$('span a:not(".sample")').hide();
can be used in this specific scenario.
Nevertheless, if you want to hide the parentheses as well, you will have to create a custom function to remove only the unwanted code:
$('span').html(function(i,old) {
return old.substring(0,old.indexOf('('));
});​
http://jsfiddle.net/pkMgP/
If you prefer to hide it instead of deleting it, you can wrap everything in an HTML element and apply styles to it accordingly:
$('span').html(function(i,old) {
var idx = old.indexOf('(');
return old.substring(0,idx) + '<span style="display:none">' + old.substring(idx) + '</span>';
});​
http://jsfiddle.net/pkMgP/1/