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Si - spectrometer acceptance matching

After the Si multiplicity is obtained, it needs to be compared with the spectrometer $dN/d\eta$. One needs to take into account that Si acceptance is broader and extends further from midrapidity than spectrometer's; therefore $dN/d\eta$ is measured over different ranges of $\eta$. I had to involve RQMD simulation to be able to compare $dN/d\eta$ from the Si and the spectrometer. In principle one can get the same answer from the measurement of non-identified $dN/dy$ distribution for + and $-$ (like NA49's $h^{-}$ [41]).

Therefore I require that the absolute $\,dN/\,d\eta$ in Si and spectrometer match with factors which I derive from RQMD distribution, see Table 4.3. The spectrometer acceptance was cut down to a fiducial range, free of the edge effects (monitored by the acceptance-corrected $\,dN/\,d\eta$ histograms with high resolution in $\eta$).

Table 4.3: RQMD-generated factors for acceptance matching. The following acceptance intervals were used. For the Si: ${\eta }_{min}=1.5$, ${\eta }_{max}=3.3$. For the spectrometer: in the low angle setting, ${\eta }_{min}=3.6$, ${\eta }_{max}=4.4$. In the high angle setting, ${\eta }_{min}=2.6$, ${\eta }_{max}=3.1$.

$\frac{spectrometer}{Si (+ and -)/2}$	Spectrometer sign
	$+$	$-$
high angle	1.208	0.986
low angle	1.025	0.871

These factors are the ratios of $dN/d\eta$ from the simulation alone. The simulation needs to know only the gross shape of $dN/d\eta$ for both signs, which RQMD does know. (Its $dN/dy$ distribution for pions has $\sigma=1.4$ in agreement with NA49 $h^{-}$ [41]. ) The words ``simulation alone'' mean that delta electrons which I do not simulate, as well as imperfections of Si alignment, which I do not know, do not affect the simulated factors. Massive particles have asymmetrical $dN/d\eta$ distribution and our high angle spectrometer settings cover them more efficiently than Si. As a result, the simulated factors are different for $+$ and $-$ because of the asymmetry between protons/antiprotons and $K^{+}/K^{-}$.