Why acknowledgement time for broadcasting packet is more than that of unicast packet?

In broadcast message, ACK comes after 1.6 second and in unicast message, ACK comes after ~200 ms. I am sending API frame.

I searched on the internet that node who get the broadcast message will relay the same, but I can see only receive packet not transmit packet.

Why the time difference between ACK is large?

In broadcast, intermediate nodes re-transmit received broadcast messages. However, they do not send it again on UART out line. That’s why user see just single entry of that packet on XCTU screen.

You didn’t mention which XBee variant you are using. In broadcast, module reports ack as soon as it is finish up with transmission (along with duplicates). While in unicast, module transmit once and report Ack as soon as it receives success delivery status from destination (which should the case in your setup).
If delivery is not successful then it goes for multiple retry attempts. In such scenario, you will see that unitcast Ack are taking lot more time.

I am using XBee series 2, suppose I have three hop network. When source broadcast the packet, all one hop node will get that message and relay it. To track the packet again I need to broadcast the packet from one hop node to second hop node?
Is there any method to reach upto destination without broadcasting the packet second time? or all the nodes will get that message??

In broadcast, each and every node of network will receive that message. No need to initiate transmission again from second hop node.

And from that packet I can detect source’s address as well.
Thank you very much, it really helped a lot.