München 2019 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 48: Heavy-Ion Collisions and QCD Phases IX
HK 48.3: Talk
Thursday, March 21, 2019, 14:45–15:00, HS 15
Very soft dielectron production in pp collisions at √s=13 TeV with ALICE — •Jerome Jung — Institut für Kernphysik, Goethe-Universität Frankfurt
Low-mass dielectrons present an exceptional tool to deepen our understanding of the Quark-Gluon Plasma (QGP) created in the collision of ultra-relativistic heavy-ions, since they are produced at all stages of the collision while being unaffected by the strong interaction. To single out the interesting signal characteristics of the QGP, the primordial e+e− pair production in vacuum has to be understood first.
At the Intersecting Storage Rings (ISR) at CERN, an excess of dielectron pairs over the expectation from know dielectron sources had been measured at low invariant mass and small pair pT,ee in pp collisions at √s = 63 GeV. In ALICE the reconstruction efficiency of low-pT electrons can be increased by reducing the magnetic field of the central barrel solenoid. This allows a better electron background rejection and simultaneously gives the opportunity to access a similar phase space as the ISR experiments.
In this talk, results of the dielectron measurement in pp collisions at √s = 13 TeV taken with reduced magnetic field will be presented including the analysis of new data from 2018. They are compared to the published nominal-field data, to illustrate the benefits of the low-field setting and to the expected yield from known hadronic sources to address the question of a possible excess at LHC energies.
Supported by BMBF and the Helmholtz Association.