Correlating nonresonant di-electron searches at the LHC to the Cabibbo-angle anomaly and lepton flavor universality violation

In addition to the existing strong indications for lepton flavor universality violation in low-energy precision experiments, the CMS Collaboration at CERN recently released an analysis of nonresonant dilepton pairs which could constitute the first sign of lepton flavor universality violation in high-energy searches at the LHC. In this article, we show that the Cabibbo-angle anomaly, an (apparent) violation of first row and column Cabibbo-Kobayashi-Maskawa (CKM) matrix unitarity with <math display="inline"><mo>≈</mo><mn>3</mn><mi>σ</mi></math> significance, and the CMS result can be correlated and commonly explained in a model-independent way by the operator <math display="inline"><mo stretchy="false">[</mo><msubsup><mi>Q</mi><mrow><mo>ℓ</mo><mi>q</mi></mrow><mrow><mo stretchy="false">(</mo><mn>3</mn><mo stretchy="false">)</mo></mrow></msubsup><msub><mo stretchy="false">]</mo><mn>1111</mn></msub><mo>=</mo><mo stretchy="false">(</mo><msub><mover accent="true"><mo>ℓ</mo><mo stretchy="false">¯</mo></mover><mn>1</mn></msub><msup><mi>γ</mi><mi>μ</mi></msup><msup><mi>σ</mi><mi>I</mi></msup><msub><mo>ℓ</mo><mn>1</mn></msub><mo stretchy="false">)</mo><mo stretchy="false">(</mo><msub><mover accent="true"><mi>q</mi><mo stretchy="false">¯</mo></mover><mn>1</mn></msub><msub><mi>γ</mi><mi>μ</mi></msub><msup><mi>σ</mi><mi>I</mi></msup><msub><mi>q</mi><mn>1</mn></msub><mo stretchy="false">)</mo></math>. This is possible without violating the bounds from the nonresonant dilepton search of ATLAS (which interestingly also observed slightly more events than expected in the electron channel) nor from <math display="inline"><mi>R</mi><mo stretchy="false">(</mo><mi>π</mi><mo stretchy="false">)</mo><mo>=</mo><mi>π</mi><mo stretchy="false">→</mo><mi>μ</mi><mi>ν</mi><mo stretchy="false">/</mo><mi>π</mi><mo stretchy="false">→</mo><mi>e</mi><mi>ν</mi></math>. We find a combined preference for the new physics hypothesis of <math display="inline"><mn>4.5</mn><mi>σ</mi></math> and predict <math display="inline"><mn>1.0004</mn><mo>&lt;</mo><mi>R</mi><mo stretchy="false">(</mo><mi>π</mi><mo stretchy="false">)</mo><mo>&lt;</mo><mn>1.0009</mn></math> (95% C.L.) which can be tested in the near future with the forthcoming results of the PEN experiment.