Diapositive 1

1
Nucleosynthèse Primordiale bilan et perspectives
Alain Coc (Centre de Spectrométrie Nucléaire et
de Spectrométrie de Masse, Orsay) Elisabeth
Vangioni (Institut dAstrophysique de Paris )

• Introduction
• Standard Big-Bang Nucleosynthesis
• ?B determination
• Observations
• Nuclear data
• Concordance BBN/CMB/Spectroscopy
• Beyond the Standard Big-Bang model

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Determination of the baryonic density of the
Universe

• Standard Big Bang Nucleosynthesis
• Calculated and observed 4He, D, 3He, 7Li
  primordial abundances ? ? (or ?Bh2)
• Need good
• Observational data
• Nuclear data

• Anisotropies in the Cosmic Microwave Background
  radiation
• BOOMERanG, CBI, DASI, MAXIMA, ARCHEOPS, WMAP,..

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Density components of the Universe
A natural reference the critical density
1.88 h2 ? 10-29 g/cm3 or 2.9 h2 ? 1011 M?/Mpc3
(hH0/100 km/s/Mpc h?0.7)
???/?C
Number of baryons per photon ? ? nb/n? et ?bh2
3.65?107 ?
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Anisotropies of the Cosmic Microwave Background
(CMB)

• Geometry (?T?1), 1st peak
• ?b (2nd/1st peaks)

Spatial fluctuation spectrum of CMB ? (Inertia
from baryons)
?bh20.0224?0.0009 ?(6.134?0.246)10-10
WMAP Spergel et al. (2003)
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Isotopes to constrain ?
4He little sensitive to ?
3He complex stellar production / destruction
history.
D seems the best candidate a strong monotonic
evolution with ? and no stellar production.
7Li main drawback a non monotonic evolution
with ? two ? values for a given Li/H
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Nucleosynthesis (I)
Equilibrium as long as the reaction rate is
faster than the expansion rate
Followed by decoupling and freezeout
Equilibrium p?n Nn/Npexp(-?mnp/kT) ?mnp
1.29 MeV
Equilibrium breaks out when
Then T ? 1010 K and Nn/Np ? 0.2
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Nucleosynthesis (II)
Neutrons decay until T is low enough for
np?D?
becomes faster then deuterium photodisintegration
D? ? np (Q -2.2 MeV)
Then, t 3 mn, T ? 109 K and Nn has decrased to
Nn/Np ? 0.1
Nucleosynthesis starts to produce essentially 4He
together with traces of D, 3He, 7Li, .
X(4He) ? 2X(n) ? 0.2
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Burles Tytler 1998
Observations (I) D
Lyman-? forest
Cloud at redshift of z 3.6 on the line of sight
of quasar QSO 1937-1009

• Observations
• D/H ratio at high redshift from the depth/width
  of absorption lines
• Baryonic density (?b) from the census of the
  Lyman-? Forest  lines

D
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D/H observations in cosmological clouds
Burles Tytler 1998a,b OMeara et al. 2001
DOdorico et al. 2001 Pettini Bowen 2001
Kirkman et al. 2003
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Observation (II) Li abundances in low
metallicity stars

• Spite plateau Li/H versus metallicity (time)
  Li/H?1.12 10-10 Spite Spite, 1982
• (0.91-1.91)?10-10 (95 c.l.) Ryan et al. 2000
• ?2.34?10-10 Meléndez Ramirez 2004
• (1.1-1.5)?10-10 Asplund et al. 2005

• Low dispersion
• 6Li observed ? In principle, low Li destruction ?
  0.1 dex
• ?Reliable primordial abundance (in principle)

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Observations (III) 4He

• 4He from a sample of 82 H II regions in 76 blue
  compact galaxies
• Yp 0.24210.0021
• Izotov Thuan 2003
• From a selected sub-sample
• 0.232 lt Yp lt 0.258
• Olive Skillman 2004

• Previously used values
• Yp0.24520.0015 Izotov et al.
  (1999)
• Yp0.23910.0020 Peimbert et al. (2002)

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Observations (IV) 3He
3He/H data Bania et al. 2002 but at high
metallicity weak constrains on primordial value
Vangioni-Flam et al. 2002.
3He
Calculated (BBNCMB) 3He/H1.0?10-5 ?No 3He
evolution since BBN
3He/H (1.10.2)10-5
Li
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The 12 reactions of standard BBN

• Origin of reaction rates
• Theoretical
• n?p with ?n885.7?0.8 s PDG 2004
  (?n878.5?0.7 ?0.3 Serebrov et al. 2005,
  Mathews, Kajino Shima 2004), otherwise small
  uncertainty Brown Sawyer (2001)
• 1H(n,?)2H Two nucleons effective field theory
  Chen Savage (1999)
• Experimental
• New compilation Descouvemont, Adahchour, Angulo,
  Coc Vangioni-Flam (2004)

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Nuclear reaction rates analysis

•  R-Matrix  formalism S-factors fits of data
  constrained by theory
• Reaction rates measured at BBN energies

