PanToTarget.cs

using UnityEngine;
using System.Collections;

public class PanToTarget : MonoBehaviour {

    public GameObject target;


    // Use this for initialization
    void Start () {
        
    }
    
    // Update is called once per frame
    void Update () {
        Vector3 diff = target.transform.position - transform.position;
        float pan = Mathf.Atan2 (diff.x, diff.z);
        transform.rotation = Quaternion.AngleAxis (pan*180f/Mathf.PI + 180, Vector3.up);
    }
}