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Cross Section and Tensor Analysing Power of the $\vec{d}d\to \eta\alpha$ Reaction Near Threshold

The GEM collaboration Budzanowski, A. ; Chatterjee, A. ; Gebel, R. ; et al.
Nucl.Phys.A 821 (2009) 193-209, 2009.
Inspire Record 803178 DOI 10.17182/hepdata.52401

The angular distributions of the unpolarised differential cross section and tensor analysing power $A_{xx}$ of the $\vec{d}d\to\alpha \eta$ reaction have been measured at an excess energy of 16.6 MeV. The ambiguities in the partial-wave description of these data are made explicit by using the invariant amplitude decomposition. This allows the magnitude of the s-wave amplitude to be extracted and compared with results published at lower energies. In this way, firmer bounds could be obtained on the scattering length of the $\eta \alpha$ system. The results do not, however, unambiguously prove the existence of a quasi-bound $\eta \alpha$ state.

3 data tables
Table 1

Total cross section from fit to the differential angular distribution.

Table 2

Differential angular distribution.

Table 3

Analysing power measurements.


Differential cross sections measurement for the p p --> d pi+ reaction at 850-MeV/c.

The GEM collaboration Betigeri, M. ; Bojowald, J. ; Budzanowski, A. ; et al.
Phys.Rev.C 63 (2001) 044011, 2001.
Inspire Record 551879 DOI 10.17182/hepdata.54884

The present data support a large anisotropy in accordance with phase shift predictions and in contrast to another recent experiment.

4 data tables
Table 1

Measured deuteron angular distribution in the c.m. system. The errors shown are statistical only and there is an additional 10 PCT systematic uncertainty on the overall normalisation.

Table 2

Legendre polynomial coefficients from a second order and fourth order fit.

Table 3

Total cross section from second order fit.

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