Mikko Laine- Hot QCD and Warm Dark Matter

8/3/2019 Mikko Laine- Hot QCD and Warm Dark Matter

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Hot QCD and Warm Dark Matter

Mikko Laine

(University of Bielefeld, Germany)

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Why bother with hot QCD?

Hot QCD theorists:

Heavy ion experimentalists need us.

Heavy ion experimentalists:

It is relevant for cosmology.

95% of cosmologists:

Hot QCD is uninteresting since there is

no strong first order phase transition.

But...

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It appears that there is Dark Matter

Rotation curves

Gravitational lensing of distant galaxies

Large-scale structure formation

Anisotropies in cosmological microwave background

Supernovae distance measurements

Each has unknown systematic uncertainties, yet all canbe explained with a common dm = 0.22 0.04, or

edm 1.1

GeV

m3 ebaryon 0.2

GeV

m3 .3


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What could Dark Matter be?

CDM (Cold Dark Matter): M> 50 GeV.

New particles from SUSY?

WDM (Warm Dark Matter): M>

10 keV.

Right-handed neutrinos?

Peebles 1982

Olive, Turner 1982

Modifications in gravity at large distances, ...

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Minimal model for right-handed (sterile) neutrinos

L = LMSM +1

2 Ns[i/ Ms]Ns[hsL aRNs+H.c.] ,

where generations s, = 1, 2, 3 are summed over.

Active neutrino masses with see-saw: m

|hs|2v2

Ms .Usually: M1,M2,M3 10

10...1015 GeV, |hs|


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How about edm? Experimental constraints

Lower bound from structure formation, upper bound

from X-ray emission from sterile neutrino decays.

s hsvMs .

Review:

Abazajian,

Koushiappas

astro-ph/0605271

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Confront this with a theoretical computation

Basic mechanism for dark matter generation: thermal.

Dodelson, Widrow 1994

T

d

u

e

N1

GF

transition

After production N1 does not interact any more.

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Rate |amplitude|2

the rate can be related to the imaginary part of the

2-point function of active neutrinos:

d

u

e+

N1N1

Or, more generally:

V, A

e+

N1N1

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As formulae Asaka, Laine, Shaposhnikov 2006

Cosmology part:

Td

dT

n1(T)

s(T)

=

1

3c2s(T)s(T)

3m2Pl

8e(T)

d3qR(T, q) .

Relation to active neutrinos:

R(T, q) 1

(2)32|q|

3=1

21M4

1Tr[Q/ Im / ]

[M21

+ 2|q|Re ]2.

Imaginary part of active neutrino self-energy:

Im / (Q) G2

F

d3r

(2)3K |q|T,|q + r|

T

(Q/ + R/ ) V,A

(|q| |q + r|, r) .

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Why does QCD thermodynamics play a role?

Tr[Q/ Im / ] G2

FT6f(|q|/T).

Re G2FT41w |q|.

For |q| T, one then has

R(T,q) M41G2FT6

(M21

+ 100G2FT6)2

,

and the rate is strongly peaked around

T

M1

10GF

13

200 MeV

M1

1 keV

13

.

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Example of numerics

0.00 0.05 0.10 0.15 0.20

dm

200

400

600

T/M

eV

M1

= 10 keV

1

2= 10

-10with = e

hadronicuncertainties

Asaka, Laine, Shaposhnikov, in preparation11


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Main sources of hadronic uncertainties

(1) Equation-of-state, particularly c2s(T), s(T), e(T).

Current status plenary by Urs Heller, etc.

(2) Spectral functions for vector and axial currents.

Current status plenary by Tetsuo Hatsuda, etc.

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Conclusions

The basic WDM scenario is old, but it has recently

experienced a revival, because of progress on

... the experimental side: parameter region stronglyconstrained by structure formation and X-ray bounds,

so one has to be more quantitative than before.

... the theoretical side: there is a minimal model whichmay also explain neutrino masses, baryogenesis, etc.

So need to promote predictions to a higher level ofaccuracy, and for this hot QCD is much needed.

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Mikko Laine- Hot QCD and Warm Dark Matter