The electromagnetic decays of the charmed and bottom baryons in chiral perturbation theory

We have investigated the electromagnetic decays of the antitriplet and sextet charmed baryon systems with $J^P= \frac{1}{2}^+, \frac{3}{2}^+$ in the framework of the heavy baryon chiral perturbation theory. We first construct the chiral Lagrangians at $O(p^2)$ and $O(p^3)$. Then we calculate the electromagnetic (EM) decay amplitudes of the charmed baryon systems up to $O(p^3)$. With the help of the quark model, we estimate the low energy constants. The numerical results of the EM decay widths show good convergence of the chiral expansion. We notice that the two neutral EM decay processes $\Xi_c'^0\rightarrow\gamma+\Xi_c^0$ and ${\Xi_c^*}'^0\rightarrow\gamma+\Xi_c^0$ are strongly suppressed by the SU(3) U-spin flavor symmetry. With the same formalism, we also estimate the EM decay widths of the bottomed baryons. The EM decay widths of the heavy baryons may be measured at facilities such as LHCb and JPARC. The explicit chiral structures of the heavy baryon decay amplitudes derived in this work may be useful to the possible chiral extrapolations of the future lattice simulations of these EM decay amplitudes

The consistency of estimator under fixed design regression model with NQD errors

In this article, basing on NQD samples, we investigate the fixed design nonparametric regression model, where the errors are pairwise NQD random errors, with fixed design points, and an unknown function. Nonparametric weighted estimator will be introduced and its consistency is studied. As special case, the consistency result for weighted kernel estimators of the model is obtained. This extends the earlier work on independent random and dependent random errors to NQD case

Exotic QQqˉqˉQQ\bar{q}\bar{q}, QQqˉsˉQQ\bar{q}\bar{s} and QQsˉsˉQQ\bar{s}\bar{s} states

After constructing the possible $J^P=0^-, 0^+, 1^-$ and $1^+$ $QQ\bar{q}\bar{q}$ tetraquark interpolating currents in a systematic way, we investigate the two-point correlation functions and extract the corresponding masses with the QCD sum rule approach. We study the $QQ\bar{q}\bar{q}$, $QQ\bar{q}\bar{s}$ and $QQ\bar{s}\bar{s}$ systems with various isospins $I=0, 1/2, 1$. Our numerical analysis indicates that the masses of doubly-bottomed tetraquark states are below the threshold of the two bottom mesons, two bottom baryons and one doubly bottomed baryon plus one anti-nucleon. Very probably these doubly-bottomed tetraquark states are stable.Comment: 37 pages, 2 figure

Evolution of green shipping research: themes and methods

Over the past 30 years, there have been growing concerns on theenvironmental impacts of maritime transportation, which have attractedgreat attention from both academia and practitioners. Understandingdevelopments in this area can help guide future research. We conducteda comprehensive review of green shipping research, comprising 213papers published in transportation journals in SSCI of 2017 over theperiod 1988–2017. We find that research on green shipping hasincreased greatly since 2012, accounting for 77.5% of the reviewedpapers. The main focus today on green shipping was on air pollution,and the classification of green shipping practice, such as technical measures,operational options, market-based measures, and recycling andreusing, is becoming clear. According to the existing studies, futureresearch on green shipping must strengthen technology research tonot only solve practical problems, but also to establish a theoreticalgreen shipping system. Moreover, researchers from different countriescould cooperate with each other to give effective suggestions on settingstandards and laws of green shipping. Finally, we identify the futureresearch themes will focus on setting up green shipping system andlegislation and policy

Possible Deuteron-like Molecular States Composed of Heavy Baryons

We perform a systematic study of the possible loosely bound states composed of two charmed baryons or a charmed baryon and an anti-charmed baryon within the framework of the one boson exchange (OBE) model. We consider not only the $\pi$ exchange but also the $\eta$, $\rho$, $\omega$, $\phi$ and $\sigma$ exchanges. The $S-D$ mixing effects for the spin-triplets are also taken into account. With the derived effective potentials, we calculate the binding energies and root-mean-square (RMS) radii for the systems $\Lambda_c\Lambda_c(\bar{\Lambda}_c)$, $\Xi_c\Xi_c(\bar{\Xi}_c)$, $\Sigma_c\Sigma_c(\bar{\Sigma}_c)$, $\Xi_c^\prime\Xi_c^\prime(\bar{\Xi}_c^\prime)$ and $\Omega_c\Omega_c(\bar{\Omega}_c)$. Our numerical results indicate that: (1) the H-dibaryon-like state $\Lambda_c\Lambda_c$ does not exist; (2) there may exist four loosely bound deuteron-like states $\Xi_c\Xi_c$ and $\Xi_c^\prime\Xi_c^\prime$ with small binding energies and large RMS radii.Comment: 17 pages, 32 figure

Possible JPC=0+−J^{PC} = 0^{+-} Exotic State

We study the possible exotic states with $J^{PC} = 0^{+-}$ using the tetraquark interpolating currents with the QCD sum rule approach. The extracted masses are around 4.85 GeV for the charmonium-like states and 11.25 GeV for the bottomomium-like states. There is no working region for the light tetraquark currents, which implies the light $0^{+-}$ state may not exist below 2 GeV.Comment: 13 pages, 11 figures, 2 table