Lower and upper bounds on CSL parameters from latent image formation and IGM heating

We study lower and upper bounds on the parameters for stochastic state vector reduction, focusing on the mass-proportional continuous spontaneous localization (CSL) model. We show that the assumption that the state vector is reduced when a latent image is formed, in photography or etched track detection, requires a CSL reduction rate parameter λ that is larger than conventionally assumed by a factor of roughly 2 × 10^9±2, for a correlation length r_C of 10^-5cm. We reanalyse existing upper bounds on the reduction rate and conclude that all are compatible with such an increase in λ. The best bounds that we have obtained come from a consideration of heating of the intergalactic medium (IGM), which shows that λ can be at most ~10^8±1 times as large as the standard CSL value, again for r_C = 10^-5cm. (For both the lower and upper bounds, quoted errors are not purely statistical errors, but rather are estimates reflecting modelling uncertainties.) We discuss modifications in our analysis corresponding to a larger value of r_C. With a substantially enlarged rate parameter, CSL effects may be within range of experimental detection (or refutation) with current technologies.