Electrical charge and Mass

1. Jun 30, 2005

pallidin

Greetings.

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

Thanks.

2. Jun 30, 2005

mikeu

No, the neutron has roughly the same mass as the proton but zero charge...

3. Jun 30, 2005

dextercioby

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

Daniel.

4. Jun 30, 2005

fliptomato

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.

Best,
Flip

5. Jun 30, 2005

pallidin

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.

6. Jun 30, 2005

pallidin

OK, but out of the fundamental particle group, does ANY fundamental particle without charge have mass?

7. Jun 30, 2005

ZapperZ

Staff Emeritus
Example: Neutrinos, all three flavors.

Zz.

8. Jun 30, 2005

pallidin

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.

9. Jul 4, 2005

ambresh

Hey, I think it would be better to say that every charged particle has mass.

10. Jul 4, 2005

Spin_Network

11. Jul 4, 2005

Spin_Network

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?

12. Jul 4, 2005

seratend

Before paradoxes, what do you mean by a zero point energy source?

Seratend. : )

13. Jul 4, 2005

El Hombre Invisible

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?

14. Jul 4, 2005

juvenal

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.

15. Jul 5, 2005

El Hombre Invisible

The Z0 is a virtual boson, isn't it?

16. Jul 5, 2005

Meir Achuz

The Z0 has a short lifetime, ~3X10^-25 sec, but it is just as real as other unstable particles.

17. Jul 5, 2005

El Hombre Invisible

I did not know that. I have always been told that the W and Z bosons were virtual. Can the Z0s be observed?

18. Jul 5, 2005

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

$$m = \sqrt {E_{total}^2 - (m_{total} c^2)^2}$$

If you get the $Z^0$ mass, then those particles likely came from a $Z^0$ decay.

Of course, you have to take into account the "background" from random combinations of particles that weren't produced by $Z^0$ 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 $Z^0$ 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.

19. Jul 5, 2005

El Hombre Invisible

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.

20. Jul 5, 2005

juvenal

Define "directly observed".