Neutrinos Definition and 106 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. Zuzana

    A Atmospheric electron neutrinos

    Hi, I would like to ask question about atmospheric electron neutrinos. It is known that atmospheric electron neutrinos originate from the decay of muon in the atmosphere, but we can also calculate that muon with energy more than 10 GeV is able to penetrate about 100 km, so it does not decay and...
  2. fresh_42

    I Neutrino detection at Cern And here is the pop science summary: Which results can be expected?
  3. G

    Photon and Neutrino detector and photon trawl device

    Summary:: Hello I am a writer and presently working on treatment for a science-fiction story. So I am not a scientist, just a neophyte interested in science and wanting to write a fiction that would not be too far-fetched and that would make some sense for everyone, including the scientific...
  4. Physics4Eva

    I Neutrino Confusion

    I was looking into neutrinos and found that a man named Ettore Majorana proposed neutrinos and antineutrinos are the same thing. If this could be true, antineutrinos emitted during double beta decay could annihilate one another and vanish. However, this would violate lepton number conservation...
  5. J

    A Why do we write that there are no right-handed neutrinos?

    I'm puzzled why, now that we know that neutrinos have mass, we still read that there are only left-handed neutrinos, as far as we know. I understand that right-handed neutrinos do not interact by the weak force, so we would not detect them. My question is why we read that they might not /...
  6. jim mcnamara

    I MiniBooNE results at 6.1 sigma: Potential evidence for sterile neutrinos

    Bee Hossenfelder's blog has a discussion: Preprint: New evidence in the search for the 'sterile' neutrino. Can someone comment on this please. @mfb
  7. K

    I Neutrino mass

    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?
  8. D

    B What particle(s) pass through Earth?

    What particles(s) can pass through hundreds of miles of the Earth? Is it only neutrinos, or is there some other particle(s)?
  9. C

    I Neutrino flavour eigenstates and expansion of the universe

    Neutrinos were flavor eigenstates at the time of their decoupling from baryonic matter. Since they were not pure mass eigenstates, how do you take this fact into account if you try to study how they evolved as the universe expanded? Could we determine if the heaviest neutrino could be non...
  10. M

    I Neutrinos interact with photon in "level tree"?

    i found reading the possible interaction of neutrinos with photons to not "level tree", what's the meaning of level tree? and how is that posibble ?
  11. W

    B Coordinated galactic bangs instead of big bang

    The theory of cosmology assumes that the universe has been created from a single point by one big bang event. This theory implies processes which exceed the speed of light. <<Mentor note: This post has been edited to remove some content.>>
  12. V

    A Transforming lepton basis to diagonlise charged lepton mass

    To determine the mass of charged leptons, we rotate such that the matrix of yukawa couplings (which gives the mass matrix after EWSB) is diagonal. We also call this flavour basis for neutrinos, because the flavoured neutrinos couple directly to the correspondong flavoured lepton in weak charged...
  13. C

    A Are neutrinos created by pair production

    Assume just for this question that a neutrino has a mass of 1 ev. That is about the energy of an infrared photon with a wavelength of 1 micron. Is it possible for a visible light photon, or a more energetic photon, to create a neutrino-antineutrino pair?
  14. Seanra

    I My lecturer says "Special relativity is absolutely wrong"

    Hi guys In an assignment I wrote for university I was penalised for claiming that FTL neutrinos would violate special relativity. Below is the relevant part of my assignment and the response from my lecturer. Could somebody please explain what he could mean by that because as far as I can...
  15. S

    I How do neutrinos conserve angular momentum?

    I'm learning about beta decay and as I understand in beta decay we get: neutron → proton + electron And since all these have spin 1/2 we have that the conservation of angular momentum is not conserved. The neutrino with spin 1/2 is proposed to also exist in the process to solve this so that...
  16. D

    Neutrino Decoupling Function

    Background: Neutrinos decouple at around 10^10 K (or 1 MeV). This is normally shown as the interaction rate (between neutrinos and electrons) over the hubble constant: Gamma/H = (T/10^10 K)^3 My problem: I have a function which is dependent on the neutrino-electron interaction. But it does...
  17. T

    How would neutrinos affect fusion?

    How would fusion processes be affected, by a background bath / sea of neutrinos ? Would the constant interactions between fusion products, and neutrinos, constantly break apart the fusion products, and so tend to "undo" the fusion?
  18. TerranIV

    Could Dark Matter be composed of neutrons?

