Winger Lowe bagged a first-half brace, while Luke McGrath touched down just 30 seconds after the break, as the Irish province prevailed in the battle between the top two in the pool’s standings.
Scarlets at least picked up a losing bonus point thanks to Dan Jones’ second penalty of the game in the closing stages, meaning they now sit three points behind the leaders.
In Conference A, Munster missed out on the chance to narrow the gap to runaway leaders Glasgow as they suffered a 25-18 defeat at Cardiff Blues.
Jarrod Evans kicked two conversions and a pair of penalties for the Blues, who scored 19 points in the space of eight first-half minutes but were forced to withstand a second-half fightback from the visitors.
Tyler Bleyendaal slotted over a penalty with the final kick of the game to at least secure Munster a losing bonus point, although they now trail the Warriors by 16 points in the fight to secure a semi-final spot.
Sign up to our mailing list for a weekly digest from the wide world of rugby.Sign Up Now