How to use dynamic URL parameters in Magento 2 to change layout for A/B testing and display different content

namespace DMTQ\Catalog\Observer;

use Magento\Framework\Event\ObserverInterface;
use Magento\Framework\Event\Observer;
use Magento\Framework\App\RequestInterface;

class LayoutChangeEventListener implements ObserverInterface
{
    /**
     * Request
     * @var RequestInterface
     */
    protected RequestInterface $_request;

    /**
     * Class constructor
     * @param RequestInterface $request
     */
    public function __construct(
        RequestInterface           $request,
    )
    {
        $this->_request = $request;
    }

    public function execute(Observer $observer)
    {
        $layout = $observer->getLayout();
        $fullActionName = $observer->getFullActionName();
        if ($fullActionName === 'catalog_product_view') {
            $ad = $this->_request->getParam('ab');
            if ($ad == 'b') {
                $layout->getUpdate()->addHandle('catalog_product_view_b');
            }
        }
    }
}