Is the Proton's Half Life Really 10 to the Power of 32 Years?

[ElliePhysicsStudent]

Hi

I've been reading websites about particle physics recently, and in some places they say the proton is stable and others they say it is unstable, with a half life of 10 to the power of 32 years. I know it is the most stable baryon.
The only possible decay I've read about is a proton decaying into a positron and a photon, which does not conserve baryon number, in which case, how can it have a half life at all? Are there any other possible decays?
Also, would a proton with a half life of 10 to the power of 32 years be classified as unstable or stable, as my physics teacher argued that this was so long that it would be pretty stable (and also that this was longer than the universe, which I thought physicists hadnt calculated the length of definitively yet).
This could be a stupid question so sorry if it is.
Thankyou
Ellie

 

[selfAdjoint]

Originally posted by ElliePhysicsStudent
Hi

I've been reading websites about particle physics recently, and in some places they say the proton is stable and others they say it is unstable, with a half life of 10 to the power of 32 years. I know it is the most stable baryon.
The only possible decay I've read about is a proton decaying into a positron and a photon, which does not conserve baryon number, in which case, how can it have a half life at all? Are there any other possible decays?
Also, would a proton with a half life of 10 to the power of 32 years be classified as unstable or stable, as my physics teacher argued that this was so long that it would be pretty stable (and also that this was longer than the universe, which I thought physicists hadnt calculated the length of definitively yet).
This could be a stupid question so sorry if it is.
Thankyou
Ellie

They did an experiment where they observed 10^33 protons for a year, and none of them decayed. Nobody has ever reported seeing a proton decay. Some theories require proton decay after a very long time, but those theories haven't yet made enough correct predictions to become highly plausible.

 

[xeguy]

The proton is considered stable on time scales much greater than the age of the universe. Experiments like the one mentioned above establish that proton decay (if it happens) is extremely rare. The experiment referred to was carried out at the Super-Kamiokande water detector in Japan (also used for neutrino research). The lower bound for the proton half-life was something like 10^35 years. When you consider that the agreed upon age of the universe is in the 10-15 billion year range, that corresponds to on the order of 10^9 years. That's why the proton is considered a stable particle, though some Grand Unified Theories predict the decay on very long time scales.

 

[LURCH]

Originally posted by xeguy
... though some Grand Unified Theories predict the decay on very long time scales.

Doesn't the second law of thermodynamics also require it? A proton has mass and therefroe energy. It constitutes a localised density of energy sarounded by an environment of lesser enrgy density. This is a condition that cannot remain intact forever, according to entropy. The energy contained in a small space must radiate otu into its relatively cold saroundings until the two achieve equal energy states, mustn't it?

 

[eagleone]

Originally posted by LURCH
Doesn't the second law of thermodynamics also require it? A proton has mass and therefroe energy. It constitutes a localised density of energy sarounded by an environment of lesser enrgy density. This is a condition that cannot remain intact forever, according to entropy. The energy contained in a small space must radiate otu into its relatively cold saroundings until the two achieve equal energy states, mustn't it?

Well, I don’t know how much I would meddle thermodynamics in that topic, after all it’s statistical model, and it doesn’t consider quantum properties of mass/energy. But theoretically yes. [/color]

 

[suyver]

Originally posted by LURCH
Doesn't the second law of thermodynamics also require it? A proton has mass and therefroe energy. It constitutes a localised density of energy sarounded by an environment of lesser enrgy density. This is a condition that cannot remain intact forever, according to entropy. The energy contained in a small space must radiate otu into its relatively cold saroundings until the two achieve equal energy states, mustn't it?

Following the same argument, one could also proclaim the electron to be unstabile. Does that follow from any of the unified theories so far?

 

[chroot]

Terry and Antonio,

I split your last posts off into a new thread of the same title in the Theory Development subforum. That is where alternative or personal theories should be posted.

- Warren

 

[Mr. Robin Parsons]

Originally posted by chroot
Terry and Antonio,

I split your last posts off into a new thread of the same title in the Theory Development subforum. That is where alternative or personal theories should be posted.

- Warren

Who is "Terry and Antonio"?

 

[beacon]

Originally posted by suyver
Following the same argument, one could also proclaim the electron to be unstabile. Does that follow from any of the unified theories so far?

There is no any unified theories predicting the decaying of electrons, I think. LURCH's viewpoint is very interesting. Can anyone explain this?

 

[Nereid]

Originally posted by Mr. Robin Parsons
Who is "Terry and Antonio"?

Terry Giblin and Antonio Lao. Their posts - one of each - can be found in Theory Development, in a thread called "Proton: stable or unstable"

 

[Haelfix]

Assuming conservation of baryon number is a good quantum number in the universe and quarks are subject to confinement, the proton in this ground state can't decay or give off energy. It would be 'stable'.

