The file physics constains results for pi+ meson as input and pi+ meson as output. physics1 is for pi- to pi-.
This data frame contains the following columns:
Inverse total energy
Weisberg, H., Beier, H., Brody, H., Patton, R., Raychaudhari, K., Takeda, H., Thern, R. and Van Berg, R. (1978). s-dependence of proton fragmentation by hadrons. II. Incident laboratory momenta, 30–250 GeV/c. Physics Review D, 17, 2875–2887.
Weisberg, S. (2005). Applied Linear Regression, 3rd edition. New York: Wiley, Section 5.1.1.