Looking for charming asymmetries

September 29, 2016, CERN
A view of the LHCb experimental cavern. Credit: Maximilien Brice/CERN

One of the biggest challenges in physics is to understand why everything we see in our universe seems to be formed only of matter, whereas the Big Bang should have created equal amounts of matter and antimatter.

CERN's LHCb experiment is one of the best hopes for physicists looking to solve this longstanding mystery.

At the VIII International Workshop on Charm Physics , which took place in Bologna earlier this month, the LHCb Collaboration presented the most precise measurement to date of a phenomenon called Charge-Parity (CP) violation among particles that contain a charm quark.

CP symmetry states that laws of physics are the same if a particle is interchanged with its anti-particle (the "C" part) and if its spatial coordinates are inverted (P). The violation of this symmetry in the first few moments of the universe is one of the fundamental ingredients to explain the apparent cosmic imbalance in favour of matter.

Until now, the amount of CP violation detected among elementary particles can only explain a tiny fraction of the observed matter-antimatter asymmetry. Physicists are therefore extending their search in the quest to identify the source of the missing anti-matter.

The LHCb collaboration made a precise comparison between the decay lifetime of a particle called a D0 meson (formed by a charm quark and an up antiquark) and its anti-matter counterpart D-0 (formed by an charm antiquark and up quark), when decaying either to a pair of pions or a pair of kaons. Any difference in these lifetimes would provide strong evidence that an additional source of CP violation is at work. Although CP violation has been observed in processes involving numerous particles that contain b and s quarks, the effect is still unobserved in the charm-quark sector and its magnitude is predicted to be very small in the Standard Model.

Thanks to the excellent performance of CERN's Large Hadron Collider, for the first time the LHCb collaboration is accumulating a dataset large enough to access the required level of precision on CP-violating effects in charm-meson decays. The latest results indicate that the lifetimes of the D0 and D-0 particles, measured using their decays to pions or kaons, are still consistent, thereby demonstrating that any CP violation effect that is present must indeed be at a tiny level.

However, with many more analyses and data to come, LHCb is looking forward to delving even deeper into the possibility of CP violation in the charm sector and thus closing in on the universe's missing antimatter. "The unique capabilities of our experiment, and the huge production rate of charm mesons at the LHC, allow us to perform measurements that are far beyond the sensitivity of any previous facility," says Guy Wilkinson, spokesperson for the LHCb collaboration. "However, nature demands that we dig even deeper in order to uncover an effect. With the data still to come, we are confident of responding to this challenge," he adds.

Explore further: Charming surprise: First evidence for CP violation in charm decays

More information: More information is available on the LHCb website: lhcb-public.web.cern.ch/lhcb-p … lcome.html#Charm2016

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Hyperfuzzy
1 / 5 (2) Sep 29, 2016
First: Matter is made of two diametrical spherical fields; therefore, two scenarios for orbiters. If matter is made up of positive orbiters, stability exist if only positive orbiters. I'm talking about atomic orbiters. So, conceptually, we're OK, diametrically speaking. Anti-matter, MC^2 are Bull$h*t. Kwazy wabbit!
Seeker2
1 / 5 (1) Sep 30, 2016
"CP symmetry states that laws of physics are the same if a particle is interchanged with its anti-particle (the "C" part) and if its spatial coordinates are inverted (P). The violation of this symmetry in the first few moments of the universe is one of the fundamental ingredients to explain the apparent cosmic imbalance in favour of matter"

If space is more or less symmetric, why wouldn't time be? We're matter and space appears to be expanding all around us. But if you're antimatter and travelling in reverse time, space is disappearing all around you. Which means you were pretty well left out at the big bang. Or so it seems anyway.
Urgelt
1 / 5 (1) Sep 30, 2016
Seeker2, the notion that antimatter moves backward in time is a conjecture, not accepted physics. There's no proof.
antialias_physorg
5 / 5 (2) Sep 30, 2016
But if you're antimatter and travelling in reverse time

If antimatter were to go backwards in time it would show CPT symmetry - not CP symmetry. Since it doesn't that idea is a non-starter.

Just because something has "anti" in the name doesn't mean it has to be opposite to everything.
Seeker2
1 / 5 (1) Sep 30, 2016
Seeker2, the notion that antimatter moves backward in time is a conjecture, not accepted physics. There's no proof.
Right. I only bring it up because it answers the question.
Seeker2
1 / 5 (1) Sep 30, 2016
If antimatter were to go backwards in time it would show CPT symmetry - not CP symmetry...
Good point. Urgelt, it looks like here is the proof you're looking for. See https://en.wikipe...symmetry
Urgelt
1 / 5 (1) Sep 30, 2016

Seeker2, that isn't proof, it's conjecture. CPT theory is a mathematical construction. Proof of movement through time in reverse for antimatter requires evidence that doesn't exist. And that isn't the only part of CPT theory that lacks evidence to back it up, either.

Absent evidence, the conjecture persuades some physicists. Others are skeptical. There is no consensus.

Reverse time travel for antimatter falls into the category of 'cool idea, it will be neat if it's true.'

I count myself among the skeptics - though I am not a physicist, and my vote doesn't count. Why? It seems to me that if CPT were valid, we would be looking for bosons that also travel backwards. Anti-bosons, in other words. (Otherwise, backwards-traveling antimatter would be lonely. :P) Nobody is looking for backwards-traveling bosons, so far as I have read. It's not a thing in physics.
Urgelt
1 / 5 (1) Sep 30, 2016
Seeker2, one more point. CPT theory isn't fully explored. For example, what should happen when backwards-traveling antimatter particles interact with forward-traveling bosons? What should we expect to see that we would not see with bosons striking matter particles?

We have seen nothing in collider physics that hints of strangeness in boson-antimatter interactions. Hit an antimatter atom with a photon of the right frequency and the positron jumps up an orbit just like an electron would. The interactions appear to proceed in the same time direction.