Statistical mechanics applies of course, but ask yourself, what else can it decay too? Theres no other mode. Its stuck in that configuration essentially forever.

 

[Mr. Robin Parsons]

Originally posted by Nereid
Terry Giblin and Antonio Lao. Their posts - one of each - can be found in Theory Development, in a thread called "Proton: stable or unstable"

Thanks! found it sort of strange as I didn't see there names attached to, or in, any posts in here (this thread)...

 

[suyver]

Originally posted by beacon
There is no any unified theories predicting the decaying of electrons, I think. LURCH's viewpoint is very interesting. Can anyone explain this?

I also have never heard of it. I'd be most interested in hearing more from LURCH's argument.

 

[chroot]

MRP:

I have split off your questions and comments about electrons and generators to a new thread, entitled "Generators and Electrons" in the Theory Development subforum.

- Warren

 

[selfAdjoint]

Jackiw, in his Yang-Mills retrospective says

‘tHooft concluded that baryon number is not conserved in the standard
model. By evaluating the Euclidean functional integral in a Gaussian approximation around
the instanton solution of Belavin et al., he calculated the baryon lifetime. Fortunately it is
exponentially small, but diamonds in principle are not forever

 

[kurious]

The particle which causes proton decay may be antimatter that decayed in the early universe along with all the other antimatter that's missing.

 

[Antonio Lao]

Proton decay is a prediction of the grand unified theories. These are theories that attempt to unify the electroweak force and the strong force of particles and fields in quantum field theories. These theories assert that since quarks are heavier than leptons, quarks should ultimately decay into leptons. The theories have nothing to say about the involvement of antimatter.

The mystery of the asymmetry of matter-antimatter remains to be resolved. At the present time, no such a theory of resolution exist.

 

[kurious]

The mystery of the asymmetry of matter-antimatter remains to be resolved. At the present time, no such a theory of resolution exist.

What if matter and antimatter have slightly different masses which in the conditions of the big bang meant that antimatter was split into tiny fragments which fill all of space whereas matter survived.

 

[suyver]

What if matter and antimatter have slightly different masses

I think that would violate the CPT-theorem... That would be bad news.

 

[Antonio Lao]

In order not to violate the CPT Theorem, the antimatter must be found dominantly in a universe by themselves and this anti-universe is connected to ours at various time-zero points which we call the vacuum. The phenomena of vacuum fluctuation is a direct proof that this is what is actually happening.

 

[kurious]

Does this mean that antimatter could be all around us?

 

[Antonio Lao]

We are surrounded by air but antimatter are in the vacuum and it is stabilized by the existence of virtual photons. If we by accident touch any of the antimatter, we will be turned into pure energy. Then there is also the question of dimension. We are basically four dimensional beings. The vacuum is zero dimensional. To "reach" the vacuum, we must contract our dimension from 4 to 3, from 3 to 2, from 2 to 1, from 1 to 0. Each of these steps is controlled by a force. EM force (4 to 3), Weak force (3 to 2), strong force (2 to 1), gravity (1 to 0).

 

[chroot]

kurious,

Yes, antimatter particles spring into existence everywhere, all the time, and promptly annihilate with the matter particles that sprung into existence at the same time. When particles are created, they are always created in pairs -- one normal matter, one anti-matter. There's a good chance that your body has encountered at least one anti-matter particle sometime in your lifetime, created by interactions between the atmosphere and a cosmic ray.

Antonio,

You were making good sense up until your "contract our dimensions" business.

- Warren

 

[Mr. Robin Parsons]

kurious,

Yes, antimatter particles spring into existence everywhere, all the time, and promptly annihilate with the matter particles that sprung into existence at the same time. When particles are created, they are always created in pairs -- one normal matter, one anti-matter. There's a good chance that your body has encountered at least one anti-matter particle sometime in your lifetime, created by interactions between the atmosphere and a cosmic ray.

Antonio,

You were making good sense up until your "contract our dimensions" business.

- Warren

So were you, till the 1^stemboldened, not quite...

 

[chroot]

How did I fail to make sense?

- Warren

 

[kurious]

The vacuum must have a temperature equal to the temperature of the matter in its neighbourhood or else I reckon all rest mass would decay.
I reckon you're right and the vacuum has entropy too.I estimate that to reach a temperature of 10 to the power of 32 K - the temperature at the time of the big bang- the universe must have had a radius of 10 ^ 16 metres.
Far larger than is currently thought.

 

[Mr. Robin Parsons]

If it was "all the time" wouldn't it be eminently detectable and wouldn't the universe be doing nothing but...?

EDIT could just be me not 'seeing it' properly, as well, so don't take it as a criticism please, more like a quest for better info...

 

[Antonio Lao]

chroot,

I am still working on my sense. I start from being crazy then thru self-psychoanalysis, I hope to arrive at being normal when at a ripe old age.

