J.Lo comes in at No. 2.

50 Cent's "The Massacre" (Shady/Aftermath/Interscope) bursts onto The Billboard 200 with U.S. sales of 1.14 million units, according to Nielsen SoundScan. The figure -- the rapper's best sales week ever -- topples last week's No. 1, Omarion's "O" (T.U.G./Epic/Sony Music), sending it down to No. 8 on a 58% decline to 77,000.

"Massacre" stands as the sixth-largest opening week since Nielsen SoundScan began tracking sales in 1991. Also, as previously reported, 50 Cent breaks his own record for the largest sales total by far of any title with a shortened release week. His previous record for an abbreviated first week came with his first album, "Get Rich or Die Tryin'," which opened with 872,000 in February 2003.

50 Cent leads a quartet of high-profile debuts this week.

Jennifer Lopez takes second place with her fourth studio album, "Rebirth." The Epic set bows with 261,000 units, falling short of her previous albums. Lopez earned her first No. 1 with 2001's "J.Lo" -- which started with 272,000 and has earned 3.7 million to date -– and her second the following year with the remix record "J to Tha L-O!" –- which opened with 156,000 and has a total of 1.4 million.

Jack Johnson scores his biggest sales week with his third Brush Fire Records set, "In Between Dreams," which bows at No. 3 with 228,000 units. Johnson also started at No. 3 with 2003's "On & On," which has sold 1.2 million after opening with 132,000. His best-selling title remains his 2001 debut, "Brushfire Fairytales," at 1.7 million.

The Mars Volta bows at No. 4 with "Frances the Mute" (Strummer/Universal), which sells 123,000 -- marking the duo's biggest sales week and highest-charting album to date. 2003's "De-Loused in the Comatorium" debuted at No. 34 with just 28,000.

The Game’s "The Documentary" (Aftermath/G-Unit/Interscope) drops 4-5 on a 5% slide to 100,000, while Green Day's "American Idiot" (Reprise) takes a 3-6 tumble on a 21% decline to 86,000.

Ray Charles' "Genius Loves Company" (Concord/Hear Music) falls 2-7 on a 26% slope to 81,000. Kelly Clarkson's "Breakaway" (RCA) inches 10-9 despite a 2% fall to 63,000. Eminem's "Encore" (Shady/Aftermath/Interscope) dips 8-10 on a 13% decline to 61,000.

The return of original vocalist Rob Halford for Judas Priest's "Angel of Retribution" (Epic) leads to the group's highest-charting album and biggest sales week ever, at No. 13 with 58,000 copies. The band previously went as high as No. 17 with the Columbia sets "Turbo" in 1986 and "Screaming for Vengeance" in 1982.

Jamie O'Neal is back after five years with her best week ever, as "Brave" (EMI) enters at No. 40 with 25,000 units. Her 2000 Mercury Nashville debut, "Shiver," bowed at No. 165 with just 9,000 and went on to sell 515,000 copies.

Pimp C scores his first chart appearance with "Sweet James Jones Stories" (Rap-A-Lot), at No. 50 with 23,000 units.

Josh Groban gets the Oprah touch this week. His March 2 appearance on Winfrey's talk show brings "Closer" (Reprise) to greatest gainer status, on a 120% boost to 32,000 units. The singer also performed with Beyonce during the Feb. 27 Academy Awards ceremony on ABC.

Overall U.S. album sales are up 8% over last week at 12 million units, 2% higher than the comparable week last year. Sales for 2005 are 9% below last year at 10 million units.