332 research outputs found

    The p(d,p)d and p(d,p)pn reactions as a tool for the study of the short range internal structure of the deuteron

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    In recent time the deuteron structure at short distances is often treated from the point of view nonnucleonic degrees of freedom. In this paper the measurements of T-odd polarization observables using tensor polarized deuteron beam and polarized proton target or proton polarimeter are proposed to search the quark configurations inside the deuteron.Comment: 12 pages, 8 Postscript figures, submitted in Phys.Atom.Nuc

    Dynamics of 1S0^{1}S_0 diproton formation in the pd{pp}snpd\to \{pp\}_sn and pN{pp}sπpN\to \{pp\}_s\pi reactions in the GeV region

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    Mechanisms for the production of 1S0^1S_0 diproton pairs, pps{pp}_s, in the pdppsnpd\to {pp}_s n reaction are studied at proton beam energies 0.5 -- 2 GeV in kinematics similar to those of backward elastic pdpd scattering. This reaction provides valuable information on the short-range NNNN and pdpd interactions that is complementary to that investigated in the well known pddppd\to dp and dpp(0)Xdp\to p(0^\circ)X processes. The pdppsnpd\to {pp}_sn reaction is related to the subprocesses π0dpn\pi^0 d\to pn and pNppsπpN\to {pp}_s \pi using two different one--pion--exchange (OPE) diagrams. Within both these models a reasonable agreement could be obtained with the data below 1GeV. The similar energy dependence of the pd{pp}snpd\to\{pp\}_s n and pddppd\to dp cross sections and the small ratio of about 1.5% in the production of {pp}s\{pp\}_s to deuteron final states follow naturally within the OPE models.Comment: 10 pages, 7 figures, Late

    Coulomb corrections to low energy antiproton annihilation cross sections on protons and nuclei

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    We calculate, in a systematic way, the enhancement effect on antiproton-proton and antiproton-nucleus annihilation cross sections at low energy due to the initial state electrostatic interaction between the projectile and the target nucleus. This calculation is aimed at future comparisons between antineutron and antiproton annihilation rates on different targets, for the extraction of pure isospin channels.Comment: 18 pages, 4 figures (latex format

    Vector Meson Photoproduction with an Effective Lagrangian in the Quark Model

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    A quark model approach to the photoproduction of vector mesons off nucleons is proposed. Its starting point is an effective Lagrangian of the interaction between the vector meson and the quarks inside the baryon, which generates the non-diffractive s- and u- channel resonance contributions. Additional t-channel π0\pi^0 and σ\sigma exchanges are included for the ω\omega and ρ0\rho^0 production respectively to account for the large diffractive behavior in the small tt region as suggested by Friman and Soyeur. The numerical results are presented for the ω\omega and ρ\rho productions in four isospin channels with the same set of parameters, and they are in good agreement with the available data not only in ω\omega and ρ0\rho^0 productions but also in the charged ρ\rho productions where the additional t-channel σ\sigma exchange does not contribute so that it provides an important test to this approach. The investigation is also extended to the ϕ\phi photoproduction, and the initial results show that the non-diffractive behavior of the ϕ\phi productions in the large tt region can be described by the s- and u- channel contributions with significantly smaller coupling constants, which is consistent with the findings in the similar studies in the QHD framework. The numerical investigation has also shown that polarization observables are essential for identifying so-called "missing resonances".Comment: 36 pages, 10 PS figures, extended version of nucl-th/9711061 and nucl-th/9803021, submitted to PR

    Measurement of the tensor Ayy and vector Ay analyzing powers of the deuteron inelastic scattering off berillium at 5.0 GeV/c and 178 mr

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    Tensor Ayy and vector Ay analyzing powers in the inelastic scattering of deuterons with the momentum of 5.0 GeV/c on beryllium at an angle of 178 mr in the vicinity of the excitation of baryonic resonances with masses up to 1.8 GeV/c^2 have been measured. The Ayy data are in a good agreement with the previous data obtained at 4.5 and 5.5 GeV/c. The results of the experiment are compared with the predictions of the plane wave impulse approximation and \omega-meson exchange models.Comment: 18 pages, 9 figure

