The QCD phase diagram is studied in the presence of an isospin asymmetry using continuum extrapolated staggered quarks with physical masses. In particular, we investigate the phase boundary between the normal and the pion condensation phases and the chiral/deconfinement transition. The simulations are performed with a small explicit breaking parameter in order to avoid the accumulation of zero modes and thereby stabilize the algorithm. The limit of vanishing explicit breaking is obtained by means of an extrapolation, which is facilitated by a novel improvement program employing the singular value representation of the Dirac operator. Our findings indicate that no pion condensation takes place above $T\approx 160\mathrm{MeV}$ and also suggest that the deconfinement crossover continuously connects to the BEC-BCS crossover at high isospin asymmetries. The results may be directly compared to effective theories and model approaches to QCD.

We construct the relativistic chiral Lagrangians with decuplet baryons up to the order $\mathcal{O}(p^4)$ (one loop). For the meson-decuplet-decuplet couplings, there are 1, 13, 55, and 548 terms in the $\mathcal{O}(p^1)-\mathcal{O}(p^4)$ order Lagrangians, respectively. For the meson-octet-decuplet Lagrangians, the number of independent terms from $\mathcal{O}(p^1)$ to $\mathcal{O}(p^4)$ is 1, 5, 67, and 611, respectively. For convenience of application, the $\pi \mathrm{\Delta }\mathrm{\Delta }$ and $\pi N\mathrm{\Delta }$ chiral Lagrangians are picked out. This new form of $\mathrm{\Delta }$ Lagrangians is equivalent to the original isovector-isospinor one, and we establish relations between these two forms.

The production of large $p_T$ dileptons and photons originating from photoproduction processes in p-p collisions at Large Hadron Collider energies is calculated. The comparisons between the exact treatment results and the ones of the equivalent photon approximation approach are expressed as the $Q^2$ (the virtuality of photon) and $p_T$ distributions. The method developed by Martin and Ryskin is used for avoiding double counting when the coherent and incoherent contributions are considered simultaneously. The numerical results indicate that the equivalent photon approximation is only effective in small $Q^2$ region and can be used for coherent photoproduction processes with proper choice of $Q_{\max }^2$ (the choices $Q_{\max }^2\sim \widehat{s}$ or $\infty$ will cause obvious errors), but cannot be used for incoherent photoproduction processes. The exact treatment is needed to deal accurately with the photoproduction of large $p_T$ dileptons and photons.

We present a detailed study of the subtle interplay transpiring at the level of two integral equations that are instrumental for the dynamical generation of a gluon mass in pure Yang-Mills theories. The main novelty is the joint treatment of the Schwinger-Dyson equation governing the infrared behavior of the gluon propagator and of the integral equation that controls the formation of massless bound-state excitations, whose inclusion is instrumental for obtaining massive solutions from the former equation. The self-consistency of the entire approach imposes the requirement of using a single value for the gauge coupling entering in the two key equations; its fulfilment depends crucially on the details of the three-gluon vertex, which contributes to both of them, but with different weight. In particular, the characteristic suppression of this vertex at intermediate and low energies enables the convergence of the iteration procedure to a single gauge coupling, whose value is reasonably close to that extracted from related lattice simulations.

In this work we study temporal quantum correlations, quantified by Leggett-Garg (LG) and LG-type inequalities, in the $B$ and $K$ meson systems. We use the tools of open quantum systems to incorporate the effect of decoherence which is quantified by a single phenomenological parameter. The effect of $CP$ violation is also included in our analysis. We find that the LG inequality is violated for both $B$ and $K$ meson systems, the violation being most prominent in the case of $K$ mesons and least for $B_s$ system. Since the systems with no coherence do not violate LGI, incorporating decoherence is expected to decrease the extent of violation of LGI and is clearly brought out in our results. We show that the expression for the LG functions depends upon an additional term, apart from the experimentally measurable meson transition probabilities. This term vanishes in the limit of zero decoherence. On the other hand, the LG-type parameter can be directly expressed in terms of transition probabilities, making it a more appropriate observable for studying temporal quantum correlations in neutral meson systems.

We revisit rare radiative leptonic decays $B_{s,d}\to \gamma e^{+}{e}^{-}$ and $B_{s,d}\to \gamma {\mu }^{+}{\mu }^{-}$ in the standard model and provide the updated estimates for various differential distributions (the branching ratios, the forward-backward asymmetry, and $R_{\mu /e}$, the ratio of the differential distribution for muons over electrons in the final state). The new ingredients of this work compared to the existing theoretical analyses are the following: (i) we calculate all $B_d\to \gamma$ and $B_s\to \gamma$ form factors induced by the vector, axial-vector, tensor and pseudotensor quark currents within the relativistic dispersion approach based on the constituent quark picture; (ii) we perform a detailed analysis of the charm-loop contributions to radiative leptonic decays: we obtain constraints imposed by electromagnetic gauge invariance and discuss the existing ambiguities in the charmonia contributions.

