Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Gravitino Production from Heavy Moduli Decay and Cosmological Moduli Problem Revived

Shuntaro Nakamura, Masahiro Yamaguchi

Abstract

The cosmological moduli problem for relatively heavy moduli fields is reinvestigated. For this purpose we examine the decay of a modulus field at a quantitative level. The modulus dominantly decays into gauge bosons and gauginos, provided that the couplings among them are not suppressed in the gauge kinetic function. Remarkably the modulus decay into a gravitino pair is unsuppressed generically, with a typical branching ratio of order 0.01. Such a large gravitino yield after the modulus decay causes cosmological difficulties. The constraint from the big-bang nucleosynthesis pushes up the gravitino mass above 10^5 GeV. Furthermore to avoid the over-abundance of the stable neutralino lightest superparticles (LSPs), the gravitino must weigh more than about 10^6 GeV for the wino-like LSP, and even more for other neutralino LSPs. This poses a stringent constraint on model building of low-energy supersymmetry.

Gravitino Production from Heavy Moduli Decay and Cosmological Moduli Problem Revived

Abstract

The cosmological moduli problem for relatively heavy moduli fields is reinvestigated. For this purpose we examine the decay of a modulus field at a quantitative level. The modulus dominantly decays into gauge bosons and gauginos, provided that the couplings among them are not suppressed in the gauge kinetic function. Remarkably the modulus decay into a gravitino pair is unsuppressed generically, with a typical branching ratio of order 0.01. Such a large gravitino yield after the modulus decay causes cosmological difficulties. The constraint from the big-bang nucleosynthesis pushes up the gravitino mass above 10^5 GeV. Furthermore to avoid the over-abundance of the stable neutralino lightest superparticles (LSPs), the gravitino must weigh more than about 10^6 GeV for the wino-like LSP, and even more for other neutralino LSPs. This poses a stringent constraint on model building of low-energy supersymmetry.

Paper Structure

This paper contains 38 equations, 1 figure.

Figures (1)

  • Figure 1: Constant contours of the density parameter $\Omega_{\chi} h^2$ are drawn in the $m_{\chi}$-$m_{3/2}$ plane. Three real lines represent $\Omega_{\chi} h^2=$0.01, 0.1, and 1, from the above. Also shown by a dashed line is the contour of $\Omega_{\chi} h^2 = 0.13$, approximately corresponding to the 95%CL upperbound of the cold dark matter abundance from the cosmological observations.