Question

An excellent introduction for a mathematician without previous exposure to quantum field theory is the book by Gerald Folland: "Quantum field theory, a tourist guide for mathematicians", ISBN: 978-0-8218-4705-3. To understand the standard model, one first needs to learn about quantum field theory, since this is an example of QFT model, although a rather formidable one. I think you will have a hard time finding a more pedagogical introduction to this subject than Folland's book.