Raycasting on iPhone

Unity Engine
1

How do you control a game object on screen with touch? Right now my object just jumps into the air right when the game starts:

var Player : GameObject;
function Update () {
    if (Input.GetButtonDown) {
        // Construct a ray from the current mouse coordinates
        var ray = Camera.main.ScreenPointToRay (Input.mousePosition);
        if (Physics.Raycast (ray)) {
           
           rigidbody.velocity.y = 5;
        }
    }
}
2 
	function Update () {
		
     for(touch in iPhoneInput.touches)
  
     rigidbody.AddForce (0,20,20);
     
 
     }

I changed the script around, but now the entire screen is reacting to touch. How do I limit it to just a single game object?