Measurement of Direct-Photon Elliptic Flow in Pb-Pb Collisions at = 2.76 TeV

Workshop for Young Scientists on the Physics of Ultrarelativistic Nucleus–Nucleus Collisions 2012

Lohner, Daniel^1

Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany^1

关键词: Charged pions;    Direct photons;    Elliptic flows;    Inverse slope;    Pb-Pb collisions;    Production time;    System evolution;    Thermal photons;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/446/1/012028/pdf
DOI  :  10.1088/1742-6596/446/1/012028

来源: IOP

【 摘 要 】

We present the first measurement of the direct-photon elliptic flow vγ,dir2in Pb-Pb collisions at 2.76 TeV with data taken by the ALICE experiment at the LHC. The measurement provides evidence for a non-zero vγ,dir2for 1 Teffof the low pTdirect-photon spectrum observed at LHC and RHIC, recent hydrodynamical descriptions of the direct-photon production include a substantial portion of thermal photons from the hot plasma phase. As a consequence of the early production time, vγ,dir2is expected to be small compared to hadrons. A large vγ,dir2might lend support for a significant direct-photon emission from late stages of the system evolution where hadron flow has developed.