Assignments of ΛQ\Lambda_Q and ΞQ\Xi_Q baryons in the heavy quark-light diquark picture

We apply a new mass formula which is derived analytically in the relativistic flux tube model to the mass spectra of $\Lambda_Q$ and $\Xi_Q$ (\emph{Q} = \emph{c} or \emph{b} quark) baryons. To this end, the heavy quark-light diquark picture is employed. We find that all masses of the available $\Lambda_Q$ and $\Xi_Q$ states can be understood well. The assignments to these states do not appear to contradict the strong decay properties. $\Lambda_c(2760)^+$ and $\Xi_c(2980)$ are assigned to the first radial excitations with $J^P = 1/2^+$. $\Lambda_c(2940)^+$ and $\Xi_c(3123)$ might be the 2\emph{P} states. The $\Lambda_c(2880)^+$ and $\Xi_c(3080)$ are the good 1\emph{D} candidates with $J^P = 5/2^+$. $\Xi_c(3055)$ is likely to be a 1\emph{D} state with $J^P = 3/2^+$. $\Lambda_b(5912)^0$ and $\Lambda_b(5920)^0$ favor the 1\emph{P} assignments with $J^P = 1/2^-$ and $3/2^-$, respectively. We propose a search for the $\tilde{\Lambda}_{c2}(5/2^-)$ state which can help to distinguish the diquark and three-body schemes.Comment: 9 tables, more discussions and references adde

Low-lying charmed and charmed-strange baryon states

In this work, we systematically study the mass spectra and strong decays of $1P$ and $2S$ charmed and charmed-strange baryons in the framework of nonrelativistic constituent quark models. With the light quark cluster-heavy quark picture, the masses are simply calculated by a potential model. The strong decays are studied by the Eichten-Hill-Quigg decay formula. Masses and decay properties of the well-established $1S$ and $1P$ states can be reproduced by our method. $\Sigma_c(2800)^{0,+,++}$ can be assigned as a $\Sigma_{c2}(3/2^-)$ or $\Sigma_{c2}(5/2^-)$ state. We prefer to interpret the signal $\Sigma_c(2850)^0$ as a $2S(1/2^+)$ state although at present we cannot thoroughly exclude the possibility that this is the same state as $\Sigma_c(2800)^0$. $\Lambda_c(2765)^+$ or $\Sigma_c(2765)^+$ could be explained as the $\Lambda_c^+(2S)$ state or $\Sigma^+_{c1}(1/2^-)$ state, respectively. We propose to measure the branching ratio of $\mathcal{B}(\Sigma_c(2455)\pi)/\mathcal{B}(\Sigma_c(2520)\pi)$ in future, which may disentangle the puzzle of this state. Our results support $\Xi_c(2980)^{0,+}$ as the first radial excited state of $\Xi_c(2470)^{0,+}$ with $J^P=1/2^+$. The assignment of $\Xi_c(2930)^0$ is analogous to $\Sigma_c(2800)^{0,+,++}$, \emph{i.e.}, a $\Xi^\prime_{c2}(3/2^-)$ or $\Xi^\prime_{c2}(5/2^-)$ state. In addition, we predict some typical ratios among partial decay widths, which are valuable for experimental search for these missing charmed and charmed-strange baryons.Comment: 16 pages, 3 figures, 13 tables. Accepted by Eur. Phys. J.

The first Chinese student space shuttle getaway special program

The first Chinese Getaway Special program is described. Program organization, the student proposal evaluation procedure, and the objectives of some of the finalist's experiments are covered. The two experiments selected for eventual flight on the space shuttle are described in detail. These include: (1) the control of debris in the cabin of the space shuttle; and (2) the solidification of two immiscible liquids in space

Plastic avalanches in metal-organic framework crystals

The compressive properties of metal-organic framework (MOF) crystals are not only crucial for their densification but also key in determining their performance in many applications. We herein investigated the mechanical responses of a classic crystalline MOF, HKUST-1 by using in situ compression tests. A serrated flow accompanied by the unique strain avalanches was found in individual and contacting crystals before their final flattening or fracture with splitting cracks. The plastic flow with serrations is ascribed to the dynamic phase mixing due to the progressive and irreversible local phase transition in HKUST-1 crystals, as revealed by molecular dynamics and finite element simulations. Such pressure-induced phase coexistence in HKUST-1 crystals also induces a significant loading-history dependence of their Young's modulus. The observation of plastic avalanches in HKUST-1 crystals here not only expands our current understanding of the plasticity of MOF crystals but also unveils a novel mechanism for the avalanches and plastic flow in crystal plasticity