Summary

The results of the inclusive production cross section of $V_0$ strange particle measurements using the HERA-B detector were presented. The $V_0$ cross sections were determined using the information from the tracking stations of VDS and Main tracker for three types of target material, carbon , titanium and tungsten, in the squared transverse momentum range of $0. \,<\, p_t^2\, <\,1.5\,\, ($GeV/c$)^2$ and in the Feynman scaling variable ($x_F$) range $-0.12 \,<\,x_F \, <\,0.$.

The cross section analysis consist of the following main steps:

• A detailed quality check was performed for the ITR data for all runs considered in the analysis.

• The geometrical acceptance and reconstruction efficiency were estimated by using Monte Carlo simulation. The overall efficiency to reconstruct the $V_0$ was found to be about 10% for $K^0_S$ and 5% for $\Lambda (\bar \Lambda)$.

• The backgrounds to the $V_0$ mass peaks were subtracted by a polynomial fit of the background spectrum.

Various sources of systematic uncertainties, such as luminosity determination, $V_0$ background subtraction and MC description of data especially $p_t^2$ and $x_F$ kinematical variables were estimated.

The $V_0$ cross sections per nucleon were fitted for the three target materials using a functional dependence $\sigma \varpropto A^{\alpha}$. The exponent $\alpha$ was measured to be 0.932 $\pm$ 0.081. The value for the $K^0_S$ inclusive production cross section provided by the Annecy(LAPP) [#!drijard!#] experiment for $\sqrt{s}=52.5$ GeV is in agreement with the measurements presented in this work. The cross section for $\Lambda$ is in agreement with the numbers provided by ISR at $\sqrt{s}=53$ GeV and $\sqrt{s}=62$ GeV [#!erhan!#]. Comparisons of the $V_0$ inclusive production cross section and the ratio of production cross sections $\sigma (\bar \Lambda) / \sigma (\Lambda)$ determined at mid-rapidity, with other experiments is shown in Fig.6.22 and in Fig.6.23

Figure 6.22: Production cross section of $V_0$ as a function of $s$ (the square of center of mass energy). Measurements obtained with the 2000 and 2002 Minimum bias data are shown with black symbols, open symbols represent measurements done by another experiments.

Figure: Ratio of production cross sections $\sigma (\bar \Lambda) / \sigma (\Lambda)$ determined at mid-rapidity as a function of $\sqrt {s}$. Measurements obtained with the 2002 Minimum bias data are shown with black symbol, open symbols represent measurements done by another experiments.

The presented analysis illustrates a good understanding of the HERA-B detector performance during data taking 2002/2003. It also demonstrates that results of HERA-B can significantly contribute to the $V_0$ inclusive cross section measurements and help to better understand the strange particle production mechanism.