• Neutrino speed and mass

    From Phillip Helbig (undress to reply)@21:1/5 to raymond.yohros@gmail.com on Thu Mar 26 11:53:29 2020
    In article <0013b48a-26fc-4b7c-ade4-a70929efa9a7@googlegroups.com>, <raymond.yohros@gmail.com> writes:

    Why then can we not determine what % of the speed of light
    the particles where traveling at and with some algebra as usual
    determine their masses as well?

    Note that neutrinos from the supernova 1987A in the Large Magellanic
    Cloud emitted neutrinos which were detected on Earth. Since the
    difference in emission times of light and neutrinos is only about 3
    hours, this is negligible for the travel time of 157,000 years and thus provides a good lower limit on the speed of neutrinos (i.e. very close
    to the speed of light). This gives an upper limit on the mass of the
    electron neutrino of about 26 eV. Current limits are about 0.11 eV.
    However, because of neutrino oscillations, we know that it is non-zero.

    [[Mod. note -- To amplify one point Phillip made: measurements of neutrino oscillations tell us the *difference* between the *squares* of the masses
    of different types of neutrinos, i.e., they tell us something like
    m1**2 - m2**2 . But if my dim recollection is correct, they don't
    easily tell us which of the 3 types of neutrinos m1 and m2 refer to.
    -- jt]]

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  • From raymond.yohros@gmail.com@21:1/5 to All on Thu Mar 26 23:24:52 2020
    On Thursday, March 26, 2020 at 1:53:33 PM UTC-5, Phillip Helbig (undress to reply) wrote:
    In article <0013b48a-26fc-4b7c-ade4-a70929efa9a7@googlegroups.com>, <raymond.yohros@gmail.com> writes:

    Why then can we not determine what % of the speed of light
    the particles where traveling at and with some algebra as usual
    determine their masses as well?

    Note that neutrinos from the supernova 1987A in the Large Magellanic
    Cloud emitted neutrinos which were detected on Earth. Since the
    difference in emission times of light and neutrinos is only about 3
    hours, this is negligible for the travel time of 157,000 years and thus provides a good lower limit on the speed of neutrinos (i.e. very close
    to the speed of light). This gives an upper limit on the mass of the electron neutrino of about 26 eV. Current limits are about 0.11 eV.
    However, because of neutrino oscillations, we know that it is non-zero.


    Can it be possible that the mass of an electron neutrino
    Is never the same?, unlike dirac particles.

    that the 3 different flavors are simply 3 different ranges in which
    the mass of the neutrino may be? But not a fixed value, like a photon
    or electron? Or even c? (the probability mass range distribution.)

    if there masses oscillates, that already means they move at variable speeds!

    is a neutrinoless double beta decay observation the only way to conclude
    that we are talking of mayorana particles?

    r.y

    [[Mod. note -- I believe that we know there are (at least) 3 mass
    eigenstates which are stable (they do not oscillate); the 3 known
    neutrino flavors are mixtures of these mass eigenstates.
    -- jt]]

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  • From Tom Roberts@21:1/5 to raymond.yohros@gmail.com on Fri Mar 27 08:16:59 2020
    On 3/26/20 12:44 AM, raymond.yohros@gmail.com wrote:
    Why then can we not determine what % of the speed of light
    the [neutrinos] where traveling at and with some algebra as usual
    determine their masses as well?

    The resolution in measuring their speed is too poor to distinguish it
    from c, by many orders of magnitude. So their mass cannot be determined
    from their speed. And as the moderator mentioned, one would also need to
    know the energy of the neutrinos.

    Also, KATRIN did not actually measure the mass of the electron neutrino,
    they only put an upper limit of 1.1 eV on it. They may be able to reduce
    that somewhat, but it is a very challenging measurement.

    Note that neutrino oscillation measurements imply nonzero but much
    smaller mass differences between the different neutrino mass
    eigenstates; they cannot determine the mass of any of them.

