Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userS-wave eta-proton FSI; phenomenological analysis of near-threshold production of pi0, eta, and eta mesons in proton-proton collisions
69
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We describe a novel technique for comparing total cross sections for the reactions pp --> pp pi(0), pp --> pp eta, and pp --> pp eta close to threshold. The initial and final state proton-proton interactions are factored out of the total cross section, and the dependence of this reduced cross section on the volume of phase space is discussed. Different models of the proton-proton interaction are compared. We argue that the scattering length of the S-wave eta-proton interaction is of the order of 0.1 fm.
rate research
Read More
We present the results of measurements of the analysing power for the p(pol)p --> pp eta reaction at the excess energies of Q=10 and 36 MeV, and interpret these results within the framework of the meson exchange models. The determined values of the analysing power at both excess energies are consistent with zero implying that the eta meson is produced predominantly in s-wave.
Taking advantage of the high acceptance and axial symmetry of the WASA-at-COSY detector, and the high degree of the polarized proton beam of COSY, the reaction pp{to} pp{eta} has been measured close to threshold to explore the analyzing power Ay. The angular distribution of Ay is determined with the precision improved by more than one order of magnitude with respect to previous results allowing a first accurate comparison with theoretical predictions. The determined analyzing power is consistent with zero for an excess energy of Q = 15 MeV signaling s wave production with no evidence for higher partial waves. At Q = 72 MeV the data reveals strong interference of P s and P p partial waves and cancellation of (P p) and Ss*Sd contributions. These results rule out the presently available theoretical predictions for the production mechanism of the {eta} meson.
The $pp to pp eta^{prime}$ (958) reaction has been measured at COSY using the internal beam and the COSY-11 facility. The total cross sections at the four different excess energies mbox{$ Q = ~1.5 ~MeV, ~1.7 ~MeV, ~2.9 ~MeV,$ and $ ~4.1 MeV$} have been evaluated to be mbox{$ sigma = 2.5 pm 0.5~nb$, $~~~ 2.9 pm 1.1~nb$, $~~~ 12.7 pm 3.2~nb$, ~ and $~~~ 25.2 pm 3.6 ~nb $}, respectively. In this region of excess energy the $eta^{prime}$ (958) cross sections are much lower compared to those of the $pi ^0$ and $eta$ production.
A comparison of the close-to-threshold total cross sections for the eta-prime meson production in both the pp --> pp eta-prime and pn --> pn eta-prime reactions should provide insight into the flavour-singlet (perhaps also into gluonium) content of the eta-prime meson and the relevance of quark-gluon or hadronic degrees of freedom in the creation process. The excitation function for the reaction pp --> pp eta-prime has been already established. At present, experimental investigations of the quasi-free pn --> pn X reactions are carried out at the COSY-11 facility using a beam of stochastically cooled protons and the deuteron cluster target. A method of measurement and preliminary results from the test experiments of the pn --> pn eta reaction are presented in this report.
Recent data on photoproduction of $eta$ mesons off protons have been included in the data base for the Bonn-Gatchina partial wave analysis. The real and imaginary parts of the $S$-wave $eta^prime pto eta^prime p$ scattering amplitude in the threshold region were fit to yield the $eta^prime p$ scattering length and the interaction range. This new analysis found $|a_{eta^prime p}|= (0.403pm 0.015pm 0.060)$ fm and a phase $phi=(87pm2)^circ$, while the range parameter is not well-constrained. The striking behavior of the GRAAL data on the beam asymmetry in the threshold region suggests that a narrow proton-$eta$ resonance might exist. However, the scattering length was found to be relatively insensitive to the possible existence of this narrow resonance.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
