We study the radiative decay into $\gamma$ and a baryon of the SU(3) octet and decuplet of nine and ten resonances that are dynamically generated from the interaction of vector mesons with baryons of the octet and the decuplet, respectively. We obtain quite different partial decay widths for the various resonances, and for different charge states of the same resonance, suggesting that the experimental investigation of these radiative decays should bring much information on the nature of these resonances. For the case of baryons of the octet we determine the helicity amplitudes and compare them with experimental data when available.

We study the longitudinal polarization of the tau lepton in $\overline{B}\to D\tau \overline{\nu }$ decay. After discussing possible sensitivities of $\tau$ decay modes to the $\tau$ polarization, we examine the effect of charged Higgs boson on the $\tau$ polarization in $\overline{B}\to D\tau \overline{\nu }$. We find a relation between the decay rate and the $\tau$ polarization, and clarify the role of the $\tau$ polarization measurement in the search for the charged Higgs boson.

We present a measurement of the $t\overline{t}$ cross section using high-multiplicity jet events produced in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$. These data were recorded at the Fermilab Tevatron Collider with the D0 detector. Events with at least six jets, two of them identified as $b$ jets, were selected from a $1{\mathrm{fb}}^{-1}$ data set. The measured cross section, assuming a top quark mass of $175\mathrm{GeV}/c^2$, is $6.9\pm 2.0\mathrm{pb}$, in agreement with theoretical expectations.

We find two systems via holography that exhibit quantum Berezinskii-Kosterlitz-Thouless (BKT) phase transitions. The first is the ABJM theory with flavor and the second is a flavored (1, 1) little string theory. In each case the transition occurs at nonzero density and magnetic field. The BKT transition in the little string theory is the first example of a quantum BKT transition in ($3+1$) dimensions. As in the “original” holographic BKT transition in the D3/D5 system, the exponential scaling is destroyed at any nonzero temperature and the transition becomes second order. Along the way we construct holographic renormalization for probe branes in the ABJM theory and propose a scheme for the little string theory. Finally, we obtain the embeddings and (half of) the meson spectrum in the ABJM theory with massive flavor.

We study the generation of small neutrino masses in an extra-dimensional model, where singlet fermions are allowed to propagate in the extra dimension, while the standard model particles are confined to a brane. Motivated by the fact that extra-dimensional models are nonrenormalizable, we truncate the Kaluza-Klein towers at a maximal Kaluza-Klein number. This truncation, together with the structure of the bulk Majorana mass term, motivated by the Sherk-Schwarz mechanism, implies that the Kaluza-Klein modes of the singlet fermions pair to form Dirac fermions, except for a number of unpaired Majorana fermions at the top of each tower. These heavy Majorana fermions are the only sources of lepton number breaking in the model, and similarly to the type-I seesaw mechanism, they naturally generate small masses for the left-handed neutrinos. The lower Kaluza-Klein modes mix with the light neutrinos, and the mixing effects are not suppressed with respect to the light-neutrino masses. Compared to conventional fermionic seesaw models, such mixing can be more significant. We study the signals of this model at the Large Hadron Collider, and find that the current low-energy bounds on the nonunitarity of the leptonic mixing matrix are strong enough to exclude an observation.

Many classical scalar field theories possess remarkable solutions: coherently oscillating, localized clumps, known as oscillons. In many cases, the decay rate of classical small amplitude oscillons is known to be exponentially suppressed and so they are extremely long lived. In this work we compute the decay rate of quantized oscillons. We find it to be a power law in the amplitude and couplings of the theory. Therefore, the quantum decay rate is very different to the classical decay rate and is often dominant. We show that essentially all oscillons eventually decay by producing outgoing radiation. In single field theories the outgoing radiation has typically linear growth, while if the oscillon is coupled to other bosons the outgoing radiation can have exponential growth. The latter is a form of parametric resonance: explosive energy transfer from a localized clump into daughter fields. This may lead to interesting phenomenology in the early universe. Our results are obtained from a perturbative analysis, a nonperturbative Floquet analysis, and numerics.

Expectation values of the electromagnetic field and the electric current are introduced at space-time resolution which belongs to the quantum domain. These allow us to approach some key features of classical electrodynamics from the underlying QED. One is the emergence of the radiation field in the retarded solution of the Maxwell equation, derived from an action principle. Another question discussed is the systematic derivation of the polarizability of a charge system. Furthermore, the decoherence and the consistency of the photon field are established by a perturbative calculation of the reduced density matrix for the electromagnetic field within the closed time path formalism.

