What is the difference between "Bhāva" and "Ātman" in Pali I have read in Buddhist text, Buddhism is about "Bhāva" and not "Ātman". 

What is the difference between "Bhāva" and "Ātman"?
Both have their places in Buddhist thought/practice.

First, the definitions:


bhāva: condition; nature; becoming
atta (ātman is the Sanskrit form): self; ego; soul


Here are a couple of relevant quotes:


  In Buddhist thought, bhāva denotes the continuity of life and death, including reincarnation, and the maturation arising therefrom. (source)


So, bhāva could be described as the "seamlessness of existence".


  Although the Buddha argued that no permanent, unchanging "self" can be found, some Buddhist schools, sutras and tantras present the notion of an atman or permanent "Self", although mostly referring to an Absolute and not to a personal self. (source)


And atta is about the person in the moment; though as mentioned above, it's really more about a higher level conceptual "self".

In Buddhist thought, the opposite of atta (anatta) is a generally more significant concept:


  In Buddhism, the term anattā refers to the perception of "not-self", recommended as one of the seven beneficial perceptions, which along with the perception of dukkha and impermanence is also formally classified among the three marks of existence. (source)


I hope this helps!