The Sonos soundbars do not have a Bluetooth transmitter. 

In fact, the Sonos Ace connects using a WiFi signal to a Sonos soundbar, not a Bluetooth signal. 

I only want to connect a simple headphone, it works for few second and than it’s disconnected is anybody can help me ? 

I’d assume you’re connecting to the tv rather than soundbar? And then the HDMI-ARC re-establishes connection to the soundbar? 

Sonos soundbars do not transmit Bluetooth.  TVs do have Bluetooth transmitters to use with headphones, but they are often overridden by soundbars that are connected via HDMI-ARC.  To prevent this, you need to turn CEC off on the TV before connecting the bluetooth device. 

I really thank you both answer I’ll try and I’ll let you know 

best Antonio