    New data on OZI rule violation in bar{p}p annihilation at rest

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    The results of a measurement of the ratio R = Y(phi pi+ pi-) / Y(omega pi+ pi-) for antiproton annihilation at rest in a gaseous and in a liquid hydrogen target are presented. It was found that the value of this ratio increases with the decreasing of the dipion mass, which demonstrates the difference in the phi and omega production mechanisms. An indication on the momentum transfer dependence of the apparent OZI rule violation for phi production from the 3S1 initial state was found.Comment: 11 pages, 3 PostScript figures, submitted to Physics Letter

    Measurement of the Analyzing Power in pd(pp)n\vec{p}d \to (pp)n \\with a Fast Forward 1S0^1S_0--Diproton

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    A measurement of the analyzing power AyA_y of the pd(pp)+n\vec{p}d \to (pp) + n reaction was carried out at beam energies of 0.5 and 0.8 GeV by detection of a fast forward proton pair of small excitation energy Epp<3E_{pp} < 3 MeV. The kinematically complete experiment made use of the ANKE spectrometer at the internal beam of COSY and a deuterium cluster--jet target. For the first time the SS--wave dominance in the fast diproton is experimentally demonstrated in this reaction. While at Tp=0.8T_p=0.8 GeV the measured analyzing power AyA_y vanishes, it reaches almost unity at Tp=0.5T_p=0.5 GeV for neutrons scattered at θnc.m.=167\theta_n^{c.m.}=167^\circ. The results are compared with a model taking into account one--nucleon exchange, single scattering and Δ\Delta (1232) excitation in the intermediate state. The model describes fairly well the unpolarized cross section obtained earlier by us and the analyzing power at 0.8 GeV, it fails to reproduce the angular dependence of AyA_y at 0.5 GeV.Comment: 4 pages, 4 figures, 1 tabl

    The K^{+}--->\pi^{+}\nu\bar{nu} Rare Decay in Two Higgs Doublet Model

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    The rare k+--->pi+ \nu \bar{\nu} decay is investigated in the context of type II two-Higgs-doublet model (2HDM). By using the existing experimental data of the branching ratio, restrictions on the free parameters of the model m_H, and tan\beta are obtained: tan\beta belong to the range 0.7- o.8, and m_H belong to the range 500- 700 GeV.Comment: 12 pages, latex file, 3 figures, postscript file

    Coherent pion production in neutrino nucleus collision in the 1 GeV region

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    We calculate cross sections for coherent pion production in nuclei induced by neutrinos and antineutrinos of the electron and muon type. The analogies and differences between this process and the related ones of coherent pion production induced by photons, or the (p,n) and (3He,t)(^3 He, t) reactions are discussed. The process is one of the several ones occurring for intermediate energy neutrinos, to be considered when detecting atmospheric neutrinos. For this purpose the results shown here can be easily extrapolated to other energies and other nuclei.Comment: 13 pages, LaTex, 8 post-script figures available at [email protected]

    Measurements of the reaction pˉpϕη\bar{p}p \to \phi \eta of antiproton annihilation at rest at three hydrogen target densities

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    The proton-antiproton annihilation at rest into the ϕη\phi\eta final state was measured for three different target densities: liquid hydrogen, gaseous hydrogen at NTP and at a low pressure of 5 mbar. The yield of this reaction in the liquid hydrogen target is smaller than in the low-pressure gas target. The branching ratios of the ϕη\phi\eta channel were calculated on the basis of simultaneous analysis of the three data samples. The branching ratio for annihilation into ϕη\phi\eta from the 3S1^3S_1 protonium state turns out to be about ten times smaller as compared to the one from the 1P1^1P_1 state.Comment: 10 pages, 3 Postscript figures. Accepted by Physics Letters
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