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View Full Version : Is Dark Matter Made up of Sterile Neutrinos?



Fraser
2006-Mar-24, 04:56 AM
SUMMARY: Since it makes up a large part of the Universe, you'd think we'd know what dark matter is by now. Sorry, it's still a mystery, but new theories are coming out all the time. An international team of researchers are now theorizing that dark matter could be a class of particles known as "sterile neutrinos". These particles, formed right at the Big Bang, could account for the Universe's missing mass, and would have the handy side effect of speeding up the early formation of stars.

View full article (http://www.universetoday.com/am/publish/sterile_neutrinos_dark_matter.html)
What do you think about this story? post your comments below.

antoniseb
2006-Mar-24, 01:20 PM
I'm aware of tests for Neutralinos that might turn up something in the next few years. What could possibly be a test for Sterile Neutrinos? I'd think that if there were something with a lepton number and a mass of a few KeV, that we'd have seen evidence of it in the accelerators.

Is there someone on the forum who understands the proposed properties of Sterile Neutrinos enough to explain why we haven't observed the energy defecits they should be causing in the lab?

iantresman
2006-Mar-24, 04:28 PM
This sounds like new physics to explain new physics. To paraphrase the little boy in the Emporer's New Clothes, would it be radical to suggest that the reason we haven't the observed the energy defecits "Sterile Neutrinos" should be causing in the lab, is because they're not there?

Regards,
Ian Tresman

antoniseb
2006-Mar-24, 05:34 PM
would it be radical to suggest...
No, but my question was more to get an explanation as to why we don't see them, as opposed to a categorical statement that they aren't there. The people postulating Sterile Neutrinos have surely thought about this, and must have some idea why we don't see them. With Neutralinos, the answer is because they are too massive to have been produce in the labs so far.

antoniseb
2006-Mar-24, 10:04 PM
Rocky, welcome to the BAUT forum. You cannot post religious statements here. Please read our rules before posting again.

blueshift
2006-Mar-25, 03:02 PM
I'm aware of tests for Neutralinos that might turn up something in the next few years. What could possibly be a test for Sterile Neutrinos? I'd think that if there were something with a lepton number and a mass of a few KeV, that we'd have seen evidence of it in the accelerators.

Is there someone on the forum who understands the proposed properties of Sterile Neutrinos enough to explain why we haven't observed the energy defecits they should be causing in the lab?We might not be able to measure them yet. I must admit that I am a bit confused why such measurement hasn't taken place. A possible experiment might be as follows as far as my two cents are worth:

Smash protons into a target and look at the tracks left by the collision...There should be pions and kaons and particle/antiparticle pairs..Magnets then filter out most material, leaving a pion beam with a positive charge. The pion beam will decay into neutrinos, electrons, muons and a few other particles..Smash those particles into a 200 foot steel and concrete wall and only neutrinos come out the other side.

Now take the following finding:


http://researchnews.osu.edu/archive/molhydro.htm

If that still holds up you add a equal amounts of bumpy dust into two remaining chambers, one that gets bombarded with the beam and the other doesn't.

If the speed of molecular hydrogen formation is increased in the "beamed" chamber compared to the "unbeamed" other chamber then, as that article indicates, that should indicate presence of sterile neutrinos.

Yet we might not be able to detect them for the following reasoning:

Since there is also supposed to be some interaction of sterile neutrinos with other neutrinos and we might only be able to find some evidence in an odd way. For instance, sterile neutrinos might cause oscillations to change at a specific frequency and a mass of 1 KeV might appear. I am not sure that such an experiment is that easy to perform since we are just getting a grip on neutrino oscillations and the distances for travel has to be great to observe them.

This is all speculation on my part and I am sure others can calculate something better.

Gerald Lukaniuk
2006-Mar-25, 09:57 PM
Great article! However, in still wondering about this "sterile" concept. Do they really mean some puritanical notion like "asexual" or celibate? (Opps no s.. please we're scientists.) Or maybe apolitical. Perhaps it is similar to the state of cleanliness my ex German rocket scientist physics prof. used to insist our lab books had to reflect for us to get a passing grade. I get nostalgic when I read ludicrous suggestions like
"The lack of lepton number was converted to a non-zero baryon number.” I can still see Herr Professor slamming down his pointer when a bright student (who clearly does not have what it takes to be a good scientist) points out a contradiction in a theory. "Nein there must be Order in the Universe!"
There is a fundamental problem with algebra itself, which was originally designed by moneychangers, and accountants erroneously implying both zero and negative integers are real numbers to justify indebtedness. It is just a useful but approximate tool in science but leaves a residue of absurd contradictions like irrational numbers or "dark energy"

blueshift
2006-Mar-25, 10:50 PM
Great article! However, in still wondering about this "sterile" concept. Do they really mean some puritanical notion like "asexual" or celibate? (Opps no s.. please we're scientists.) Or maybe apolitical. Technically speaking, you are not far off ASFAIK.
Neutrinos relate to the weak force which does involve the transformation of one particle into another. Sterile neutrinos (if they do exist) do not relate to the transformation of particles into other particles. Hence, the name "sterile" is fitting.

antoniseb
2006-Mar-25, 10:51 PM
I can still see Herr Professor slamming down his pointer when a bright student (who clearly does not have what it takes to be a good scientist) points out a contradiction in a theory. "Nein there must be Order in the Universe!"
Amusing, but be careful with the stereotyping.

