Big Bang
Nucleosynthesis
Suggested Reading:
Ryden, Chapter 10
Fields, 2006: The European Physical Journal A,
Volume 27, Issue 1, pp.3-14
Elemental Abundances
Binding Energy/Nucleon
Binding Energy per Nucleon
B/A (MeV)
8
4
He
6
4
3
H
3
He
2
D
0
from Ryden’s book
1
10
A =Z+N
100
Figure 10.1: The binding energy per nucleon (B/A) as a function of the
number of nucleons (protons and neutrons) in an atomic nucleus. Note the
absence of nuclei at A = 5 and A = 8.
ophysics deed, η is the sole parameter in the standard BBN model.
context
ssential
Main BBN Network
he comparticle
ith a(t)
edmann
(1)
smologuniverse
niverse,
species
(2)
ns, and
r parti). Thus
2
ASTR/PHYS 5580
Fields (2006)
COSMOLOGY
Week 6
BBN Calculation
2
ΩBh =WMAP
1
10
10
10
10
10
10
10
2
10
10
4
n
10
He
-3
2
10
H
-5
3
H
3
10
He
-7
10
-9
7
10
Li
7
-11
Be
10
6
-13
-15
C
Li
11
10
10
B
9
-17
10
10
4
1
p
-1
11
10
3
10
-19
-1
-3
-5
-7
-9
10
10
10
10
-11
10
Be
10
B
8
8
B
10
10
10
10
Li
B
10
13
12
Be
10
10
Coc et al. (arXiv:1107.1117)
2
10
-16
-17
-18
-19
-20
-21
-17
-19
10
-21
10
-23
10
-22
-23
-24
B
-25
10
-15
-15
9
-23
-14
-13
Li
10
10
10
10
-21
Mass fraction
Mass fraction
10
3
10
Time (s)
4
-25
10
-25
Dependence on Baryon-to-Photon Ratio
B.D. Fields: Big bang nucleosynthesis in the new cosmology
Fields (2006)
Fig. 5. The predictions of standard BBN [18], with thermonuclear rates based on the NACRE com
8
The European Physical Journal A
Observation of D Abundance
to turn the problem around and test the astrophysics of
post-BBN light element evolution [26]. Alternatively, one
can consider possible physics beyond the Standard Model
(e.g., with Nν ̸= 3) and then use all of the abundances to
test such models; this is the subject of our final section.
4 Light element observations and comparison
with theory
BBN theory predicts the universal abundances of D, 3 He,
4
He, and 7 Li, which are essentially determined by t ∼
Ferlet etatal.much
(ISM)later
180 s. Abundances are however observed
epochs, after stellar nucleosynthesis has commenced. The
ejected remains of this stellar processing can alter the light
element abundances from their primordial values, but also
produce heavy elements such as C, N, O, and Fe (“metals”). Thus one seeks astrophysical sites with low metal
abundances, in order to measure light element abundances
which are closer to primordial. For all of the light elements,
systematic errors are an important and often dominant
limitation to the precision of the primordial abundances.
In recent years, high-resolution spectra have revealed the presence of D in high-redshift, low-metallicity
quasar absorption systems (QAS), via its isotope-shifted
Lyman-α absorption. These are the first measurements
of light element abundances
distances.
Burlesat&cosmological
Tytler (1998)
It is believed that there are no astrophysical sources of
deuterium [27], so any measurement of D/H provides
a lower limit to primordial D/H and thus an upper
limit on η; for example, the local interstellar value of
D/H = (1.5 ± 0.1) × 10−5 [28] requires that η10 ≤ 9. In
fact, local interstellar D may have been depleted by a
factor of 2 or more due to stellar processing. However,
Q1243+3047
Q0347-3819
Q2206-199
PKS1937-1009
Fields (2006)
Fig. 6. D/H abundances shown as a function of [Si/H]. Labels
denote the background QSO, except for the local interstellar
value (LISM; [28]).
Observation of
4He Abundance
Steigman (arXiv:1208.0032)
Figure 2: Helium abundance (mass fractions, Y) determinations from the sample of extragalactic
H II regions studied by Izotov & Thuan (2010) [29] as a function of the corresponding oxygen abundances (O/H by number). The solid line is the Izotov & Thuan best fit to a linear Y versus O/H
correlation.
Neutrino Physics
“Evolution” of the primordial helium
abundance
Neutrinos And B
Steigman, arXiv:1208.0032
Primordial Nucleosynthesis
Gary Steigman
Observation of 7Li Abundance
Steigman (arXiv:1008.4765)
Figure 2: The lithium abundances ([Li] ≡ 12+log(Li/H)) as a function of metallicity ([Fe/H]) as derived
from observations of very metal-poor stars in the Galaxy. See the text for references. The horizontal band
shows the ±1σ SBBN prediction.
10
-3
10
-4
0.24
He/H, D/H
3
10
10
Li/H
2
4
He
0.22 -3
10
10
7
Planck
(2005), rather than considering
-2
ΩB h
0.26
7
Li/H
3
cic
-5
10
(2010)
with
the
first WMAP
re3
he
He
5)al. 2007) to -6the recent Planck
10
u-2013). The reduced uncertainty
7
-9
is
Lireduced
10
rect
consequence
of
the
he
on
Ωb ·h2 while 7 Li uncertainty is
ry
-10
by
nuclear
uncertainty
on the
10
to
e.
ts
1
10
Coc
(arXiv:1307.6955)
nlays the abundances as a func10
of
η×10
Table
2 those at Plank baryonic
ng
rs- Neﬀ = 3.Fig.We1.—do(Color
not online)
use the
Abundances
or
3
7
of 4 He D, et
Heal.and(2005)
Li (blue) as a
lue
from
Mangano
rs
function of the baryon over photon ranon–instantaneous
neutrino
decoutio (bottom)
or baryonic
density (top).
in
sence of oscillations.
While
this to the
The vertical areas
corresponds
22
WMAP
black) for
and Planck
works
for 4 He,
the(dot,
change
the (solid,
by
yellow) baryonic densities while the
r.]exactly in the opposite direction
horizontal areas (green) represent the
rk
adopted observational abundances; see
n-Hence, to implement these very
text. The (red) dot–dashed lines cor2 × 10−4 for
Yp ),towe
suggest to
nd
respond
the extreme values of the
or
ader, to correct
3 results
eﬀectiveN
neutrino
coming from
eﬀ = families
ns
CMB Planck
study, Neﬀ
= (3.02, 3.70);
ith the exactly
calculated
abunsee text.
e.g. ∆Yp ) given in the Tables of
Mass fraction
10
10
10
D
-4
-5
3
He
-6
7
-9
Li
-10
1
Planck
BBN vs CMB onD η
He/H, D/H
he
WMAP
M
ty
0.24
gioni
(2010);
(b) Coc et al.4 (2012), (c) Spergel et al. (2007) ; (d) Amsler et al. (2008);
ed
He
)is Komatsu et0.22al. (2011) ; (f) Beringer et al. (2012); (g) Ade et al. (2013)
10
10
η×10