Charged kaon femtoscopic correlations in pp collisions at $\sqrt{s}=7$ TeV

Correlations of two charged identical kaons (K$^{\rm ch}$K$^{\rm ch}$) are measured in pp collisions at $\sqrt{s}=7$ TeV by the ALICE experiment at the Large Hadron Collider (LHC). One-dimensional K$^{\rm ch}$K$^{\rm ch}$ correlation functions are constructed in three multiplicity and four transverse momentum ranges. The K$^{\rm ch}$K$^{\rm ch}$ femtoscopic source parameters $R$ and $\lambda$ are extracted. The K$^{\rm ch}$K$^{\rm ch}$ 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 K$_{\rm s}^{\rm 0}$K$_{\rm s}^{\rm 0}$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.

Figures

Figure 1

Purity and contaminations of selected kaons in pp collisions at $\sqrt{s}=7$ TeV.
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Figure 2

Correlation functions versus $q_{inv}$ for identical kaons from pp collisions at $\sqrt{s}=7$ TeV (solid circles)and those obtained with PERUGIA-2011 (open circles). Positive and negative kaon pairs are combined. The three columns represent the samples with different charged-particle multiplicities: $(1-11)$, $(12-22)$, $(>22)$, the four rows represent the four pair transverse momentum ranges:(0.2-0.35), (0.35-0.5), (0.5-0.7), (0.7-1.0) GeV/$c$. The lines going through the points represent the Gaussian fits discussed in the text
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Figure 3

$\lambda$-parameters of ${\rm K}^{\rm ch}{\rm K}^{\rm ch}$ versus $m_{\rm T}$ extracted by fitting correlation functions shown in Fig.[2] to Eq.[1] and the baseline to Eq.[2]. For comparison the ${\rm K}^0_{\rm s}{\rm K}^0_{\rm s}$ $\lambda$-parameters measured by ALICE in 7 TeV pp collisions are also shown. Statistical (darker lines) and total errors are shown. The points corresponding to the second and third multiplicity bins are offset by 0.03 GeV/$c^2$ for clarity.
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Figure 4

One-dimensional charged kaon radii versus $m_{\rm T}$extracted by fitting correlation functions shown in Fig.[2] to Eq.[1] and the baseline to Eq.[2]. For comparison the $\pi\pi$ and ${\rm K}^0_{\rm s}{\rm K}^0_{\rm s}$ radii measured by ALICE in 7 TeV pp collisions are also shown Statistical (darker lines) and total errors are shown. The points corresponding to the second and third multiplicity bins are offset by 0.03 GeV/$c$$^2$ for clarity.
[png]   [pdf]   [eps]