function ret = accelerationDueToPushBeam(this, PositionVector, VelocityVector)
    % is the distance between the chamber center and the cross point of push beam and z-axis (along the gravity)
    WaveVectorEndPoint = [0, 1, this.DistanceBetweenPushBeamAnd3DMOTCenter/this.PushBeamDistance];
    WaveVectorEndPoint = WaveVectorEndPoint./norm(WaveVectorEndPoint);
    Origin=[0,0,0];

    SaturationIntensity = this.calculateLocalSaturationIntensity(this.PushBeamSaturationIntensity, PositionVector, Origin, WaveVectorEndPoint, this.PushBeamRadius, this.PushBeamWaist);
    
    DopplerShift = (VelocityVector * WaveVectorEndPoint(1:3)') * this.PushBeamWaveVector;
    
    Detuning = this.PushBeamDetuning - DopplerShift;

    a_push = (Helper.PhysicsConstants.PlanckConstantReduced * this.PushBeamWaveVector * WaveVectorEndPoint(1:3)/Helper.PhysicsConstants.Dy164Mass).*(this.PushBeamLinewidth * 0.5) .* ...
             (SaturationIntensity/(1 + SaturationIntensity + (4 * (Detuning./this.PushBeamLinewidth).^2)));
             
    if this.SpontaneousEmission
        a_scatter = this.accelerationDueToSpontaneousEmissionProcess(SaturationIntensity, SaturationIntensity, Detuning, this.PushBeamLinewidth, this.PushBeamWaveVector);
    else
        a_scatter = [0,0,0];
    end

    a_total = a_push + a_scatter;
    
    ret = a_total(1:3);
end