Gigantic assertions of 'truth' require gigantic amounts of evidence to be declared 'true.' (Thanks, Carl Sagan.) That evidence does not exist for this conjecture. Backwards-traveling antimatter is just exactly like multiple universes theories. They're cool ideas. We have no evidence to suggest that they are describing our reality.

Math can describe any physics. The question is, which math describes ours?
Urgelt
1 / 5 (1) Sep 30, 2016
Antialias wrote, "Just because something has "anti" in the name doesn't mean it has to be opposite to everything."

Um, so, antialias is not necessarily the opposite of an alias...?

Your MOM named you that?

Oh, you poor thing. :P
Seeker2
1 / 5 (1) Sep 30, 2016
Absent evidence, the conjecture persuades some physicists.
Absent evidence the conjecture persuades no physicists I know of. Check https://en.wikipe...ymmetry.
Seeker2
1 / 5 (1) Sep 30, 2016
Seeker2, one more point. CPT theory isn't fully explored. For example, what should happen when backwards-traveling antimatter particles interact with forward-traveling bosons?
Photons are their own antiparticle. Shifted 180 degrees in phase angle I presume.
Seeker2
1 / 5 (1) Sep 30, 2016
Gigantic assertions of 'truth' require gigantic amounts of evidence to be declared 'true.' (Thanks, Carl Sagan.)
Probably useless folly to be declaring anything absolutely true. We can only find explanations.
Seeker2
1 / 5 (1) Sep 30, 2016
Photons are their own antiparticle. Shifted 180 degrees in phase angle I presume.
Not really, Photons are their own antiparticle because they do not travel in time. Otherwise they would be conflicted.
Urgelt
1 / 5 (1) Sep 30, 2016
Um, Seeker2, why are you arguing with yourself? How many users are on that account, anyway?

You wrote, "Photons are their own antiparticle. Shifted 180 degrees in phase angle I presume."

No. Photons do not annihilate each other. They are not antiparticles to themselves, no matter the phase. (Cancellation is not annihilation.)

Then you wrote, answering your own post, "Not really, Photons are their own antiparticle because they do not travel in time. Otherwise they would be conflicted."

No. Photons are timeless in their own frame of reference, but that's not to say that they do not travel in time. They do; and we know how fast they do it, and in which time direction.

Amazing. You took two opposite positions arguing against each other, and they're both wrong. I think you set a new record for brain farts on Phys.org.
Hyperfuzzy
1 / 5 (2) Sep 30, 2016
Really guys, we're supposed to be thinkers. When atomic physics came onto the scene, you do realize even the best made stupid conjecture such as anti-matter from cosmic particles and Dirac. What was observed was a particle in the wrong regime. The idea of mass is an understandable error. Mass from gravity an gravity from the number of charge pairs. All the BS is over something that does not exist! Imagine the RF from a very fast moving charge, mix very tight fast orbits and high speed particles. I would think annihilation also. But someone has to inspect the remnants.
Hyperfuzzy
1 / 5 (2) Sep 30, 2016
Something that really bothers me is particles. Has anybody an axiomatic structure for particles. I can't find any fundamental and elemental particles and certainly not a single particle of charge. Only the field. So why do we give Nobels for particle physics with no axiomatic structure but supply proof with the field, duh?

Oh well, planet of fools. Who's running this ship, anyway?
Hyperfuzzy
1 / 5 (2) Sep 30, 2016
Look, charge! Charge is the entire field, from it's center to infinity, fixed relative to the center. Only motion through the field, and conglomerations create something. Since they are diametrical, I dare you to define this universe without motion. As for charming asymmetries, WTF are we talking about? Asymmetrical thinking?

Note the field is updated relative to the observed center at the speed of light, any observer. But please don't get confused like Einstein. Always start with the initial conditions and not some assumption.
Hyperfuzzy
1 / 5 (2) Sep 30, 2016
It does not matter what is done or defined at CERN. Charge is all there is, never created nor destroyed, measurable, definable, but poorly understood. The misunderstanding is obvious, logically, we seek a definition relative to our composite thinking, or our worldly knowledge of space, time, gravity, explosions, collisions, etc.. Truth is not there. Each charge is still there, waiting for an acknowledgement. The field is continuous and relative and superposition applies everywhere. It's a lot simpler than anything you will learn in a PhD program in theoretical physics.
Phys1
5 / 5 (1) Sep 30, 2016
@Seeker2
Photons are their own antiparticle. Shifted 180 degrees in phase angle I presume.

That is 100% correct.
Phys1
5 / 5 (1) Sep 30, 2016
Seeker2, the notion that antimatter moves backward in time is a conjecture, not accepted physics. There's no proof.

"Antimatter travels backward in time" is not a scientific statement.
If you invert charge (C), time (T) and space ℗ the QED equations say that everything look the same. If you only do CP inversion then a particle will appear like its antiparticle travelling in the opposite direction. That is what is meant.
Hyperfuzzy
1 / 5 (2) Sep 30, 2016
@Seeker2
Photons are their own antiparticle. Shifted 180 degrees in phase angle I presume.

That is 100% correct.

Think about it, the field is proportional to 1/r^2, now define it as a particle. No wait, it's an entire sphere, no wait, its an entire volume, no, it's everywhere and updated at the speed of light relative to its center. This is a no brainer, not particulate. Note Einstein defined everything as corpuscular, i.e. his dissertation, add the slit experiment and expect particles to be different from waves. No particles.
Hyperfuzzy
1 / 5 (2) Sep 30, 2016
Photons? Stop blowing smoke up your own ...
Hyperfuzzy
1 / 5 (2) Sep 30, 2016
Seeker2, the notion that antimatter moves backward in time is a conjecture, not accepted physics. There's no proof.

