ARFoundationSample.AirTapGesture.cs

using UnityEngine;

public class AirTapGesture : MonoBehaviour
{
    [SerializeField] private Camera ArCamera;

    private void Update()
    {
        if (Input.touchCount <= 0) return;

        var touch = Input.GetTouch(0);
        if (touch.phase == TouchPhase.Began)
        {
            // rayを照射
            var ray = this.ArCamera.ScreenPointToRay(touch.position);

            // Cubeをタップした場合はCubeを配置する
            RaycastHit hit;
            var hasHit = Physics.Raycast(ray, out hit);
            if (hasHit)
            {
                var target = hit.collider.gameObject;
                if (target.name.Contains("Cube"))
                {
                    var clone = Instantiate(target); // Clone
                    clone.AddComponent<Rigidbody>();
                }
            }
        }
    }
}