What tense should paper titles use?
First: the usual (read: boring) way of writing academic paper titles is indeed without verbs:


  A study of acquired growth hormone deficiency
  and hypogonadotropic hypogonadism in a subject with repeated head trauma


or using gerunds (which is a verb form, but in that case is used to construct a present progressive but a noun phrase):


  Understanding acquired growth hormone deficiency
  and hypogonadotropic hypogonadism in a subject with repeated head trauma




However, I think include a verb is possible, and oftentimes makes the title much catchier and appealing to the non-specialist reader. For example, the titles I “quoted” above are of my own making, but the real title for the article (and believe me, you want to read it) is:


  Acquired growth hormone deficiency and hypogonadotropic hypogonadism in a subject with repeated head trauma, or Tintin goes to the neurologist


There: even if I know nothing of “acquired growth hormone deficiency” and “hypogonadotropic hypogonadism”, I know what the paper is about.

Now, if you use verbs in article titles, they are mostly going to be about established facts, generic questions, mathematical proofs, … which means you should write in the present tense.


  
  Vitamin C enriched diet can prevent scurvy
  Minesweeper is NP-complete
  


I particularly like to use questions in titles, as they make quite clear the problem you're tackling:


  
  How hard is the measurement of quartz hardness? A review of the commercial available apparatuses and their robustness
  How fast does the swallow fly? Reexamining the impact of the bird's geographical origin
  


In a few cases, you would talk about a historical event, and then you'd use the past tense:


  
  How World War One was won: the role of time travelers from the twenty-second century
  The CERN measurement was not a fluke: finally establishing the Higgs discovery at the 10-sigma level