added cross section unit

Framework/Units/PhysicalConstants.h

@@ -54,7 +54,7 @@ namespace corsika::units::si::constants {
   // unified atomic mass unit
   constexpr quantity<mass_d> u{Rep(1.6605402e-27L) * kilogram};
 
-  // millibarn
+  // barn
   constexpr quantity<area_d> barn{Rep(1.e-28L) * meter * meter};
   
   // etc.

Framework/Units/PhysicalUnits.h

@@ -24,6 +24,31 @@ namespace phys {
   }   // namespace units
 } // namespace phys
 
+namespace phys {
+  namespace units {
+    namespace literals {
+      QUANTITY_DEFINE_SCALING_LITERALS(barn, area_d,
+                                       magnitude(corsika::units::si::constants::barn))
+
+      // phys::units::quantity<energy_d/mass_d> Joule2Kg = c2; // 1_Joule / 1_kg;
+
+    } // namespace literals
+  }   // namespace units
+}
+
+namespace phys {
+  namespace units {
+    namespace literals {
+      QUANTITY_DEFINE_SCALING_LITERALS(meter, length_d,
+                                       magnitude(corsika::units::si::constants::meter))
+
+      // phys::units::quantity<energy_d/mass_d> Joule2Kg = c2; // 1_Joule / 1_kg;
+
+    } // namespace literals
+  }   // namespace units
+}
+
+
 namespace corsika::units::si {
   using namespace phys::units;
   using namespace phys::units::literals;

Framework/Units/testUnits.cc

@@ -54,7 +54,8 @@ TEST_CASE("PhysicalUnits", "[Units]") {
     REQUIRE(1_mol / 1_amol == Approx(1e18));
     REQUIRE(1_K / 1_zK == Approx(1e21));
     REQUIRE(1_K / 1_yK == Approx(1e24));
-
+    //    REQUIRE(1_barn / 1_mbarn == Approx(1e3));
+    
     REQUIRE(1_A / 1_hA == Approx(1e-2));
     REQUIRE(1_m / 1_km == Approx(1e-3));
     REQUIRE(1_m / 1_Mm == Approx(1e-6));