Within the perturbative QCD approach, we recalculate the branching ratio and polarization fractions of the pure annihilation decay $B\to \varphi \varphi$ in both the standard model and the family nonuniversal $Z^{\prime }$ model. We find that this decay is dominated by the longitudinal part, while the transverse parts are negligibly due to the absence of the $(S-P)(S+P)$-type operator. In the standard model, the branching ratio is predicted as $({4.4}_{-0.6-0.5}^{+0.8+0.3})\times {10}^{-8}$, which is larger than the previous predictions. With an additional $Z^{\prime }$ boson, the branching ratio can be enhanced by a factor of 2 or reduced one-half in the allowed parameter space. These results will be tested by the ongoing LHCb experiment and forthcoming Super-$B$ experiments.

The effects of gluon radiation by charm quarks on the transport coefficients, e.g., drag, longitudinal and transverse diffusions, and shear viscosity, have been studied within the ambit of perturbative quantum chromodynamics and kinetic theory. We found that soft gluon radiation by the charm quark has substantial effects on the transport coefficients. However, the radiative effects on the shape of its equilibrium distribution function is insignificant. We also observe that the shear viscosity to entropy ratio of the quark-gluon plasma is closer to the experimentally extracted value when the gluon radiation by the charm quark is included.

There are two $Z$-peak observables related to the pair production of bottom quarks that show a deviation of about $2.5\sigma$ each from Standard Model expectations. While the discrepancy in the forward-backward asymmetry is a long-standing one, the tension for the second observable, namely the ratio of the partial width for a $Z$ decaying to a pair of bottom quarks to the total hadronic decay width of the $Z$, has recently gone up due to a full two-loop evaluation of the Standard Model contributions. We show how both these discrepancies may be explained in the framework of new physics that couples only to the third generation of quarks. In the paradigm of effective operators, the Wilson coefficients of some of the possible operators are already very tightly constrained by flavor physics data. However, there still remain certain operators, particularly those involving right-chiral quark fields, which can successfully explain the anomalies. We also show how the footprints of such operators may be observed at the upgraded LHC.

The crucial property of particle colliders is their ability to convert (e.g. electrical) energy into the mass of heavy particles. We have become used to the extremely low efficiency of this conversion and the severe limitations on the mass scale of heavy particles that can be reached. In view of this situation, it appears reasonable to ask whether a perfect conversion machine of this type (a perfect “collider”) exists even in principle and whether there is a highest mass scale that can be reached by such a machine. It turns out that, with a number of assumptions, such a machine is conceivable in a world with a strongly coupled, approximately scale-invariant four-dimensional (4D) field theory with five-dimensional (5D) gravity dual. This machine can be realized as a 5D tower built on the IR brane (in Randall-Sundrum model language). Transporting mass to the tip of this tower is, under certain conditions, equivalent to producing heavy pointlike 4D particles. Hence, this can be thought of as a perfect “collider.” In the simple, “pure Randall-Sundrum setting” that we analyze, this machine can only reach a certain maximal energy scale, which falls as the gravity-dual of the 4D quantum field theory (QFT) approaches the strong coupling domain. On these grounds, one might expect that a no-go theorem (in the spirit of that of Carnot for the conversion of heat into work) exists for generic weakly coupled QFTs.

Measuring spectral distortions of the cosmic microwave background (CMB) is attracting considerable attention as a probe of high energy particle physics in the cosmological context, since primordial inflation explorer (PIXIE) and polarized radiation imaging and spectroscopy mission (PRISM) have recently been proposed. In this paper, CMB distortions due to resonant conversions between CMB photons and light axionlike particles (ALPs) are investigated, motivated by the string axiverse scenario which suggests the presence of a plenitude of light axion particles. The distortions due to resonant conversions have a frequency-independent shape, in contrast to $\mu$ and $y$ distortions. Therefore, one can distinguish the distortions due to resonant conversions from $\mu$ and $y$ distortions. Since these resonant conversions depend on the strength of primordial magnetic fields, constraints on CMB distortions can provide an upper limit on the product of the photon-ALP coupling constant $g$ and the comoving strength of primordial magnetic fields $B$. Potentially feasible constraints from PIXIE/PRISM can set a limit $gB\lesssim {10}^{-16}{\mathrm{GeV}}^{-1}\mathrm{nG}$ for ALP mass $m_{\varphi }\lesssim {10}^{-14}\mathrm{eV}$. Although this result is not a direct constraint on $g$ and $B$, it is significantly tighter than the product of the current upper limits on $g$ and $B$.

