Vector Boson Jets with BlackHat and Sherpa Page: 4 of 6
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D. Maitre et al.
II ' ' '
- ._. s-= 196TeV - NLOparton
10- - NLO hadron
- DO data
p7> 20GeV, I ] < 25 _- -
65 GeV < M <115 GeV
R = 05 [sswoe] BlackHat+Sherpa
- LO hadron / NLO hadron NLO scale ependence
2 - NLO parton / NLO hadron < LO scaled pendence
- DO data / NLO hadron
Third Jet PT [GeV]
50 100 150 200 250
Third Jet PT [ GeV ]
Figure 2. The left plot shows 1/o-z, x d-/dpT at for the third-hardest jet in Z, -* + 3-jet production, comparing
DO data against LO and NLO predictions. In the upper panel the parton-level NLO distributions are the solid
(black) histograms, while the NLO distributions corrected to hadron level are given by dash-dot (magenta)
histograms. The DO data is indicated by the (red) points. The LO predictions corrected to hadron level are
shown as dashed (blue) lines. The lower panel shows the distribution normalized to the full hadron-level NLO
prediction. The scale-dependence bands in the lower panels are shaded (gray) for NLO and cross-hatched (brown)
for LO. The right plot shows the d-/dpT distribution for the third-hardest jet at the LHC running at 7 TeV, with
the indicated cuts. The complete color dependence is included in this plot, but no corrections to hadron level are
normally operates for production runs, whereas
-target is a target value computed by BLACKHAT
using higher-precision arithmetic of at least 32
digits. The phase-space points are selected in the
same way as those used to compute cross sections.
As seen in fig. 3, no point has a relative errors
larger than about one part in 100; this level of
precision is more than adequate for phenomeno-
What about the real corrections? In fig. 4
we show a pT-distribution for the real-emission
contributions, including dipole subtractions. Al-
though these contributions are not physically
meaningful by themselves (they need to be com-
bined with dipole terms and the virtual correc-
tions, and at the very least summed over other
single-quark-line subprocesses), they do serve to
illustrate that our SHERPA-based integration
setup has them under control. In this calcula-
tion, we used the anti-kt algorithm and took the
center of mass energy to be 7 TeV. We applied
a jet cut of PT > 25 GeV, along with other cuts
on the leptons and the rapidities of the jets. This
plot is based on a calculation that used 2 x 108
phase-space points, yielding the rather small inte-
gration errors indicated by the thin vertical lines.
Two key improvements in our setup which make
the real contributions feasible are an improved in-
tegrator [14,8] and more efficient nine-point tree-
level amplitudes generated by BLACKHAT using
on-shell recursion relations .
A publicly available version of BLACKHAT is
under construction and is being tested in a va-
riety of projects (see e.g. ref. ). This version
uses the Binoth Les Houches interface . It has
been tested with both C++ and Fortran clients.
We intend the public version to provide all pro-
50 100 150 200 250 300 3
Z/y*+3jets+X -- LO
.. s = 7 TeV
Ra - F T r/
.. p > 25 GeV, Iy ,2 < 3
Ei > 20 GeV, 1 p < 25
66 GeV < Al <116 GeV ---
R = 04 [siscone] Bla&kHat+Sherpa
--LO / NLO NLO scale dependence
SLO scale dependence
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Berger, C.F.; /MIT, LNS; Bern, Z.; /UCLA; Dixon, Lance J.; /SLAC et al. Vector Boson Jets with BlackHat and Sherpa, article, August 25, 2010; [California]. (https://digital.library.unt.edu/ark:/67531/metadc1012228/m1/4/: accessed March 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.