A study of the decay
pan id="mmlsi1" class="mathmlsrc">pan class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0370269316301022&_mathId=si1.gif&_user=111111111&_pii=S0370269316301022&_rdoc=1&_issn=03702693&md5=a27d90cd9ed1c8a9305ee68cb10567d6" title="Click to view the MathML source">D0→K−π+μ+μ−pan>pan class="mathContainer hidden">pan class="mathCode">pan>pan>pan> is performed using data collected by the LHCb detector in proton–proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of
pan id="mmlsi2" class="mathmlsrc">pan class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0370269316301022&_mathId=si2.gif&_user=111111111&_pii=S0370269316301022&_rdoc=1&_issn=03702693&md5=aa553350039047030cfe0c9c588b103c" title="Click to view the MathML source">2.0 fb−1pan>pan class="mathContainer hidden">pan class="mathCode">pan>pan>pan>. Decay candidates with muon pairs that have an invariant mass in the range
pan id="mmlsi102" class="mathmlsrc">pan class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0370269316301022&_mathId=si102.gif&_user=111111111&_pii=S0370269316301022&_rdoc=1&_issn=03702693&md5=9ca79b3c364a17f07386b953b9201081" title="Click to view the MathML source">675–875 MeV/c2pan>pan class="mathContainer hidden">pan class="mathCode">pan>pan>pan> are considered. This region is dominated by the
pan id="mmlsi11" class="mathmlsrc">pan class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0370269316301022&_mathId=si11.gif&_user=111111111&_pii=S0370269316301022&_rdoc=1&_issn=03702693&md5=ed6c8ea4c95c2a6afc807fff99e1cc17" title="Click to view the MathML source">ρ0pan>pan class="mathContainer hidden">pan class="mathCode">pan>pan>pan> and
ω resonances. The branching fraction in this range is measured to be
This is the first observation of the decay
pan id="mmlsi1" class="mathmlsrc">pan class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0370269316301022&_mathId=si1.gif&_user=111111111&_pii=S0370269316301022&_rdoc=1&_issn=03702693&md5=a27d90cd9ed1c8a9305ee68cb10567d6" title="Click to view the MathML source">D0→K−π+μ+μ−pan>pan class="mathContainer hidden">pan class="mathCode">pan>pan>pan>. Its branching fraction is consistent with the value expected in the Standard Model.