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Transcript of 1 Primordial nucleosynthesis and New Physics Maxim Pospelov University of Victoria and Perimeter...
1
Primordial nucleosynthesis and New Physics
Maxim PospelovUniversity of Victoria and Perimeter Institute
K. Jedamzik and M. Pospelov, arXiv:0906.2087R. Cyburt and M. Pospelov, arXiv:0906.4373
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Outline of the talk
1. Current status of Big Bang Nucleosynthesis.
2. Lithium problem. Possible solutions.
3. Particle decay/annihiliation after the BBN.
4. Catalyzed BBN.
5. Conclusions.
3
BBN and Particle Physics
.0other ; conditions Initial less;or MeV ~ reactants ofEnergy
......)(
inp
kjijkii
nnn
nnvdT
dnTTH
dt
dn
Particle physics can
1. Affect the timing of reactions,
via e.g. new thermal degrees of freedom
2. Introduce non-thermal channels e.g. via late decays or annihilations of heavy particles, E À T.
3. Provide catalyzing ingredients that change hijkvi (MP, 2006). Possible catalysts: electroweak scale remnants charged under U(1) or color SU(3) gauge groups. Relevant for charged NLSP-gravitino
LSP scenario.
extrafermion
extrabosoneff
Pl
22/1
eff 8
732
8
72 ;const)( NNN
M
TNTH
4
Elemental Abundance
A<1,2,3,4,7 – BBN; A>12 –Stars; A=6,9,10,11 –“orphans” (cosmic ray spallation)
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BBN abundance curves
n/p freeze-outDeut. bottleneckAll nuclear rates drop <Hubble
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Non-thermal change of elemental abundances due to late time energy injection
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Catalyzed Production of 6Li and 9Be at 8 KeV, suppression of 7Be+7Li at 35 KeV
Day 1, 5:25a.m. 0:03a.m.
9Be
6Li
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SBBN, current Status (Cyburt, Fields, Olive 2008)Theoretical predictions of abundances as functions of b Yellow band: WMAP-suggested input for baryon to photon ratio b =6.14 10-10
7Be branch
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The fraction of energy density in baryons is measured rather precisely,
No more wiggle room with b for BBN.
2. There is a noticeable tension between predicted and observed amounts of 7Li,
A. Measurements have an unaccounted systematic error. B. We do not understand the cycling of 7Li in stars.
What we see is not primordial. C. Calculations (e.g. nuclear rates) are wrong.D. New Physics interference. What kind of new physics?
4. Unexpected 6Li problem? Not yet...
Lithium problem
1010)17.023.6( b
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Deuterium and Lithium abundances
Coc et al, ApJ 2004
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Possible astrophysical resolution of 7Li discrepancy
There is a growing suspicion that pop II stars can themselves deplete lithium by admixing it from the atmospheres into a hot interrior where it gets destroyed (Korn et al., 2006, employs diffusion and extra mixing).
Can it provide a factor of 2-3 suppression?
Can the suppression work uniformly along the Spite plateau, without introducing extra scatter?
Would the measured abundances of other elements be OK?
12
Emerging 6Li problem?A lot of speculations about primordial 6Li!
Unexpected plateau (?) of 6Li with metallicity (Asplund et al., 2005)
6Li/H ~ 2 £ 10-11
13
9Be vs metallicityThere is no evidence for primordial values
No serious BBN models ever predicted anything in excess of 10-15
14
More on 7Li generation during the BBNIn fact, it is 7Li+7Be that we are interested in (much later, 7Be
captures an electron and becomes 7Li). Things are simple: there is one reaction in, and one reaction out
3He+ ! 7Be + - IN. 7Be +n ! p +7Li – OUT, (followed by 7Li+p ! 2)At T>25 keV, 7Li is unstable being efficiently burned by protons. 4He, 3He, D, p, and n can be all considered as an input for lithium
calculation.
1. 3He and n abundances ? All reactions are too well-known. 3He is indirectly measured by the solar neutrino flux.
2. 3He(, )7Be reaction is now known with better than 10% accuracy.
New nuclear ways of destroying 7Be ?
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Burning of 7Be using deuterium
It has been suggested (Coc et al., 2004) that if the reaction rate of 7Be(d,p)®® is arbitrarily increased by a factor of ~ 100, the lithium problem can be “solved” right during the BBN.
Subsequent experimental search (Angulo et al., 2005) have shown no enhancement in this reaction.