"Antimatter travels backward in time" is not a scientific statement.
If you invert charge (C), time (T) and space ℗ the QED equations say that everything look the same. If you only do CP inversion then a particle will appear like its antiparticle travelling in the opposite direction. That is what is meant.

BS defined by BS is still BS.
Seeker2
3 / 5 (2) Sep 30, 2016
"Antimatter travels backward in time" is not a scientific statement.
Here's one that is - Per http://phys.org/n...big.html "the theories of physics work equally well going forward or backward in time."
Seeker2
1 / 5 (1) Oct 01, 2016
Could this be a scientific statement from the same source? "from Aristotle and Augustine to Paul Dirac – the discoverer of antimatter, which can be thought of as normal matter moving backward in time"
Seeker2
1 / 5 (1) Oct 01, 2016
Also from the same source - "the creation of time might be discernible during the rapid cosmic inflation that took place just after the Big Bang, when space and time expanded much, much faster than today." Time expanding just like space? Could it be? When something expands does it expand in one direction only? Like there's a big wall out there telling time not to expand in the reverse direction. I don't buy it.
Urgelt
1 / 5 (1) Oct 01, 2016
When Seeker wrote, "Photons are their own antiparticle. Shifted 180 degrees in phase angle I presume...", Phys1 answered, "That is 100% correct."

It is, if you confuse cancellation with annihilation.

Don't confuse them.

Antiparticle is a term which applies to fermions, not bosons. One of the CERN physicists came out of his cave in 2012 long enough to explain it to the ignorati:

http://www.abc.ne...7034.htm

Don't forget, the Pauli exclusion principle does not apply to bosons. They do not collide. They do not annihilate.

There is a convention, not rigorously observed, among physicists to say that bosons are their own antiparticles, but this doesn't mean that bosons manifest as bosons and antibosons. It means that bosons are bosons, period.
Seeker2
1 / 5 (1) Oct 01, 2016
When Seeker wrote, "Photons are their own antiparticle. Shifted 180 degrees in phase angle I presume...", Phys1 answered, "That is 100% correct."

It is, if you confuse cancellation with annihilation.
Since photons are their own antiparticle, they can't annihilate. I wouldn't worry about anything which is its own antiparticle annihilating another similar particle. Similar particles just don't annihilate.
Urgelt
1 / 5 (1) Oct 01, 2016
For those of you who like to parrot the phrase 'bosons are their own antiparticle' and also champion the idea that 'antimatter travels through time in the opposite direction from matter,' please do explain if you think that bosons - some of them - travel through time in the opposite direction from other bosons. Or explain why you think they do not. Either explanation will be fascinating to hear.
Seeker2
1 / 5 (1) Oct 02, 2016
For those of you who like to parrot the phrase 'bosons are their own antiparticle' and also champion the idea that 'antimatter travels through time in the opposite direction from matter,' please do explain if you think that bosons - some of them - travel through time in the opposite direction from other bosons. Or explain why you think they do not. Either explanation will be fascinating to hear.
I don't think they travel through time. E.g. the photon. If it did which way would it travel? Hitch a ride on a photon and you can go anywhere instantly, as far as the photon's time is concerned.
Phys1
5 / 5 (1) Oct 02, 2016
When Seeker wrote, "Photons are their own antiparticle. Shifted 180 degrees in phase angle I presume...", Phys1 answered, "That is 100% correct."
It is, if you confuse cancellation with annihilation.

Two high energy photons can annihilate by inverse electron-positron annihilation.
https://en.wikipe...reaction

Antiparticle is a term which applies to fermions, not bosons.

Pions are bosons and they have antiparticles. Klein-Gordons equation, for bosons, predicts these as well.
One of the CERN physicists

Interesting link, he is talking about "elementary bosons" meaning not consisting of quarks-which are fermions. The photon example shows that his pov is incorrect.
Don't forget, the Pauli exclusion principle does not apply to bosons.

They obey boson statistics, so they are correlated.
They do not collide.

W bosons would mutually collide if they existed long enough
Phys1
5 / 5 (1) Oct 02, 2016
_Charged_ W bosons would mutually collide if they existed long enough.
Phys1
5 / 5 (1) Oct 02, 2016
Here's one that is - Per http://phys.org/n...big.html "the theories of physics work equally well going forward or backward in time."

Agreed.
Could this be a scientific statement from the same source? "from Aristotle and Augustine to Paul Dirac – the discoverer of antimatter, which can be thought of as normal matter moving backward in time"

That is stating that under CT inversion particles turn into antiparticles with reversed momentum, but interpreted for laymen. The interpretation makes it less scientific in my opinion.
Phys1
5 / 5 (1) Oct 02, 2016
Seeker2, the notion that antimatter moves backward in time is a conjecture, not accepted physics. There's no proof.

It is popularisation.
Positrons are considered antimatter and move forward in time.
Phys1
5 / 5 (1) Oct 02, 2016
For those of you who like to parrot the phrase 'bosons are their own antiparticle'

Some are, some are not. The pi+ and pi- pions are each others antiparticles. pi0 is its own antiparticle. Same for W+/- and the uncharged Z. Same for photons.

btw photon-photon conversion into e-p pairs is a theoretical (but very sound) idea.
An experiment to measure this is apparently underway since May 2014:
http://phys.org/n...est.html
Phys1
5 / 5 (1) Oct 02, 2016
Since photons are their own antiparticle, they can't annihilate.

If the pair has enough energy (>1.22 MeV, e+p mass) it can annihilate.
I suspect that theoretically they could even annihilate into, massless, neutrino anti-neutrino pairs, that is at any energy, via a virtual Z boson as intermediate.
Phys1
5 / 5 (1) Oct 02, 2016
Urgelt
1 / 5 (1) Oct 02, 2016
The Pauli Exclusion Principle doesn't apply to photons, Phys1. They can't collide with each other. The Wikipedia article you cited isn't about photons colliding with photons, but with photons colliding with matter, which is an entirely different thing. High-energy photons colliding with matter will dump their energy and you can get a particle spray. There's no question that the energy they carry can be converted to matter in such collisions, but they can't do it on their own.

