We present the first searches for gravitational waves from $r$-modes of the Crab pulsar, coherently and separately integrating data from three stretches of the first two observing runs of Advanced LIGO using the $\mathcal{F}$-statistic. The second run was divided in two by a glitch of the pulsar roughly halfway through. The frequencies and derivatives searched were based on radio measurements of the pulsar’s spin-down parameters as described in Caride et al., [Phys. Rev. D 100, 064013 (2019)]. We did not find any evidence of gravitational waves. Our best 90% confidence upper limits on gravitational wave intrinsic strain were $1.5\times {10}^{-25}$ for the first run, $1.3\times {10}^{-25}$ for the first stretch of the second run, and $1.1\times {10}^{-25}$ for the second stretch of the second run. These are the first upper limits on gravitational waves from $r$-modes of a known pulsar to beat its spin-down limit, and they do so by more than an order of magnitude in amplitude or two orders of magnitude in luminosity.

We calculate the complete $T$ matrices of the elastic nucleon-nucleon scattering up to third order in SU(3) heavy baryon chiral perturbation theory. The phase shifts with orbital angular momentum $L\ge 2$ and the mixing angles with $J\ge 2$ are evaluated by using low-energy constants that are extracted from the meson-baryon analysis. It turns out that our prediction is consistent with the empirical phase shifts and mixing angles data and also the results from SU(2) heavy baryon chiral perturbation theory. The errors from the low-energy constants are analyzed in detail. Our calculation provides reliable evidence that the nucleon-nucleon interaction calculated in SU(3) heavy baryon chiral perturbation theory leads to reasonable predictions.

In this work, we calculate the higher mass spectra for the $2S$- and $1D$-wave fully-charmed and fully-bottom tetraquark states in a nonrelativistic potential quark model. The $2S$-wave fully-charmed/bottom tetraquark states lie in the mass range of $\sim (6.9,7.1)/(19.7,19.9)\mathrm{GeV}$, apart from the highest $0^{++}$ state $T_{(cc\overline{c}\overline{c})0^{++}}(7185)/T_{(bb\overline{b}\overline{b})0^{++}}(19976)$. Most of the $2S$-wave states highly overlap with the high-lying $1P$-wave states. The masses for the $1D$-wave fully-charmed/bottom tetraquark states are predicted to be in the range of $\sim (6.7,7.2)/(19.5,20.0)\mathrm{GeV}$. The mass range for the $D$-wave tetraquark states cover most of the mass range of the $P$-wave states and the whole mass range of the $2S$-wave states. The narrow structure $X(6900)$ recently observed at LHCb in the di-$J/\psi$ invariant mass spectrum may be caused by the $1P$-, or $2S$-, or $1D$-wave $T_{(cc\overline{c}\overline{c})}$ states. The vague structure $X(7200)$ may be caused by the highest $2S$-wave state $T_{(cc\overline{c}\overline{c})0^{++}}(7185)$, two low-lying $3S$-wave states $T_{(cc\overline{c}\overline{c})0^{++}}(7240)$ and $T_{(cc\overline{c}\overline{c})2^{++}}(7248)$, and/or the high-lying $1D$-wave states with masses around 7.2 GeV and $J^{PC}=0^{++},1^{++},2^{++},3^{++}$, or $4^{++}$. While it is apparent that the potential quark model calculations predict more states than the structures observed in the di-$J/\psi$ invariant mass spectrum, our calculations will help further understanding of the properties of these fully-heavy tetraquark states in their strong and magnetic interactions with open channels based on explicit quark model wave functions.

We discuss the pion and kaon distribution amplitudes up to twist-3 in the context of the random instanton vacuum (RIV). We construct explicitly the pertinent quasipion and quasikaon distributions in the RIV, and analyze them in leading order in the diluteness factor, at a resolution fixed by the inverse instanton size. The distribution amplitudes (DA) follow from the large momentum limit. The results at higher resolution are discussed using QCD evolution, and compared to their asymptotic limits and some lattice results.

Within the non-Abelian SU(2) Proca-Higgs theory, we study localized axially symmetric solutions possessing a finite field energy. It is shown that in a certain sense such solutions are analogs of the Nielsen-Olesen tube, since they have a longitudinal magnetic field creating a flux of this field over the central cross section of the Proca tube. The main difference between the Proca tube and the Nielsen-Olesen tube is that the Proca tube is described by a topologically trivial solution and has finite size, since its energy density decreases exponentially with distance. The dependence of the total field mass of the Proca tube on the value of one of the parameters determining the solution is examined in detail. The solutions are obtained both in the presence and in the absence of external sources (charge and current densities).