    Tom Roberts

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  • From Phillip Helbig (undress to reply@21:1/5 to helbig@asclothestro.multivax.de on Fri Mar 27 08:17:00 2020
    In article <r5ijjk$16a$1@gioia.aioe.org>, "Phillip Helbig (undress to
    reply)" <helbig@asclothestro.multivax.de> writes:

    Note that neutrinos from the supernova 1987A in the Large Magellanic
    Cloud emitted neutrinos which were detected on Earth. Since the
    difference in emission times of light and neutrinos is only about 3
    hours, this is negligible for the travel time of 157,000 years and thus provides a good lower limit on the speed of neutrinos (i.e. very close
    to the speed of light). This gives an upper limit on the mass of the electron neutrino of about 26 eV. Current limits are about 0.11 eV.
    However, because of neutrino oscillations, we know that it is non-zero.

    [[Mod. note -- To amplify one point Phillip made: measurements of neutrino oscillations tell us the *difference* between the *squares* of the masses
    of different types of neutrinos, i.e., they tell us something like
    m1**2 - m2**2 . But if my dim recollection is correct, they don't
    easily tell us which of the 3 types of neutrinos m1 and m2 refer to.
    -- jt]]

    I now see that what I wrote is somewhat confusing. The only sentence
    which refers to neutrino oscillations is the very last one, added to
    emphasize the point that while upper limits have been decreasing, unlike
    the mass of the photon or graviton it is ruled out that the mass of the neutrino could be exactly zero, because of neutrino oscillations, even
    there is no lower limit on the mass from more-direct measurements of the
    mass. As Jonathan mentioned, they tell us something about the
    differences of the squares of the masses, not the masses themselves.
    (I'm not absolutely sure that the case of one massless and two massive neutrinos is not allowed, but I think that the implication is that all
    three types have a non-zero mass.)

    With regard to the time-of-flight measurements from supernova 1987A,
    note that massless neutrinos would all have the same time of flight,
    even with different energies. With a mass, different energies would
    lead to differences in the times of flight. The measured spread on
    arrival times can put an upper limit on the mass.

    While probably most expect the electron neutrino to be the lightest and
    the tau neutrino the heaviest, like the corresponding charged particles, apparently an inverted mass hierarchy is possible, with some other
    ordering. In other words, we don't know if the electron neutrino is necessarily the lightest one.

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  • From Ned Latham@21:1/5 to Tom Roberts on Sun Mar 29 07:58:38 2020
    Tom Roberts wrote:
    raymond.yohros wrote:

    Why then can we not determine what % of the speed of light
    the [neutrinos] where traveling at and with some algebra as usual
    determine their masses as well?

    The resolution in measuring their speed is too poor to distinguish it
    from c, by many orders of magnitude. So their mass cannot be determined
    from their speed. And as the moderator mentioned, one would also need to
    know the energy of the neutrinos.

    Also, KATRIN did not actually measure the mass of the electron neutrino,
    they only put an upper limit of 1.1 eV on it. They may be able to reduce
    that somewhat, but it is a very challenging measurement.

    Note that neutrino oscillation measurements imply nonzero

    Which in turn implies irregularity of shape?

    but much smaller mass differences between the different neutrino
    mass eigenstates;

    Three masses gives two differences; is there anything like an integral
    common denominator?

    they cannot determine the mass of any of them.

    So how are the differences determined?

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  • From Michael Moroney@21:1/5 to Ned Latham on Sun Mar 29 15:47:35 2020
    Ned Latham <nedlatham@internode.on.net> writes:

    Tom Roberts wrote:

    but much smaller mass differences between the different neutrino
    mass eigenstates;

    Three masses gives two differences; is there anything like an integral
    common denominator?

    Differences between the SQUARES of the masses. And there are three pairs of squares of mass differences.

    Three equations and three unknowns, in theory this should be solvable or at least reduced to a degenerate.

    Is it possible for exactly one of the eigenstates, or exactly one neutrino mass to be exactly 0, or do all 3 need nonzero mass?

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  • From Michael Moroney@21:1/5 to Tom Roberts on Sun Mar 29 21:43:28 2020
    Tom Roberts <tjroberts137@sbcglobal.net> writes:

    On 3/26/20 12:44 AM, raymond.yohros@gmail.com wrote:
    Why then can we not determine what % of the speed of light
    the [neutrinos] where traveling at and with some algebra as usual
    determine their masses as well?

