We consider a classically scale invariant version of the Standard Model, extended by an extra dark $SU(2{)}_X$ gauge group. Apart from the dark gauge bosons and a dark scalar doublet which is coupled to the Standard Model Higgs through a portal coupling, we incorporate right-handed neutrinos and an additional real singlet scalar field. After symmetry breaking à la Coleman-Weinberg, we examine the multi-Higgs sector and impose theoretical and experimental constraints. In addition, by computing the dark matter relic abundance and the spin-independent scattering cross section off a nucleon we determine the viable dark matter mass range in accordance with present limits. The model can be tested in the near future by collider experiments and direct detection searches such as XENON 1T.

We have computed the Wilsonian effective action in a simple model with a spontaneously broken chiral parity. The Wilsonian running of relevant parameters makes it possible to discuss in a consistent manner the issues of fine-tuning and the stability of the scalar potential. This has been compared with the standard picture based on a Gell-Mann-Low running. Since the Wilsonian running automatically includes integration of heavy degrees of freedom, the running differs markedly from the Gell-Mann-Low version. Similar behavior can be observed: the scalar mass-squared parameter and the quartic coupling can change sign from a positive to a negative one, due to the running which causes a spontaneous symmetry breaking or an instability in the renormalizable part of the potential for a given range of scales. However, care must be taken when drawing conclusions, because of the truncation of higher-dimension operators. Taking the scalar field’s amplitude near the cutoff $\mathrm{\Lambda }$ may cancel the suppression due to the scale, and only the suppression due to small couplings partially justifies the truncation in this region. Also, when taking the cutoff higher, to include larger amplitudes of the fields, the higher-order irrelevant operators, whose coefficients grow with the scale, may affect the conclusion about the stability. The Gell-Mann-Low running allows one to resume relatively easily a class of operators corresponding to large logarithms to the form of the renormalization group equation improved effective potential which is valid over a huge range of scales. In the Wilsonian approach this would correspond to following the running of a large number of irrelevant operators, which is technically problematic. As for the issue of the fine-tuning, since in the Wilsonian approach power-law terms are not subtracted, one can clearly observe the quadratic sensitivity of a fine-tuning measure to the change of the cutoff scale. The Wilsonian version of the radiative symmetry-breaking mechanism has been described.

We attempt to explain the recent ATLAS $3\sigma$ excess of dilepton events with an invariant mass near $Z$ peak through the gluino-mediated sbottom production in a simplified scenario inspired by the minimal supersymmetric Standard Model. The additional $Z$ bosons can be produced through the cascade decay chain $\tilde{g}\to b{\tilde{b}}_1^{†}\to b\overline{b}{\tilde{\chi }}_{2,3}^0\to b\overline{b}{\tilde{\chi }}_1^{0}Z$, in which ${\tilde{b}}_1$ is the right-handed sbottom, ${\tilde{\chi }}_1^0$ is the bino-like lightest supersymmetric particle (LSP) and ${\tilde{\chi }}_{2,3}^0$ are two nearly degenerate Higgsino-like next-to LSPs. Taking into account the constraint from the LHC search for the gluino-mediated sbottom production in the final states with the missing transverse energy and at least three $b$-jets, we find that the ATLAS on-$Z$ excess can only be marginally explained at the $2\sigma$ level. We also note that within the scenario where the gluino predominantly decays to the right-handed stop instead of the sbottom, the excess can hardly be explained, since the $Z$-boson is not produced in the stop dominant decay channel, ${\tilde{t}}_1\to b{\tilde{\chi }}_1^{+}$.

We study the nucleon-pion-state contribution to the QCD two-point function of the standard nucleon interpolating fields. For sufficiently small quark masses these two-particle states are expected to have a smaller total energy than the single-particle excited states. We calculate the nucleon-pion-state contribution to leading order in chiral perturbation theory. Both parity channels are considered. We find the nucleon-pion-state contribution to be small, contributing at the few percent level to the effective mass in the positive parity channel.

