Draft:Original research/Neutrinos

A neutrino is a particle with neutral charge and perhaps hence the name neutrino. Spin which everything does whether charged or uncharged; is 1/2. Another supremely interesting property of a neutrino is that it is an extremely weakly interacting particle. This particle has mass which is very small.

Universals

The "neutrino fluxes [may be] predicted by such scenarios [as the standard model or grand unification] if consistency with the observed cosmic ray flux and the universal γ-ray background at 1 − 10 GeV is required. Flux levels detectable by proposed km³ scale neutrino observatories are allowed by these constraints. Bounds on or detection of a neutrino flux above ~ 1 EeV would allow neutrino astronomy to probe grand unification scale physics."

"The shapes of the [ultra-high energy] UHE nucleon and γ-ray spectra predicted within ["top-down"] TD models are “universal” in the sense that they depend only on the physics of [a supermassive elementary "X" particle associated with some grand unified theory (GUT)] X particle decay."

"In contrast to the universality of UHE spectral shapes, the predicted γ-ray flux below ∼ 10¹⁴ eV (the threshold for pair production of photons on the [cosmic microwave background] CMB) and the predicted neutrino flux depend on the total energy release integrated over redshift and thus on the specific TD model."

"Observational data on the universal γ-ray background in the 1 − 10 GeV region [27], to which the generic cascade spectrum would contribute directly, turn out to provide an important constraint. Since the UHE γ-ray flux is especially sensitive to certain astrophysical parameters such as the extragalactic magnetic field (EGMF), a reliable calculation of the predicted spectral shapes requires numerical methods."

"The calculations take into account all the relevant interactions with the (redshift dependent) universal low energy photon background in the radio, microwave and optical/infrared regime."

"Above ≃ 100 EeV the corresponding fluxes would dominate all present model predictions for AGN neutrino fluxes [14] as well as the flux of “cosmogenic” neutrinos produced by interactions of UHE [cosmic rays] CRs with the universal photon background [37,38,31]."

The "constraint imposed by requiring that TD scenarios do not overproduce the measured universal γ-ray background at 1 − 10 GeV implies an upper limit on these neutrino fluxes which only depends on the ratio r of energy injected into the neutrino versus [electromagnetic] EM channel, and not on any specific TD scenario or even a possible connection to UHE CRs."

Physics

In this photograph is recorded "[t]he first use of a hydrogen bubble chamber to detect neutrinos, on November 13, 1970. A neutrino hit a proton in a hydrogen atom. The collision occurred at the point where three tracks emanate on the right of the photograph. Credit: Argonne National Laboratory.

A neutrino is an electrically neutral, weakly interacting elementary subatomic particle with half-integer spin. ... Neutrinos do not carry electric charge, which means that they are not affected by the electromagnetic forces that act on charged particles such as electrons and protons. Neutrinos are affected only by the weak sub-atomic force, of much shorter range than electromagnetism, and gravity, which is relatively weak on the subatomic scale. They are therefore able to travel great distances through matter without being affected by it.

"If neutrinos have negligible rest mass, the present density expected for relic neutrinos from the big bang is n_ν = 110 (T_γ/2.7 K)³ cm^–3 for each two-component species. This is of order the photon density n_γ, differing just by a factor 3/11 (i.e. a factor 3/4 because neutrinos are fermions rather than bosons, multiplied by 4/11, the factor by which the neutrinos are diluted when e⁺–e^– annihilation boosts the photon density). This conclusion holds for non-zero masses, provided that m_vc² is far below the thermal energy (~ 5 MeV) at which neutrinos decoupled from other species and that the neutrinos are stable for the Hubble time. Comparison with the baryon density, related to Ω via n_b = 1.5 x 10^–5 Ω_b h² cm^–3, shows that neutrinos outnumber baryons by such a big factor that they can be dynamically dominant over baryons even if their masses are only a few electron volts. In fact, a single species of neutrino would yield a contribution to Ω of Ω_v = 0.01 h^–2 (m_v)_eV, so if h = 0.5, only 25 eV is sufficient to provide the critical density."

"Neutrinos of nonzero mass would be dynamically important not only for the expanding universe as a whole but also for large bound systems such as clusters of galaxies. This is because they would now be moving slowly: if the universe had cooled homogeneously, primordial neutrinos would now be moving at around 200 (m_v)^-1_eV km s^–1. They would be influenced even by the weak (~ 10^–5 c²) gravitational potential fluctuations of galaxies and clusters. If the three (or more) types of neutrinos have different masses, then the heaviest will obviously be gravitationally dominant, since the numbers of each species should be the same."

Astrophysics

"The observations of solar and supernova neutrinos open up a new area of science: neutrino astrophysics. [...] solar neutrinos provide a beam of elementary particles that can be used to investigate fundamental physics, in particular to study intrinsic neutrino properties."

