The new angular analysis of the decay $B\to K^{*}{\ell }^{+}{\ell }^{-}$ recently presented by the LHCb Collaboration still indicates some tensions with the Standard Model predictions. There are several ongoing analyses to solve the problem of separating hadronic and new physics effects in this decay, but the significance of the observed tensions in the angular observables in $B\to K^{*}{\mu }^{+}{\mu }^{-}$ is still dependent on a theory guesstimate of the hadronic contributions to these decays. Using the new data from LHCb, we offer two tests which make a statistical comparison to determine whether the most favored explanation of the anomalies is new physics or underestimated hadronic effects. We then analyze the usefulness of these tests in two future scenarios. Finally, we update our global fits to all available $b\to s$ data and discuss the impact of the new LHCb measurements.

The ratios among the leading-order (LO) hadronic vacuum polarization (HVP) contributions to the anomalous magnetic moments of an electron, muon, and $\tau$ lepton, $a_{\ell =e,\mu ,\tau }^{\mathrm{HVP},\mathrm{LO}}$, are computed using lattice $\mathrm{QCD}+\mathrm{QED}$ simulations. The results include the effects at order $\mathcal{O}({\alpha }_{em}^2)$ as well as the electromagnetic and strong isospin-breaking corrections at orders $\mathcal{O}({\alpha }_{em}^3)$ and $\mathcal{O}({\alpha }_{em}^2(m_u-m_d))$, respectively, where $(m_u-m_d)$ is the $u$- and $d$-quark mass difference. We employ the gauge configurations generated by the Extended Twisted Mass Collaboration with $N_f=2+1+1$ dynamical quarks at three values of the lattice spacing ($a\simeq 0.062$, 0.082, 0.089 fm) with pion masses in the range $\simeq 210–450\mathrm{MeV}$. The calculations are based on the quark-connected contributions to the HVP in the quenched-QED approximation, which neglects the charges of the sea quarks. The quark-disconnected terms are estimated from results available in the literature. We show that in the case of the electron-muon ratio the hadronic uncertainties in the numerator and in the denominator largely cancel out, while in the cases of the electron-$\tau$ and muon-$\tau$ ratios such a cancellation does not occur. For the electron-muon ratio we get $R_{e/\mu }\equiv (m_{\mu }/m_e{)}^2(a_e^{\mathrm{HVP},\mathrm{LO}}/a_{\mu }^{\mathrm{HVP},\mathrm{LO}})=1.1456(83)$ with an uncertainty of $\simeq 0.7\%$. Our result, which represents an accurate Standard Model (SM) prediction, agrees very well with the estimate obtained using the results of dispersive analyses of the experimental $e^{+}{e}^{-}\to$ hadrons data. Instead, it differs by $\simeq 2.7$ standard deviations from the value expected from present electron and muon ($g-2$) experiments after subtraction of the current estimates of the QED, electroweak, hadronic light-by-light and higher-order HVP contributions, namely $R_{e/\mu }=0.575(213)$. An improvement of the precision of both the experiment and the QED contribution to the electron ($g-2$) by a factor of $\simeq 2$ could be sufficient to reach a tension with our SM value of the ratio $R_{e/\mu }$ at a significance level of $\simeq 5$ standard deviations.

We apply the linear logarithmic relaxation (LLR) method, which generalizes the Wang-Landau algorithm to quantum systems with continuous degrees of freedom, to the fermionic Hubbard model with repulsive interactions on the honeycomb lattice. We compute the generalized density of states of the average Hubbard field and devise two reconstruction schemes to extract physical observables from this result. By computing the particle density as a function of chemical potential we assess the utility of LLR in dealing with the sign problem of this model, which arises away from half filling. We show that the relative advantage over brute-force reweighting grows as the interaction strength is increased and discuss possible future improvements.

The QCD/HQET matching coefficient for the heavy-quark field is calculated up to four loops. It must be finite; this requirement produces analytical results for some terms in the four-loop on-shell heavy-quark field renormalization constant which were previously only known numerically. The effect of a nonzero lighter-flavor mass is calculated up to three loops. A class of on-shell integrals with two masses is analyzed in detail. By specifying our result to QED, we obtain the relation between the electron field and the Bloch–Nordsieck field with four-loop accuracy.

Minijets provide useful information on parton interactions in the low transverse-momentum (low-$p_T$) region. Because minijets produce clusters, we study the clustering properties of produced particles in high-energy $pp$ collisions as a first step to identify minijets. We develop an algorithm to find clusters by using the k-means clustering method, in conjunction with a k-number (cluster number) selection principle in the space of pseudorapidity and azimuthal angles. We test the clustering algorithm using events generated by pythia8.1 for $pp$ collision at $\sqrt{s}=200\mathrm{GeV}$. We find that clustering of low-$p_T$ hadrons occurs in high multiplicity events. However, similar clustering properties are also present for particles produced randomly in a finite pseudorapidity and azimuthal angle space. To distinguish the dynamics from random generations of events, it is necessary to examine the correlation between particles and between clusters. We find that the correlations between clusters may provide a useful tool to distinguish the underlying dynamics of the reaction mechanism.