Gerald Lukaniuk
2006-Mar-26, 02:24 AM
Amusing, but be careful with the stereotyping.
This prof was by no means a stereotype having both met Einstein and brought togethere meeting of all the great cosmologists but he does reflect academics at worst.

Gerald Lukaniuk
2006-Mar-26, 02:46 AM
Technically speaking, you are not far off ASFAIK.
Neutrinos relate to the weak force which does involve the transformation of one particle into another. Sterile neutrinos (if they do exist) do not relate to the transformation of particles into other particles. Hence, the name "sterile" is fitting.
These critters are beleived to have to decayed into something? that seeded hydrogen formation shunning H's uglier sister anti-H. Then seeing all the little H's running around they decided to get sterilized so we don't see any little flashes of light as a new bouncing baby Hydrogen pops into the universe. So that where little hydrogens come from. So much for the birds and the bees. It would seem that particle physics has been able to get on one of these guys or his anti particle brother to sire some antihydrogen.

Starblade
2006-Apr-01, 09:27 PM
Technically speaking, isn't whether a neutrino right handed or left handed dependant on frame of reference? IE if a left handed neutrino burst came from another galaxy a long time ago and far far away (Sorry, I just had to say that. :P) wouldn't it look like a right handed neutrino going slowly here?

Or am I totally wrong about this?

blueshift
2006-Apr-03, 01:44 AM
Technically speaking, isn't whether a neutrino right handed or left handed dependant on frame of reference? IE if a left handed neutrino burst came from another galaxy a long time ago and far far away (Sorry, I just had to say that. :P) wouldn't it look like a right handed neutrino going slowly here?

Or am I totally wrong about this?Reference frame and reference point are not the same thing. A reference frame is what shares your motion, not your position. Some distant civilization 8 billion ly away might be living on a planet the precise size of earth with the same distance from its own star and same period of annual revolution and same spin. It would have to be the same ecliptic plane as earth is as well. It would be in the same reference frame as earth as long as the distances between them do not change. A coordinate system could be drawn on graph paper representing such a reference frame with earth at one set of coordinates and the other planet at another set of coordinates. The coordinate system would share the motion of both planets so each planet would not depart from its set of coordinates. Other coordinate systems could be drawn right over the previous one with larger or smaller sizes to each set of coordinates. One could be metric while the other American Standard. They would all be in the same reference frame as well as long as they shared the same motion. That would not change anything. Who ever is closest to the neutrino records the data that counts and relays the recording to all the other coordinates at speed c.

You won't be in the same reference frame with earth if you move around on earth at all. If you throw a baseball, your arm will not be in the same reference frame as you are. Your elbow will not be in the same reference frame as your fingers. They will have different motions. There are many reference frames all along that arm as long as it moves.

I hope this helps.

Starblade
2006-Apr-04, 03:13 AM
I hope this helps.

Actually, it doesn't. Thanks anyways, though.

I know the difference. I wasn't referring to anything specific in the article. I was referring to the article in general. If you were in a spaceship going in the opposite direction of our sun, and going extremely fast, won't left-handed neutrinos look like right handed neutrinos?

That's what I'm saying. If it works for electrons, it should work for neutrinos.

antoniseb
2006-Apr-04, 12:20 PM
If you were in a spaceship going in the opposite direction of our sun, and going extremely fast, won't left-handed neutrinos look like right handed neutrinos? ... If it works for electrons, it should work for neutrinos.

This doesn't work for electrons either. Being in a spaceship going the opposite way around the galaxy from the Sun gives you some different velocity, but that doesn't hange the spin of the electron.

Shahbaz
2006-May-31, 08:37 AM
I was wondering that this idea might create little problem regarding another experiment which measured the gravitational lensing because of dark matter.
If the mass of this sterile neutrino is vey small so for any measurable gravitational lensing the amount of sterile neutrini gathered up in a place would be very improbable.

I would like some comments on this.

antoniseb
2006-May-31, 10:04 AM
If the Sterile neutrinos collectively have enough mass to account for the lensing, then they will account for the lensing. If not, then some other particle(s) is/are responsible. This article was speculation about what kind of particle we should be looking for.

