SN1987A - A Retrospective Analysis Regarding Neutrino Speed

Discussion in 'Physics & Math' started by Walter L. Wagner, Sep 28, 2011.

  1. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member


    SN1987A, A Retrospective Analysis Regarding Neutrino Speed

    In 1987 the physics community was surprised by a fortuitous supernova. The light from the supernova reached Earth on February 23, 1987, and as it was the year’s first supernova, it was designated SN1987A. The parent star was located approximately 168,000 light-years away, in the Large Magellanic Cloud, which is the Milky Way’s companion dwarf galaxy. It became visible to the naked eye in Earth’s southern hemisphere.

    In this observation, a star core collapsed and released a lot of energy. Most of the excess energy is predicted in theory to be radiated away in a ‘cooling phase’ massive burst of neutrinos/anti-neutrinos formed from pair-production (80-90% of the energy release) and these neutrinos would be of all 3 flavors, both neutrinos and anti-neutrinos, while some 10-20% of the energy is released as accretion phase neutrinos via reactions of electrons plus protons forming neutrons plus neutrinos, or positrons plus neutrons forming protons plus neutrinos (1 flavor, neutrino and anti-neutrino). The observations are also consistent with the models' estimates of a total neutrino count of 10^58 with a total energy of 10^46 joules.

    Approximately three hours before the visible light from SN 1987A reached the Earth, a burst of neutrinos was observed at those three separate neutrino observatories. This is due to neutrino emission (which occurs simultaneously with core collapse) preceding the emission of visible light (which occurs only after the shock wave reaches the stellar surface). At 7:35 a.m. Universal time, Kamiokande II detected 11 antineutrinos, IMB 8 antineutrinos and Baksan 5 antineutrinos, in a burst lasting less than 13 seconds.

    In this respect, a point that deserves to be stressed is that all 3 detectors observed a relatively large number of events in the first one second of data-taking, about 40% of the total counts (6 events in Kamiokande-II, 3 events in IMB and 2 events in Baksan), while the remaining 60% were spread out over the course of the next 12 seconds.

    In other words, these neutrinos travelled a total distance of 5.3 X 10^12 light seconds (168,000 light years), with almost half originating at roughly the same time (within about a 1 second burst of neutrino emission), and all arrived at earth (the light-transit time of earth's diameter is << 1 second and is not a factor due to the spacing of the detectors) within about 1 second of each other. In other words, they all travelled at close to the same speed to within nearly 13 orders of magnitude (5.3 X 10^12 seconds/1 second), far greater than any other measurement precision ever made for the speed of light. And, they all travelled at very close to the speed of light (travelling the same distance as the photons that reached Earth 3 hours later) at a speed consistent to c to within about 1 part per 500 million).

    One would expect that since the neutrinos are emitted with potentially a range of energies, that their transit time would have exhibited a range of speeds (all in the 0.9999+ c speed range) if they were sub-luminal particles. While it has been believed that because the total ‘rest-energy’ of a neutrino is on the order of a few eV, while the rest-mass of an electron is about 511 KeV, neutrinos would all travel at close to c if they have mass and high-energy. But the energy they carry is sufficient to bring their speed to near c to only about .999999+ c if they are mass-particles, and the range in energies from pair-production should produce a spread in those speeds, albeit at many significant figures beyond the first few 9s. The calculated energy is indeed high, but not infinite. But that is not what was observed. They were observed to have all travelled at the same speed to 13 significant figures. In other words, had they had slight variations in their speed all slightly less than c, they would have had a large spread in the arrival time at Earth, on the order of days to years. The actual observation is far more consistent with neutrinos as having zero rest mass, and traveling at c, and appears wholly inconsistent with having a rest-mass and ejected with a spectrum of varying energies.

    Let us briefly review the history of the discovery of neutrinos.

