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Nuclear Reactions in Primordial Nucleosynthesis

Nuclear Reactions in Primordial Nucleosynthesis. Pasquale Dario Serpico MPI für Physik München. V Meeting Italiano di Astrofisica Nucleare 20-22 Aprile 2005 -Teramo.

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Nuclear Reactions in Primordial Nucleosynthesis

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  1. Nuclear Reactions in Primordial Nucleosynthesis Pasquale Dario Serpico MPI für Physik München V Meeting Italiano di Astrofisica Nucleare 20-22 Aprile 2005 -Teramo based on work in collab. with S. Esposito, F. Iocco, G. Miele, G. Mangano and O. Pisanti - “Federico II” University and INFN Naples

  2. Overview of the Talk (2H) (4He) (7Li) BBN in the “Precision Cosmology” Epoch n-decoupling & n↔p rates : The Weak reaction stage The Road to the Nuclides: The Nuclear reaction stage As BBN is ruled by Non-linear Differential equations… present status: theory versus observations Outlook & perspectives P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  3. BBN Flowchart Primordial Elements Observations Cosmology Yi Systematics! Nuclear Astrophysics BBN Data Regression! Astrophysics s(E) wb , dwb/wb <<1!!! CMB “PDG” stuff: n , GN, a, • Physics... New Physics?

  4. Weak rates Freeze out of weak rates fixes n/p ratio (crucial for4He) Big improvements in the last decade: • QED radiative corrections • Finite nucleon mass corrections • Plasma effects • Neutrino spectral distortion Rates are accurate at the O(0.1 %), i.e. as(dn/ n)exp P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  5. 4He status Once WMAP value forwbfixed, theoretical predictions are quite robust, unless some unknown systematics affect the STANDARD PHYSICSdata(e.g., nexp, G. Matthews et. al. ‘04) Yp th=0.2481± 0.0005 For wb=0.023 ± 0.001 General agreement among several groups. Error dominated by(dn/ n)exp New evaluation of GN: negligible contribution to the uncertainty (PDG 2004) P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  6. The observational side is still “confused”: BCG (metal poor, extragal. obj., HII regions) give an unreasonable spread of values, changing with the sample, the regression method to Z=0, the analyzers’ group… Not shown, Ypb=0.2421(44)±0.0021 (Iz& Th ’04) Other Determinat. ~0.244 (I) 0.248±0.009 (II), ±0.004 (II’) Yp=0.239 ±0.002 Yp=0.2345 ±0.0026 Yp=0.244(5) ±0.001 Olive & Skillman 04 Yp=0.249 ±0.009 0.232≤Yp ≤ 0.258 Conservative Range The estimate is systematics dominated (e.g., degeneracies among astrophysical parameters). Further (high quality) data, and possible complementary techniques needed to improve the determination. P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  7. Bounds to Non-standard Physics: the case of neutrino sector At this stage it is impossible to severely bound Neff from BBN. However always much better than CMB alone: according to the assumed value for Yp -but quite conservatively-DNeff<1-1.5. Analogously, the BBN bound on lepton degeneracyx is by far the most stringent Cuoco et al. ‘03 See also Barger et al. ‘03 D+CMB Extended to all flavors! Dolgov, Hansen, Pastor, Petcov, Raffelt, Semikoz 2002 D+ 4He +CMB P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  8. Road 1 4He Observations Cosmology Yp Systematics! Only “loose” check of Standard Cosmological Model BBN CMB New Physics? Till now, many bounds (DNeff,xe. …) Could be improved!!!

