[mini] Fix b0 calculation in collisions (#958)

* fix error in b0 calculation

* reset benchmark because an error in the collisions was fixed

---------

Co-authored-by: Tools <hipace.tools@desy.de>

src/particles/collisions/UpdateMomentumPerez.H

@@ -115,6 +115,7 @@ void UpdateMomentumPerezElastic (
         // Compute b0
         T_R const b0 = amrex::Math::abs(q1*q2) * inv_c2 /
                (T_R(4.0)*MathConst::pi*PhysConstSI::ep0) * gc/mass_g *
+               ( m1*g1s*m2*g2s/(p1sm*p1sm*inv_c2) + T_R(1.0) ) *
                ( m1*g1s*m2*g2s/(p1sm*p1sm*inv_c2) + T_R(1.0) );
 
         // Compute the minimal impact parameter

tests/checksum/benchmarks_json/collisions.SI.1Rank.json

@@ -1,21 +1,21 @@
 {
   "lev=0": {
-    "Bx": 185894.49970857,
-    "By": 185895.56149722,
-    "Bz": 5398.3222513339,
-    "ExmBy": 84160567478008.0,
-    "EypBx": 84160440559263.0,
-    "Ez": 71704816487098.0,
-    "Psi": 1089584703.5587,
-    "Sx": 5219478972547400.0,
-    "Sy": 5219255132250900.0,
-    "chi": 4056826099294100.0,
-    "jx": 1.4609565125223e+16,
+    "Bx": 185895.73026042,
+    "By": 185896.51121669,
+    "Bz": 5397.3617493578,
+    "ExmBy": 84160800520468.0,
+    "EypBx": 84160737818435.0,
+    "Ez": 71704902663921.0,
+    "Psi": 1089584989.4535,
+    "Sx": 5219436746330300.0,
+    "Sy": 5219267801701100.0,
+    "chi": 4056826200594800.0,
+    "jx": 1.4609509906637e+16,
     "jx_beam": 0.0,
-    "jy": 1.4609736131743e+16,
+    "jy": 1.4609638654652e+16,
     "jy_beam": 0.0,
     "jz_beam": 1.0840992316526e+16,
-    "rhomjz": 178184621.6204
+    "rhomjz": 178181264.72285
   },
   "beam": {
     "charge": 1.1933011570032e-15,