Photons dumping energy in collisions with matter are not annihilating each other. Annihilation is a completely different phenomenon - and it only applies to antimatter meeting matter.

You can set up an experiment where photons collide with matter, producing a spray of matter and antimatter particles which can then annihilate. But that is not the same thing as saying that photons can collide with one another and annihilate.
Urgelt
1 / 5 (2) Oct 02, 2016
Think longer and harder about what physicists are attempting to tell us when they say 'bosons are their own antiparticles.' It does not mean what you think.

It means that bosons are bosons. That's really all it means. There is no particle dichotomy involving opposite charges, and they do not annihilate one another in collisions, since collisions between bosons don't happen.

There is no such thing as an anti-photon.
Phys1
5 / 5 (1) Oct 02, 2016
The Pauli Exclusion Principle doesn't apply to photons, Phys1.

Tell me something new.
They can't collide with each other. The Wikipedia article you cited isn't about photons colliding with photons, but with photons colliding with matter,

Breit-Wheeler is about photon-photon annihilation. You should read
https://en.wikipe..._process
There is no such thing as an anti-photon.

There is. It is a photon. Under the right conditions two photons can annihilate: Breit-Wheeler. Just the reverse of positron-electron annihilation.

Believe what you want. I am just stating the publicly known facts.
Urgelt
1 / 5 (1) Oct 02, 2016
You are again confusing conjecture with verified experimental evidence.

Quoting from the article: "As of January 2016, Brett Wheeler pair production hasn't yet been achieved in the laboratory."

They have an experiment. They are deriving data from it. They are interpreting the data using Monte-Carlo simulations. The authors *think* they know what's happening. But a lot of work will be required to prove that photons can obey the Pauli Exclusion Principle. That's a big claim, and it will require a lot more evidence than they've thus far amassed.
Phys1
5 / 5 (1) Oct 02, 2016
@Urgelt
You are confusing me with someone else.
Btw you are shifting.
First you said photons do not annihilate, now you say I have no "verified evidence".
I did not say I had. You read the links that _I_ provided.
Time reversed positron-electron annihilation is not a "conjecture" but a consequence of time reversal symmetry. QED's predictions have always been verified with sometimes stunning accuracy.
The question is not "if" but "when" Breit-Wheeler pair production will be observed.

Btw there is strong exp[erimental evidence of it:
"However, in 1997, researchers at the Stanford Linear Accelerator Centre were able to conduct the so-called multi-photon Breit–Wheeler process using electrons to first create high-energy photons, which then underwent multiple collisions to produce electrons and positrons, all within same chamber."
Hyperfuzzy
1 / 5 (2) Oct 02, 2016
When do we realize truth from bull$hit. It's not there!
RealityCheck
1 / 5 (3) Oct 02, 2016
Hi Phys1, Urgelt, everyone. :)

IF we realize that it's all boils down to just "energy-space" perturbations/features which concentrate Energy quantity either transiently (ie lightspeed moving perturbations/features) or persistently (ie slower moving perturbations/features), THEN we can realize that all these 'collisions' (whether in LHC scenario OR in Breit-Wheeler scenario) are actually processes which 'coincide' sufficient energy in the relevant co-moving energy-space "event center location!

Hence we get LHC concentrating sufficient energy to produce quark-gluon plasma 'fluid' and 'jets' which reform whatever transient/persistent energy-space perturbations/features are eventually detected.

Similarly, the Breit-Wheeler hypothesis/scenario merely brings together sufficient energy in the energy-space 'event centre location' from which exits whatever transient/persistent 'products' that such energy quanta can form into.

CONTINUED...
RealityCheck
1 / 5 (3) Oct 02, 2016
CONTINUED... @ Phys1, Urgelt, everyone:

It makes no difference where from or in what form the requisite energy quotient comes (in LHC case it is from E-Magnetic field 'coils' acceleration forces; in Breit_Wheeler case its from Laser E-M field 'photonic' radiation acceleration forces).

The following observation is directed to Phys1 in prticular, re his quoted excerpt:
"which then underwent multiple collisions to produce electrons and positrons, all within same chamber."
Since the "hohlraum" is a "tiny gold can", it might be instructive to consider what the phrase "multiple collisions" actually means. For example, does it mean:

1) "multiple collisions" of photons "ONLY between themselves"?...OR

2) photons unavoidably having "multiple collisions" involving the tiny gold can (hohlraum) WALLS?

Further clarification from proponents of the Breit-Wheeler 'mechanism' would help minimize misunderstandings re actual "collision participants" involved. :)
Hyperfuzzy
1 / 5 (2) Oct 02, 2016
CONTINUED...

Further clarification from proponents of the Breit-Wheeler 'mechanism' would help minimize misunderstandings re actual "collision participants" involved. :)

So, never!
RealityCheck
1 / 5 (3) Oct 02, 2016
Hi again Phys1, Urgelt, everyone. :)

Further to my above two posts, you might be interested to know avout another related but more recent mechanism/experiment worth further investigation/clarification for yourselves:

http://phys.org/n...ers.html

Cheers all. :)
Urgelt
1 / 5 (1) Oct 02, 2016
It seems to me that the source of confusion here is the difference between photonic decay (very high energy photons) and photonic collisions.

There is no evidence, and no accepted theory, for photonic collisions. And there is no evidence, and no accepted theory, for bosons obeying the Pauli Exclusion Principle.

Thanks for clarifying, RealityCheck.

Phys 1 wrote, "Btw you are shifting. First you said photons do not annihilate, now you say I have no "verified evidence".

