Evidence of Dark Matter? 130-GeV gamma rays from near our galaxy's core

[lpetrich]

The Reference Frame: A confirmation of the 130 GeV dark matter-like bump - Lubos Motl
[1204.2797] A Tentative Gamma-Ray Line from Dark Matter Annihilation at the Fermi Large Area Telescope - Christoph Weniger

The observation of a gamma-ray line in the cosmic-ray fluxes would be a smoking-gun signature for dark matter annihilation or decay in the Universe. We present an improved search for such signatures in the data of the Fermi Large Area Telescope (LAT), concentrating on energies between 20 and 300 GeV. Besides updating to 43 months of data, we use a new data-driven technique to select optimized target regions depending on the profile of the Galactic dark matter halo. In regions close to the Galactic center, we find a 4.6 sigma indication for a gamma-ray line at 130 GeV. When taking into account the look-elsewhere effect the significance of the observed excess is 3.3 sigma. If interpreted in terms of dark matter particles annihilating into a photon pair, the observations imply a dark matter mass of 129.8\pm2.4^{+7}_{-13} GeV and a partial annihilation cross-section of <\sigma v> = 1.27\pm0.32^{+0.18}_{-0.28} x 10^-27 cm^3 s^-1 when using the Einasto dark matter profile. The evidence for the signal is based on about 50 photons; it will take a few years of additional data to clarify its existence.

[1205.1045] Fermi 130 GeV gamma-ray excess and dark matter annihilation in sub-haloes and in the Galactic centre - Elmo Tempel, Andi Hektor, Martti Raidal

We analyze publicly available Fermi-LAT high-energy gamma-ray data and confirm the existence of clear spectral feature peaked at $E_\gamma= 130$ GeV. Scanning over the Galaxy we identify several disconnected regions where the observed excess originates from. Our best optimized fit is obtained for the central region of Galaxy with a clear peak at 130 GeV with statistical significance $4.5\sigma.$ The observed excess is not correlated with Fermi bubbles. We compute the photon spectra induced by dark matter annihilations into two and four standard model particles, the latter via two light intermediate states, and fit the spectra with data. Since our fits indicate sharper and higher signal peak than in the previous works, data disfavors all but the dark matter direct two-body annihilation channels into photons. If Einasto halo profile correctly predicts the central cusp of Galaxy, dark matter annihilation cross-section to two photons is of order ten percent of the standard thermal freeze-out cross-section. If the observed gamma-ray excess comes from dark matter annihilations, we have identified the most dense dark matter sub-structures of our Galaxy. The large dark matter two-body annihilation cross-section to photons may signal a new resonance that should be searched for at the CERN LHC experiments.

Almost but not quite 5 standard deviations, but if this result holds up, it will be indirect evidence of dark matter.

Annihilation radiation has already been observed for a more familiar sort of system: The all-sky distribution of 511 keV electron-positron annihilation emission

 

[twofish-quant]

Interesting...

Since 130 GeV happens to be order of magnitude of the possible Higgs Boson at LHC

http://blog.vixra.org/2011/08/13/has-the-lhc-seen-the-higgs-boson-at-144-gev/

Yes I know 130 != 144, but I'm a theoretical astrophysicist so it's close enough.

 

[Whovian]

Interesting.

 

[Chronos]

It will be interesting to see the results of the last run at LHC.

 

[Drakkith]

Interesting. I'm curious, would 130 GeV gamma rays interact in a specific way with the interstellar medium? Would there be a way to detect these gamma rays other than by direct detection by space telescopes?

 

[mfb]

Interesting...

Since 130 GeV happens to be order of magnitude of the possible Higgs Boson at LHC

http://blog.vixra.org/2011/08/13/has-the-lhc-seen-the-higgs-boson-at-144-gev/

Yes I know 130 != 144, but I'm a theoretical astrophysicist so it's close enough.

144 GeV has been excluded (was just a fluctuation), but there is a strong signal at ~125 GeV, even closer to the 130. However, there is no process which can convert such a Higgs into photons with a peak at 130 GeV. A Higgs mass of 260 GeV would allow that, but that is excluded and I don't see any mechanism which would generate enough Higgs bosons to detect their decay products in astronomy.

I'm curious, would 130 GeV gamma rays interact in a specific way with the interstellar medium?

Not different from 100 and 160, I think.

Would there be a way to detect these gamma rays other than by direct detection by space telescopes?

If their interaction with ordinary matter is strong enough, they might get detected in the LHC. The signature would look different there, depending on the properties of the dark matter particles.

 

[lpetrich]

Higgs particles cannot be dark matter, because they are too short-lived for that. A dark-matter particle ought to be able to survive for the age of the Universe, and the purported Higgs particle does not even make it outside the LHC's beam pipes.

So it's a curious coincidence.

Back to that 130-GeV particle, I've found some papers in arxiv about what it could possibly be. So from two-photon annihilation alone we can't tell much about it. It likely has various other annihilation modes, but they will likely produce a continuum spectrum and thus may be hard to distinguish.

If WIMP direct-detection experiments succeed, they will provide additional clues, especially if they discover evidence of a 130-GeV WIMP. Different experiments use different detector materials, so one might be able to disentangle the spin-independent and spin-dependent effects of both protons and neutrons. That means at least 4 experimental numbers, and that will provide more constraints for theoretical models.

 

[twofish-quant]

Higgs particles cannot be dark matter, because they are too short-lived for that. A dark-matter particle ought to be able to survive for the age of the Universe, and the purported Higgs particle does not even make it outside the LHC's beam pipes.

So it's a curious coincidence.

I'm not sure that it is a coincidence. 100 GeV is the energy scale for electroweak unification and I'd guess that Higgs mass, dark matter masses, and this energy scale are connected in some weird way.

Back to that 130-GeV particle, I've found some papers in arxiv about what it could possibly be.

It's funny since it looks like every theorist with his pet particle is advancing it as a candidate for the signal. Since there isn't much data yet, not much is excluded.

If WIMP direct-detection experiments succeed, they will provide additional clues, especially if they discover evidence of a 130-GeV WIMP. Different experiments use different detector materials, so one might be able to disentangle the spin-independent and spin-dependent effects of both protons and neutrons. That means at least 4 experimental numbers, and that will provide more constraints for theoretical models.

Or we could find that it's a statistical fluke or some sort of instrument error. It looks like that we'll at least know if it is "real" in the next 6-8 months.