118703610
Hybrid Baryons in QCD
In this study, we present the first comprehensive study of hybrid baryons using lattice QCD methods. Using a large basis of composite QCD interpolating fields we extract an extensive spectrum of baryon states and isolate those of hybrid character using their relatively large overlap onto operators which sample gluonic excitations. We consider the spectrum of Nucleon and Delta states at several quark masses finding a set of positive parity hybrid baryons with quantum numbers $$N_{1/2^+},\,N_{1/2^+},\,N_{3/2^+},\, N_{3/2^+},\,N_{5/2^+},\,$$ and $$\Delta_{1/2^+},\, \Delta_{3/2^+}$$ at an energy scale above the first band of `conventional' excited positive parity baryons. This pattern of states is compatible with a color octet gluonic excitation having $$J^{P}=1^{+}$$ as previously reported in the hybrid meson sector and with a comparable energy scale for the excitation, suggesting a common bound-state construction for hybrid mesons and baryons.
14262604
Hybrid meson production by electromagnetic and weak interactions in a flux tube simulation of lattice QCD
We calculate rates for hybrid meson production by electromagnetic and weak interactions in the flux-tube model. Applications include photo and electroproduction at Jefferson Laboratory and HERA, and the production of light strange and charmed hybrids in the weak decays of heavy flavours. Photoproduction of some light hybrids is predicted to be prominent in charge exchange reactions, $\gamma p \to n \cal{H}$ and accessible in $\gamma p \to p \cal{H}$. Production of light or charmed hybrids in $B$ and $D$ decays may be feasible with high statistics. Photoproduction of the axial hybrid meson is predicted to be large courtesy of $\pi$ exchange, and its strange counterpart is predicted in $B \to \psi K_H(1^+)$ with $b.r. \sim 10^{-4}$. Production rates for exotic hybrid candidates $1^{-+};(0,2)^{+-}$ are given special attention. Selection rules that can help to distinguish between hybrid and conventional states with the same $J^{PC}$ are noted.
120601853
Radiative Physics in Charmonium from Lattice QCD
Charmonium is an attractive system for the application of lattice QCD methods owing to the possibility of computing with the physical quark mass in a reasonable time. While the sub-threshold spectrum has been considered in some detail in previous works, it is only very recently that further properties such as radiative transitions and two-photon decays have come to be calculated; herein we discuss this recent progress.
15493314
Pentaquark implications for exotic mesons
If the exotic baryon {theta}{sup +}(1540) is a correlated ududs with J{sup P}=(1{sup +}/2), then there should exist an exotic meson {theta}{sup +} with strangeness +2, J{sup P}=1{sup -}, mass {approx}1.6 GeV, decaying to K{sup +}K{sup 0} with width O(10-100) MeV. The {pi}{sub 1}(1400;1600) may be broad members of 10{+-}10 in such a picture, and it is possible that vector mesons in the 1.4-1.7 GeV mass range are related to this multiplet. We suggest that dynamical correlations may limit the spectrum of J{sup P(C)} such that the 1{sup -({+-}}{sup )} states are isolated.
16434102
Pentaquark symmetries, selection rules and another potentially narrow state
Abstract We identify essential differences between the pentaquark and chiral soliton models of 10 5 and 8 5 pentaquarks and conventional 8 3 states, which are experimentally measurable. We show how the decays of Ξ5 states in particular can test models of the pentaquarks, recommend study of the relative branching ratios of, e.g., Ξ − 5 →Ξ − π 0 :Ξ 0 π − , and predict that the decay amplitude Ξ 5 →Ξ ∗ π is zero at leading order in pentaquark models for any mixture of 10 and the associated 8 5 . We also include a pedagogic discussion of wavefunctions in the pentaquark picture and show that pentaquark models have this 8 5 with F/D=1/3, in leading order forbidding Ξ5→ΛK. The role of Fermi–Dirac symmetry in the qqqq wavefunction and its implications for the width of pentaquarks are briefly discussed. The relative couplings g 2 (Θ Q NK Q ∗ )/g 2 (Θ Q NK Q )=3 for Q≡s,c,b. A further potentially narrow state Λ in 8 5 with JP=3/2+ is predicted around 1650 MeV.
