Bimaximal mixing refers to a proposed form of the lepton mixing matrix. It is characterized by the 
  
    
      
        
          ν
          
            3
          
        
      
    
    {\displaystyle \nu _{3}}
  
 neutrino being a bimaximal mixture of 
  
    
      
        
          ν
          
            μ
          
        
      
    
    {\displaystyle \nu _{\mu }}
  
 and 
  
    
      
        
          ν
          
            τ
          
        
      
    
    {\displaystyle \nu _{\tau }}
  
 and being completely decoupled from the 
  
    
      
        
          ν
          
            e
          
        
      
    
    {\displaystyle \nu _{e}}
  
, i.e. a uniform mixture of 
  
    
      
        
          ν
          
            μ
          
        
      
    
    {\displaystyle \nu _{\mu }}
  
 and 
  
    
      
        
          ν
          
            τ
          
        
      
    
    {\displaystyle \nu _{\tau }}
  
. The 
  
    
      
        
          ν
          
            e
          
        
      
    
    {\displaystyle \nu _{e}}
  
 is consequently a uniform mixture of 
  
    
      
        
          ν
          
            1
          
        
      
    
    {\displaystyle \nu _{1}}
  
 and 
  
    
      
        
          ν
          
            2
          
        
      
    
    {\displaystyle \nu _{2}}
  
. Other notable properties are the symmetries between the 
  
    
      
        
          ν
          
            μ
          
        
      
    
    {\displaystyle \nu _{\mu }}
  
 and 
  
    
      
        
          ν
          
            τ
          
        
      
    
    {\displaystyle \nu _{\tau }}
  
 flavours and 
  
    
      
        
          ν
          
            1
          
        
      
    
    {\displaystyle \nu _{1}}
  
 and 
  
    
      
        
          ν
          
            2
          
        
      
    
    {\displaystyle \nu _{2}}
  
 mass eigenstates and an absence of CP violation. The moduli squared of the matrix elements have to be:
 According to PDG convention: 7 , bimaximal mixing corresponds to 
  
    
      
        
          θ
          
            12
          
        
        =
        
          θ
          
            23
          
        
        =
        
          45
          
            ∘
          
        
      
    
    {\displaystyle \theta _{12}=\theta _{23}=45^{\circ }}
  
 and 
  
    
      
        
          θ
          
            13
          
        
        =
        
          δ
          
            13
          
        
        =
        0
      
    
    {\displaystyle \theta _{13}=\delta _{13}=0}
  
, which produces following matrix:: 24 
 Alternatively, 
  
    
      
        
          θ
          
            12
          
        
        =
        
          θ
          
            23
          
        
        =
        −
        
          45
          
            ∘
          
        
      
    
    {\displaystyle \theta _{12}=\theta _{23}=-45^{\circ }}
  
 and 
  
    
      
        
          θ
          
            13
          
        
        =
        
          δ
          
            13
          
        
        =
        0
      
    
    {\displaystyle \theta _{13}=\delta _{13}=0}
  
 can be used, which corresponds to:: 5 
 The L/E flatness of the electron-like event ratio at Super-Kamiokande severely restricts the CP-conserving neutrino mixing matrices
to the form:: 7 
 Bimaximal mixing corresponds to 
  
    
      
        θ
        =
        
          45
          
            ∘
          
        
      
    
    {\displaystyle \theta =45^{\circ }}
  
. Tribimaximal mixing and golden-ratio mixing also correspond to an angle in the above parametrization. Bimaximal mixing, along with these other mixing schemes, have been falsified by a non-zero 
  
    
      
        
          θ
          
            13
          
        
      
    
    {\displaystyle \theta _{13}}
  
.