What is Neutrino mass: Definition and 31 Discussions

A neutrino ( or ) (denoted by the Greek letter ν) is a fermion (an elementary particle with spin of 1/2) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small (-ino) that it was long thought to be zero. The rest mass of the neutrino is much smaller than that of the other known elementary particles excluding massless particles. The weak force has a very short range, the gravitational interaction is extremely weak, and neutrinos do not participate in the strong interaction. Thus, neutrinos typically pass through normal matter unimpeded and undetected.Weak interactions create neutrinos in one of three leptonic flavors: electron neutrinos (νe), muon neutrinos (νμ), or tau neutrinos (ντ), in association with the corresponding charged lepton. Although neutrinos were long believed to be massless, it is now known that there are three discrete neutrino masses with different tiny values, but they do not correspond uniquely to the three flavors. A neutrino created with a specific flavor has an associated specific quantum superposition of all three mass states. As a result, neutrinos oscillate between different flavors in flight. For example, an electron neutrino produced in a beta decay reaction may interact in a distant detector as a muon or tau neutrino. Although only differences between squares of the three mass values are known as of 2019, cosmological observations imply that the sum of the three masses (< 2.14 × 10−37 kg) must be less than one millionth that of the electron mass (9.11 × 10−31 kg).For each neutrino, there also exists a corresponding antiparticle, called an antineutrino, which also has spin of 1/2 and no electric charge. Antineutrinos are distinguished from the neutrinos by having opposite signs of lepton number and right-handed instead of left-handed chirality. To conserve total lepton number (in nuclear beta decay), electron neutrinos only appear together with positrons (anti-electrons) or electron-antineutrinos, whereas electron antineutrinos only appear with electrons or electron neutrinos.Neutrinos are created by various radioactive decays; the following list is not exhaustive, but includes some of those processes:

beta decay of atomic nuclei or hadrons,
natural nuclear reactions such as those that take place in the core of a star
artificial nuclear reactions in nuclear reactors, nuclear bombs, or particle accelerators
during a supernova
during the spin-down of a neutron star
when cosmic rays or accelerated particle beams strike atoms.The majority of neutrinos which are detected about the Earth are from nuclear reactions inside the Sun. At the surface of the Earth, the flux is about 65 billion (6.5×1010) solar neutrinos, per second per square centimeter. Neutrinos can be used for tomography of the interior of the earth.Research is intense in the hunt to elucidate the essential nature of neutrinos, with aspirations of finding:

the three neutrino mass values
the degree of CP violation in the leptonic sector (which may lead to leptogenesis)
evidence of physics which might break the Standard Model of particle physics, such as neutrinoless double beta decay, which would be evidence for violation of lepton number conservation.

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  1. strangerep

    A Proof that neutrino flavor oscillation implies nonzero neutrino mass?

    [This is a reference request.] I'm dissatisfied with the "proofs" I've found so far. E.g., in Kayser's review from 2008, in the paragraph following his eq(1.4), he assumes a propagation amplitude Prop##(\nu_i)## of ##\exp(-im_i \tau_i)##, where "##m_i## is the mass of the ##\nu_i## and...
  2. mfb

    I New cosmological neutrino mass constraint: sum<0.09 eV at 95% CL

    arXiv: On the most constraining cosmological neutrino mass bounds From neutrino mixing we know that an inverted order (two "heavy" neutrinos, one light neutrino) needs a sum of masses of at least ~0.09 eV, while the normal order (two light, one "heavy") can have a sum as low as ~0.05 eV. The...
  3. Arman777

    A N-body simulation with varying neutrino mass

    I am trying to find a picture of the N-body simulations that shows the LSS. Particularly I am looking for different neutrino masses without the CDM. For instance pictures likes this But with more varying/different neutrino masses. I am looking for articles
  4. Arman777

    I Calculating the Maximum total neutrino mass by using cosmological boun

    In an article its written, $$\Omega_{\nu} = \frac{\rho_{\nu}}{\rho_{crit}}=\frac{\sum m_{i,\nu}n_{i,\nu}}{\rho_{crit}} = \frac{\sum m_{\nu}}{93.14h^2eV}$$ Now I am trying to derive this for myself but I could not. Can someone help me ? So the values are, ##\rho_{crit} = 1.053 75 \times...
  5. E

