To change the mouse parameters :
xinput list # to list the peripherals, note the good number!
xinput list-props 9 #list parameters from peripheral number 9
xinput set-prop 9 'Device Accel Constant Deceleration' 3 # set the acceleration of peripheral 9 to value 3. The higher the value is, the more you divide the acceleration. Acceleration is maximum for a value equal to 1. The "basis" value seems to be 1.7, for me...
To permanently set the change :
A hidden file in your directory is ".profile" (Ctrl+H to see hidden files)
Double click on it and open it. Copy paste the previous command at the end. That's it!
P.S. to apply the same command for all users you can edit the file /etc/profile (not an hidden file).