Recently a quantum portrait of black holes was suggested according to which a macroscopic black hole is a Bose–Einstein condensate of soft gravitons stuck at the critical point of a quantum phase transition. We explain why quantum criticality and instability are the key for an efficient generation of entanglement and consequently of the scrambling of information. By studying a simple Bose–Einstein prototype, we show that the scrambling time, which is set by the quantum break time of the system, goes as $\log N$ for $N$ the number of quantum constituents or equivalently the black hole entropy.

It can be easily shown that bound orbits around a static source can only exist in four dimensions for any force driven by the Laplace equation. This is true not only for Maxwell’s electromagnetism and Newton’s gravity, but for Einstein’s theory of gravitation as well. In contrast to Maxwell’s electrodynamics and Newton’s gravity, general relativity has a natural and remarkable generalization in higher dimensions in Lovelock gravity. However, it is not Laplace driven and hence admits bound orbits around a static black hole in all even $D=2N+2$ dimensions, where $N$ is the degree of the Lovelock polynomial action. This is as general a result as Bertrand’s theorem of classical mechanics, in which the existence of closed orbits uniquely singles out the inverse square law for a long-range central force.

Gravitational waves radiated by the coalescence of compact-object binaries containing a neutron star and a black hole are one of the most interesting sources for the ground-based gravitational-wave observatories Advanced LIGO and Advanced Virgo. Advanced LIGO will be sensitive to the inspiral of a $1.4M_{\odot }$ neutron star into a $10M_{\odot }$ black hole to a maximum distance of $\sim 900\mathrm{Mpc}$. Achieving this sensitivity and extracting the physics imprinted in observed signals requires accurate modeling of the binary to construct template waveforms. In a neutron-star–black-hole binary, the black hole may have significant angular momentum (spin), which affects the phase evolution of the emitted gravitational waves. We investigate the ability of currently available post-Newtonian templates to model the gravitational waves emitted during the inspiral phase of neutron-star–black-hole binaries. We restrict to the case where the spin of the black hole is aligned with the orbital angular momentum and compare several post-Newtonian approximants. We examine restricted amplitude post-Newtonian waveforms that are accurate to third-and-a-half post-Newtonian order in the orbital dynamics and complete to second-and-a-half post-Newtonian order in the spin dynamics. We also consider post-Newtonian waveforms that include the recently derived third-and-a-half post-Newtonian order spin-orbit correction and the third post-Newtonian order spin-orbit tail correction. We compare these post-Newtonian approximants to the effective-one-body waveforms for spin-aligned binaries. For all of these waveform families, we find that there is a large disagreement between different waveform approximants, starting at low to moderate black hole spins, particularly for binaries where the spin is antialigned with the orbital angular momentum. The match between the TaylorT4 and TaylorF2 approximants is $\sim 0.8$ for a binary with $m_{\mathrm{BH}}/m_{\mathrm{NS}}\sim 4$ and ${\chi }_{\mathrm{BH}}=c{J}_{\mathrm{BH}}/G{m}_{\mathrm{BH}}^2\sim 0.4$. We show that the divergence between the gravitational waveforms begins in the early inspiral at $v\sim 0.2$ for ${\chi }_{\mathrm{BH}}\sim 0.4$. Post-Newtonian spin corrections beyond those currently known will be required for optimal detection searches and to measure the parameters of neutron-star–black-hole binaries. The strong dependence of the gravitational-wave signal on the spin dynamics will make it possible to extract significant astrophysical information from detected systems with Advanced LIGO and Advanced Virgo.

