8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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Motivation and Recipe Light gravitinos as WDM Results and Summary

Is gravitino still a warm dark matter candidate?

A. Khmelnitsky

Faculty of Physics, M.V.Lomonosov Moscow State University

Institute for Nuclear Research of the Russian Academy of Sciences, Moscow

15th International Seminar on High Energy Physics,Quarks-2008

Sergiev Posad, Russia, May 23-29, 2008

with D. Gorbunov and V. Rubakov

http://find/http://goback/

8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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Motivation and Recipe Light gravitinos as WDM Results and Summary

CDM Issues

Cold Dark Matter Consistent with Bulk of Cosmological Data

BUT

Some Discrepancies are Observed

Missing Satellites:CDM Predicts too Many Satellite Dwarf GalaxiesCuspy Galactic Density ProfilesToo Low Angular Momenta of Spiral Galaxies

Possible Hints towards Warm Dark MatterWDM: Sizeable Primordial Velocity Dispersions of DMParticles

Another way to quantify: Phase space density

http://find/http://goback/

8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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Motivation and Recipe Light gravitinos as WDM Results and Summary

CDM Issues

Cold Dark Matter Consistent with Bulk of Cosmological Data

BUT

Some Discrepancies are Observed

Missing Satellites:CDM Predicts too Many Satellite Dwarf GalaxiesCuspy Galactic Density ProfilesToo Low Angular Momenta of Spiral Galaxies

Possible Hints towards Warm Dark Matter

WDM: Sizeable Primordial Velocity Dispersions of DMParticles

Another way to quantify: Phase space density

http://find/http://goback/

8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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Motivation and Recipe Light gravitinos as WDM Results and Summary

CDM Issues

z=2

z=1

z=0 CDM WDM1 WDM2

Simulation of structure formation in CDM and WDMscenarios with various masses of DM particles(P. Bode, J. P. Ostriker and N. Turok, 2001)

M i i d R i Li h i i WDM R l d S

http://find/http://goback/

8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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Motivation and Recipe Light gravitinos as WDM Results and Summary

CDM Issues

Cold Dark Matter Consistent with Bulk of Cosmological Data

BUT

Some Discrepancies are Observed

Missing Satellites:CDM Predicts too Many Satellite Dwarf GalaxiesCuspy Galactic Density ProfilesToo Low Angular Momenta of Spiral Galaxies

Possible Hints towards Warm Dark Matter

WDM: Sizeable Primordial Velocity Dispersions of DMParticles

Another way to quantify: Phase space density

http://find/http://goback/

8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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Motivation and Recipe Light gravitinos as WDM Results and Summary

8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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Motivation and Recipe Light gravitinos as WDM Results and Summary

CDM Issues

Cold Dark Matter Consistent with Bulk of Cosmological Data

BUT

Some Discrepancies are Observed

Missing Satellites:CDM Predicts too Many Satellite Dwarf GalaxiesCuspy Galactic Density ProfilesToo Low Angular Momenta of Spiral Galaxies

Possible Hints towards Warm Dark Matter

WDM: Sizeable Primordial Velocity Dispersions of DMParticles

Another way to quantify: Phase space density

Motivation and Recipe Light gravitinos as WDM Results and Summary

http://find/http://goback/

8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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Motivation and Recipe Light gravitinos as WDM Results and Summary

Phase space density

Measurable quantity

Q= v2

radial3/2

Q 5 103 M/pc3

(km/s)3

Estimates typical value of halo particles distribution function

Q m4 n

13p23/2

n

p23/2= fhalo(p, r)d

3p

5/2

fhalo(p, r)p2d3p

3/2

fhalo(p, r)

Thus

fhaloQ

33/2m4

Motivation and Recipe Light gravitinos as WDM Results and Summary

http://find/http://goback/

8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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Motivation and Recipe Light gravitinos as WDM Results and Summary

Warmness Condition

In course of evolution particles leave dense regions ofphase-space Q f decreases by a factor of = 102 103

But only a fraction of dark matter particles should have highphase space density

dSph/DM 105

WDM: Fraction of particles has primordial phase spacedensity

f Q

33/2 m4

Motivation and Recipe Light gravitinos as WDM Results and Summary

http://find/http://goback/

8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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Motivation and Recipe Light gravitinos as WDM Results and Summary

Warmness Condition

In course of evolution particles leave dense regions ofphase-space Q f decreases by a factor of = 102 103

But only a fraction of dark matter particles should have highphase space density

dSph/DM 105

WDM: Fraction of particles has primordial phase spacedensity

f Q

33/2 m4

Motivation and Recipe Light gravitinos as WDM Results and Summary

http://find/http://goback/

8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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p g g y

Warmness Condition

In course of evolution particles leave dense regions ofphase-space Q f decreases by a factor of = 102 103

But only a fraction of dark matter particles should have highphase space density

dSph/DM 105

WDM: Fraction of particles has primordial phase spacedensity

f Q

33/2 m4

Motivation and Recipe Light gravitinos as WDM Results and Summary

http://find/http://goback/

8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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p g g y

Light gravitinos as Warm Dark Matter

Two production channels

Scattering processes:

Total present mass density:

scG

M

100 GeV

2 1keV

mG

TR

1 TeV

Gravitino mass in keV range Low reheat temperature

Decay processes:

Motivation and Recipe Light gravitinos as WDM Results and Summary

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8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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g g y

Production in decays

Decay rate:

M5

6m2G

M2Pl

Total present mass density:

decG 8104

gb +

15

16gf

gMSSM

g

3/2 1keVmG

M

100 GeV

3

Largest contribution comes from heaviest superparticlesSuperparticles mass in 100 GeV range

Motivation and Recipe Light gravitinos as WDM Results and Summary

http://find/http://goback/

8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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Gravitino from decays spectrum

%Fermi-Dirac

rr

TR = 4M

'TR M

%

Fermi-Dirac

'Gravitino from decays

Feature at low reheat temperature

Gravitino from decays are colder than thermal:

Mean momentum is lowerPhase space density is higher

Motivation and Recipe Light gravitinos as WDM Results and Summary

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Two scenarios are considered

M Mq,Mg TR Mq,Mg; M M,M

Motivation and Recipe Light gravitinos as WDM Results and Summary

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Two scenarios are considered

M Mq,Mg TR Mq,Mg; M M,M

Allowed region is too small

Motivation and Recipe Light gravitinos as WDM Results and Summary

http://find/http://goback/

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Results and Conclusion

We find that gravitino is warm dark matter provided that

its mass is in range

1keV mG 25 keV

TR is at most in the TeV range

superparticles whose mass M is below the reheat temperatureobeys

M 350 GeV

Gravitino as warm dark matter candidate will soon be eitherruled out or supported by the LHC experiments.

Motivation and Recipe Light gravitinos as WDM Results and Summary

http://find/http://goback/

8/3/2019 A. Khmelnitsky- Is gravitino still a warm dark matter candidate?

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Results and Conclusion

We find that gravitino is warm dark matter provided that

its mass is in range

1keV mG 25 keV

TR is at most in the TeV range

superparticles whose mass M is below the reheat temperatureobeys

M 350 GeV

Gravitino as warm dark matter candidate will soon be eitherruled out or supported by the LHC experiments.

http://find/http://goback/