| 17 | | * Cone- or $K_{T}$-jet MLM: The final-state partons in an MG/ME event are clustered according to the $K_{T}$-jet algorithm to find the "equivalent parton shower history'' of the event. The Feynman diagram information from !MadGraph is used to allow only clusterings that correspond to diagrams existing in the generated matrix element. For the cone jet algorithm, a minimum $P_T$ and $\Delta R$ must be defined for all partons. For the $K_T$ scheme, the smallest $K_{T}$ value is restricted to be above the cutoff scale "xqcut". In order to closely mimic the behaviour of the parton shower, the $K_{T}$ value for each clustering vertex corresponding to a QCD emission is used as renormalization scale for $\alpha_{s}$ in that vertex. As factorization scale, as well as renormalization scale for the central hard $2\to1$ or $2\to2$ process, the transverse mass $m_{T}^2 = P_{T}^2 + m^2$ of the particle(s) produced in the central process is used. This event is then passed to Pythia for parton showering. After showering, but before hadronization and decays, the final-state partons are clustered into jets; for the cone jet MLM scheme using cone jets, with minimum $P_T > P_T^{ME}$ and $\Delta R=\Delta R^{ME}$, and for the $K_{T}$-jet scheme using $K_{T}$ jets with a cutoff scale $Qcut > xqcut$. These jets are then compared to the original partons from the matrix element event. A jet is considered to be matched to the closest parton if, for the cone jet scheme, the jet is within 1.5$\Delta R$ from the parton, and for the $K_{T}$-jet scheme, if the jet measure $K_{T}(parton,jet)$ is smaller than the cutoff $Qcut$. The event is rejected unless each jet is matched to a parton, except for the highest multiplicity sample, where extra jets are allowed below the $P_T$ or $K_{T}$ scale (for the respective schemes) of the softest matrix element parton in the event. These matching schemes can be used with both the old (vituality-ordered) and the new ($\pt$-ordered) shower implementations of \pythia. |
| | 17 | * Cone- or $K_{T}$-jet MLM: The final-state partons in an MG/ME event are clustered according to the $K_{T}$-jet algorithm to find the "equivalent parton shower history'' of the event. The Feynman diagram information from !MadGraph is used to allow only clusterings that correspond to diagrams existing in the generated matrix element. For the cone jet algorithm, a minimum $P_T$ and $\Delta R$ must be defined for all partons. For the $K_T$ scheme, the smallest $K_{T}$ value is restricted to be above the cutoff scale "xqcut". In order to closely mimic the behaviour of the parton shower, the $K_{T}$ value for each clustering vertex corresponding to a QCD emission is used as renormalization scale for $\alpha_{s}$ in that vertex. As factorization scale, as well as renormalization scale for the central hard $2\to1$ or $2\to2$ process, the transverse mass $m_{T}^2 = P_{T}^2 + m^2$ of the particle(s) produced in the central process is used. This event is then passed to Pythia for parton showering. After showering, but before hadronization and decays, the final-state partons are clustered into jets; for the cone jet MLM scheme using cone jets, with minimum $P_T > P_T^{ME}$ and $\Delta R=\Delta R^{ME}$, and for the $K_{T}$-jet scheme using $K_{T}$ jets with a cutoff scale $Qcut > xqcut$. These jets are then compared to the original partons from the matrix element event. A jet is considered to be matched to the closest parton if, for the cone jet scheme, the jet is within 1.5$\Delta R$ from the parton, and for the $K_{T}$-jet scheme, if the jet measure $K_{T}(parton,jet)$ is smaller than the cutoff $Qcut$. The event is rejected unless each jet is matched to a parton, except for the highest multiplicity sample, where extra jets are allowed below the $P_T$ or $K_{T}$ scale (for the respective schemes) of the softest matrix element parton in the event. These matching schemes can be used with both the old (vituality-ordered) and the new ($P_T$-ordered) shower implementations of \pythia. |
