We investigate the possibility of precision measurements for parameters of the littlest Higgs model with $T$ parity at the International Linear Collider. The model predicts new gauge bosons ($A_{\mathrm{H}}$, $Z_{\mathrm{H}}$, and $W_{\mathrm{H}}$), among which the heavy photon ($A_{\mathrm{H}}$) is a candidate for dark matter. The masses of these new gauge bosons strongly depend on the vacuum expectation value that breaks a global symmetry of the model. Through Monte Carlo simulations of the processes, $e^{+}{e}^{-}\to A_{\mathrm{H}}{Z}_{\mathrm{H}}$ and $e^{+}{e}^{-}\to W_{\mathrm{H}}^{+}{W}_{\mathrm{H}}^{-}$, we show how precisely the masses can be determined at the International Linear Collider for a representative parameter point of the model. We also discuss the determination of the little Higgs parameters and their impact on the future measurement of the thermal abundance of the dark matter relics in our Universe.

We compute to next-to-leading order in QCD the tensor unparticle contribution to the diphoton production at the LHC, wherein the unparticle sector is a consequence of (a) scale invariance but not full conformal invariance and (b) conformal invariance. We use the semianalytical two cutoff phase-space slicing method to handle the $\mathcal{O}({\alpha }_s)$ corrections to the $pp\to \gamma \gamma X$ and show that our results are insensitive to the soft and collinear cutoffs. In order to avoid the contribution of the photons due to fragmentation, we employ the smooth cone isolation criterion. Significance of the QCD corrections to the diphoton events including unparticles is highlighted.

We present a quenched lattice calculation of all six form factors: vector [$f_1(q^2)$], weak-magnetism [$f_2(q^2)$], induced scalar [$f_3(q^2)$], axial-vector [$g_1(q^2)$], weak electricity [$g_2(q^2)$], and induce pseudoscalar [$g_3(q^2)$] form factors, in hyperon semileptonic decay ${\Xi }^0\to {\Sigma }^{+}l\overline{\nu }$ using domain wall fermions. The $q^2$ dependences of all form factors in the relatively low $q^2$ region are examined in order to evaluate their values at zero momentum transfer. The ${\Xi }^0\to {\Sigma }^{+}$ transition is highly sensitive to flavor SU(3) breaking since this decay corresponds to the direct analogue of neutron beta decay under the exchange of the down quark with the strange quark. The pattern of flavor SU(3) breaking effects in the hyperon beta decay is easily exposed in a comparison to results for neutron beta decay. We measure SU(3)-breaking corrections to $f_1(0)$, $f_2(0)/f_1(0)$, and $g_1(0)/f_1(0)$. A sign of the leading-order corrections, of which the size is less than a few percent, on $f_1(0)$ is likely negative, while $f_2(0)/f_1(0)$ and $g_1(0)/f_1(0)$ receive positive corrections of order 16% and 5%, respectively. The observed pattern of the deviation from the values in the exact SU(3) limit does not support some of the model estimates. We show that there are nonzero second-class form factors in the ${\Xi }^0\to {\Sigma }^{+}$ decay, measuring $f_3(0)/f_1(0)=0.14(9)$ and $g_2(0)/g_1(0)=0.68(18)$, which are comparable to the size of first-order SU(3) breaking. It is also found that the SU(3) breaking effect on $g_3(0)/g_1(0)$ agrees with the prediction of the generalized pion-pole dominance.

We study the nucleon, Sigma and cascade octet baryon electromagnetic form factors and the effects of SU(3) flavor symmetry breaking from $2+1$-flavor lattice calculations. We find that electric and magnetic radii are similar; the maximum discrepancy is about 10%. In the pion-mass region we explore, both the quark-component and full-baryon moments have small SU(3) symmetry breaking. We extrapolate the charge radii and the magnetic moments using three-flavor heavy-baryon chiral perturbation theory. The systematic errors due to chiral and continuum extrapolations remain significant, giving rise to charge radii for $p$ and ${\Sigma }^{-}$ that are 3–4 standard deviations away from the known experimental ones. Within these systematics the predicted ${\Sigma }^{+}$ and ${\Xi }^{-}$ radii are 0.67(5) and $0.306(15){\mathrm{fm}}^2$, respectively. When the next-to-next-to-leading order of heavy-baryon chiral perturbation theory is included, the extrapolated magnetic moments are less than 3 standard deviations away from Particle Data Group values, and the discrepancy is possibly due to remaining chiral and continuum extrapolation errors.