    I was thinking about the properties of dark matter - how it doesn't seem to interact with any of the forces of the universe except gravity and I was thinking about how neutrinos also don't have any charge and they don't interact with any other forces except the weak force and gravity. I thought...
  19. P_Ravensorow

    Percentage of Matter, Dark Matter and Baryonic Matter

    How do we know that out of 100 percent, 4.96% is Matter, 0.42% is Neutrinos, approx 25% Dark matter and rest 70% is dark energy. How do we know about these percentages if we don't know how large the universe is? Or are these calculations based on the spaces of the VISIBLE universe? Are Dark...
  20. alemsalem

    What are the highest energy neutrinos moving near earth?

    that can be detected.
  21. K

    Schools Grad Schools for Neutrino Experiment

    Hi everyone. I think for grad school I want to do work on neutrinos. Anyone know of any good and up and coming schools with good faculty working on these experiments? My application should be good, but not great with great grades/research but very average GRE and PGRE scores.
  22. lalo_u

    Right handed neutrino in SM

    I am reading Mohapatra's book: "Massive Neutrinos in Physics and Astrophysics". At the beginning of chapter 7, it is sought expressions where the right neutrino was considered in the Electroweak Standard Model. Everything was fine until I found the expression...
  23. lalo_u

    Right handed neutrino identity

    I am reading Mohapatra's book: "Massive Neutrinos in Physics and Astrophysics". At the beginning of chapter 7, it is sought expressions where the right neutrino was considered in the Electroweak Standard Model. Everything was fine until I found the expression...
  24. R

    Neutrino Communication Problem

    Homework Statement I need some help understanding the following problem: A distant, advanced civilization wishes to make contact with us using neutrinos rather than photons as the transmitting medium to avoid problems of obscuration along the line of sight. Suppose they use an \bar{\nu_e}...
  25. O

    Neutrinos-Antineutrinos in the universe

    Hello everybody, I am a first year physics student and I have a question about neutrinos and antineutrinos. In a beta minus decay we will get an antineutrino, so I assume that Earth 'produces' more antineutrinos. Does it? However from a beta plus we get neutrinos and positrons. So does...
  26. L

    Handedness of neutrinos and antineutrinos

    Could anybody explain why neutrinos have only ever been observed to be left-handed and antineutrinos right-handed? If neutrinos travel slower than light and have mass (albeit very small), as shown by neutrino oscillation experiments, why can neutrinos not change their handedness?
  27. E

    High energy neutrino telescopes

    Hello, I am opening this thread so as to discuss if possible what you believe is the science case of building a neutrino telescope. Being a fanatic in the field , I would like to hear opinions from whoever wants to say about whether it is important to build such a detector and why. Thank you!
  28. C

    What happens to the electron neutrino post beta+ decay?

    In β+ decay a proton releases a positron and an electron neutrino causing the proton to change into a neutron to help balance the nucleus. I am studying advanced PET imaging and trying find a better understanding of the positrons other half. Does it just go on being a normal electron.
  29. marcus

    Weinberg's dark matter idea re fractional cosmic neutrinos

    Weinberg's dark matter idea re "fractional cosmic neutrinos" Goldstone Bosons as Fractional Cosmic Neutrinos Steven Weinberg (Submitted on 8 May 2013) It is suggested that Goldstone bosons may be masquerading as fractional...
  30. W

    Neutrino polarization

    I was reading in my QM book that neutrinos are "essentially left handedly polarized." (Townsend on Page 119) If neutrinos can be polarized, what is oscillating? Do other particles with mass exhibit polarization?
  31. Rlam90

    Neutrinos to probe nuclear structure?

    Do you think it would be possible to use a beam of neutrinos to probe the structure of atomic nuclei? Since they do not interact electronically, they would be useful to study the structure of both neutrons and protons, either through gravitational deflection or weak interactions. Could this...
  32. J

    Estimating Neutrino Flux Density

    1. Problem "Estimate the flux of neutrinos passing through your body per second if the present energy density of neutrinos from the Big Bang is 0.2 MeV/m3. Assume that you are a standard size covering 0.01 m2". Homework Equations nv = Uv(T) / <Ev> The Attempt at a Solution I've assumed that...
  33. xortdsc

    Interaction between Neutrons/Neutrinos

    Hello, I was wondering if there is any evidence on how (free/not within nucleus) neutron/neutron interactions work. I know there is QCD which states they attract (but maybe only in a nucleus?), but that's theory - has this been experimentally proven at all ? I'm only interested in the free...
  34. A

    Neutrino is faster then photon (light) so how can be this possible?

