Speaker
Description
Neutral mesons such as $\pi^{0}$ and $\eta$ that decay into two photons are suitable to study parton energy loss in the QGP, since they can be identified, using a fine-segmented electromagnetic calorimeter, in a wide transverse momentum range.
The Photon Spectrometer (PHOS) in ALICE is an electromagnetic calorimeter which is located at 4.6 m from the interaction point.
PHOS consists of 12,544 segments with a $2.2 \times 2.2\times 18 \ {\rm cm}^{3}$ $\rm PbWO_{4}$ crystal readout by an APD.
This fine granularity, possible due to the small Moliere radius of 2.2 cm, allows us to distinguish two photons decaying with a small opening angle from a parent particle up to $p_{\rm T}$ = 50 ${\rm GeV}/c$ with an invariant mass method.
ALICE recorded about 20 $\mu b^{-1} $ of Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV and 2.5 $n b^{-1} $ of pp collisions at $\sqrt{s}$ = 5.02 TeV with minimum bias triggers in 2015.
Additionally, PHOS Level-0 trigger which is based on high energy hits in 4 $\times$ 4 crystals can extend the $\pi^{0}$ measurement up to $p_{\rm T}$ = 30 ${\rm GeV}/c$ in pp collisions.
Clear $\pi^{0}$ and $\eta$ meson peaks have been extracted in a wide $p_{\rm T}$ range and in each centrality class via di-photon decay channel with the PHOS detector in ALICE.
| Preferred Track | Jets and High pT Hadrons |
|---|---|
| Collaboration | ALICE |
