### 33 f(-p_{1}) + f(-p_{2}) → Z(→ b(p_{3}) + b(p_{4}))

#### 33.1 Z-boson production, processes 31–33

These processes represent the production of a Z boson which subsequently decays
either into electrons (nproc=31), neutrinos (nproc=32) or bottom quarks
(nproc=33). Where appropriate, the effect of a virtual photon is also included.
As noted above, for nproc=31 and nproc=33 the constraint m34min > 0 is
obligatory. The calculation may be performed at LO, NLO and NNLO [1, 2]
although the NLO and NNLO calculation of process 33 does not include
radiation from the bottom quarks (i.e. radiation occurs in the initial state
only).

This process can be calculated at LO, NLO, and NNLO. NLO calculations can be
performed by subtraction, zero-jettiness slicing and q_{T}-slicing. NNLO calculations
can be performed by zero-jettiness slicing and q_{T}-slicing.

To calculate the total cross section to on-shell Z bosons, we take process
(nproc=32), (no γ^{*} contribution) and set (zerowidth=.true.) and (removebr =.true.).
When removebr is true in process 31, the Z boson does not decay.

#### 33.2 Plotter

nplotter_Z_only.f is the default plotting routine.

#### 33.3 Example input and output file(s)

input33.ini process33.out

### References

[1]
R. Boughezal,
J.M. Campbell,
R.K. Ellis,
C. Focke,
W. Giele,
X. Liu
et al.,
Color
singlet
production
at
NNLO
in
MCFM,
Eur.
Phys.
J.
C
77
(2017)
7
[1605.08011].

[2]
J.M. Campbell,
R.K. Ellis
and
S. Seth,
Non-local
slicing
approaches
for
NNLO
QCD
in
MCFM,
2202.07738.