相关论文: Is there an eta-3He quasi--bound state ?
Coherent photoproduction of $\eta$-mesons off $^3$He, i.e. the reaction $\gamma ^3{He}\rightarrow \eta ^3{He}$, has been investigated in the near-threshold region. The experiment was performed at the Glasgow tagged photon facility of the…
A K-matrix formalism is used to relate the amplitudes for the three reactions pd --> 3He eta, pi- 3H --> 3He eta and pd --> 3H pi+. Free parameters are fitted to the available experimental data and an extrapolation below the eta 3He…
We present preliminary results from dp --> 3He X (X=pi0,eta) measurements near the eta production threshold. The data were taken during a slow ramping of the COSY internal deuteron beam scattered on a proton target. The 3He ejectiles were…
New, high-precision measurements of the 3He(e,e'p) reaction using the A1 collaboration spectrometers at the Mainz microtron MAMI are presented. These were performed in parallel kinematics at energy transfers below the quasi-elastic peak,…
We have measured excitation function for dp -> ppp_pi- reaction near the eta production threshold. We observe an enhancement of the counting rate above the threshold which can originate from the production of the eta meson in the reaction…
An exclusive measurement of the dd -> 3He n \pi 0 reaction was carried at a beam momentum of p = 1.2 GeV/c using the WASA-at-COSY facility. For the first time data on the total cross section as well as differential distributions were…
We have measured the reaction p + d -> 3He + eta at a proton beam energy of 980 MeV, which is 88.5 MeV above threshold using the new ``germanium wall'' detector system. A missing--mass resolution of the detector system of 2.6% was achieved.…
The differential cross sections of $pD\to ^3He X$ reactions, where $X=\eta, \ \eta'\ ,\omega, \ \phi $, are calculated on the basis of a two-step mechanism involving the subprocesses $pp\to d\pi ^+$ and $\pi^+n\to Xp $. It is shown that…
We have studied the reaction eta d -> eta d close to threshold within a nonrelativistic three-body formalism. We considered several eta N and NN models, in particular potentials with separable form, fitted to the low-energy eta N and NN…
The eta-prime meson production in the reaction pp-->pp eta-prime has been studied at excess energies of Q = 26.5, 32.5 and 46.6 MeV using the internal beam facility COSY-11 at the cooler synchrotron COSY. The total cross sections as well as…
Preliminary results of recent measurements of the near threshold eta meson production in the dp-->dp eta reaction are presented. The experiment was performed at the COSY-Juelich accelerator with the use of the COSY-11 detection system. Data…
The recent high statistics measurement of the pp -> pp eta reaction at an excess energy Q=15.5 MeV has been analysed by means of partial wave decomposition of the cross section. Guided by the dominance of the final state 1S0 pp interaction…
The total cross section of the pp -> pp eta' reaction has been measured at two energies near threshold by detecting the final protons in a magnetic spectrometer. The values obtained are about a factor of 70 less than for the corresponding…
We present a precise measurement of the cross section, proton and $\rm ^3He$ analyzing powers, and spin correlation coefficient $C_{y,y}$ for $p$-$\rm ^3He$ elastic scattering near 65 MeV, and a comparison with rigorous four-nucleon…
The cross section for the reaction $dd\rightarrow \,^4\!H\!e\,\eta$ close to threshold is estimated in a two-step model, similar to that which successfully describes near-threshold $pd\rightarrow \,^3\!H\!e\,\eta$ production. A $\pi$-meson,…
Using a recent parametrization of the fully antisymmetric three-nucleon wave function, based on the Paris and CD-Bonn potentials, we analyze the momentum distributions of constituents in 3He, as well as the spin-dependent observables for…
We have studied the quasielastic 3He(e,e'p)d reaction in perpendicular coplanar kinematics, with the energy and momentum transferred by the electron fixed at 840 MeV and 1502 MeV/c, respectively. The 3He(e,e'p)d cross section was measured…
It is shown that most of the available data on the $pp\to pp\eta$ reaction, including the invariant mass distributions in the $pp\to pp\eta$ reaction recently measured at COSY, can be understood in terms of the partial-wave amplitudes…
We present a measurement of the spin-dependent cross sections for the \vec{^3He}(\vec{e},e')X} reaction in the quasielastic and resonance regions at four-momentum transfer 0.1 < Q^2< 0.9 GeV^2. The spin-structure functions have been…
The contributions of three different types of driving terms are included in the estimation of the pd -> pd eta reaction at low energies. Near threshold, it is predicted that a two-step model involving an intermediate pion should be the most…