This paper is devoted to the study of the processes $e^{+}{e}^{-}\to J/\Psi {\eta }_c$, $J/\Psi {\eta }_c^{\prime }$, ${\psi }^{\prime }{\eta }_c$, ${\psi }^{\prime }{\eta }_c^{\prime }$ within light cone formalism. It is shown that if one disregards the contribution of higher Fock states, the twist-3 distribution amplitudes needed in the calculation can be unambiguously determined from the twist-2 distribution amplitudes and equations of motion. Using models of the twist-2 distribution amplitudes the cross sections of the processes under study are calculated. The results of the calculation are in agreement with Belle and BABAR experiments. It is also shown that relativistic and radiative corrections to the cross sections play a crucial role in the achievement of the agreement between the theory and experiments. A comparison of the results of this paper with the results obtained in other papers is carried out. In particular, it is shown that the results of the papers where relativistic and radiative corrections were calculated within nonrelativistic QCD are overestimated by a factor of $\sim 1.5$.

Recently it was pointed out that for the evaluation of the numerically dominant pion-exchange contribution to the hadronic light-by-light scattering correction in the muon $g-2$, a fully off-shell pion-photon-photon form factor should be used. Following this proposal, we first derive a new short-distance constraint on the off-shell form factor which enters at the external vertex for the muon $g-2$ and show that it is related to the quark condensate magnetic susceptibility in QCD. We then evaluate the pion-exchange contribution in the framework of large-$N_C$ QCD using an off-shell form factor which fulfills all short-distance constraints. With a value for the magnetic susceptibility as estimated in the same large-$N_C$ framework, we obtain the result $a_{\mu }^{\mathrm{LbyL};{\pi }^0}=(72\pm 12)\times {10}^{-11}$. Updating our earlier results for the contributions from the exchanges of the $\eta$ and ${\eta }^{\prime }$ using simple vector-meson dominance form factors, we obtain $a_{\mu }^{\mathrm{LbyL};\mathrm{PS}}=(99\pm 16)\times {10}^{-11}$ for the sum of all light pseudoscalars. Combined with available evaluations for the other contributions to hadronic light-by-light scattering this leads to the new estimate $a_{\mu }^{\mathrm{LbyL};\mathrm{had}}=(116\pm 40)\times {10}^{-11}$.

The possibility of having a gauge fixing term in the effective Lagrangian that is not a quadratic expression has been explored in spin-two theories so as to have a propagator that is both traceless and transverse. We first show how this same approach can be used in spontaneously broken gauge theories as an alternate to the ’t Hooft gauge fixing which avoids terms quadratic in the scalar fields. This “nonquadratic” gauge fixing in the effective action results in two complex fermionic and one real bosonic ghost field. A global gauge invariance involving a fermionic gauge parameter, analogous to the usual Becchi-Rouet-Stora-Tyutin invariance, is present in this effective action.

We study the $\beta$ deformation of $\mathcal{N}=4$ super Yang-Mills theory on $S^3$ with chemical potentials for the $U(1{)}_R$ as well as the two global $U(1)$ symmetries. The one-loop effective potential at weak coupling is computed for both the Coulomb and Higgs branches. At near critical chemical potential and small finite temperature, we find a metastable state at the origin of moduli space. On the Higgs branch, this has the interpretation in terms of deconstruction as an extra-dimensional torus which becomes metastable for infinite size and decays to zero size through quantum tunneling and thermal activation. At strong coupling, the theory is described by its gravitational dual. The relevant background is found by performing a TsT transformation on the solution describing an ${\mathrm{AdS}}_5$ black hole spinning in $S^5$. A probe-brane calculation, using giant gravitons as probes, reveals qualitative agreement with the weak coupling results.

It is known that including vector mesons stabilizes the size of a Skyrmion without the need for a Skyrme term. This paper provides the first results for static multi-Skyrmions in such a theory. The rational map ansatz is used to investigate multi-Skyrmions in a theory which includes the $\omega$ vector meson and has no Skyrme term. Bound states with baryon numbers two, three, and four are found, which have axial, tetrahedral, and cubic symmetries, respectively. The results reveal a qualitative similarity with the standard Skyrme model with a Skyrme term and no vector mesons, suggesting that some features are universal and do not depend on the details of the theory. Setting the pion decay constant and meson masses to their experimental values leaves only a single free parameter in the model. Fixing this parameter, by equating the energy of the baryon number four Skyrmion to the ${\mathrm{He}}^4$ mass, yields reasonable results for other baryon numbers.

