p_lab plots for pi+ from C+C at 1 and 2A GeV are compared to pi+ from KAOS.
TAPS data points are from Ch. Sturm (published in his thesis, page 81, Fig.4.7), and show d(sigma)/dp_lab at 44+-4 and 54+-4 deg for 1A GeV,
and at 32+-4 deg. and 40+-4deg. for 2A GeV (region close to midrapidity).
The HADES points are re-calculated from multiplicity to cross section assuming total cross section 950 mb,
and corrected to minimum bias by a ratio of number of participants 6./8.61 and 6./8.38 for 1 and 2 GeV, respectively.
2 figures show the comparison for 1 and 2 GeV
The same figures in the linear scale are also attached. For 1 GeV data we have almost perfect agreement, for 2 GeV our data are systematically lower than the KAOS points at low momenta region, just outside the error bars (about 10% difference).
There can be problem with upper range in momenta of our data. When pi/p ratio is low, we do not separate protons and pi+ already at momenta below 1000 MeV/c. For 1 GeV I already cut points with p_lab above 775 and 875 Me/c for 44 and 54 degrees, respectively. For 2 GeV, it probably
should be done for p_lab > 900 MeV/c for the 40 deg. data.
Comparison of the cross sections within KAOS acceptance (p_lab > 175 MeV/c):
HADES KAOS p_lab>175MeV/c
1GeV 44 deg 46+-3+-3 46+-2
54 29+-1.5+-2 29+-2
2GeV 32 deg 173+-9+-12 185+-5
40 120+-6+-9 129+-4
Errors of our data: 1st error is a 5% error of the efficiency correction, the 2nd is a 7% error of the correction to min. bias.
- 02 Dec 2008
- c1c liny:
- c2c liny: