How Do I Lock The Y Axis In A Camera Follow Script?

I don't want the camera to follow the player when he jumps.

I'm a beginner and have no idea how to do this. Here is my script...

 using System;
 using UnityEngine;
 
 namespace UnityStandardAssets._2D
 {
     public class Camera2DFollow : MonoBehaviour
     {
         public Transform target;
         public float damping = 1;
         public float lookAheadFactor = 3;
         public float lookAheadReturnSpeed = 0.5f;
         public float lookAheadMoveThreshold = 0.1f;
 
         private float m_OffsetZ;
         private Vector3 m_LastTargetPosition;
         private Vector3 m_CurrentVelocity;
         private Vector3 m_LookAheadPos;
 
         // Use this for initialization
         private void Start()
         {
             m_LastTargetPosition = target.position;
             m_OffsetZ = (transform.position - target.position).z;
             transform.parent = null;
         }
 
 
         // Update is called once per frame
         private void Update()
         {
             // only update lookahead pos if accelerating or changed direction
             float xMoveDelta = (target.position - m_LastTargetPosition).x;
 
             bool updateLookAheadTarget = Mathf.Abs(xMoveDelta) > lookAheadMoveThreshold;
 
             if (updateLookAheadTarget)
             {
                 m_LookAheadPos = lookAheadFactor*Vector3.right*Mathf.Sign(xMoveDelta);
             }
             else
             {
                 m_LookAheadPos = Vector3.MoveTowards(m_LookAheadPos, Vector3.zero, Time.deltaTime*lookAheadReturnSpeed);
             }
 
             Vector3 aheadTargetPos = target.position + m_LookAheadPos + Vector3.forward*m_OffsetZ;
             Vector3 newPos = Vector3.SmoothDamp(transform.position, aheadTargetPos, ref m_CurrentVelocity, damping);
 
             transform.position = newPos;
 
             m_LastTargetPosition = target.position;
         }
     }
 }