首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
In this article, we study the $\frac{1} {2}^ -$ and $\frac{3} {2}^ -$ heavy and doubly heavy baryon states $\Sigma _Q \left( {\frac{1} {2}^ - } \right)$ , $\Xi '_Q \left( {\frac{1} {2}^ - } \right)$ , $\Omega _Q \left( {\frac{1} {2}^ - } \right)$ , $\Xi _{QQ} \left( {\frac{1} {2}^ - } \right)$ , $\Omega _{QQ} \left( {\frac{1} {2}^ - } \right)$ , $\Sigma _Q^* \left( {\frac{3} {2}^ - } \right)$ , $\Xi _Q^* \left( {\frac{3} {2}^ - } \right)$ , $\Omega _Q^* \left( {\frac{3} {2}^ - } \right)$ , $\Xi _{QQ}^* \left( {\frac{3} {2}^ - } \right)$ and $\Omega _{QQ}^* \left( {\frac{3} {2}^ - } \right)$ by subtracting the contributions from the corresponding $\frac{1} {2}^ +$ and $\frac{3} {2}^ +$ heavy and doubly heavy baryon states with the QCD sum rules in a systematic way, and make reasonable predictions for their masses.  相似文献   

2.
Chemiluminescence experiments have been performed to assess the state of current $\mathrm{CO}_{2}^{*}$ kinetics modeling. The difficulty with modeling $\mathrm{CO}_{2}^{*}$ lies in its broad emission spectrum, making it a challenge to isolate it from background emission of species such as CH? and CH2O?. Experiments were performed in a mixture of 0.0005H2+0.01N2O+0.03CO+0.9595Ar in an attempt to isolate $\mathrm{CO}_{2}^{*}$ emission. Temperatures ranged from 1654 K to 2221 K at two average pressures, 1.4 and 10.4 atm. The unique time histories of the various chemiluminescence species in the unconventional mixture employed at these conditions allow for easy identification of the $\mathrm{CO}_{2}^{*}$ concentration. Two different wavelengths to capture $\mathrm{CO}_{2}^{*}$ were used; one optical filter was centered at 415 nm and the other at 458 nm. The use of these two different wavelengths was done to verify that broadband $\mathrm{CO}_{2}^{*}$ was in fact being captured, and not emission from other species such as CH? and CH2O?. As a baseline for time history and peak magnitude comparison, OH? emission was captured at 307 nm simultaneously with the two $\mathrm{CO}_{2}^{*}$ filters. The results from the two $\mathrm{CO}_{2}^{*}$ filters were consistent with each other, implying that indeed the same species (i.e., $\mathrm{CO}_{2}^{*}$ ) was being measured at both wavelengths. A first-generation kinetics model for $\mathrm{CO}_{2}^{*}$ and CH2O? was developed, since no comprehensively validated one exists to date. CH2O? and CH? were ruled out as being present in the experiments at any measurable level, based on calculations and comparisons with the data. Agreement with the $\mathrm{CO}_{2}^{*}$ model was only fair, which necessitates future improvements for a better understanding of $\mathrm{CO}_{2}^{*}$ chemiluminescence as well as the kinetics of the ground state species.  相似文献   

3.
4.
The theoretical calculations indicated that the monoclinic low-temperature phase of silver telluride $(\upbeta \hbox {-Ag}_{2}\hbox {Te})$ is a new binary topological insulator with highly anisotropic single Dirac cone surface. We obtained $\upbeta \hbox {-Ag}_{2}\hbox {Te}$ crystal ingots containing few grains by the Bridgman method. We also deposited thin films of tellurium, $\hbox {Ag}_{5}\hbox {Te}_{3}\hbox { and }(\hbox {Te+Ag}_{5}\hbox {Te}_{3})$ by thermal evaporation method. The Raman spectra of $\upbeta \hbox {-Ag}_{2}\hbox {Te}$ , tellurium and $\hbox {Ag}_{5}\hbox {Te}_{3}$ were measured at three excitation wave lengths: 633, 515 and 488 nm. The Raman active modes of $\upbeta \hbox {-Ag}_{2}\hbox {Te}$ , tellurium and $\hbox {Ag}_{5}\hbox {Te}_{3}$ are situated at frequencies below 300  $\hbox {cm}^{-1}$ while vibrations of other phases appear at higher frequencies.  相似文献   

