Near threshold eta meson production in the d d --> He-4 eta reaction.

Wrońska, A. ; Hejny, V. ; Wilkin, C. ; et al.
Eur.Phys.J.A 26 (2005) 421-428, 2005.
Inspire Record 695766 DOI 10.17182/hepdata.43489

The d+d->alpha+eta reaction has been investigated near threshold using the ANKE facility at COSY-Juelich. Both total and differential cross sections have been measured at two excess energies, Q=2.6 MeV and 7.7 MeV, with a subthreshold measurement being undertaken at Q=-2.6 MeV to study the physical background. While consistent with isotropy at the lower energy, the angular distribution reveals a pronounced anisotropy at the higher one, indicating the presence of higher partial waves. Options for the decomposition into partial amplitudes and their consequences for determination of the s-wave eta-alpha scattering length are discussed.

3 data tables

Measured cross sections. Systematic (DSYS) error does not include the luminosity uncertainty.

Experimental angular distribution at excess energy 2.6 MeV.

Experimental angular distribution at excess energy 7.7 MeV.


a0(980)+ resonance production in p p --> d K+ anti-K0 reactions close to threshold.

Kleber, V. ; Buescher, Markus ; Chernyshev, V. ; et al.
Phys.Rev.Lett. 91 (2003) 172304, 2003.
Inspire Record 617741 DOI 10.17182/hepdata.31682

The reaction pp->d K+ Kbar0 has been investigated at an excess energy of Q=46 MeV above the (K+ Kbar0) threshold with ANKE at COSY-Juelich. From the detected coincident dK+ pairs about 1000 events with a missing Kbar0 were identified, corresponding to a total cross section of sigma(pp->d K+ Kbar0)=(38 +/- 2(stat) +/- 14(syst)) nb. Invariant-mass and angular distributions have been jointly analyzed and reveal s-wave dominance between the two kaons, accompanied by a p-wave between the deuteron and the kaon system. This is interpreted in terms of a0+(980)-resonance production.

6 data tables

Total cross section for P P --> DEUT K+ KBAR0.

Centre of mass angular distribution of the deuteron with respect to the direction of the incoming proton.

Centre of mass angular distribution of the vector joining the K+ and KBAR0 with respect to the direction of the incoming proton.

More…

Comparison of Lambda and Sigma0 threshold production in proton proton collisions.

Sewerin, S. ; Schepers, G. ; Balewski, J.T. ; et al.
Phys.Rev.Lett. 83 (1999) 682-685, 1999.
Inspire Record 478929 DOI 10.17182/hepdata.42059

Threshold measurements of the associated strangeness production reactions pp --> p K(+) Lambda and pp --> p K(+) Sigma(0) are presented. Although slight differences in the shapes of the excitation functions are observed, the most remarkable feature of the data is that at the same excess energy the total cross section for the Sigma(0) production appears to be about a factor of 28 smaller than the one for the Lambda particle. It is concluded that strong Sigma(0)-p final state interactions, and in particular the Sigma-N --> Lambda-p conversion reaction, are the likely cause of the depletion for the yield in the Sigma signal. This hypothesis is in line with other experimental evidence in the literature.

1 data table

The given errors are statistical only. The cross section presented as a function of the nominal excess energy.


eta' production in proton proton scattering close to threshold.

Moskal, P. ; Balewski, J.T. ; Budzanowski, A. ; et al.
Phys.Rev.Lett. 80 (1998) 3202-3205, 1998.
Inspire Record 467809 DOI 10.17182/hepdata.42086

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.

1 data table

Only statistical errors are presented in the table.


Total cross section of the reaction p p --> p K+ Lambda close to threshold.

Balewski, J.T. ; Budzanowski, A. ; Dombrowski, H. ; et al.
Phys.Lett.B 420 (1998) 211-216, 1998.
Inspire Record 467810 DOI 10.17182/hepdata.42045

The energy dependence of the total cross section for the pp \to pK^+\Lambda reaction was measured in the threshold region covering the excess energy range up to 7MeV. Existing model calculations describe the slope of the measured cross sections well, but are too low by a factor of two to three in rate. The data were used for a precise determination of the beam momentum of the COSY-synchrotron.

1 data table

Only statistical errors are presented in the table.


Threshold measurements at the internal experimental facility COSY-11

Balewski, J. ; Brauksiepe, S. ; Budzanowski, A. ; et al.
Nucl.Phys.A 626 (1997) 85C-92C, 1997.
Inspire Record 463151 DOI 10.17182/hepdata.36361

The experimental setup and detection technique of the COSY-11 installation, an internal experimental facility at the cooler synchrotron and storage ring COSY Jülich, are described. The detection system has been designed for meson production studies with full geometrical acceptance close to threshold. Preliminary results of first measurements are presented, emphasis is put on strangeness production in the reactions pp → ppK + K − and pp → pK + Λ .

2 data tables

Excess energy of 6.1 MeV above threshold 3.3016 GeV.

Excess energy of 2 MeV above threshold 2.339 GeV.