Displaying Woocommerce Product Category in WordPress

woocommerce categories are not a “category” they’re the product_cat taxonomy. change your args like so:

$params = array(
    'posts_per_page' => 5,
    'post_type' => 'product',
    'tax_query' => array(
        array(
            'taxonomy' => 'product_cat',
            'field' => 'slug',
            'terms' => 'cap'
        )
    )
);