Chiral anomaly and anomalous finite-size conductivity in graphene

Graphene is a monolayer of carbon atoms packed into a hexagon lattice to host two pairs of massless two-dimensional Dirac fermions in the absence of or with negligible spin-orbit coupling. It is known that the existence of non-zero electric polarization in reduced momentum space which is associated with a hidden chiral symmetry will lead to the zero-energy flat band of zigzag nanoribbon. The Adler-Bell-Jackiw chiral anomaly or non-conservation of chiral charges at different valleys can be realized in a confined ribbon of finite width. In the laterally diffusive regime, the finite-size correction to conductivity is always positive and goes inversely with the square of the lateral dimension W, which is different from the finite-size correction inversely with W from boundary modes. This anomalous finite-size conductivity reveals the signature of the chiral anomaly in graphene, and is measurable experimentally.Comment: 5 pages, 2 figure

Regenerated cellulose/multiwalled carbon nanotube composite films with enhanced mechanical properties prepared in NaOH/urea aqueous solution

Regenerated cellulose (RC)/multiwalled carbon nanotube (MWCNTs) composite films have been successfully prepared in NaOH/urea aqueous solution by coagulation with H2SO4 solution. The structure and properties of the RC/MWCNTs composite films are investigated by Fourier-transform infrared (FTIR) spectra, wide-angle X-ray diffraction (XRD), optical microscope (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and tensile testing. The results reveal that the MWCNTs disperse well in the cellulose matrix when the content of the MWCNTs is less than 1wt%. MWCNTs in the cellulose matrix maintain the original nanocrystalline structure and properties, weaken the hydrogen-bond formed between the cellulose, decrease the crystallinity of the composite films, but do not apparently reduce the thermal stability of the composite films. Compared to regenerated cellulose films, the mechanical properties of the composite films have been improved to some extent. The tensile strength of the composite films is bound to be 108 MPa, when the amount of MWCNTs is just 0.2wt %

Corrections to the Forward Limit Dispersion Relations for γZ\gamma Z-Exchange Contributions

In the past fifteen years, dispersion relations (DRs) in the forward limit have been widely accepted as a model-independent method for estimating the $\gamma Z$-exchange contributions to the parity asymmetry $A_{\textrm{PV}}$ in elastic $ep$ scattering. In this work, for the first time, we estimate the corrections to these DRs. Firstly, we analyze the properties of $A_{\textrm{PV}}$ based on a general formalism, and discuss the possibility of the DRs breaking down due to two kinematic poles in $A_{\textrm{PV}}$. Then, we use point-like interactions as an example to illustrate the exact breakdown of these DRs at the experimental energy regions. Furthermore, by using the effective low-energy interactions, we estimate the $\gamma Z$-exchange contributions for the upcoming P2 experiment, and the results indicate that the correction to the forward limit DR for $\Box_{\gamma Z}^{V}$ is abot 47\%, which is significantly larger than the naive expectation prior to this study.Comment: 4 figure

Two-Photon-Exchange effect in ep→enπ+ep\rightarrow en\pi^+ at small −t-t with the hadronic model and dispersion relation approach

In this work, the two-photon-exchange (TPE) effect in $ep\rightarrow en\pi^+$ at small $-t$ is discussed. In the previous work, the TPE contribution with one $\pi$ intermediate state is estimated numerically within a hadronic model under the pion-dominance approximation. Here we extend the discussion to include one $\rho$ intermediate state. The TPE contribution can be described by one scalar function in the limit $m_e\rightarrow 0$, the dispersion relation (DR) satisfied by this scalar function is analysed. The analytic expressions for the imaginary parts of the TPE contributions from one $\pi$ or one $\rho$ intermediate state are given within the hadronic model. Combining these analytic expressions and the DR, the corresponding real parts of the TPE contributions can be estimated easily at any available region. This can help the further experimental analysis to include the TPE contributions in a convenient way. The numeric results show that the TPE correction with one $\rho$ intermediate state is much smaller than that with one $\pi$ intermediate state in the current energy region. These results suggest that the TPE contribution with an elastic state is the main TPE contribution in $ep\rightarrow en\pi^+$ at small $-t$

Production of charmonium χcJ(2P)\chi_{cJ}(2P) plus one ω\omega meson by e+e−e^+e^- annihilation