In this paper, we perform the first simultaneous QCD global analysis of data from semi-inclusive deep inelastic scattering, Drell-Yan, $e^{+}{e}^{-}$ annihilation into hadron pairs, and proton-proton collisions. Consequently, we are able to extract a universal set of nonperturbative functions that describes the observed asymmetries in these reactions. The outcome of our analysis indicates single transverse-spin asymmetries in high-energy collisions have a common origin. Furthermore, we achieve the first phenomenological agreement with lattice QCD on the up and down quark tensor charges.

In an external magnetic field, the energy of the electroweak sphaleron—representing the energy barrier to baryon and lepton number violation—decreases but remains nonzero until the upper Ambjørn–Olesen critical field strength set by the Higgs mass and the electric charge. At this point the sphaleron energy vanishes. We demonstrate this by numerically computing the sphaleron configuration in the presence of an external magnetic field over the full range of field strengths until the energy barrier vanishes. We discuss the implications for baryogenesis in the early universe and the possibility of observing of baryon and lepton number violation in heavy-ion collisions.

A search for $CP$ violation in the ${\mathrm{\Lambda }}_b^0\to p{\pi }^{-}{\pi }^{+}{\pi }^{-}$ decay is performed using LHCb data corresponding to an integrated luminosity of $6.6{\mathrm{fb}}^{-1}$ collected in $pp$ collisions at center-of-mass energies of 7, 8 and 13 TeV. The analysis uses both triple product asymmetries and the unbinned energy test method. The highest significances of $CP$ asymmetry are 2.9 standard deviations from triple product asymmetries and 3.0 standard deviations for the energy test method. Once the global $p$-value is considered, all results are consistent with no $CP$ violation. Parity violation is observed at a significance of 5.5 standard deviations for the triple product asymmetry method and 5.3 standard deviations for the energy test method. The reported deviations are given in regions of phase space.

We initiate the application of Hamiltonian truncation methods to solve strongly coupled QFTs in $d=2+1$. By analysing perturbation theory with a Hamiltonian truncation regulator, we pinpoint the challenges of such an approach and propose a way that these can be addressed. This enables us to formulate Hamiltonian Truncation theory for ${\varphi }^4$ in $d=2+1$, and to study its spectrum at weak and strong coupling. The results obtained agree well with the predictions of a weak/strong self-duality possessed by the theory. The ${\varphi }^4$ interaction is a strongly relevant UV divergent perturbation, and represents a case study of a more general scenario. Thus, the approach developed should be applicable to many other QFTs of interest.

The regularization procedure for getting the four-dimensional nontrivial Einstein-Gauss-Bonnet effective description of gravity and its Lovelock generalization has been recently developed. Here we propose the regularization for the three-dimensional gravity, which is based on the rescaling of the coupling constants and, afterward, taking the limit $D\to 3$. We obtain the generalization of the Bañados-Teitelboim-Zanelli solution in the presence of the higher curvature (Gauss-Bonnet and Lovelock) corrections of any order. The obtained general solution shows a peculiar behavior: The event horizon is allowed not only for asymptotically anti–de Sitter spacetimes, but also for the de Sitter and flat cases, when the Gauss-Bonnet coupling constant is negative. The factor of the electric charge is analyzed as well for various branches of the solution, and the Hawking temperature is obtained.

The fluid-gravity correspondence documents a precise mathematical map between a class of dynamical spacetime solutions of the Einstein field equations of gravity and the dynamics of its corresponding dual fluid flows governed by the Navier-Stokes (NS) equations of hydrodynamics. This striking connection has been explored in several dynamics-based approaches and has surfaced in various forms over the past four decades. In a recent construction, it has been shown that the manifold properties of geometric duals are in fact intimately connected to the dynamics of incompressible fluids, thus bypassing the conventional on-shell standpoints. Following such a prescription, we construct the geometrical description that effectively captures the dynamics of an incompressible NS fluid with respect to a uniformly rotating frame. We propose the gravitational dual(s) described by bulk metric(s) in ($p+2$) dimensions such that the equations of parallel transport of an appropriately defined bulk velocity vector field when projected onto an induced timelike hypersurface require that the incompressible NS equation of a fluid relative to a uniformly rotating frame be satisfied at the relevant perturbative order in ($p+1$) dimensions. We argue that free fluid flows on manifold(s) described by the proposed metric(s) can be effectively considered as an equivalent theory of nonrelativistic viscous fluid dynamics with respect to a uniform rotating frame. We also present suggestive insights as to how spacetime rotation parameters encode information pertaining to the inertial effects in the corresponding fluid dual.

