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Richard Ruiz | Univ. of Pittsburgh | U.S.A.

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Five Inverse Femtobarns

Hi All! Great news: the CMS Experiment, just a moment ago, announced that the LHC delivered 5fb-1 today!

Figure 1: Proof. It happened. (Image: Mine)

This is terrific news and if you happen to see a member of CERN’s accelerator division, be sure to congratulate her or him.

Figure 2: Total (integrated) luminosity delivered to (red) and recorded by (blue) the CMS detector. (Image: CMS)

To give a little context, 1 fb-1 (pronounced: one inverse femtobarn) worth of data is measure of the number proton collisions (scaled by a bunch of physics and efficiency parameters) and is the equivalent of 70 trillion proton-proton collisions. So 5 fb-1 is 350 trillion proton-proton collisions, which is 3.5 × 1014 = 350,000,000,000,000 proton-proton collisions. Before the start of collisions this year, the LHC had only delivered about 35 pb-1 (0.035 fb-1), which is only about 2.45 trillion = 2,450,000,000,000 proton-proton collisions. In other words, 99.3% of the data generated by the LHC came between this past March and Today. How can you not be impressed by that? 😀

Figure 3: Total (integrated) luminosity recorded by ATLAS (black/behind green), CMS (green), LHCb (blue), and ALICE (red). (Image: CERN)

Figure 4: Log of total (integrated) luminosity recorded by ATLAS (black/behind green), CMS (green), LHCb (blue), and ALICE (red). (Image: CERN)

Due to detector efficiencies and such, not all the data generated is recorded. The above plot, generated & continuously updated by CERN, shows that ATLAS and CMS have a small bit before reaching 5 fb-1. However, it is very reasonable to suggest that both experiments will have recorded 5 fb-1 before the end of the third week of November October. (Thanks to Achintya & Dave for catching this mistake. I have “week 43” in my notes for this post, so I have no idea how I ended up with the November date.)



As always, happy colliding.

– richard (@bravelittlemuon)

PS. I refer you to a previous post about what the experiments can do with 5 fb-1.


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