As to the double-checking, the analysis behind this result used the whole data set collected by the BaBar experiment at the Stanford Linear Accelerator (SLAC). So that's years of data, and the experiment hasn't been running since 2008. The question of course is, can some other experiment produce the same results. As this is B-physics I would guess LHCb, one of the 4 main experiments at CERN's LHC, might be able to do this, but I really don't know for sure.
If you can repeat the same experiment and get another 3 sigma deviation from the Standard Model predictions then yes, you could combine the results to get a >3 sigma total (though they don't simply just add up to 6).
As to the double-checking, the analysis behind this result used the whole data set collected by the BaBar experiment at the Stanford Linear Accelerator (SLAC). So that's years of data, and the experiment hasn't been running since 2008. The question of course is, can some other experiment produce the same results. As this is B-physics I would guess LHCb, one of the 4 main experiments at CERN's LHC, might be able to do this, but I really don't know for sure.
If you can repeat the same experiment and get another 3 sigma deviation from the Standard Model predictions then yes, you could combine the results to get a >3 sigma total (though they don't simply just add up to 6).