I said both and I stand by both. Photons do not annihilate. And the evidence for bosons obeying the Pauli Exclusion Principle (e.g. they can collide) is lacking.
Phys1
not rated yet Oct 03, 2016
@Urgelt
There is no confusion, not on my side. I reiterate.
The reaction e+p --> ph+ph is annihilation and so is the reaction ph+ph --> e+p (Breit-Wheeler)

A photon can decay [into ep pairs] if a) it has enough energy and b) if another body is present. If that other body is _also a photon_ and if they then both disappear that is annihilation. The Breit-Wheeler process is known theoretically since 1932 as one of the sensational predictions of QED.

It is therefore justified to say that the photon is its own antiparticle.
Phys1
not rated yet Oct 03, 2016
And the evidence for bosons obeying the Pauli Exclusion Principle

They don't, they obey an analogous principle leading to Bose statistics.
(e.g. they can collide) is lacking.

Absence of evidence is not evidence of absence.

Btw the PEP as it is at this time is not an interaction.
It is the consequence of symmetry. That is the pov of theoretical physicists.
Electrons interact through EM, but are correlated through EM interaction _and_ PEP.
Urgelt
1 / 5 (1) Oct 03, 2016
Phys1 wrote, "The reaction e+p --> ph+ph is annihilation and so is the reaction ph+ph --> e+p (Breit-Wheeler)"

Annihilation is the complete conversion of matter to energy.

Both annihilation and high-energy photonic decay demonstrate E=MC^2, but that does not mean that decay is identical to annihilation. You're misusing the term.

The PEP doesn't apply to bosons, so far as our physics can determine. Bosons can't collide, and they can't annihilate.
Hyperfuzzy
1 / 5 (1) Oct 03, 2016
@Urgelt
There is no confusion, not on my side. I reiterate.
The reaction e+p --> ph+ph is annihilation and so is the reaction ph+ph --> e+p (Breit-Wheeler)

A photon can decay [into ep pairs] if a) it has enough energy and b) if another body is present. If that other body is _also a photon_ and if they then both disappear that is annihilation. The Breit-Wheeler process is known theoretically since 1932 as one of the sensational predictions of QED.

It is therefore justified to say that the photon is its own antiparticle.

No it's our insidious way of naming things!
Phys1
not rated yet Oct 03, 2016
Annihilation is the complete conversion of matter to energy.

All matter corresponds to energy even without any reaction or conversion, so this definition is not ok.
In QED annihilation means that a particle, massless or massive, ceases to exist in favour of other stuff.
In the Breit-Wheeler process you start with two photons and you end up with none.
Where are the photons? Their identities were annihilated. They go on as an electron positron pair.
Urgelt
1 / 5 (1) Oct 03, 2016
"...you start with two photons and you end up with none.
Where are the photons? Their identities were annihilated. They go on as an electron positron pair."

From the Encyclopedia Brittanica: https://www.brita...hilation

You are not using the term 'annihilated' as physicists use the term, but as the general public uses the word. Sloppy, Phys1.

Terms are rather important in science. Misusing them spreads confusion.

Again: photons can't collide. You can't 'annihilate' particles unless they can collide, converting matter into energy with complete efficiency. Photons *can* decay; it's a different term and refers to a different phenomenon in physics. Both illuminate E=MC^2,
Phys1
not rated yet Oct 03, 2016
No I am using it as a physicist does.
The EB is not a physics textbook.
Are you familiar with annihilation and creation operators?
Urgelt
1 / 5 (1) Oct 03, 2016
Vaguely. But Brittanica is just one of a zillion sources that say the same damn thing. And they *do* consult subject matter experts.

You are misusing the term 'annihilation.' The correct term for high-energy photons disintegrating into matter particles is 'decay.'

A single high-energy photon can probably decay into matter particles - no collision required. And they can't collide in the first place. Extending 'annihilation' to photons is not a proper use of a scientific term.
Phys1
not rated yet Oct 03, 2016

A single high-energy photon can probably decay into matter particles - no collision required.

Impossible. Forbidden by energy-momentum conservation.
You are not knowledgeable on the subject.
And they can't collide in the first place.

I never said they collide.
Extending 'annihilation' to photons is not a proper use of a scientific term.

You are not knowledgeable about QED and the creation/annihilation operator formalism so not competent to decide this.
Seeker2
1 / 5 (1) Oct 03, 2016
Seeker2, the notion that antimatter moves backward in time is a conjecture, not accepted physics. There's no proof.

It is popularisation.
Positrons are considered antimatter and move forward in time.
Feynman demonstrated positrons moving backward in time as they rotate in the opposite direction of electrons in a cyclotron.
Seeker2
1 / 5 (1) Oct 03, 2016
Extending 'annihilation' to photons is not a proper use of a scientific term.

The proper term is decay.
Seeker2
1 / 5 (1) Oct 03, 2016
See also https://en.wikipe..._process .
This reference talks about creation, not annihilation.
Seeker2
1 / 5 (1) Oct 03, 2016
Feynman demonstrated positrons moving backward in time as they rotate in the opposite direction of electrons in a cyclotron.
As I understand Feynman a particle moves from one point to another through all possible paths in spacetime and there is a non-zero probability amplitude that a particle can reverse direction in time.
Hyperfuzzy
1 / 5 (2) Oct 04, 2016
Feynman demonstrated positrons moving backward in time as they rotate in the opposite direction of electrons in a cyclotron.
As I understand Feynman a particle moves from one point to another through all possible paths in spacetime and there is a non-zero probability amplitude that a particle can reverse direction in time.

