresponding one-loop matrices. Using the color-generator notation, we reproduce the two-loop single-pole quantities ${\mathbf{H}}^{(2)}$ introduced by Catani for quark and gluon elastic scattering. Our results also make possible threshold and a variety of other resummations at next-to-next-to-leading logarithm. All of these considerations apply to $2\to n$ processes with massless external lines.

We present a measurement of the branching fraction for the doubly-Cabibbo-suppressed decay $D^{+}\to K^{+}{\pi }^0$, using $281{\mathrm{pb}}^{-1}$ of data accumulated with the CLEO-c detector on the $\psi (3770)$ resonance. We find $\mathcal{B}(D^{+}\to K^{+}{\pi }^0)=(2.28\pm 0.36\pm 0.15\pm 0.08)\times {10}^{-4}$, where the first uncertainty is statistical, the second is systematic, and the last error is due to the uncertainty in the reference mode branching fraction.

We derive from the Einstein equation an evolution law for the area of a trapping or dynamical horizon. The solutions to this differential equation show a causal behavior. Moreover, in a viscous fluid analogy, the equation can be interpreted as an energy balance law, yielding to a positive bulk viscosity. These two features contrast with the event horizon case, where the noncausal evolution of the area and the negative bulk viscosity require teleological boundary conditions. This reflects the local character of trapping horizons as opposed to event horizons. Interpreting the area as the entropy, we propose to use an area/entropy evolution principle to select a unique dynamical horizon and time slicing in the Cauchy evolution of an initial marginally trapped surface.

A Dirac electron field is quantized in the background of a Dirac magnetic monopole, and the phenomenon of induced quantum numbers in this system is analyzed. We show that, in addition to electric charge, also squares of orbital angular momentum, spin, and total angular momentum are induced. The functional dependence of these quantities on the temperature and the $CP$-violating vacuum angle is determined. Thermal quadratic fluctuations of charge and squared total angular momentum, as well as the correlation between them and their correlations with squared orbital angular momentum and squared spin, are examined. We find the conditions when charge and squared total angular momentum at zero temperature are sharp quantum observables rather than mere quantum averages.