diff --git a/eic_data.yaml b/eic_data.yaml
index 36add1e1f01c8363c8af8c1bbffb23968887ad2d..ca4b5ed73efa3a557d6fdf6c6d09760710f53496 100644
--- a/eic_data.yaml
+++ b/eic_data.yaml
@@ -223,6 +223,7 @@ components:
       - char              radiator          // Radiator number (0/1/..) in a sequence of the IRTAlgorithm configuration file
       - float             npe               // Overall p.e. count associated with this estimate
       - float             theta             // Cherenkov theta angle
+      - float             rindex            // Average refractive index for this collection of photons
 
 datatypes: