A new look at neutrino limits from big bang nucleosynthesis

Keith A. Olive; Gary Steigman

doi:10.1016/0370-2693(95)00668-B

A new look at neutrino limits from big bang nucleosynthesis

Keith A. Olive, Gary Steigman

Physics and Astronomy (Twin Cities)

Research output: Contribution to journal › Article › peer-review

36 Scopus citations

Abstract

We take a fresh look at the limits on the number of neutrino flavors derived from big bang nucleosynthesis. In particular, recent measurements of the ⁴He abundance enable one to estimate the primordial ⁴He mass fraction at Y_p = 0.232 ± 0.003(stat) ± 0.005 (syst). For a baryon to photon ratio, η, consistent with the other light elements, this leads to a best fit for the number of neutrino flavors N_ν < 3 (the precise number depends on η) indicating a very strong upper limit to N_ν. Here, we derive new upper limits on N_ν, paying special attention to the fact that the best estimate may lie in an unphysical region (N_ν < 3 if all three neutrino flavors are light or massless; the lower bound to N_ν may even be as low as 2, if the small window for a ν_τ mass is exploited). Our resulting upper limits therefore depend on whether N_ν ≥ 2 or 3 is assumed. We also explore the sensitivity of our results to the adopted value of η and the assumed systematic errors in Y_p.

Original language	English (US)
Pages (from-to)	357-362
Number of pages	6
Journal	Physics Letters B
Volume	354
Issue number	3-4
DOIs	https://doi.org/10.1016/0370-2693(95)00668-B
State	Published - Jul 20 1995

Bibliographical note

Funding Information:
We especially thank Paul Langacker for calling to our attentiont hekey issue we haved iscussedh erea nd, Naoya Hata, Bob Scherrer, Dave Thomas and Terry Walker for permission to utilize some of the resultso f our joint work in this manuscript.W e also would like to thankT . Falk and M. Roos for helpful conversations. This work was supportedi n part by DOE grants DE-FG02-94ER40823 and DE-AC02-76ERO1545.

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title = "A new look at neutrino limits from big bang nucleosynthesis",

abstract = "We take a fresh look at the limits on the number of neutrino flavors derived from big bang nucleosynthesis. In particular, recent measurements of the 4He abundance enable one to estimate the primordial 4He mass fraction at Yp = 0.232 ± 0.003(stat) ± 0.005 (syst). For a baryon to photon ratio, η, consistent with the other light elements, this leads to a best fit for the number of neutrino flavors Nν < 3 (the precise number depends on η) indicating a very strong upper limit to Nν. Here, we derive new upper limits on Nν, paying special attention to the fact that the best estimate may lie in an unphysical region (Nν < 3 if all three neutrino flavors are light or massless; the lower bound to Nν may even be as low as 2, if the small window for a ντ mass is exploited). Our resulting upper limits therefore depend on whether Nν ≥ 2 or 3 is assumed. We also explore the sensitivity of our results to the adopted value of η and the assumed systematic errors in Yp.",

author = "Olive, \{Keith A.\} and Gary Steigman",

note = "Funding Information: We especially thank Paul Langacker for calling to our attentiont hekey issue we haved iscussedh erea nd, Naoya Hata, Bob Scherrer, Dave Thomas and Terry Walker for permission to utilize some of the resultso f our joint work in this manuscript.W e also would like to thankT . Falk and M. Roos for helpful conversations. This work was supportedi n part by DOE grants DE-FG02-94ER40823 and DE-AC02-76ERO1545.",

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doi = "10.1016/0370-2693(95)00668-B",

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AU - Olive, Keith A.

AU - Steigman, Gary

N1 - Funding Information: We especially thank Paul Langacker for calling to our attentiont hekey issue we haved iscussedh erea nd, Naoya Hata, Bob Scherrer, Dave Thomas and Terry Walker for permission to utilize some of the resultso f our joint work in this manuscript.W e also would like to thankT . Falk and M. Roos for helpful conversations. This work was supportedi n part by DOE grants DE-FG02-94ER40823 and DE-AC02-76ERO1545.

PY - 1995/7/20

Y1 - 1995/7/20

N2 - We take a fresh look at the limits on the number of neutrino flavors derived from big bang nucleosynthesis. In particular, recent measurements of the 4He abundance enable one to estimate the primordial 4He mass fraction at Yp = 0.232 ± 0.003(stat) ± 0.005 (syst). For a baryon to photon ratio, η, consistent with the other light elements, this leads to a best fit for the number of neutrino flavors Nν < 3 (the precise number depends on η) indicating a very strong upper limit to Nν. Here, we derive new upper limits on Nν, paying special attention to the fact that the best estimate may lie in an unphysical region (Nν < 3 if all three neutrino flavors are light or massless; the lower bound to Nν may even be as low as 2, if the small window for a ντ mass is exploited). Our resulting upper limits therefore depend on whether Nν ≥ 2 or 3 is assumed. We also explore the sensitivity of our results to the adopted value of η and the assumed systematic errors in Yp.

AB - We take a fresh look at the limits on the number of neutrino flavors derived from big bang nucleosynthesis. In particular, recent measurements of the 4He abundance enable one to estimate the primordial 4He mass fraction at Yp = 0.232 ± 0.003(stat) ± 0.005 (syst). For a baryon to photon ratio, η, consistent with the other light elements, this leads to a best fit for the number of neutrino flavors Nν < 3 (the precise number depends on η) indicating a very strong upper limit to Nν. Here, we derive new upper limits on Nν, paying special attention to the fact that the best estimate may lie in an unphysical region (Nν < 3 if all three neutrino flavors are light or massless; the lower bound to Nν may even be as low as 2, if the small window for a ντ mass is exploited). Our resulting upper limits therefore depend on whether Nν ≥ 2 or 3 is assumed. We also explore the sensitivity of our results to the adopted value of η and the assumed systematic errors in Yp.

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A new look at neutrino limits from big bang nucleosynthesis

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