Not sure if it will work with AngularJS v1.2.0-rc.2 with ui-router v0.2.0. I have tested this solution on AngularJS v1.3.14 with ui-router v0.2.13.
I just realize that is not necessary to pass the parameter in the URL as gwhn recommends.
Just add your parameters with a default value on your state definition. Your state can still have an Url value.
$stateProvider.state('state1', {
url : '/url',
templateUrl : "new.html",
controller : 'TestController',
params: {new_param: null}
});
and add the param to $state.go()
$state.go('state1',{new_param: "Going places!"});