Give me a break, Feynman built diagrams but somehow forgot that all changing fields are the result of charge motion. Neutrinos are not particles, they are the change in the field due to the uncoupling of the proton and the electron. So if he wants to define diagrams maybe he should have applied the physics we know! i.e. QM does not define causality! Error in logic, lost in the woods.
Hyperfuzzy
1 / 5 (2) Oct 04, 2016
Is anyone aware of the fact that electrons and protons are never created or destroyed?
Urgelt
1 / 5 (1) Oct 04, 2016
Phys1 wrote, "You are not knowledgeable on the subject."

No argument there. I'm not a physicist.

"You are not knowledgeable about QED and the creation/annihilation operator formalism so not competent to decide this."

I'm deciding nothing. The terms as physicists use them are defined by physicists.

Physicists don't use the term 'annihilate' to describe the decay of high-energy photons into matter particles. They use the term 'annihilate' only to describe the conversion of matter and antimatter particles in collisions into photons.

Insisting that they use the term 'annihilate' the way Phys1 used it is cranky as hell.
Urgelt
1 / 5 (1) Oct 04, 2016
Seeker2 wrote, "As I understand Feynman a particle moves from one point to another through all possible paths in spacetime and there is a non-zero probability amplitude that a particle can reverse direction in time."

Yes. It's a hair-on-fire idea that may owe more to the incompleteness of our physics than to reality. Feynman's day job was generating hair-on-fire ideas. Brilliant fellow, but that doesn't mean that time reversal has been verified in experiments.

"Feynman demonstrated positrons moving backward in time as they rotate in the opposite direction of electrons in a cyclotron."

No. Opposite rotation can be explained entirely by the opposite charge of antiparticles guided by the cyclotron's electromagnetic field. They're *expected* to rotate in the opposite direction.

If they are going backwards in time, some other experimental evidence is required to show it. To date, that hasn't been done.
Seeker2
1 / 5 (1) Oct 04, 2016
Opposite rotation can be explained entirely by the opposite charge of antiparticles guided by the cyclotron's electromagnetic field. They're *expected* to rotate in the opposite direction.
Expected by Feynman for a reason. Why should nature create two different particles when one can do the job?
Seeker2
1 / 5 (1) Oct 04, 2016
Brilliant fellow, but that doesn't mean that time reversal has been verified in experiments.
Brilliant fellow just did verify his idea with the cyclotron experiment.
Urgelt
1 / 5 (1) Oct 04, 2016
"Why should nature create two different particles when one can do the job?"

Any question starting with 'Why should nature...' is unanswerable. The 'why' is mysterious.

Physics concerns itself with the 'what.' We can observe. We can theorize. We can know when our theories are getting closer when they make predictions that are borne out in experiments. But there's a lot we can't test with our technology. (Yet.)

"Brilliant fellow just did verify his idea with the cyclotron experiment."

Alas, no. Antiparticles obeying electromagnetic fields according to their charges are just antiparticles obeying electromagnetic fields. If you assume they travel *forward* in time, you expect them to do exactly what we observe. The question as to their time direction is unanswered.

We know very well that our theories concerning the 'what' are incomplete. As to the 'why,' there are no real answers.
Seeker2
1 / 5 (1) Oct 04, 2016
We know very well that our theories concerning the 'what' are incomplete. As to the 'why,' there are no real answers.
As to the why, it looks like because nature loves making fools out of physicists. Among others I presume.
Seeker2
1 / 5 (1) Oct 04, 2016
Antiparticles obeying electromagnetic fields according to their charges are just antiparticles obeying electromagnetic fields.
All particles obey e/m fields according to their charge. Obedience holds in reverse time as well as forward time for all physical laws.
Phys1
not rated yet Oct 04, 2016

Insisting that they use the term 'annihilate' the way Phys1 used it is cranky as hell.

When you don't know a subject you should tread with caution and modesty.
You didn't, so now you have to save face by aggression.
Urgelt
3 / 5 (2) Oct 04, 2016
"When you don't know a subject you should tread with caution and modesty."

Correct. I have admitted my limitations. I must rely on experts, and have done so.

Your real gripe is that I don't rely on you, an anonymous poster, as an expert. You present yourself as a physicist and make clear declarations that are laughable to anyone who pays attention to what the real experts are saying about the field.

Photon decay is not annihilation.

Your arguments mirror Donald Trump's tactics - when caught in an error, you double down and resort to your own aggression. It's amusing, really. You should know, even as a layperson, that you can't demonstrate the truth of a proposition in physics by smearing a speaker. You can only do it by showing evidence for your position, which you have failed to do.
Hyperfuzzy
1 / 5 (1) Oct 04, 2016
"When you don't know a subject you should tread with caution and modesty."


Nobody knows particle physics because particles don't exist only the fields. When a conglomeration of these spherical fields we see things because of the "fields" and we fill solids because of repulsion. Everybody is wrong. Maxwell, close, with no explanation why space is only these diametrical spherical fields. The later we must accept until we learn to measure things as they are and not measure things to fit our paradigm.
TheGhostofOtto1923
5 / 5 (1) Oct 04, 2016
Your arguments mirror Donald Trump's tactics - when caught in an error, you double down and resort to your own blah

https://youtu.be/vuegl6ob0Po

-I think politics is something the human race will grow out of. Emperor trump won't allow it and the machines will make it impossible like all crime.
Urgelt
3 / 5 (2) Oct 04, 2016
I'm no admirer of Hillary Clinton, Otto. She's a liar and she's corrupt as they come.

But on the despicable scale, Trump trumps even Clinton. Yikes.

Civilization will be smashed to smithereens before crime becomes impossible. I mean that literally, not rhetorically. We're headed for a crash. But even if that weren't true, machines will never make either politics or crime impossible. People will use them to perpetrate both.
Seeker2
1 / 5 (1) Oct 04, 2016
"Any question starting with 'Why should nature...' is unanswerable. The 'why' is mysterious.
Try Occam's razor. Maybe that would help.
Phys1
not rated yet Oct 04, 2016
make clear declarations that are laughable to anyone who pays attention to what the real experts are saying about the field.

