Correlations of two charged identical kaons (Kch Kch) are measured in pp collisions at sqrt{s}=7 TeV by the ALICE experiment at the Large Hadron Collider (LHC). One-dimensional Kch Kch correlation ...functions are constructed in three multiplicity and four transverse momentum ranges. The Kch Kch femtoscopic source parameters R and lambda are extracted. The Kch Kch correlations show a slight increase of femtoscopic radii with increasing multiplicity and a slight decrease of radii with increasing transverse momentum. These trends are similar to the ones observed for pi pi and Ks0 Ks0 correlations in pp and heavy-ion collisions. However, the observed one dimensional correlation radii for charged kaons are larger at high multiplicities than those for pions in contrast to what was observed in heavy-ion collisions at RHIC.
We report on the high statistics two-pion correlation functions from pp collisions at sqrt{s}=0.9 TeV and sqrt{s}=7 TeV, measured by the ALICE experiment at the Large Hadron Collider. The correlation ...functions as well as the extracted source radii scale with event multiplicity and pair momentum. When analyzed in the same multiplicity and pair transverse momentum range, the correlation is similar at the two collision energies. A three-dimensional femtoscopic analysis shows an increase of the emission zone with increasing event multiplicity as well as decreasing homogeneity lengths with increasing transverse momentum. The latter trend gets more pronounced as multiplicity increases. This suggests the development of space-momentum correlations, at least for collisions producing a high multiplicity of particles. We consider these trends in the context of previous femtoscopic studies in high-energy hadron and heavy-ion collisions, and discuss possible underlying physics mechanisms. Detailed analysis of the correlation reveals an exponential shape in the outward and longitudinal directions, while the sideward remains a Gaussian. This is interpreted as a result of a significant contribution of strongly decaying resonances to the emission region shape. Significant non-femtoscopic correlations are observed, and are argued to be the consequence of "mini-jet"-like structures extending to low p_T. They are well reproduced by the Monte-Carlo generators and seen also in pi^+ pi^- correlations.
Underlying event was originally defined by the CDF collaboration decades ago. Here we improve the original definition to extend our analysis for events with multiple-jets. We introduce a definition ...for surrounding rings/belts and based on this definition the jet- and surrounding-belt-excluded areas will provide a good underlying event definition. We inverstigate our definition via the multiplicity in the defined geometry. In parallel, mean transverse momenta of these areas also studied in proton-proton collisions at \(\sqrt{s}=7\) TeV LHC energy.
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