bbn, neutrinos, and the cbr gary steigman (with j. p. kneller & v. simha) center for cosmology...
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BBN, NEUTRINOS, AND THE CBR
Gary Steigman
(with J. P. Kneller & V. Simha)
Center for Cosmology and Astro-Particle Physics
Ohio State University
PPC 2007, TAMU, May 14 – 18, 2007
~ 0.1 s after the Big BangNeutrinos Decouple
~ 380 kyr after the Big BangRelic Photons (CBR) are free
~ 100 s after the Big BangPrimordial Nucleosynthesis
BBN (~ 20 Minutes) & The CBR (~ 400 kyr)
Provide Complementary Probes Of The
Early Evolution Of The Universe
Do predictions and observations of the baryon
density (10 (nB/nγ)0 = 274 Bh2 ) and
expansion rate (H) of the Universe agree
at these different epochs?
* Neutrinos Play Important Roles At Both Epochs
As the Universe expands and cools, BBN
“begins” at T 70 keV (when n / p 1 / 7)
Coulomb barriers and the absence of
free neutrons end BBN at T 30 keV
tBBN 4 24 min.
The Early, Hot, Dense Universe Is A
Cosmic Nuclear Reactor
BBN Abundances of D, 3He, 7Li
are RATE (Density) LIMITED
D, 3He, 7Li are potential BARYOMETERS
BBN – Predicted Primordial Abundances
7Li 7Be
4He Mass Fraction
DEUTERIUM --- The Baryometer Of Choice
• As the Universe evolves, D is only DESTROYED
* Anywhere, Anytime : (D/H) t (D/H) P
* For Z << Z : (D/H) t (D/H) P (Deuterium Plateau)
• H and D are seen in Absorption, BUT …
* H and D spectra are identical H Interlopers?
* Unresolved velocity structure Errors in N(H ) ?
• (D/H) P is sensitive to the baryon density ( )
D/H vs. Metallicity
Deuterium Plateau ?
Real variations,systematic differences, statistical uncertainties ?
Low – Z / High – z QSOALS
105(D/H)P = 2.68 ± 0.27
For Primordial D/H adopt the mean
For the error adopt the dispersion around the mean
D/H vs. Metallicity
CBR Temperature Anisotropy Spectrum
(T2 vs. ) Depends On The Baryon Density
The CBR is an early - Universe Baryometer
10 = 4.5, 6.1, 7.5
CBR constrains 10
V. Simha & G.S.
• S H/ H (/)1/2 (1 + 7N / 43)1/2
The Expansion Rate (H Hubble Parameter)
provides a probe of Non-Standard Physics
• 4He is sensitive to S while D probes
+ N and N 3 + N
4He provides a Chronometer
D provides a Baryometer
0.23
0.24
0.25
4.0 3.0 2.0
YP & yD 105 (D/H)
D & 4He Isoabundance Contours
Kneller & Steigman (2004)
BBN (D, 4He) For N ≈ 2.4 ± 0.4
YP & yD 105 (D/H)
4.0 3.0 2.0
0.25
0.24
0.23
D & 4He Isoabundance Contours
Kneller & Steigman (2004)
CBR Temperature Anisotropy Spectrum
Depends on the Radiation Density R (S or N)
The CBR is an early - Universe Chronometer
N = 1, 3, 5
V. Simha & G.S.
CBR constrains N (S)
Lithium ( “Spite” ) Plateau (?)
[Li] 12 + log(Li/H) 2.1
[Li] 12 + log(Li/H) 2.6 – 2.7
Li too low ?
BBN and Primordial (Pop ) Lithium
4.0 3.0 2.0
0.25
0.24
0.23
yLi 1010 (Li/H)
4.0
Even for N 3
Y + D H
Li H 4.0 0.7 x 10 10
log (Li) 2.6 0.1
(vs. log (Li)obs 2.2)
Li depleted / diluted
in Pop stars ?
BBN (D & 4He) and the CBR Agree !
(The Theorist’s Mantra)
More & Better Data Are Needed !
SUCCESS
CHALLENGE
(Lithium ?)