SLIDE 7 NLO weight for re-weighting LO parton shower events
for the q¯ q channel in the KrkNLO, in terms of Sudakov variables α and β
dσNLO
nF nB =
“ 1 + ∆VS +
nF
X
i=1
W [1]
q¯ q (˜
αF
i , ˜
βF
i ) + nB
X
j=1
W [1]
q¯ q (˜
αB
j , ˜
βB
j )
” dσLO
nF nB , W [1]
q¯ q =
d5 ¯ βq¯
q
d5σLO
q¯ q
= d5σNLO
q¯ q
− d5σLO
q¯ q
d5σLO
q¯ q
, ∆q¯
q VS =
αs 2π CF » 4 3 π2 − 5 2 – , ∆qg
VS = 0.
d5σNLO
q¯ q
(α, β, Ω) = CF αs π dαdβ αβ dϕ 2π dΩ " dσ0(ˆ s, θF ) dΩ (1 − β)2 2 + dσ0(ˆ s, θB ) dΩ (1 − α)2 2 # , d5σLO
q¯ q (α, β, Ω) = d5σF q¯ q + d5σB q¯ q =
CF αs π dαdβ αβ dϕ 2π dΩ 1 + (1 − α − β)2 2 dσ0 dΩ `ˆ s, ˆ θ ´ ,
◮ Kinematics and LO PS differential distribution σLO
nF nB to be defined below.
◮ Important point: As pointed out in [arXiv:1209.4291 ], for getting complete NLO corrections to the hard process, it is enough to retain in the above sums over gluons P
j only a single
term, the one with the maximum k2
T from one of the two showers.
◮ In the case of the backward evolution algorithm and kT -ordering, retained gluon is just the
- ne which was generated first.
◮ This exploits Sudakov suppression as POWHEG, but no need of truncated shower for angular ordering.
- S. Jadach (IFJ PAN, Krakow)
NLO corrections in the parton shower Monte Carlo Ustro´ n, Sept.2015 7 / 17