  9. Nuclear rates Apart for Helium, all the other nuclides are sensitive to the Nuclear reaction Network. To refine the predictions, it is then mandatory to properly evaluate the thermal averaged nuclear rates and their uncertainties Well, where is the problem? P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  10. Nuclear rates- II No First Principle Theory exists, as for the n↔p rates. Only partial information (Detailed Balance linking direct and Reverse Rates, Nuclear Model calculations suggesting fitting formulae, etc.) → Huge amount of experimental data needed! Main Experimental problems: extract the cross section from data in the low energy range of interest for BBN (~0.01  ~1 MeV) • Crucial role of Coulomb repulsion • Strong energy dependence • Low cross sections (~pb) • Spurious effects (e.g. atomic/molecular screening) • Extrapolation (e.g., S-factor) to low E • Difficulties with handling n and radioactive beams (e.g. 7Be, 3H) • No BBN-dedicated experiments, always “stellar” purposes. P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  11. Nuclear rates- III • Data from different experiments with different systematics • For several crucial reactions present data show evidence for ununderstood systematics • Experimental results typically overlap only partially in energy • Cross section for some (at the moment) sub-leading process is still poorly known Recent (2004) BBN-oriented Compilations: Cyburt Descouvemont et al. Serpico et al. However, with respect to the “historical” data analysis ( from Fowler and Hoyle 1964...to Smith, Kawano and Malaney 1993) Important recent steps in the field: NACRE Coll. Database: pntpm.ulb.ac.be/nacre.htm Other data (e.g. 2H(p,)3He by LUNA Collaboration 2002) P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  12. Fit method and error estimates Sik S factor at Ei of k-th experiment ikstatistical uncertainty knormalization uncertainty Sthfit (often polynomial) of the S factor depending on coefficients anto be determined by the fit Regression approach: minimization of koffset of the k-th experiment (free parameter determined by the fit) P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  13. NOTE: The choice of the regression technique and error estimate is a non-trivial task!!! Other compilations are based on biased methods (as in Cyburt 04; see D’ Agostini 94) or on some “arbitrary” criterion (as in Descouvemont 04) P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  14. Rate estimate best fit values Boltzmann-Gamow kernel Error estimate for reduced n2 larger than 1 the error is inflated by a factor (PDG minimal prescripition) The minimum measured scale error is added in quadrature (conservative, but not OVER-conservative as in Cyburt 04) P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  15. From nuclear rates to nuclide abundances BBN evolution equations numerically solved via a new code Theoretical uncertainties on Xi due to the ratesk: generalization of the linear propagation (Fiorentini, Lisi, Sarkar and Villante 1998) Allows T-dependent and/or asymmetric errors! P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  16. 2H - 2Hreactions: leading source of uncertainty for Deuterium Small statistical errors but quite large systematics due to scale normalization or unknown: poor 2 2H(d,p)3H 2H(d,n)3He Systematics-dominated, higly desiderable a new single measurement covering most of the E-range, and filling the gap of data at E=0.2-~1 MeV P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  17. A “good” example: 2H(p,)3He LUNA ‘02 data a low energy discrepancy solved, error on 2Hreduced A still debated case: 4He(3He,)7Be dominant channel for 7Be production, crucial for 7Li error budget. New measurement ongoing Important also for solar n fluxes (B & Be) P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  18. 2H status Deuterium is the most sensitive nuclide to wb : Best BBN “baryometer” wb(D)=0.021 ± 0.002 105(2H /H) th= 2.44+0.20–0.17 For wb=0.023 ± 0.001 only ± 0.04!!! due to nuclear uncertainties Essential agreement between two completely independent determinations of wb!!! Wonderful check of Standard Cosmological Model Deuterium in QSOAS Kirkman et al. 2003 One More Observation! Crighton et al. 2004 105 <2H /H> obs (2.78+0.44–0.38) 105 <2H /H> obs 2.42 ±0.27(0.57) P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  19. Deuterium in QSOAS Ly-a abs Road 2 Low Statistics (5-7 data) Systematics?(n2~4) Cosmology Theoretical Central Value and Error sligthly dependent on regression analysis for 2H(d,p)3H-2H(d,n)3He-2H(p,g)3He BBN Perfect Agreement! 2H /H strongly depends onwb CMB Important Check of Standard Cosmological Model! But…

