Narrow Results

In this paper, we have studied the spectra of strange particles in pp collision at $\sqrt{s}$ = 0.9 TeV by using different simulation models, EPOS-1.99, SIBYLL-2.3c, QGSJETII-04 and EPOS-LHC. The transverse momentum and rapidity distribution in the $p_T$ range of $0<p_T<10$ GeV/c and $0<p_T<2$ GeV/c, respectively, are investigated for the strange particles, $K_s^o$, $\mathrm{\Lambda }$, ${\mathrm{\Xi }}^{-}$. Similarly, a comparative study is done for the ratio of $\mathrm{\Lambda }/K_s^o$ and ${\mathrm{\Xi }}^{-}/\mathrm{\Lambda }$ as a function of transverse momentum and rapidity. The validity of simulation models is tested by comparing simulation results to the CMS experimental data at $\sqrt{s}$ = 0.9 TeV. For $p_T$ distributions, the EPOS-LHC model in the $p_T$ range $p_T<0.3$ GeV/c, $p_T>8$ GeV/c and in $3.6<p_T<3.8$ GeV/c while EPOS-1.99 model in the $p_T$ range $2.5<p_T<2.8$ GeV/c and QGSJETII-04 model in the $p_T$ range $2.5<p_T<2.8$ GeV/c as well as, $3.6<p_T<3.8$ GeV/c explain the experimental data well. For the, $\mathrm{\Lambda }/K_s^o$ and ${\mathrm{\Xi }}^{-}/\mathrm{\Lambda }$ versus transverse momentum distributions, EPOS-LHC model in the $p_T$ range of, $2.4<p_T<2.6$ GeV/c and $1.6<p_T<1.8$ GeV/c, EPOS-1.99 model in the $p_T$ range, $1.7<p_T<2.2$ GeV/c, SIBYLL-2.3c model in the $p_T$ range, $1.4<p_T<1.6$ GeV/c and QGSJETII-04 model in the $p_T$ range $0.4<p_T<0.6$ GeV/c explain the experimental data very well. Similarly, for $\mathrm{\Lambda }/K_s^o$ and ${\mathrm{\Xi }}^{-}/\mathrm{\Lambda }$ versus rapidity distribution QGSJETII-04 predictions in the rapidity region, $0.4<\left|y\right|<0.6$, $1.4<\left|y\right|<1.6$, and $\left|y\right|>1.8$, while EPOS-LHC model in the region, $\left|y\right|>1.8$, very well explained the experimental data. Although good comparison of the models predictions with the experimental data is observed, none of them completely describe the experimental data the spectra of strange particles over the entire $p_T$ and $y$ range.

The particle ratios $k^{+}/{\pi }^{+}$, ${\pi }^{-}/K^{-}$, $\bar{p}/{\pi }^{-}$, $\mathrm{\Lambda }/{\pi }^{-}$, $\mathrm{\Omega }/{\pi }^{-}$, $p/{\pi }^{+}$, ${\pi }^{-}/{\pi }^{+}$, $K^{-}/K^{+}$, $\bar{p}/p$, $\bar{\mathrm{\Lambda }}/\mathrm{\Lambda }$, $\bar{\mathrm{\Sigma }}/\mathrm{\Sigma }$, $\bar{\mathrm{\Omega }}/\mathrm{\Omega }$ measured at AGS, SPS and RHIC energies are compared with large statistical ensembles of 100,000 events deduced from the CRMC EPOS $1.99$ and the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) hybrid model. In the UrQMD hybrid model two types of phase transitions are taken into account. All these data are then confronted with the ideal Hadron Resonance Gas Model. The two types of phase transitions are apparently indistinguishable. Apart from $k^{+}/{\pi }^{+}$, $k^{-}/{\pi }^{-}$, $\mathrm{\Omega }/{\pi }^{-}$, $\bar{p}/{\pi }^{+}$ and $\bar{\mathrm{\Omega }}/\mathrm{\Omega }$, the UrQMD hybrid model agrees well with the CRMC EPOS $1.99$. We also conclude that the CRMC EPOS $1.99$ seems to largely underestimate $k^{+}/{\pi }^{+}$, $k^{-}/{\pi }^{-}$, $\mathrm{\Omega }/{\pi }^{-}$ and $\bar{p}/{\pi }^{+}$.