Top partners—vectorlike quarks which mix predominantly with the top quark, are simple extensions of the standard model present in many theories of new physics such as little Higgs models, topcolor models, and extra dimensions. Through renormalizable mixing with the top quark, these top partners inherit couplings to the Higgs boson. Higgs bosons produced from the decay of top partners are often highly boosted and ideal candidates for analyses based on jet substructure. Using substructure methods, we show that light Higgs bosons decaying to $\overline{b}b$ can be discovered at the 14 TeV LHC with less than $10{\mathrm{fb}}^{-1}$ for top-partner masses up to 1 TeV.

The dijet invariant mass distributions from the hadronic decay of unpolarized top quark ($t\to b{W}^{+}$ followed by $W^{+}\to u\overline{d}$) are calculated, including the next-to-leading order QCD radiative corrections. We treat the top decay in the complex mass scheme due to the existence of the intermediate state $W$ boson. Our analytical expressions are also available in different dimensional regularization schemes and ${\gamma }_5$ strategies. Finally, in order to construct the jets, we use different jet algorithms to compare their influences on our results. The obtained dijet mass distributions from the top quark decay are useful to distinguish these dijets from those produced via other sources and to clarify the issue about the recent CDF Collaboration’s $Wjj$ anomaly.

Masses and widths of the axial-vector charmed mesons $D_1(2420)$, $D_1(2430)$, $D_{s1}(2536)$, and $D_{s1}(2460)$ are calculated nonperturbatively in the resonance-spectrum-expansion model, by coupling various open and closed meson-meson channels to the bare $J^P=1^{+}$ $c\overline{q}$ ($q=u$, $d$) and $c\overline{s}$ states. The coupling to two-meson channels dynamically mixes and lifts the mass degeneracy of the spectroscopic ${}^{3}P_1$ and ${}^{1}P_1$ states, as an alternative to the usual spin-orbit splitting. Of the two resulting $S$-matrix poles in either case, one stays very close to the energy of the bare state, as a quasibound state in the continuum, whereas the other shifts considerably. This is in agreement with the experimental observation that the $D_1(2420)$ and $D_{s1}(2536)$ have much smaller widths than one would naively expect. The whole pattern of masses and widths of the axial-vector charmed mesons can thus be quite well reproduced with only two free parameters, one of which being already strongly constrained by previous model calculations. Finally, predictions for pole positions of radially excited axial-vector charmed mesons are presented.

In this paper, we propose a first-order action functional for a large class of systems that generalize the relativistic perfect fluids in the Kähler parametrization to noncommutative spacetimes. The noncommutative action is parametrized by two arbitrary functions $K(z,\overline{z})$ and $f(\sqrt{-}{j}^2)$ that depend on the fluid potentials and represent the generalization of the Kähler potential of the complex surface parametrized by $z$ and $\overline{z}$, respectively, and the characteristic function of each model. We calculate the equations of motion for the fluid potentials and the energy-momentum tensor in the first order in the noncommutative parameter. The density current does not receive any noncommutative corrections and it is conserved under the action of the commutative generators $P_{\mu }$ but the energy-momentum tensor is not. Therefore, we determine the set of constraints under which the energy-momentum tensor is divergenceless. Another set of constraints on the fluid potentials is obtained from the requirement of the invariance of the action under the generalization of the volume preserving transformations of the noncommutative spacetime. We show that the proposed action describes noncommutative fluid models by casting the energy-momentum tensor in the familiar fluid form and identifying the corresponding energy and momentum densities. In the commutative limit, they are identical to the corresponding quantities of the relativistic perfect fluids. The energy-momentum tensor contains a dissipative term that is due to the noncommutative spacetime and vanishes in the commutative limit. Finally, we particularize the theory to the case when the complex fluid potentials are characterized by a function $K(z,\overline{z})$ that is a deformation of the complex plane and show that this model has important common features with the commutative fluid such as infinitely many conserved currents and a conserved axial current that in the commutative case is associated to the topologically conserved linking number.

