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Energy difference between accelerated particles and Jets

  1. Mar 13, 2010 #1

    In the LHC particles are speed up to 7 TeV, smashing protons into "jets". I asked someone if these jets could also smash up surrounding protons and his answer was no because jets have far less energy. But he couldn't tell the energy difference, so my question is how much energy do these jets actually have compared to accelerated protons, in the sense of striking power? And what is actually the minimum striking force needed to make a proton disperse?


  2. jcsd
  3. Mar 24, 2010 #2
    I was doing some research concerning your questions, and I found this following information for a more concrete definition of Jets:

    Extracted from: http://www.symmetrymagazine.org/cms/?pid=1000558

    Also, you were wondering about the data regarding Jets, here I found these graphs which may be useful too:

    http://cms.web.cern.ch/cms/Media/Publications/CMStimes/PhysicsArchive/Simulations/SM_15.html [Broken]
    Last edited by a moderator: May 4, 2017
  4. Mar 25, 2010 #3
    striking force for proton to disapear:

    I interpret this as the energy to separate the proton to scatter with it's constituents, i.e. "hard" scattering (when p+p -> something becomes quark + gluon -> something etc) these reactions will become important when the centre of mass energy is above the masses of the protons, i.e. a few GeV
  5. Mar 25, 2010 #4
    Yes, that's what I was referring to.

    What I don't understand is that there is a of lot of (binding) energy in an proton, and that it looks a like something is boiling, generating or experiencing forces like gravity, the electro-magnetic, strong and weak force. And there is like you point out a few GeV needed to brake it apart. But when it comes to collisions it turns out that all energy is preserved though subdivided over particles, so you can only put energy in it, and don't get any out of it, in other words it looks like death weight.

    I expected that it to be like a spinning top that get's to be smashed, which would release a lot of it's inbound energy by adding momentum to every scattered projectile, along with the striking force that hit the spinning top. So the overall striking force coming out of the collision would be bigger as what has been put in it.

    Jets leave only "minimum ionization" tracks in the detectors which look the same whether they move at 0.99 or 0.999999 times the velocity of light. In the case of accelerating protons a lot of extra energy is needed for these "small" difference. The CMS Times Physics site says: "By combining the information given by the tracker and the calorimeter using a method known as the Jet Plus Track (JPT) algorithm, it is possible to improve significantly the jet energy resolution and response linearity." Could this mean that there still is a wide margin possible, although yet improved?
  6. Mar 25, 2010 #5
    The amount of energy in a proton is its mass. To get extra kinetic energy, you would have to end up with particles that have less total mass, but conservation laws can make that impossible. If two protons collide, at the end of the day there will necessarily be at least two baryons to conserve baryon number. Protons are the lightest possible baryon, so there's no possible way to "liberate" energy in a proton-proton collision. You would have to have something like a proton and anti-proton for that.

    Sorry, I can't quite follow what you're asking here.
  7. Mar 25, 2010 #6
    Ok perhaps the most silly question of the day, but what is the difference between something that is dead an something that is alive, hasn't a proton got a spirit that keeps thing going?
  8. Mar 29, 2010 #7
    Question to the moderators:

    There were 2 last posts here that have gone missing. A similar thing happened, in the https://www.physicsforums.com/showthread.php?t=388398" topic, where a post from "Bob S" was erased. I know the forum has been down, but is it perhaps possible to check what went wrong. And restore the data that has gone missing.

    kind regards,

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  9. Mar 29, 2010 #8


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  10. Apr 5, 2010 #9
    I have a better formulation; what I meant is, what happens with the global positive force that a proton has. Isn't there a factor such as "the whole is greater than the sum of its parts" that needs to be taken into account when colliding particles?
  11. Apr 5, 2010 #10
    global positive force?
  12. Apr 5, 2010 #11
    A proton is a subatomic particle with an electric charge of +1 elementary charge. So all the particles and the interaction within the proton form globally a positive force (charge) of +1.
  13. Apr 5, 2010 #12
    Yes I know I am phd student i theoretical particle physics

