When asking a ``why'' question it's essential to spell out what is assumed to be known and what is sought for. The answer is that's what experiment shows. There's no particular reason, due to symmetry, for neutrinos to be only left-handed. It's a property of Nature and what matters is to describe its consequences in a mathematically consistent way.

That neutrinos are left-handed doesn't have anything to do with the fact that they don't carry electric charge (they do carry weak charge). It does have to do with the fact that, while they're massive, their mass can't be described by a Dirac type mass term. For the moment this isn't completely excluded, just very unlikely (since the mass would have to be so small as to evade the experimental limits on beta-decay, for instance). So it is much more likely, though not, yet, conclusively settled experimentally, that their mass is described by another mechanism. The so-called ``seesaw mechanism'', cf. https://indico.cern.ch/event/1047959/attachments/2302196/3916167/a_vicente.pdf for a review, is one way of describing their masses. There are many varieties and experiments that can distinguish between them are very hard.

That they don't carry electric charge simply means that they don't couple directly to the electromagnetic field.

It is known how to describe their properties in considerable detail, cf. Article On the Properties of Neutrinos

My research shows that handeness variation is affected by the charge. Elementary fermions (i.e. spin - 1/2) without charge are stuck only with one type. either left handed or right and I can explain also why this is so?

Also neutrinos are IMO not dark matter particles since they have a tiny intrinsic magnetic dipole moment.

The first statement is incorrect; fermions that do not carry electric charge, are not, necessarily, chiral. It suffices to write down the free action for a spin-1/2 fermion, which can be massive, so the mass term breaks chiral symmetry. It is also possible to couple fermions to gauge fields that are not electromagnetic in a way consistent with chiral symmetry. Coupling spin-1/2 fermions to gauge fields does not eliminate one chirality.

Nobody's claimed that neutrinos are dark matter particles, because that's trivially wrong. And the reason isn't that they have a magnetic dipole moment-it's because they do have, more generally, electromagnetic (through quantum effects) interactions, which dark matter doesn't have.

Maybe this becomes more apparent of what I am saying here. Namely, a "charged up" neutrino can be proven mathematically that it transforms to an electron.

This also has been observed in experiments:

The Wolfenstein matter effect or else known as a “neutrino electron swap”. Basically whet is happening the charge of a bound electron is passed (relayed) to a free neutrino and this then becomes an electron and the original electron looses its intrinsic angular momentum and becomes a neutrino.

This IMHO infers that charge is the reason why charged fermions have two types of transverse polarization, left ad right.

https://sureshemre.wordpress.com/2020/03/28/on-the-transformation-of-neutrino-into-electron/#:~:text=A%20neutrino%20passing%20through%20matter,is%20a%20very%20rare%20process.

Therefore IMO, charge which correlates to intrinsic angular momentum of a spin-1/2 particle is the fundamental reason why charged fermions can observed having two types of handeness whereas chargeless neutrinos are only left-handed and antineutrinos only right-handed.

If the SM says that theoretically, right handed neutrinos (sterile neutrinos) or left handed antineutrinos should exist, well, obliviously IMO the SM theory must be revised to comply with experiment.

Emmanouil, I've read a variety of papers that suggest an electron is a 511keV photon trapped in a chiral twisted double-loop configuration. The charge results from a sinusoidal field variation wrapped into a Mobius-like spinor, wherein the maximum and minima combine to form what looks like an all-round standing field. In this model, mass is merely resistance to change-in-motion for a wave in a closed path. I've also considered the neutrino in detail, and I conclude that it's more like the photon than the electron. However instead of being a transverse wave, it seems to me to be a rotational wave of sorts, akin to a breather. It has no charge, and I can find no evidence of a neutrino travelling at anything other than c. Which means it has no mass, apart from a minor effective mass caused by a concertina-like oscillation. And as far as I can tell, the handedness is what distinguishes a neutrino from an antineutrino.

“Why neutrinos are only left-handed?”

- to answer the question above is necessary before to answer the question – what does the word “a particle” mean at all?, and so, including, why – if that is so, of course [while that isn’t so] - do other particles are arbitrary-handed?, etc.

