Weak Decays of Doubly Heavy Baryons: Bcc→BcV{\cal B}_{cc}\to {\cal B}_c V

The weak decays of a spin-$1/2$ doubly charm baryon (${\cal B}_{cc}$) to a spin-$1/2$ singly charm baryon (${\cal B}_c$) and a light vector meson ($V$) are studied under a phenomenological scheme. The contributions are classified into different topological diagrams, among which the short distance ones are calculated under the factorization hypothesis, and the long distance contributions are modelled as final-state interactions (FSIs) which are estimated with the one-particle-exchange model. In calculation the topological contributions tend to fall in a hierarchy. The branching fractions or decay widths are estimated, and it indicates that $\Xi_{cc}^+\to\Xi_c^+\pi^+\pi^-$ and $\Omega_{cc}^{+}\rightarrow\Xi_{c}^{+}K^-\pi^+$ can be used as candidate decays for searching $\Xi_{cc}^+$ and $\Omega_{cc}^+$. Some decays that are mainly activated by the long distance effects are found, observation on which in future experiments can help to understand the role of FSIs in charm baryon decays.Comment: 29 pages, 5 figures, 7 tables; version published in EPJ

Theory And Application Development Of Electronic Structure Methods Involving Heavy Computation

The propargyl radical, the most stable isomer of C3H3, is very important in combustion reactions. However, theoretical calculations have never been able to find a strong absorption around 242 nm as seen in experiments. In this study, we calculated the electronic energy levels of the propargyl radical using highly accurate multireference methods, including multireference configuration interaction singles and doubles method with triples and quadruples treated perturbatively [denoted as MRCISD(TQ)], as well as second and third order generalized Van Vleck perturbation theories (GVVPT2 and GVVPT3). Calculations indicate that this absorption can be solely attributed to a Franck-Condon-allowed transition from the ground B1 state to the Rydberg-like first A1 excited state. Calculations also show that GVVPT2 with a relatively small active space fails to capture enough Rydberg character of this excited state, while it can be recovered by GVVPT3, MRCISD, and MRCISD(TQ). In order to speed up MRCISD(TQ) calculations, the triple and quadruple (TQ) perturbative corrections, the most time-consuming part of MRCISD(TQ) calculations, were parallelized using Message Passing Interface (MPI). The MRCISD(TQ) method is organized in the framework of macroconfigurations, which allows the use of incomplete reference spaces and provides an efficient means of screening large number of non-interacting configuration state functions (CSFs). The test calculations show that the parallel code achieved close to linear speed-up when the number of CSFs in each macroconfiguration is small. The speed-up suffers when large numbers of CSFs exist in only a few macroconfigurations. The computer algorithm for second-order generalized van Vleck multireference perturbation theory (GVVPT2) was similarly parallelized using the MPI protocol, organized in the framework of macroconfigurations. The maximum number of CSFs per macroconfiguration is found to have less influence on the MPI speedup and scaling than in the case of MRCISD(TQ). It was previously found that unrestricted local density approximation (LDA) orbitals can be used in place of MCSCF to provide orbitals for GVVPT2. This inspired us to use the more controllable restricted density functional theory (DFT) to provide unbiased orbitals for GVVPT2 calculations. In this study, the relationship between restricted DFT and unrestricted DFT were explored and the restricted DFT results were obtained by utilizing subroutines from unrestricted DFT calculations. We also found that the DIIS technique drastically sped up the convergence of RDFT calculations. Plane wave DFT methods are commonly used to efficiently evaluate solid state materials. In this work, the electronic properties of pristine graphene and Zn-phthalocyanine tetrasulfonic acid (Zn-PcS) physisorbed on single-layer graphene were calculated using plane wave DFT. The Perdew-Burke-Ernzerhof functional with dispersion correction (PBE-D2) was used. The densities of states were obtained for both pristine and absorbed graphene, and the disappearance of the characteristic dip in the density of states of the adsorbed system was attributed to the lowest unoccupied molecular orbital of the adsorbed molecule. A small charge transfer from graphene to the molecule was found. We present comparison of DFT results with Scanning Tunneling Microscopy/Spectroscopy data

Chinese Species Resource and Protection Policy

6 pages

Holographic entanglement of purification for thermofield double states and thermal quench

We explore the properties of holographic entanglement of purification (EoP) for two disjoint strips in the Schwarzschild-AdS black brane and the Vaidya-AdS black brane spacetimes. For two given strips on the same boundary of Schwarzschild-AdS spacetime, there is an upper bound of the separation beyond which the holographic EoP will always vanish no matter how wide the strips are. In the case that two strips are in the two boundaries of the spacetime respectively, we find that the holographic EoP exists only when the strips are wide enough. If the width is finite, the EoP can be nonzero in a finite time region. For thermal quench case, we find that the equilibrium time of holographic EoP is only sensitive to the width of strips, while that of the holographic mutual information is sensitive not only to the width of strips but also to their separation.Comment: 23 pages, 12 figures, major correction of section