Changes between Version 11 and Version 12 of ComplexMassScheme

Timestamp:

Aug 13, 2015, 3:04:45 AM (9 years ago)

Author:

Valentin Hirschi

Comment:

--

ComplexMassScheme

@@ -14 +14 @@
 The difference between these two amplitudes must be higher order. More formally, this means $\mathcal{A}^{\text{Born}}_{\text{CMS}}\sim \mathcal{A}^{\text{Born}}_{\Gamma=0} \sim \mathcal{O}(\alpha^a)$. 
 
-Then, if we write $(\mathcal{A}^{\text{Born}}_{\text{CMS}}-\mathcal{A}^{\text{Born}}_{\Gamma=0})/\alpha^a \equiv \Delta^{\text{LO}} = \kappa^{\text{LO}}_0 + \kappa^{\text{LO}}_1 \cdot \alpha + \mathcal{O}(\alpha^2) $, the statement that the difference is higher order is equivalent to state that $\kappa^{\text{LO}}_0=0$. At NLO, this relation translates to :
+At LO, we can write $(\mathcal{A}^{\text{Born}}_{\text{CMS}}-\mathcal{A}^{\text{Born}}_{\Gamma=0})/\alpha^a \equiv \Delta^{\text{LO}} = \kappa^{\text{LO}}_0 + \kappa^{\text{LO}}_1\alpha + \mathcal{O}(\alpha^2) $. The statement that the difference is higher order is then equivalent to state that $\kappa^{\text{LO}}_0=0$. 
 
-$((\mathcal{A}^{\text{Virtual}}_{\text{CMS}}+\mathcal{A}^{\text{Born}}_{\text{CMS}})-(\mathcal{A}^{\text{Virtual}}_{\Gamma=0}+\mathcal{A}^{\text{Born}}_{\Gamma=0}))/\alpha^{a+1} \equiv \Delta^{\text{NLO}} = \kappa^{\text{NLO}}_0 + \kappa^{\text{NLO}}_1 \cdot \alpha + \mathcal{O}(\alpha^2) $
+At NLO, this relation becomes
+$((\mathcal{A}^{\text{Virtual}}_{\text{CMS}}+\mathcal{A}^{\text{Born}}_{\text{CMS}})-(\mathcal{A}^{\text{Virtual}}_{\Gamma=0}+\mathcal{A}^{\text{Born}}_{\Gamma=0}))/\alpha^{a+1} \equiv \Delta^{\text{NLO}} = \kappa^{\text{NLO}}_0 + \kappa^{\text{NLO}}_1\alpha + \mathcal{O}(\alpha^2) $
 
 In order to check that $\kappa^{\text{LO}}_0$ and $\kappa^{\text{NLO}}_0$ are indeed zero, the test proceeds by scaling down all relevant couplings and widths by the parameter $\lambda$ and to evaluate the expressions of $\Delta$ for many progressively smaller values of \lambda but always on the same offshell kinematic configuration. One can then plot the quantities $\Delta^{\text{NLO|LO}}/\lambda$ and make sure that the asymptot for small values of lambda is the constant $\kappa^{\text{NLO|LO}}_1$. Any divergent behavior would be a manifestation of the presence of the term $\kappa^{\text{NLO|LO}}_0/\lambda$ which reveals an issue with the CMS implementation (most likely one of the two points mentioned above) which spoils the expected cancellation.
@@ -28 +29 @@
 
 {{{ MG5_aMC> check cms [-reuse] <process_definition> <options> }}}
+ * Ex.: {{{ check cms -reuse u d~ > e+ ve a [virt=QCD QED] --name=udx_epvea --tweak=['default','allwidths->allwidths*0.99(widths_x_0.99)'] }}}  
 
 First, the '-reuse' following 'cms' specifies that you want to reuse relevant information existing from previous runs. This includes potentially reusing the fortran output of the NLO matrix element if the same process was run before with the 'cms check' command. Also, if a name was given to this run (see option '--name' further) and the corresponding saved result python pickled file exists on disk, this run will be skipped and the result recycled from the pickle file.