Changes between Version 37 and Version 38 of Reweight

Timestamp:

Feb 1, 2016, 9:25:16 PM (9 years ago)

Author:

Olivier Mattelaer

Comment:

--

Reweight

@@ -45 +45 @@
  the final weight is then computed by recombining the weight according to the above formula.
 
- However in MadGraph5_aMC@NLO, we use the virt-tricks method which avoid the computation of the virtual for some of the phase-space points. This speed optimisation method forbids the simple above reweighting since the generation will have $\mathcal{W}_V^{old}=0$ even if $V_{old} \neq 0$. To avoid this problem, $\mathcal{W}_B$ is splitted in two piece :$\mathcal{W}_{BC}$, $\mathcal{W}_{BB}$. $\mathcal{W}_{BC}$ is the part proportional to the born and related to the one counter-term, while $\mathcal{W}_{BB}$ is for the other contribution (the born itself and the approximate virtual).
+ However in MadGraph5_aMC@NLO, we use the virt-tricks method which avoid the computation of the virtual for some of the phase-space points. This speed optimisation method forbids the simple above reweighting since the generation will have $\mathcal{W}_V^{old}=0$ even if $V_{old} \neq 0$. To avoid this problem, $\mathcal{W}_B$ is splitted in two piece :$\mathcal{W}_{BC}$, $\mathcal{W}_{BB}$. $\mathcal{W}_{BC}$ is the part, proportional to the born, related to the one of the counter-terms, while $\mathcal{W}_{BB}$ is for all the other contributions (the born itself and the approximate virtual).
  The reweighting is then done as 
    $$\mathcal{W}_{BB}^{new} = \frac{(B^{new}+V^{new})}{(B^{old}+V^{old})} * \mathcal{W}_{BB}^{old} $$