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### One Recorded Inverse Femtobarn!!!

Last week I announced that LHC reached the 2011 milestone of delivering one inverse femtobarn of luminosity to LHCb. This week, LHCb reached the 2011 milestone of recording one inverse femtobarn of data.

There is a subtle difference between these two statements, which is better illustrated in the graph below, where it can see that the delivered and recorded integrated luminosities are different, and the difference seems to grow with time.

So what exactly does “delivered” and “recorded” integrated luminsoity actually mean? Surprisingly for physics, they mean exactly how they sound. That is, delivered integrated luminosity refers to the integrated luminosity of proton-proton collisions which the LHC has delivered to LHCb while recorded luminosity refers to the amount of data we have recorded on disk. We obviously want these to be as close to each other as possible, but as I’ve mentioned before, this is not possible due to the detector hardware.

You may all be wondering why LHCb is celebrating one inverse femtobarn while ATLAS and CMS are celebrating five inverse femtobarns. This is due to the fact that the design instantaneous luminosities for LHCb is much lower than for ATLAS and CMS. In fact, at the beginning of the year, the milestone of one inverse femtobarn seemed almost unachievable. This remarkable accomplishment has only been possible due to the excellent performance of both the LHC team in implementing luminosity leveling and the LHCb team in running the detector at higher instantaneous luminosity than it was initial designed for.

In terms of physics, one inverse femtobarn of data corresponds to about seventy billion b quark pairs decaying in the LHCb detector. This huge amount of data allows us to significantly increase the accuracy of our results like $$\phi_s$$. It also increases the statistics of various rare decays like $$B_{s}\rightarrow\mu\mu$$. Stay tuned for more results!

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