Firstly, if you want the regex not to capture the "Name=" part, you should specify it explicitly before the capture group.
Secondly, for me, it works (if you give proper field name):
Thirdly, why the \d* at the end? You have more data you're not showing us?
@PickleRick Thanks for your reply i have added the screenshot for my output please have a look and the log also.
I don't know what your "-_raw" field is supposed to mean. The field name (with an exception for splunk's internal field like _raw or _time) has to start on a letter. Drop the "field=" option completely (even with matching _raw, you shouldn't use it - the rex command matches to _raw by default and specifying it explicitly can have performance impact - at least that's what the docs say).
If you match your regex to whole event, you should... get all event up to any apersand ("&") signs.