    I am trying to understand what you are really after, since I presume that you dont have any physics background?
  14. Apr 5, 2010 #13
    Indeed I have little understanding, but there is one thing that puzzles me. A proton is some sort of organism/mechanism that has a charge, and when collided and smashed into pieces it's mass and energy is divided over the different parts, due to the conservation of energy. But for most organisms the specific way of bundling all the different bits and pieces generates an "extra" that defines the organism, there is a reason why something is build in a particular way, some sort of power gain. Like you can stack a group of bricks and one type of formation is stronger than the other, making it more resistant than the individual building bricks, and to a certain level indestructible. So when you do destroy the composition there is more resistance force (inertia) released than the separate pieces all have together?
  15. Apr 5, 2010 #14
    You are trying to mix methaphysics into physics again.

    I don't think you have understood the concepts of inertia and force either so why use those nomenclatures?
  16. Apr 5, 2010 #15
    As you wish, but we see nuclei that remain stable for billions of years, but, if that nuclei had one more particle in it, the forces put upon its particles cause them to decay with a half-life of seconds. There is an infinite energy difference between these compositions. Why is that?

    If the life-span of a proton is billions of years isn't that a form of inertia?
  17. Apr 6, 2010 #16

    1) no there is not an infinite energy difference between a stable nucleus and a non-stable one, how did you count?

    2) I thought we were discussing the proton and jets?
  18. Apr 6, 2010 #17
    I was referring to nuclear particles,
    http://en.wikipedia.org/wiki/Top_quark" [Broken] The Standard Model predicts its lifetime to be roughly 5×10^−25 s.
    http://en.wikipedia.org/wiki/Proton" [Broken] Protons are observed to be stable and their empirically observed half-life is at least 6.6×10^35 yr.

    Yes, and if I may bring up http://en.wikipedia.org/wiki/Fictitious_forces" [Broken] I would like to quote this bit of information from the wiki-page:

    Thus, measurement of the tension in the string identifies the inertial frame: it is the one where the tension in the string provides exactly the centripetal force demanded by the motion as it is observed in that frame, and not a different value. That is, the inertial frame is the one where the fictitious forces vanish.
    So much for fictitious forces due to rotation. However, for linear acceleration, Newton expressed the idea of undetectability of straight-line accelerations held in common: If bodies, any how moved among themselves, are urged in the direction of parallel lines by equal accelerative forces, they will continue to move among themselves, after the same manner as if they had been urged by no such forces. (http://en.wikipedia.org/wiki/Inertial_frame#Separating_non-inertial_from_inertial_reference_frames")

    So the energy of linear flying particles before and after collisions is according to Newton undetectability, thus fictitious forces within the proton stay undetected.
    Last edited by a moderator: May 4, 2017
  19. Apr 6, 2010 #18
    you are in some way becoming more and more blurry what you really want to know

    where is the infinite energy difference?
  20. Apr 6, 2010 #19
    A quark on it's own last a fraction of a second, one in a proton infinitely, I think the difference is quite clear.
  21. Apr 6, 2010 #20
    ok now I getting the picture, you are dressing your actual question with physics terms used incorrectly, there IS no inifinte energy difference between say a bound quark and a free quark. Why didn't you simply ask why a quark bound in a proton doesn't decay, instead of invoking spirits and other stuff?

    This is the "same" question as why the neutron as a free particle has a "lifetime" of approx 10 minutes, wheras bound in a nucleus it is stable.

    The reason for this has to do with stability of a configuration, the nucleus is stable since the overall configuration has lower energy then the nucleus minus the neutron going to its decay products. Physical systems strive to obtain an energy configuration as stable as possible, compare with the ball which "wants" to roll down the hill instead of just stopping half ways down.
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