Search

We analyze the latest LHCb data on the $\pi^+\pi^-$ spectrum in the isospin-violating $X(3872)~\to~J/\psi \pi^+\pi^-$ decay, employing a model-independent approach based on dispersion theory to deal with the $\pi\pi$ final state interactions. Additionally, the isospin breaking effects are properly introduced, allowing for reliable and accurate extraction of the ratio, $R_X$, between the $X(3872)$ couplings to the $J/\psi \rho$ and $J/\psi \omega$ channels from the data. We find very good agreement with the LHCb data for the whole range of the $\pi^+\pi^-$ invariant mass, and $R_X$ is determined to be $0.19\pm 0.02$, significantly smaller than what was determined earlier. Using this value, we make predictions for the $\pi^+\pi^0\pi^-$ mass distribution in the $X(3872)~\to~J/\psi \pi^+\pi^0\pi^-$ process, which is currently accessible by the BESIII Collaboration, and update a prediction for the pole positions of the isovector partner states of the $X(3872)$, $W_{c1}$, with $I(J^{PC})=1(1^{++})$., Comment: 9 pages, 1 table and 2 figures

Using chiral effective field theory, we predict that there must be isovector charmonium-like $D\bar D^*$ hadronic molecules with $J^{PC}=1^{++}$ denoted as $W_{c1}$. The inputs are the properties of the $X(3872)$, including its mass and the ratio of its branching fractions of decays into $J/\psi\rho^0$ and $J/\psi\omega$. The predicted states are virtual state poles of the scattering matrix, pointing at a molecular nature of the $X(3872)$ as well as its spin partners. They should show up as either a mild cusp or dip at the $D\bar D^*$ thresholds, explaining why they are elusive in experiments. The so far negative observation also indicates that the $X(3872)$ is either a bound state with non-vanishing binding energy or a virtual state, only in these cases the $X(3872)$ signal dominates over that from the $W_{c1}^0$. The pole positions are $3881.2^{+0.8}_{-0.0}- i 1.6^{+0.7}_{-0.9}$ MeV for $W_{c1}^0$ on the fourth Riemann sheet of the $D^0\bar D^{*0}$-$D^+D^{*-}$ coupled-channel system, and $3866.9^{+4.6}_{-7.7}- i (0.07\pm0.01)$ MeV for $W_{c1}^\pm$ on the second Riemann sheet of the $(D\bar D^*)^\pm$ single-channel system. The findings imply that the peak in the $J/\psi\pi^+\pi^-$ invariant mass distribution is not purely from the $X(3872)$ but contains contributions from $W_{c1}^0$ predicted here. The states should have isovector heavy quark spin partners with $J^{PC}=0^{++}$, $2^{++}$ and $1^{+-}$, with the last one corresponding to $Z_c$. We suggest to search for the charged $0^{++}$, $1^{++}$ and $2^{++}$ states in $J/\psi\pi^\pm \pi^0$., Comment: 26 pages, 8 figures; version to be published in JHEP

The primary objective of this study is to investigate hadronic molecules of $K^*\bar K_1(1270)$ using a one-boson-exchange model, which incorporates exchanges of vector and pseudoscalar mesons in the $t$-channel, as well as the pion exchange in the $u$-channel. Additionally, careful consideration is given to the three-body effects resulting from the on-shell pion originating from $K_1(1270)\to K^*\pi$. Then the BESIII data of the $J/\psi\to\phi\eta\eta'$ process is fitted using the $K^*\bar K_1(1270)$ scattering amplitude with $J^{PC}=0^{--}$ or $1^{--}$. The analysis reveals that both the $J^{PC}=0^{--}$ and $1^{--}$ assumptions for $K^*\bar K_1(1270)$ scattering provide good descriptions of the data, with similar fit qualities. Notably, the parameters obtained from the best fits indicate the existence of $K^*\bar K_1(1270)$ bound states, denoted by $\phi(2100)$ and $\phi_0(2100)$ for the $1^{--}$ and $0^{--}$ states, respectively. The current experimental data, including the $\eta$ polar angular distribution, cannot distinguish which $K^*\bar K_1(1270)$ bound state contributes to the $J/\psi\to\phi\eta\eta'$ process, or if both are involved. Therefore, we propose further explorations of this process, as well as other processes, in upcoming experiments with many more $J/\psi$ events to disentangle the different possibilities., Comment: 11pages, 8figures and 1 table

This study focuses on the interaction of the pseudoscalar meson octet and the baryon decuplet. In the continuum, it is observed that several $J^{P}=\frac32^-$ baryon resonances can be produced by the Weinberg-Tomozawa interaction in unitarized chiral perturbation theory, including the $N(1875)$, $\Sigma(1670)$, $\Sigma(1910)$, $\Xi(1820)$ and $\Omega(2012)$. Among them, the $\Xi(1820)$ and $\Sigma(1670)$ may exhibit a potential two-pole structures. The unitarized chiral perturbation approach is then applied as the underlying theory to predict the energy levels of these systems in a finite volume. These energy levels are well described by the $K$-matrix parameterization constrained by flavor SU(3) symmetry. With the parameters from the best fits, the poles extracted from the $K$-matrix parameterization closely correspond to those derived from the underlying chiral effective field theory, as long as they are close to physical region and not significantly higher than the lowest relevant threshold., Comment: 11 pages, 6 figures and 2 tables