The scientific answer to the question “what is “a particle”” is fundamentally impossible in mainstream physics, where “particles” – and really everything in Matter, including “Matter” itself, are fundamentally transcendent/mystic phenomena/notions.

The answer so can be , and is, given only in framework of the Shevchenko-Tokarevsky’s Planck scale informational physical model, two main papers are

https://www.researchgate.net/publication/354418793_The_Informational_Conception_and_the_Base_of_Physics, and

https://www.researchgate.net/publication/383127718_The_Informational_Physical_Model_and_Fundamental_Problems_in_Physics .

More see at least 1-st paper, here only a brief and first approximation comment:

- particles [as everything in Matter at all is/are specific disturbances] are specific cyclic disturbances/cyclic algorithms that run on FLE hardware in the Matter’s ultimate base - (at least) [4+4+1]4D dense lattice of primary elementary logical structures – (at least) [4+4+1]4D binary reversible fundamental logical elements [FLE],

- which [the lattice] is placed in the corresponding Matter’s fundamentally absolute, fundamentally flat, fundamentally continuous, and fundamentally “Cartesian”, (at least) [4+4+1]4D spacetime with metrics (at least) (cτ,X,Y,Z, g,w,e,s,ct), FLE “size” and “FLE binary flip time” are Planck length, lP, and Planck time, tP.

The algorithms run as sequential “FLE-by-FLE flipping” that proceeds cyclically along corresponding 4D helixes in utmost fundamental 4D space with metrics (cτ,X,Y,Z ) with the speeds √2c, so front of a helix particle” moves in the space with 4D velocity, c, [bold means 4D vector], c=lP/tP.

So a particle exists at every time moment as FLE-flipping point on its helix, which moves along its 4D momentum P, which created the particle impacting on some the lattice’s FLE; the radius of the helix is λ=ћ/P, that essentially determines the QM uncertainty at particles interactions.

So the “particle-flipping point” has intrinsic “angular momentum”, M, always be equal to ћ, and which is directed along 4D P.

“Rest massless” particles [now for sure known only photons] are created by 3DXYZ space momentums, and so move only in this space, having, correspondingly, M= ћ,

Having rest mass particles are created by cτ-directed space momentums, and so having small speeds in the 3DXYZ space move practically with the speed of light along the cτ-axis [antiparticles in negative cτ-direction, so its M and helixes are opposite to particles ones], so the really observable M 3D projection is “particle spin” be equal ½ ћ,[the particle is “fermion”], from this follows that, since neutrinos are fermions, they for sure have rest masses.

However if a particle has a large energy, it moves practically with the speed of light in the 3D space, and so M and P are directed practically along some 3D line, so the observable M 3D projection is equal to ±ћ.

This projection is called in physics “helicity”, and all rest mass particles are, say, let “left-”, while antiparticles “right-“ handed; as, say, that are high energy electrons and positrons. Neutrinos rest masses are extremely small, and so they are really observed when move practically with the speed of light, having corresponding observable helicities ±ћ; etc.Note, however, that at small speeds in general spin projection on some axis, including 3D momentum direction, and so helicity, are uncertain.

Though note, that in Standard Model also other, and in certain extent similar, term exists - “chirality”, see, say, [https://en.wikipedia.org/wiki/Chirality_(physics)]

“…For massive particles – such as electrons, quarks, and neutrinos – chirality and helicity must be distinguished: ….”

- since “chirality”, which doesn’t depend on a particle 3D speed and “helicity” in reference frames at large speed are different. Really that looks as bit artificial difference, real difference is because of the above – since particles and antiparticles are fundamentally “left-” and “right-“ handed.

In absolute, i.e. that are at rest in 3DXYZ space frames, only in which all parameters of everything in Matter have real values, chirality and helicity at large speeds are practically the same.

Thus “chirality” is a parameter of all having rest mass particles, but in the SM that is as a rule pointed only relating to neutrinos. Really substantiation of this looks as possibly vague, and exists practically for some grounding of P-parity violation at Weak Force interactions, which is really experimentally observed, but that, rather probably here can be other effects.