We study the hadron-quark phase transition in the interior of neutron stars. For the hadronic sector, we use a microscopic equation of state involving nucleons and hyperons derived within the Brueckner-Hartree-Fock many-body theory with realistic two-body and three-body forces. For the description of quark matter, we employ the Dyson-Schwinger approach and compare with the MIT bag model. We calculate the structure of neutron star interiors comprising both phases and find that with the Dyson-Schwinger model, the hadron-quark phase transition takes place only when hyperons are excluded, and that a two-solar-mass hybrid star is possible only if the nucleonic equation of state is stiff enough.

We explore equilibrium solutions of nontopological solitons in a general class of scalar field theories which include global $U(1)$ symmetry. We find new types of solutions, tube-shaped and crust-shaped objects, and investigate their stability. Like $Q$-balls, the new solitons can exist in supersymmetric extensions of the standard model, which may be responsible for baryon asymmetry and dark matter. Therefore, observational signals of the new solitons would give us more information on the early Universe and supersymmetric theories.

Anisotropic spherically symmetric systems are studied in the connection and densitized triad variables used in loop-quantum gravity. The material source is an anisotropic fluid, which is arguably the most commonly used source term in anisotropic studies within general relativity. The $\mathrm{\text{gravitational}}+\mathrm{\text{anisotropic}}$ fluid constraints are derived and analyzed and then quantum gravity inspired holonomy replacements are performed. The quantum properties of the fluid are dictated by the modified constraint equations. Particular attention is paid to wormhole throats, as they provide a simplistic model of the structures thought to be ubiquitous in the quantum gravity space-time foam at high energy scales. In comparison to the purely classical theory, the quantum corrections act to increase the energy density of the fluid, which indicates that they may lessen the energy condition violation present in the classical theory. Related to this, in principle it would be possible to have scenarios where the classical solution yields everywhere negative (with a zero at the throat) fluid energy density but the corresponding quantum-corrected theory possesses only small regions of negative energy density or even everywhere non-negative energy density.

We examine observational signatures of dark matter (DM) annihilation in the Milky Way arising from electroweak bremsstrahlung contributions to the annihilation cross section. It has been known for some time that photon bremsstrahlung may significantly boost DM annihilation yields. Recently, we have shown that electroweak bremsstrahlung of $W$ and $Z$ gauge bosons can be the dominant annihilation channel in some popular models with helicity-suppressed $2\to 2$ annihilation. $W/Z$-bremsstrahlung is particularly interesting because the gauge bosons produced via annihilation subsequently decay to produce large correlated fluxes of electrons, positrons, neutrinos, hadrons (including antiprotons) and gamma rays, which are all of importance in indirect DM searches. Here, we calculate the spectra of stable annihilation products produced via $\gamma /W/Z$-bremsstrahlung. After modifying the fluxes to account for the propagation through the Galaxy, we set upper bounds on the annihilation cross section via a comparison with observational data. We show that stringent cosmic ray antiproton limits preclude a sizable DM contribution to observed cosmic ray positron fluxes in the class of models for which the bremsstrahlung processes dominate.

We recalculated the coupling constants $g_{\varphi \sigma \gamma }$, $g_{\varphi a_0\gamma }$, $g_{\omega \sigma \gamma }$, $g_{a_0\omega \gamma }$, $g_{\rho \sigma \gamma }$, and $g_{a_0\rho \gamma }$ by taking into account the contributions of the three-particle up to twist-4 distribution amplitudes of the photon involving quark-gluon and quark-anti-quark-photon fields in the light-cone sum-rule framework.

We show that in the multi-Higgs extension of minimal supersymmetric standard model, which has $N$-pairs of Higgs doublets (called NHMSSM), it is impossible to break $CP$ spontaneously, if we do not allow for fine-tuning relations between parameters. The result holds true even in the presence of spontaneous $R$-parity breaking.

LHC searches for the standard model Higgs boson in $WW$ or $ZZ$ decay modes place strong constraints on the top-Higgs state predicted in many models with new dynamics preferentially affecting top quarks. Such a state couples strongly to top quarks, and is therefore produced through gluon fusion at a rate enhanced relative to the rate for the standard model Higgs boson. A top-Higgs state with mass less than 300 GeV is excluded at 95% C.L. if the associated top-pion has a mass of 150 GeV, and the constraint is even stronger if the mass of the top-pion state exceeds the top-quark mass or if the top-pion decay constant is a substantial fraction of the weak scale. These results have significant implications for theories with strong top dynamics, such as topcolor-assisted technicolor, top-seesaw models, and certain Higgsless models.

