$the_category_id    = 10;
$new_posts          = new WP_Query( array(
    \'post_type\'     => \'post\',
    \'post_status\'   => \'publish\',
    \'tax_query\'     => array(
        array(
            \'taxonomy\'          => \'category\',
            \'terms\'             => array( $the_category_id ),
            \'field\'             => \'term_id\',
            \'operator\'          => \'AND\',
            \'include_children\'  => false
        )
    )
) );