Production of e+ e- pairs accompanied by nuclear dissociation in ultra-peripheral heavy ion collision

The collaboration
Phys.Rev.C 70 (2004) 031902, 2004.

Abstract (data abstract)
We present the first data on $e^{+}e^{−}$ pair production accompanied by nuclear breakup in ultra-peripheral gold-gold collisions at a center of mass energy of 200 GeV per nucleon pair. The nuclear breakup requirement selects events at small impact parameters, where higher-order corrections to the pair production cross section should be enhanced. We compare the pair kinematic distributions with two calculations: one based on the equivalent photon approximation, and the other using lowest-order quantum electrodynamics (QED); the latter includes the photon virtuality. The cross section, pair mass, rapidity and angular distributions are in good agreement with both calculations. The pair transverse momentum, $p_{T}$, spectrum agrees with the QED calculation, but not with the equivalent photon approach. We set limits on higher-order contributions to the cross section. The $e^{+}$ and $e^{−}$ $p_{T}$ spectra are similar, with no evidence for interference effects due to higher-order diagrams.

• #### Figure 2 a

Data from Figure 2 a

10.17182/hepdata.98580.v1/t1

(a) The pair mass distribution, (b) pair $p){T}$ , (c) pair rapidity and (d) pair cos($\theta′$) distributions. The data (points)...

• #### Figure 2 b

Data from Figure 2 b

10.17182/hepdata.98580.v1/t2

(a) The pair mass distribution, (b) pair $p){T}$ , (c) pair rapidity and (d) pair cos($\theta′$) distributions. The data (points)...

• #### Figure 2 c

Data from Figure 2 c

10.17182/hepdata.98580.v1/t3

(a) The pair mass distribution, (b) pair $p){T}$ , (c) pair rapidity and (d) pair cos($\theta′$) distributions. The data (points)...

• #### Figure 2 d

Data from Figure 2 d

10.17182/hepdata.98580.v1/t4

(a) The pair mass distribution, (b) pair $p){T}$ , (c) pair rapidity and (d) pair cos($\theta′$) distributions. The data (points)...

• #### Figure 3

Data from Figure 3

10.17182/hepdata.98580.v1/t5

The $p_{T}$ spectra of the produced electrons and positrons, along with the comparable EPA and QED calculations. In both calculations,...