Time-honored rituals of the rock ‘n’ roll experience were observed on Thursday at the (incongruously-named) Jiffy Lube Live, as the erstwhile Nissan Pavilion hosted a characteristically impassioned performance by Pearl Jam and a commensurately fervent showing from one of contemporary music’s most loyal fan bases. Many “Jammers” arrived hours in advance to tailgate in the parking lots, trade stories about past shows, and animatedly speculate on the evening’s set list. Once inside, they stood at rapt attention throughout the concert, snapping photos continuously, raising lighters occasionally, and shouting along so loudly to every song that Eddie Vedder eventually yielded the mic, letting 25,000 voices belt out the first verse of “Better Man” as he strummed along on guitar. Only the most jaded observer would fail to be impressed by such an ardent and earnest crowd response.