    The resolution in measuring their speed is too poor to distinguish it
    from c, by many orders of magnitude. So their mass cannot be determined
    from their speed. And as the moderator mentioned, one would also need to
    know the energy of the neutrinos.

    Re SN 1987A, what is believed to be the reaction(s) which produce the
    majority of its neutrinos? What is the energy of those neutrinos?

    Assuming the SN1987A progenitor is relatively stationary wrt us, and
    from the time between neutrino detection and visible evidence of the
    supernova, we know the neutrinos must be going at very close to c.
    However, there should be an estimate of their minimum speed (still
    nearly c, of course, and from that we should be able to determine the
    minimum gamma of the neutrinos from our reference. From that and the
    estimated energy of the neutrinos, we should be able to put an upper
    limit on their masses, and it would have to be very small for such a
    large gamma. I assume this has been done, correct? Or does neutrino oscillation throw everything off?

    Speaking of which, I don't see how a neutrino could convert to a
    different type with a different mass without violating conservation of
    energy, momentum or both. What is happening with this?

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  • From raymond.yohros@gmail.com@21:1/5 to Michael Moroney on Mon Mar 30 20:57:22 2020
    On Sunday, March 29, 2020 at 3:43:29 PM UTC-5, Michael Moroney wrote:
    Speaking of which, I don't see how a neutrino could convert to a
    different type with a different mass without violating conservation of energy, momentum or both. What is happening with this?

    and the irony is that conservation laws are the reason they
    where discovered!

    I'm sure it has something to do with distance,temperature and the medium
    they travel, and again, conservation laws will give us the clue once
    again. It is all part of solving the vacuum catastrophe, our current
    crisis in physics

    r.y

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  • From Ned Latham@21:1/5 to Michael Moroney on Mon Mar 30 22:27:50 2020
    [[Mod. note -- I apologise for the delay in processing this article,
    which the author posted on Sunday 2020-03-29.
    -- jt]]

    Michael Moroney wrote:
    Ned Latham <nedlatham@internode.on.net> writes:
    Tom Roberts wrote:

    but much smaller mass differences between the different neutrino
    mass eigenstates;

    Three masses gives two differences; is there anything like an integral common denominator?

    Differences between the SQUARES of the masses.

    There have to be differences of the square roots of the squares too.

    And there are three pairs of squares of mass differences.

    You're right. I have no idea how I did that.

    Three equations and three unknowns, in theory this should be solvable
    or at least reduced to a degenerate.

    Is it possible for exactly one of the eigenstates, or exactly one
    neutrino mass to be exactly 0, or do all 3 need nonzero mass?

    You know my opinion on that. They must all be non-zero.

    There is still the question of whether there is an integral common
    denominator.

    [[Mod. note -- The neutrino-oscillation observations give information
    (only) on the differences between the squares of the masses.

    We have no reason to expect the masses to be in integer ratios.
    -- jt]]

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  • From raymond.yohros@gmail.com@21:1/5 to Tom Roberts on Mon Mar 30 22:40:10 2020
    On Friday, March 27, 2020 at 3:17:02 AM UTC-5, Tom Roberts wrote:
    On 3/26/20 12:44 AM, raymond.yohros@gmail.com wrote:
    Why then can we not determine what % of the speed of light
    the [neutrinos] where traveling at and with some algebra as usual
    determine their masses as well?

    The resolution in measuring their speed is too poor to distinguish it
    from c, by many orders of magnitude. So their mass cannot be determined
    from their speed. And as the moderator mentioned, one would also need to
    know the energy of the neutrinos.


    Ice cube detected neutrinos in the order of 1 Pev's(bert and ernie)
    and big bird was 2 Pev's!
    That may be around 2 magnitude orders higher than protons
    spinning on the LHC!

    of course the sources and flight times of these cosmic
    neutrinos where undetermined but there are clues about where
    In the sky they may have come to point telescopes.
    one of those may have been a blazar, PKS B1424-418

    The point i tried to make in my second post was that we
    may be tempted to think that their masses may not be
    fixed values beside their 3 stable eigenstates.

