Muon Spin Relaxation Rates as a Limit on Fluctuating Torsion Fields in Solids

This paper examines how precisely muon spin relaxation in a solid sample limits fluctuating spin couplings at the muon site. The system considered is positive muons implanted in a solid with field sensitivity near 10 microtesla, and the observable is relaxation rate, local-field sensitivity and the implied coupling limit. Evaluating the ordinary behaviour of the system and the spin-torsion contribution under explicit assumptions about polarisation and uniformity, and inverting the comparison at the stated laboratory precision, gives a quantitative bound rather than a qualitative assertion of smallness. The computed record is: field_sensitivity_T = 1.000e-05; energy_J = 4.490e-31; torsion_bound_per_m = 1.420e-05; relaxation_rate_per_s = 8516; muon_lifetime_s = 2.197e-06. The torsion-related contribution is far below the level that would alter the ordinary behaviour of the system at current precision, and the value that would have produced a visible residual is stated so that future improvements can be assessed against it directly. No new measurement is reported. This study is simulated and computed from stated assumptions, not measured.