5.
It is shown that for each finite number N of Dirac measures ${\delta_{s_n}}$ supported at points ${s_n \in {\mathbb R}^3}$ with given amplitudes ${a_n \in {\mathbb R} \backslash\{0\}}$ there exists a unique real-valued function ${u \in C^{0, 1}({\mathbb R}^3)}$ , vanishing at infinity, which distributionally solves the quasi-linear elliptic partial differential equation of divergence form ${-\nabla \cdot ( \nabla{u}/ \sqrt{1-| \nabla{u} |^2}) = 4 \pi \sum_{n=1}^N a_n \delta_{s_n}}$ . Moreover, ${u \in C^{\omega}({\mathbb R}^3\backslash \{s_n\}_{n=1}^N)}$ . The result can be interpreted in at least two ways: (a) for any number N of point charges of arbitrary magnitude and sign at prescribed locations s n in three-dimensional Euclidean space there exists a unique electrostatic field which satisfies the Maxwell-Born-Infeld field equations smoothly away from the point charges and vanishes as |s| ?? ??; (b) for any number N of integral mean curvatures assigned to locations ${s_n \in {\mathbb R}^3 \subset{\mathbb R}^{1, 3}}$ there exists a unique asymptotically flat, almost everywhere space-like maximal slice with point defects of Minkowski spacetime ${{\mathbb R}^{1, 3}}$ , having lightcone singularities over the s n but being smooth otherwise, and whose height function vanishes as |s| ?? ??. No struts between the point singularities ever occur.  相似文献   

6.
We study mutually unbiased unextendible maximally entangled bases (MUUMEBs) in bipartite stystem \(\mathbb {C}^{d}\otimes \mathbb {C}^{d + 1}\). By deriving the sufficient and necessary conditions that two MUUMEBs in \(\mathbb {C}^{3}\otimes \mathbb {C}^{4}\) need to satisfy, we first establish two pairs of MUUMEBs in \(\mathbb {C}^{3}\otimes \mathbb {C}^{4}\). Then we present the sufficient and necessary conditions that two MUUMEBs in bipartite system \(\mathbb {C}^{d}\otimes \mathbb {C}^{d + 1}\) need to satisfy, thus generalize the main results of Halqem et al. (Int. J. Theor. Phys. 54(1), 326, 2015).  相似文献   

7.
We estimate $BR(K \to \pi \nu \bar \nu )$ in the context of the Standard Model by fitting for λ tV tdV ts * of the “kaon unitarity triangle” relation. To find the vertex of this triangle, we fit data from |? K|, the CP-violating parameter describing K mixing, and a ψ,K , the CP-violating asymmetry in B d 0 J/ψK 0 decays, and obtain the values $\left. {BR(K \to \pi \nu \bar \nu )} \right|_{SM} = (7.07 \pm 1.03) \times 10^{ - 11} $ and $\left. {BR(K_L^0 \to \pi ^0 \nu \bar \nu )} \right|_{SM} = (2.60 \pm 0.52) \times 10^{ - 11} $ . Our estimate is independent of the CKM matrix element V cb and of the ratio of B-mixing frequencies ${{\Delta m_{B_s } } \mathord{\left/ {\vphantom {{\Delta m_{B_s } } {\Delta m_{B_d } }}} \right. \kern-0em} {\Delta m_{B_d } }}$ . We also use the constraint estimation of λ t with additional data from $\Delta m_{B_d } $ and |V ub|. This combined analysis slightly increases the precision of the rate estimation of $K^ + \to \pi ^ + \nu \bar \nu $ and $K_L^0 \to \pi ^0 \nu \bar \nu $ (by ?10 and ?20%, respectively). The measured value of $BR(K^ + \to \pi ^ + \nu \bar \nu )$ can be compared both to this estimate and to predictions made from ${{\Delta m_{B_s } } \mathord{\left/ {\vphantom {{\Delta m_{B_s } } {\Delta m_{B_d } }}} \right. \kern-0em} {\Delta m_{B_d } }}$ .  相似文献   

