**UPDATE:** Issues 6 of Marvel's *Star Wars* and *Darth Vader* comic series.

In the new Disney/Marvel canon, in which all new comics, books, and games are considered to have the same level of canon as the movies, Vader has his first direct confrontation with Luke between Episodes IV and V, but doesn't know who he is. This is shown in the new monthly comic series *Star Wars* (by Marvel; issue #2). After taking Luke's lightsaber, Vader takes a closer look at it and realizes it used to be his own.

![Marvel Star Wars (2015) #2][4]

![enter image description here][5]

Later, in Issue 6, Boba Fett learns the name of the young wannabe-Jedi that blew up the Death Star. **He relays this information to Vader.**

![enter image description here][1]

![enter image description here][2]

Suffice to say, he's not impressed.

![enter image description here][3]

Later, in Issue 6 of the ongoing *Darth Vader* comic series, this scene is shown again and expanded upon. Vader makes the immediate connection to Padme and having been lied to by the Emperor about the exact circumstances of her death. He makes a hologram call to the Emperor similar to the one in TESB:

> The Emperor: Yes, Vader? Ah... I sense your anger. *Great* anger. Have you something to say? Some proud, defiant words? Or are you wise enough to *know your place?*

>(beat)

> Darth Vader: I am angry. You would not have me otherwise. My anger brought me to you. I want you to know--I will not fail. And I understand *us* precisely.

It's worth noting that in the 2004 DVD and 2011 Blu-ray edits, considered to be the current state of canon, the conversation with the Emperor mentioned in the original question is [altered][6]:

> The Emperor: We have a new enemy. The young rebel who destroyed the Death Star. I have no doubt this boy is the offspring of Anakin Skywalker.  
> Darth Vader: How is that possible?  
> The Emperor: Search your feelings, Lord Vader. You will know it to be true. He could destroy us.  
> Darth Vader: He's just a boy. Obi-Wan can no longer help him.  
> The Emperor: The Force is strong with him. The son of Skywalker must not become a Jedi.

It's strongly implied here that Vader and the Emperor had never discussed Luke up until this point. Vader's line "How is that possible?" could originally have meant anything from that he didn't know previously, to that he had guessed but didn't understand the particulars given that he'd thought he'd killed Padmé on the landing platform, to that he wanted to pretend that he hadn't known and was "playing along" the same way that the Emperor was referring to Anakin Skywalker as a third party. This new information eliminates the first interpretation, but the exact meaning of Vader's "how is that possible" is still up to speculation as of issue 6 of the comic series.

  [1]: https://i.sstatic.net/RaOgx.png
  [2]: https://i.sstatic.net/h4kUv.png
  [3]: https://i.sstatic.net/c01ka.png
  [4]: https://i.sstatic.net/NtOGb.png
  [5]: https://i.sstatic.net/WTW8q.png
  [6]: http://scifi.stackexchange.com/questions/6614/why-did-sidious-tell-vader-who-luke-was