Hi
I want to detect just the person that enters
and I want to use a single sensor compatible with arduino
is there a motion sensor one direction
if yes i want his name or his reference
Thank you for your time 
It could be done with two motion sensors covering different areas. Depending on which is triggered first you can determine the direction of travel.
If there's a door you could have a door sensor and a motion sensor. If motion before door sensor triggered that indicates an exit (assuming there isn't other motion in range of the motion detector.
You could also use a camera and computer vision but that's more appropriate for a computer instead of an Arduino.
The Panasonic Grid-Eye 8x8 thermal camera is Arduino compatible, and with the appropriate code could be used to detect humans moving in one direction.