    And this is not the first time we observe something like this in nature
    You may say that a z bosons may be 91.19 Gev/c2
    But you can find them at other values with less probabilities!

    Flying at variable speeds, variable mass distributions,
    Fermions but with some bosonic characteristics, this
    Particles truly hold the answers to the best
    question we can ask.

    cheers
    r.y

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  • From Phillip Helbig (undress to reply@21:1/5 to raymond.yohros@gmail.com on Tue Mar 31 09:14:19 2020
    In article <693dc170-665b-478d-b351-3c543da09c36@googlegroups.com>, raymond.yohros@gmail.com writes:

    On Sunday, March 29, 2020 at 3:43:29 PM UTC-5, Michael Moroney wrote:
    Speaking of which, I don't see how a neutrino could convert to a
    different type with a different mass without violating conservation of
    energy, momentum or both. What is happening with this?

    It's a difficult concept, but not unknown in particle physics. Observed particles can be mixtures of other particles, and the state of the
    mixture can changed during propagation, so it's not like one type of
    neutrino can change into another (which would indeed be forbidden by conservation laws).

    and the irony is that conservation laws are the reason they
    where discovered!

    Isaac Asimov wrote a book on the neutrino. The neutrino makes its
    introduction about halfway through the book. The first half is about conservation laws.

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  • From Hendrik van Hees@21:1/5 to All on Tue Mar 31 17:17:58 2020
    On 31/03/2020 11:14, Phillip Helbig (undress to reply) wrote:
    In article <693dc170-665b-478d-b351-3c543da09c36@googlegroups.com>, raymond.yohros@gmail.com writes:

    On Sunday, March 29, 2020 at 3:43:29 PM UTC-5, Michael Moroney wrote:
    Speaking of which, I don't see how a neutrino could convert to a
    different type with a different mass without violating conservation of
    energy, momentum or both. What is happening with this?

    It's a difficult concept, but not unknown in particle physics. Observed particles can be mixtures of other particles, and the state of the
    mixture can changed during propagation, so it's not like one type of
    neutrino can change into another (which would indeed be forbidden by conservation laws).

    and the irony is that conservation laws are the reason they
    where discovered!

    Isaac Asimov wrote a book on the neutrino. The neutrino makes its introduction about halfway through the book. The first half is about conservation laws.

    It's indeed a not so easy concept, and it's not so easy to find an
    entirely correct treatment in the literature. First of all of course
    mixing means that the "type of neutrino" changes. To understand in which
    sense one needs a bit of QFT background.

    First of all one has to remember that the identification of certain
    states of a quantum field, the socalled one-particle Fock states, as
    particles apply only to (asymptotic) free fields. These are spanned by
    the one-particle states of definite momentum, mass and spin (or for
    massless particles helicity). Thus only mass eigenstates are
    interpretible as particles which are sufficiently far away from other
    particles they interact with ("asymptotic free states").

    Interacting QFT lets you calculate transition rates from one initial
    asymptotic free state (usually two particles) to another final
    asymptotic free state (where you can have, of course, any number of
    newly created particles as far as the corresponding reaction is allowed
    by the conservation laws).

    Now neutrinos are the uncharged leptons and thus take part in the
    electroweak but not the strong interaction. The electroweak interaction
    within the Standard Model is described by a chiral gauge theory, and in
    the Standard Model the neutrinos are treated as massless Dirac
    particles, of which only the left-handed part interacts via the weak interaction.

    Now with the discovery of neutrino oscillations this is not entirely
    correct anymore, and one has to extend the Standard Model. The
    implication of neutrino mixing is that first of all at least two of the
    three neutrino states must get massive and second that the neutrino
    flavor eigenstates are not the neurtino-mass eigenstates.