    Historically, the study of beta decay provided the first physical evidence of the neutrino. In 1911 Lise Meitner and Otto Hahn performed an experiment that showed that the energies of electrons emitted by beta decay had a continuous, rather than discrete, spectrum. Unlike alpha particles that are emitted with a discrete energy, allowing for a recoil nucleus to conserve energy and momentum, this continuous energy spectrum to a maxium energy was in apparent contradiction to the law of conservation of energy and momentum for a two-body system, as it appeared that energy was lost in the beta decay process, and momentum not conserved.

    Between 1920-1927, Charles Drummond Ellis (along with James Chadwick and colleagues) established clearly that the beta decay spectrum is really continuous. In a famous letter written in 1930, Wolfgang Pauli suggested that in addition to electrons and protons, the nuclei of atoms also contained an extremely light, neutral particle. He proposed calling this the ‘neutron’. He suggested that this ‘neutron’ was also emitted during beta decay and had simply not yet been observed. Chadwick subsequently discovered a massive neutral particle in the nucleus, which he called the “neutron”, which is our modern neutron. In 1931 Enrico Fermi renamed Pauli's ‘neutron’ to neutrino (Italian for little neutral one), and in 1934 Fermi published a very successful model of beta decay in which neutrinos were produced, which would be particles of zero rest mass but carrying momentum and energy and travelling at c, or very low-mass particles traveling at nearly c.

    Before the idea of neutrino oscillations came up, it was generally assumed that neutrinos, as the particle associated with weak interactions, travel at the speed of light with momentum and energy but no rest-mass, similarly to photons traveling at the speed of light with momentum and energy but no rest-mass and associated with electron-magnetic interactions. The question of neutrino velocity is closely related to their mass. According to relativity, if neutrinos carry a mass, they cannot reach the speed of light, but if they are mass-less, they must travel at the speed of light.

    In other words, in order to conserve both momentum and energy during beta decay, the theoretical particle called a 'neutrino' was predicted. It was presumed that the neutrino either travelled at the speed of light and had zero rest mass (most dominant theory until the 1980s) but momentum (analogous to the electromagnetic photon, which travels at the speed of light, with momentum, but with zero rest-mass), or else it travelled at near-relativistic speeds with very small rest-mass (the less popular and unproven theory).

    However, with the apparent recent discovery of neutrino oscillation, it became popular though not universal to assert that neutrinos have a very small rest mass: "Neutrinos are most often created or detected with a well defined flavor (electron, muon, tau). However, in a phenomenon known as neutrino flavor oscillation, neutrinos are able to oscillate between the three available flavors while they propagate through space. Specifically, this occurs because the neutrino flavor eigenstates are not the same as the neutrino mass eigenstates (simply called 1, 2, 3). This allows for a neutrino that was produced as an electron neutrino at a given location to have a calculable probability to be detected as either a muon or tau neutrino after it has traveled to another location. This quantum mechanical effect was first hinted by the discrepancy between the number of electron neutrinos detected from the Sun's core failing to match the expected numbers, dubbed as the "solar neutrino problem". In the Standard Model the existence of flavor oscillations implies nonzero differences between the neutrino masses, because the amount of mixing between neutrino flavors at a given time depends on the differences in their squared-masses. There are other possibilities in which neutrino can oscillate even if they are massless. If Lorentz invariance is not an exact symmetry, neutrinos can experience Lorentz-violating oscillations."

    Thus, observed oscillations in 'flavor' (type of neutrino based on origin source) suggested that neutrinos had a small rest mass, and therefore according to Einstein had to travel at less than c.

    But do they?

    "Lorentz-violating neutrino oscillation refers to the quantum phenomenon of neutrino oscillations described in a framework that allows the breakdown of Lorentz invariance. Today, neutrino oscillation or change of one type of neutrino into another is an experimentally verified fact; however, the details of the underlying theory responsible for these processes remain an open issue and an active field of study. The conventional model of neutrino oscillations assumes that neutrinos are massive, which provides a successful description of a wide variety of experiments; however, there are a few oscillation signals that cannot be accommodated within this model, which motivates the study of other descriptions. In a theory with Lorentz violation neutrinos can oscillate with and without masses and many other novel effects described below appear. The generalization of the theory by incorporating Lorentz violation has shown to provide alternative scenarios to explain all the established experimental data through the construction of global models."