The Solar System metric recommended by the International Astronomical Union (IAU) resolution B1.3, during its 24th general assembly, allows light propagation calculations until order $c^{-3}$ only. However, an increasing number of forthcoming spatial experiments will require a modelization of the gravitational field including all the $c^{-4}$ terms in the metric to describe light propagation at the required precision. This will be the case for missions planned or in project, like TIPO, ASTROD, LATOR. Hence, it is necessary to extend the IAU framework to include all the relevant contributing terms. This paper proposes such an extension.

In the scalar-tensor theory of gravitation it seems nontrivial to establish if solutions of the cosmological equations in the presence of a cosmological constant (or a vacuum energy) behave as attractors independently of the initial values. We develop a general formulation in terms of two-dimensional phase space, mainly according to the Brans-Dicke model requiring the scalar field decoupled from the matter Lagrangian in the Jordan frame. We show that there are two kinds of fixed points, one of which is an attractor depending on the coupling constant and equation of state. We find that the static universe in the Jordan frame is an attractor in the presence of a cosmological constant for some range of the coupling constant. We extend our analysis to a power-law potential, finding a new type of power-law inflation caused by the coupling to the matter fluid, also as an attractor.

We quantify the consistency of numerical-relativity black-hole-binary waveforms for use in gravitational-wave (GW) searches with current and planned ground-based detectors. We compare previously published results for the $(\ell =2,|m|=2)$ mode of the gravitational waves from an equal-mass nonspinning binary, calculated by five numerical codes. We focus on the $1000M$ (about six orbits, or 12 GW cycles) before the peak of the GW amplitude and the subsequent ringdown. We find that the phase and amplitude agree within each code’s uncertainty estimates. The mismatch between the $(\ell =2,|m|=2)$ modes is better than ${10}^{-3}$ for binary masses above $60M_{\odot }$ with respect to the Enhanced LIGO detector noise curve, and for masses above $180M_{\odot }$ with respect to Advanced LIGO, Virgo, and Advanced Virgo. Between the waveforms with the best agreement, the mismatch is below $2\times {10}^{-4}$. We find that the waveforms would be indistinguishable in all ground-based detectors (and for the masses we consider) if detected with a signal-to-noise ratio of less than $\approx 14$, or less than $\approx 25$ in the best cases.

We study effects of possible tachyonic perturbations of dark energy on the CMB temperature anisotropy. Motivated by some models of phantom energy, we consider both Lorentz-invariant and Lorentz-violating dispersion relations for tachyonic perturbations. We show that in the Lorentz-violating case, the shape of the CMB anisotropy spectrum generated by the tachyonic perturbations is very different from that due to adiabatic scalar perturbations and, if sizeable, it would be straightforwardly distinguished from the latter. The tachyonic contribution improves slightly the agreement between the theory and data; however, this improvement is not statistically significant, so our analysis results in limits on the time scale of the tachyonic instability. In the Lorentz-invariant case, tachyonic contribution is a rapidly decaying function of the multipole number $l$, so that the entire observed dipole may be generated without conflicting the data at higher multipoles. On the conservative side, our comparison with the data places limit on the absolute value of the (imaginary) tachyon mass in the Lorentz-invariant case.

With the prospect of measuring the fraction of arriving secondary photons, produced through photo-pion energy-loss interactions of ultra-high-energy cosmic ray (UHECR) protons with the microwave background during propagation, we investigate how information about the local UHECR source distribution can be inferred from the primary (proton) to secondary (photon) ratio. As an aid to achieve this, we develop an analytic description for both particle populations as a function of propagation time. Through a consideration of the shape of the Greisen-Zatsepin-Kuzmin cutoff and the corresponding photon fraction curve, we investigate the different results expected for both different maximum proton energies injected by the sources, as well as a change in the local source distribution following a perturbative deformation away from a homogeneous description. At the end of the paper, consideration is made as to how these results are modified through extragalactic magnetic field effects on the proton’s propagation. The paper aims to demonstrate how the shape of the cosmic ray flux in the cutoff region, along with the photon fraction, are useful indicators of the cutoff origin as well as the local UHECR source distribution.