125997156
Charmonium Radiative Physics
122253058
Fock-space diagonalization of the state-dependent pairing Hamiltonian with the Woods-Saxon mean field
A particle-number conserving approach is presented to solve the nuclear mean-field plus pairing Hamiltonian problem with a realistic deformed Woods-Saxon single-particle potential. The method is designed for the state-dependent monopole pairing Hamiltonian {cflx H}{sub pair}={summation}{sub {alpha}{beta}}G{sub {alpha}{beta}}c{sub {alpha}}{sup {dagger}}c{sub {bar {alpha}}}{sup {dagger}}c{sub {bar {beta}}}c{sub {beta}} with an arbitrary set of matrix elements G{sub {alpha}{beta}}. Symmetries of the Hamiltonians on the many-body level are discussed using the language of P symmetry introduced earlier in the literature and are employed to diagonalize the problem; the only essential approximation used is a many-body (Fock-space) basis cutoff. An optimal basis construction is discussed and the stability of the final result with respect to the basis cutoff is illustrated in details. Extensions of the concept of P symmetry are introduced and their consequences for an optimal many-body basis cutoff construction are exploited. An algorithm is constructed allowing to solve the pairing problems in the many-body spaces corresponding to p{approximately}40 particles on n{approximately}80 levels and for several dozens of lowest lying states with precision {approximately}(1{endash}2) {percent} within seconds of the CPU time on a CRAY computer. Among applications, the presence of the low-lying seniority s=0 solutions, that are usually poorly described in terms of the standardmore » approximations (BCS, HFB), is discussed and demonstrated to play a role in the interpretation of the spectra of rotating nuclei. {copyright} {ital 1997} {ital The American Physical Society}« less
122414594
Nuclear shell structure at very high angular momentum
Abstract A cranked modified-oscillator model (with triaxial shape coordinates ϵ and γ) is used to study the nuclear potential-energy surface (based on a Strutinsky type of shell correction method) for very high angular momenta (30 ≦ I ≦ 100). For this region of spin, pair correlation is assumed to have collapsed. The influence of rapid rotation on the shell structure has been studied in the light and heavy rare-earth region as well as the Te-Ba region. Preliminary studies have also been made in the regions of superheavy and light nuclei. The possible occurrence of yrast traps is discussed.
24677742
Critical frequency in nuclear chiral rotation.
Self-consistent solutions for the so-called planar and chiral rotational bands in 132La are obtained for the first time within the Skyrme-Hartree-Fock cranking approach. It is suggested that the chiral rotation cannot exist below a certain critical frequency which under the approximations used is estimated as Planck's omega(crit) approximately 0.5-0.6 MeV. However, the exact values of Planck's omega(crit) may vary, to an extent, depending on the microscopic model used, in particular, through the pairing correlations and/or calculated equilibrium deformations. The existence of the critical frequency is explained in terms of a simple classical model of two gyroscopes coupled to a triaxial rigid body.
55630915
Probing nuclear shapes close to the fission limit with the giant dipole resonance in 216 Rn
The gamma-ray decay of the giant dipole resonance (GDR) in the compound nucleus {sup 216}Rn formed with the reaction {sup 18}O+{sup 198}Pt at the bombarding energy of 96 MeV was investigated. High-energy gamma-ray spectra in coincidence with both prompt and delayed low-energy transitions were measured. The obtained GDR width at the average temperature {approx_equal}1 MeV was found to be larger than that at T=0 MeV and to be approximately constant as a function of spin. The measured width value of 7 MeV is found to be consistent with the predictions based on calculations of the nuclear shape distribution using the newest approach for the treatment of the fission barrier within the liquid drop model. The present study is the first investigation of the giant dipole resonance width from the fusion-evaporation decay channel in this nuclear mass range.
18751256
ROTATION OF TETRAHEDRAL NUCLEI IN THE CRANKING MODEL
The three-dimensional cranking model is used to investigate the microscopic aspects of the rotation of nuclei with the tetrahedral symmetry. Two classes of rotation axes are studied corresponding to two different discrete symmetries of the rotating hamiltonian. Self-consistent Hartree-Fock-Bogoliubov calculations show that the tetrahedral minimum remains remarkably stable until the first single-particle crossing.