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Adam Yurkewicz | USLHC | USA

View Blog | Read Bio

Days and Weeks

Life is getting very exciting again at CERN.  In conversations about the future we are now using the words “days” and “weeks” instead of “months” and “years”.  Now that beam is back in the LHC, we are eagerly awaiting the first collisions.  The ATLAS detector has been operating 24 hours/7 days a week for a while now, and is ready.  The next milestone will be proton beams going all the way around the LHC ring.  Then the big milestone will be the first collisions of protons in the LHC.

While obviously we want collisions, the question is what can we do with the small amount of data we expect to collect this year?  We will not make any big discoveries in 2009.  We mainly want to establish that the detector is working well and to begin doing some basic checks. This starts with timing.  All of the different parts of the detector (that work pretty much independently of one another) have to be synchronized with each other down to the nanosecond level, something that is very hard to do without an absolute reference.  One really nice reference is a particle traveling through several different subdetectors.

The next thing we can do is find the first “jets” (sprays of particles formed from quarks and gluons), electrons, muons, and so on, the basic particles that our detector is built to detect. After that we can start to calibrate the detector.  This is mainly done by comparing measurements of particles from one part of the detector to measurements of similar particles from other parts of the detector, and also by checking that we measure basic things like the masses of well-known particles to be the same as measured many times by previous experiments.

After being so close last fall, it has been a long wait to get back to this point.  When the explosion happened last September, few people would have guessed it would take this long to get back to this point.  But the excitement of last fall has returned.  The line to get through the gates into CERN was a little longer this morning, parking has been much tougher to find the last couple of weeks, and (of course) the number of meetings is increasing.  After all the years of preparation, we are finally at the start of a wonderful new era of discovery.


14 Responses to “Days and Weeks”

  1. Jeff Handy says:

    Please just be sure, when you destroy the entire universe, that it’s quick and painless. ;) Kidding! I’m just hoping nothing bad happens again. Finally getting real full-powered data will be quite exciting regardless of the wait for enough data for discovery. It’s great to see the buzz happening once again!

  2. heyhey says:

    Cool! I eagerly await whatever might come of this.

  3. Wallmott says:

    Is the LHC delayed even more?

    On Cersn web site they have changed “The first High energy collisions will most likley occur after mid december” to “The first high energy collisions will most likely occur in early 2010″

  4. Lac Léman says:

    Hi Wallmott,

    Indeed, there is some more delay. Cern’s communication is somewhat inconsistent. This time it seems to be much less severe. They just wanna make sure they don’t blow the thing up again :-)
    The status overview (slide 3) of the LPC Monday Meeting looks promising and the schedule foresees at least some slightly accelerated (2×1.2 Tev) collisions (slide 6) for christmas.
    The most recent large presentation about the LHC Status is from Monday by Steve Myers, held at the HCP2009 – Hadron Collider Physics Symposium.

    Current status info is available at the
    LPC Monday Meetings.

  5. > “The first high energy collisions will most likely occur in early 2010″

    What they mean technically is: they want collisions with center-of-mass energy around 2.1 before christmas. This is called “low energy” even though it would make it the highest energy collider in the world.

    Then, next year they will ramp up that center-of-mass energy to maybe something between 5 and 7 TeV. This is called “high” energy, even though it’s half or less of design energy.

  6. Regit says:

    isnt Tevatron already makin Center of Mass energy collisions superior than the LHC will do this year?

  7. Regit says:

    and where is going to be the collisions?

  8. Adam Yurkewicz says:

    Hi Regit,
    The Tevatron is colliding protons and antiprotons at 1.96 TeV center of mass energy. The LHC will start colliding protons against protons at 0.9 TeV, then possibly increase to about 2.4 TeV in December. Hopefully early next year, the energy will be increased to about 7 TeV. The ultimate goal is for collisions at 14 TeV, but that doesn’t look like it will happen until 2012.


  9. Wallmott says:

    Is there a big difference bettwen colliding Protons and anti protons to protons and protons?

  10. Adam Yurkewicz says:

    Hi Wallmott,
    Protons and antiprotons are made out of different kinds of quarks, and even though we say we are colliding protons and antiprotons, we are really colliding the quarks inside. So yes, there are some differences. We can do the physics studies either way, but we need to account for this difference.
    Proton-proton colliders are a little easier to build because antiprotons have to be produced (and stored while you are making all you need) and that is harder for antiprotons than protons.
    The number of collisions you have when you steer two beams of particles towards each other increases (a good thing) when you have more particles in each beam, whether they be protons or antiprotons. The limitation in a proton-antiproton collider is how many antiprotons you can have at a time.


  11. Wallmott says:

    Are there any differences in the results in the collisions bettwen antiproton – proton collisions and proton – proton collisions?

    I just have one more wierd question that i need to have answerd for one of my projects in school that i hope someone can answer.

    Say just in theory, would proton to proton collisions be more dangerous then a proton – antiproton collision?

    I have this question because i have found that some fear mongers were against RHIC and now the LHC but never any mention of Tevatron. It seems odd since Tevatron is way more powerfull in energy then RHIC.

    Sorry for my stupid question but i hope someone can answer it.

    I know both are safe but i just wanted to know why there were never any mention of any antiproton – proton colliders.

  12. Adam Yurkewicz says:

    Hi Wallmott,
    >Say just in theory, would proton to proton collisions be more dangerous then a >proton – antiproton collision?

    No, I think if one were dangerous the other would be as well. Of course, neither one is dangerous.
    The recent fearmongering was more based on the energy of the collisions (which will eventually be higher at the LHC).


  13. Lac Léman says:

    Hi Wallmott,

    RHIC was perceived as more dangerous than the tevatron because it can collide gold ions, thus, with more quarks involved, potentially producing more strange quarks than in proton antiproton collisions and turn the whole planet into a strangelet, which unsurprisingly didn’t happen yet :-)
    There are two enlightening articles about that hype by Professor Robert P. Crease, a philosopher and historian at Stony Brook who wrote for physics world [
    1, 2]. Learn about “doxoids”, compound particles of bad thinking ;-)
    LHC has got higher energy and a lot more luminosity (moooore particle collisions)than the tevatron. So it’s a much more promising doomsday machine.

  14. Jimbo says:

    Hi Adam,

    In one of your replies, you mention 2.4 Tev as an energy level to be explored at LHC. Is there as particle physics reason for this or is it accelerator based ?


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