Is there any connection between pizza and Pisa(city of leaning tower)

No.

The term 'pizza' first appeared "in a Latin text from the southern Italian town of Gaeta in 997 AD, which claims that a tenant of certain property is to give the bishop of Gaeta duodecim pizze 'twelve pizzas' every Christmas Day, and another twelve every Easter Sunday".

Prepare to salivate : https://en.wikipedia.org/wiki/Pizza

The town of Pisa, although the origins of the name remain a mystery, has no connection with the yummy foodstuff.

Prepare to tilt head : https://en.wikipedia.org/wiki/Pisa

The connection is that you can get pizza in Pisa.

http://www.tripadvisor.co.uk/Restaurants-g187899-c31-Pisa_Province_of_Pisa_Tuscany.html

Remember that the tomato wasn't introduced to the European Continent until around 1500AD after Columbus returned with the fruit from the New World. Pizza actually means pie and what we think of as pizza today has no connection to food of a thousand years ago. https://en.wikipedia.org/wiki/Tomato