Abstract
This Letter presents the observation and measurement of electroweak production of a same-sign π boson pair in association with two jets using 36.1ββfbβ1 of proton-proton collision data recorded at a center-of-mass energy of βπ =13ββTeV by the ATLAS detector at the Large Hadron Collider. The analysis is performed in the detector fiducial phase-space region, defined by the presence of two same-sign leptons, electron or muon, and at least two jets with a large invariant mass and rapidity difference. A total of 122 candidate events are observed for a background expectation of 69 Β±7 events, corresponding to an observed signal significance of 6.5 standard deviations. The measured fiducial signal cross section is πfid=2.89+0.51β0.48β’(stat)+0.29β0.28β’(syst)ββfb.