We revisit the method of using the photon-graviton conversion mechanism in the presence of the external magnetic field to probe small-scale primordial magnetic fields that may exist between the last scattering surface and the present. Specifically, we investigate impacts on the conversion efficiency due to the presence of matter, including the plasma collective effect and the atomic polarizability. In general, these effects tend to reduce the conversion probability. Under this more realistic picture and based on the precision of Cosmic Background Explorer’s measurement of the cosmic microwave background (CMB) blackbody spectrum, we find an upper bound for the primordial magnetic field strength, $B\lesssim 30\mathrm{G}$, at the time of recombination. Although at present the bound based on the photon-graviton conversion mechanism is not as tight as that obtained by the direct use of CMB temperature anisotropy, it nevertheless provides an important independent constraint on primordial magnetic fields and at epochs in addition to the recombination. The bound can be significantly improved if the CMB blackbody spectrum measurement becomes more precise in future experiments such as Primordial Inflation Explorer.

Direct dark matter detection focuses on elastic scattering of dark matter particles off nuclei. In this study, we explore inelastic scattering where the nucleus is excited to a low-lying state of 10–100 keV, with subsequent prompt deexcitation. We calculate the inelastic structure factors for the odd-mass xenon isotopes based on state-of-the-art shell-model calculations and chiral effective field theory for the interaction of weakly interacting massive particles with nucleons. For these cases, we find that the inelastic channel is comparable to or can dominate the elastic channel for momentum transfers around 150 MeV. We calculate the inelastic recoil spectra in the standard halo model, compare these to the elastic case, and discuss the expected signatures in a xenon detector, along with implications for existing and future experiments. The combined information from elastic and inelastic scattering will allow for the determination of the dominant interaction channel within one experiment. In addition, the two channels probe different regions of the dark matter velocity distribution and can provide insight into the dark halo structure. The allowed recoil energy domain and the recoil energy at which the integrated inelastic rates start to dominate the elastic channel depend on the mass of the dark matter particle, thus providing a potential handle to constrain its mass.

We show how a strongly coupled lattice theory consisting of just fermions and gauge fields can exhibit a dynamical Higgs mechanism through the formation of a gauge-invariant four-fermion condensate. Furthermore, we argue that this lattice Higgs phase may survive into the continuum limit.

Axial charge in a QCD plasma is P- and $CP$-odd. We propose and study P- and $CP$-odd observables in photon and dilepton emissions from an axially charged QCD plasma, which may provide possible experimental evidences of axial charge fluctuation and triangle anomaly in the plasma created in heavy-ion collisions. Our observables measure spin alignments of the emitted photons and dileptons, and are shown to be related to the imaginary part of chiral magnetic conductivity at finite frequency-momentum, which ultimately arises from the underlying triangle anomaly of the QCD plasma with a finite axial charge density. We present an exemplar computation of these observables in a strongly coupled regime using AdS/CFT correspondence.

An optical ring cavity is used to place the first laboratory constraints on parity-odd nonrenormalizable Lorentz violation. Variations in resonant frequencies are limited to parts in $10^{15}$. Absolute sensitivity to Lorentz-violating operators of mass dimension 6 is improved by a factor of a million over existing parity-even microwave-cavity bounds. Sensitivity to dimension-8 violations is improved by 14 orders of magnitude.

We present a reinterpretation of CMS searches for type-III seesaw lepton triplets at the LHC, both for the normal and the inverse seesaw. We find that, in contrast with previous expectations, these searches in the trilepton final state have a good sensitivity to triplets with predominant coupling to the $\tau$ lepton. We also show that the limits resulting from direct searches can be neatly presented for arbitrary masses and general flavor mixings. Thus, it turns out that the common (and often unrealistic) simplifying assumptions about the flavor couplings of the triplets used by experimental collaborations to present their results are unnecessary and should be dropped.