8.
The fully differential angular distribution for the rare flavor-changing neutral current decay $\bar{B}_{d}^{0} \to\bar{K}^{*0} (\to K^{-} \pi^{+}) \mu^{+}\mu^{-} $ is studied. The emphasis is placed on accurate treatment of the contribution from the processes $\bar{B}_{d}^{0} \to\bar{K}^{*0} (\to K^{-} \pi^{+}) V $ with intermediate vector resonances V=??(770),??(782),?(1020),J/??,??(2S),?? decaying into the ?? + ?? ? pair. The dilepton invariant-mass dependence of the branching ratio, longitudinal polarization fraction f L of the $\bar{K}^{*0}$ meson, and forward?Cbackward asymmetry A FB is calculated and compared with data from Belle, CDF and LHCb. It is shown that inclusion of the resonance contribution may considerably modify the branching ratio, calculated in the SM without resonances, even in the invariant-mass region far from the so-called charmonia cuts applied in the experimental analyses. This conclusion crucially depends on values of the unknown phases of the B 0??K ?0 J/?? and B 0??K ?0 ??(2S) decay amplitudes with zero helicity.  相似文献   

9.
In this work, we present a study of the magneto transport properties in magnetic multilayered structure $\text{ Ni }_{81}\text{ Fe }_{19}\text{/Zr }$ Ni 81 Fe 19 /Zr . The magnetic $(\text{ Ni }_{81}\text{ Fe }_{19})$ ( Ni 81 Fe 19 ) and non magnetic (Zr) layer thickness $(\mathbf{t}_\mathbf{NiFe}, \mathbf{t}_\mathbf{zr})$ ( t NiFe , t zr ) effects on the magneto resistance (MR) are discussed theoretically in the framework of the Johnson–Camley semi classical approach based on the Boltzmann transport equation. A comparison between calculated and measured MR is obtained. The observed MR ratio oscillates for Zr layer thickness with an average period of 7Å. A generally weak $\text{ MR }(\text{ t }_{\mathrm{NiFe}})$ MR ( t NiFe ) ratio for fixed $\mathbf{t}_\mathbf{zr}$ t zr is obtained and it shows a maxima peak of the MR with a value of 1.8 % located at $\mathbf{t}_\mathbf{NiFe}= 80$ t NiFe = 80 Å.  相似文献   

10.
Using algebraic methods, we find the three-loop relation between the bare and physical couplings of one-flavourD-dimensional QED, in terms of Γ functions and a singleF 32 series, whose expansion nearD=4 is obtained, by wreath-product transformations, to the order required for five-loop calculations. Taking the limitD→4, we find that the \(\overline {MS} \) coupling \(\bar \alpha (\mu )\) satisfies the boundary condition $$\begin{gathered} \frac{{\bar \alpha (m)}}{\pi } = \frac{\alpha }{\pi } + \frac{{15}}{{16}}\frac{{\alpha ^3 }}{{\pi ^3 }} + \left\{ {\frac{{11}}{{96}}\zeta (3) - \frac{1}{3}\pi ^2 \log 2} \right. \hfill \\ \left. { + \frac{{23}}{{72}}\pi ^2 - \frac{{4867}}{{5184}}} \right\}\frac{{\alpha ^4 }}{{\pi ^4 }} + \mathcal{O}(\alpha ^5 ), \hfill \\ \end{gathered} $$ wherem is the physical lepton mass and α is the physical fine structure constant. Combining this new result for the finite part of three-loop on-shell charge renormalization with the recently revised four-loop term in the \(\overline {MS} \) β-function, we obtain $$\begin{gathered} \Lambda _{QED}^{\overline {MS} } \approx \frac{{me^{3\pi /2\alpha } }}{{(3\pi /\alpha )^{9/8} }}\left( {1 - \frac{{175}}{{64}}\frac{\alpha }{\pi } + \left\{ { - \frac{{63}}{{64}}\zeta (3)} \right.} \right. \hfill \\ \left. { + \frac{1}{2}\pi ^2 \log 2 - \frac{{23}}{{48}}\pi ^2 + \frac{{492473}}{{73728}}} \right\}\left. {\frac{{\alpha ^2 }}{{\pi ^2 }}} \right), \hfill \\ \end{gathered} $$ at the four-loop level of one-flavour QED.  相似文献   

