(A) Unless otherwise agreed by the parties or pursuant to the rules governing the arbitration, an arbitrator may be challenged only if circumstances exist that give rise to justifiable doubts as to his independence or impartiality, or as to his possession of the qualifications upon which the parties have agreed.

(B) A party may challenge an arbitrator appointed by it, or in whose appointment it has participated, only for reasons of which the party becomes aware after the appointment has been made.