Low energy light-by-light scattering in heavy-ion UPC, a new possibility

Apr 9, 2019, 4:15 PM
26m
Palazzo Badini-Confalonieri - Sala Lauree

Palazzo Badini-Confalonieri - Sala Lauree

Via Verdi, 10 Turin
Parallel Session Talk WG4: Hadronic and Electroweak Observables WG4: Hadronic and Electroweak Observables

Speakers

Mariola Kłusek-Gawenda (IFJ PAS) Antoni Szczurek (Institute of Nuclear Physics) Rainer Schicker (Ruprecht Karls Universitaet Heidelberg (DE)) Mariola Ambroziak (u)Dr Mariola Klusek-Gawenda (Institute of Nuclear Physics Polish Academy of Sciences)

Description

So far light-by-light scattering ($\gamma\gamma\to\gamma\gamma$) was not accessible for experiments because the corresponding cross section is rather low. Measurements of diphotons in ultra-peripheral collisions (UPCs) of lead-lead have been reported recently by the ATLAS [1] and CMS Collaborations [2]. Our theoretical results based on equivalent photon approximation in the impact parameter space [3] are in good agreement with the current data [1,2].
We will discuss how to extend such studies to lower $\gamma\gamma$ energies where photoproduction of pseudoscalar and scalar resonances contribute to the two-photon final state. In addition, we consider the dominant background that arises from $\gamma\gamma$ fusion into pairs of neutral pions [4]. Such $\pi^0$-pairs contribute to the background when only two of the four decay photons are within the experimental acceptance, the other two photons escape undetected. We will discuss in detail how to reduce the unwanted background.
We will present differential distributions and total cross section in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{NN}}$=5.05 and 5.52TeV [5,6] and cross section for Ar-Ar collisions at the energy equal to 6.3TeV [7]. Results for ALICE and LHCb acceptance will be presented.
[1] ATLAS Collaboration, Nature Phys. 13 (2017) 852
[2] CMS Collaboration, arXiv:1810.04602
[3] M.Kłusek-Gawenda,P.Lebiedowicz,A.Szczurek, Phys.Rev.C93 (2016) 044907
[4] M.Kłusek-Gawenda,A.Szczurek, Phys.Rev.C87 (2013) 054908
[5] M.Kłusek-Gawenda,R.McNulty,R.Schicker,A.Szczurek, in preparation
[6] M.Kłusek-Gawenda, EPJ Web Conf. 199 (2019) 05004
[7] Z.Citron et al., arXiv:1812.06772

Primary authors

Mariola Kłusek-Gawenda (IFJ PAS) Antoni Szczurek (Institute of Nuclear Physics) Rainer Schicker (Ruprecht Karls Universitaet Heidelberg (DE))

Co-author

Ronan Mcnulty (University College Dublin (IE))

Presentation materials