Final answer:
The decisional role that the middle managers need to assume is disseminator.
Step-by-step explanation:
The decisional role that the company's middle managers will need to assume in order to adapt themselves to the new CEO's different personality is disseminator. Jurgen Hambrecht is known for his easy affability, which indicates that he is likely to encourage open communication and engage with his employees. As disseminators, middle managers will need to effectively communicate the CEO's vision, goals, and decisions to the rest of the organization, ensuring that everyone understands and can align their efforts accordingly.