Are direct search experiments sensitive to all spin-independent weakly interacting massive particles?

Area of Science:

• Particle Physics
• Astrophysics
• Cosmology

Background:

• Direct detection experiments search for weakly interacting massive particles (WIMPs), a leading dark matter candidate.
• Standard analyses assume spin-independent WIMP interactions are also isospin independent.
• This assumption may not hold, potentially affecting experimental interpretations.

Purpose of the Study:

• To investigate the impact of isospin-dependent interactions on spin-independent WIMP-nucleus scattering.
• To determine revised limits for WIMP detection experiments under this alternative scenario.
• To establish a model-independent framework for analyzing such scenarios.

Main Methods:

• Developed a model-independent framework to analyze WIMP-nucleus interactions.
• Calculated spin-independent WIMP-nucleus cross sections considering isospin dependence.
• Applied the framework to existing experimental data from leading WIMP detection experiments.

Main Results:

• Spin-independent WIMP-nucleus cross sections are significantly quenched in an isospin-dependent scenario.
• Leading experiments set limits 1-2 orders of magnitude less stringent than traditional analyses.
• The discrepancy between CDMS-II and ZEPLIN-I limits is notably reduced in the isospin-dependent case.

Conclusions:

• The assumption of isospin independence in WIMP searches can lead to overly stringent limits.
• Isospin-dependent interactions provide a more comprehensive interpretation of WIMP detection data.
• Revised model-independent limits are crucial for accurate dark matter searches.