-- LauraReina - 2015-12-21
# Standard setup for the calculation of tTV (V=Z,W^{+},W^{-}) at NLO QCD

### General framework

#### Setup

**QCD scales and variations** #### Analysis

### ttV recommended cross sections at 13 TeV using fixed scale (mt+mV/2)

Correlation effects are consistently included in the uncertainties of the combined ttW- + ttW+ cross section.

We propose to present a comparison among existing NLO QCD tools. EW corrections will be discussed in a separate section, where the impact of heavy-boson radiation (tTVV) will also be briefly discussed.

We propose to compare results from:

- MG5_aMC@NLO 2.3.2
- Powhel
- Sherpa2.2.0+Openloops1.2.3

We also suggest to postpone presenting results for tT+photon to future studies that would also include multiple photon emission, radiative top decays, and a study of QED showers.

All input parameters should be chosen in compliance with the official Higgs HXSWG note https://cds.cern.ch/record/2047636/files/LHCHXSWG-INT-2015-006.pdf unless otherwise necessary. Small deviations from the recommendation are possible if they are not likely to substantially affect the results. In particular we recommend:

**Specific input parameters and PDFs**

- consider sqrt(s)=13 TeV;
- use MH=125 GeV and mt=172.5 GeV (see recommendation);
- electroweak parameters should be computed in the Gmu scheme, i.e. using Gmu and the on-shell W and Z masses as input parameters
- use NLO PDF4LHC15;
- 5F scheme.

- calculate total cross sections using both fixed (with central value mu0=mt+MV/2) and dynamical (with central value mu0=HT/2) renormalization/factorization scale, where HT=sum of t,T,V transverse energies (ignoring extra jet emissions)
- calculate distributions using dynamical renormalization/factorization scale mu0=HT/2.
- estimate the scale uncertainty with the usual independent factor-2 variations of (muR,muF) excluding antipodal variations.

We propose to keep the final-state particles (tTV) stable (no decays) and to consider the following observables:

- total cross section
- pT of t,T,V (20 bins from 0,500 GeV)
- eta of t,T,V (20 bins from -4,4)
- pT of tTV and tT system (20 bins from 0,500 GeV)
- pT of 1st light jet (non-b jets) with R=0.4 anti-kT algorithm and eta<2.5 (20 bins from 25,525 GeV)
- geometric average of t,T,V transverse energies (20 bins from 0,1000 GeV)
- HT=sum of t,T,V transverse energies (ignoring extra jet emissions) (20 bins from 400,1000 GeV)

**Rivet analyses**

The Rivet routine that implements the above analysis (as well as example plots) can be found at this URL

- hxswg_ttv_stable = generic analysis for tTV+X final states with V=Z,W+,W- (stable top quarks and bosons)

Process | XS [fb] | scale | alpha_S | |

ttZ | 839.3 | + 9.6% −11.3% | ±2.8% | ±2.8% |

ttW+ | 397.6 | +12.7% −11.4% | ±2.0% | ±2.6% |

ttW- | 203.2 | +13.3% −11.7% | ±2.1% | ±2.9% |

ttW- + ttW+ | 600.8 | +12.9% -11.5% | ±2.0% | ±2.7% |

This topic: LHCPhysics > LHCHXSWG > LHCHXSWG1 > LHCHXSWGTTH > ProposaltTV

Topic revision: r12 - 2020-04-02 - LauraReina

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