The radially excited pseudoscalar state $\eta (1295)$ is still poorly understood [as well as its $SU(3)$ partners $\pi (1300)$ and $K(1460)$] and we want to attract attention experimenters to its comprehensive study. As for the main three-body decay $\eta (1295)\to \eta \pi \pi$, here the main interest is the measurements of the shapes of the $\eta \pi$ and $\pi \pi$ mass spectra in which the contributions from the $a_0(980)$ resonance and the large $\pi \pi S$ wave ($\sigma$) should manifest themselves. To describe these mass spectra, we propose to use a simple isobar model with a single fitting parameter characterizing the relative intensity of the $a_0(980)$ and $\sigma$ state production. Our main goal is to discuss the dynamics of the isospin-breaking decays $\eta (1295)\to {\pi }^{+}{\pi }^{-}{\pi }^0$ and $\eta (1295)\to 3{\pi }^0$, whose experimental studies could continue the impressive story of isospin violations in the decays of light isoscalar mesons $\omega \to 2\pi$, $\eta \to 3\pi$, ${\eta }^{\prime }\to 3\pi$, $\eta (1405)\to 3\pi$, and $f_1(1285)\to 3\pi$. We estimate the widths of the isospin-breaking decays $\eta (1295)\to 3\pi$ produced via the mixing of the ${\pi }^0-\eta$ and $a_0^0(980)-f_0(980)$ states and also due to the ${\pi }^0(1300)-\eta (1295)$ mixing. Processes that have the potential for detecting $\eta (1295)\to 3\pi$ decays are discussed.

We show how to compute directly the renormalization/evolution of the radiative jet function that appears in the factorization theorems for $B\to \gamma \ell \nu$ and $H\to \gamma \gamma$ through a $b$-quark loop. We point out that, in order to avoid double counting of soft contributions, one should use in the factorization theorems a subtracted radiative jet function from which soft contributions have been removed. The soft-contribution subtractions are zero-bin subtractions in the terminology of soft-collinear effective theory. We show that they can be factored from the radiative jet function and that the resulting soft-subtraction function gives rise to a nonlocal renormalization of the subtracted radiative jet function. This is a novel instance in which zero-bin subtractions lead to a nonlocality in the renormalization of a subtracted quantity that is not present in the renormalization of the unsubtracted quantity. We demonstrate the use of our formalism by computing the order-${\alpha }_s$ evolution kernel for the subtracted radiative jet function. Our result is in agreement with the result that had been inferred previously by making use of the factorization theorem for $B\to \gamma \ell \nu$, but that had been ascribed to the unsubtracted radiative jet function.

This work presents a sensitivity study of a reactor liquid scintillator detector to three kinds of dark bosons with masses below 1 MeV, such as dark photons, axion-like particles, and light scalar bosons. The JUNO-TAO detector with Taishan nuclear reactor is taken as a reference. With a proposed 180 days of data taking, the best sensitivity result at the level of $\sim {10}^{-5}$ 95% C.L. is achieved for dark photons with an optimized signal to background ratio for the electron coupling constant $g_X$ through inverse Compton-like scattering. Similar calculations are completed for axion-like particles and scalar bosons. The background systematic uncertainty presents as the main limiting factor for the further sensitivity improvement. Several remarks are made to the controversial analysis for the NEOS experiment. Additionally the differential and the inverse differential cross sections have been derived for all three boson types and their interactions with electrons in liquid scintillator.

We propose a new candidate of GeV-scale inelastic dark matter (DM). Our construction has an anomaly-free $U(1{)}_X$ gauge group with a dark photon mediator, and it can realize either scalar or fermionic inelastic DM. It is highly predictive and testable. We study the scattering rate of light inelastic DM with electrons in the XENON1T experiment and with nuclei in the XENON1T, CRESST-III, CDEX-1B and DarkSide-50 experiments. We resolve the recent XENON1T anomaly via electron recoil detection. Combining the XENON1T constraints from both electron recoils and nuclear recoils (including the Migdal effect), we predict the inelastic DM mass $\lesssim 1.4\mathrm{GeV}$. We further analyze the bounds by the DM relic abundance, the lifetime of heavier DM components, and laboratory constraints, from which we identify the viable parameter space for the future probe. This provides an important benchmark for the theories and experimental tests of GeV-scale inelastic DM.