    If they have a rest mass, and travel at near-c but slightly below c, there should be a slight variation in their speeds based upon their total energy (most of which would be kinetic energy, not rest-mass energy). In other words, various high-energy neutrinos would travel at, for example, .99999997 c or .99999995 c, etc., and this variation in speed, however slight, should be detectable.

    But the variation in neutrino velocity from c, in the 1987a data, was at most about 1/490,000,000 (3 hours/168,000 years). It was actually much closer to c than that (and most likely at c) because of the head-start the neutrinos received over the photons. More importantly, their close arrival time (40% within 1 second) implies an identical speed to 13 orders of magnitude. While they are all released as essentially prompt neutrinos, the remaining energy of the core implosion should have taken a significant amount of time to churn through the overlying massive amount of star. While one might argue that it would take less than 3 hours for the core implosion energy to reach the surface of the star, and then start its race to Earth with the previously released neutrinos, I believe this has been fairly well presented previously in the astrophysics community to be a reasonable value.

    The calculations for the volume of the star that actually underwent core implosion shows such a volume at about 60 km diameter, or about 1/100 light-second, and would not have been a factor in the timing of the arrival of the neutrinos.

    Most of the neutrinos released are not from the proton/electron or positron/neutron fusion releasing electron neutrinos and anti-neutrinos. Rather, the energy of the degeneracy creates neutrino/anti-neutrino pairs of all 3 flavors, which travel in opposite direction (to conserve momentum). Most of the neutrinos released were therefore from this pair-production, which would have occurred relatively simultaneously (to within a few seconds) within the volume of that imploding core.

    So, the spread in arrival time of the neutrinos on Earth, measured at 13 seconds, is accounted almost entirely due to the time for the pair-production and cooling to be completed. In other words, all of the neutrinos that travelled those 168,000 light years travelled at exactly the same speed without regard to their energy to within 13 orders of magnitude.

    So the 1987a data show both an extreme example of exactly the same flight of time without regard to energy, and a speed almost exactly equal to c to within far better than 1/500,000,000 based on the 3 hour discrepancy of the early arrival of the neutrinos compared to the photons after travelling for some 168,000 years.

    This data strongly suggests that neutrinos travel at light speed with energy and momentum, but no rest mass, as originally surmised; and not at slightly below c with some slight rest-mass, as has been the notion as of late (since flavor oscillation was recently detected).

    Quotations and sources listed below:

    Improved analysis of SN1987A antineutrino events. G. Pagliaroli, F. Vissani, M.L. Costantini, A. Ianni, Astropart.Phys.31:163-176,2009.
    Last edited: Sep 29, 2011
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  3. CptBork Robbing the Shalebridge Cradle Valued Senior Member

    You could make a garbage truck fly arbitrarily close to lightspeed if you put enough energy into it, so I don't see how this in any way negates the small neutrino masses suggested by flavour oscillations. What velocity distribution should one reasonably expect from a supernova event based on current neutrino mass estimates, if not the values they already obtained?
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  5. Trippy ALEA IACTA EST Staff Member

    Pair production has nothing to do with it in a Type II core collapse supernova.

    The Fe/Ni core mass exceeds the point where it can continue to be supported by degeneracy pressure.
    It collapses, at a large velocity.
    It gets really hot, really quickly, and emits gamma rays.
    The gamma rays cause the photo dissociation of Iron and Nickle nuclei into Helium nuclei and free neutrons.
    The P-T regime by this stage forces electron capture beta decay to occur, and it is this beta decay that results in the emission of Neutrinos, not pair production.

    Pair production only comes into the pair instability supernova.
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  7. mathman Valued Senior Member

    I believe that it is events like these that make many scientists skeptical about neutrinos traveling faster than light, as reported by CERN.
  8. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

    "In this work we focus on the only mechanism that has been studied in some detail: the neutrino-driven mechanism ...