We present our result for the $K\to \pi \pi$ decay amplitudes for both the $\mathrm{\Delta }I=1/2$ and $3/2$ processes with the improved Wilson fermion action. Expanding on the earlier works by Bernard et al. and by Donini et al., we show that mixings with four-fermion operators with wrong chirality are absent even for the Wilson fermion action for the parity odd process in both channels due to CPS symmetry. Therefore, after subtraction of an effect from the lower dimensional operator, a calculation of the decay amplitudes is possible without complications from operators with wrong chirality, as for the case with chirally symmetric lattice actions. As a first step to verify the possibility of calculations with the Wilson fermion action, we consider the decay amplitudes at an unphysical quark mass $m_K\sim 2m_{\pi }$. Our calculations are carried out with $N_f=2+1$ gauge configurations generated with the Iwasaki gauge action and nonperturbatively $O(a)$-improved Wilson fermion action at $a=0.091\mathrm{fm}$, $m_{\pi }=280\mathrm{MeV}$, and $m_K=580\mathrm{MeV}$ on a ${32}^3\times 64$ ($La=2.9\mathrm{fm}$) lattice. For the quark loops in the penguin and disconnected contributions in the $I=0$ channel, the combined hopping parameter expansion and truncated solver method work very well for variance reduction. We obtain, for the first time with a Wilson-type fermion action, that $\mathrm{Re}{A}_0=60(36)\times 10^{-8}\mathrm{GeV}$ and $\mathrm{Im}{A}_0=-67(56)\times 10^{-12}\mathrm{GeV}$ for a matching scale $q^{*}=1/a$. The dependence on the matching scale $q^{*}$ for these values is weak.

Using abundant experimental information about charmed mesons together with recent research, we systematically study higher radial and orbital excitations in the charmed meson family by analyzing the mass spectrum and by calculating their Okubo-Zweig-Iizuka-allowed two-body decay behaviors. This phenomenological analysis reveals underlying properties of the newly observed charmed states $D(2550)$, $D^{*}(2600)$, $D^{*}(2760)$, $D(2750)$, $D_J(2580)$, $D_J^{*}(2650)$, $D_J^{*}(2760)$, $D_J(2740)$, $D_J(3000)$, and $D_J^{*}(3000)$ to provide valuable information about the charmed mesons still missing in experiments.

Relativistic light-front bound-state equations for mesons and baryons can be constructed in the chiral limit from the supercharges of a superconformal algebra which connect baryon and meson spectra. Quark masses break the conformal invariance, but the basic underlying supersymmetric mechanism, which transforms meson and baryon wave functions into each other, still holds and gives remarkable connections across the entire spectrum of light and heavy-light hadrons. We also briefly examine the consequences of extending the supersymmetric relations to double-heavy mesons and baryons.

Using the experimental data from the STAR, PHENIX, ALICE, and CMS programs on the rapidity and energy dependence of the $p_T$ spectra in $p+p$ collisions, we show that a universal distribution exists. The energy dependence of temperature $T$ and parameter $n$ of the Tsallis distribution are also discussed in detail. A cascade particle production mechanism in $p+p$ collisions is proposed.

We discuss the two-photon coupling of the lightest scalar meson on the basis of an extension of $\chi \mathrm{PT}$. Using low-energy data on the pion form factor and the $\gamma \gamma \to {\pi }^{+}{\pi }^{-}({\pi }^0{\pi }^0)$ cross sections as inputs, we find $\mathrm{\Gamma }(\sigma \to \gamma \gamma )\cong 0.126\mathrm{keV}$. The smallness of the result and the relative weight between its components, $\frac{{\mathrm{\Gamma }}_{\gamma \gamma \to S_1}}{\mathrm{\Gamma }\gamma \gamma \to \pi \pi \to S_1}\le 1$, suggests that the scalar $0^{++}$ meson is mainly a $Q^2{\overline{Q}}^2$ state.

