Joystick Raycast Problem?

Hi to all)) I use if(Physics.Raycast(ray, out hit, 4.0f)){ for placing or delete block on screen position touch. But even if i touch my Joystick or another button, raycast delete block when i touch my Joystick. I allready try to use LayerMask but with no succes How can i ignore my Joystick from RayCasting? Can any one help me with this? Here the part of my code:

 if (Input.GetMouseButtonDown(0)){ 
 if(buttonTimer == 0){
 if(hand.gameObject.active == true){    
 Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
 RaycastHit hit;
 if(Physics.Raycast(ray, out hit, 4.0f)){    
 Vector3 hitPoint = hit.point + (ray.direction.normalized * 0.01f);
 IntVect blockHitPoint = new IntVect((int)hitPoint.x, (int)hitPoint.z,    (int)hitPoint.y);
 m_World.Dig(blockHitPoint, hitPoint);
 }
 buttonTimer = buttonCoolDown;
 }
 }

Please some one help me figure it out. I search this forum, and find some answer, but it didnt help me(

I update code to use Touch Input, but problem is still.

   if (Input.touchCount == 1 ) {
     Touch touch = Input.touches[0];
     if(hand.gameObject.active == true){    
     if(touch.phase == TouchPhase.Began){
     if(buttonTimer == 0){
     Ray ray = Camera.main.ScreenPointToRay(touch.position);
     RaycastHit hit;
     if(Physics.Raycast(ray, out hit, 4.0f)){    
     Vector3 hitPoint = hit.point + (ray.direction.normalized * 0.01f);
     IntVect blockHitPoint = new IntVect((int)hitPoint.x, (int)hitPoint.z, (int)hitPoint.y);
     m_World.Dig(blockHitPoint, hitPoint);
     }    
     buttonTimer = buttonCoolDown;
     }
     }
     }
     }