LHC starts 8 TeV collisions

Today the Large Hadron Collider smashed protons at 8 TeV for the first time beating last years energy of 7 TeV. Physics runs will begin in about a weeks time. This year they have set an agressive target of 15/fb at this energy. Last year they exceeded predicitons by a factor of five but we should not expect the same again this year. Reaching 15/fb will be a great result and anything more will be spectacular

23 Responses to LHC starts 8 TeV collisions

  1. carla says:

    Last year they managed 3.5/nb/s so this year the max they’re going for is 7/nb/s – is that right?

  2. Lubos Motl says:

    With 7-8 months, one needs 2/fb per month or so which is about 65/pb/day or 2.8/pb/hour or 0.75/nb/s but the max is about 6 times higher than the average, so I only get 5/nb/s or so. Not far from yours. ;-)

    BTW good you’re using the slash convention of ours. ;-)

    I’ve been thinking about renaming the “inverse femtobarn” as “events per femtobarn”. The idea is that this luminosity is multiplied by the cross section of a process to get the number of events in the process.

    Would it be more user-friendly to write the total 2012 luminosity as 15 ev/fb? ;-)

  3. Chris Austin says:

    ev as an abbreviation of events is too similar to eV as an abbreviation of electronvolt. The number of events is a dimensionless number so does not need a unit.

  4. wl59 says:

    You could use the Planck Energy 543 kwh (and its mass equivalent).

    That’s also good for daily live, if you successfully claim at your electricity company that of the planck units would have no fractions, so them current spend measuring and monthly bill must be wrong and you owe them nothing

  5. Tony Smith says:

    If the 2012 runs of the LHC remain as inconclusive as the runs up to 2011, it seems that we might need something better than the 2014/2015 repaired/upgraded LHC to begin to really understand Higgs-related physics.

    Phil said a while back:
    “… If they could revive the tunnel of the abandoned SSC collider in Texas and use niobium-tin magnets it would be possible to build a 100 TeV collider, but the cost would be enormous. …”.

    How enormous would be the cost ?

    Consider that the USA is now spending
    trillions of USdollar-equivalents on Quantitative Easing bail-outs for financial derivative systems of the Big 5 Banks
    why not
    spend a measly $1 trillion on reviving and rebuilding the SSC ?

    Unlike the Big 5 Bank Bailout trillions,
    a lot of the SSC $1 trillion would go into jobs for real people who actually do the construction work of the SSC.

    As in the initial SSC plan, the construction money could be spread all over the USA to subcontractors,
    making the SSC a nationwide job creator
    so that
    even if the revived SSC could be built more cheaply than $1 trillion,
    it should be built to solid-gold specifications to be sure to spend the full $1 trillion
    which would have 2 benefits:
    1 – with no corner-cutting, it would be pretty sure to work at 100 TeV and so to give a lot of interesting new physics;
    2 – it would have full effectiveness as a job creator for subcontractors all over the USA.

    the physics community should quit being so timid
    should say that understanding fundamental physics
    is more important to human civilization than any Derivative Banking Casino
    that a revived SSC will give more jobs/money to the bulk of the population than does putting trillions in the pockets of Derivative Casino Bankers
    will at $1 trillion actually cost LESS than the multi-trillion dollar QE bailouts already spent on the Big Bank Derivative Casino.


    • Lawrence B. Crowell says:

      It makes one pine for the SSC. If accelerator physics is going to really probe this domain we need to think big, like 100TeV. This is particularly if we want to put some of these ideas about extra large dimensions to the test.

    • Dilaton says:

      Yep, Tony Smith is exactly right.

      … Tony Smith for President ;-) !

  6. wl59 says:

    OK, spying out nature continues. Hope we that within 2 months the data are enough for exclude Higgs with more than 95% , finally, to finish with that almost 50 years old zombie.

  7. carla says:

    They’re now running at 0.75 optimum with 264×264 bunches. Optimum running for 1380 bunches would give close to 20/fb for the year so with 0.75 this is already potentially 15/fb/year :)

  8. ondra says:

    Any idea guys why ATLAS has lower lumi than CMS? Thanks in advance.

    • jahonen says:

      I think it is mostly a calibration issue, they haven’t yet performed Van Der Meer (VDM) scans which are used to calibrate the luminosity figures.

  9. kevin says:

    looks like they are going to beat last year’s instantaneous luminosity record this afternoon

  10. Lubos Motl says:

    Hi Phil, do you agree that minutes ago, the LHC has just beaten the immediate luminosity record, to 4.2/nb/s ie 135/fb/year?

    • carla says:

      It’s a bit disappointingly low bearing in mind they predicted a max L this year of 6.8/nb/s and I was hoping they might get to 6.0/nb/s with 1380 bunches over the next few days. Still, there is potential to increase the bunch intensity from 1.3 to 1.6×10^11 p/b and reduce emissivity from 3mm to 2mm over the coming weeks to maximise L.

      Maybe I’m being unrealistically impatient :)

      • Lubos Motl says:

        Dear carla, if 2011 is a good role model, you’re impatient, indeed. ;-) The increases and improvements didn’t happen in the first week of running; the records were being improved pretty much throughout the year.

        At the same moment, I think that 4.2/nb/s would be marginally enough to achieve 15/fb per year if they were really working most of the time and avoided breaks… I also hope the instantaneous luminosity will be raised.

      • carla says:

        @Lubos I think it was estimated that that they would collect around 10/fb this year with last years running parameters from late October. As you say, we’re probably at a level where 15/fb/year is now likely, since we’re also running at 4Tev but… I’m greedy and hoping for 20/fb/year, even if highly unlikely ;)

      • ondra says:

        Carla, check http://indico.cern.ch/getFile.py/access?contribId=7&sessionId=1&resId=1&materialId=slides&confId=162632
        Steve Myers presentation about 2012 lumi.
        Of course, now we are on 0.6 beta and only 1.3e11 bunch intensity with 1092 bunches so its too early to be concerned about 6 or 7/nb/s.
        Concerning integrated lumi it would be much more useful to gain more time in stable beams.

      • anonymous says:

        Carla—For the past week, CMS has had about a 20% higher luminosity than ATLAS. Yet they should be the same (or very close). I suspect one of the groups has a calibration problem, but if that isn’t fixed it’s going to be a big problem in interpreting the results.

      • ondra says:

        CMS just reached 4.55/nb/s with 1.35e11 protons per bunch with 1092 bunches in machine and yesterday recorded almost 200/pb, you can see the potential for 140 days of physics …

      • carla says:

        @ondra where do you get the reading for the number of protons per bunch from?

      • ondra says:

        @carla, from OP Vistars, Dashboard, you take ratio of beam intensity and number of bunches.

  11. nameab says:

    could you tell me Ervin Goldfain ‘s Website or his email


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