It is important, however, that the search was made at E~400 keV, and the extrapolation to BBN regime was done assuming smoothness of astrophysical S-factor (cross section).
Such assumptions can be spectacularly violated by the presence of near threshold resonances ( e.g. F. Hoyle, 1950s).
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9B energy levels
from TUNL
nuclear data
project
Zooming in: 16.7 MeV resonance near 7Be +d
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Nothing much is known about 5/2+, 16.7 MeV +/- 100 keV resonance in 9B. Information about mirror nucleus, 9Be, shows that this resonance is extremely narrow.
We (R. Cyburt and MP) try to determine parameters of this resonance phenomenologically, and then see if it can be consistent with nuclear physics/quantum mechanics.
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Parameters of the resonance
Above the black line, 7Li/H < 0.5 [7Li/H]SBBN,
and the Lithium problem is “solved”. One needs a resonance in 160-200 keV range, and Gamma > 10 keV.
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Uncertainty in 7Li due to 9B resonance
¡ ~10 keV is a problem because of the Coulomb screening. Such a large deuterium separation width at a resonance energy of 200 keV implies extremely large radius for the 7Be+d interaction channel, as large as 10 fm. This is border-line of what is allowed by QM.
If indeed lithium problem is solved that way, it implies “new nuclear physics”, i.e. 16.7 MeV resonance in 9B is a 10 fm-size bound
state of 7Li and Deuteron.
Being completely agnostic about properties of this resonance within QM, we arrive at the the following prediction for primordial lithium
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Enlarged error bars for 7Li
Experimental studies of the property of this resonance are required!
21
Nonstandard BBN scenarios
Late injection of electromagnetic/hadronic energy distorts primordial abundances, especially for those elements where the SBBN processes are extremely inefficient
(4He(d,°)6Li is the radiative E2 reaction, suppressed by 8 orders of magnitude relative to “normal” reactions)
Energy injection with baryons in the final stay allows to circumvent this by a chain of endo-thermic but photonless reactions (Dimopoulos et al, 1980s) 4He + p 3H + p + p, Q=-16 MeV
There is a possibility of suppressing 7Be if O(10-5) neutrons per proton are injected (Jedamzik, 2004). This also increases D/H. Typical lifetime ~ 1000 sec is required.
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BBN with energy injectiondecaying dark matter
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BBN with energy injectionannihilating dark matter
Thermal WIMP
benchmark
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Catalyzed BBN Suppose that there is an electroweak scale remnant X- (and X+), e.g. SUSY partner of
electron, or , with the following properties:
1. Masses are in excess of 100 GeV to comply with LEP/Tevatron.
2. Abundances per baryon YX are O(0.1-0.001). In a fully specified model of particle physics they scale as YX » (0.01-0.05)mX/TeV.
3. Decay time X is longer than 1000 sec; no constraints on decay channels.
Are there changes in elemental abundances from mere presence of X-? Yes! Anything at all that sticks to He with bindingenergy between 150 KeV and 1500 KeV will lead to the catalysis of 6Li production!Any quantities of (8BeX) in excess of 10-10 at 8 keV will lead to the
catalysis of 9Be to >10-13 level.
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Properties of bound states
fm7.1 KeV;3.8
fm6.3;KeV350
KeV3972
He22
He
crecomb
b
Bohr
rT
aE
mZE
fm5.2 KeV;35
fm0.1;KeV1350
KeV27872
Be22
Be
crecomb
b
Bohr
rT
aE
mZE
(4HeX-) (7BeX-)Bohr radius is 2 times larger than nuclear Bohr orbit is within nuclear radius
X-
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Recombination of 4He and X-
(4HeX) bottleneck
Naive equilibrium Saha-type equation
gives a rapid switch from 0 to 1 at 8.3 KeV
Realistic solution to Boltzmann equation leads to a gradual increase of the number of bound states. Catalyzed synthesis of 6Li will start below 9keV
)KeV3.8()/exp()2/(1
1
)(
)(2/3
He1
He
-He TTETmnTn
Tn
bX
X
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After bound states have formed, new reaction channels open up
Main SBBN channel for 6Li production4He + D ! 6Li + ; Q = 1.47 MeV
in usual astrophysical units. 6Li(SBBN) » 10-14
NB: typical pre-exponents for reactions are 105-106,
for photon-less reactions 108-1010
Main CBBN channel for 6Li production
(4HeX-) + D ! 6Li + X-; Q = 1.13 MeV
)/435.7exp(30 3/19
3/29 TTvSBBN
)/37.5exp(104.2 3/19
3/29
8 TTvCBBN
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New Reaction Channels
A possible SBBN channel for 9Be production8Be + n ! 9Be + ; Q = 1.66 MeV
9Be(SBBN) » 10-18
Main CBBN channel for 9Be production
(8BeX-) + n ! 9Be + X-; Q = 0.26 MeV
This is a large photonless rate dominated by threshold resonance!