    In consequence strictly speaking you cannot directly observe neutrinos
    but only via the reaction of neutrinos with other directly observable particles. This is because, the neutrinos are created in flavor
    eigenstates, e.g., by the decay of muons to muon neutrinos + something
    else (nearly 100% decay channel is mu->e+\bar{\nu}_e + \nu_{\mu}). These
    are not the mass eigenstates and thus on their propagation they
    oscillate between the different flavor eigenstates, and you can only
    observe them by some reaction in the detector material via other
    particles. The reaction is again in a flavor eigenstate through the weak interaction. Due to the oscillation you have some probability to detect
    each of the three flavors, and this probability is determined by the
    distance between the source and the detector ("long baseline
    experiments") and the mixing matrix (a unitary matrix, called the Pontecorvo---Maki---Nakagawa---Sakata matrix which describes the
    transformation between mass- and flavor-eigenstates.

    This is in close analogy with the quark-mixing matrix (the Cabibbo-Kobayashi-Maskawa), where also the d-, s-, b- flavor eigenstates
    are not the same as the mass eigenstates. As there you also have
    CP-violating phases for the neutrinos. The difference is that in contradistinction to the charged quarks, which are clearly Dirac
    fermions, the neutral neutrinos could well be also Majorana particles,
    i.e., they could be "strictly neutral" and thus their own antiparticles.
    In this case there are two more CP-violating phases. Whether or not this
    is the case or whether or not the neutrino-mixing matrix violates CP is
    not yet known. Also the neutrino masses are not well known.

    For an effective description of neutrino oscillations, see the Wikipedia article:

    https://en.wikipedia.org/wiki/Neutrino_oscillation

    but be aware that this is an effective description, which doesn't take
    into account the above mentioned quantum-field theoretical
    creation-detection mechanism which makes everything consistent with both
    energy and (!!!) momentum conservation as in any other scattering
    process. For the full QFT treatment see

    https://arxiv.org/abs/1008.2077

    --
    Hendrik van Hees
    Goethe University (Institute for Theoretical Physics)
    D-60438 Frankfurt am Main
    http://fias.uni-frankfurt.de/~hees/

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  • From Tom Roberts@21:1/5 to Michael Moroney on Wed Apr 1 07:36:27 2020
    On 3/29/20 3:43 PM, Michael Moroney wrote:
    Re SN 1987A, what is believed to be the reaction(s) which produce the majority of its neutrinos? What is the energy of those neutrinos?

    The usual suspects: nuclear interactions giving neutrinos of a few MeV,
    and particle decays that can be either lower or higher energy.

    Assuming the SN1987A progenitor is relatively stationary wrt us, and
    from the time between neutrino detection and visible evidence of the supernova, we know the neutrinos must be going at very close to c.
    However, there should be an estimate of their minimum speed (still
    nearly c, of course, and from that we should be able to determine the
    minimum gamma of the neutrinos from our reference. From that and the estimated energy of the neutrinos, we should be able to put an upper
    limit on their masses, and it would have to be very small for such a
    large gamma. I assume this has been done, correct? Or does neutrino oscillation throw everything off?

    The difficulty is understanding the astrophysical processes that emit
    the neutrinos,and those that emit the light. The neutrinos were detected
    BEFORE the light from SN1987A, so the astrophysical processes dominate
    the time difference, not slower propagation due to nonzero neutrino mass.

    By applying a common astrophysical model, Arnett and Rosner calculate an
    upper bound on neutrino mass of 12 eV [Arnett and Rosner, PRL _58_
    (1987), p1906]. That is significantly higher than other experiments'
    upper limits. And the uncertainty in the astrophysics involved is large.

    Speaking of which, I don't see how a neutrino could convert to a
    different type with a different mass without violating conservation of energy, momentum or both. What is happening with this?

