How to make Drum Hi Hat stop (open-closed on the one note) ?

I'm not totally clear on what you mean. The General MIDI standard - which MuseScore uses - provides separate sounds for stick on open hi-hat, stick on closed hi-hat, and pedal closing. Just use the appropriate note for the sound you want. Using the standard "Drumset" instrument, these sounds are associated with the eleventh, seventh, and ninth notes on the palette respectively. Or are you saying you want a different sound than one of these three? Maybe you want to have the sound of the open hi-hat being struck but then choked off with the pedal? Best way to notate that would be using two notes - the open hi-hat note followed by the pedal note. If you'd rather notate the choke using articulation symbols, you could always hide the actual note.

I want to do the same thing... I want the open hat to ring ONLY on it's note value and stop completely. Not ring through the next beat, like when you have your foot on the pedal and then just lift your foot to cut the ringing hat.