Constraining neutrinophilic mediators at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>FASER</mml:mi><mml:mi>ν</mml:mi></mml:mrow></mml:math>, FLArE, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/M

High energy collider neutrinos have been observed for the first time by the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>FASER</a:mi><a:mi>ν</a:mi></a:math> experiment. The detected spectrum of collider neutrinos scattering off nucleons can be used to probe neutrinophilic mediators with GeV-scale masses. We find that constraints on the pseudoscalar (axial vector) neutrinophilic mediator are close to the scalar (vector) case since they have similar cross section in the neutrino massless limit. We perform an analysis on the measured muon spectra at <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>FASER</c:mi><c:mi>ν</c:mi></c:math>, and find that the bounds on the vector mediator from the current <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>FASER</e:mi><e:mi>ν</e:mi></e:math> data are comparable to the existing bounds at <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msub><g:mi>m</g:mi><g:msup><g:mi>Z</g:mi><g:mo>′</g:mo></g:msup></g:msub><g:mo>≈</g:mo><g:mn>0.2</g:mn><g:mtext> </g:mtext><g:mtext> </g:mtext><g:mi>GeV</g:mi></g:math>. We also study the sensitivities to a neutrinophilic mediator at future Forward Physics Facilities including FLArE and <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mrow><i:mi>FASER</i:mi><i:mi>ν</i:mi><i:mn>2</i:mn></i:mrow></i:math> by using both the missing transverse momentum and the charge identification information. We find that FLArE and <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mrow><k:mi>FASER</k:mi><k:mi>ν</k:mi><k:mn>2</k:mn></k:mrow></k:math> can impose stronger bounds on both the scalar and vector neutrinophilic mediators than the existing bounds. The constraints on the scalar mediator can reach 0.08 (0.1) for <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:msub><m:mi>m</m:mi><m:mi>ϕ</m:mi></m:msub><m:mo>≲</m:mo><m:mn>1</m:mn><m:mtext> </m:mtext><m:mtext> </m:mtext><m:mi>GeV</m:mi></m:math> with (without) muon charge identification at <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mrow><o:mi>FASER</o:mi><o:mi>ν</o:mi><o:mn>2</o:mn></o:mrow></o:math>. Published by the American Physical Society 2024