Probing CP Violation with Neutrino Disappearance Alone

The best way to probe <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>C</a:mi><a:mi>P</a:mi></a:math> violation in the lepton sector is with long-baseline accelerator neutrino experiments in the appearance mode: the appearance of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:msub><c:mrow><c:mi>ν</c:mi></c:mrow><c:mrow><c:mi>e</c:mi></c:mrow></c:msub></c:mrow></c:math> in predominantly <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:msub><e:mi>ν</e:mi><e:mi>μ</e:mi></e:msub></e:math> beams. Here we show that it is possible to discover <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi>C</g:mi><g:mi>P</g:mi></g:math> violation with disappearance experiments only, by combining JUNO for electron neutrinos and DUNE or Hyper-Kamiokande for muon neutrinos. While the maximum sensitivity to discover <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mi>C</i:mi><i:mi>P</i:mi></i:math> is quite modest (<k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mn>1.6</k:mn><k:mi>σ</k:mi></k:math> with 6 years of JUNO and 13 years of DUNE), some values of <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>δ</m:mi></m:math> may be disfavored by <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mo>></o:mo><o:mn>3</o:mn><o:mi>σ</o:mi></o:math> depending on the true value of <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mrow><q:mi>δ</q:mi></q:mrow></q:math>. Published by the American Physical Society 2024