protected function buildTrackingParamsSession()
    {
        $this->utmSession = $this->getSession('utm_session');
        $this->utmSession->setExpiration('30 minutes');

        if ($this->getParameter('utm_source')) {
            $this->utmSession->utmSource = $this->getParameter('utm_source');
        }
        if ($this->getParameter('utm_medium')) {
            $this->utmSession->utmMedium = $this->getParameter('utm_medium');
        }
        if ($this->getParameter('utm_campaign')) {
            $this->utmSession->utmCampaign = $this->getParameter('utm_campaign');
        }
        if ($this->getParameter('utm_content')) {
            $this->utmSession->utmContent = $this->getParameter('utm_content');
        }

        // store additional parameters
        $this->additionalTrackingSession = $this->getSession('additional_tracking_params');
        $this->additionalTrackingSession->setExpiration('30 minutes');

        if ($this->getParameter('banner_variant')) {
            $this->additionalTrackingSession->bannerVariant = $this->getParameter('banner_variant');
        }
    }