    Neutrino oscillation is not a "conversion". Rather it is the usual
    quantum mechanical process of projecting a wavefunction onto different
    basis eigenstates. When the weak interaction creates a neutrino, it is
    created in a "flavor eigenstate" -- either nu_e, nu_mu, or nu_tau
    (electron, muon, and tau neutrino). But those are not the same as the
    "mass eigenstates" (which are better called "eigenstates of the
    propagation Hamiltonian"). These latter eigenstates describe how the wavefunction (amplitude) propagates. Each mass eigenstate has nonzero
    overlap with each flavor eigenstate, but with different factors, so each
    flavor eigenstate has different fractions of the mass eigenstates. Since
    the mass eigenstates have different masses, their amplitudes vary in
    space along the propagation direction with different wavelengths (this
    is the usual rotation of their complex phase). This would be
    unobservable by itself, but when the neutrino interacts in the detector,
    it does so as a flavor eigenstate, and the different mass eigenstates in
    the wavefunction interfere, giving a different amplitude for the flavor eigenstates than when it was created. That difference is a function of
    which flavors are involved, the distance between creation and detection,
    and the energy of the neutrino -- measurements on earth over several
    hundred kilometers can provide considerable detail of the process
    because the neutrino beam has a range of energies.

    As for conservation of 4-momentum, remember that in QM no wavefunction
    is perfectly sharp. The creation interaction expressed as a flavor
    eigenstate has sufficient indeterminacy in 4-momentum to have nonzero
    overlaps with each of the mass eigenstates. Each mass eigenstate
    propagates independently, conserving 4-momentum. Since their amplitudes
    vary differently in space, and the flavor eigenstates have different
    fractions to the mass eigenstates, at the detector the overlap with
    flavor eigenstates is different from what it was at creation. So at
    creation the neutrino had a definite flavor, but at the detector it has
    nonzero amplitude to be each of the three flavors; for a given neutrino
    the detector will see only one of them, but for the beam there will be a distributions of all three flavors, even if the beam was all created as
    a single flavor.

    Tom Roberts

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  • From Jos Bergervoet@21:1/5 to All on Wed Apr 1 22:38:59 2020
    On 20/03/31 6:17 PM, Hendrik van Hees wrote:
    ...> Now neutrinos are the uncharged leptons and thus take part in the
    electroweak but not the strong interaction. The electroweak interaction within the Standard Model is described by a chiral gauge theory, and in
    the Standard Model the neutrinos are treated as massless Dirac
    particles, of which only the left-handed part interacts via the weak interaction.

    Now with the discovery of neutrino oscillations this is not entirely
    correct anymore, and one has to extend the Standard Model. The
    implication of neutrino mixing is that first of all at least two of the
    three neutrino states must get massive and second that the neutrino
    flavor eigenstates are not the neutrino-mass eigenstates.

    And do you think the right-handed part will still not be interacting?

    What does that mean for neutrinos standing still? Or more precisely,
    neutrino fields at energies much lower than their mass? Is there a kind
    of 'electroweak-static' theory, like we have classical electrostatics
    for QED with the electrons at much lower energy than their mass?

    --
    Jos

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  • From Michael Moroney@21:1/5 to Tom Roberts on Thu Apr 2 08:00:54 2020
    Tom Roberts <tjroberts137@sbcglobal.net> writes:

    On 3/29/20 3:43 PM, Michael Moroney wrote:
    Re SN 1987A, what is believed to be the reaction(s) which produce the
    majority of its neutrinos? What is the energy of those neutrinos?

    The usual suspects: nuclear interactions giving neutrinos of a few MeV,
    and particle decays that can be either lower or higher energy.

    I was wondering if a oarticular reaction of a certain energy dominated.
    I know the general idea behind the formation of a neutron star was that
    p + e = n + nu, but was there a particular energy or energy range most
    of the neutrinos would have, particularly if most of the protons may be
    protons in iron nuclei or something.

    Assuming the SN1987A progenitor is relatively stationary wrt us, and
    from the time between neutrino detection and visible evidence of the
    supernova, we know the neutrinos must be going at very close to c.
    However, there should be an estimate of their minimum speed (still
    nearly c, of course, and from that we should be able to determine the
    minimum gamma of the neutrinos from our reference. From that and the
    estimated energy of the neutrinos, we should be able to put an upper
    limit on their masses, and it would have to be very small for such a
    large gamma. I assume this has been done, correct? Or does neutrino
    oscillation throw everything off?

    The difficulty is understanding the astrophysical processes that emit
    the neutrinos,and those that emit the light. The neutrinos were detected >BEFORE the light from SN1987A, so the astrophysical processes dominate
    the time difference, not slower propagation due to nonzero neutrino mass.

