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Have you ever read a post on a subject you felt like you knew a little bit about, and subsequently been absolutely certain that you've missed the entire point due to your now apparent ignorance?

"Doc! Doc! What the hell is an inverse femtobarn?"

No, seriously, I'm into this kind of stuff and I've never heard of that.

Femto is like "milli" or "micro", but equal to 10 to the -15th
or 0.000000000000001

A "barn" is a measure of area (10 to the -28 square meters)
or about the size of the uranium nucleus
(femtobarn = code word from WWII days of developing the atomic bomb)

And from my old math books I finally get use that famous phase:

It naturally follows that: :rolleyes:
The inverse femtobarn is how many particle collision events per femtobarn.

Oh, and here is another phase.
The derivation is left to the reader. :yelsick:

Oh, oh. Here is something that tickled me...

The Higgs particle was named the "God particle" by Peter Higgs, who said,
"No one around him would allow it to be called "that God damn particle".
.

God particles per femtobarn - how much is that in angels per needle point? Attachment 35832

Quote:

Originally Posted by Scriveyn (Post 779440)

God particles per femtobarn - how much is that in angels per needle point? Attachment 35832

It depends on if they are fallen angels or not. Offhand, I'd say one angel per needlepoint.

Quote:

Originally Posted by Lamplighter (Post 779437)

Yes, to the individual meanings of "inverse", "femto", "barn" and "data", but how does tha allow "5 inverse femtobarns of data"???

Okay, femto = 10 to the -28. Inverse femto = 10 to the 28. But barn is area and you don't measure data in terms of area. How can you have any amount of barns of data?

Shopkeeper, I'll have five cubic hours of oranges, please.

I suspect leg-pulling. Maybe a mishievous scientist is feeding BS to an incredulous journalist.

I think the way to look at it is... as the collider runs over time,
the accumulated area of the particles increases.
This value needs to be corrected for the inefficiency of each specific
collider in detecting 100% of the particles (fudge factor=luminosity)

I don't really know what I just said... ;) and
maybe someone can offer a better explanation.
But, in the meantime, as quoted directly from Wikipedia

Quote:

The "inverse femtobarn" (fb−1) is a measurement of particle collision events per femtobarn.
One inverse femtobarn is equal to around 70 million million (70 x 1012) collisions.

Over a period of time, two streams of particles with a cross-sectional area, measured in femtobarns, are directed to collide.
The total number of collisions is directly proportional to the luminosity
of the collisions measured over this time.

Therefore, the collision count can be calculated by multiplying the integrated luminosity
by the sum of the cross-section for those collision processes.
This count is then expressed as inverse femtobarns for the time period (e.g., 100 fb−1 in nine months).

Inverse femtobarns are often quoted as an indication of particle collider effectiveness.
Fermilab has produced 10 fb−1 in the last decade.
Fermilab's Tevatron took about 4 years to reach 1 fb−1 in 2005,
while the Large Hadron Collider experiments ATLAS and CMS reached
over 5 inverse femtobarns of proton-proton data in 2011 alone.

Usage example

As a simplified example, if a beamline runs for 8 hours (28,800 seconds)
at an instantaneous luminosity of 300 × 1030 cm−2s−1 = 300 μb−1s−1,
then it will gather data totaling an integrated luminosity of 8,640,000 μb−1 = 8.64 pb−1 during this period.

By next year, collisions will be occurring – if all continues to go well
– at a rate producing what physicists call one "inverse femtobarn,"
best described as a colossal amount of information for analysts to ponder.

Therefore, it naturally follows in todays news that
they will also need a much bigger computer. :rolleyes:
.

Quote:

Originally Posted by ZenGum (Post 779505)

But barn is area and you don't measure data in terms of area.

Horseshit per acre.

[baits]Good thing we didn't build that under-size one in Texas.[/tw]

Quote:

Fishermen unravel family mystery after month at sea

Uein Buranibwe, 53, and Temaei Tontaake, 26, made headlines late last month when they washed ashore in the Marshall Islands after 33 days lost at sea.

They were more than 600 kilometres from home.

Their global satellite positioning system had run out of batteries after they left their island on what should have been an 80km trip to get gas.

Marshall Islands Journal editor Giff Johnson says the men found much-needed food and water on Namdrik Island.

But he also says that one of the men discovered that his uncle, feared drowned at sea 50 years earlier, had also wound up on the same atoll and married into the community.

The men discovered that they had relatives on the island.

"That was a pretty pleasant surprise to drift at sea for 33 days and wind up on an island where you've got family members," Mr Johnson said.