Svemir
2006-May-31, 12:57 PM
Can sterile neutrinos be ruled out as warm dark matter candidates? (http://arxiv.org/PS_cache/astro-ph/pdf/0605/0605706.pdf)

antoniseb
2006-May-31, 02:09 PM
That's an interesting paper Svemir. One thing that I don't often see is an analysis of Dark Matter that allows for there to be multiple particles that make it up. Suppose, for instance that 20% of dark matter were WDM sterile neutrinos, 50% were CDM neutralinos, 25% were Axions, AND 5% are hot dark matter (neutrinos). The paper makes some strong constraints that assume there is only one type of dark matter.

folkhemmet
2006-May-31, 03:07 PM
Dark matter is a very rich subject which spans particle physics, astrophysics, and cosmology. The underground direct dark matter searches are just now exploring the interesting part of the SUSY parameter space. The current limit for WIMP dark matter is that it most have a cross-section less than 1.6X10^-43 cm^2 at a mass of 60 Gev (Sadoulet et al 2006). Interestingly, many of the premier particle physics models seem to be converging on a WIMP cross-section somewhere between 10^-44 to 10^-46 cm^2. This means that a huge discovery--that is, the discovery of cold dark matter may take place very soon, within the next couple of years as the CDMS and other groups increase their detector masses and sensitivities. These are exciting times.

Neutrinos are interesting. There existence brings up two points: (i) we should not get too impatient that CDM has not been detected yet because it took a lot of time, effort, and technological inovation to discover the neutrino, and (ii) neutrinos prove that at least some of the dark matter is not baryonic. Neutrinos are indeed hot dark matter, even though they probably make up less than a percent of omega total.

Blob
2006-Jul-24, 12:22 PM
Title: Constraints on Sterile Neutrino Dark Matter
Authors: Kevork Abazajian, Savvas M. Koushiappas (Los Alamos National Laboratory)
(UPDATE)

Researchers present a comprehensive analysis of constraints on the sterile neutrino as a dark matter candidate. The minimal production scenario with a standard thermal history and negligible cosmological lepton number is in conflict with conservative radiative decay constraints from the cosmic X-ray background in combination with stringent small-scale structure limits from the Lyman-alpha forest. They show that entropy release through massive particle decay after production does not alleviate these constraints. They further show that radiative decay constraints from local group dwarf galaxies are subject to large uncertainties in the dark matter density profile of these systems. Within the strongest set of constraints, resonant production of cold sterile neutrino dark matter in non-zero lepton number cosmologies remains allowed.

Read more (http://arxiv.org/PS_cache/astro-ph/pdf/0605/0605271.pdf) (36kb, PDF)

trinitree88
2006-Jul-25, 04:38 AM
SUMMARY: Since it makes up a large part of the Universe, you'd think we'd know what dark matter is by now. Sorry, it's still a mystery, but new theories are coming out all the time. An international team of researchers are now theorizing that dark matter could be a class of particles known as "sterile neutrinos". These particles, formed right at the Big Bang, could account for the Universe's missing mass, and would have the handy side effect of speeding up the early formation of stars.

View full article (http://www.universetoday.com/am/publish/sterile_neutrinos_dark_matter.html)
What do you think about this story? post your comments below.

Fraser. Peter Biermann and Alexander Kusenko are seemingly glossing over the fact that no particle physics experiment has ever seen:
1. failure to conserve Lepton Number
2. failure to conserve Baryon Number
The high transverse velocities observed in pulsars requires no new physics, and is adequately explained by the late eighties work of the Russian theorists Leinson, and Oraevskii.(Sov. Journal of Nuclear Physics) The scattering of neutrinos is modeled by them as bimodal:
1. neutrino/quark-gluon bag scattering(symmetrical)
2. an enhanced, additional 30% from neutrino/ spin-wave(magnons) scattering(asymmetrical)
Their secondary scattering is coupled to the B field. All weak interactions show parity effects, an innate asymmetry. It is the asymmetry in the secondary scattering that is likely the cause of pulsar ejection velocities.
Coefficients of correlation between observed transverse velocities vs residual magnetic fields run to ~ .7. Anything above .3 is statistically significant. ( Parity, Pulsars, and Supernova Remnants...paper submitted for class credit. MIT, Bates Linear Accelerator, Feb 92. NSF Winter Course on Nuclear and Particle Physics. Syllabus and talk given at Vassar College, Nov. 92..."Parity, Pulsars and Supernova Remnants". Stating that "the origin of the pulsar high velocities is unknown"...in the excerpt, is simply not true. Pete.

folkhemmet
2007-Mar-24, 11:20 AM
Here is a more recent paper that ends by suggesting that sterile neutrinos may indeed be the dominant form of dark matter in the Universe: "The Observed properties of Dark Matter on small spatial scales" astro-ph/0703308