Limits On Large Extra Dimensions Based On Observations Of Neutron Stars With The Fermi-Large Area Teleoscope
Abstract
We present limits related to the large extra dimensions (LED) model, from the gamma-ray flux of 6 gamma-ray faint neutron stars, using data from the Fermi Large Area Telescope (Fermi-LAT). We assume that Kaluza-Klein (KK) gravitons as predicted in this model are produced in supernova cores, that they are gravitationally retained as neutron stars are formed, and that their decay could contribute to a gamma-ray flux. Considering between 2 and 7 additional spatial dimensions in the context of the LED model, we develop spectral energy distributions (SEDs) of gamma-rays arising from decays of KK gravitons in the vicinity of neutron stars. The SEDs for each number of extra dimensions, n, and each source, are generated by Monte Carlo simulation. Based on 1 year of data from the Fermi-LAT, 95% C.L. upper limits on the size of extra dimensions R from each source are obtained, as well as 95% C.L. lower limits on the (n+4)-dimensional Planck scale, M_D. We obtain combined 95% C.L. upper limits from all the sources on the extra dimensions size, R (m), of 9.0E-9, 3.7E-11, 2.5E-12, 5.0E-13, 1.7E-13, 8.3E-14 for n = 2, 3,. . . ,7. We also obtain 95% C.L. lower limits on the extra-dimensional effective Planck mass, M_D (TeV) of 230, 15, 2.5, 0.66, 0.24, and 0.11 for n = 2,3,. . . ,7. The limits are more stringent than collider limits, for n < 4, and comparable to LHC results for n = 4. We conclude that if the Planck scale is around a TeV, then for n = 2 or 3, the compactification topology must be more complicated than a torus. For extra dimensions of the same size, n ≥ 4 are favored from our results.
- Publication:
-
AAS/High Energy Astrophysics Division #12
- Pub Date:
- September 2011
- Bibcode:
- 2011HEAD...12.4211B