New BBN limits on physics beyond the standard model from 4He

Richard H. Cyburt, Brian D. Fields, Keith A. Olive, Evan Skillman

Research output: Contribution to journalArticlepeer-review

323 Scopus citations


A recent analysis of the 4He abundance determined from observations of extragalactic HII regions indicates a significantly greater uncertainty for the 4He mass fraction. Furthermore, due to a different treatment of systematic effects such as underlying stellar absorption, the derived value of the 4He abundance is slightly higher. As a result, the predicted value of the primordial 4He abundance is now in line with calculations from big bang nucleosynthesis when the baryon density determined by WMAP is assumed. Analysis based on prior estimates of the 4He abundance will necessarily lead to constraints which are overly restrictive. Based on this new analysis of 4He, we derive constraints on a host of particle properties which include: limits on the number of relativistic species at the time of BBN (commonly taken to be the limit on neutrino flavors), limits on the variations of fundamental couplings such as αem and GN, and limits on decaying particles.

Original languageEnglish (US)
Pages (from-to)313-323
Number of pages11
JournalAstroparticle Physics
Issue number3
StatePublished - Apr 2005

Bibliographical note

Funding Information:
R.H.C. would like to thank C. Angulo, P. Descouvemont and P. Serpico for helpful discussions on our respective BBN rate compilations [11–13] . The work of K.A.O. was partially supported by DOE grant DE-FG02-94ER-40823. The work of B.D.F. was supported by the National Science Foundation under grant AST-0092939. The work of R.H.C. was supported by the Natural Sciences and Engineering Research Council of Canada.


  • Big bang nucleosynthesis
  • Early Universe


Dive into the research topics of 'New BBN limits on physics beyond the standard model from 4He'. Together they form a unique fingerprint.

Cite this