167 research outputs found

    Proposed Search for a00(980)f0(980)a^0_0(980)-f_0(980) Mixing in Polarization Phenomena

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    The K+K^+ and K0K^0 meson mass difference induces the mixing of the a00(980)a^0_0(980) and f0(980)f_0(980) resonances, the amplitude of which, between the K+KK^+K^- and K0Kˉ0K^0\bar K^0 thresholds, is large in magnitude, of the order of mKmK02mK+2αmK2 m_{K}\sqrt{m^2_{K^0}-m^2_{K^+}}\approx\sqrt\alpha m^2_K, and possesses the phase sharply varying by about 90^\circ. We suggest performing the polarized target experiments on the reaction πpηπ0n\pi^-p\to\eta\pi^0n at high energy in which the fact of the existence of a00(980)f0(980)a^0_0(980)-f_0(980) mixing can be unambiguously and very easily established through the presence of a strong jump in the azimuthal asymmetry of the ηπ0\eta\pi^0 SS wave production cross section near the KKˉK\bar K thresholds. The presented estimates of the polarization effect to be expected in experiment are to a great extent model independent.Comment: RevTeX, 9 pages, 1 figure. A number of typographical and grammatical errors correcte

    Amplitude analysis of reactions pi(-)p->etapi(-)p and pi(-)p->etapi(0)n on polarized target and the exotic 1-+ meson

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    Recently several experimental groups analysed data on πpηπp\pi^- p \to \eta \pi^- p and πpηπ0n\pi^- p \to \eta \pi^0 n reactions with exotic 1+1^{-+} PP-wave and found a conflicting evidence for an exotic meson I=11+(1405)I=1 1^{-+} (1405). High statistics data on these reactions are presently analysed by BNL E852 Collaboration. All these analyses are based on the crucial assumption that the production amplitudes do not depend on nucleon spin. This assumption is in sharp conflict with the results of measurements of πpππ+n\pi^- p \to \pi^- \pi^+ n, π+nπ+πp\pi^+ n \to \pi^+ \pi^- p and K+nK+πpK^+ n \to K^+ \pi^- p on polarized targets at CERN which find a strong dependence of production amplitudes on nucleon spin. To ascertain the existence of exotic meson 1+(1405)1^{-+} (1405), it is necessary to perform a model-independent amplitude analysis of reactions πpηπp\pi^- p \to \eta \pi^- p and πpηπ0n\pi^- p \to \eta\pi^0 n. We demonstrate that measurements of these reactions on transversely polarized targets enable the required model independent amplitude analysis without the assumption that production amplitudes are independent on nucleon spin. We suggest that high statistics measurements of reactions πpηπp\pi^- p \to \eta\pi^- p and πpηπ0n\pi^- p \to\eta\pi^0 n be made on polarized targets at BNL and at Protvino IHEP, and that model-independent amplitude analyses of this polarized data be performed to advance hadron spectroscopy on the level of spin dependent production amplitudes.Comment: 23 page

    Surface magnetism in iron, cobalt, and nickel

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    ππ\pi\pi scattering S wave from the data on the reaction πpπ0π0n\pi^-p\to\pi^0\pi^0n

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    The results of the recent experiments on the reaction πpπ0π0n\pi^-p\to\pi^0\pi^0n performed at KEK, BNL, IHEP, and CERN are analyzed in detail. For the I=0 ππ\pi\pi S wave phase shift δ00\delta^0_0 and inelasticity η00\eta^0_0 a new set of data is obtained. Difficulties emerging when using the physical solutions for the π0π0\pi^0\pi^0 S and D wave amplitudes extracted with the partial wave analyses are discussed. Attention is drawn to the fact that, for the π0π0\pi^0\pi^0 invariant mass, m, above 1 GeV, the other solutions, in principle, are found to be more preferred. For clarifying the situation and further studying the f0(980)f_0(980) resonance thorough experimental investigations of the reaction πpπ0π0n\pi^-p\to\pi^0\pi^0n in the m region near the KKˉK\bar K threshold are required.Comment: 17 pages, 5 figure

