What Mass Are the Smallest Protohalos?
We calculate the kinetic-decoupling temperature for weakly interacting massive particles (WIMPs) in supersymmetric (SUSY) and extra dimensional models that can account for the cold-dark-matter abundance determined from cosmic microwave background measurements. Depending on the parameters of the particle-physics model, a wide variety of decoupling temperatures is possible, ranging from several MeV to a few GeV. These decoupling temperatures imply a range of masses for the smallest protohalos much larger than previously thought—ranging from 10-6M[direct-sum] to 102M[direct-sum]. We expect the range of protohalos masses derived here to be characteristic of most particle-physics models that can thermally accommodate the required relic abundance of WIMP dark matter, even beyond SUSY and extra dimensions.
Additional Information© 2006 The American Physical Society (Received 15 March 2006; revised 8 May 2006; published 18 July 2006) K.S. is supported by NASA through Hubble Fellowship Grant No. HST-HF-01191.01-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under Contract No. NAS 5-26555. S.P. and M.K. are supported in part by DOE No. DE-FG03-92-ER40701 and FG02-05ER41361 and NASA No. NNG05GF69G.
Published - PROprl06.pdf