lindorblu on "search by tags"

Hi!
I need to modify this part of code to have search by tags.

<?php
						$author_args = array(
									'taxonomy'        =>'authors',
									'show_option_all' => __( 'All Authors', 'raakbookoo' ),
									'hide_empty'      => 1,
									'orderby'         => 'slug',
									'order'           => 'ASC',
									'name'            => 'authors'
						);
						$author = get_term_by( 'slug', get_query_var( 'authors' ), 'authors' );
						if ( $author ) {
							$author_args['selected'] = $author->term_id;
						}
						wp_dropdown_categories( $author_args );
					?>

Anyone could help? Thank you :)