98 research outputs found
QCD corrections to tri-boson production
We present a computation of the next-to-leading order QCD corrections to the
production of three Z bosons at the LHC. We calculate these corrections using a
completely numerical method that combines sector decomposition to extract
infrared singularities with contour deformation of the Feynman parameter
integrals to avoid internal loop thresholds. The NLO QCD corrections to pp ->
ZZZ are approximately 50%, and are badly underestimated by the leading order
scale dependence. However, the kinematic dependence of the corrections is
minimal in phase space regions accessible at leading order.Comment: 15 pages, 3 figures; typos fixed, references and event listing adde
t \bar{t} W production and decay at NLO
We present results for the production of a top pair in association with a
W-boson at next-to-leading order. We have implemented this process into the
parton-level integrator MCFM including the decays of both the top quarks and
the W-bosons with full spin correlations. Although the cross section for this
process is small, it is a Standard Model source of same-sign lepton events that
must be accounted for in many new physics searches. For a particular analysis
of same-sign lepton events in which b-quarks are also present, we investigate
the effect of the NLO corrections as a function of the signal region cuts.Comment: 10 pages, 7 figure
Associated production of a Kaluza-Klein excitation of a gluon with a t t(bar) pair at the LHC
In Randall-Sundrum models, the Kaluza-Klein (KK) excitations of the gluon,
g_{KK} have enhanced couplings to the right-handed quarks. In the absence of a
gg g_{KK} coupling in these models, the single production of a g_{KK} from an
initial gg state is not possible. The search for other production mechanisms at
the LHC, therefore, becomes important. We suggest that the associated
production of a g_{KK} with a t t(bar) pair is such a mechanism. Our study
shows that through this process the LHC can probe KK gluon masses in the range
of 2.8 -- 2.9 TeV.Comment: 11 pages, 3 figure
Second order QCD corrections to inclusive semileptonic b \to Xc l \bar \nu_l decays with massless and massive lepton
We extend previous computations of the second order QCD corrections to
semileptonic b \to c inclusive transitions, to the case where the charged
lepton in the final state is massive. This allows accurate description of b \to
c \tau \bar \nu_\tau decays. We review techniques used in the computation of
O(\alpha_s^2) corrections to inclusive semileptonic b \to c transitions and
present extensive numerical studies of O(\alpha_s^2) QCD corrections to b \to c
l \bar \nu_l decays, for l =e, \tau.Comment: 30 pages, 4 figures, 5 table
Physics at a 100 TeV pp collider: Higgs and EW symmetry breaking studies
This report summarises the physics opportunities for the study of Higgs
bosons and the dynamics of electroweak symmetry breaking at the 100 TeV pp
collider.Comment: 187 pages, 94 figures. Chapter 2 of the "Physics at the FCC-hh"
Repor
The fully differential hadronic production of a Higgs boson via bottom quark fusion at NNLO
The fully differential computation of the hadronic production cross section
of a Higgs boson via bottom quarks is presented at NNLO in QCD. Several
differential distributions with their corresponding scale uncertainties are
presented for the 8 TeV LHC. This is the first application of the method of
non-linear mappings for NNLO differential calculations at hadron colliders.Comment: 27 pages, 13 figures, 1 lego plo
Complete off-shell effects in top quark pair hadroproduction with leptonic decay at next-to-leading order
Results for next-to-leading order QCD corrections to the pp(p\bar{p}) -> t
\bar{t} -> W^+W^- b\bar{b} -> e^{+} \nu_{e} \mu^{-} \bar{\nu}_{\mu} b \bar{b}
+X processes with complete off-shell effects are presented for the first time.
Double-, single- and non-resonant top contributions of the order
{\cal{O}}(\alpha_{s}^3 \alpha^4) are consistently taken into account, which
requires the introduction of a complex-mass scheme for unstable top quarks.
Moreover, the intermediate W bosons are treated off-shell. Comparison to the
narrow width approximation for top quarks, where non-factorizable corrections
are not accounted for is performed. Besides the total cross section and its
scale dependence, several differential distributions at the TeVatron run II and
the LHC are given. In case of the TeVatron the forward-backward asymmetry of
the top is recalculated afresh. With inclusive selection cuts, the
forward-backward asymmetry amounts to A^{t}_{FB} = 0.051 +/- 0.0013.
Furthermore, the corrections with respect to leading order are positive and of
the order 2.3% for the TeVatron and 47% for the LHC. A study of the scale
dependence of our NLO predictions indicates that the residual theoretical
uncertainty due to higher order corrections is 8% for the TeVatron and 9% for
the LHC.Comment: 35 pages, 39 figures, 3 tables. References and note added, version to
appear in JHE
The SM and NLO multileg working group: Summary report
This report summarizes the activities of the SM and NLO Multileg Working
Group of the Workshop "Physics at TeV Colliders", Les Houches, France 8-26
June, 2009.Comment: 169 pages, Report of the SM and NLO Multileg Working Group for the
Workshop "Physics at TeV Colliders", Les Houches, France 8-26 June, 200
Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at s√=8 TeV with the ATLAS detector
The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy s√=8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb−1. No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c) of approximately 30
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