More see the link above,

Cheers

Emmanouil Markoulakis

Hi Emmanouil,

I don't know if you remember the trispatial vector geometry that directly relates the spin of the electron to its magnetic oscillation.

I just want to mention that your conclusion that handeness variation would be affected by the charge. Elementary fermions (i.e. spin - 1/2) without charge would be stuck only with one type. either left handed or right is in harmony with the trispatial geometry conclusion about the nature of neutrinos, that could not have an electric charge due to the manner that they can be emitted from this perspective. Put in perspective in this paper published in 2013:

Article The Mechanics of Neutrinos Creation in the 3-Spaces Model

Regarding the relation between electron spin and its magnetic energy, the whole concept was explained and published in Sections 10 and 11 of this book chapter published in 2023:

Article Electromagnetic and Kinematic Mechanics Synchronized in thei...

By the way, if interested, the final synthesis of the trispatial model was published this last July:

Article From E=mc2 in normal space to E=m0cIcK in the complex config...

Best Regards, André

Dear André Michaud ,

Long time no see!

How are you my friend?

Yes it would be arrogant and ignorant NOT to foresee that such a unique fundamental difference of the changeless neutrino (I am talking about the elementary charge e and not the weak charge) compared to its charged cousin the electron would be somehow correlated with the uni-handeness of the neutrino.

Best Regards,

Emmanouil

Emmanouil Markoulakis

Dear Emmanouil,

I am fine, and I see that you are in full swing of your exploration of the subatomic level.

On my part, the last 3 papers of my project of reverse engineering the electromagnetic mechanics aspects of the inner structures and interactions of electromagnetic quanta at the subatomic level according to Wilhelm Wien's 1901 project of synchronizing it with kinematic mechanics have just now been published (March, April and July of 2024) and no more articles will be forth coming.

The complete sequence of articles of this project is now at the disposal of the upcoming generation as I had planned 30 years ago.

This project is now over as far as I am concerned.

But even for researcher who may not agree with my analyses, the Reference Sections of each of these articles provides links to the whole sequence of the original papers of the discoverers of all magnetic aspects of point-like behaving elementary charged particles of the turn of the 20th century that all are now in the public domain due to the time elapsed, up to Marmet's 2003 paper and some more recent contributions. If some of them may be of use to you, direct internet links are provided.

Best Regards, André

Here is a toy model illustration of why the charge of the electron is possible responsible for its Dual-Handeness. In the case of the chargeless neutrino it has Uni-Handerness because it's not having any charge:

https://tinyurl.com/3d4ude28

The thread question is scientifically answered in the SS post on page 1. If briefly

- the left-/right- handiness/ left-/right chirality is fundamental property of all [i.e. particles and antiparticles] particles which is really can be observed only in fermions, as the left- handiness of particles and the right- handedness of antiparticles.

The handednesses exist because of particles and antiparticles [what are particles and antiparticles see the SS&VT Planck scale informational physical model papers linked in the pointed SS post] are the same algorithms, which run as moving utmost universally in the Matter’s ultimate base - [4+4+1]4D dense FLE-lattice, and so in corresponding utmost universal “kinematical” space with metrics (cτ,X,Y,Z)

- as sequential FLE-by-FLE flipping point along 4D helix that has radius, λ, λ~ћ/P, P is a particle’s/antiparticle’s 4D momentums; helixes’ 4D axes are directed along P direction, the FLE-flipping point of practically all particles so have intrinsic particle’s 4D “angular momentum”, M, be equal to ћ, the 3DXYZ projection of having rest mass [all] particles Ms is observed as the particle’s “spin” be equal to ½ ћ;

- and, at that, antiparticles’ algorithms run in command order that is reverse to the particles’ order.

So the helixes are “left” and “right” handed, what is by some ways rather possibly really observed/rationally interpreted of the data experimentally at neutrinos interactions.

The particles/antiparticles left-/right- handedness by no means depends on something else, including on what fundamental Nature forces charges [all] particles have, etc.

More see the SS post on page 1, and links in the post.