unstable is Beas collisons tripleRequires .0 8vSBBN
9100.2 vCBBN
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6Li and 9Be at 8 KeVCBBN with YX = 5£10-3, X=1 as a typical example,
resulting in 6Li >10-8, and 9Be>10-11 – Excluded!
Observationally, 6Li/H < few£ 10-11; 9Be/H<few£ 10-13,
Therefore, YX(2£104sec) < 10-5 , and typically X < 5£ 103 s.
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6Li and 9Be at 8 KeVCBBN with YX = 10-1, X=2000s as a “just so” scenario
6Li/H=1.3£ 10-11; 9Be/H=7£ 10-14: A very intriguing pattern!!!
9Be/6Li = (2-5)£ 10-3 - a typical “footprint” of CBBN
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Constraints on particle physics models
Type I: X-! SM-[X0], E » MX . Longevity because of small couplings. Examples:NLSP slepton (stau, smuon...) !Gravitino LSPNLSP slepton (stau, smuon...) ! "Dirac" RH sneutrino LSPLong-lived EW scale triplet Higgs decaying to SMType I requires taking care of "nonthermal" BBN effects.
Type II: X-! X0 + e-[]; E » few MeV or less.Longevity because of the small energy release. Examples:Closely degenerate stau-neutralino system Closely degenerate chargino-neutralino (O(MeV) splitting)Dark matter as heavy EW multiplet (O(MeV) splitting)Before CBBN, models of Type II were believed to be unconstrained by physics of
the Early Universe.
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Catalytic suppression of 7Be + 7Li
The “bottleneck” is creation of (7BeX-) bound states that is controlled by 7Be+X-! (7BeX-) + reaction
There are two main destruction channels that are catalyzed: 1. p-reaction: (7BeX-) + p ! (8BX-) + by a factor of >1000 relative to 7Be + p ! 8B + 2. In models with weak current, the “capture” of X- is catalyzed:
(7BeX-) ! 7Li + X0 ,so that lifetime of (7BeX-) becomes ¿ 1 sec. 7Li is significantly more
fragile and is destroyed by protons “on the spot”.3. There is significant energy injection via X+ +X- ! (X+X-) ! radiation. If this process has hadronic modes, it
also affects Li7. 4. Combination of 6Li and 7Li constraints indicates the lifetime
1000-2000 s.
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How likely is such scenario? (SUSY landscape ? :)
Suppose nature chose the weak scale supersymmetry.
There are two types of regular superpartners:
Neutrals: neutralinos, sneutrinos.
Charged: charged sleptons, squarks, charginos
All masses are at ~ TeV or less [one would hope!]
“Probability” of mlightest charged < mlightest neutral
: 50%
Gravitino mass is a free parameter, not linked to weak scale
“Probability” of mgravitino<mlightest charged < mlightest neutral
: 25%
In 25% cases SUSY models would have long-lived
charged or strongly interacting relics!
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Conclusions 1. Lithium problem is a serious discrepancy between SBBN
prediction and Spite plateau value of 7Li abundance. Possibly indicates A. new delicate processes in the atmospheres of pop II stars, B. New nuclear physics channels (easy to check), C. New particles that catalyze 7Be destruction. Or the combination of the above. Last option is generally testable at LHC.
2. Energy injection via decay/annihilation of heavy relics is testable with BBN, especially in the channels that are accidentally suppressed in the standard scenario: 6Li, 9Be.
3. Catalysis of nuclear fusion is a new generic mechanism of how particle physics can affect the BBN predictions for lithium and beryllium. CBBN imposes important constraints on particle physics models that cannot be [yet] probed in other ways; this includes some TeV-scale SUSY models. 6Li and 9Be abundances are drastically enhanced, with ratio 6Li/9Be = (2-5) £ 10-3, affected by mere presence of charged particles during BNN. 7Li+7Be can be suppressed by a factor of ~ 2.