482,289 research outputs found

    Decay width of d(2380)NNπd^*(2380) \to NN \pi process in a chiral constituent quark model

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    The width of three-body single-pion decay process dNNπ0,±d^*\to NN\pi^{0,\pm} is calculated by using the dd^* wave function obtained from our chiral SU(3) constituent quark model calculation. The effect of the dynamical structure on the width of dd^* is taken into account in both the single ΔΔ\Delta\Delta channel and coupled ΔΔ+CC\Delta\Delta+CC two-channel approximations. Our numerical result shows that in the coupled-channel approximation, namely, the hidden-color configuration being considered, the obtained partial decay width of dNNπd^*\to NN\pi is about several hundred KeV\rm {KeV}, while in the single ΔΔ\Delta\Delta channel it is just about 23 MeV2\sim 3~\rm{MeV}. We, therefore, conclude that the partial width in the single-pion decay process of dd^* is much smaller than the widths in its double-pion decay processes. Our prediction may provide a criterion for judging different interpretations of the dd^* structure, as different pictures for the dd^* may result quite different partial decay width.Comment: 6 pages, 1 figure, and 1 table, typos correcte

    Haldane, Large-D and Intermediate-D States in an S=2 Quantum Spin Chain with On-Site and XXZ Anisotropies

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    Using mainly numerical methods, we investigate the ground-state phase diagram of the S=2 quantum spin chain described by H=j(SjxSj+1x+SjySj+1y+ΔSjzSj+1z)+Dj(Sjz)2H = \sum_j (S_j^x S_{j+1}^x + S_j^y S_{j+1}^y + \Delta S_j^z S_{j+1}^z) + D \sum_j (S_j^z)^2, where Δ\Delta denotes the XXZXXZ anisotropy parameter of the nearest-neighbor interactions and DD the on-site anisotropy parameter. We restrict ourselves to the case with Δ0\Delta \ge 0 and D0D \ge 0 for simplicity. Each of the phase boundary lines is determined by the level spectroscopy or the phenomenological renormalization analysis of numerical results of exact-diagonalization calculations. The resulting phase diagram on the Δ\Delta-DD plane consists of four phases; the XY 1 phase, the Haldane/large-DD phase, the intermediate-DD phase and the N\'eel phase. The remarkable natures of the phase diagram are: (1) the Haldane state and the large-DD state belong to the same phase; (2) there exists the intermediate-DD phase which was predicted by Oshikawa in 1992; (3) the shape of the phase diagram on the Δ\Delta-DD plane is different from that believed so far. We note that this is the first report of the observation of the intermediate-DD phase

    Electroproduction of the d* dibaryon

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    The unpolarized cross section for the electroproduction of the isoscalar Jπ=3+J^\pi = 3^+ di-delta dibaryon dd^* is calculated for deuteron target using a simple picture of elastic electron-baryon scattering from the ΔΔ(7D1)\Delta \Delta (^7D_1) and the NN(3S1)NN (^3S_1) components of the deuteron. The calculated differential cross section at the electron lab energy of 1 GeV has the value of about 0.24 (0.05) nb/sr at the lab angle of 10^\circ (30^\circ) for the Bonn B potential when the dibaryon mass is taken to be 2.1 GeV. The cross section decreases rapidly with increasing dibaryon mass. A large calculated width of 40 MeV for d(ΔΔ7S3)d^*(\Delta\Delta ^7S_3) combined with a small experimental upper bound of 0.08 MeV for the dd^* decay width appears to have excluded any low-mass dd^* model containing a significant admixture of the ΔΔ(7S3)\Delta\Delta (^7S_3) configuration.Comment: 11 journal-style pages, 8 figure

    On the role of confinement on solidification in pure materials and binary alloys

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    We use a phase-field model to study the effect of confinement on dendritic growth, in a pure material solidifying in an undercooled melt, and in the directional solidification of a dilute binary alloy. Specifically, we observe the effect of varying the vertical domain extent (δ\delta) on tip selection, by quantifying the dendrite tip velocity and curvature as a function of δ\delta, and other process parameters. As δ\delta decreases, we find that the operating state of the dendrite tips becomes significantly affected by the presence of finite boundaries. For particular boundary conditions, we observe a switching of the growth state from 3-D to 2-D at very small δ\delta, in both the pure material and alloy. We demonstrate that results from the alloy model compare favorably with those from an experimental study investigating this effect.Comment: 13 pages, 9 figures, 3 table

    Reassessment of the Collins Mechanism for Single-spin Asymmetries and the behaviour of Delta d(x) at large x.

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    It is shown that the Collins mechanism explanation of the transverse single-spin asymmetries in p^{\uparrow} p -> \pi X leads to a transversely polarized d quark density Delta_T d(x) which violates the Soffer bound when one uses several standard forms for the longitudinally polarized d quark density Delta d(x) obtained from polarized deep inelastic scattering. Imposition of the Soffer bound with these Delta d(x) yields results in hopeless disagreement with the data. Remarkably, imposition of the Soffer bound, but using parametrizations of Delta d(x) that respect the PQCD condition Delta q(x) / q(x) -> 1 as x -> 1, leads to an excellent fit to most of the data. The implications for the polarized DIS neutron longitudinal asymmetry A_1^n at large x are dramatic.Comment: 13 pages, 11 figures, 1 table and 4 figures changed. Revised version to appear in Phys. Rev.

    Woolsack 1963 volume 1 number 1

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    Table of Contents: Excessive Juvenile Detention by Richard L. Vaughn Judge of the Juvenile Court of San Diego County Bambic ALSA President Common Law Ramble by W.J. Miller Barrister-at-law General Hickman : Some points about studying law Editorial Student Bar President’s corner by Jon Gudmunds Phi Delta Phi Phi Alpha Delta Congressman UTT : Limited Test Ban Treaty Tobacco on Trial : Guilty? by Milan L. Brandon, M. D. Congressman Van Deerlin : Congressional Conflict of Interest Problem Trusts and the Estate Owner by Paul L. Crosby Life Underwriter N.Y. Life Insurance Co. Meet the Facultyhttps://digital.sandiego.edu/woolsack/1000/thumbnail.jp

    Growth Index of DGP Model and Current Growth Rate Data

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    Recently, some efforts focus on differentiating dark energy and modified gravity with the growth function δ(z)\delta(z). In the literature, it is useful to parameterize the growth rate fdlnδ/dlna=Ωmγf\equiv d\ln\delta/d\ln a=\Omega_m^\gamma with the growth index γ\gamma. In this note, we consider the general DGP model with any Ωk\Omega_k. We confront the growth index of DGP model with currently available growth rate data and find that the DGP model is still consistent with it. This implies that more and better growth rate data are required to distinguish between dark energy and modified gravity.Comment: 12 pages, 1 table, 2 figures, Latex2e; v2: discussions added, Phys. Lett. B in press; v3: published versio
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