$\Sigma^0$ and $\overline{\Sigma}^0$ Baryon Production in pp Collisions at $\sqrt{s}$ = 7 TeV with ALICE at the LHC

20 May 2014, 16:30
spectrum (darmstadtium)



Board: J-02
Poster Thermodynamics and Hadron Chemistry Poster session


Alexander Borissov (Pusan National University (KR))


Hyperon production in heavy-ion collisions is a very precious probe to study the properties of the hot dense matter, as it is sensitive to strangeness enhancement, chiral symmetry restoration and parton energy loss. Moreover, it allows to further constrain the chemical freeze-out parameters based on statistical models. The measurement of the full set of hyperons allows to discriminate prompt and decay hyperons, e.g. prompt $\Lambda$ and one from $\Sigma^0$ decay. The ALICE detector provides a unique capability to study the electromagnetic decay of $\Sigma^0$($\overline{\Sigma}^0$) baryon due to the possibility to measure the low energy photons. The status of the first observation of $\Sigma^0$ and $\overline{\Sigma}^0$(1192 MeV) baryon in pp collisions at $\sqrt{s} = 7$ TeV by ALICE at the LHC is presented. The $\Sigma^0 \to \Lambda + \gamma$ ($\overline{\Sigma}^0 \to \overline{\Lambda} + \gamma$) signal (branching is 100%) is reconstructed through an invariant mass analysis: the decay $\Lambda \to {\rm p} + \pi^-$ ($\overline{\Lambda} \to \overline{\rm p} + \pi^+$) is detected in the central tracking system of ALICE, while the photon is reconstructed via its conversion. The peak position is in agreement with the PDG data and its width is consistent with the results of Monte Carlo simulation. The $\Sigma^0$ ($\overline{\Sigma}^0$) baryon is measured in the transverse momentum range between 1 and 10 GeV/$c$. In addition, an invariant mass peak is reconstructed with the photon detected in the ALICE PHOS calorimeter.
On behalf of collaboration: ALICE

Primary author

Alexander Borissov (Pusan National University (KR))

Presentation Materials