11.
Quasi solid state dye-sensitized solar cells (DSSCs) have been fabricated with electrolytes containing $\text{ I }^{-}/\text{ I }_{3}^{-}$ redox couple using 80 % hydrolyzed polyvinyl alcohol (PVA) doped with potassium iodide (KI) and a mixture of potassium iodide and tetrapropyl ammonium iodide ( $\text{ Pr }_{4}\text{ NI }$ ) salts. The quasi solid state gel polymer electrolytes were prepared using 1:1 ethylene carbonate (EC):propylene carbonate (PC) mixture. The solar cells have the structure of ITO/ $\text{ TiO }_{2}$ /N3-Dye/electrolyte/Pt/ITO. The conductivity of the electrolytes has been calculated from the bulk resistance value determined using the electrochemical impedance spectroscopy. The performance of the DSSCs has been studied by varying the concentration of the doping salts in the electrolyte and incident light intensity. The DSSC fabricated with the KI salt electrolyte containing 9.9 wt% PVA, 39.6 wt% EC, 39.6 wt% PC, 10.9 wt% KI $(+\text{ I }_{2})$ exhibited the best power conversion efficiency of 1.97 %. However, the DSSC with a double-salt electrolyte containing 9.9 wt% PVA: 39.6 wt% EC: 39.6 wt% PC: (6.5 wt% KI: 4.4 wt% $\text{ Pr }_{4}\text{ NI }$ ) ( $+\text{ I }_{2}$ ) exhibited a higher efficiency of 3.27% under $100 \text{ mW/cm }^{2}$ light intensity. The efficiency of this cell increased to 4.59 % under dimmer light of intensity of $54 \text{ mW/cm }^{2}$ .  相似文献   

12.
Femtosecond (fs) laser pulses at variable delay times allowed us to track the fast non-radiative transitions between the manifold of highly excited $\mathrm{M}_{\mathrm{Na}}^{**}$ states to the lower lying fluorescent $\mathrm{M}_{\mathrm{Na}}^{*}$ state in CaF2. Two distinct $\mathrm{M}_{\mathrm{Na}}^{**}$ states of the manifold at 3.16?eV ( $\mathrm{M}_{\mathrm{Na}2}^{**}$ ) and 4.73?eV ( $\mathrm{M}_{\mathrm{Na}3}^{**}$ ) were populated using the second (SH) and third harmonics (TH) of fs laser light at 785?nm. The population kinetics of the fluorescent $\mathrm{M}_{\mathrm{Na}}^{*}$ state in the 2?eV excitation energy range was revealed by depleting its fluorescence centered at 740?nm using fundamental near infrared (NIR) fs laser pulses. The related time constants for $\mathrm{M}_{\mathrm{Na}2,3}^{**}{\sim}{>} \mathrm{M}_{\mathrm{Na}}^{*}$ relaxation amounted to 1.0±0.14?ps and 3.0±0.3?ps upon SH and TH excitation, respectively.  相似文献   

13.
A full ligand-field energy matrix diagonalization treatment for 3d 1 ions in tetragonal symmetry is developed on the basis of the two spin?Corbit coupling parameter model, and the contributions of the spin?Corbit coupling of the ligand ions to the optical and electron paramagnetic resonance spectra are included. Spin Hamiltonian parameters of the tetragonal ${\rm V}^{4+}$ center in $\hbox{K}_2\hbox{SO}_4 {-} \hbox{Na}_2\hbox{SO}_4{-}\hbox{ZnSO}_4$ glass are calculated from the complete energy matrix diagonalization and the perturbation theory methods. The results calculated by both methods are not only close to each other but also in good agreement with the experimental values. Furthermore, the compressed defect structure of the ${\rm (VO_6)^{8-}}$ cluster is discussed.  相似文献   

14.
Tensor meson dominance combined with vector meson dominance, QCD-potentials and the experimental leptonic widths of Γ and Γ′ predicts $$\Gamma _{\Upsilon '\left( {10.01} \right) \to \gamma 2^{ + + } \left( {\bar bb} \right)} = 2.8keV$$ and $$\Gamma _{2^{ + + } \left( {\bar bb} \right) \to \gamma \Upsilon \left( {9.46} \right)} = 134keV.$$ The angular distributions of the γ and the jetsj resulting from the decays $$e^ + e^ - \to \Upsilon '\left( {10.01} \right) \to \gamma 2^{ + + } \left( {\bar bb} \right) \to \gamma gg \to \gamma jj$$ and $$e^ + e^ - \to \Upsilon '\left( {10.01} \right) \to \gamma 2^{ + + } \left( {\bar bb} \right) \to \gamma \bar qq \to \gamma jj$$ with massless vector gluonsg, (coupled gauge invariantly) and quarksq are uniquely determined in TMD. The result for the first process agrees with that of perturbative QCD. No perturbative QCD-prediction for the latter is known.  相似文献   

