Scaling patterns for QCD jets

Gerwick, Erik; Plehn, Tilman; Schumann, Steffen; Schichtel, Peter

doi:10.1007/jhep10(2012)162

Cited by 55 publications

(54 citation statements)

References 134 publications

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“…While for high multiplicities a flat exclusive jet multiplicity ratio is derived from the non-abelian nature of QCD FSR, at low multiplicity the jet multiplicity ratio is flat due to the combined effect of a Poisson-distributed multiplicity distribution and parton density suppression [3]. The emission of the first parton should be suppressed more strongly than the subsequent parton emissions.…”

Section: Jet Multiplicitiesmentioning

confidence: 99%

“…In these searches, the multiplicity and kinematics of jets in Z + jets events are exploited to achieve a separation of signal from background. This procedure often introduces scales larger than the mass of the Z boson, resulting in large logarithmic contributions in the calculation of higher-order QCD corrections to the predicted Z + jets cross section [3,4]. The measured Z + jets cross section can be compared 1 The notation Z refers to the complete Z/γ * interference.…”

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confidence: 99%

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Measurement of the production cross section of jets in association with a Z boson in pp collisions at $ \sqrt{s}=7 $ TeV with the ATLAS detector

Aad¹,

Abajyan²,

Abbott³

et al. 2013

J. High Energ. Phys.

113

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Measurements of the production of jets of particles in association with a Z boson in pp collisions at √ s = 7 TeV are presented, using data corresponding to an integrated luminosity of 4.6 fb −1 collected by the ATLAS experiment at the Large Hadron Collider. Inclusive and differential jet cross sections in Z events, with Z decaying into electron or muon pairs, are measured for jets with transverse momentum p T > 30 GeV and rapidity |y| < 4.4. The results are compared to next-to-leading-order perturbative QCD calculations, and to predictions from different Monte Carlo generators based on leading-order and next-to-leading-order matrix elements supplemented by parton showers. Conclusions 24The ATLAS collaboration 35 IntroductionThe production of jets of particles in association with a Z boson 1 at hadron colliders provides an important test of perturbative quantum chromodynamics (pQCD). Such events also constitute a non-negligible background for studies of the Higgs boson candidate [1,2] and searches for new phenomena. In these searches, the multiplicity and kinematics of jets in Z + jets events are exploited to achieve a separation of signal from background. This procedure often introduces scales larger than the mass of the Z boson, resulting in large logarithmic contributions in the calculation of higher-order QCD corrections to the predicted Z + jets cross section [3,4]. The measured Z + jets cross section can be compared 1 The notation Z refers to the complete Z/γ * interference.-1 - JHEP07(2013)032directly to fixed-order predictions at next-to-leading-order (NLO) in pQCD [5][6][7] and to Monte Carlo (MC) generators based on next-to-leading-order or leading-order (LO) matrix elements supplemented by parton showers [8][9][10]. The simulations based on LO matrix elements are affected by large uncertainties in the factorization and renormalization scales and need to be tuned and validated using data. Measurements of the Z + jets cross section have been reported for lower jet energies and lower jet multiplicities in proton-antiproton collisions at a center-of-mass energy of √ s = 1.96 TeV [11][12][13] and in proton-proton collisions based on a data set of 0.036 fb −1 collected at √ s = 7 TeV [14, 15]. This article extends these measurements, using 4.6 fb −1 of proton-proton collision data collected by the ATLAS experiment in 2011 at √ s = 7 TeV. Complementary measurements in Z + jets final states in proton-proton collisions at √ s = 7 TeV have been reported in ref. [16]. The large data set allows cross sections to be measured for the production of up to seven jets in association with a Z boson. Differential jet cross sections are accessible for large jet multiplicities and for energy regimes up to 1 TeV, which allows the modelling of the Z + jets process to be probed for typical phase-space regimes expected from new phenomena and from Higgs boson production, for example via vector-boson-fusion (VBF).Selected events contain a Z boson decaying into a pair of electrons or muons. Associated jets are identifi...