The energy at which cosmic rays from extra-galactic sources begin to dominate over those from galactic sources is an important open question in astroparticle physics. A natural candidate is the energy at the “ankle” in the approximately power-law energy spectrum which is indicative of a crossover from a falling galactic component to a flatter extra-galactic component. The transition can occur without such flattening but this requires some degree of conspiracy of the spectral shapes and normalizations of the two components. Nevertheless, it has been argued that extra-galactic sources of cosmic ray protons that undergo interactions on the CMB can reproduce the energy spectrum below the ankle if the crossover energy is as low as the “second knee” in the spectrum. This low crossover model is constrained by direct measurements by the Pierre Auger Observatory, which indicate a heavier composition at these energies. We demonstrate that upper limits on the cosmic diffuse neutrino flux provide a complementary constraint on the proton fraction in ultra-high energy extra-galactic cosmic rays and forthcoming data from IceCube will provide a definitive test of this model.

Estimation of the angular power spectrum of the cosmic microwave background on a small patch of sky is usually plagued by serious spectral leakage, especially when the map has a hard edge. Even on a full-sky map, point source masks can alias power from large scales to small scales producing excess variance at high multipoles. We describe a new fast, simple, and local method for estimation of power spectra on small patches of the sky that minimizes spectral leakage and reduces the variance of the spectral estimate. For example, when compared with the standard uniform sampling approach on a $8\mathrm{degree}\times 8\mathrm{degree}$ patch of the sky with 2% area masked due to point sources, our estimator halves the error bars at $\ell =2000$ and achieves a more than fourfold reduction in error bars at $\ell =3500$. Thus, a properly analyzed experiment will have error bars at $\ell =3500$ equivalent to those of an experiment analyzed with the now standard technique with $\sim 16–25$ times the integration time.

We obtain tree-level estimates of various differential branching ratios of heavy baryon decays with massive sterile neutrinos ${\nu }_x$ in the final state. Generally, charmed baryons are found to be less promising than charmed mesons, in contrast to $b$ hadrons. In the latter case, branching ratios of beauty mesons and baryons into sterile neutrinos are of the same order. As a consequence, at high energies beauty baryons give contribution to sterile neutrino production comparable to the contribution of beauty mesons (up to about 15%). Experimental limits on active-to-sterile mixing are quite strong for neutrinos lighter than $D$ mesons but for heavier neutrinos they are weaker. As an example, for neutrino masses in the range $2\mathrm{GeV}\lesssim m_{{\nu }_x}\lesssim 2.5\mathrm{GeV}$, current data imply that the bounds on ${\Lambda }_b$-hyperon branching ratios into sterile neutrinos are $\mathrm{Br}({\Lambda }_b\to {\Lambda }_c+e^{-}+{\nu }_x)\lesssim 1.3\times {10}^{-5}–1.7\times {10}^{-6}$ and $\mathrm{Br}({\Lambda }_b\to {\Lambda }_c+{\mu }^{-}+{\nu }_x)\lesssim 3.9\times {10}^{-7}–1.4\times {10}^{-7}$.

We explore the possibility to discriminate between certain strongly coupled technicolor (TC) models and warped extra dimensional models where the standard model fields are propagating in the extra dimension. We consider a generic QCD-like TC model with running coupling as well as two TC models with walking dynamics. We argue that, due to the different production mechanisms for the lowest-lying composite tensor state in these TC theories compared to the first Kaluza-Klein graviton mode of the warped extra dimensional case, it is possible to distinguish between these models based on the angular analysis of the reconstructed longitudinal $Z$ bosons in the $pp\to ZZ\to 4$ charged leptons channel.

We study high-$p_T$ jets from QCD and from highly boosted massive particles such as tops, $W$, $Z$, and Higgs bosons, and argue that infrared-safe observables can help reduce QCD backgrounds. Jets from QCD are characterized by different patterns of energy flow compared to the products of highly boosted heavy particle decays, and we employ a variety of jet shapes, observables restricted to energy flow within a jet, to explore this difference. Results from Monte Carlo generators and arguments based on perturbation theory support the discriminating power of the shapes we refer to as planar flow and angularities. We emphasize that for massive jets, these and other observables can be analyzed perturbatively.