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Title: Insights into neutrino decoupling gleaned from considerations of the role of electron mass

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Journal Article: Published Article
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Nuclear Physics. B
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Related Information: CHORUS Timestamp: 2017-08-03 15:30:24; Journal ID: ISSN 0550-3213
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Grohs, E., and Fuller, George M. Insights into neutrino decoupling gleaned from considerations of the role of electron mass. Netherlands: N. p., 2017. Web. doi:10.1016/j.nuclphysb.2017.07.019.
Grohs, E., & Fuller, George M. Insights into neutrino decoupling gleaned from considerations of the role of electron mass. Netherlands. doi:10.1016/j.nuclphysb.2017.07.019.
Grohs, E., and Fuller, George M. 2017. "Insights into neutrino decoupling gleaned from considerations of the role of electron mass". Netherlands. doi:10.1016/j.nuclphysb.2017.07.019.
title = {Insights into neutrino decoupling gleaned from considerations of the role of electron mass},
author = {Grohs, E. and Fuller, George M.},
abstractNote = {},
doi = {10.1016/j.nuclphysb.2017.07.019},
journal = {Nuclear Physics. B},
number = ,
volume = ,
place = {Netherlands},
year = 2017,
month = 8

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Publisher's Version of Record at 10.1016/j.nuclphysb.2017.07.019

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  • Perturbative analyses seem to suggest that fermions whose mass comes solely from a Yukawa coupling to a scalar field can be made arbitrarily heavy, while the scalar remains light. The effects of the fermion can be summarized by a local effective Lagrangian for the light degrees of freedom. Using weak coupling and large-{ital N} techniques, we present a variety of models in which this conclusion is shown to be false when nonperturbative variations of the scalar field are considered. The heavy fermions contribute nonlocal terms to the effective action for light degrees of freedom. This resolves paradoxes about anomalous andmore » nonanomalous symmetry violation in these models. The application of these results to lattice gauge theory implies that attempts to decouple lattice fermion doublers by the method of Swift and Smit cannot succeed, a result already suggested by lattice calculations.« less
  • In this paper we reconsider recently derived bounds on MeV tau neutrinos, taking into account previously unaccounted for effects. We find that, assuming that the neutrino lifetime is longer than [similar to]100 sec, the constraint [ital N][sub eff][lt]3.6 rules out [nu][sub [tau]] masses in the range 0.5[lt][ital m][sub [nu][tau]][lt]35 MeV for Majorana and 0.3[lt][ital m][sub [nu][tau]][lt]35 MeV for Dirac neutrinos. Given that the present laboratory upper bound is 31 MeV, our results imply an upper bound of 0.5 MeV for Majorana neutrinos and of 0.3 MeV for Dirac neutrinos.
  • We consider the decoupling of neutrinos in the early Universe in presence of non-standard neutral current neutrino-electron interactions (NSI). We present the results of fully numerical and momentum-dependent calculations, including flavor neutrino oscillations. We find that the presence of neutrino-electron NSI may enhance the entropy transfer from electron-positron pairs into neutrinos instead of photons, up to a value of the effective number of neutrinos N{sub eff}{approx_equal}3.12 for NSI parameters within the ranges allowed by present laboratory data, which is almost three times the effect that appears for standard weak interactions. Thus non-standard neutrino-electron interactions do not essentially modify the densitymore » of relic neutrinos nor the bounds on neutrino properties from cosmological observables, such as their mass.« less
  • Using all the SN 1987A neutrino burst events culled by the Kamiokande II detector and a realistic underlying neutrino source model and spectrum, a series of Monte Carlo calculations has been performed to obtain upper limits with confidence levels for the mass of the electron neutrino. With conservative assumptions, the upper limits are 14 eV (90 percent), 16 eV (95 percent), and 19 eV (99 percent). These limits are inconsistent with the lower limit quoted by the ITEP collaboration and are lower than all the extant upper limits from tritium decay experiments. If further, but reasonable, source model constraints aremore » imposed, limits of 12 eV (90 percent), 14 eV (95 percent), and 17 eV (99 percent) are obtained. 29 references.« less
  • The investigation of tritium {beta}-decay yields the lowest limits on the rest mass of the electron anti neutrino from decay kinematics. [m{sub {nu}}{sup 2}c{sup 4} = ({minus}147{+-}68{sub stat}{+-}41{sub sys}) (eV){sup 2} and m{sub {nu}}{sup 2}c{sup 4} = ({minus}24{+-}48{sub stat}{+-}61{sub sys}) (eV){sup 2}.] to improve the limits the authors investigated the endpoint region of the tritium {beta}-decay spectrum with an integrating solenoid retarding spectrometer. This spectrometer is ideally suited for this experiment as it offers high resolution and a large accepted solid angle simultaneously. It essentially consists of a magnetic guiding field formed by two solenoids and a set of cylindricalmore » electrodes providing the electrostatic filter. Electrons with an energy high enough to pass the filter are reaccelerated and focussed onto the detector. The sources used are about 30 monolayers of {sup 3}H{sub 2} frozen onto a LHe cooled Aluminium substrate. A resolution of E/{Delta}E of 3000 together with a high solid angle of {Delta}{Omega}/4{pi} = 40% and a low background enabled the authors to improve the results quoted above. Data were taken in the region close to the endpoint for about 24 days. The signal obtained is clearly above background at 20 eV below the {beta} endpoint. To minimize systematic uncertainties the data evaluation is restricted to a region of 137 eV below the endpoint. The result is m{sub {nu}}{sup 2}c{sup 4} = ({minus}39{+-}34{sub stat}{+-}15{sub sys})(eV){sup 2}, from which an upper limit of m{sub {nu}}c{sup 2} < 7.2eV may be derived. The experiment yields the atomic mass difference of m({sup 3}H) - m({sup 3}He) = (18591 {+-}3)eV.« less