214 research outputs found
PL25: Glueballs and other
No full text. Experimental evidence has become strong for an exotic, non-¯qq resonance at 1400 MeV with J PC = 1 \Gamma+ . Among 0 \Gamma+ ; 1 +\Gamma and 2 ++ mesons, the best candidates for non-¯qq states are still weak. The extraordinary and difficult sector of isoscalar 0 ++ (f0) mesons approaches experimental consistency; theoretical explanations of the observed states need the glueball component. 1 Introduction The main task of meson spectroscopy today is to verify or falsify the existence of non-¯qq mesons predicted by Quantumchromodynamics (QCD). Non-¯qq is a short name for mesons whose constituents are not just a quark and an antiquark. The constituents could be, for instance, two gluons, forming a glueball. It is not obvious that gluons, even if they carry colour and attract other gluons, will form bound states [1]. The massless gauge gluons of QCD have to get dressed in a similar way as current quarks in order to behave like massive constituents of a hadron. The notion of a..
A microscopic derivation of nuclear collective rotation-vibration model, axially symmetric case
No full textWe derive a microscopic version of the successful phenomenological hydrodynamic model of Bohr-Davydov-Faessler-Greiner for collective rotation-vibration motion of an axially symmetric deformed nucleus. The derivation is not limited to small oscillation amplitudes. The nuclear Schrodinger equation is canonically transformed to collective co-ordinates, and then linearized using a constrained variational method. The associated constraints are imposed on the wavefunction rather than on the particle co-ordinates. The approach yields three self-consistent, time-reversal invariant, cranking-type Schrodinger equations for the rotation-vibration and intrinsic motions, and a self-consistency equation. For harmonic oscillator mean-field potentials, these equations are solved in closed forms and applied to the ground-state rotational bands in some axially-symmetric nuclei. The results are compared with those of other models and related measured data.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Resonances of the systems and in the reactions and at COMPASS
No full textWe describe partial-wave analyses of the systems \pi-\eta and \pi-\eta' produced in interactions of a \pi- beam (190 GeV/c) with a liquid hydrogen target. The data were recorded during the 2008 COMPASS run, where a slow recoiling proton (|t|>0.1 GeV^2) was required by the trigger. We compare analyses of the \pi-\eta and \pi-\eta' data. Significant contributions can be attributed to the resonances a_2(1320), observed in the D_+-wave, and a_4(2040), observed in the G_+-wave. Between the two systems, we find similar compositions of the even partial waves D_+ and G_+ after taking phase-space factors into account, but a much enhanced P_+-wave in \pi-\eta'. Relative phase-differences indicate a large incoherent contribution of in the P_+-wave of the \eta'\pi- system, but other interpretations are not excluded. The known resonances a_2(1320), a_4(2040) and their parameters could be extracted from the data; their branchings are found to roughly agree with predictions from \eta\eta' mixing.We describe partial-wave analyses of the systems \pi-\eta and \pi-\eta' produced in interactions of a \pi- beam (190 GeV/c) with a liquid hydrogen target. The data were recorded during the 2008 COMPASS run, where a slow recoiling proton (|t|>0.1 GeV^2) was required by the trigger. We compare analyses of the \pi-\eta and \pi-\eta' data. Significant contributions can be attributed to the resonances a_2(1320), observed in the D_+-wave, and a_4(2040), observed in the G_+-wave. Between the two systems, we find similar compositions of the even partial waves D_+ and G_+ after taking phase-space factors into account, but a much enhanced P_+-wave in \pi-\eta'. Relative phase-differences indicate a large incoherent contribution of in the P_+-wave of the \eta'\pi- system, but other interpretations are not excluded. The known resonances a_2(1320), a_4(2040) and their parameters could be extracted from the data; their branchings are found to roughly agree with predictions from \eta\eta' mixing
Boltzmann's H-theorem, its limitations, and the birth of (fully) statistical mechanics
No full textA comparison is made of the traditional Loschmidt (reversibility) and Zermelo (recurrence) objections to Boltzmann's H-theorem, and its simplified variant in the Ehrenfests' 1912 wind-tree model. The little-cited 1896 (pre-recurrence) objection of Zermelo (similar to an 1889 argument due to Poincare) is also analysed. Significant differences between the objections are highlighted, and several old and modern misconceptions concerning both them and the H-theorem are clarified. We give particular emphasis to the radical nature of Poincare's and Zermelo's attack, and the importance of the shift in Boltzmann's thinking in response to the objections as a whole
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