    In the neutrino-driven mechanism, there are two main phases of neutrino emission:

    i) A thermal phase, called cooling, occurring when the proto-neutron star cools quietly. This phase involves most of the emitted neutrinos, 80-90% in energy.

    In the last phase of the SN collapse the nascent proto-neutron star evolves in a hot neutron star (with radius Rns ) and this process is characterized by a neutrinos and anti-neutrinos flux of all species. This is the cooling phase; ... "

    October 2, 2008, Improved analysis of SN1987A antineutrino events
  9. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

    We're not talking about such objects. If neutrinos have a rest mass, and are acclerated to various high-energies such that they are near light-speed, they would have slight variations in those speeds. In other words, they would not all be accelerated to exactly the same speed via a thermal cooling pair-production process, but would have a spread of energies. We would see this at well before the 13th decimal place on their measured variation from their flight speed (which we can call c'), and c' (their actual speed to 13 orders of magnitude precision) is the same as c to within at least 1/500,000,000 as measured. Since it appears they travel with constant speed (not variable but close to c) and very close to c, they almost certainly travel at c. This was also the Fermilab result when measuring their flight-time through a large distance through the Earth.
  10. Trippy ALEA IACTA EST Staff Member

    Supports exactly what I have said, and still isn't talking about pair production.
  11. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member


    Pair production by photons in dense matter.
  12. Trippy ALEA IACTA EST Staff Member

  13. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

  14. Trippy ALEA IACTA EST Staff Member


    It still doesn't contradict what I initially said about the source of the initial burst of the neutrinos.

    It provides a mechanism by which an evolving neutron star might continue to emit Neutrinos - but both that and the cooper pairing deal with the other 9s of what was observed, and neither process excludes the electron capture beta decay I described.

    The point being, and the point that I was making, among other things, is that the massive burst is not associated with the cooling phase, at least not according to your own sources, the massive burst is associated with the accretion phase (I think that was the term used by one of the papers you linked to), but all the other mechanisms (cooper pairing, pair production) are (or appear to be) associated with the cooling phase that takes place after the neutron star has been formed, not the accretion phase burst which takes place as it forms.
  15. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

    Did you not read my post #5 above? It clearly states that 80-90% of the neutrinos are released during the cooling phase (and elsewhere in the article it references that the accretion phase (10-20% of the neutrino release) might occur 'contemporaneously' with the cooling phase.

    However, none of that is really relevant to the thrust of this post, which is that there is a prompt burst of 40% of the neutrinos that lasts for 1 second, and that therefore those neutrinos all travel at the same speed to Earth, over the 168,000 years of travel, which is phenomenally close together to 13 decimal places of c' (the neutrino speed), and strongly implies that the c' actual speed of the neutrinos is also the same value as the c of photons; i.e. a constant. The 1/500,000,000th measured variation from c (assuming that they left at exactly the same time, which we know is not true and therefore the figure is much tighter than that) is also compelling evidence that c' is actually c because the measurements are so close to each other. More importantly, this is very accurately measured and so we know those neutrinos all travel very close to c, not varying from it by 1/40,000th as CERN data asserts.

    It is also interesting that at least 4 of the Gran Sasso researchers refused to sign on to the article - likely because they understood the above generally (without having read my post specifically, of course, because I posted this several weeks after they refused to sign on).
  16. Trippy ALEA IACTA EST Staff Member

    Yes, I'm routinely in the habit of replying to posts that I quote in full, without reading them.

    Please Register or Log in to view the hidden image!

    Actually, it would be the other way around, with the Cooling phase occuring contemperaneously with the accretion phase. Also note that SN 1987A is a bad example in this regard - note the reference to 'Hints' of the cooling phase in your article? It suggests that the majority of SN1987A neutrinos that were detected were accretionary.