The production of quark-antiquark pairs along a color flux tube precedes the fragmentation of the tube. Because of local conservation laws, the production of a $q\text{−}\overline{q}$ pair will lead to correlations of adjacently produced mesons (mostly pions). Adjacently produced mesons however can be signalled by their rapidity difference $\mathrm{\Delta }y$ falling within the window of $|\mathrm{\Delta }y|\lesssim 1/(dN/dy)$, on account of the space-time-rapidity ordering of produced mesons in a flux-tube fragmentation. Therefore, the local conservation laws of momentum, charge, and flavor will lead to a suppression of the angular correlation function $dN/(d\mathrm{\Delta }\varphi d\mathrm{\Delta }y)$ for two mesons with opposite charges or strangeness on the near side at $(\mathrm{\Delta }\varphi ,\mathrm{\Delta }y)\sim 0$, but an enhanced correlation on the back-to-back, away side at $\mathrm{\Delta }\varphi \sim \pi$, within the window of $|\mathrm{\Delta }y|\lesssim 1/(dN/dy)$. These properties can be used as signatures for the fragmentation of a color flux tube. The gross features of the signature of flux-tube fragmentation for two oppositely charged mesons are qualitatively consistent with the STAR and NA61/SHINE angular correlation data for two hadrons with opposite charges in the low-$p_T$ region in high-energy $pp$ collisions.

The recent astronomical observation of GeV gamma-ray excess from the Galactic center was suggested due to a $b\overline{b}$ mode in the tens GeV of weakly interacting massive particle (WIMP) pair annihilations, and this mode was also explored by the new dwarf galaxy observation. Considering the case where the WIMP pair mass is below the top quark mass, a pseudoscalar $\varphi$ is studied in this article, which mediates the interactions between the standard model fermions and fermionic WIMPs and the neutral flavor-changing interactions in standard model fermion sectors. The $b\overline{b}$ mode is favored in WIMP pair annihilations, while the WIMP-nucleus scattering is highly suppressed in direct detection. Alternative schemes of $t\to c$ decay and single top production are employed to search the WIMPs. Assuming the mass of the WIMPs is around 5–60 GeV and with reasonable inputs by the constraints, the branching ratio ${\mathcal{B}}_{t\to c\overline{\chi }\chi }$ of a top quark decaying into a charm quark and a WIMP pair is derived of order $10^{-8}–10^{-5}$; thus, careful studies in the future on top physics may help to gain a better understanding of WIMPs.

We show that the parity of the $hZ\gamma$ vertex can be probed by interference between the gluon fusion Higgs production, $gg\to h\to \gamma Z\to \gamma {\ell }^{+}{\ell }^{-}$, and the background, $gg\to \gamma Z\to \gamma {\ell }^{+}{\ell }^{-}$, amplitudes. In the presence of a parity violating $hZ\gamma$ vertex, this interference alters the kinematic distribution of the leptons and photon compared to Standard Model (SM) expectations. For a Higgs with SM-sized width and couplings, we find that the size of the effect enters at most at the $10^{-2}$ level. Such a small effect cannot be seen at the LHC, even with futuristic high luminosities. Should there exist other broader scalar particles with larger production cross-section times branching ratio to $Z\gamma$, then the parity structure of their $Z\gamma$ couplings can be probed with this technique.

We develop a theory describing the superfield extension of the two-form field coupled to the usual chiral and real scalar superfield and find the one-loop Kählerian effective potential in this theory.

The proposed analogy between hadron production in high-energy collisions and Hawking-Unruh radiation process in the black holes shall be extended. This mechanism provides a theoretical basis for the freeze-out parameters, the temperature ($T$), and the baryon chemical potential ($\mu$), characterizing the final state of particle production. The results from charged black holes, in which the electric charge is related to $\mu$, are found comparable with the phenomenologically deduced parameters from the ratios of various particle species and the higher-order moments of net-proton multiplicity in thermal statistical models and Polyakov linear-sigma model. Furthermore, the resulting freeze-out condition $⟨E⟩/⟨N⟩\simeq 1\mathrm{GeV}$ for average energy per particle is in good agreement with the hadronization process in the high-energy experiments. For the entropy density ($s$), the freeze-out condition $s/T^3\simeq 7$ is found at $\mu \lesssim 0.3\mathrm{GeV}$. Then, due to the dependence of $T$ on $\mu$, the values of $s/T^3$ increase with increasing $\mu$. In accordance with this observation, we found that the entropy density ($s$) remains constant with increasing $\mu$. Thus, we conclude that almost no information is going lost through Hawking-Unruh radiation from charged black holes. It is worthwhile to highlight that the freeze-out temperature from charged black holes is determined independent on both freeze-out conditions.