In this paper we reexamine how to utilize the previous proposed color-octet axial-vector boson $Z_{\mathrm{C}}$ to explain the $3.4\sigma$ anomaly of $t\overline{t}$ forward-backward (FB) asymmetry $A_{\mathrm{FB}}$ for $m_{t\overline{t}}>450\mathrm{GeV}$ observed by CDF. Our numerical results indicate that the best-fit parameters are $g_A^q=0.07$, $g_A^Q=3$, and $M_{\mathrm{C}}=440\mathrm{GeV}$, which are obtained by fitting the mass dependent $A_{\mathrm{FB}}$ and total cross section data provided by a recent CDF measurement. Here $g_A^q(g_A^Q)$ and $M_{\mathrm{C}}$ are the axial couplings among $Z_{\mathrm{C}}$ with the first two (the third) generation quarks, and $Z_{\mathrm{C}}$ mass, respectively. We also calculate one-side forward-backward asymmetry $A_{\mathrm{OFB}}$ for top and bottom quark pair production at the LHC, focusing on the new contributions from $Z_{\mathrm{C}}$. Our studies show that $A_{\mathrm{OFB}}$ can be utilized to measure the properties of new particle $Z_{\mathrm{C}}$.

We briefly review the need to perform renormalization of inflationary perturbations to properly work out the physical power spectra. We also summarize the basis of (momentum-space) renormalization in curved spacetime and address several misconceptions found in recent literature on this subject.

We perform the stability analysis of the Schwarzschild black hole in $f(R)$ gravity with the parity-violating Chern–Simons (CS) term coupled to a dynamical scalar field $\theta$. For this purpose, we transform the $f(R)$ gravity into the scalar-tensor theory by introducing a scalaron $\varphi$, providing the dynamical CS modified gravity with two scalars. The perturbation equation for the scalar $\theta$ is coupled to the odd-parity metric perturbation equation, providing a system of two coupled second-order equations, while the scalaron is coupled to the even-parity perturbation equation. This implies that the CS coupling affects the Regge–Wheeler equation, while $f(R)$ gravity does not affect the Zerilli equation. It turns out that the Schwarzschild black hole is stable against the external perturbations if the scalaron is free from the tachyon.

We discuss the response of neutron stars to the tidal interaction in a compact binary system, as encoded in the Love number associated with the induced deformation. This problem is of interest for gravitational-wave astronomy as there may be a detectable imprint on the signal from the late stages of binary coalescence. Previous work has focused on simple barotropic neutron star models, providing an understanding of the role of the stellar compactness and overall density profile. We add realism to the discussion by developing the framework required to model stars with varying composition and an elastic crust. These effects are not expected to be significant for the next generation of detectors, but it is nevertheless useful to be able to quantify them. Our results show that (perhaps surprisingly) internal stratification has no impact whatsoever on the Love number. We also show that crust elasticity provides a (predictably) small correction to existing models.

We examine the future sensitivity of CoGeNT to the presence of dark matter streams and find that consideration of streams in the data may lead to differences in the interpretation of the results. We show the allowed particle mass and cross section for different halo parameters, assuming spin-independent elastic scattering. As an example, we choose a stream with the same velocity profile as that of the Sagittarius stream (and in the Solar neighborhood) and find that, with an exposure of $\sim 10\mathrm{kg}\mathrm{yr}$, the CoGeNT results can be expected to exclude the standard-halo-model–only halo in favor of a $\mathrm{\text{standard halo model}}+\mathrm{\text{stream}}$ halo at the 95% (99.7%) confidence level, provided the stream contributes 3% (5%) of the local dark matter density. The presence of a significant stream component may result in incorrect estimates of the particle mass and cross section unless the presence of the stream is taken into account. We conclude that the CoGeNT experiment is sensitive to streams and care should be taken to include the possibility of streams when analyzing experimental results.

