tag:blogger.com,1999:blog-7315236707728759521.post1826848330986042312..comments2024-03-27T22:28:06.861-06:00Comments on Dispatches From Turtle Island: Dineutron Bound StatesAndrew Oh-Willekehttp://www.blogger.com/profile/02537151821869153861noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-7315236707728759521.post-20976440822300406222014-08-13T17:40:13.394-06:002014-08-13T17:40:13.394-06:00"Why is the mass of the left-handed one less ..."Why is the mass of the left-handed one less than the mass of the right handed neutrino?"<br /><br />This is one of the big reasons that I do not believe that non-weakly interacting leptons with no EM charge can truly be "right handed NEUTRINOS" and probably need something to put them in another category entirely. I don't believe that there are right handed counterparts to the Standard Model neutrinos.<br /><br />Instead, I think it is more likely that DM particles, if they do exist, are either:<br /><br />In the gravitational sector together with the spin-2 graviton and lacks either baryon number or lepton number or interactions with color charge, weak force or EM, likely as a singlet gravitino with spin-1/2 or spin-3/2 on the gravitational side of a gravito-weak unification that shares a common Higgs bosons but has no other overlap. <br /><br />OR<br /><br />For example, DM is made of composite particles that have a right parity lepton/left parity anti-lepton with charge +/- 0.5 that comes in confined pairs bound by something analogous to color charge that is confining and mediated by a new spin-1 vector boson that does not interact with any other Standard Model particles except DM leptons and perhaps themselves. The DM confining force might be weaker than the strong force by a factor of about 10^6, thus keeping the mass lower.andrewhttps://www.blogger.com/profile/08172964121659914379noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-37864727471736176162014-08-13T16:09:20.317-06:002014-08-13T16:09:20.317-06:00Good questions:
My best guess (based off of what i...Good questions:<br />My best guess (based off of what is consistent with known data sets within experimental error) is that dark matter is a 7.1 keV right-handed neutrino of spin 1/2 and an electron lepton number of +/-1. It's anti-particle would have the same rest mass, but with an electron lepton number of opposite sign (-/+1).<br />This particle would be formed before the temperature of the universe fell below MeV, and would be a non-thermal relic from the big bang with a non-zero(but small) decay rate into its left-handed active electron neutrino. <br /><br />As you mentioned above, a right-handed neutrino (since it has rest mass) interacts with the Higgs Boson. So, it would be generated during the "electro-weak era" of the Big Bang when the temperatures were on the order of GeV to TeV. <br /><br />The big questions I have are: are there muon and taon versions of this right-handed neutrino? If so, what are their rest masses?<br />Why is the mass of the left-handed one less than the mass of the right handed neutrino? (Since no other particle we know has a different mass when it changes from left to right handed polarization.)<br />Can right handed neutrinos cancel with left handed anti-neutrinos?<br /><br />Going back to my first comment regarding your post...the reason I wrote that comment is that any type of neutron matter can't be dark matter because neutrons fail a number of important criterion. For example, dark matter can't interact via the E&M force (neutrons can because they are made of quarks.) Dark matter can't clump together (neutrons can in the form of neutron stars.) And finally, the rest mass of dark matter is roughly in the range of 2-10 keV, which means that neutrons are too heavy to be dark matter.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-2181263948239892832014-08-13T09:53:45.178-06:002014-08-13T09:53:45.178-06:00Also would DM have lepton number, baryon number, o...Also would DM have lepton number, baryon number, or some other DM number? Would it have anti-particles (presumably LH anti-matter and RH matter)?<br /><br />Would it be generated from high energy gravitons much like photons can create particle-antiparticle pairs? What kind of circumstances would generate 4-20 keV gravitons and cause them to condense into matter?<br /><br />Would it have spin-1/2 or spin-3/2?<br /><br />The 3.53 keV line certainly is suggestive of a 7.06 keV or 1.265 keV DM particle. Or perhaps they would be weird and it would take three of them to annihilate since they would not be right on the matter-antimatter axis but would be skewed from it in three ways (a bit like three color quarks v. two direction electric charge) implying 2.58ish keV which would be right on target.<br />andrewhttps://www.blogger.com/profile/08172964121659914379noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-32367521055075254312014-08-13T09:43:26.967-06:002014-08-13T09:43:26.967-06:00Even if two neutrons could be stable, it doesn'...Even if two neutrons could be stable, it doesn't imply that more in a nucleus would be. More generally, the experimental evidence tends to point pretty strongly towards dineutron states being quite unstable.<br /><br />I wouldn't be surprised, however, if consideration of short lived dineutron states could help to resolve the lithium problem in Big Bang Nucleosynthesis and perhaps also shed light on hints of low levels of Boron that is observed in very old stars and not predicted by BBN.<br /><br />WDM does fit the data better than CDM, but the 2-10 keV rest mass is as much a function of the mean velocity of DM particles implied if they are a thermal relic, as they do with the mass itself. If DM is generated in a manner that is not a thermal relic that produces the same mean velocity and mean density of DM particles, then the rest mass limitation is not so great, and one could imagine neutronium particles being produced by means other than thermal relic production.<br /><br />The biggest problem with WDM at 2-10 keV is that particle physics experiments pretty definitively rule out any weakly interacting particle in that mass range. So, we can't have a 2-10 keV WIMP. We would need to have right handed (i.e. "sterile") 2-10 keV particle without electric charge, and the data favor a singlet dominate dark sector over a multi-generational one (although, if there were three generations of right parity dark matter particles and 2-10 keV was the lightest and the heavier ones decayed into the lighter ones with a mean lifetime of even 10 million years or less, that would work out.<br /><br />A 2-10 keV DM particle could have a tiny Yukawa coupling to the Higgs boson in addition to its gravitational coupling (which would be experimentaly impossible to measure) even though it couldn't couple to photons or W bosons or Z bosons. Also, if it were a composite particle that was color charged, the gluon field would make them at a minimum not much lighter than a proton (ca. 970 GeV) (the lightest fermionic hadron) since even with zero rest mass quarks, lattice QCD predicts that a proton would weigh about 840 GeV +/-.<br /><br />DM-genesis would still be a problem, however and some self-interaction term might make sense although it would require a new boson as well.andrewhttps://www.blogger.com/profile/08172964121659914379noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-90677910043179016552014-08-12T17:19:56.583-06:002014-08-12T17:19:56.583-06:00Neutron balls would not make good dark matter part...Neutron balls would not make good dark matter particles because they would clump together, and eventually make neutrons stars or other much larger objects. Free neutrons would much rather stick to nuclei. Also, we can rule of neutrons as dark matter particles because more neutrons in the early universe would effect the concentration of helium and deuterium.<br /><br />In order to be consistent with all data sets, dark matter needs to be a non-electrically-charged fermion with a rest mass of ~2-10 keV.Anonymousnoreply@blogger.com