Descouvemont, Adahchour, Angulo, Coc
Vangioni-Flam ADNDT (2004)
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Comparison between observed and calculated
abundances
Limits (1-?) obtained by Monte-Carlo from DAACV
reaction rate uncertainties Coc,
Vangioni-Flam,Descouvemont, Adahchour, Angulo,
ApJ (2004)
2-3 factor !
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6Li observations in halo stars
Nissen et al. (1999) Cayrel, et al. (1999) Aoki
et al. (2004) Asplund et al. (2005)
Observed ratio in halo stars 6Li/7Li ? 0.05
Calculated ratio (BBNCMB) 6Li/7Li 10-4?-5
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The Li problems
Descouvemont et al. Coc et al. (2004)
7Be(d,p)2? ? 100
Ryan et al. (2000)
Uncertainty from 2H(?,?)6Li (NACRE)
4He(t,n)6Li, 7Li(p,d)6Li Q -5MeV
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The 7Be(d,p)2? experiment
Centre de Recherche du Cyclotron, Louvain-la-Neuve
One multi-strips LEDA detector
ECR source at CRC
Beam 0.2-1. 107 pps of 7Be at 5.8 MeV, degraded
to 1.8 MeV (0.4 MeV c.m.) Target 200 ?g/cm2 CD2
poliethylene Detectors two (LEDA) multistrips
(8?16) Si detectors (300 and 500 ?m)
LEDA 1 2
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7Be(d,p)2? cross-section
Integrated (?E?0.23 MeV) cross section Angulo
et al. , ApJL (2005)
Experiment at Louvain-la-Neuve
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Experiment at GSI (provisional)
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The Li problems unsolved by nuclear physics

• 7Be(d,p)2? effect negligible
• D(?,?)2? too low
• R-matrix analysis of D(?,?)2? data to be
  done
• 6Li/H?7?10-15 (?40) (D(?,?)2?, 6Li(p,?),
  ??Bh2)
• Other solutions (?)
• Stellar depletion (7Li), observational bias,
  heavy particle decay, proto/ pregalactic
  production (6Li),

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Origin of CMB, SBBN and Li observations
discrepancies

• Nuclear No!
• Stellar (7Li) ?
• Observational bias 1D/3D, LTE/NLTE model
  atmospheres, effective temperature scale
• Li stellar destruction (but low dispersion!)

• Non Standard Model(s) ?
• Affecting expansion rate during BBN
  Quintessence, Tensor-Scalar gravity,
  ?-degeneracy,.
• Variation of fundamental couplings ?em
  Ichikawa Kawasaki 2004, or all Landau et al.
  2005
• Massive particle decay can destroy 7Li but 3He/D
  problem Jedamzik (2004), Kawasaki et al. (2005),
  Ellis et al. (2005)
• Pregalactic/protogalactic 6Li production Suzuki
  Inoue (2002) Rollinde et al. 2005 (?poster
  Rollinde et al.)

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Influence of the expansion rate
Abundances as a function of the effective number
of neutrino families a parametrisation
of the expansion rate.
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Neutrino degeneracy

• But difference in ?? smeared out by neutrino
  oscillations

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Basics of Scalar Tensor theories of Gravitation
Most general theories of gravity include a scalar
field beside the metric Mathematically
consistent Motivated by superstring dilaton
in the graviton supermultiplet, modulii after
dimensional reduction Only consistent massless
field theory to satisfy Weak Equivalence
Principle Preserve most symmetries of general
relativity Useful extension of GR (simple but
general enough)
spin 2
spin 0
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Basics of Scalar Tensor theories of Gravitation
If the coupling (A(?)) has a minimum, it is
attracted toward GR
Damour, Nordtvedt, PRL 70 (1993) 2217
Such solutions are argued to be natural  in
string theory
Damour, Polyakov, NPB 423 (1994) 532

• Constrains at z0 (present), z103 (CMB) and
  z108 (BBN) following Damour Pichon PRD 1999
• Test of BBN code with TS gravity including a
  potential

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Evolution of the scalar component from z1011
until now
a(f) ½ßf2 ln(A(f))
Now
CMB
BBN
Coc, Olive, Uzan, Vangioni, PRD to be submitted
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BBN constraints on Scalar Tensor theories of
Gravitation
7Li
4He
Coc, Olive, Uzan, Vangioni, PRD to be submitted
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Collaborations
Théories Tenso-Scalaires de la gravitation,
Jean-Philippe Uzan (IAP) Keith Olive (University
of Minnesota) Observations (6Li) R. Cayrel (IAP)
F. Spite M. Spite (Observatoire de
Paris-Meudon) Physique nucléaire
expérimentale Carmen Angulo (CRC,UcL, Louvain la
Neuve) Faïrouz Hammache (IPNO) Physique
nucléaire théorique Pierre Descouvemont
(Université Libre de Bruxelles) Physique des
neutrinos Cristina Volpe (IPNO)
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Conclusions et perspectives

• SBBN calculations with nuclear reaction rates
  under control
• Confirms good agreement for ?B values deduced
  from
• CMB,
• SBBN (D and 4He),
• However disagreement between Li observations,
  SBBN and CMB
• Nuclear no!
• Stellar, cosmology, origin ?
• New 6Li observations in halo stars 6Li/ 7Li ?
  0.05
• New observations planned at VLT
• BBN is now a parameter free model !
• Test of theories beyond the Standard Model
• TS theories of gravity
• Neutrino properties
• .