An accurate theoretical template of the redshift-space galaxy power spectrum, if applicable out to nonlinear scales, enables us to extract more stringent and robust constraints on cosmological parameters from the measured galaxy clustering. In this work, we develop a simulation-based template, so-called emulator, for the redshift-space power spectrum of dark matter halos. Using the redshift-space halo power spectra measured from the dark quest $N$-body simulation suite that covers 101 flat-geometry $w$-cold dark matter ($w\mathrm{CDM}$) cosmologies around the Planck $\mathrm{\Lambda }\mathrm{CDM}$ model, we feed these data into a feed-forward neural network to build the fast and accurate emulation of the power spectrum from the linear to nonlinear scales up to $k\simeq 0.6h{\mathrm{Mpc}}^{-1}$. Our emulator achieves about 1% and 5% fractional accuracies in predicting the monopole and quadrupole moments of the power spectrum, respectively, for halos of $\sim {10}^{13}{h}^{-1}{M}_{\odot }$ that correspond to host halos of the Sloan Digital Sky Survey (SDSS) LOWZ- and CMASS (constant mass)-like galaxies, where the achieved accuracies are sufficient compared to the statistical errors of SDSS volume. The validation and performance of the emulator are given by the comparison of the emulator predictions with the power spectra directly measured from the simulations for validation sets that are not used in the training. We demonstrate that the emulator outputs can be used to make model predictions for the redshift-space power spectrum of galaxies by employing user-fed models for the halo-galaxy connection, such as the halo occupation distribution. The emulator allows us to easily incorporate the Finger-of-God effect due to the virial motions of galaxies and the Alcock-Paczyński distortions. Our code can compute the redshift-space galaxy power spectrum in a CPU subseconds and is ready to perform the emulator-based cosmological analysis for the exiting and upcoming galaxy redshift surveys.

We investigate the recently introduced metastable dark energy (DE) models after the final $Planck$ 2018 legacy release. The essence of the present work is to analyze their evolution at the level of perturbations. Our analyses show that both the metastable dark energy models considered in this article, are excellent candidates to alleviate the $H_0$ tension. In particular, for the present models, $Planck$ 2018 alone can alleviate the $H_0$ tension within 68% CL. Along with the final cosmic microwave background data from the $Planck$ 2018 legacy release, we also include external cosmological datasets in order to asses the robustness of our findings.

We present a new version of the hadron interaction event generator sibyll. While the core ideas of the model have been preserved, the new version handles the production of baryon pairs and leading particles in a new way. In addition, production of charmed hadrons is included. Updates to the model are informed by high-precision measurements of the total and inelastic cross sections with the forward detectors at the LHC that constrain the extrapolation to ultrahigh energy. Minimum-bias measurements of particle spectra and multiplicities support the tuning of fragmentation parameters. This paper demonstrates the impact of these changes on air-shower observables such as $X_{\max }$ and $N_{\mu }$, drawing comparisons with other contemporary cosmic-ray interaction models.

Nonequilibrium Green’s functions provide an efficient way to describe the evolution of the energy-momentum tensor during the early-time preequilibrium stage of high-energy heavy-ion collisions. Besides their practical relevance they also provide a meaningful way to address the question when and to what extent a hydrodynamic description of the system becomes applicable. Within the kinetic theory framework we derive a new method to calculate time-dependent nonequilibrium Green’s functions describing the evolution of energy and momentum perturbations on top of an evolving far-from-equilibrium background. We discuss the approach toward viscous hydrodynamics along with the emergence of various scaling phenomena for conformal systems. By comparing our results obtained in the relaxation time approximation to previous calculations in Yang-Mills kinetic theory, we further address the question which macroscopic features of the energy-momentum tensor are sensitive to the underlying microscopic dynamics.

The standard nonperturbative approaches of renormalization group for tensor models are generally focused on a purely local potential approximation (i.e., involving only generalized traces and products of them) and are showed to strongly violate the modified Ward identities. This paper is a continuation of our recent contribution [Phys. Rev. D 101, 106015 (2020), intended to investigate the approximation schemes compatible with Ward identities and constraints between $2n$-points observables in the large $N$ limit. We consider separately two different approximations: In the first one, we try to construct a local potential approximation from a slight modification of the Litim regulator, so that it remains optimal in the usual sense, and preserves the boundary conditions in deep UV and deep IR limits. In the second one, we introduce derivative couplings in the truncations and show that the compatibility with Ward identities implies strong relations between $\beta$ functions, allowing one to close the infinite hierarchy of flow equations in the nonbranching sector, up to a given order in the derivative expansion. Finally, using an exact relation between correlations functions in large $N$ limit, we show that strictly local truncations are insufficient to reach the exact value for the critical exponent, highlighting the role played by these strong relations between observables taking into account the behavior of the flow; and the role played by the multitrace operators, discussed in the two different approximation schemes. In both cases, we compare our conclusions to the results obtained in the literature and conclude that, at a given order, by taking into account the exact functional relations between observables like Ward identities in a systematic way, we can strongly improve the physical relevance of the approximation for an exact renormalization group equation.