    By applying a common astrophysical model, Arnett and Rosner calculate an >upper bound on neutrino mass of 12 eV [Arnett and Rosner, PRL _58_
    (1987), p1906]. That is significantly higher than other experiments'
    upper limits. And the uncertainty in the astrophysics involved is large.

    OK. So this was done but answers from other methods are better.

    Speaking of which, I don't see how a neutrino could convert to a
    different type with a different mass without violating conservation of
    energy, momentum or both. What is happening with this?

    Neutrino oscillation is not a "conversion". Rather it is the usual
    quantum mechanical process of projecting a wavefunction onto different
    basis eigenstates. When the weak interaction creates a neutrino, it is >created in a "flavor eigenstate" -- either nu_e, nu_mu, or nu_tau
    (electron, muon, and tau neutrino). But those are not the same as the
    "mass eigenstates" (which are better called "eigenstates of the
    propagation Hamiltonian"). These latter eigenstates describe how the >wavefunction (amplitude) propagates. Each mass eigenstate has nonzero
    overlap with each flavor eigenstate, but with different factors, so each >flavor eigenstate has different fractions of the mass eigenstates. Since
    the mass eigenstates have different masses, their amplitudes vary in
    space along the propagation direction with different wavelengths (this
    is the usual rotation of their complex phase). This would be
    unobservable by itself, but when the neutrino interacts in the detector,
    it does so as a flavor eigenstate, and the different mass eigenstates in
    the wavefunction interfere, giving a different amplitude for the flavor >eigenstates than when it was created. That difference is a function of
    which flavors are involved, the distance between creation and detection,
    and the energy of the neutrino -- measurements on earth over several
    hundred kilometers can provide considerable detail of the process
    because the neutrino beam has a range of energies.

    OK, so this is better thought of like Schrodinger's cat. You don't know
    if the cat is dead or alive until you open the box. And you can't claim
    the neutrino starts off as an electron neutrino, becomes a muon neutrino
    then an electron neutrino then interacts as a tau neutrino, but you can
    only say it has odds of X, Y and Z of interacting as each type and
    actually does interact as one type. This is the same idea as if you
    sent a single photon to a double slit, it has odds of showing up at
    certain places on the far side, but can actually show up at only one
    spot.

    Correct?

    As for conservation of 4-momentum, remember that in QM no wavefunction
    is perfectly sharp. The creation interaction expressed as a flavor
    eigenstate has sufficient indeterminacy in 4-momentum to have nonzero >overlaps with each of the mass eigenstates. Each mass eigenstate
    propagates independently, conserving 4-momentum. Since their amplitudes
    vary differently in space, and the flavor eigenstates have different >fractions to the mass eigenstates, at the detector the overlap with
    flavor eigenstates is different from what it was at creation. So at
    creation the neutrino had a definite flavor, but at the detector it has >nonzero amplitude to be each of the three flavors; for a given neutrino
    the detector will see only one of them, but for the beam there will be a >distributions of all three flavors, even if the beam was all created as
    a single flavor.

    OK. But still if a bunch of electron neutrinos gets created and some
    interact as tau neutrinos of a different mass, doesn't that still mean
    that one or the other of energy and momentum must be different in the interaction? Or that's "OK" because of the uncertainty involved?

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  • From Michael Moroney@21:1/5 to All on Sat Apr 4 17:42:34 2020
    I have an addition question about neutrino oscillation.

    If you look at the article
    https://en.wikipedia.org/wiki/Neutrino_oscillation and the last three
    images under "Three neutrino probabilities" it shows the odds of
    detection as a particular type, as a function of distance/energy when
    they are created as a particular type. Of course very close to the
    origin it is very likely the original type. However for the three charts
    they cycle through the probabilities the odds are generally higher they
    will be detected as their original type. Meaning they "remember" what
    they were created as?

    Also the (black) electron type curve is "different" from the muon/tau
    types (red/blue). Can we 'conclude' anything from this, perhaps the
    muon/tau neutrinos have a similar mass to each other and the electron
    type is rather different from them?

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