    If I reach the speed of light which is 300 00 km/s the time will stop! and if I travel faster then light i'll travel to the past (Please Correct me if I'm wrong) I read that the Neutrino is faster then photon (light) so how can be this possible ?! Because if it is realy faster than light that...
  35. P

    Superluminal neutrinos now 'pseudoscience'?

    are the supposed superluminal neutrinos at gran sasso now considered 'pseudoscience'?
  36. D

    Decay Energy/Gamma-ray production/Neutrino

    Homework Statement Homework Equations dN/dt = -λN = -\frac{ln(2)}{τ(1/2)} N(1 year) = N0e-λt Decay energy Q = KEf - KEi = mfc2 - mic2 The Attempt at a Solution a): Using the above equations I found: 56Co decays/s = 1.65 x 1047 decays/s 56Ni decays/s = 1.20 x 1045 decays/s...
  37. D

    Neutrino flux through Earth

    EDIT: I apologize for not noticing this earlier, but I realize this should be in the HW/Coursework section of the forum. If possible, would someone be able to move it over for me? Again, sorry for my error and any trouble/confusion. I would like some help calculating the flux of neutrinos...
  38. J

    Neutrino/schrodinger eq problem

    Hey, I'm a high school student from Europe and my final paper is on Neutrino oscillations. I practiced some basic quantum states(qbit), but i find it much harder for this neutrino problem. I translated it in hope that some of you could give me some pointers. I left some parts of the...
  39. R

    Can neutrinos cause Cherenkov radiation?

    If I'm correct, Cherenkov radiation is caused when particle moves faster than light in a certain medium. Can neutrinos, say, travelling through water, cause Cherenkov radiation then? Or is there a property of neutrinos which prevents that?
  40. B

    Higgs, neutrinos, and standard model status

    I've always understood that the "formula" for the Standard Model is SU(3) × SU(2) × U(1). Since the discovery of the Higgs boson, and observations of neutrino flavor oscillations, has that formula been revised, or is it still the same?
  41. T

    What is the diference between right handed neutrinos And quarks?

    In the traditional Standard Model, Why right handed quarks can have mass And there cant be any right handed neutrino? Wikipedia says that it damages renormalizability, but why does that not happen with the corresponding quarks? In other words, why did you invent the see saw mechanism for...
  42. S

    Neutral pseudo meson decay into neutrino antineutrino

    what are standards model limits on decay of K0, Do, B0 meson into a pair of neutrino and anti neutrino. I know that these highly suppressed due to involve FCNC. but if someone can tell me about theoretical limits on these reactions.
  43. Spinnor

    Can matter focus neutrinos in a supernova event?

    The initial flux of neutrinos from a supernova is mostly radial (say we are far from where they are produced but also far below the top of the dying star)? As the neutrinos help blow the top off the star do the density variations of the outer portions of the star act like a variable index of...
  44. D

    Problem regarding determining mass of neutrino

    problem regarding determining mass of neutrino (urgent) 1. Homework Statement [/b] It is found that the speed v of the neutrinos with 10 MeV of total energy is (1- v/c) < 2x10^(-9) Estimate the mass of the neutrinos in terms of eV, and determine whether the value you find is an upper or lower...
  45. Mordred

    Cosmic Neutrino background?

    I'm currently reading a cosmology book, the book is 4 years old. I am looking for more recent articles and developments on the subject. This is in the nature of supportive study material.
  46. H

    How much energy is lost due to neutrinos in matter-antimatter reaction ?

    I read that matter-antimatter annihilation is not as useful as we thought because a large amount of energy is carried away by neutrinos. So, how much is this energy ? What is the percentage of the lost energy to the energy calculated from E=mc^2 ?
  47. M

    Neutrino Minimal Standard Model

    Marcus suggested that the nuMSM deserves its own thread and I agree. The nuMSM is the context in which the Shaposhnikov-Wetterich prediction of the Higgs mass was made. (PF thread.) A search on "nuMSM" at InspireHEP turns up 29 papers, a lot of them about cosmology. Shaposhnikov in...
  48. D

    Book suggestions for accelerator and neutrino physics

    Hi, I am writing my (undergraduate) research thesis on accelerator/particle/neutrino physics. I'm planning on writing about the history of this field (HEP) and what such research has tried to accomplish. Currently, I'm looking for some books to read up on the history and such of HEP...
  49. N

    Z-Boson reasonance and the number of neutrino varieties

    I've read that the experimental results of Z-Boson resonance confirm the theoretical expectations that there are 3-types of Neutrinos, not 2 or 4. How are these theoretical expectations calculated? I.e. how does the number of neutrino varieties affect Z-boson resonance? Thank you
  50. P

    Detection of neutrinos from nuclear reactors vs. ambient neutrino noise

    Hello, In experiments such as KamLAND, it is expected to measure neutrinos emitted by Japan's nuclear reactors. Such experiments were built to find evidence for neutrino oscillation. Is there anyone who knows how one can make the difference between the neutrinos from nuclear reactors and...