Investor Steve Mandel of the hedge fund Lone Pine Capital has acquired 7 percent of Dunkin’ Brands Group, according to a report posted on the Nasdaq’s website. Mandel bought more than 7 million shares, paying $29 per share on average, according to GuruFocus Real Time Picks. Dunkin’ shares have gained 22 percent so far this year. They have been publicly traded for just over a year.