  20. 7Li status • Given the WMAP result, the road to 7Li is clarified Propaganda: we did not limit to reanalyze the ~O(10) reactions believed to be dominant. We revised and update the whole network (O(~100)), improved the analysis or looking for new important reactions, and checked again the relative weights of the different channels. Almost two years of work... A (partial!!!) list: 2H(d,)4He, 3He(t,d)4He, 3He(t,np)4He, 3H(t,nn)4He, 4He(d,)6Li, 6Li(p,3He)4He, 3H(p, )4He, 7Li(p, )4He4He, 7Be(n,)4He, 7Li(d,n)4He4He, 7Be(d,p)4He4He, 6Li(d,p/n)7Li/ 7Be, 7X(3X,p/n)9Be ,three body, partition functions... Equilibrium determined bywb, and the relative weight of the two paths First 7Li bump: T~70 keV, via4He(t,g)7Li Then plateau reached because of competion of7Li(p,a) 4He Indirect7Li production via4He(3He,g)7Be and late EC decays to 7Li P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  21. We get 1010(7Li /H) th= 4.8 ± 0.4 ± 0.4 Due to nuclear uncertainties Due to dwb=0.001 Experimentally, in ancient metal poor stars (halo or extragal.) one finds a plateau (Spite pl.) for low Z → Hint of Primordial Origin. Several determinations, suggesting the (conservative) range 1<1010(7Li /H)exp<2 d (7Li /H)exp <0.5 Very difficult measurements, tiny fraction of neutral Li, crucial importance of T… Low dispersion, compatible with 0, hard to explain by depletion/diffusion models! Still an open problem: the most puzzling for Standard BBN New clues on Astrophysics? A window on non-standard Physics in the Early Universe? P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  22. Nuclear Physics Solution disfavored, tough not yet completely ruled out “Wrong” normalization in4He(3He,g)7Beto reconcile Spite Plateau & BBN excluded at (at least) 2 s from the measured solar Boron n-flux in SNO [Cyburt et al., PRD 69 (2004)] Possible underestimate of7Be(d,p)2 4Heby 2-3 orders of magnitude [Coc et al. ApJ 600 (2004)] seems excluded by new measurements (C. Angulo @ NIC VIII) x30 x100 x300 x1000 We expect this issue to be soon (and finally) clarified by forthcoming measurements. P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  23. Exotica K Jedamzik, PRD 70 (2004) In Non-standard BBN, other interesting possibilities. For example, decay or annihilation of CDM relics (neutralinos?) → Prediction of a 6Li plateau P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  24. Exotica: an intriguing hint Recent hint for a 6Li plateau (see review in Lambert, astro-ph/0410418) A possible window on non-standard physics! In this context, other interesting possibilities for Nuclear Astrophysics Experimentalists in improved measurements of (e.g.) 6Li+p↔3He+4He, 6Li+n↔3H+4He,… +other possibly neglected reactions Indirectly (CR nucleosynthesis), the spallation a+a reactions at middle-high energies also quite important! P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  25. Road 3 Spite Plateau Systematics in Astrophysical models? New Measurements BBN Astrophysics CMB New Physics?

  26. Outlook I focused on the difference between 4He prediction (depending on weak rates and n effects, theoretically well understood) and the other nuclides, sensitive to the Nuclear Network details. • We performed a deep and wide review and analysis of the network • We compiled an updated BBN-oriented nuclear database • We used a new, self-consistent and unbiased protocol for data regression. The error budget was put on a more “statistical” ground, and typically a reduction of the errors with respect to previous compilations was found. I compared the predictions for the three most relevant nuclides with observations (2H) (4He) (7Li) P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  27. A Summary Plot of present Standard BBN Situation 1 s nuclear error bars included, observational conservative ranges or upper limits shown. hbx1010 P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  28. Perspectives We expectfrom Nuclear physicists: new measurements in the energy range of interest for BBN (0.01  1 MeV) 4He(3He, )7Be, 2H-2H, 7Be(n,4He)4He, 4He(2H, )6Li,... Astrophysicists: better understanding of possible systematics affecting 4He measurement and 7Li, but also more data for 2H Astroparticle physicists:If both the previous communities will confirm actual results... Should try to find some smart idea to solve the puzzle, as usual!!! P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  29. QED radiative effects Check: the neutron lifetime inner corrections outer corrections Perturbative QCD Leading log resummation Coulomb correction: rescattering of electron in the proton field, Weak magnetism nexp = 885.7 ± 0.8 snth = 886.5 s P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  30. Plasma effects • Interactions with photons/electrons of the plasma • Change in the e.m. equation of state due to photon/electron thermal masses P=P() • New Process (→ only allowed at finite T. Checked negligible) Very small corrections ≤ O(0.1 %) P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  31. Neutrino decoupling neutrinos are in chemical equilibrium with the e.m. plasma till weak reactions freeze out at T few MeV First approximation: instantaneous decoupling. Neutrino decoupling has no overlap in time with e+-e- annihilation Asymptotic value reached forTν /T: All nspecies keep FD distribution Standard Contribution to Hubble Expansion Law P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  32. More accurate calculations by solving the kinetic equations show apartial entropy transfer during e+-e- annihilation phase Spectral Distortions, f=fn(p,Tν)[1+δf(p)] different forne(both CC & NC) and nx(NC only) How distortions in neutrino distributions can affect BBN ? • change in total n energy density ~ 1 % • change in n-p weak rates:fne enters the thermal averaged rate Tiny effects, ~ 10-4 on 4He mass fraction!! For details and references: Dolgov, Phys. Rep. 370 (2002) P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

  33. nexpProblem? If confirmed, quite embarassing for most of the previous determinations!!! In G. Matthews et. al. ’04, used nexp = 878.5 ± 0.7 s ±0.3 s from Serebrov et al, unpublished, 04 instead of nPDB = 885.7 ± 0.8 s Yp th=0.248→0.246 Gravitational trap, cold n Estrapolation tostor-1→0, Best storage time determination claimed P. D. Serpico, MPI für Physik - Munich “Nuclear Reactions in Primordial Nucleosynthesis” 20-22/04 Teramo

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