    Unquenching the scalar glueball

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    Computations in the quenched approximation on the lattice predict the lightest glueball to be a scalar in the 1.5-1.8 GeV region. Here we calculate the dynamical effect the coupling to two pseudoscalars has on the mass, width and decay pattern of such a scalar glueball. These hadronic interactions allow mixing with the qqq \overline q scalar nonet, which is largely fixed by the well-established K_0^*(1430). This non-perturbative mixing means that, if the pure gluestate has a width to two pseudoscalar channels of ~100 MeV as predicted on the lattice, the resulting hadron has a width to these channels of only ~30 MeV with a large eta-eta component. Experimental results need to be reanalyzed in the light of these predictions to decide if either the f_0(1500) or an f_0(1710) coincides with this dressed glueball.Comment: 12 pages, LaTex, 3 Postscript figure

    DGLAP analyses of nPDF: constraints from data

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    We explain how the constraints from present experimental data can be used to obtain the nPDF in the framework of LO DGLAP evolution. We will also compare the only two available sets of this type and comment on the important information that neutrino factories could provide.Comment: 1 pages, 1 postscript figure. Invited talk at the NuFact'02 workshop (Neutrino Factories based on Muon Storage Rings), London, July 200

    Another look at ππ\pi\pi scattering in the scalar channel

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    We set up a general framework to describe ππ\pi\pi scattering below 1 GeV based on chiral low-energy expansion with possible spin-0 and 1 resonances. Partial wave amplitudes are obtained with the N/DN/D method, which satisfy unitarity, analyticity and approximate crossing symmetry. Comparison with the phase shift data in the J=0 channel favors a scalar resonance near the ρ\rho mass.Comment: 17 pages, 5 figures, REVTe

    Screening and Anti-Screening Effects in J/psi Production on Nuclei

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    The nuclear effects in J/psi hadro- and electroproduction on nuclei are considered in framework of reggeon approach. It is shown that screening regime which holds for electroproduction at x_F > 0.7 and for hadroproduction at x_F > -(0.3-0.4) is changed with anti-screening regime for smaller x_F values.Comment: 6 pages, 6 figures. Small changes in wordin

    Coherence Time in High Energy Proton-Nucleus Collisions

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    Precisely measured Drell-Yan cross sections for 800 GeV protons incident on a variety of nuclear targets exhibit a deviation from linear scaling in the atomic number A. We show that this deviation can be accounted for by energy degradation of the proton as it passes through the nucleus if account is taken of the time delay of particle production due to quantum coherence. We infer an average proper coherence time of 0.4 +- 0.1 fm/c, corresponding to a coherence path length of 8 +- 2 fm in the rest frame of the nucleus.Comment: 11 pages in LaTeX. Includes 6 eps figures. Uses epsf.st

    Manifestation of the a00(980)f0(980)a^0_0(980)-f_0(980) mixing in the reaction πpηπ0n\pi^-p\to\eta\pi^0n on a polarized target

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    It is argued that the single-spin asymmetry in the reaction πpa00(980)n(ηπ0)Sn\pi^-p\to a_0^0(980)n\to(\eta\pi^0)_S n is extremely sensitive to the mixing of the a00(980)a^0_0(980) and f0(980)f_0(980) resonances. It is shown that at low momentum transfers (namely, in any one of the intervals 0t0.025,...,0.10\leq-t\leq0.025,...,0.1 GeV2^2) the normalized asymmetry, which can take the values from -1 to 1, must undergo a jump in magnitude close to 1 in the ηπ0\eta\pi^0 invariant mass region between 0.965 GeV and 1.01 GeV. The strong asymmetry jump is the straightforward manifestation of the a00(980)f0(980)a^0_0(980)-f_0(980) mixing. For observing the jump, any very high quality ηπ0\eta\pi^0 mass resolution is not required. The energy dependence of the polarization effect is expected to be rather weak. Therefore, it can be investigated at any high energy, for example, in the range from eight to 100 GeV.Comment: 19 pages, 7 figures. Three figures and discussion added; version published in PR
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