New light singlet scalars with flavor-specific couplings represent a phenomenologically distinctive and flavor-safe alternative to the well-studied possibility of Higgs-portal scalars. However, in contrast to the Higgs portal, flavor-specific couplings require an ultraviolet completion involving new heavy states charged under the Standard Model gauge symmetries, leading to a host of additional novel phenomena. Focusing for concreteness on a scenario with up-quark-specific couplings, we investigate two simple renormalizable completions, one with an additional vectorlike quark and another featuring an extra scalar doublet. We consider the implications of naturalness, flavor- and $CP$ violation, electroweak precision observables, and direct searches for the new states at the LHC. These bounds, while being model dependent, are shown to probe interesting regions in the parameter space of the scalar mass and its low-energy effective coupling, complementing the essential phenomenology of the low-energy effective theory at a variety of low and medium energy experiments.

We present a lattice analysis of the light pseudoscalar mesons with consideration for the mixing between the flavor-neutral states ${\pi }^0$, $\eta$ and ${\eta }^{\prime }$. We extract the masses and flavor compositions of the pseudoscalar meson nonet in $n_f=1+1+1$ lattice $\mathrm{QCD}+\mathrm{QED}$ around an SU(3)-flavor symmetric point, and observe flavor-symmetry features of the extracted data, along with preliminary extrapolation results for the flavor compositions at the physical point. A key result of this work is the observed mass splitting between the ${\pi }^0$ and $\eta$ on our ensembles, which is found to exhibit behavior that is simply related to the corresponding flavor compositions.

In light of the first observation of the semileptonic decay $B_s^0\to K^{-}{\mu }^{+}{\nu }_{\mu }$ by the LHCb Collaboration, we revisit the determination of the Cabibbo-Kobayashi-Maskawa parameter $|V_{ub}|$ from exclusive semileptonic $B$-meson decays. A controlled theoretical input on the Standard Model $B\to \pi$ and $B_s\to K$ vector and scalar form factors from Lattice QCD in the large $q^2$ region, in combination with experimental measurements of the differential $B\to \pi \ell {\nu }_{\ell }$ and $B_s^0\to K^{-}{\mu }^{+}{\nu }_{\mu }$ branching ratio distributions, has allowed us determine $|V_{ub}|=3.86(11)\times {10}^{-3}$ and $|V_{ub}|=3.58(9)\times {10}^{-3}$ from the analyses of the individual decay channels, respectively, and $|V_{ub}|=3.68(5)\times {10}^{-3}$ from a simultaneous analysis of both decays, which is only a 1.4% error and differs by $1.8\sigma$ with respect to the value from inclusive determinations $|V_{ub}|=4.25(12{)}_{-14}^{+15}(23)\times {10}^{-3}$. Our results are based on the use of Padé approximants to the participating form factors, highlighting the importance of the decay $B_s\to K\mu {\nu }_{\mu }$ in complementing the traditional $B\to \pi \ell {\nu }_{\ell }$ one in the exclusive determination of $|V_{ub}|$ and allowing us to obtain, to the best of our knowledge, the first correlated results for the $B\to \pi$ and $B_s\to K$ vector and scalar form factors. We hope that our study strengthens the case for precise measurements of the differential $B_s\to K\ell {\nu }_{\ell }$ decay rate with a finer resolution of the $q^2$ bins, as it would definitely allow achieving more conclusive results for $|V_{ub}|$.

We perform an analytic calculation of the color fields in heavy-ion collisions by considering the collision of longitudinally extended nuclei in the dilute limit of the color glass condensate effective field theory of high-energy QCD. Based on general analytic expressions for the color fields in the future light cone, we evaluate the rapidity profile of the transverse pressure within a simple specific model of the nuclear collision geometry and compare our results to $(3+1)\mathrm{D}$ classical Yang-Mills simulations.

We propose a new measurement of the heavy flavor hadron double spin asymmetry in deep-inelastic scattering at a future Electron-Ion Collider (EIC) to constrain the polarized gluon distribution function inside the proton. Statistical projection on $D^0$ meson double spin asymmetry is calculated with an EIC central detector using an all-silicon tracker and vertexing subsystem. A first impact study was done by interpreting pseudodata at next-to-leading order in QCD. The sensitivity of the experimental observable in constraining gluon helicity distribution in a wide range of parton momentum fraction $x$ has been investigated considering different collision energies. This measurement complements the inclusive spin-dependent structure function measurement and provides an opportunity to constrain the gluon helicity distribution in the moderate $x$ region.