 

[chroot]

MRP:

It *is* all the time, and it *is* eminently detectable.

- Warren

 

[Mr. Robin Parsons]

The prepoderance of antimatter anihilations has been detected, and proven, as all the time, everywhere?

Hummm, you would wonder what/why I would question?

 

[garytse86]

you can say that a proton is not stable chemically, that's why you get h30+ ions, the proton is not going to sit in solution doing nothing

 

[chroot]

gary:

Compounds of hydrogen have nothing to do with the stability of the proton itself.

- Warren

 

[Mr. Robin Parsons]

But I would be curious to know if, in separating protons from their respective electrons, by ionizational energies, (then a magnet to evacuate the protons), if placed back into an ionizing chamber, then turning the ionizing energy off, will the electrons that were once there, re-appear, from the energy that the ionization process imparted?

 

[chroot]

If you separate electrons from protons, you have a box of electrons and a box of protons. You can't destroy electrons, nor can you create them.

- Warren

 

[garytse86]

yes but in an acid, you don't get H+ ions but H30+ ions instead

 

[Terry Giblin]

Where did all the electrons disappear too?

If you separate electrons from protons, you have a box of electrons and a box of protons. You can't destroy electrons, nor can you create them.

- Warren

Warren,

Assuming you now have a box of electrons, and the walls of the box, act as a square-square potential well - quantum barrier which we can control, to release only one single electron at a 'time'.

Now we build two concentric circular walls around the box, the inner wall has two slits in it and the outter wall is painted white.

How did the electrons tunnel throught the wall?

Where do all the electrons disappear too?

Where did all the photons appear from and how?

I can only see a intereference wave pattern, but no electrons?

"You can't destroy electrons" - or matter or energy only change its form.

Regards

Terry Giblin

 

[ahrkron]

yes but in an acid, you don't get H+ ions but H30+ ions instead

How is that relevant?

In a chemical reaction, by definition the number of protons do not change. Actually, even the number of protons in each nucleus is not altered.

 

[garytse86]

How is that relevant?

In a chemical reaction, by definition the number of protons do not change. Actually, even the number of protons in each nucleus is not altered.

yes but the proton is not chemically stable otherwise it would not form an ion with H2O.

 

[chroot]

We're not talking about "chemical stability," gary, for the last time.

- Warren

 

[chroot]

I have split off MRP's discussion of whether or not chemistry includes nuclear effects to the Theory Development subforum.

- Warren

 

[IooqXpooI]

Isn't a proton just a combination of quarks?

It is stable, yet turns into a Neutron by means of Weak Force quickly...(in the atom)

 

[Nereid]

Isn't a proton just a combination of quarks?

Yes.

It is stable, yet turns into a Neutron by means of Weak Force quickly...(in the atom)

I think you mean 'in a nucleus', and only in certain cases, e.g. where it can capture an orbital electron, and where the resulting nucleus has lower energy than the starting one, ...

 

[Mr. Robin Parsons]

And in radio-active decay, it reverts back to a proton, from a neutron by decay emitance of either, an electron, or a positron. (and a neutrino too, I suspect, I recall)

 

[chroot]

Beta decay:

n \rightarrow p + e^- + \overline{\nu}_e

- Warren

 

[Haelfix]

Note the inverse process is not a 'decay', its a reaction... One with very small cross section too I might add.

So the point stands, the proton has nothing to decay into... In nuclear and particle physics, any situation like that is defined to be 'stable'. Note this is not the same meaning as a chemist would use, where typically you aren't dealing with extreme vacuums.

You have to go beyond the SDM* to find a mechanism for its decay. (*aside from one technicality which has vanishingly small contribution)

 

[Antonio Lao]

What I don't understand is why the sum of the mass of the quarks composing the proton is larger than the mass of the proton.

Experimentally it can be said that the formation of proton liberates mass in term of energy because it takes about the same energy to form the jets which have proven the existence of quarks. But individual quark cannot be isolated. How much more energy does it takes to isolate the quark?

 

[Mr. Robin Parsons]

Have protons been created experimentally? or are you simply referring to the math's prediction(s)?

 

[Antonio Lao]

Experimental verification of quarks by the formation of jets proving the compositeness of nucleons and mesons of all hadrons.

 

[chroot]

What I don't understand is why the sum of the mass of the quarks composing the proton is larger than the mass of the proton.

You have it backward. The proton has more mass than the sum of its constituent quarks, because the binding energy between them counts as additional mass via E=mc².

How much more energy does it takes to isolate the quark?

You can't isolate quarks, because the energy required to pull two apart is more than the energy required to create two more. In other words, you can pull a pair apart to a point and then *pop* you'll wind up with two pairs.

- Warren

 

[Mr. Robin Parsons]

Uhmmm, this was the question I had asked: "Have protons been created experimentally?" Lord knows what question you answered...