    This is important to understand, because it alludes to something else buried in the data - the neutrino emission from SN1987A was cut short - the model that I have seen that best fits this is if the forming neutron star was massive enough that as it cooled (by emitting accreetionary neutrinos) it's physical radius fell below its schwarzchild radius, and the neutron star collapsed into a black hole, which is consistent with, for example, the fact that no neutron star has yet been observed. And yes, there are other models, however...

    You've only just figured out something that Physicists realized back in 1987 and used to set limits on Neutrino masses?

    Incidentally, the narrow shape of the accretionary burst is not neccessarily indicative of anything more than the small volume from which they were emitted.

    Or that they were emitted from a small volume.

    No, not really.
  17. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

    1. Contemporaneous is contemporaneous -- at the same time.

    2. Yes, the 40%/60% suggests a somewhat different model.

    3. Might be so.

    4. No, I've been well aware of the method for upper limits of rest-mass since I read about SN1987A in 1987, nearly a quarter century ago.

    5. The 1 second prompt burst requires a small 1-light-second diameter volume as well, but it also requires a prompt burst of 1 second. Both are required.

    6. Yes, it is interesting that 4-5 researchers refused to have their names included. Certainly it is interesting to them. It is indicative that they find the publication premature. They likely know about the results I discussed in this post.

    There is no getting around the fact that for nature to have results equating to the CERN publication, the SN1987A neutrinos would have had to have arrived about 4 years early. Instead, they were only 3 hours early, which can be accounted for entirely by the estimated time for the core-implosion energy release to churn through the upper layers of the star and burst forth as a large photon emission from the outer surface, giving the neutrinos an effective 3-hour head-start.

    The fact of the 1-second prompt burst being measured for 40% of the neutrinos that were detected is indicative of how close together in speed that prompt burst was - - measured to be the exact same speed to 13 orders of magnitude.

    Those two facts - close arrival time with the photons, and exact same speed to 13 orders of magnitude -- strongly suggests neutrinos are luminal particles, not subluminal (or supraluminal as CERN suggested).
    Last edited: Sep 29, 2011
  18. OnlyMe Valued Senior Member

    Walter.., how do you accelerate a neutrino?

    And though I have not read the complete Fermilab results, it has been my understanding that their margin of error was a significant factor and the "at c" conclusion then a guess.
  19. OnlyMe Valued Senior Member

    Walter.., this keeps bugging me every time you bring it up. You keep equating a neutrino emission event time of say 1 second (above) with the light time diameter of the volume. To me this keeps suggesting that the neutrinos are emitted from the far side of the volume instead of from somewhere within the volume.

    Why is the emission duration equal to the light time "diameter"? Instead of say the light time radius? (Assuming the neutrinos originate from somewhere closer to the center or core than the surface.)
  20. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

    It's actually not anywhere near 1 light-second diameter for the model used in my references, but rather on the order of 50 km, as per various graphs in the paper. The neutrino transit time of such a small volume is neglible compared to 1 second. What I don't have is a more exact timing of the arrivals of the first 40% other than that it was attributed to the first 1 second, while the other 60% of the neutrinos to the remaining 12 seconds of neutrino registration.

    Good question, how do you accelerate a neutrino? How do you accelerate a photon - you don't - they have no mass and 'instantaneously' obtain their momentum and speed (c) at their point of generation (such as when electrons change orbits, or other electromagentic changes, annihilations, whatever). I believe the same will hold true for neutrinos if they are massless. And, they should be able to be created with a range of energies and momentums.

    If they have mass, there should be an acceleration process, but no model is detailed that I'm aware of that fits the facts.
  21. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

    "I received a comment on this piece from Luca Stanco, a senior member of the Opera collaboration (who also worked on the ZEUS experiment with me several years ago). He points out that although he is a member of Opera, he did not sign the arXiv preprint because while he supported the seminar and release of results, he considers the analysis "preliminary" due at least in part to worries like those I describe, and that it has been presented as being more robust than he thinks it is. Four other senior members of Opera also removed their names from the author list for this result."

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