The factorization theorem for organizing multiple electroweak boson emissions at future colliders with energy far above the electroweak scale is formulated. Taking the inclusive muon-pair production in electron-positron collisions as an example, we argue that the summation over isospins is demanded for constructing the universal distributions of leptons and gauge bosons in an electron. These parton distributions are shown to have the same infrared structure in the phases of broken and unbroken electroweak symmetry, an observation consistent with the Goldstone equivalence theorem. The electroweak factorization of processes involving protons is sketched, with an emphasis on the subtlety of the scalar distributions. This formalism, in which electroweak shower effects are handled from the viewpoint of factorization theorem for the first time, is an adequate framework for collider physics at ultra high energy.

Neutrons produced by cosmic ray muons are an important background for underground experiments studying neutrino oscillations, neutrinoless double beta decay, dark matter, and other rare-event signals. A measurement of the neutron yield in the three different experimental halls of the Daya Bay Reactor Neutrino Experiment at varying depth is reported. The neutron yield in Daya Bay’s liquid scintillator is measured to be $Y_n=(10.26\pm 0.86)\times {10}^{-5}$, $(10.22\pm 0.87)\times {10}^{-5}$, and $(17.03\pm 1.22)\times {10}^{-5}{\mu }^{-1}{\mathrm{g}}^{-1}{\mathrm{cm}}^2$ at depths of 250, 265, and 860 meters-water-equivalent. These results are compared to other measurements and the simulated neutron yield in Fluka and Geant4. A global fit including the Daya Bay measurements yields a power law coefficient of $0.77\pm 0.03$ for the dependence of the neutron yield on muon energy.

The process $e^{+}{e}^{-}\to D_s^{*+}{D}_{s0}^{*}(2317{)}^{-}+\mathrm{c}.\mathrm{c}.$ is observed for the first time with the data sample of $567{\mathrm{pb}}^{-1}$ collected with the BESIII detector operating at the BEPCII collider at a center-of-mass energy $\sqrt{s}=4.6\mathrm{GeV}$. The statistical significance of the $D_{s0}^{*}(2317{)}^{\pm }$ signal is $5.8\sigma$ and the mass is measured to be $(2318.3\pm 1.2\pm 1.2)\mathrm{MeV}/c^2$. The absolute branching fraction $\mathcal{B}(D_{s0}^{*}(2317{)}^{\pm }\to {\pi }^0{D}_s^{\pm })$ is measured as ${1.00}_{-0.14}^{+0.00}(\text{stat}{)}_{-0.14}^{+0.00}(\text{syst})$ for the first time. The uncertainties are statistical and systematic, respectively.

In the first part of the paper we generalize the butterfly velocity formula to anisotropic spacetime. We apply the formula to evaluate the butterfly velocities in M-branes, D-branes, and strings backgrounds. We show that the butterfly velocities in M2-branes, M5-branes and the intersection $\mathrm{M}2\perp \mathrm{M}5$ equal to those in fundamental strings, D4-branes and the intersection $\mathrm{F}1\perp \mathrm{D}4$ backgrounds, respectively. These observations lead us to conjecture that the butterfly velocity is generally invariant under a double-dimensional reduction. In the second part of the paper, we study the butterfly velocity for Einstein-Gauss-Bonnet gravity with arbitrary matter fields. A general formula is obtained. We use this formula to compute the butterfly velocities in different backgrounds and discuss the associated properties.

Future space-based tests of relativistic gravitation—laser ranging to Phobos, accelerometers in orbit, and optical networks surrounding Earth—will constrain the theory of gravity with unprecedented precision by testing the inverse-square law, the strong and weak equivalence principles, and the deflection and time delay of light by massive bodies. In this paper, we estimate the bounds that could be obtained on alternative gravity theories that use screening mechanisms to suppress deviations from general relativity in the Solar System: chameleon, symmetron, and Galileon models. We find that space-based tests of the parametrized post-Newtonian parameter $\gamma$ will constrain chameleon and symmetron theories to new levels, and that tests of the inverse-square law using laser ranging to Phobos will provide the most stringent constraints on Galileon theories to date. We end by discussing the potential for constraining these theories using upcoming tests of the weak equivalence principle, and conclude that further theoretical modeling is required in order to fully utilize the data.

In response to LIGO’s observation of GW170104, we performed a series of full numerical simulations of binary black holes, each designed to replicate likely realizations of its dynamics and radiation. These simulations have been performed at multiple resolutions and with two independent techniques to solve Einstein’s equations. For the nonprecessing and precessing simulations, we demonstrate the two techniques agree mode by mode, at a precision substantially in excess of statistical uncertainties in current LIGO’s observations. Conversely, we demonstrate our full numerical solutions contain information which is not accurately captured with the approximate phenomenological models commonly used to infer compact binary parameters. To quantify the impact of these differences on parameter inference for GW170104 specifically, we compare the predictions of our simulations and these approximate models to LIGO’s observations of GW170104.

