کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
10722798 1033800 2011 4 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
A robust upper limit on Neff from BBN, circa 2011
موضوعات مرتبط
مهندسی و علوم پایه فیزیک و نجوم فیزیک هسته ای و انرژی بالا
پیش نمایش صفحه اول مقاله
A robust upper limit on Neff from BBN, circa 2011
چکیده انگلیسی
We derive here a robust bound on the effective number of neutrinos from constraints on primordial nucleosynthesis yields of deuterium and helium. In particular, our results are based on very weak assumptions on the astrophysical determination of the helium abundance, namely that the minimum effect of stellar processing is to keep constant (rather than increase, as expected) the helium content of a low-metallicity gas. Using the results of a recent analysis of extragalactic HII regions as upper limit, we find that ΔNeff⩽1 at 95% C.L., quite independently of measurements on the baryon density from cosmic microwave background anisotropy data and of the neutron lifetime input. In our approach, we also find that primordial nucleosynthesis alone has no significant preference for an effective number of neutrinos larger than the standard value. The ∼2σ hint sometimes reported in the literature is thus driven by CMB data alone and/or is the result of a questionable regression protocol to infer a measurement of primordial helium abundance.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Physics Letters B - Volume 701, Issue 3, 11 July 2011, Pages 296-299
نویسندگان
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