2012

[Deepwater6]

http://www.bbc.co.uk/news/science-environment-16070460

 

A few things to look forward to this year... Hope everyone has a nice holiday.

[phision]

http://www.bbc.co.uk...onment-16070460

 

 

Read the above link and found: "20 inverse femtobarns of data", can anyone enlighten me to what the BBC was trying to convey here? Is a Barn not a unit of area?

[CraigD]

Read the above link and found: "20 inverse femtobarns of data", can anyone enlighten me to what the BBC was trying to convey here? Is a Barn not a unit of area?

The barn is a unit of area, 10^-28 m², so a femtobarn is 10^-43 m².

 

An "inverse barn" or "inverse femtobarn" is a bit of a misnomer, as it doesn't mean 10²⁸ or 10⁴³ m^-2, but 10²⁸ or 10⁴³ events/m². Thus, it's a unit of the product of the "brightness" of particle physics sources, the efficiency of the detection apparatus, and the duration of the experiments.

 

All said, I think events per unit area is an awkward, confusing unit compared to simply a count of events, so not as useful to the non-specialist.

[phision]

All said, I think events per unit area is an awkward, confusing unit compared to simply a count of events, so not as useful to the non-specialist.

 

Thank you CraigD. I agree, it is awkward!

 

I also believe the author of the article didn't understand the unit as it should have been described as a data set relating to an instantaneous luminosity if associated with a time scale(ie fb⁻¹s⁻¹), to describe a productive rate, or a data set relating to an integrated luminosity, to descibe a total productivity. It may only have been a grammatical error, but one the renders the description as useless to anyone who does not use this terminology in the abbrivated language that people who use this unit every-day must do!

[maddog]

Read the above link and found: "20 inverse femtobarns of data", can anyone enlighten me to what the BBC was trying to convey here? Is a Barn not a unit of area?

Uhh, Yeah I see where this could sound a bit physhy (excuse my pun).

 

I would interpret the phrase "20 inverse femtobarns of data" as "20 / femtobarns of data" or

data = 20/fb (i.e. 20 event per femtobarn). You are right this does sound like a luminosity like value

(as events per unit area).

 

Definition of fb = femtobarn is as CraigD already said.

 

maddog

[phision]

This web page(http://cdsweb.cern.c...d/1450229?ln=en) shows the fb^-1 unit being used more accurately, than the BBC page linked above, as it refers to the integrated luminosity and the data set thereof!

[LaurieAG]

This web page(http://cdsweb.cern.c...d/1450229?ln=en) shows the fb^-1 unit being used more accurately, than the BBC page linked above, as it refers to the integrated luminosity and the data set thereof!

 

But they seem more intent on matching data rates than going back through their old data and excluding the same LHCb bunches from their old data sets.

 

The LHC is back to record collision rates and matching the 2011 data set now seems within reach for the summer conferences.

 

Either way it is going to be very interesting.

 

For info on 2012 click on the attached link and enter dates after 21/12/2012 (look at xmas eve). I picked this up on a lounge thread ages ago.

 

http://starroot.com/cgi/daycalc.pl

Edited November 29, 2012 by LaurieAG