How come I experience a discrepancy between reported clicks for an Cxense Display campaign and the Google Analytics reported referrals for that specific landing page?
First of all, Cxense Display reports clicks or unique clicks while Google Analytics reports visits on referral level. That's like comparing apples with oranges.
Secondly, there are a lot of technical obstacles between the Ad Servers click and Google Analytics registering a correct referral source. Please read the section “Referrers” in the Google Support link below where DFP themselves advise against such a comparison.
“Comparing referrer URLs to DFP clicks is not advised. Referrers in analytics are not an accurate measure of clicks or landings…”
“Comparing Apples to Oranges – Clicks vs. Visits”