Search found 14 matches

by zaim
Fri Apr 20, 2012 11:22 am
Forum: The Accelerator
Topic: 2012 Events Discussion
Replies: 100
Views: 79684

Re: 2012 Events Discussion

If we can trust the CMS lumi, they have delivered 1 fb^-1 in 2012 with the current fill. No doubt the LHC is running very smoothly.
by zaim
Sun May 29, 2011 5:19 pm
Forum: The Accelerator
Topic: 2011 Events Discussion
Replies: 184
Views: 44869

Re: 2011 Events Discussion

Just now the LHC surpassed 0.5 fb^-1 integrated luminosity delivered to CMS.
Current fill of 32 pb^-1 plus the 468 ps^-1 stated here https://twiki.cern.ch/twiki/bin/view/CM ... licResults
by zaim
Thu Apr 21, 2011 8:20 pm
Forum: The Accelerator
Topic: 2011 Events Discussion
Replies: 184
Views: 44869

Re: 2011 Events Discussion

What do you mean about 2m squeeze? I am pretty sure I saw 1.5m at CMS and ALTAS in the 480 fill. LHCb and ALICE does not have problems with the luminosity directly, but with the number of collisions per bunch crossing. When two high intensity bunches which is squeezed tightly collides, there may be ...
by zaim
Sun Apr 17, 2011 8:30 pm
Forum: The Accelerator
Topic: 2011 Events Discussion
Replies: 184
Views: 44869

Re: 2011 Events Discussion

You can see the Tevatron records here http://www-bd.fnal.gov/pplot/today/DataSummaryTables.html. The luminosity record at the Tevatron is 402.4 (ub.s)^-1, so the LHC is not quit there yet, but in a couple of days, it will surpass its American counterpart. A record it did take however, was integrated...
by zaim
Thu Feb 24, 2011 12:04 pm
Forum: The Accelerator
Topic: The Hump
Replies: 20
Views: 7702

Re: The Hump

The hump is maybe gone!!!!!

from todays meeting:
"Since the start-up we did not see any sign of the hump (for the first time)
...but we do not know what has changed that made it disappear
Monitoring to detect any change
"
by zaim
Thu Jul 15, 2010 10:24 am
Forum: ALICE
Topic: Alice having difficulties?
Replies: 4
Views: 3707

Re: Alice having difficulties?

Alice gets less luminosity in order to avoid pile up. I.e. they dont want more than one collision per crossing. See e.g. the footnote on these figures http://lpc.web.cern.ch/lpc/lumiplots.htm I visited the Alice cavern a year ago, it was clear that they were not as close to be ready for collisions a...
by zaim
Sat Jul 10, 2010 5:22 pm
Forum: The Accelerator
Topic: Current Events Discussion
Replies: 512
Views: 91923

Re: Current Events Discussion

First of all they have only begone to scratch the surface. They need about 10,000 times more data than they have now, to be able to say anything certain about e.g. the Higgs mechanism. When this is said they where able to publish the first physics results already months ago, with only very little da...
by zaim
Tue Jul 06, 2010 10:17 pm
Forum: The Accelerator
Topic: Target beam separation / reduced luminosity in ALICE
Replies: 4
Views: 1975

Re: Target beam separation / reduced luminosity in ALICE

A guess could be that they are having problems with pileup. I.e. problems reconstruction the tracks of particles when there are more than one collision per intersection. This would explain why it comes at the same time as the intensity per bunch is increased. Alice is a little different from CMS and...
by zaim
Mon May 24, 2010 5:59 pm
Forum: The Accelerator
Topic: Current Events Discussion
Replies: 512
Views: 91923

Re: Current Events Discussion

Now when there is no beam, it seams like a good time to give a status over the weekend + monday so far. Fill 1117 - CMS wasn't reporting luminosity during the first part of this fill. They probably recorded a bit more than Atlas Atlas : Integrated luminosity: 9.342e+002 ub^-1 Alice : Integrated lumi...
by zaim
Wed May 19, 2010 5:08 pm
Forum: Science
Topic: Let's go hump hunting!
Replies: 86
Views: 24412

Re: Let's go hump hunting!

Hump still there. From tuesday:

13:28: B1 and B2 10^11 injected OK
13:44: We lost half of B2 doing a Q' measurement;
Probably we hit the hump during the measurement
by zaim
Tue May 18, 2010 1:05 am
Forum: Science
Topic: Luminance, luminosity, squeezing explained in English
Replies: 14
Views: 10316

Re: Luminance, luminosity, squeezing explained in English

nice post Tau. The luminosity can be used to calculate expected rates (R). You just need to know the cross section (sigma) of the process and multiply it with the luminosity (L), ie R=sigma L. In this blog post http://pdg2.lbl.gov/atlasblog/?p=339 the author has plotted the cross section for differe...
by zaim
Tue May 11, 2010 10:25 pm
Forum: The Accelerator
Topic: Actual progress of the LHC-physics-programm
Replies: 18
Views: 5275

Re: Actual progress of the LHC-physics-programm

A good place to learn about the progress is the LHCC meetings from the 5th of May. Here is the agenda http://indico.cern.ch/conferenceDisplay.py?confId=92525 and in video http://cdsweb.cern.ch/record/1264592/ (part 1 and 2 are reversed apparently) Conclusion is something like: ~1.1nb^-1 data and eve...
by zaim
Sat Dec 05, 2009 7:49 pm
Forum: Science
Topic: Summer student lectures
Replies: 6
Views: 5348

Summer student lectures

While you wait for collisions, there are many hours of entertainment in watching the summer student lectures: http://indico.cern.ch/tools/SSLPdisplay.py?stdate=2009-06-29&nbweeks=8 The summer student program is a summer school for ~140 student every summer. I attended the 2009 summer program, and it...