We consider spinning generalizations of the Ellis wormhole in scalar-tensor theory. Analogous to other compact objects, these wormholes can carry a nontrivial scalarization. We determine the domain of existence of the scalarized wormholes and investigate the effect of the scalarization on their properties. Depending on the choice of the coupling function, they may possess multiple throats and equators in the Jordan frame, while possessing only a single throat in the Einstein frame.

We investigate a compelling model of quintessential inflation in the context of $\alpha$-attractors, which naturally result in a scalar potential featuring two flat regions; the inflationary plateau and the quintessential tail. The “asymptotic freedom” of $\alpha$-attractors, near the kinetic poles, suppresses radiative corrections and interactions, which would otherwise threaten to lift the flatness of the quintessential tail and cause a 5th-force problem respectively. Since this is a nonoscillatory inflation model, we reheat the Universe through instant preheating. The parameter space is constrained by both inflation and dark energy requirements. We find an excellent correlation between the inflationary observables and model predictions, in agreement with the $\alpha$-attractors setup. We also obtain successful quintessence for natural values of the parameters. Our model predicts potentially sizeable tensor perturbations (at the level of 1%) and a slightly varying equation of state for dark energy, to be probed in the near future.

FASER, ForwArd Search ExpeRiment at the LHC, has been proposed as a small, very far forward detector to discover new, light, weakly-coupled particles. Previous work showed that with a total volume of just $\sim 0.1–1{\mathrm{m}}^3$, FASER can discover dark photons in a large swath of currently unconstrained parameter space, extending the discovery reach of the LHC program. Here we explore FASER’s discovery prospects for dark Higgs bosons. These scalar particles are an interesting foil for dark photons, as they probe a different renormalizable portal interaction and are produced dominantly through $B$ and $K$ meson decays, rather than pion decays, leading to less collimated signals. Nevertheless, we find that FASER is also a highly sensitive probe of dark Higgs bosons with significant discovery prospects that are comparable to, and complementary to, much larger proposed experiments.

A natural possibility for dark matter is that it is composed of the stable pions of a QCD-like hidden sector. Existing literature largely assumes that pion self-interactions alone control the early universe cosmology. We point out that processes involving vector mesons typically dominate the physics of dark matter freeze-out and significantly widen the viable mass range for these models. The vector mesons also give rise to striking signals at accelerators. For example, in most of the cosmologically favored parameter space, the vector mesons are naturally long-lived and produce standard model particles in their decays. Electron and proton beam fixed-target experiments such as HPS, SeaQuest, and LDMX can exploit these signals to explore much of the viable parameter space. We also comment on dark matter decay inherent in a large class of previously considered models and explain how to ensure dark matter stability.

The recently proposed large momentum effective theory (LaMET) of Ji [1] has led to a burst of activity among lattice practitioners to perform and control the first pioneering calculations of the quasi-PDFs of the nucleon. These calculations represent approximations to the standard, exact PDFs defined as correlation functions of fields with lightlike separation, being instead correlations along a longitudinal direction of the operator ${\gamma }^z$; as such, they differ from standard PDFs by a perturbative matching condition with power-suppressed $1/p_z^2$ corrections, becoming exact in the limit $p_z\to \infty$. Investigating the systematics of this behavior thus becomes crucial to understanding the validity of LaMET calculations. While this has been done using models for the nucleon, an analogous dedicated study has not been carried out for the $\pi$ and $\rho$ valence quark distribution functions. Using a constituent quark model, a systematic calculation is performed to estimate the size and $x$ dependence of the finite-$p_z$ effects in these quasi-PDFs, finding them to be potentially tamer for lighter mesons than for the collinear quasi-PDFs of the nucleon.

The variational Hamiltonian approach to quantum chromodynamics in Coulomb gauge is investigated within the framework of the canonical recursive Dyson-Schwinger equations. The dressing of the quark propagator arising from the variationally determined nonperturbative kernels is expanded and renormalized at one-loop order, yielding a chiral condensate compatible with the observations.

Within the framework of the perturbative QCD approach based on $k_T$ factorization, we study 40 $B_c\to DS$ decay modes in the leading order and leading power, where “$S$” stands for the light scalar meson. Under two different scenarios (S1 and S2) for the description of scalar mesons, we explore the branching fractions and related $CP$ asymmetries. As a heavy meson consisting of two heavy quarks with different flavor, the light-cone distribution amplitude of the $B_c$ meson has not been well defined, and therefore the $\delta$ function is adopted. We find that the contributions of emission diagrams are suppressed by the vector decay constants and Cabibbo-Kobayashi-Maskawa elements, and the contributions of annihilation are dominant. After the calculation, we also find that some branching fractions are in the range $[{10}^{-5},{10}^{-4}]$, which could be measured at the current LHCb experiment, and other decays with smaller branching fractions will be tested at high-energy colliders in the future. Furthermore, some decay modes have large $CP$ asymmetries, but they are unmeasurable currently due to the small branching fractions.