Inspired by the recent observation of $e^+e^-\to \omega X(3872)$ by the BESIII Collaboration, in this work we study the production of the charmonium $\chi_{cJ}(2P)$ by $e^+e^-$ annihilation. We find that the $e^+e^-\to\omega\chi_{c0}(2P)$ and $e^+e^-\to \omega\chi_{c2}(2P)$ have sizable production rates, when taking the cross section data from $e^+e^-\to \omega X(3872)$ as the scaling point and treating the $X(3872)$ as the charmonium $\chi_{c1}(2P)$. Considering that the dominant decay modes of $\chi_{c0}$ and $\chi_{c2}(2P)$ involve $D\bar{D}$ final states, we propose that $e^+e^-\to \omega D\bar{D}$ is an ideal process to identify $\chi_{c0}(2P)$ and $\chi_{c2}(2P)$, which is similar to the situation that happens in the $D\bar{D}$ invariant mass spectrum of the $\gamma\gamma\to D\bar{D}$ and $B^+\to D^+{D}^- K^+$ processes. With continuous accumulation of experimental data, these proposed production processes offer a promising avenue for exploration by the BESIII and Belle II collaborations.Comment: 7 pages and 6 figures. Accepted by Phys. Rev. D for publicatio

The weak decays of Ξc(′)→Ξ\Xi^{(')}_{c}\to\Xi in the light-front quark model

Without contamination from the final state interactions, the calculation of the branching ratios of semileptonic decays $\Xi^{(')}_{c}\to\Xi+e^+\nu_e$ may provide us more information about the inner structure of charmed baryons. Moreover, by studying those processes, one can better determine the form factors of $\Xi_c\to\Xi$ which can be further applied to relevant estimates. In this work, we use the light-front quark model to carry out the computations where the three-body vertex functions for $\Xi_c$ and $\Xi$ are employed. To fit the new data of the Belle II, we re-adjust the model parameters and obtain $\beta_{s[sq]}=1.07$ GeV which is 2.9 times larger than $\beta_{s\bar s}=0.366$ GeV. This value may imply that the $ss$ pair in $\Xi$ constitutes a more compact subsystem. Furthermore, we also investigate the non-leptonic decays of $\Xi^{(')}_c\to \Xi$ which will be experimentally measured soon, so our model would be tested by consistency with the new data.Comment: 10 pages, 3 figures and 6 tables. arXiv admin note: text overlap with arXiv:1912.0143

Analysis on Heavy Quarkonia Transitions with Pion Emission in Terms of the QCD Multipole Expansion and Determination of Mass Spectra of Hybrids

One of the most important tasks in high energy physics is search for the exotic states, such as glueball, hybrid and multi-quark states. The transitions $\psi(ns)\to \psi(ms)+\pi\pi$ and $\Upsilon(ns)\to \Upsilon(ms)+\pi\pi$ attract great attentions because they may reveal characteristics of hybrids. In this work, we analyze those transition modes in terms of the theoretical framework established by Yan and Kuang. It is interesting to notice that the intermediate states between the two gluon-emissions are hybrids, therefore by fitting the data, we are able to determine the mass spectra of hybrids. The ground hybrid states are predicted as 4.23 GeV (for charmonium) and 10.79 GeV (for bottonium) which do not correspond to any states measured in recent experiments, thus it may imply that very possibly, hybrids mix with regular quarkonia to constitute physical states. Comprehensive comparisons of the potentials for hybrids whose parameters are obtained in this scenario with the lattice results are presented.Comment: 16 pages, 2 figur

Relationship of cumulative dust exposure dose and cumulative abnormal rate of pulmonary function in coal mixture workers

AbstractTo investigate the dose-response relationship between cumulative dust exposure (CDE) and cumulative abnormal rate of pulmonary function in coal mixture workers. Three hundred and twenty eight coal mixture workers (exposed group) and 169 nondust-exposed workers (control group) were recruited. Basic information data were collected and pulmonary function tests were performed. Pulmonary function was compared between the two groups after comparing smoking behaviors. Pulmonary function indices [forced vital capacity in 1 second after full inspiration (FVC)%, forced expiratory volume (FEV)1%, and FEV1/FVC%] were compared among groups stratified by service length (exposure duration). The relationship between CDE dose and cumulative abnormal rate of pulmonary function in coal mixture workers was analyzed. Abnormal rate of pulmonary function in the exposed group (35.1%) was significantly higher than the control group (10.1%; p < 0.001); FVC%, FEV1%, and FEV1/FVC% in the exposed group decreased significantly compared with the control group (all p < 0.05). Differences in FVC%, FEV1%, and FEV1/FVC% among coal mixture workers stratified by exposure duration in the exposed group were statistically significant (all p < 0.05). The discernible increase in the cumulative abnormal rate was observed, from ≥ 1000 mg/m3·years group to ≥ 1700 mg/m3·years group. Correlation analysis revealed a positive correlation between the CDE dose and the cumulative abnormal rate of pulmonary function. Higher abnormal pulmonary function rate was found among coal mixture workers, characterized by decreased pulmonary function indices. Our results suggested a positive relationship between CDE dose and cumulative abnormal pulmonary function rate, and a rapid increase in cumulative abnormal rate within a certain range of CDE dose. A lower limit value of 1000 mg/m3·years has reference significance