NLO Vector Boson Production With Light Jets Page: 3 of 5
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NLO VECTOR BOSON PRODUCTION WITH LIGHT JETS
l0
o'
10'
105
05
05
04
3 0
N 02
01100 150
100 150
50 100 150 50 100 150
First Jet pT [GeV] Second Jet pT [GeV]100 150
50 100 150
Third Jet pT [GeV]Fig. 1. PT distributions for the first four jets in Z+4 jets at the LHC with s = 7 TeV, as
well as ratios to W+ and W-. Details of the experimental cuts can be found in ref. [13].
A left-handed W+ that decays leptonically will preferentially emit the neutrino along
its flight direction, whereas the positron will tend to be emitted in the opposite direction
(in the W rest frame), resulting in a larger average transverse momentum for the neutrino
than for the positron. The opposite effect happens in the case of the decaying left-handed
W- boson: the electron inherits a larger average transverse momentum than the anti-
neutrino. This asymmetry in the transverse momentum of the decay products is not
present if the vector boson is longitudinally polarised. Fig. 2 illustrates the phenomenon
in density plots for the ratio of Ws arising from top-quark decays to those from prompt
production at the LHC fi= 7 TeV and cuts chosen as in ref. [5]:a (pp tt
z
W + 3 jets) dd (pp -W + 3 jets) .One can see in the figure that in the case of the W+ bosons, prompt production tends
to populate more the region where the transverse momentum of the neutrino is larger
than that of the positron, while the opposite effect is seen for the W- boson. A suitable
cut, or the addition of such information in statistical analysis tools such as boosted
decision trees or neural networks could help discriminate between these two processes.
The predominant left-handedness of prompt W bosons at the LHC with PT > 50 GeV
has been measured by the CMS collaboration [15] and found to be in good agreement
with theoretical predictions [5].
4. - Conclusions
The field of NLO corrections for high-multiplicity final states has seen tremendous
progress in the last few years, as exemplified by the first computations of 2 -> 5 processes.3
- - LO Z / ,y*+ 4 jets + X = 7TeV BlackHat+Sherpa
- NLO
10
p > 25 GeV, I i < 3 10
p > 20 GeV, I11I < 25
66 GeV < M <116 GeV LO scale dependence
R = 05 [eetl-kr - NLO scale dependence . F = HT /2 to'
-- LO/NLO
05
--- LO Z/W -- LO Z/W+ " 05
. NLO Z/W . -NLO Z/W -- 04100 150
50 100 150
Fourth Jet pT [GeV]01
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Bern, Z.; Diana, G.; Dixon, L.J.; Febres Cordero, F.; Forde, D.; Gleisberg, T. et al. NLO Vector Boson Production With Light Jets, article, February 15, 2012; United States. (https://digital.library.unt.edu/ark:/67531/metadc831187/m1/3/: accessed March 29, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.