We study the classical radiation emitted by free-falling charges in de Sitter spacetime coupled to different kinds of fields. Specifically we consider the cases of the electromagnetic field, linearized gravity, and scalar fields with arbitrary mass and curvature coupling. Given an arbitrary set of such charges, there is a generic result for sufficiently late times which corresponds to each charge being surrounded by a field zone with negligible influence from the other charges. Furthermore, we explicitly find a static solution in the static patch adapted to a charge (implying no energy loss by the charge) which can be regularly extended beyond the horizon to the full de Sitter spacetime, and show that any other solution decays at late times to this one. On the other hand, for nonconformal scalar fields the inertial observers naturally associated with spatially flat coordinates will see a nonvanishing flux far from the horizon, which will fall off more slowly than the inverse square of the distance for sufficiently light fields ($m^2+\xi R<5H^2/4$) and give rise to a total integrated flux that grows unboundedly with the radius. This can be qualitatively interpreted as a consequence of a classical parametric amplification of the field generated by the charge due to the time-dependent background spacetime. Most of these results do not hold for massless minimally coupled scalar fields, whose special behavior is analyzed separately.

Traversable wormholes are primarily useful as “gedanken experiments” and as a theoretician’s probe of the foundations of general relativity. In this work, we analyze the possibility of having tunnels in a hyperbolic spacetime. We obtain exact solutions of static and pseudo-spherically symmetric spacetime tunnels by adding exotic matter to a vacuum solution referred to as a degenerate solution of class A. The physical properties and characteristics of these intriguing solutions are explored, and through the mathematics of embedding it is shown that particular constraints are placed on the shape function, that differ significantly from the Morris-Thorne wormhole. In particular, it is shown that the energy density is always negative, and the radial pressure is positive, at the throat, contrary to the Morris-Thorne counterpart. Specific solutions are also presented by considering several equations of state, and by imposing restricted choices for the shape function or the redshift function.

The existence of a sizable, $\mathcal{O}({10}^{-10}–{10}^{-9}\mathrm{G})$, cosmological magnetic field in the early Universe has been postulated as a necessary step in certain formation scenarios for the large-scale $\mathcal{O}(\mu \mathrm{G})$ magnetic fields found in galaxies and galaxy clusters. If this field exists then it may induce significant mixing between photons and axion-like particles (ALPs) in the early Universe. The resonant conversion of photons into ALPs in a primordial magnetic field has been studied elsewhere by Mirizzi, Redondo and Sigl (2009). Here we consider the nonresonant mixing between photons and scalar ALPs with masses much less than the plasma frequency along the path, with specific reference to the chameleon scalar field model. The mixing would alter the intensity and polarization state of the cosmic microwave background (CMB) radiation. We find that the average modification to the CMB polarization modes is negligible. However the average modification to the CMB intensity spectrum is more significant and we compare this to high-precision measurements of the CMB monopole made by the far infrared absolute spectrophotometer on board the COBE satellite. The resulting 95% confidence limit on the scalar-photon conversion probability in the primordial field (at 100 GHz) is ${\overline{\mathcal{P}}}_{\gamma \leftrightarrow \varphi }<2.6\times {10}^{-2}$. This corresponds to a degenerate constraint on the photon-scalar coupling strength, $g_{\mathrm{eff}}$, and the magnitude of the primordial magnetic field. Taking the upper bound on the strength of the primordial magnetic field derived from the CMB power spectra, $B_{\lambda }\le 5.0\times {10}^{-9}\mathrm{G}$, this would imply an upper bound on the photon-scalar coupling strength in the range $g_{\mathrm{eff}}\lesssim 7.14\times {10}^{-13}{\mathrm{GeV}}^{-1}$ to $g_{\mathrm{eff}}\lesssim 9.20\times {10}^{-14}{\mathrm{GeV}}^{-1}$, depending on the power spectrum of the primordial magnetic field.

