February2,2008 8:32 WSPC/TrimSize: 9.75inx6.5inforProceedings serpicoS03proceedings AN UPDATED NUCLEAR REACTION NETWORK FOR BBN. 4 0 0 PASQUALEDARIOSERPICO 2 Max-Planck-Institut fu¨r Physik n (Werner-Heisenberg-Institut) a J F¨ohringer Ring 6 D 80805 Mu¨nchen [email protected] 7 1 ThekeyStandard-Physics inputsoftheBigBangNucleosynthesis (BBN)arethe v light nuclei reaction rates. Both the network and the nuclear rates have been 2 recently reanalyzed and updated, and cosmological and New-Physics constraints 7 (takingintoaccounttheWMAPCosmicMicrowaveBackgroundanisotropiesmea- 0 surement)obtainedwithanewcodearepresented. 1 0 4 0 Early Universe is a (hot) plasma in a FLRW metric whose composition and / h properties depend on the cosmic temperature T and that cools during universe p expansion. Themaineventsofitsevolutiondependonthefreezing ofsomeinterac- - o tionduringthecosmicexpansion. BBNtakesplacewhennuclearreactions(keeping r baryonsinchemicalequilibrium)freeze-out,thusproducingacharacteristicpattern t s in light nuclide abundances. a : BBN plays a fundamental role in Cosmology, where it can be used to check the v internal consistence of the Standard Cosmological Model (SCM); in Astrophysics, i X e.g. to study the Li depletion mechanism in halo PopII stars, PopIII chemical r composition or the Galactic Chemical Evolution; or to get a hint of New-Physics, a because BBN is sensitive to the existence of other relativistic degrees of freedom (parameterized in N ), to ν’s asymmetries, etc. eff In its minimal formulation, BBN is an overconstrained theory: all the relevant observables depend on the only unknown parameter η ≡ n /n , where n and n b γ b γ are respectively the baryon and the photon number densities. The other parame- ters are Standard-Physics inputs, and the greatest uncertainties in standard BBN predictions arise from nuclear reaction rates R . k These rates are obtained as thermal averages of the relevant cross-sections σ. Froma theoreticalpoint of view, it is very difficult to use a first principle approach (strong interactions, many body problems, etc.), so one makes recourse to nuclear models. Moreover, experimental difficulties are present due to the low counting rates, strong energy dependence and corrections for electron screening. To obtain low energy extrapolations,fit the data and/or the theoreticalpredictions, it is use- ful to introduce some meaningful parameterizations, as the so-called astrophysical S factor. 1 February2,2008 8:32 WSPC/TrimSize: 9.75inx6.5inforProceedings serpicoS03proceedings 2 In a completely general approach, the error matrix (due to nuclear uncertainties) for the nuclide abundances is given by the quantities: 1 σi2j(θ,R)≡ 4X(cid:2)Xi(θ,Rk+δRk+)−Xi(θ,Rk−δRk−)(cid:3)×[i→j] (1) k ± withδR the(temperaturedependent)upperandloweruncertaintiesonR ,respec- k k tively; R represents the collection of the nuclear reactionrates and θ the collection oftheotherrelevantcosmologicalparameters(i.e. η,N ,...). Thisslightlydiffers eff from the approach in [1] which assumes the existence (in principle not necessary) of the linear functionals λ =∂logX (θ)/∂logR . To properly define these quan- ik i k tities, the symmetric, temperature independent, relative uncertainties δR /R are k k needed. The analysis performed in [2] (see also [3, 4]) is restricted to a reduced network including the reactions relevant for the abundances of the nuclides with A≤7. More than 80 reactions were examined, and many of the main reaction rates have been updated. Particularlyusefultools in this workwere furnishedby the NACRE compilation [5], the LUNA measurement [6], or some recent theoretical predictions (e.g. [7], for the key reaction p+n → γ +2H). Moreover, in the new code the nuclear partition functions were introduced to include the role of excited states for nuclides whose mass number A ≥ 6 [2, 5], and new reactions were added (as the 3He+3H ↔γ+6Li, see [2, 3, 4]). The negligible role of plasma screening effects and of new three-body reactions was also confirmed [2, 4]. In the recent paper [3], some applications of this new code were performed: we (mainly) checked the internal consistence of the SCM (sections 4 and 5) and eval- uated the BBN constraints on some New-Physics scenarios (section 7): e.g., we showedthatinthe Degenerate-BBNscenarioafourthsterileneutrino,asforexam- ple required to interpret LSND evidence for ν ↔ ν oscillation, is not yet ruled µ e out. References 1. G. Fiorentini, E. Lisi, S.Sarkar, and F.L. Villante, Phys. Rev. D58, 063506, (1998). 2. P.D. Serpico, Diploma Thesis, Universityof Naples Federico II,2003 (unpublished). 3. A. Cuoco, F. Iocco, G. Mangano, G. Miele, O. Pisanti, and P.D. Serpico, astro-ph/0307213. 4. F. Iocco, G. Mangano, G. Miele, O.Pisanti, and P.D.Serpico, in preparation. 5. C. Angulo et al., Nucl. Phys. A656, 3, (1999). NACRE web site http://pntpm.ulb.ac.be/nacre.htm. 6. LUNACollaboration, Nucl. Phys. A706, 203, (2002). 7. G. Rupak,Nucl. Phys. A678, 409-423, (2000).