Dismiss Notice
Join Physics Forums Today!

Electrical charge and Mass

  1. Jun 30, 2005 #1

    I read somewhere that ONLY particles with an electrical charge possess mass.
    Is that true?

  2. jcsd
  3. Jun 30, 2005 #2
    No, the neutron has roughly the same mass as the proton but zero charge...
  4. Jun 30, 2005 #3


    User Avatar
    Science Advisor
    Homework Helper

    The Z vector boson is the heaviest counterexample.Until we find (if we find) the Higgs boson.

  5. Jun 30, 2005 #4
    re: relation of electric charge and mass

    Mass comes from the breaking of the SU(2)xU(1) gauge symmetry by the Higgs boson. The Higgs gets a "vacuum expectation value" (vev) at low energies and creates effective mass terms in the Lagrangian. (There are no mass terms in the high-energy Lagrangian--they break chiral symmetry.)

    Electric charge comes from that same SU(2)xU(1) gauge symmetry, the charge of a particle depends on its representation in the symmetry group.

    In this sense, the mass terms for particles and the electric charge of those particles can be traced back to this SU(2)xU(1) symmetry, but they're two very different things.

  6. Jun 30, 2005 #5
    To my understanding, the neutron is not a fundamental particle, rather is a amalgamation of charged and non-charged "particles". Thus, it's electrical identity is not "neutral" in subdivided states, though it is as a whole.
  7. Jun 30, 2005 #6
    OK, but out of the fundamental particle group, does ANY fundamental particle without charge have mass?
  8. Jun 30, 2005 #7


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    Example: Neutrinos, all three flavors.

  9. Jun 30, 2005 #8
    Great. Thanks.
    From viewing http://physicsweb.org/articles/world/11/7/3/1 it is clear that there is a growing experimental evidence that the neutrino has mass.
    I would posit that such evidence lay's to rest the notion that electrical charge is immutably related to mass.

    Thanks again.
  10. Jul 4, 2005 #9
    Hey, I think it would be better to say that every charged particle has mass.
  11. Jul 4, 2005 #10
  12. Jul 4, 2005 #11
    If Mass of a body, is a Measure of its Energy, then if Energy Changes, so does Mass!

    If a body moves towards C, then its Mass increases thus, conversely if a body comes to rest, so does its Mass?

    There are paradox's for Mass to Energy Ratio's, this is evident when has a Zero-Point-Energy source...and then accelerate's it to close to the speed of light..this translates to an Infinity-Point-Energy source?
  13. Jul 4, 2005 #12
    Before paradoxes, what do you mean by a zero point energy source?

    Seratend. : )
  14. Jul 4, 2005 #13
    When that article states that most of the mass of, say, a proton is comprised on the (kinetic) energy of its quarks and gluons, I think you can infer that the proton is at rest. If the proton is not at rest, then you are measuring its relativistic mass. As 'mass' is generally taken to mean 'rest mass', it's not helpful to consider the proton as anything other than at rest. It's rest mass, then, is the sum of the relativistic masses of its components (quarks and gluons). Gluons have no rest mass, but because of their motion have relativistic mass (like the photon).

    As far as I know, all real particles that are known for sure to have mass also have charge. The neutrino and Higgs boson may prove this incorrect, but as their masses are not yet known for sure, this is pending. Some virtual bosons have mass without charge, but no real ones. I've raised this question before. Cool to see it in a thread.

    What's with the arbitrary upper case characters?
  15. Jul 4, 2005 #14
    As Daniel pointed out - the Z0 is a fundamental particle that is neutral and quite heavy. And its discoverers (or at least the heads/founders of the collaboration that discovered it) got Nobel prizes in 1984.
  16. Jul 5, 2005 #15
    The Z0 is a virtual boson, isn't it?
  17. Jul 5, 2005 #16

    Meir Achuz

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    The Z0 has a short lifetime, ~3X10^-25 sec, but it is just as real as other unstable particles.
  18. Jul 5, 2005 #17
    I did not know that. I have always been told that the W and Z bosons were virtual. Can the Z0s be observed?
  19. Jul 5, 2005 #18


    User Avatar

    Staff: Mentor

    Yes, and as Juvenal pointed out, they have been, as far back as 1984.

    Basically, you look for the combinations of particles that they're supposed to decay into, calculate the total momentum and energy of those particles, and then the invariant mass from

    [tex]m = \sqrt {E_{total}^2 - (m_{total} c^2)^2}[/tex]

    If you get the [itex]Z^0[/itex] mass, then those particles likely came from a [itex]Z^0[/itex] decay.

    Of course, you have to take into account the "background" from random combinations of particles that weren't produced by [itex]Z^0[/itex] decay, that just happen to have the right energy and momentum. So you end up with statements like, "Out of xx candidate events, we conclude that yy of them are [itex]Z^0[/itex] decays, with a confidence level of zz%." This applies for the detection of any particle that is so short-lived that we can't observe its tracks directly in a bubble chamber or electronic track-detector.
  20. Jul 5, 2005 #19
    Sorry, I meant directly observed. However, I seem to have misunderstood that relevant point here that Z0s, like photons, can be virtual or real, which kind of makes my question redundant.
  21. Jul 5, 2005 #20
    Define "directly observed".