Speaker
Patrick Simon Reichelt
(Johann-Wolfgang-Goethe Univ. (DE))
Description
The measurement of electron-positron pairs (dielectrons) in the low invariant mass region allows to study the vacuum and in-medium properties of light vector mesons. Additionally, low-mass dielectrons are produced by internal conversion of virtual direct photons that are emitted during the evolution of ultra-relativistic heavy-ion collisions. They are excellent direct probes to study all collision stages, since they pass through the hot and dense medium almost unscathed.
In particular, the extraction of virtual photons in the low-mass region provides a complementary measurement of the real photon yield, which gives access to the temperature of the created matter and can be compared to results from other approaches and existing theoretical calculations.
In the ALICE apparatus at the LHC, electrons at mid-rapidity are identified by their specific energy loss in the Inner Tracking System (ITS) and the Time Projection Chamber (TPC), combined with time-of-flight information from the TOF detector.
We will present the electron identification performance of these detector systems and the measurement of the low-mass dielectron continuum in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV.
The invariant mass distribution of dielectrons, in slices of pair transverse momentum, will be compared to that of a cocktail of the expected hadronic contributions, with the aim of extracting the virtual direct photon yield.
| On behalf of collaboration: | ALICE |
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Author
Patrick Simon Reichelt
(Johann-Wolfgang-Goethe Univ. (DE))
