How to track with GA signup when cookie is lost by spring security login

gaSpringSecurityLogin.js

//Ajax callback after signup form validation
if (data.status == 'ok'){                
  trackSignupOkPageViewToGA()
  sendFormToLoginNewUser()
}

//Call GA trackePageview for a fake url
function trackSignupOkPageViewToGA(){
  if (typeof _gaq !== "undefined" && _gaq !== null) {
    _gaq.push(['_trackPageview', '/signupDone']);
    //Push the login function to make sure the conversion track happens
    _gaq.push(function() { sendFormToLoginNewUser() });
  }
  else sendFormToLoginNewUser()
}