Precision neutrino oscillation experiments of the future—of which DUNE is a prime example—require reliable event generator tools. The 1–4 GeV energy regime, in which DUNE will operate, is marked by the transition from the low-energy nuclear physics domain to that of perturbative QCD, resulting in rich and highly complex physics. Given this complexity, it is important to establish a validation procedure capable of disentangling the physical processes and testing each of them individually. Here, we demonstrate the utility of this approach by benchmarking the GENIE generator, currently used by all Fermilab-based experiments, against a broad set of inclusive electron-scattering data. This comparison takes advantage of the fact that, while electron-nucleus and neutrino-nucleus processes share a lot of common physics, electron scattering gives one access to precisely known beam energies and scattering kinematics. Exploring the kinematic parameter range relevant to DUNE in this manner, we observe patterns of large discrepancies between the generator and data. These discrepancies are most prominent in the pion-producing regimes and are present not only in medium-sized nuclei, including argon, but also in deuterium and hydrogen targets, indicating mismodeled hadronic physics. Several directions for possible improvement are discussed.

Using a sample of 106 million $\psi (3686)$ decays, $\psi (3686)\to \gamma {\chi }_{cJ}(J=0,1,2)$ and $\psi (3686)\to \gamma {\chi }_{cJ},{\chi }_{cJ}\to \gamma J/\psi (J=1,2)$ events are utilized to study inclusive ${\chi }_{cJ}\to \text{anything}$, ${\chi }_{cJ}\to \text{hadrons}$, and $J/\psi \to \text{anything}$ distributions, including distributions of the number of charged tracks, electromagnetic calorimeter showers, and ${\pi }^0\mathrm{s}$, and to compare them with distributions obtained from the BESIII Monte Carlo simulation. Information from each Monte Carlo simulated decay event is used to construct matrices connecting the detected distributions to the input predetection “produced” distributions. Assuming these matrices also apply to data, they are used to predict the analogous produced distributions of the decay events. Using these, the charged particle multiplicities are compared with results from MARK I. Further, comparison of the distributions of the number of photons in data with those in Monte Carlo simulation indicates that G-parity conservation should be taken into consideration in the simulation.

We present the imrphenomxhm frequency domain phenomenological waveform model for the inspiral, merger, and ringdown of quasicircular nonprecessing black hole binaries. The model extends the imrphenomxas waveform model [G. Pratten, S. Husa, C. García-Quirós, M. Colleoni, A. Ramos-Buades, H. Estellés, and R. Jaume, preceding paper, Phys. Rev. D 102, 064001 (2020)], which describes the dominant quadrupole modes $\ell =|m|=2$, to the harmonics $(\ell ,|m|)=(2,1),(3,3),(3,2),(4,4)$, and includes mode mixing effects for the (3,2) spherical harmonic. imrphenomxhm is calibrated against hybrid waveforms, which match an inspiral phase described by the effective-one-body model and post-Newtonian amplitudes for the subdominant harmonics to numerical relativity waveforms and numerical solutions to the perturbative Teukolsky equation for large mass ratios up to 1000.

In this paper we present imrphenomxas, a thorough overhaul of the imrphenomd [S. Husa et al., Phys. Rev. D 93, 044006 (2016); S. Khan et al., Phys. Rev. D 93, 044007 (2016)] waveform model, which describes the dominant $l=2$, $|m|=2$ spherical harmonic mode of nonprecessing coalescing black holes in terms of piecewise closed form expressions in the frequency domain. Improvements include in particular the accurate treatment of unequal spin effects, and the inclusion of extreme mass ratio waveforms. imrphenomd has previously been extended to approximately include spin precession [M. Hannam et al., Phys. Rev. Lett. 113, 151101 (2014)] and subdominant spherical harmonics [L. London et al., Phys. Rev. Lett. 120, 161102 (2018)], and with its extensions it has become a standard tool in gravitational wave parameter estimation. Improved extensions of imrphenomxas are discussed in companion papers [C. García-Quirós et al., Phys. Rev. D 102, 064002 (2020); G. Pratten et al., arXiv:2004.06503].