You don't understand the real experts. You are not a physicist, just an acolyte. A layman, a target of popularisations.

Photon decay is not annihilation.

So positron decay would also not be annihilation.
when caught in an error,

In your dreams.
you double down

I don't. Photons are their own antiparticle and they annihilate. You had never heard of the Breit-Wheeler process until I told you about it. And I doubt that you understand any of it.
and resort to your own aggression.

I dare you to point out where I did such a thing.

In the mean time you resorting to insults, such as
cranky as hell
.
All without having a clue.
You are, objectively and by your own admission, a fake expert.
Phys1
not rated yet Oct 04, 2016
@Chess playing p[igeon
Read this explanation of an expert to a layman like you.
https://van.physi...?id=1153
Phys1
5 / 5 (1) Oct 04, 2016
Here is another discussion on the topic.
https://www.physi...2/page-2

"However, other neutral particles are their own antiparticles, such as photons, hypothetical gravitons, and some WIMPs."
https://en.wikipe...particle

You google more by yourself from here on.
RealityCheck
1 / 5 (2) Oct 04, 2016
Hi Seeker2, Urgelt, Phys1, all. :)

Let's take a moment to consider what "traveling backwards in TIME" actually means in a physical effects sense. If that was possible in physical reality, then we would see 'antiparticles' being 'un-formed'; that is, we should observe them 'disintegrating spontaneously' all the way back into the fundamental energy-space constituents from which they were 'formed' into said 'anti-particle'.

We don't see 'anti-protons' spontaneously 'un-form' all by themselves, do we?

No; we only see 'annihilation' between particle PAIRS (proton-antiproton etc).

Physical 'traveling backwards in time' would require MORE than just ANTI-DIRECTIONAL MOTION across energy-space; which is a SPATIAL dimensional action.

"TIME" is only a MATHEMATICAL abstraction "dimension".

Time 'travel' began as Science Fiction 'literary device'; later entrenched in popular/physicists 'psyche' during era of LSD etc 'experimentation'.

Time to reconnect with Reality. :)
Hyperfuzzy
1 / 5 (1) Oct 04, 2016
Using Experts to Validate a Theory that only the Experts suggest, is like saying that God exists 'cause the Bible said it was so! Who inspired the Bible? God! OK, let's continue.
Urgelt
1 / 5 (1) Oct 04, 2016
"So positron decay would also not be annihilation."

Correct. Positron decay is not annihilation.

*All* matter particles are thought to decay, though the time to decay can be exceedingly long for conventional particles like electrons and positrons. When they do decay, the term 'annihilation' is not used by physicists to refer to the event. The term 'decay' suffices.

Annihilation in physics refers very specifically to the complete conversion of matter and antimatter to energy through collision.

Now go back and rethink your absurd posts about annihilation.
Urgelt
1 / 5 (1) Oct 04, 2016
When physicists say 'a particle is its own antiparticle,' they are explaining that colliding two of those particles will *not* result in annihilation (conversion of matter to energy). You can smash them - you can smash anything - but you won't get 100% conversion of matter to energy.

The point is even more stark for bosons, which can't collide with each other and aren't matter to begin with. Bosons are on the wrong side of the equation E=MC^2 to be called matter.
Urgelt
1 / 5 (1) Oct 04, 2016
"You are, objectively and by your own admission, a fake expert."

No. By my own admission, objectively and otherwise, I'm presenting myself as a layman, an interested observer of the science of physics, and a conversationalist. In order to be considered a 'fake expert,' I would have to do what you do: you refuse to admit your inexpertise and you present yourself as a physicist, which you are not.

"I dare you to point out where I did such a thing."

You did it in that very same post. You accused me of presenting myself as a 'fake expert.' I have done no such thing. It's an ad hominem attack. Your tone is dismissive, condescending and irritable, which is really quite amusing in light of the absurdity of your misunderstanding of the term 'annihilation' and your determination to apply it to bosons, which no sane layman, let alone physicist, would attempt.
Urgelt
1 / 5 (1) Oct 04, 2016
Reality Check, I'd like to amplify your point. Anti-particles conform to guiding electromagnetic fields in 4 dimensions, not three. There is no motion without the time dimension. Everything we see in 4 dimensions fits perfectly well with the conjecture that they move through time and the other 3 dimensions as if they are moving forward in time.

We have also not seen any hint of backwards-moving particles of any sort in any experiments, though it might also be said that we haven't devised any experiments that could robustly test this.

Regarding your point about time being a mathematical abstraction, it is, as it is treated in physics. But I still see it as a dimension, albeit one unlike the physical dimensions. The past stretches back; we can observe its reality, and do, every day. The future is not yet arrived, yet we can know things about that, too, such as Jupiter's position relative to us or the sun in three dimensions on March 31, 2022.
Urgelt
1 / 5 (1) Oct 04, 2016
Time is a measurable dimension, which is why we are striving for greater precision clocks to measure it and why we make appointments to see the dentist. The science fiction conceit about traveling backward in time - since it's a dimension, why not? - stumbles badly when it comes to a realistic scientific approach to making it happen. I don't think it's possible, myself.

I don't worry much about paradoxes; a paradox only exists when we make false assumptions. They do not occur in nature. (Zeno's paradox was formulated specifically to demonstrate this viewpoint.)

But I do worry about the nature of time.

Members of my family are long dead. Do they still exist earlier in the time dimension? Are they as real as those we regard as living now? Do those questions even have any meaning to physicists?

Heck if I know.
RealityCheck
1 / 5 (2) Oct 04, 2016
Hi Urgelt. :)

I appreciate your understanding of my point insofar as 'abstract' mathematical 'time' dimension is concerned. However you may still be influenced by metaphysical 'notions' about 'time' which crept into the physics construct a hundred years ago as if 'time' was a physical thing in its own right like space.

