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Zachary Marshall | USLHC | USA

View Blog | Read Bio

Discovery and the Ocean of New Physics

Hi there!

The LHC is about to start colliding protons at 7 TeV (3.5 TeV per beam) or with about three times more energy than has ever been achieved by man. This is really exciting stuff! We’ll have a big media day on Tuesday to make sure everyone has a front row seat to the event!

Last night I was asked an interesting question – interesting enough that I thought I’d share the answer.

Will we collide the beams at many energies, or only at 7 TeV?

The LHC is really a discovery machine. Imagine that you’re back in 1490, and we’ve built a new ship that is capable of going seven times further than any previous ship in history before it needs to land (to refresh its stores, etc). The first thing we want to do with this is take it as far as it will go to see what’s out there! It could be that we’ll find a whole mess of new particles – that would be wonderful! It could be that we find nothing at all. That really would be like Columbus sailing for the new world and coming to the edge of the earth! It seems impossible and would fly in the face of everything we know – for physicists, it would be almost as interesting as finding a load of new particles! And, of course, when you’re sailing that far, you might pass some interesting things along the way…

End Of The Earth Images

Once you’ve searched for new high energy physics, you might want to try collisions at a few different energies. That would be something like looking for islands in the Atlantic. They might not be as exciting as a new continent, but they’re worth searching for all the same. Technically, just like if we were to sail out, we have no choice but to pass all the energies in between. But we do so for only a moment, and don’t really pause there to do any significant search in the middle. Side note: the middle energies aren’t quite as exciting at the LHC as they would be at, say LEP, because protons are “composite”, rather than single objects (as one professor put it, it’s like colliding two garbage cans). You can get some sense of what’s going on at lower energies from the higher energy collisions.

So on Tuesday, you should expect to see the beams go up from 450 GeV each (when they go into the machine) to 3500 GeV each (when they are colliding) without stopping in the middle – unless they plan something I don’t know about, of course!

One fun (very) technical note. Computers have a clock that keeps them in time (your computer is probably 2 GHz, for example). The whole LHC acts like a giant set of computers, all of which are timed together. It’s as though the entire thing has a single heart beat, around 40 MHz. We actually keep the heartbeat going at just the right pace to always have collisions “on time.” But the protons are changing energy from when they are injected at 450 GeV to when they collide at 3.5 TeV!! That means the entire heartbeat of the machine speeds up just a little bit to keep up (because of relativity, it’s only a fraction of a percent, but it is noticeable!!). To make sure things are safe, ATLAS usually stops collecting data while the heartbeat is actually changing – it’s a delicate operation, and we don’t want to have to stop to fix something right before the data arrives! So we may or may not actually see any of the collisions at energies between 900 GeV and 7 TeV!




4 Responses to “Discovery and the Ocean of New Physics”

  1. Lauren says:

    Zach! Lauren, Rae Anne’s friend from Stanford. I’ve been reading news following the build-up leading into today’s collisions at CERN, and came across your blog when wondering if you were still there. How exciting that you can be right in the middle of all this epic science. Just wanted to say hi and let you know how jealous I am that (a) you’re there seeing this first-hand, and (b) you understand this stuff better than most people. I hope being at CERN is as thrilling as it seems like it would be from here, and that life is treating you well! Feel free to drop me a line if you have any fun stories from Geneva and the time to pass them along :)

  2. Dear Dr……,

    Very small free roaming particles lifetime very short.[free photons, free notron, free proton,free
    electron ,vs].And their lifetime is its energy Mc2. Protons are observed to be stable and their theoretical minimum half-life is 1×10’36 years.Grand unified theories generally predict. That proton
    decay should take place, although experiments so far have only resulted in a lower limit 10’35 years for proton’s lifetime. I see that. The earth lifetime is its Mc’2 energy. When this is calculated
    the lifetime of earth.

    Earth Mass= 5.97×10’24 kg. the lifetime 1 kg of mass in space is 2851927903,26 years.

    Earth Lifetime is 1.7×10’34 years. I think that, this is a very interesting result.

    Best regarts
    Salih Kırcalar

  3. Zach says:

    Hi Salih,

    Mc^2 is an energy, called the “rest energy” of a particle. The lifetime of a particle doesn’t seem to be related to its energy. It is, somehow, related to the “width” of the mass of the particle (usually quite a bit smaller than its mass). For an electron or proton, as far as we know, the width is zero (zero lifetime).

    The lifetime is Planck’s constant (6×10^-34) divided by the width.

    So the rest energy of Earth is around 10^34 joules, and the lower limit on the lifetime of a proton is around 10^35 years.

    All things considered, probably a coincidence – given that units like “years” and “joules” are pretty human-centric units! (I could make up a unit, widibos, where the lifetime of the proton is more than 15 widibos, and the rest energy of the earth would change in my new system of units…).

    Hope that helps!

  4. Dear Zach,
    Many Thanks for your comments. But Please to visit in my web
    site http://www.timeflow.org Thanks again.

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