"Neutrino astrophysics offers new perspectives on the Universe investigation: high energy neutrinos, produced by the most energetic phenomena in our Galaxy and in the Universe, carry complementary (if not exclusive) information about the cosmos with respect to photons. While the small interaction cross section of neutrinos allows them to come from the core of astrophysical objects, it is also a drawback, as their detection requires a large target mass. This is why it is convenient put huge cosmic neutrino detectors in natural locations, like deep underwater or under-ice sites."

Colors

Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a neutrino created with a specific lepton flavor (electron, muon or tau) can later be measured to have a different flavor. The probability of measuring a particular flavor for a neutrino varies periodically as it propagates. Neutrino oscillation is of theoretical and experimental interest since observation of the phenomenon implies that the neutrino has a non-zero mass.

A great deal of evidence for neutrino oscillation has been collected from many sources, over a wide range of neutrino energies and with many different detector technologies.

"In neutrinos, which come in three types — electron, muon and tau — [charge parity] CP violation can be measured by observing how neutrinos oscillate, or change from one type to another [at T = 2 K,] muon neutrinos morphed into electron neutrinos more often than expected, while muon antineutrinos became electron antineutrinos less often [which] suggests that the neutrinos were violating CP".

For antiproton-proton annihilation at rest, a meson result is, for example,

$p^{+}+{\bar {p}}^{-}\rightarrow \pi ^{+}+\pi ^{-},$

${\pi }^{+}\rightarrow {\mu }^{+}+{\nu }_{\mu }\rightarrow e^{+}+{\nu }_{e}+{\bar {\nu }}_{\mu }+{\nu }_{\mu },$ and

$D_{S}\rightarrow \tau +{\bar {\nu }}_{\tau }\rightarrow \nu _{\tau }+{\bar {\nu }}_{\tau }.$

"All other sources of ν_τ are estimated to have contributed an additional 15%."

$\tau \rightarrow e+\nu _{\tau }+\nu _{e},$

for two neutrinos.

$\tau \rightarrow h+\nu _{\tau }+X,$

where $h$ is a hadron, for two neutrinos.

Surface fusions

Main resources: Plasmas/Plasma objects/Surface fusions and Surface fusions

Based on the ³He-flare flux from the Sun's surface and Surveyor 3 samples (implanted ¹⁵N and ¹⁴C in lunar material) from the surface of the Moon, the level of nuclear fusion occurring in the solar atmosphere is approximately at least two to three orders of magnitude greater than that estimated from solar flares such as those of August 1972.

Although ⁷Be is usually assumed to have been produced by the Big Bang nuclear fusion, excesses (100x) of the isotope on the leading edge of the Long Duration Exposure Facility (LDEF) relative to the trailing edge suggest that fusion near the surface of the Sun is the most likely source. The particular reaction ³He(α,γ)⁷Be and the associated reaction chains ⁷Be(e^-,ν_e)⁷Li(p,α)α and ⁷Be(p,γ)⁸B => 2α + e⁺ + ν_e generate 14% and 0.1% of the α-particles, respectively, and 10.7% of the present-epoch luminosity of the Sun. Usually, the ⁷Be produced is assumed to be deep within the core of the Sun; however, such ⁷Be would not escape to reach the leading edge of the LDEF.

"Solar neutrinos from ⁸
B decay have been detected at the Sudbury Neutrino Observatory via the charged current (CC) reaction on deuterium and the elastic scattering (ES) of electrons. The flux of ν_e's is measured by the CC reaction rate to be ϕ^CC(ν_e) = 1.75 ± 0.07$(stat)_{-0.11}^{+0.12}$(syst) ± 0.05(theor) $\times$ 10⁶ cm^-1 s^-1. Comparison of ϕ^CC(ν_e) to the Super-Kamiokande Collaboration’s precision value of the flux inferred from the ES reaction yields a 3.3σ difference, assuming the systematic uncertainties are normally distributed, providing evidence of an active non-ν_e component in the solar flux. The total flux of active ⁸
B neutrinos is determined to be 5.44 ± 0.99 $\times$ 10⁶ cm^-1 s^-1."

"The data reported here were recorded between November 2, 1999 and January 15, 2001 and correspond to a live time of 240.95 days."

The following fusion reactions produce neutrinos and accompanying gamma-rays of the energy indicated:

$\mathrm {_{1}^{1}p} +\mathrm {_{1}^{1}p} \rightarrow \mathrm {_{1}^{2}d} +e^{+}+\nu _{e}+\gamma (0.42MeV).$

$\mathrm {_{4}^{7}Be} +e^{-}\rightarrow \mathrm {_{3}^{7}Li} +\nu _{e}+\gamma (0.86MeV).$

$\mathrm {_{5}^{8}B} \rightarrow \mathrm {_{4}^{8}Be} +e^{+}+\nu _{e}+\gamma (14MeV).$

Cosmic neutrino backgrounds

Neutrinos "released from the Big Bang [are] known collectively as the "cosmic neutrino background"."

"The cosmic microwave background [CνB], light that was released when the universe was just 380,000 years old, is also affected by the cosmic neutrino background."

"The energy density of the cosmic neutrino background has been measured using the abundances of light elements and the anisotropies of the cosmic microwave background."

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