I begin to look at the growth of weak density inhomogeneities of nonrelativistic matter, in bimetric-MOND (BIMOND) cosmology. Far from making an exhaustive study, I concentrate on one attractive cosmological scenario, which employs matter-twin-matter-symmetric versions of BIMOND, and, furthermore, assumes that, on average, the universe is symmetrically populated in the two sectors. MOND effects are totally absent in an exactly symmetric universe, apart from the significant possible appearance of a cosmological constant, $\Lambda \sim (a_0/c{)}^2$. MOND effects—local and cosmological—do enter when density inhomogeneities that differ in the two sectors appear and develop. MOND later takes its standard form in systems that are islands dominated by pure matter, as are presumably the well scrutinized systems such as galaxies. I derive the nonrelativistic (weak-field-slow-motion) equations governing small-scale fluctuation growth. The equations split into two uncoupled systems, one for the sum, the other for the difference, of the fluctuations in the two sectors. The former is governed strictly by Newtonian dynamics, and describes standard growth of fluctuations. The latter is governed by MOND dynamics, which entails stronger gravity, and nonlinearity even for the smallest of perturbations. These cause the difference to grow faster than the sum, leading to anticorrelated perturbations, conducing to matter-twin-matter segregation (which continues for high overdensities). The nonlinearity also causes interaction between nested perturbations on different scales. Because matter and twin matter (TM) repel each other in the MOND regime, matter inhomogeneities grow not only by their own self-gravity, but also through shepherding by flanking twin matter overdensities (and vice versa). The relative importance of gravity and pressure in the MOND system (analog of the Jeans criterion), depends also on the strength of the perturbation. MOND gravity, which scales as the square root of the difference perturbation, holds sway over pressure for any mass, for weak enough perturbations. The development of structure in the universe, in either sector, thus depends crucially on two initial fluctuation spectra: that of matter alone and that of the matter-TM difference. I also discuss the backreaction on cosmology of BIMOND effects that appear as “phantom matter” (interpreted by some as “dark matter”), resulting from inhomogeneity differences between the two sectors.

If dark matter (DM) simply consists in a scalar particle interacting dominantly with the Higgs boson, the ratio of its annihilation cross section—which is relevant both for the relic abundance and indirect detection—and its spin-independent scattering cross section on nuclei depends only on the DM mass. It is an intriguing result that, fixing the mass and direct detection rate to fit the annual modulation observed by the DAMA experiment, one obtains a relic density in perfect agreement with its observed value. In this article we update this result and confront the model to the recent CoGeNT data, tentatively interpreting the excess of events in the recoil energy spectrum as being due to DM. CoGeNT, as DAMA, points toward a light DM candidate, with somewhat different (but not necessarily incompatible) masses and cross sections. For the CoGeNT region too, we find an intriguing agreement between the scalar DM relic density and direct detection constraints. We give the $1\sigma$ region favored by the CDMS-II events, and our exclusion limits for the Xenon10 (2009) and Xenon100 data, which, depending on the scintillation efficiency, may exclude CoGeNT and DAMA. Assuming CoGeNT and/or DAMA to be due to scalar singlet DM leads to definite predictions regarding indirect detection and at colliders. We specifically emphasize the limit on the model that might be set by the current Fermi-LAT data on dwarf galaxies, and the implications for the search for the Higgs at the LHC.

It is crucial to identify the ultrahigh-energy cosmic-ray sources and probe their unknown properties. Recent results from the Pierre Auger Observatory favor a heavy nuclear composition for the ultrahigh-energy cosmic rays. Under the requirement that heavy nuclei survive in these sources, using gamma-ray bursts as an example, we predict a diagnostic gamma-ray signal, unique to nuclei—the emission of deexcitation gamma rays following photodisintegration. These gamma rays, boosted from MeV to TeV-PeV energies, may be detectable by gamma-ray telescopes such as VERITAS, HESS, and MAGIC, and especially the next-generation CTA and AGIS. They are a promising messenger to identify and study individual ultrahigh-energy nuclei accelerators.

We perform a linear stability analysis of dynamical Chern-Simons modified gravity in the geometric optics approximation and find that it is linearly stable on the backgrounds considered. Our analysis also reveals that gravitational waves in the modified theory travel at the speed of light in Minkowski spacetime. However, on a Schwarzschild background the characteristic speed of propagation along a given direction splits into two modes, one subluminal and one superluminal. The width of the splitting depends on the azimuthal components of the propagation vector, is linearly proportional to the mass of the black hole, and decreases with the third inverse power of the distance from the black hole. Radial propagation is unaffected, implying that as probed by gravitational waves the location of the event horizon of the spacetime is unaltered. The analysis further reveals that when a high frequency, pure gravitational wave is scattered from a black hole, a scalar wave of comparable amplitude is excited, and vice versa.