We propose that the $X(3915)$ observed in the $J/\psi\,\omega$ channel is the same state as the $\chi_{c2}(3930)$, and the $X(3960)$, observed in the $D_s^+D_s^-$ channel, is an $S$-wave $D_s^+ D_s^-$ hadronic molecule. In addition, the $J^{PC}=0^{++}$ {component in the $B^+\to D^+D^-K^+$} assigned to the $X(3915)$ in the current {\it Review of Particle Physics} has the same origin as the $X(3960)$, which has a mass around 3.94~GeV. To check the proposal, the available data in the $D\bar D$ and $D_s^+ D_s^-$ channels from both $ B$ decays and $\gamma\gamma$ fusion reaction are analyzed considering both the $D\bar D$-$D_s\bar D_s$-$D^*\bar D^*$-$D_s^*\bar D_s^*$ coupled channels with $0^{++}$ and a $2^{++}$ state introduced additionally. It is found that all the data in different processes can be simultaneously well reproduced, and the coupled-channel dynamics produce four hidden-charm scalar molecular states with masses around 3.73, 3.94, 3.99 and 4.23~GeV, respectively. The results may deepen our understanding of the spectrum of charmonia as well as of the interactions between charmed hadrons., Comment: 15 pages, 6 figures, 2 tables, to apear in Sci. Bull

We study the thermoelectric transport under shear strain in two spatial dimensional quantum matter using the holographic duality. General analytic formulae for the DC thermoelectric conductivities subjected to finite shear strain are obtained in terms of the black hole horizon data. Off-diagonal terms in the conductivity matrix appear also at zero magnetic field, resembling an emergent electronic nematicity which cannot nevertheless be identified with the presence of an anomalous Hall effect. For an explicit model study, we numerically construct a family of strained black holes and obtain the corresponding nonlinear stress-strain curves. We then compute all electric, thermoelectric, and thermal conductivities and discuss the effects of strain. While the shear elastic deformation does not affect the temperature dependence of thermoelectric and thermal conductivities quantitatively, it can strongly change the behavior of the electric conductivity. For both shear hardening and softening cases, we find a clear metal-insulator transition driven by the shear deformation. Moreover, the violation of the previously conjectured thermal conductivity bound is observed for large shear deformation., Comment: 35 pages, 13 figures

Recently, the LHCb Collaboration reported a near-threshold enhancement, $X(3960)$, in the $D_s^+D_s^-$ invariant mass distribution. We show that the data can be well described by either a bound or a virtual state below the $D_s^+D_s^-$ threshold. The mass given by the pole position is $(3928\pm3)$ MeV. Using this mass and the existing information on the $X(3872)$ and $Z_c(3900)$ resonances, a complete spectrum of the $S$-wave hadronic molecules formed by a pair of ground state charmed and anticharmed mesons is established. Thus, pole positions of the partners of the $X(3872)$, $Z_c(3900)$ and the newly observed $D_s^+D_s^-$ state are predicted. Calculations have been carried out at the leading order of nonrelativistic effective field theory and considering both heavy quark spin and light flavor SU(3) symmetries, though conservative errors from the breaking of these symmetries are provided., Comment: 19 pages, 4 figures and 5 tables. Version to appear in PRD

Lots of charmonium-like structures have been observed in the last two decades. Most of them have quantum numbers that can be formed by a pair of charm and anticharm quarks, thus it is difficult to unambiguously identify the exotic ones among them. In this Letter, by exploiting heavy quark spin symmetry, we present a robust prediction of the hadronic molecular scenario, where the $\psi(4230),\psi(4360)$ and $\psi(4415)$ are identified as $D\bar D_1,D^*\bar D_1$ and $D^*\bar D^*_2$ bound states, respectively. We show that a flavor-neutral charmonium-like exotic state with quantum numbers $J^{PC}=0^{--}$, denoted as $\psi_0(4360)$, should exist as a $D^*\bar D_1$ bound state. The mass and width of the $\psi_0(4360)$} are predicted to be $(4366\pm18)$ MeV and less than 10 MeV, respectively. The $\psi_0(4360)$ is significant in two folds: no $0^{--}$ hadron has been observed so far, and a study of this state will enlighten the understanding of the mysterious vector mesons between 4.2 and 4.5 GeV, as well as the nature of previously observed exotic $Z_c$ and $P_c$ states. We propose that such an exotic state can be searched for in $e^+e^-\to \eta \psi_0(4360)$ and uniquely identified by measuring the angular distribution of the outgoing $\eta$ meson., Comment: 7+3 pages, 7 figures, 2 tables; version to be appeared in PRL