Rapidity distributions are presented for events containing either a $Z$ boson or a photon with a single jet in proton-proton collisions produced at the CERN LHC. The data, collected with the CMS detector at $\sqrt{s}=7\mathrm{TeV}$, correspond to an integrated luminosity of $5.0{\mathrm{fb}}^{-1}$. The individual rapidity distributions of the boson and the jet are consistent within 5% with expectations from perturbative QCD. However, QCD predictions for the sum and the difference in rapidities of the two final-state objects show discrepancies with CMS data. In particular, next-to-leading-order QCD calculations, and two common Monte Carlo event generators using different methods to match matrix-element partons with parton showers, appear inconsistent with the data as well as with each other.

Doubly special relativity provides an intriguing scenario for studying possible modifications of special relativity. To the leading order of quantum corrections, the scenario is characterized simply by several free parameters in boost generators, dispersion relation and momentum addition law. In this scenario, we work out finite-boost transformations in $3+1$ dimensions. Constraints on parameters are obtained from compatibility analysis, in agreement with other studies. Combining two successive noncollinear boosts, we also obtain the Wigner rotation angle in this scenario. Our analysis is restricted mainly to the case of the commutative addition law.

The lighter mass eigenstate (${\tilde{t}}_1$) of the two top squarks, the scalar superpartners of the top quark, is extremely difficult to discover if it is almost degenerate with the lightest neutralino (${\tilde{\chi }}_1^0$), the lightest stable supersymmetric particle in the R-parity conserving supersymmetry. The current experimental bound on ${\tilde{t}}_1$ mass in this scenario stands only around 200 GeV. For such a light ${\tilde{t}}_1$, the heavier top squark (${\tilde{t}}_2$) can also be around the TeV scale. Moreover, the high value of the Higgs ($h$) mass prefers the left- and right-handed top squarks to be highly mixed, allowing the possibility of a considerable branching ratio for ${\tilde{t}}_2\to {\tilde{t}}_{1}h$ and ${\tilde{t}}_2\to {\tilde{t}}_{1}Z$. In this paper, we explore the above possibility together with the pair production of ${\tilde{t}}_2$ ${\tilde{t}}_2^{*}$, giving rise to the spectacular $\mathrm{\text{diboson}}+\mathrm{\text{missing}}$ transverse energy final state. For an approximately 1 TeV ${\tilde{t}}_2$ and a few hundred GeV ${\tilde{t}}_1$ the final state particles can be moderately boosted, which encourages us to propose a novel search strategy employing the jet substructure technique to tag the boosted $h$ and $Z$. The reconstruction of the $h$ and $Z$ momenta also allows us to construct the stransverse mass $M_{T2}$, providing an additional efficient handle to fight the backgrounds. We show that a $4–5\sigma$ signal can be observed at the 14 TeV LHC for $\sim 1\mathrm{TeV}$ ${\tilde{t}}_2$ with $100{\mathrm{fb}}^{-1}$ integrated luminosity.

We study the effect of disorder in a holographic superconductor by introducing a quasiperiodic chemical potential. When the condensation of the superconductor is sufficiently small compared with the strength of disorder, we find that there exists a discontinuous phase transition from superconducting state to normal state with increasing disorder strength. For relatively large condensation, we find that disorder suppresses but does not completely destroy superconductivity.

We study the two-point correlation function of density perturbations in a spherically symmetric void universe model which does not employ the Copernican principle. First we solve perturbation equations in the inhomogeneous universe model and obtain density fluctuations by using a method of nonlinear perturbation theory which was adopted in our previous paper. From the obtained solutions, we calculate the two-point correlation function and show that it has a local anisotropy at the off-center position, differently from those in homogeneous and isotropic universe models. This anisotropy is caused by the tidal force in the off-center region of the spherical void. Since no tidal force exists in homogeneous and isotropic universe models, we may test the inhomogeneous universe by observing statistical distortion of the two-point galaxy correlation function.