transform template code from page to category

Hi,
I’m currently using the current template:

<?php
/**
 * Template Name: Include arbo
 *
 * This is the template that displays all pages by default.
 * Please note that this is the WordPress construct of pages
 * and that other 'pages' on your WordPress site will use a
 * different template.
 *
 * @package WordPress
 * @subpackage Twenty_Twelve
 * @since Twenty Twelve 1.0
 * // <?php get_sidebar(); ?>
 */

get_header();
	?><ul id="extra-sidebar-lt" class="widget-area" role="complementary">
<?php dynamic_sidebar( 'sidebar-4' ); ?>
</ul><?php 

$args=array(
  'cat' => '61',
  'orderby' => 'title',
  'order' => 'ASC',
  'posts_per_page'=>-1,
  'caller_get_posts'=>1
);
$my_query = new WP_Query($args);

if( $my_query->have_posts() ) {

	if
	 ($my_query->have_posts()) : $my_query->the_post();
 ?><div id="lt-title"><?php
$categories = get_the_category();
$separator = ' ';
$output = '';
if($categories){
	foreach($categories as $category) {
		$output .= '<a href="" title="' . esc_attr( sprintf( __( "View all posts in %s" ), $category->name ) ) . '">'.$category->cat_name.'</a>'.$separator;
	}
echo trim($output, $separator);
}
?></div><?php

endif;
?><div id="lt" class="LTclass"><?php
 while 

 ($my_query->have_posts()) : $my_query->the_post();
    $this_char = strtoupper(substr($post->post_title,0,1));

  if ($this_char != $last_char) {
       $last_ord = ord($last_char);
       while ( $last_char >= 'A' && (ord($this_char) - $last_ord) > 1) {
          ++$last_ord;
          $last_char = chr($last_ord);

		  echo '<div id="lettra"><a name="'.$last_char.'"></a></div>';

       }
       $last_char = $this_char;
      echo '<a name="'.$last_char.'"></a><div id="lettra">'.$last_char.'</div>';
    } ?>
    <p><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a><br/>
    					<?php echo get_post_meta($post->ID, 'description', true); ?>

    </p>
    <?php
  endwhile;
}
?></div><?php

wp_reset_query();
get_footer();
?>

Its used in a page as a custom template.
I want to transform it to be used on the category template.
Here i call the category name : ‘cat’ => ’61’,
so it shows the posts title.

How could it be possible to determine the value of ‘cat’ in this template when surfing on http://../?cat=value

Thx!