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Section: Jet Multiplicitiesmentioning

confidence: 99%

mentioning

confidence: 99%

Measurement of the production cross section of jets in association with a Z boson in pp collisions at $ \sqrt{s}=7 $ TeV with the ATLAS detector

Aad¹,

Abajyan²,

Abbott³

et al. 2013

J. High Energ. Phys.

113

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“…This behaviour has been observed by the ATLAS [79,80] and CMS [81] collaborations. For lower jet multiplicities, a different scaling is expected with r(j) = k/(j + 1) where k is a constant, referred to as "Poisson scaling" [78]. 7 For the kinematic phase space relevant for this search, a combination of the two scalings is found to describe the data in dedicated validation regions (described later in this section), as well as in simulated W/Z+jets event samples with an integrated luminosity much larger than the one of the data.…”

Section: W/z+jetsmentioning

confidence: 99%

Search for new phenomena in a lepton plus high jet multiplicity final state with the ATLAS experiment using s = 13 $$ \sqrt{s}=13 $$ TeV proton-proton collision data

Aaboud¹,

Aad²,

Abbott³

et al. 2017

J. High Energ. Phys.

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A search for new phenomena in final states characterized by high jet multiplicity, an isolated lepton (electron or muon) and either zero or at least three b-tagged jets is presented. The search uses 36.1 fb −1 of √ s = 13 TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider in 2015 and 2016. The dominant sources of background are estimated using parameterized extrapolations, based on observables at medium jet multiplicity, to predict the b-tagged jet multiplicity distribution at the higher jet multiplicities used in the search. No significant excess over the Standard Model expectation is observed and 95% confidence-level limits are extracted constraining four simplified models of R-parity-violating supersymmetry that feature either gluino or top-squark pair production. The exclusion limits reach as high as 2.1 TeV in gluino mass and 1.2 TeV in top-squark mass in the models considered. In addition, an upper limit is set on the cross-section for Standard Model tttt production of 60 fb (6.5 × the Standard Model prediction) at 95% confidence level. Finally, model-independent limits are set on the contribution from new phenomena to the signal-region yields. Conclusion 25The ATLAS collaboration 34 IntroductionThe ATLAS experiment at the Large Hadron Collider (LHC) has carried out a large number of searches for beyond the Standard Model (BSM) physics. These searches cover a broad range of different final-state particles and kinematics. However, one gap in the search coverage, as pointed out in refs. [1,2], is in final states with one or more leptons, many jets and no-or-little missing transverse momentum (the magnitude of which is denoted by -1 - JHEP09(2017)088E miss T ). Such a search is presented in this article, considering final states with an isolated lepton (electron or muon), at least eight to twelve jets (depending on the jet transverse momentum threshold), either zero or many b-tagged jets, and with no requirement on E miss T . This search has potential sensitivity to a large number of BSM physics models. In this article, model-independent limits on the possible contribution of BSM physics to several single-bin signal regions are presented. In addition, four R-parity-violating (RPV) supersymmetric (SUSY [3-8]) benchmark models are used to interpret the results. In this case, a multi-bin fit to the two-dimensional space of jet-multiplicity and b-tagged jet multiplicity is used to constrain the models. The dominant Standard Model (SM) background arises from top-quark pair production and W/Z+jets production, with at least one lepton produced in the vector boson decay. The theoretical modelling of these backgrounds at high jet multiplicity suffers from large uncertainties, so they are estimated from the data by extrapolating the b-tagged jet multiplicity distribution extracted at moderate jet multiplicities to the high jet multiplicities of the search region. Previous searches targeting similar RPV SUSY models have been carried out by the ATLAS and CMS collabo...

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“…Last ratio plot: resummation profile with full error band vs. a subset where μ H and μ S are varied in a correlated (dark purple), respectively, anti-correlated (hatched) manner, while μ Q is held fixed k ⊥ -splitting scales, particularly the one in which an event with two jets would turn into an event with one jet as the jet p ⊥ threshold passes through the scale obtained. These observables have also been proven to be accessible to analytic considerations [90], for which comparisons to full parton showers are highly desirable though are beyond the scope of this paper. In Fig.…”

Section: Jetty Processesmentioning

confidence: 99%

Parton-shower uncertainties with Herwig 7: benchmarks at leading order

et al. 2016

Self Cite

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We perform a detailed study of the sources of perturbative uncertainty in parton-shower predictions within the Herwig 7 event generator. We benchmark two rather different parton-shower algorithms, based on angular-ordered and dipole-type evolution, against each other. We deliberately choose leading order plus parton shower as the benchmark setting to identify a controllable set of uncertainties. This will enable us to reliably assess improvements by higher-order contributions in a follow-up work.

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Scaling patterns for QCD jets

Cited by 55 publications

References 134 publications

Measurement of the production cross section of jets in association with a Z boson in pp collisions at $ \sqrt{s}=7 $ TeV with the ATLAS detector

Measurement of the production cross section of jets in association with a Z boson in pp collisions at $ \sqrt{s}=7 $ TeV with the ATLAS detector

Search for new phenomena in a lepton plus high jet multiplicity final state with the ATLAS experiment using s = 13 $$ \sqrt{s}=13 $$ TeV proton-proton collision data

Parton-shower uncertainties with Herwig 7: benchmarks at leading order

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