Cheers

Sergey: neutrinos and antineutrinos have a helicity. Electrons and positrons have a chirality. Electrons and positrons can be likened to the Mobius strip depicted on the Wikipedia spinor article. Try cutting a long thin sinusoidal strip oif paper to represent a 511keV photon, then form it into a Mobius strip to represent the electron, as per this image: https://physicsdetective.com/wp-content/uploads/strip6Spinor.png. This illustration works for me because the sinusoidal strip goes round the loop twice, such that the minima and maxima combine to yield an all-round standing field.

Dear John,

- sorry, but I comment practically only conventional physics, and don’t comment alternative approaches;

- and in this case can only repeat, that both, helicity and chirality, exist because of that all/every particle is a close-loop circular algorithm, which runs as sequential the ultimate base of Matter – (at least) [4+4+1]4D FLE-lattice’s FLE-by-FLE flipping, so article exists constantly and always as some “FLE flipping point” that moves in the utmost universal 4D space along 4D helix [including massless particles helixes are 3D in the 4D space], so this flipping point has 4D “angular momentum” , M, be equal ћ.

Because that in 4D space standard angular momentums mathematically don’t exist, the “angular momentums” of having rest mass particles are observed as 3D projections be equal to ½ ћ, in physics that is called “particle’s spin”; massless particles are observed as having spin be equal to ћ.

4D Mis always directed along particle’s linear 4D momentum, P, at that the 4D helixes of particles and antiparticles are fundamentally oppositely [”left” and “right”] handed, so if a particle moves in 3D space with speeds ~ speed of light, i.e. have large P, P is directed practically along some 3D line,

- and so M 3D projection is observed as be equal to ћ.

The observed [in physics normalized on spin, but that is inessential] projection is called in physics “helicity” and at large speeds it is observed be [for particles/antiparticles] as ”left-” and “right-” handed,

- however, again, at small speeds the spin projection on any axis, including on observed in physics 3D a particle’s momentum [which really is 3D projection of the particle’s 4D P], is in general [if the particle isn’t polarized] uncertain, and so it helicity is uncertain.

Chirality isn’t directly observed, however it exists independently on any experiments, again – that is fundamental trait o particles/antiparticles.

And, again, all that relates to all particles, including neutrinos, all have both , helicity and chirality [note, though, that that above relates only to fermions and massless particles].

More see SS posts above and links in the posts.

Cheers

@ Neutrinos are only left-handed in the Standard Model because of the way the weak force interacts with particles, the theoretical structure of the model, and the original assumption of masslessness. However, the discovery of neutrino mass and ongoing research into right-handed (sterile) neutrinos and Majorana particles suggest there is more to the story, with exciting opportunities for physics beyond the Standard Model. Best Regards--IJAZ

Ijaz, I've never seen any evidence that neutrinos travel at any speed other than the speed of light. I've never seen any evidence of a neutrino at rest. Hence I take note of Francis Perrin's 1933 paper "Possibility of the emission of neutral particles of zero intrinsic mass during β-radioactivity". He talked about a massless neutrino which "would be more analogous to the photon than an electron".

The thread question is scientifically answered and commented in the SS post on pages 1, 2,basing on the Shevchenko-Tokarevsky’s Planck scale informational physical model, the links to two main the model papers see in the first post October 14, 2024. So here only a few notes to the last posts:

In the model [in this case it is enough to see

https://www.researchgate.net/publication/354418793_The_Informational_Conception_and_the_Base_of_Physics], it is rigorously scientifically clarified what are “particles” [and “antiparticles”], including it is proven that rest massless particles can be only bosons [not with spin=0]. Particles with non-integer spin completely obligatorily have rest masses,. Neutrinos are fermions, and so for sure have rest masses as well.

Besides in the model it is explained what are “chirality” and “helicity”, which are experimentally observed [see SS posts on this page], and for these neutrinos properties – and for all other particles obligatorily – there is no necessity for the particles be rest massless. That [“chirality” and “helicity”] is rather clearly observed practically only in experiments with neutrinos is because of that at experiments neutrinos move with large Lorentz factors, i.e. their speeds in experiments differ from the light speed on ~m/s, in high energy physics on mostly ~cm/s and lesser, what really experimentally practically cannot be measured directly.

More see SS posts above and links in the posts.

Happy New Year,

Cheers