The linear transform-based tensor nuclear norm (TNN) methods have recently obtained promising results for tensor completion. The main idea of this type of methods is exploiting the low-rank structure of frontal slices of the targeted tensor under the linear transform along the third mode. However, the low-rankness of frontal slices is not significant under linear transforms family. To better pursue the low-rank approximation, we propose a nonlinear transform-based TNN (NTTNN). More concretely, the proposed nonlinear transform is a composite transform consisting of the linear semi-orthogonal transform along the third mode and the element-wise nonlinear transform on frontal slices of the tensor under the linear semi-orthogonal transform, which are indispensable and complementary in the composite transform to fully exploit the underlying low-rankness. Based on the suggested low-rankness metric, i.e., NTTNN, we propose a low-rank tensor completion (LRTC) model. To tackle the resulting nonlinear and nonconvex optimization model, we elaborately design the proximal alternating minimization (PAM) algorithm and establish the theoretical convergence guarantee of the PAM algorithm. Extensive experimental results on hyperspectral images, multispectral images, and videos show that the our method outperforms linear transform-based state-of-the-art LRTC methods qualitatively and quantitatively., Comment: Nonlinear transform, tensor nuclear norm, proximal alternating minimization, tensor completion

The holographic duality has proven successful in linking seemingly unrelated problems in physics.Recently, intriguing correspondences between the physics of soft matter and gravity are emerging,including strong similarities between the rheology of amorphous solids, effective field theories for elasticity and the physics of black holes. However, direct comparisons between theoretical predictions and experimental/simulation observations remain limited. Here, we study the effects of non-linear elasticity on the mechanical and thermodynamic properties of amorphous materials responding to shear, using effective field and gravitational theories. The predicted correlations among the non-linear elastic exponent, the yielding strain/stress and the entropy change due to shear are supported qualitatively by simulations of granular matter models. Our approach opens a path towards understanding complex mechanical responses of amorphous solids, such as mixed effects of shear softening and shear hardening, and offers the possibility to study the rheology of solid states and black holes in a unified framework., Comment: 24 pages, 21 figures

We study the magnetotransport in a minimal holographic setup of a metal-insulator transition in two spatial dimensions. Some generic features are obtained without referring to the non-linear details of the holographic theory. The temperature dependence of resistivity is found to be well scaled with a single parameter $T_0$, which approaches zero at some critical charge density $\rho_c$, and increases as a power law $T_0\sim|\rho-\rho_c|^{1/2}$ both in metallic $(\rho>\rho_c)$ and insulating $(\rho<\rho_c)$ regions in the vicinity of the transition. Similar features also happen by changing the disorder strength as well as magnetic field. By requiring a positive definite longitudinal conductivity in the presence of an applied magnetic field restricts the allowed parameter space of theory parameters. We explicitly check the consistency of parameter range for two representative models, and compute the optical conductivities for both metallic and insulating phases, from which a disorder-induced transfer of spectral weight from low to high energies is manifest. We construct the phase diagram in terms of temperature and disorder strength. The complexity during the transition is studied and is found to be not a good probe to the metal-insulator transition., Comment: 31 pages, 17 figures. v3: comments and references added, to appear in JHEP

As low-rank modeling has achieved great success in tensor recovery, many research efforts devote to defining the tensor rank. Among them, the recent popular tensor tubal rank, defined based on the tensor singular value decomposition (t-SVD), obtains promising results. However, the framework of the t-SVD and the tensor tubal rank are applicable only to three-way tensors and lack of flexibility to handle different correlations along different modes. To tackle these two issues, we define a new tensor unfolding operator, named mode-$k_1k_2$ tensor unfolding, as the process of lexicographically stacking the mode-$k_1k_2$ slices of an $N$-way tensor into a three-way tensor, which is a three-way extension of the well-known mode-$k$ tensor matricization. Based on it, we define a novel tensor rank, the tensor $N$-tubal rank, as a vector whose elements contain the tubal rank of all mode-$k_1k_2$ unfolding tensors, to depict the correlations along different modes. To efficiently minimize the proposed $N$-tubal rank, we establish its convex relaxation: the weighted sum of tensor nuclear norm (WSTNN). Then, we apply WSTNN to low-rank tensor completion (LRTC) and tensor robust principal component analysis (TRPCA). The corresponding WSTNN-based LRTC and TRPCA models are proposed, and two efficient alternating direction method of multipliers (ADMM)-based algorithms are developed to solve the proposed models. Numerical experiments demonstrate that the proposed models significantly outperform the compared ones.

Remotely sensed images may contain some missing areas because of poor weather conditions and sensor failure. Information of those areas may play an important role in the interpretation of multitemporal remotely sensed data. The paper aims at reconstructing the missing information by a non-local low-rank tensor completion method (NL-LRTC). First, nonlocal correlations in the spatial domain are taken into account by searching and grouping similar image patches in a large search window. Then low-rankness of the identified 4-order tensor groups is promoted to consider their correlations in spatial, spectral, and temporal domains, while reconstructing the underlying patterns. Experimental results on simulated and real data demonstrate that the proposed method is effective both qualitatively and quantitatively. In addition, the proposed method is computationally efficient compared to other patch based methods such as the recent proposed PM-MTGSR method.