The reaffirmation of the Outperform rating and the maintenance of a $64 price target by a reputable analyst like Gary Prestopino from Barrington Research could instill confidence among investors and potentially lead to a positive short-term impact on Koppers Holdings' stock price. Analyst ratings, especially those that are positive, can influence market perception and investor sentiment, often leading to an increase in stock price if the market aligns with the analyst's outlook.