During practice of meditation when notice thoughts disappear . experience peace and happy . innerconversation has lost. what is this state?
The state described is basic samadhi ('concentration'; 'collectedness'), which ideally is to be maintained & developed when meditating. MN 19 describes about how the Buddha-To-Be developed samadhi, in the following manner:
I steadied my mind internally, quieted it, brought it to singleness, and concentrated it...So that my mind was not strained. Tireless energy was aroused in me and unremitting mindfulness was established, my body was tranquil and untroubled, my mind concentrated and unified. Quite secluded from sensual pleasures, secluded from unwholesome states, I entered upon and abided in the first jhāna, which is accompanied by applied and sustained mind, with rapture and pleasure born of seclusion.
Are you trying to practice Samadhi?
How I practice, Samadhi plays only a supportive role. When I started practicing Mahasi dry Satipatthana I was practicing Samadhi by accident(I hear that this is a common thing with beginners of this kind of practice). I was not focusing on the actual moment by moment sensation of the breath. I was focusing on my own moment by moment "guess" of what the breath actually was. I would picture the breath in my mind or I would focus on the noting word "rising, falling" or "in, out" in some way but none of these things were an actual reality happening moment by moment. I was feeling great peace but I wasn't practicing the way I intended to practice.
At some point I started just watching the sensation of the breath as it happened and I stopped experiencing so much peace during this practice but this is the way to "see things as they are" and gain wisdom but I still got to practice Metta.
When I practice Metta, I feel great peace and joy. The mindfulness gained from seeing things as they are allows me to know when to have metta or compassion for myself.
This is just what I have experienced. I hope it helps.