    A Future of the electron neutrino mass limits

    In five years also experiment KATRIN will give either the upper bound of electron neutrino mass (0,2 eV) or even the mass of the electron neutrino. https://www.katrin.kit.edu/ My question is, what we can expect from the astronomical and non-astronomical measurements to improve these data? I...
  6. K

    I Neutrino Mass: Exploring the Oscillation Phenomenon

    Why is there an assumption that if neutrinos didn't have mass they would move at the speed of light? and how does the fact they oscillate prove they have mass?
  7. mollwollfumble

    A My T-shirt and the Standard Model

    This T-shirt I bought at a physics conference displays the following equation. It looks like the Lagrangian of the Standard Model of particle physics but I only recognise lines 1 (electroweak) and 3 (Higgs mechanism). What are lines 2 and 4 and what is/isn't included? eg. are quarks, gluons...
  8. Riotto

    A What are singular and double seesaw?

    I have just started reading about neutrino physics and recently came across two terms called double seesaw and singular seesaw. Although I’m familiar with other seesaw mechanisms (such as type-I and II) for explaining smallness of neutrino mass. I’m completely at dark about double and singular...
  9. T

    I Neutrino Mass, Baryogenesis, Dark Matter (Beyond the SM)

    Hello, So I am aware that neutrino masses, Baryogengesis/Baryon Asymmetry, and Dark matter cannot be explained by the standard model. However each can be explained by right handed neutrinos. I know that right handed neutrinos show up in many extensions to the standard model, e.g. vMSM (where...
  10. C

    A Understanding the Mass of the Higgs Triplet in Neutrino Mass Mechanism

    Hi, I would like to understand what is the MΔ which appears in the neutrino mass mechanism with Type-II seesaw. It seems to be the Higgs triplet mass. But I do not understand what is (physically) the masse of this triplet when we define it with 3 components : Δ=(Δ++,Δ+,Δ°). It is different from...
  11. V

    A Understanding the Seesaw Formula Conventions in Neutrino Mass Derivations

    ok so this is a bit of a boring question, so sorry in advance, but for some reason I am struggling with this. I am deriving the seesaw formula. Now I have gone through the derivivate and I get A : ## m_{\nu} = - m_D^T M^{-1} m_D ## Now I have seen other derivations where they get B ...
  12. F

    I How can photons interact if they travel at the speed of ligh

    I was listening to a podcast about the solar neutrino problem, and they discussed how we have deduced that neutrinos are not massless due to the fact that they interact with other particles (even if this interaction occurs rarely). I paraphrase: "a particle traveling at the speed of light is...
  13. T

    What percentage of the universe's mass is contributed by neutrinos?

    What percentage of the total mass of the universe ( byaronic + dark matter and dark energy) is contributed by the neutrino..?? Maybe by relic neutrinos...most of the time I find 340 relic neutrinos per cm3 in website ...should I take account for the neutrinos produced by all the burning...
  14. Anchovy

    Neutrino mass state = flavour state, but how come?

    I understand the basics of neutrino oscillation from the starting point of each neutrino flavour state being a superposition of mass states, or vice versa. However, the introductory texts I've seen never seem to explain what motivated such an idea. What made Pontecorvo think this?
  15. GeorgeDishman

    When did relic neutrinos cease being relativistic?

    Relic neutrinos decoupled from matter around the time of nucleogenesis so had the same temperature as matter and photons at that time. Photons decoupled much later, after electron/positron annihilation which heated the photons slightly so thereafter neutrino temperature should be (4/11)^(1/3)...
  16. PeterDonis

    Negative Neutrino Mass Squared: Accepted Paper Analysis

    I just came across this paper arguing that the electron neutrino may have negative mass squared: http://arxiv.org/abs/1408.2804 It says it has been accepted for publication. I'm wondering if anyone has seen it and can comment on the paper's arguments.
  17. D

    Can the Higgs Boson Help Solve the Mystery of Neutrino Mass?

    In reading through all the info that is coming out from today's big announcement, it seems as they still can't peg the mass of the higgs boson as much of their data comes in the form of decay paths that include neutrinos of unknown mass. My question is whether when they peg the exact mass of...
  18. R

    Loop-level corrections to the neutrino mass

    Hi, Quick question. In the SM, why can't we have loop-level interactions that give neutrinos their small masses? (It seems like we must also have Majorana neutrinos)Thanks.
  19. M

    Can Neutrino Mass Eigenstates Ever Change into Other Mass Eigenstates?

