7,806 research outputs found
Molecular states with hidden charm and strange in QCD Sum Rules
This work uses the QCD Sum Rules to study the masses of the
and molecular states with quantum numbers . Interpolating currents with definite C-parity are employed, and the
contributions up to dimension eight in the Operator Product Expansion (OPE) are
taken into account. The results indicate that two hidden strange
charmonium-like states may exist in the energy ranges of GeV
and GeV, respectively. The hidden strange charmonium-like
states predicted in this work may be accessible in future experiments, e.g.
BESIII, BelleII and SuperB. Possible decay modes, which may be useful in
further research, are predicted.Comment: 15 pages, 6 figures, 2 tables, to appear in EP
Estimating the mass of the hidden charm tetraquark state via QCD sum rules
By using QCD sum rules, the mass of the hidden charm tetraquark
state with (HCTV) is
estimated, which presumably will turn out to be the newly observed
charmonium-like resonance . In the calculation, contributions up
to dimension eight in the operator product expansion(OPE) are taken into
account. We find , which is
consistent, within the errors, with the experimental observation of
. Extending to the b-quark sector, is obtained. The calculational result
strongly supports the tetraquark picture for the "exotic" states of
and .Comment: 13 pages,3 figures, 1 table, version to appear in EPJ
Mass Spectra of , , and Exotic Glueballs
With appropriate interpolating currents the mass spectra of ,
, and oddballs are studied in the framework of QCD sum rules
(QCDSR). We find there exits one stable oddball with mass of , and one stable oddball with mass of , whereas, no stable oddball shows up. The possible
production and decay modes of these glueballs with unconventional quantum
numbers are analyzed, which are hopefully measurable in either BELLEII, PANDA,
Super-B or LHCb experiments.Comment: 10 pages, 12 figures, 4 tables, to appear in NPB. arXiv admin note:
substantial text overlap with arXiv:1408.399
Interpretation of as the Hidden Charm Tetraquark States via QCD Sum Rules
By using QCD Sum Rules, we found that the charged hidden charm tetraquark states with and , which are possible
quantum numbers of the newly observed charmonium-like resonance ,
have masses of and . The contributions up to dimension eight in the
Operator Product Expansion (OPE) were taken into account in the calculation.
The tetraquark mass of state was consistent with the
experimental data of , suggesting the state possessing
the quantum number of . Extending to the b-quark sector, the
corresponding tetraquark masses
and were obtained, which are
testable in future B-factories.Comment: 15 pages, 6 figures, to appear in European Physical Journal
Singular Value Computation and Subspace Clustering
In this dissertation we discuss two problems. In the first part, we consider the problem of computing a few extreme eigenvalues of a symmetric definite generalized eigenvalue problem or a few extreme singular values of a large and sparse matrix. The standard method of choice of computing a few extreme eigenvalues of a large symmetric matrix is the Lanczos or the implicitly restarted Lanczos method. These methods usually employ a shift-and-invert transformation to accelerate the speed of convergence, which is not practical for truly large problems. With this in mind, Golub and Ye proposes an inverse-free preconditioned Krylov subspace method, which uses preconditioning instead of shift-and-invert to accelerate the convergence. To compute several eigenvalues, Wielandt is used in a straightforward manner. However, the Wielandt deflation alters the structure of the problem and may cause some difficulties in certain applications such as the singular value computations. So we first propose to consider a deflation by restriction method for the inverse-free Krylov subspace method. We generalize the original convergence theory for the inverse-free preconditioned Krylov subspace method to justify this deflation scheme. We next extend the inverse-free Krylov subspace method with deflation by restriction to the singular value problem. We consider preconditioning based on robust incomplete factorization to accelerate the convergence. Numerical examples are provided to demonstrate efficiency and robustness of the new algorithm.
In the second part of this thesis, we consider the so-called subspace clustering problem, which aims for extracting a multi-subspace structure from a collection of points lying in a high-dimensional space. Recently, methods based on self expressiveness property (SEP) such as Sparse Subspace Clustering and Low Rank Representations have been shown to enjoy superior performances than other methods. However, methods with SEP may result in representations that are not amenable to clustering through graph partitioning. We propose a method where the points are expressed in terms of an orthonormal basis. The orthonormal basis is optimally chosen in the sense that the representation of all points is sparsest. Numerical results are given to illustrate the effectiveness and efficiency of this method
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