MeV Dark Matter With Couplings To Neutrinos
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MeV Dark Matter With Couplings To Neutrinos. Dan Hooper Particle Astrophysics Center Fermi National Accelerator Laboratory [email protected] 2007 Pheno Symposium University of Wisconsin, Madison. 511 keV Emission from the Galactic Bulge.

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Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

MeV Dark Matter With Couplings To Neutrinos

Dan Hooper

Particle Astrophysics Center

Fermi National Accelerator Laboratory

[email protected]

2007 Pheno Symposium

University of Wisconsin, Madison


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

511 keV Emission from the Galactic Bulge

  • INTEGRAL/SPI has observed bright 511 keV emission from the bulge (1.3 x 1043 positrons injected per second)

  • Gaussian, spherically symmetric morphology (FWHM of 8˚)

  • The source of these positrons remains unknown

Dan Hooper - MeV Dark Matter With Couplings to Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

511 keV Emission from the Galactic Bulge

  • Type Ia supernovae are unable to generate the observed injection rate (too few escape)

  • Hypernovae (type Ic SNe) or Gamma Ray Bursts could potentially generate enough positrons if high estimates for rates are considered

  • Even if the injection rate is sufficient, a mechanism is required to transport from disk to bulge - appears difficult

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

511 keV Emission and MeV Dark Matter

  • The INTEGRAL morphology matches well that which would be generated through the annihilation (or decay) of dark matter

  • 1-10 MeV dark matter particles annihilating to e+e- could simultaneously generate the measured dark matter relic abundance, and the observed 511 keV emission

Boehm, Hooper, Silk, Casse, Paul, PRL, astro-ph/0309686

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

511 keV Emission and MeV Dark Matter

  • The INTEGRAL morphology matches well that which would be generated through the annihilation (or decay) of dark matter

  • 1-10 MeV dark matter particles annihilating to e+e- could simultaneously generate the measured dark matter relic abundance, and the observed 511 keV emission

Boehm, Hooper, Silk, Casse, Paul, PRL, astro-ph/0309686

The Mega-tron

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

511 keV Emission and MeV Dark Matter

  • A simple scalar dark matter particle (), annihilating via the s-channel exchange of a new gauge boson (U)

  • Light mediator, lack of Z-coupling avoids stringent LEP (and other) constraints

e-

e+

Boehm, Hooper, Silk, Casse, Paul, PRL, astro-ph/0309686; Boehm and Fayet, Nucl. Phys. B, hep-ph/0305261

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

Coupling to Neutrinos?

  • The U-neutrino-neutrino coupling is not determined by astrophysical or other considerations in this scenario

  • Neutrino-electron scattering experiments place the most stringent constraints

  • If the U coupling to neutrinos is comparable to its coupling to electrons, dark matter-neutrino scattering can be significant

Hooper, M. Kaplinghat, K. Zurek, L. Strigari, astro-ph/0704.2558

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

Kinetic Decoupling

  • Neutrino-dark matter elastic scattering keeps the dark matter in kinetic equlibrium well after the number density freezes out

  • Setting equal to H, yields:

2

Hooper, M. Kaplinghat, K. Zurek, L. Strigari, astro-ph/0704.2558

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

Kinetic Decoupling

  • The kinetic decoupling temperature can be used to estimate the cutoff in the scale scale power spectrum

  • Which in our MeV-dark matter scenario yields:

Hooper, M. Kaplinghat, K. Zurek, L. Strigari, astro-ph/0704.2558

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

MeV Dark Matter and Small Scale Power

  • The matter power spectrum in these scenarios resembles somewhat that found for warm dark matter

m=1 MeV, Tkd=1 keV, 10 keV

Warm DM limit (Ly-)

Hooper, M. Kaplinghat, K. Zurek, L. Strigari, astro-ph/0704.2558

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

MeV Dark Matter & Small Scale Structure

Excluded by (g-2)e

  • If we assume a common coupling to electrons and neutrinos, we find that power is cutoff below 104-107 solar masses

  • For comparison, EW-scale WIMPs feature cutoffs typically around 10-3-10-8 solar masses

Excluded by e scattering

Relic Density OK

Hooper, M. Kaplinghat, K. Zurek, L. Strigari, astro-ph/0704.2558

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

MeV Dark Matter & Small Scale Structure

Excluded by (g-2)e

  • If we assume a common coupling to electrons and neutrinos, we find that power is cutoff below 104-107 solar masses

  • For comparison, EW-scale WIMPs feature cutoffs typically around 10-3-10-8 solar masses

  • After all constraints and issues are considered, suppression of structure below 105-107 solar masses is expected

Excluded by e scattering

Relic Density OK

Fine Tuned

Hooper, M. Kaplinghat, K. Zurek, L. Strigari, astro-ph/0704.2558

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

Missing Satellites?

Excluded by (g-2)e

  • In the upper range of these estimates, suppression could appear in the number of observed Milky Way Satellites (ie. dwarf galaxies)

  • Possible solution to the so-called “missing satellites problem”

Excluded by e scattering

Relic Density OK

Fine Tuned

Hooper, M. Kaplinghat, K. Zurek, L. Strigari, astro-ph/0704.2558

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

High Energy Neutrino Absorption

  • New boson leads to resonant neutrino interactions with the cosmic neutrino background at:

  • For SM Z-boson, this corresponds to E~1021 eV (“Z-burst”)

  • For mU~MeV, E~ TeV

  • Energy redshift broadens the very narrow resonance

  • For couplings larger than ~10-5, efficient absorption occurs over the range: ER/(1+z) < E < ER

Hooper, hep-ph/0701194;

See also Weiler, Palomerez-Ruis, (in preparation)

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

The Neutrinos Are Coming!

  • To date, no (confirmed) sources of high or ultra-high energy neutrinos have been discovered

  • This is likely to change soon

  • Experimental sensitivity is rapidly approaching that needed to detect the first extra-galactic sources of high energy neutrinos

IceCube

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

Extragalactic Sources of High Energy Neutrinos

  • Cosmic ray spectrum of protons/nuclei extends to ~1020 eV

  • pp, p interactions generate neutrinos from cosmic ray sources

  • The flux of neutrinos produced can be tied to the cosmic ray spectrum

  • “Waxman-Bahcall” Argument:

Fraction of proton energy to pions

Accounts for source evolution, etc. (~1)

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

High Energy Neutrino Absorption

  • Observing an absorption feature in the high energy neutrino spectrum will be challenging

  • Requires good neutrino energy resolution (+shower)

  • Large volume, high resolution (small PMT spacing) experiment

  • Realistic goal for future designs

(log E)~0.1,

E2 dN/dE~ 10-7 GeV/cm2 s (high z),

10 km3 yr exposure

Hooper, hep-ph/0701194

Dan Hooper - MeV Dark Matter With Couplings To Neutrinos


Dan hooper particle astrophysics center fermi national accelerator laboratory dhooper fnal

Conclusions

  • The predictions for small scale structure can be very different in MeV dark matter scenarios than for ordinary CDM WIMPs

  • Power below 104-107 solar masses is suppressed

  • Presents a possible solution to the missing satellites problem

  • Scenario can be tested by searching for ~TeV absorption lines in the cosmic neutrino spectrum


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