    Hi, We know that when we have one flavour of neutrino, it can change into another flavour by neutrino oscillations. However, if we consider a mass eigenstate, then is it true that it can never change into a different mass eigenstate? In other words is a |v_{1}> neutrino forever a |v_{1}>? I...
  20. G

    Understanding Neutrino Mass and its Impact on Beta Decay Observations

    when beta decay is observed it is noticed that some of the energy and some of the momentum is missing. it is thought that this missing energy and momentum is carried away by a neutrino. the neutrino mass is still unknown. if you know how much momentum (mv) is missing and you know how much...
  21. T

    Can neutrino mass eigenstate couple to the group of SU(2)

    can the neutrino mass eigenstate couple to the group of SU(2) doublet?if we intentionally not impose any flavor symmetry on it. \left(\begin{array}{c}\nu_{1}\\e\end{array}\right)
  22. A

    Question Concerning Neutrino Mass Hierarchy

    I've been reading up on neutrino oscillations and I have come across this issue. I know that oscillations are dependent on the mass squared differences of the mass eigenstates, which is why determining things like the absolute masses of the eigenstates and the hierarchy of the eigenstates is...
  23. R

    How Does the Dirac Conjugation Operator Affect Majorana Neutrino Mass Terms?

    In books I find that the Majorana mass term for the neutrinos is given by m_L \nu_L^T C^\dagger \nu where C is Dirac Conjugation operator. How does C look like if I write \nu_L as in terms of its two components \left(\begin{array} (\nu_{L1} \\ \nu_{L2} \end{array} \right)? Is C=...
  24. D

    Neutrino Oscillation <-> Neutrino Mass

    Wikipedia says that the phenomenon of Neutrino Oscillation implies that the neutrino has a non-zero mass (http://en.wikipedia.org/wiki/Neutrino_oscillation" ). Why is that? Why is it that Neutrino Oscillation can only exist, if neutrinos do have mass?
  25. humanino

    What are the implications of neutrino mass on the universe?

    Hi everyone, I have always been very worried about the possible consequences of neutrino masses. I just came accros a paper which I thought I would share with you. First, the reference : Neutrino mass and mixing implied by underground deficit of low energy muon-neutrino events John G...
  26. I

    Calculating Muon Momentum with Finite Neutrino Mass

    Homework Statement in the decay process, \pi ^{+} -> \mu^{+} + \nu_{\mu} show that for a neutrino of finite (but small) mass, compared with the case of the massless neutrino, the muon momentum would be reduced by the fraction: \frac{p'}{p}= - \frac{m_{\nu}^2...
  27. T

    Measuring Neutrino Mass from a Supernova

    I tried and I got a ridiculous large number for the neutrino mass. I basically used E=\gamma m c and then, for 10 MeV neutrinos, time taken is t + 10 seconds to reach Earth, for 50 MeV neutrinos, time taken is t seconds. Speed = \frac{100 000}{(t+10)} for 10 MeV and Speed = \frac{100 000}{t}...
  28. B

    So does the Higg field give the neutrino mass, and can neutrino velocity change?

    so does the Higg field give the neutrino mass, and can neutrino velocity change? how close to c is neutrino velocity?
  29. F

    How Is the Lower Bound of Neutrino Mass Calculated?

    I was wondering if anyone could help clarify this problem I am having. Upon reading a section in a paper, I am a bit stuck as to how this value of the lower bound of the neutrino mass is reached here. I have highlighted the relevant part in the snapshot...
  30. J

    Neutrino Oscillations and Mass: A Comprehensive Review

    I am in my senior year of undergrad studies and would like to read a research paper on the NEUTRINO MASS. I am hoping for it to be at a level which I can understand. I am taking particle physics right now. Are there any sites that would offer such documents? James
  31. curious george

    Estimating a neutrino mass upper limit from supernova data

    I'd appreciate it if I could get a little help on this one, I'm confused about how this is done. I know there are numerous papers out there about how to do this based on the SN1987A event that was detected with KII and IMB. The problem in my textbook asks me to make a rough estimate of the...