Recent rethinks in the physics constructs have realized that it is only MOTION/EVOLUTION of 'state' within SPACE that 'exists' in its own right....irrespective of whether we 'time' any of it or not using comparison 'standards' as conventionally implemented via CLOCK processes.

Actually, it's comparing between phenomena under study and CLOCKING phenomena 'standard' that is going on when we think of 'time dimension' in mathematical/geometrical ABSTRACT ANALYTICAL constructs.

We merely COMPARE TIMING RATES (observed rate in relativity to some standard rate) of MOTION/EVOLUTION in 3-D energy-space. So it's abstract analytical TIMING; not TIME per se. Cheers. :)
Seeker2
not rated yet Oct 05, 2016
We don't see 'anti-protons' spontaneously 'un-form' all by themselves, do we?
No. Feynman used to belabor this point, talking about mechanical clocks running backwards in forward time. Reverse time just doesn't exist. Don't worry about going backwards in time and killing your grandfather. Time expands in opposite directions just like space. We're just not going to reverse spatial expansion and similarly time. Anti-protons can continue existing as long as time is running in the opposite direction. Time will be running in the opposite direction as long as it's running in the forward direction, that is, as long as spacetime is expanding. When the dark force runs out and the temperature of the U falls to absolute zero, spacetime pops like a balloon and collapses into it's next BB phase. Or so it seems.
Phys1
5 / 5 (2) Oct 05, 2016
"You are, objectively and by your own admission, a fake expert."

No. By my own admission, objectively and otherwise, I'm presenting myself as a layman, an interested observer of the science of physics, and a conversationalist.

You make statements on physics for which you do not have the expertise. Some are wrong, some are debatable to say the least.
you refuse to admit your inexpertise

I have expertise.
and you present yourself as a physicist, which you are not.

This statement just confirms that you are a poser unable to distinguish an actual physicist.
"I dare you to point out where I did such a thing."
You did it in that very same post.

1) Your mala fide accusation dated from _just_ before that post.
2) You really are a fake expert. It is not an insult, but a fact.

You are a poser playing the second hand physicist using big words that you don't understand. Nobody should listen to someone like you.
Urgelt
not rated yet Oct 05, 2016
"We merely COMPARE TIMING RATES (observed rate in relativity to some standard rate) of MOTION/EVOLUTION in 3-D energy-space. So it's abstract analytical TIMING; not TIME per se."

You can't account for motion of any sort in 3-D energy space. You need 4 dimensions: 3 physical + 1 odd one.

"However you may still be influenced by metaphysical 'notions' about 'time' which crept into the physics construct a hundred years ago as if 'time' was a physical thing in its own right like space."

Guilty as charged.

I don't feel bad about that, RealityCheck. Thus far no-one in physics has stepped up to say 'Oh! Now we understand what the hell this is." It's as mysterious as it ever was. What I see happening today is a kind of retrenchment, as if saying 'let's not get carried away with conclusions we can't support, so we'll talk about this using minimalist interpretations of the math."

Very smart. But it isn't an answer.
Urgelt
not rated yet Oct 05, 2016
Phys1 descended from Olympus to hurl his godly wrath by saying, "Nobody should listen to someone like you."

Nobody should take me as an authoritative source for the truth about science.

Nobody should take *any* anonymous poster on the internet as an authoritative source for the truth about science.

As to whether anyone should listen to me...

In science, the validity of a point doesn't arise from who speaks it. So when I say things that are accurate, then I'm a valid conversationalist; or if I admit I don't understand and ask for clarification, then I'm a valid conversationalist. Only if I insist, against all reason and evidence, that a false thing is true have I disqualified myself from conversation.

Those rules apply to you, too. You can demand respect for your authoritative position, but you won't get it here. You're *anonymous.* No credentials.

When you go off the rails and insist on a falsehood, expect someone here to call you on it.

Bye-bye.
TheGhostofOtto1923
not rated yet Oct 05, 2016

But on the despicable scale, Trump trumps even Clinton. Yikes.
This depends entirely on whatever news feed you prefer. Which is exactly why politics is doomed. People are getting SICK of being manipulated, which is perhaps why this cycle is particularly foul.

And without politics democracy cannot survive. Yay.
Phys1
5 / 5 (1) Oct 05, 2016
Phys1 descended from Olympus to hurl his godly wrath by saying, "Nobody should listen to someone like you."

Bye-bye.

In matters of physics, compared to you, it may seem as if I live on the Olympus.
But is not a solitary peak, it is just a different level.
Years of study and experience in research, as well as development and engineering, a publications list, does that to a person.
On the other hand, you are unexplored territory where you have to rely on popularisations. It is therefore a mystery why you resort to insults. And stop lying.
RealityCheck
1 / 5 (1) Oct 05, 2016
Hi Urgelt, Phys1. :)

Guys, there is no need to be so adversarial. Scientific Intellects can discuss/disagree and still remain cordial and objective. Neither of you is 'always right', yes? So please don't let this be the beginning of yet another 'personal feud' which only demeans intellect, science, humanity.

@Urgelt:
You can't account for motion of any sort in 3-D energy space. You need 4 dimensions: 3 physical + 1 odd one.
That is yet another of the many 'metaphysical notions' about 'time' (actually 'timing', as I explained) that are still pervading/contaminating physics 'understandings'. CONSIDER: Our "accounting" of motion is maths analysis, not physical action. Nature does it whether we "account for it" or not; because 3-D REAL 'energy-space' is Natural Physical Construct; whereas the UNREAL 4-D 'time-space' is a NON-Natural ABSTRACT construct of our maths/geometry. Moreover, it's 4-D 'time-space' construct that has 'no motion in it' (ie, it covers 'all times'. :)

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