Authorize.net plugin target="_blank"??

Is it possible to launch the Authorize.net payment plugin in a new window instead of the parent window? Would like the user to stay on my page during/after the checkout process.

Yes. You will have to edit the file plugins/hikashoppayment/authorize_end.php and change the line:
<form id="hikashop_authorize_form" name="hikashop_authorize_form" action="<?php echo $method->payment_params->url;?>" method="post">

to:
<form id="hikashop_authorize_form" name="hikashop_authorize_form" action="<?php echo $method->payment_params->url;?>" target="_blank" method="post">