Black hole jet power depends on the angular velocity of magnetic field lines, ${\mathrm{\Omega }}_F$. Force-free black hole magnetospheres typically have ${\mathrm{\Omega }}_F/{\mathrm{\Omega }}_H\approx 0.5$, where ${\mathrm{\Omega }}_H$ is the angular velocity of the horizon. We give a streamlined proof of this result using an extension of the classical black hole membrane paradigm. The proof is based on an impedance-matching argument between membranes at the horizon and infinity. Then we consider a general relativistic magnetohydrodynamic simulation of an accreting, spinning black hole and jet. We find that the theory correctly describes the simulation in the jet region. However, the field lines threading the horizon near the equator have much smaller ${\mathrm{\Omega }}_F/{\mathrm{\Omega }}_H$ because the force-free approximation breaks down in the accretion flow.

We find the explicit forms of the anti–de Sitter plane, anti–de Sitter spherical, and pp waves that solve both the linearized and exact field equations of the most general higher derivative gravity theory in three dimensions. As a subclass, we work out the six-derivative theory and the critical version of it where the masses of the two spin-2 excitations vanish and the spin-0 excitations decouple.

In this work, we show that regular black holes in a Randall-Sundrum-type brane world model are generated by the nonlocal bulk influence, expressed by a constant parameter in the brane metric, only in the spherical case. In the axial case (black holes with rotation), this influence forbids them. A nonconstant bulk influence is necessary to generate regular black holes with rotation in this context.

Quantum gravity corrections to accretion onto a Schwarzschild black hole are considered in the context of the asymptotically safe scenario. The possible positions of the critical points are discussed and the general conditions for critical points are obtained. The explicit expressions for the matter density compression and the temperature profile, both below the critical radius and at the event horizon, are derived. For polytropic matter, we determine the corrected temperature and the integrated flux resulting from quantum gravity effects at the event horizon, which might be considered as a test of the asymptotically safe scenario.

It has been suggested that several small-scale structure anomalies in $\mathrm{\Lambda }\mathrm{CDM}$ cosmology can be solved by strong self-interaction between dark matter particles. It was shown by Braaten and Hammer [Phys. Rev. D 88, 063511 (2013)] that the presence of a near threshold S-wave resonance can make the scattering cross section at nonrelativistic speeds come close to saturating the unitarity bound. This can result in the formation of a stable bound state of two asymmetric dark matter particles (which we call darkonium). The work of Laha and Braaten [Phys. Rev. D, 89, 103510 (2014)] studied the nuclear recoil energy spectrum in dark matter direct detection experiments due to this incident bound state. Here we study the angular recoil spectrum and show that it is uniquely determined up to normalization by the S-wave scattering length. Observing this angular recoil spectrum in a dark matter directional detection experiment will uniquely determine many of the low-energy properties of dark matter independent of the underlying dark matter microphysics.

Does the observable spectrum of cosmic fluctuations depend on detailed initial conditions? This addresses the question if the general inflationary paradigm is sufficient to predict within a given model the spectrum and amplitude of cosmic fluctuations, or if additional particular assumptions about the initial conditions are needed. The answer depends on the number of $e$-foldings $N_{\text{in}}$ between the beginning of inflation and horizon crossing of the observable fluctuations. We discuss an interacting inflaton field in an arbitrary homogeneous and isotropic geometry, employing the quantum effective action $\mathrm{\Gamma }$. An exact time evolution equation for the correlation function involves the second functional derivative ${\mathrm{\Gamma }}^{(2)}$. The operator formalism and quantum vacua for interacting fields are not needed. Use of the effective action also allows one to address the change of frames by field transformations (field relativity). Within the approximation of a derivative expansion for the effective action we find the most general solution for the correlation function, including mixed quantum states. For not too large $N_{\text{in}}$ the memory of the initial conditions is preserved. In this case the cosmic microwave background cannot disentangle between the initial spectrum and its processing at horizon crossing. The inflaton potential cannot be reconstructed without assumptions about the initial state of the universe. We argue that for very large $N_{\mathrm{in}}$ a universal scaling form of the correlation function is reached for the range of observable modes. This can be due to symmetrization and equilibration effects, not yet contained in our approximation, which drive the short distance tail of the correlation function toward the Lorentz invariant propagator in flat space.