15.
We calculate, exactly, the next-to-leading correction to the relation between the \(\overline {MS} \) quark mass, \(\bar m\) , and the scheme-independent pole mass,M, and obtain $$\begin{gathered} \frac{M}{{\bar m(M)}} \approx 1 + \frac{4}{3}\frac{{\bar \alpha _s (M)}}{\pi } + \left[ {16.11 - 1.04\sum\limits_{i = 1}^{N_F - 1} {(1 - M_i /M)} } \right] \hfill \\ \cdot \left( {\frac{{\bar \alpha _s (M)}}{\pi }} \right)^2 + 0(\bar \alpha _s^3 (M)), \hfill \\ \end{gathered} $$ as an accurate approximation forN F?1 light quarks of massesM i <M. Combining this new result with known three-loop results for \(\overline {MS} \) coupling constant and mass renormalization, we relate the pole mass to the \(\overline {MS} \) mass, \(\bar m\) (μ), renormalized at arbitrary μ. The dominant next-to-leading correction comes from the finite part of on-shell two-loop mass renormalization, evaluated using integration by parts and checked by gauge invariance and infrared finiteness. Numerical results are given for charm and bottom \(\overline {MS} \) masses at μ=1 GeV. The next-to-leading corrections are comparable to the leading corrections.  相似文献   

16.
The mutually unbiasedness between a maximally entangled basis (MEB) and an unextendible maximally entangled system (UMES) in the bipartite system \(\mathbb {C}^{2}\otimes \mathbb {C}^{2^{k}} (k>1)\) are introduced and discussed first in this paper. Then two mutually unbiased pairs of a maximally entangled basis and an unextendible maximally entangled system are constructed; lastly, explicit constructions are obtained for mutually unbiased MEB and UMES in \(\mathbb {C}^{2}\otimes \mathbb {C}^{4}\) and \(\mathbb {C}^{2}\otimes \mathbb {C}^{8}\), respectively.  相似文献   

17.
The process p $ \bar{{p}}$ $ \rightarrow$ $ \Lambda_{c}^{+}$ $ \bar{{\Lambda}}_{c}^{-}$ is investigated within the handbag approach. It is shown to lowest order of perturbative QCD that, under the assumption of restricted parton virtualities and transverse momenta, the dominant dynamical mechanism, characterized by the partonic subprocess u $ \bar{{u}}$ $ \rightarrow$ c $ \bar{{c}}$ , factorizes in the sense that only the subprocess contains highly virtual partons, namely a gluon, while the hadronic matrix elements embody only soft scales and can be parameterized in terms of helicity flip and non-flip generalized parton distributions. Modelling the latter functions by overlaps of light-cone wave functions for the involved baryons we are able to predict cross-sections and spin correlation parameters for the process of interest.  相似文献   

18.
19.
The available data on \(|\Delta B| = |\Delta S| = 1\) decays are in good agreement with the Standard Model when permitting subleading power corrections of about \(15\,\%\) at large hadronic recoil. Constraining new-physics effects in \(\mathcal {C}_{7}^{\mathrm {}}\) , \(\mathcal {C}_{9}^{\mathrm {}}\) , \(\mathcal {C}_{10}^{\mathrm {}}\) , the data still demand the same size of power corrections as in the Standard Model. In the presence of chirality-flipped operators, all but one of the power corrections reduce substantially. The Bayes factors are in favor of the Standard Model. Using new lattice inputs for \(B\rightarrow K^*\) form factors and under our minimal prior assumption for the power corrections, the favor shifts toward models with chirality-flipped operators. We use the data to further constrain the hadronic form factors in \(B\rightarrow K\) and \(B\rightarrow K^*\) transitions.  相似文献   

20.
We extend from \(B^0 - \overline {B^0 } to T^0 - \overline {T^0 } \) the study of neutral pseudoscalar mesons with respect to mixing and CP violation. The possibility of a quite large top quark mass necessitates a more careful computation of the box diagram amplitude. Our result is that, while in \(B^0 - \overline {B^0 } \) systems CP violation is expected to be very small (~10?6) and mixing quite large (10–20% or more), precisely the opposite occurs for \( T^0 - \overline {T^0 } \) . In particular, CP violation in the \( T_u^0 - \overline {T_u^0 } \) system could be of the same order of magnitude as in the \(K^0 - \overline {K^0 } \) system (~10?3) while the mixing is totally negligible.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号