Correct google analytics query parameter for site search ?

Google analytics can provide details of which searches users type into the search gallery box.
Information google analytics require is :

Enter your 'Query Parameter' in the field provided. Please enter only the word or words that designate an internal query parameter such as "term,search,query". Sometimes the word is just a letter, such as "s" or "q". You may provide up to five parameters, separated by a comma.

My question is, what is the correct Query parameter to use with google analytics ?

The resulting URL from imputing a search into gallery with the word "searchstring" is.

http://www.xxxxx.com.au/photos/main.php?g2_return=%2Fphotos%2Fmain.php&g2_formUrl=%2Fphotos%2Fmain.php&g2_authToken=63d04a669967&g2_view=search.SearchScan&g2_form[formName]=search_SearchBlock&g2_form[searchCriteria]=searchstring&g2_form[useDefaultSettings]=1

I guess I strip some part of this URL ? Am I on the right track ?

I am guessing it might be [searchCriteria]=

Thanks