Alleviating the present tension between T2K and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>NO</mml:mi> <mml:mi>ν</mml:mi> <mml:mi mathvariant="normal">A</mml:mi> </mml:math> with nonstandard neutrino interactio

Since neutrino oscillation was observed, several experiments have been built to measure its parameters. NuMI Off-axis <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msub> <a:mi>ν</a:mi> <a:mi>e</a:mi> </a:msub> </a:math> Appearance ( <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi>NO</c:mi> <c:mi>ν</c:mi> <c:mi mathvariant="normal">A</c:mi> </c:math> ) and Tokai-to-Kamioka (T2K) are two long-baseline experiments dedicated to measuring mainly the mixing angle <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"> <f:msub> <f:mi>θ</f:mi> <f:mn>23</f:mn> </f:msub> </f:math> , the charge-parity ( <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"> <h:mi>C</h:mi> <h:mi>P</h:mi> </h:math> ) conjugation phase <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"> <j:mrow> <j:msub> <j:mrow> <j:mi>δ</j:mi> </j:mrow> <j:mrow> <j:mi mathvariant="normal">CP</j:mi> </j:mrow> </j:msub> </j:mrow> </j:math> , and the mass ordering. However, there is a tension in current data. The T2K allowed region is in conflict with the region allowed by <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"> <m:mi>NO</m:mi> <m:mi>ν</m:mi> <m:mi mathvariant="normal">A</m:mi> </m:math> . We propose a nonstandard charged current interaction (CC-NSI) in neutrino production to relieve this tension. The CC-NSI is computed through quantum field theory formalism, where we derive perturbative analytical formulae considering CC-NSI in the pion decay. Within this new approach, we can alleviate <p:math xmlns:p="http://www.w3.org/1998/Math/MathML" display="inline"> <p:mi>NO</p:mi> <p:mi>ν</p:mi> <p:mi mathvariant="normal">A</p:mi> </p:math> and T2K tension for CC-NSI complex parameters of order <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"> <s:msup> <s:mn>10</s:mn> <s:mrow> <s:mo>−</s:mo> <s:mn>3</s:mn> </s:mrow> </s:msup> </s:math> . We show the new phase has a degeneracy to the Dirac <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline"> <u:mi>C</u:mi> <u:mi>P</u:mi> </u:math> phase of the form <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"> <w:mrow> <w:msub> <w:mrow> <w:mi>δ</w:mi> </w:mrow> <w:mrow> <w:mi mathvariant="normal">CP</w:mi> </w:mrow> </w:msub> <w:mo>±</w:mo> <w:mi>ϕ</w:mi> <w:mo>=</w:mo> <w:mn>1.5</w:mn> <w:mi>π</w:mi> </w:mrow> </w:math> , being a possible source of violation of charge-parity symmetry.