Recently type-II seesaw in a supersymmetric$SO(10)$ framework has been found useful in explaining large solar and atmospheric mixing angles as well as a larger value of ${\theta }_{13}$ while unifying quark and lepton masses. An important question in these models is whether there exists consistency between coupling unification and type-II seesaw dominance. Scenarios where this consistency can be demonstrated have been given in a SUSY framework. In this paper we give examples where type-II dominance occurs in $SO(10)$ models without supersymmetry but with additional TeV-scale particles and also in models with split-supersymmetry. Grand unification is realized in a two step process via breaking of $SO(10)$ to $SU(5)$ and then to a TeV-scale standard model supplemented by extra fields and an $SU(5)$ Higgs multiplet ${15}_H$ at a scale of about ${10}^{12}\mathrm{GeV}$ to give a type-II seesaw. The predictions for proton lifetime in these models are in the range ${\tau }_p^0=2\times {10}^{35}\mathrm{yrs}$. to $6\times {10}^{35}\mathrm{yrs}$. A number of recent numerical fits to GUT-scale fermion masses can be accommodated within this model.

A study of meson-baryon systems with total strangeness $-1$ is made within a framework based on the chiral and hidden local symmetries. These systems consist of octet baryons, pseudoscalar and vector mesons. The pseudoscalar meson-baryon (PB) dynamics has been earlier found determinant for the existence of some strangeness $-1$ resonances, for example, $\Lambda (1405)$, $\Lambda (1670)$, etc. The motivation of the present work is to study the effect of coupling the closed vector meson-baryon (VB) channels to these resonances. To do this, we obtain the $\mathrm{PB}\to \mathrm{PB}$ and $\mathrm{VB}\to \mathrm{VB}$ amplitudes from the $t$-channel diagrams and the $\mathrm{PB}\leftrightarrow \mathrm{VB}$ amplitudes are calculated using the Kroll-Ruddermann term where, considering the vector meson dominance phenomena, the photon is replaced by a vector meson. The calculations done within this formalism reveal a very strong coupling of the VB channels to the $\Lambda (1405)$ and $\Lambda (1670)$. In the isospin 1 case, we find evidence for a double pole structure of the $\Sigma (1480)$ which, like the isospin 0 resonances, is also found to couple strongly to the VB channels. The strong coupling of these low-lying resonances to the VB channels can have important implications on certain reactions producing them.

The one-loop quark contribution to the QCD effective potential for the homogeneous Abelian gluon field in the presence of an external strong electromagnetic field is evaluated. The structure of extrema of the potential as a function of the angles between chromoelectric, chromomagnetic, and electromagnetic fields is analyzed. In this setup, the electromagnetic field is considered as an external one while the gluon field represents domain structured nonperturbative gluon configurations related to the QCD vacuum in the confinement phase. Two particularly interesting gluon configurations, (anti-)self-dual and crossed orthogonal chromomagnetic and chromoelectric fields, are discussed specifically. Within this simplified framework it is shown that the strong electromagnetic fields can play a catalyzing role for a deconfinement transition. At the qualitative level, the present consideration can be seen as a highly simplified study of an impact of the electromagnetic fields generated in relativistic heavy ion collisions on the strongly interacting hadronic matter.

The Atlas and CMS groups have both reported an excess of events in the $W{W}^{*}\to {\ell }^{+}{\ell }^{-}+E_T^{\mathrm{miss}}$ search channel, which could be the first evidence for the Higgs boson. In the MSSM, the lightest SUSY Higgs scalar $h$ is expected to occur with mass $m_h\lesssim 135\mathrm{GeV}$, depending on the range of SUSY parameters scanned over. Since the $h\to W{W}^{*}$ branching fraction falls swiftly with decreasing $m_h$, a signal in the $W{W}^{*}$ channel would favor an $h$ at the high end of its predicted mass range. We scan over general GUT scale SUSY model parameters to find those which give rise to $m_h\gtrsim 130\mathrm{GeV}$. A value of $m_0\sim 10–20\mathrm{TeV}$ is favored, with $A_0\sim \pm 2m_0$, while the lower range of $m_{1/2}\lesssim 1\mathrm{TeV}$ is also slightly favored. This gives rise to an ``effective SUSY’’ type of sparticle mass spectrum. For low $m_{1/2}$, gluino pairs may be accessible to LHC searches, while for higher $m_{1/2}$ values, the SUSY spectra would likely be out of range of LHC reach.