Taking advantage of both the high mass resolution of the COSY-11 detector and the high energy resolution of the low-emittance proton beam of the cooler synchrotron COSY, we determine the excitation ...function for the pp→ppη(') reaction close to threshold. Combining these data with previous results, we extract the scattering length for the η(')-proton potential in free space to be Re(a(pη(')))=0±0.43 fm and Im(a(pη(')))=0.37(-0.16)(+0.40) fm.
Taking advantage of both the low-emittance proton beam of the cooler synchrotron COSY and the high momentum precision of the COSY-11 detector system, the mass distribution of the η' meson was ...measured with a resolution of 0.33 MeV/c2 (FWHM), improving the experimental mass resolution by almost an order of magnitude with respect to previous results. Based on the sample of more than 2300 reconstructed pp → ppη' events, the total width of the η' meson was determined to be Γ(η') = 0.226 ± 0.017(stat) ± 0.014(syst) MeV/c2.
The proton–proton and proton–
η
′
invariant mass distributions have been determined for the
pp
→
pp
η
′
reaction at an excess energy of
Q
=
16.4
MeV
. The measurement was carried out using the ...COSY-11 detector setup and the proton beam of the cooler synchrotron COSY. The shapes of the determined invariant mass distributions are similar to those of the
pp
→
pp
η
reaction and reveal an enhancement for large relative proton–proton momenta. This result, together with the fact that the proton–
η interaction is much stronger that the proton–
η
′
interaction, excludes the hypothesis that the observed enhancement is caused by the interaction between the proton and the meson.
Taking advantage of both the high mass resolution of the COSY-11 detector and the high energy resolution of the low-emittance proton beam of the cooler synchrotron COSY, we determine the excitation ...function for the pp arrow right ppeta' reaction close to threshold. Combining these data with previous results, we extract the scattering length for the eta'-proton potential in free space to be Re(apeta') =0+ or -0.43 fm and Im(apeta')=0.37-0.16+0.40 fm.
Taking advantage of both the low-emittance proton beam of the cooler synchrotron COSY and the high momentum precision of the COSY-11 detector system, the mass distribution of the {eta}{sup '} meson ...was measured with a resolution of 0.33 MeV/c{sup 2} (FWHM), improving the experimental mass resolution by almost an order of magnitude with respect to previous results. Based on the sample of more than 2300 reconstructed pp{yields}pp{eta}{sup '} events, the total width of the {eta}{sup '} meson was determined to be {Gamma}{sub {eta}}{sup '}=0.226{+-}0.017(stat){+-}0.014(syst) MeV/c{sup 2}.
The reaction pp arrow right pp pi super(0) pi super(0) has been investigated at a beam energy of 1.4 GeV using the WASA-at-COSY facility. The total cross section is found to be (324+/-systematic ...sub(21)+/-normalization sub(58)) mu b. In order to study the production mechanism, differential kinematic distributions have been evaluated. The differential distributions indicate that both initial state protons are excited into intermediate Delta (1232) resonances, each decaying into a proton and a single pion, thereby producing the pion pair in the final state. No significant contribution of the Roper resonance N super( square )(1440) via its decay into a proton and two pions is found.
An exclusive measurement of the decay eta arrow right pi super(+) pi super(-) gamma has been performed at the WASA facility at COSY. The eta mesons were produced in the fusion reaction inline image X ...at a proton beam momentum of 1.7 GeV/c. Efficiency corrected differential distributions have been extracted based on inline image events after background subtraction. The measured pion angular distribution is consistent with a relative p-wave of the two-pion system, whereas the measured photon energy spectrum was found at variance with the simplest gauge invariant matrix element of eta arrow right pi super(+) pi super(-) gamma . A parameterization of the data can be achieved by the additional inclusion of the empirical pion vector form factor multiplied by a first-order polynomial in the squared invariant mass of the pi super(+) pi super(-) system.
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![Determination of the [eta]'...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0031-9007/small "Determination of the [eta]'-Proton Scattering Length in Free Space")