How to return the index of multi value field in the search results in Lucene?

I have a document that contains tags field, I add it like this:

for (Tag tag : tags) { //rock, disco, jazz
   fields.add(new StringField("Tag", tag.name, Field.Store.YES))
}

Now, when I perform the search I would like to get not only document that has a tag, but also specific index within the Tag field that matches the query.
For, example, now when I search for jazz I need also within search results index=2. To know exact tag that was matched (because I use also prefix search and phrase search).

How can I achieve that with Lucene?