Charmed meson decays to a light pseudoscalar ($P$) and light vector ($V$) meson are analyzed taking account of $\eta \mathrm{\text{−}}{\eta }^{\prime }$ mixing. A frequently-used octet-singlet mixing angle of 19.5° is compared with a value of 11.7° favored by a recent analysis of $D\to PP$ decays.

In this paper we discuss the global symmetries and the renormalizability of Lee-Wick (LW) scalar QED. In particular, in the “auxiliary-field” formalism we identify softly broken $SO(1,1)$ global symmetries of the theory. We introduce $SO(1,1)$ invariant gauge-fixing conditions that allow us to show in the auxiliary-field formalism directly that the number of superficially divergent amplitudes in a LW Abelian gauge theory is finite. To illustrate the renormalizability of the theory, we explicitly carry out the one-loop renormalization program in LW scalar QED and demonstrate how the counterterms required are constrained by the joint conditions of gauge and $SO(1,1)$ invariance. We also compute the one-loop beta functions in LW scalar QED and contrast them with those of ordinary scalar QED.

In a recent paper, we proposed a new class of supersymmetric $SO(10)$ models for neutrino masses where the TeV-scale electroweak symmetry is $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}$, making the associated gauge bosons $W_R$ and $Z^{\prime }$ accessible at the Large Hadron Collider. We showed that there exists a domain of Yukawa coupling parameters and symmetry breaking patterns which give an excellent fit to all fermion masses including neutrinos. In this sequel, we discuss an alternative Yukawa pattern which also gives a good fermion mass fit, and then study the predictions of both models for the proton lifetime. Consistency with current experimental lower limits on the proton lifetime require the squark masses of the first two generations to be larger than $\sim 1.2\mathrm{TeV}$. We also discuss how one can have simultaneous breaking of both $SU(2{)}_R\times U(1{)}_{B-L}$ and standard electroweak symmetries via radiative corrections.

In this paper, forward-backward asymmetry and differential cross section of top quark in flavor violating $Z^{\prime }$ model up to $\mathcal{O}({\alpha }_s^2{\alpha }_X)$ at Tevatron are calculated. In order to account for the top observed large forward-backward asymmetry, the new coupling $g_X$ among $Z^{\prime }$ and quarks will be not much less than strong coupling constant $g_s$. After including the new higher order correction, the differential cross section can fit the data better than those only including the leading contributions from $Z^{\prime }$, while the forward-backward asymmetry is still in agreement with the measurement.

We show that in the transitions ${\psi }^{\prime }\to h_c{\pi }^0$ and ${\eta }_c^{\prime }\to {\chi }_{c0}{\pi }^0$ the contributions from charmed-meson loops are highly suppressed, in contrast to various other charmonium decays. We calculate the width of the ${\psi }^{\prime }\to h_c{\pi }^0$, which agrees with the recent BES-III data, and predict the width of the ${\eta }_c^{\prime }\to {\chi }_{c0}{\pi }^0$, $\Gamma ({\eta }_c^{\prime }\to {\chi }_{c0}{\pi }^0)=1.5\pm 0.4\mathrm{keV}$. A confirmation of this prediction would also provide additional support for a recent analysis of ${\psi }^{\prime }\to J/\psi {\pi }^0(\eta )$, where loops are claimed to play a prominent role.

The new BABAR data on the pion-photon transition form factor arouses people’s interest for the determination of the pion distribution amplitude. To explain the data, we take both the leading valence quark state’s and the nonvalence quark state’s contributions into consideration, where the valence quark part up to next-to-leading order is presented and the nonvalence quark part is estimated by a phenomenological model based on its limiting behavior at both $Q^2\to 0$ and $Q^2\to \infty$. Our results show that to be consistent with the new BABAR data at the large $Q^2$ region, a broader amplitude other than the asymptoticlike pion distribution amplitude should be adopted. The broadness of the pion distribution amplitude is controlled by a parameter $B$. It has been found that the new BABAR data at low and high energy regions can be explained simultaneously by setting $B$ to be around 0.60, in which the pion distribution amplitude is closed to the Chernyak-Zhitnitsky form.