With the upcoming Run 3 of the LHC, the $\mathrm{FASER}\nu$ and SND@LHC detectors will start a new era of neutrino physics using the far-forward high-energy neutrino beam produced in collisions at ATLAS. This emerging LHC neutrino physics program requires reliable estimates of the LHC’s forward neutrino fluxes and their uncertainties. In this paper, we provide a new fast-neutrino flux simulation, implemented as a RIVET module, to address this issue. We present the expected energy distributions going through the $\mathrm{FASER}\nu$ and SND@LHC detectors based on various commonly used event generators, analyze the origin of those neutrinos, and present the expected neutrino event rates.

Neutrinos have two properties that make them fairly unique from other known particles: extremely low cross sections and flavor changing oscillations. With a good knowledge of the oscillation parameters soon in hand, it will become possible to detect low-energy atmospheric neutrinos sensitive to the forward elastic scattering off electrons in the Earth’s core providing a measurement of the core properties and the matter effect itself. As the dynamics of the Earth’s core are complicated and in a difficult to probe environment, additional information from upcoming neutrino experiments will provide feedback into our knowledge of geophysics as well as useful information about exoplanet formation and various new physics scenarios including dark matter. In addition, we can probe the existence of the matter effect in the Earth and constrain the nonstandard neutrino interaction parameter ${\epsilon }_{ee}^{\oplus }$. We show how DUNE’s sensitivity to low-energy atmospheric neutrino oscillations can provide a novel constraint on the density and radius of the Earth’s core at the 9% level and the Earth’s matter effect at the 5% level. Finally, we illuminate the physics behind low-energy atmospheric neutrino resonances in the Earth.

The Bose et al.-Marletto-Vedral (BMV) experiment [S. Bose et al., Phys. Rev. Lett. 119, 240401 (2017); C. Marletto and V. Vedral, Phys. Rev. Lett. 119, 240402 (2017)] aims to prove that spacetime is nonclassical by observing entanglement generated by gravity. However, local hidden variable theories (LHVTs) can simulate the entangled correlations. We propose to extend the entanglement generated by the BMV experiment to distant quantum particles in a Bell experiment. Violating a Bell inequality would rule out LHVTs, providing a stronger proof of the nonclassicality of spacetime than the BMV proposal.

Motivated by recent work suggesting observably large spacetime fluctuations in the causal development of an empty region of flat space, we conjecture that these metric fluctuations can be quantitatively described in terms of a conformal field theory of near-horizon vacuum states. One consequence of this conjecture is that fluctuations in the modular Hamiltonian $\mathrm{\Delta }K$ of a causal diamond are equal to the entanglement entropy: $⟨\mathrm{\Delta }{K}^2⟩=⟨K⟩=\frac{A({\mathrm{\Sigma }}_{d-2})}{4G_d}$, where $A({\mathrm{\Sigma }}_{d-2})$ is the area of the entangling surface in $d$ dimensions. Our conjecture applies to flat space, the cosmological horizon of dS, and AdS Ryu-Takayanagi diamonds, but not to large finite area diamonds in the bulk of AdS. We focus on three pieces of quantitative evidence, from a Randall-Sundrum II braneworld, from the conformal description of black hole horizons, and from the fluid-gravity correspondence. Our hypothesis also suggests that a broader range of formal results can be brought to bear on observables in flat and dS spaces.

We study the holographic renormalization group (RG) flow in the presence of higher-order curvature corrections to the ($d+1$)-dimensional Einstein-Hilbert (EH) action for an arbitrary interacting scalar matter field by using the superpotential approach. We find the critical points of the RG flow near the local minima and maxima of the potential and show the existence of the bounce solutions. In contrast to the EH gravity, regarding the values of couplings of the bulk theory, superpotential may have both upper and lower bounds. Moreover, the behavior of the RG flow is controlled by singular curves. This study may shed some light on how a c-function can exist in the presence of these corrections.

Flatness—the absence of spacetime curvature—is a well-understood property of macroscopic, classical spacetimes in general relativity. The same cannot be said about the concepts of curvature and flatness in nonperturbative quantum gravity, where the microscopic structure of spacetime is not describable in terms of small fluctuations around a fixed background geometry. An interesting case is given by the two-dimensional models of quantum gravity, which lack a classical limit and therefore are maximally “quantum.” We investigate the recently introduced quantum Ricci curvature in causal dynamical triangulations quantum gravity on a two-dimensional torus, whose quantum geometry could be expected to behave as a flat space on suitably coarse-grained scales. On the basis of Monte Carlo simulations we have performed, with system sizes of up to 600.000 building blocks, this does not seem to be the case. Instead, we find a scale-independent “quantum flatness,” without an obvious classical analog. As part of our study, we develop a criterion that allows us to distinguish between local and global topological properties of the toroidal quantum system.