#
Femtoscopy with Identified Hadrons in pp, pPb, and PbPb Collisions in CMS^{ †}

^{†}

## Abstract

**:**

## 1. Introduction

## 2. Data Analysis

#### 2.1. Correlations

- particles from the actual event are paired with particles from some given number (in our case 25) of preceding events (“event mixing”); only events belonging to the same multiplicity (${N}_{\mathrm{rec}}$) class are mixed;
- particles from the actual event are paired, the laboratory momentum vector of the second particle is rotated around the beam axis by 90 degrees (“rotated”);
- particles from the actual event are paired, but the laboratory momentum vector of the second particle is negated (“mirrored”).

#### 2.2. Coulomb Interaction

#### 2.3. Clusters: Mini-Jets, Multi-Body Decays of Resonances

## 3. Results

#### Scaling

## 4. Conclusions

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**The distribution of $ln\epsilon $ as a function of total momentum p, for positively (

**Left**) and negatively (

**Right**) charged particles, in case of pPb collisions at $\sqrt{{s}_{{}_{\mathrm{NN}}}}=$ 5.02 TeV [8]. Here $\epsilon $ is the most probable energy loss rate at a reference path length ${l}_{0}=$ 450 $\mathsf{\mu}\mathrm{m}$. The z scale is shown in arbitrary units and is linear. The curves show the expected $ln\epsilon $ for electrons, pions, kaons, and protons (full theoretical calculation, Equation (30.11) in Ref. [12]).

**Figure 2.**Contribution of clusters (mini-jets and multi-body decays of resonances) to the measured Coulomb-corrected correlation function of ${\pi}^{+}{\pi}^{-}$ (open squares) for some selected ${k}_{\mathrm{T}}$ bins, 20 $\le {N}_{\mathrm{rec}}<$ 30, in case of pPb interactions at $\sqrt{{s}_{{}_{\mathrm{NN}}}}=$ 5.02 TeV [8]. The solid curves show the result of the Gaussian fit.

**Figure 3.**The like-sign correlation function of pions (red triangles) corrected for Coulomb interaction and cluster contribution (mini-jets and multi-body resonance decays) as a function of ${q}_{\mathrm{inv}}$ or the combined momentum, in some selected ${N}_{\mathrm{rec}}$ bins for all ${k}_{\mathrm{T}}$ [8]. Points with statistical uncertainty higher than 10% are plotted with light grey color. The solid curves indicate fits with the exponential Bose–Einstein parametrization.

**Figure 4.**The like-sign correlation function of kaons (red triangles) corrected for Coulomb interaction and cluster contribution (mini-jets and multi-body resonance decays) as a function of ${q}_{\mathrm{inv}}$, in some selected ${N}_{\mathrm{rec}}$ bins for all ${k}_{\mathrm{T}}$ [8]. Points with statistical uncertainty higher than 10% are plotted with light grey color. The solid curves indicate fits with the Bose–Einstein parametrization.

**Figure 5.**The ${N}_{\mathrm{tracks}}$ dependence of the one-dimensional pion radius (

**Top**) and the one-dimensional pion chaoticity parameter (

**Bottom**), shown here for several ${k}_{\mathrm{T}}$ bins, for all studied reactions [8]. Lines are drawn to guide the eye.

**Figure 6.**The ${N}_{\mathrm{tracks}}$ dependence of the two-dimensional pion radii (${R}_{l}$—open symbols, ${R}_{t}$—closed symbols), shown here for several ${k}_{\mathrm{T}}$ bins, for all studied reactions [8]. Lines are drawn to guide the eye.

**Figure 7.**(

**Left**) Radius parameters as a function of ${N}_{\mathrm{tracks}}$ scaled to ${k}_{\mathrm{T}}=$ 0.45 GeV/c with the help of the parametrization ${R}_{\mathrm{param}}$ (Equation 5). (

**Right**) ratio of the radius parameter and the value of the parametrization ${R}_{\mathrm{param}}$ (Equation 5) at ${k}_{\mathrm{T}}=$ 0.45 GeV/c as a function of ${k}_{\mathrm{T}}$ (points were shifted left and right with respect to the center of the ${k}_{\mathrm{T}}$ bin for better visibility). Upper row: R from the one-dimensional (${q}_{\mathrm{inv}}$) analysis. Middle row: ${R}_{l}$ from the two-dimensional $({q}_{\mathrm{l}},{q}_{\mathrm{t}})$ analysis. Bottom row: ${R}_{t}$ from the two-dimensional $({q}_{\mathrm{l}},{q}_{\mathrm{t}})$ analysis. Fit results are indicated in the figures [8]; for details, see text.

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**MDPI and ACS Style**

Siklér, F.
Femtoscopy with Identified Hadrons in pp, pPb, and PbPb Collisions in CMS. *Universe* **2017**, *3*, 76.
https://doi.org/10.3390/universe3040076

**AMA Style**

Siklér F.
Femtoscopy with Identified Hadrons in pp, pPb, and PbPb Collisions in CMS. *Universe*. 2017; 3(4):76.
https://doi.org/10.3390/universe3040076

**Chicago/Turabian Style**

Siklér, Ferenc.
2017. "Femtoscopy with Identified Hadrons in pp, pPb, and PbPb Collisions in CMS" *Universe* 3, no. 4: 76.
https://doi.org/10.3390/universe3040076