Consequences of 2nd order QCD for jet structure in e+e− annihilation

Chandramohan, T.; Clavelli, L.

doi:10.1016/0550-3213(81)90224-8

Cited by 64 publications

(45 citation statements)

References 13 publications

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“…Unlike the global logarithms this contribution does not factor, so we assign it a common soft scale which for our numerical analysis we take to beμ S given in Eq. (35).…”

Section: Non-global Logarithmsmentioning

confidence: 99%

“…We remind the reader that there is some freedom in this refactorization, and that the corresponding uncertainty is probed by varying the parameter r in Eq. (35).…”

Section: Appendix A: Perturbative Inputsmentioning

confidence: 99%

“…The first calculations were carried out for event shapes in e + e − → jets using hemisphere jet masses. Here factorization theorems are well established and calculations exist up to N 3 LL [15,19,21,[34][35][36][37][38]. In Refs.…”

Section: Introductionmentioning

confidence: 99%

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Jet mass spectra in Higgs boson plus one jet at next-to-next-to-leading logarithmic order

et al. 2013

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The invariant mass of a jet is a benchmark variable describing the structure of jets at the LHC. We calculate the jet mass spectrum for Higgs plus one jet at the LHC at next-to-next-to-leading logarithmic (NNLL) order using a factorization formula. At this order, the cross section becomes sensitive to perturbation theory at the soft m 2 jet /p jet T scale. Our calculation is exclusive and uses the 1-jettiness global event shape to implement a veto on additional jets. The dominant dependence on the jet veto is removed by normalizing the spectrum, leaving residual dependence from non-global logarithms depending on the ratio of the jet mass and jet veto variables. For our exclusive jet cross section these non-global logarithms are parametrically smaller than in the inclusive case, allowing us to obtain a complete NNLL result. Results for the dependence of the jet mass spectrum on the kinematics, jet algorithm, and jet size R are given. Using individual partonic channels we illustrate the difference between the jet mass spectra for quark and gluon jets. We also study the effect of hadronization and underlying event on the jet mass in Pythia. To highlight the similarity of inclusive and exclusive jet mass spectra, a comparison to LHC data is presented.

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“…Unlike the global logarithms this contribution does not factor, so we assign it a common soft scale which for our numerical analysis we take to beμ S given in Eq. (35).…”

Section: Non-global Logarithmsmentioning

confidence: 99%

“…We remind the reader that there is some freedom in this refactorization, and that the corresponding uncertainty is probed by varying the parameter r in Eq. (35).…”

Section: Appendix A: Perturbative Inputsmentioning

confidence: 99%

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Jet mass spectra in Higgs boson plus one jet at next-to-next-to-leading logarithmic order

et al. 2013

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“…Given a central transverse thrust axis n T,C , one can separate the central region C into an up part C U consisting of all particles in C with p ⊥ · n T,C > 0 and a down part C D with p ⊥ · n T,C < 0 respectively. One then defines, in analogy with e + e − [66][67][68], the normalised squared invariant masses of the two regions 17) from which one can obtain a (non-global) central total and heavy-jet mass, 18) and the corresponding global event-shapes, the exponentially-suppressed total and heavy-jet mass…”

Section: Jhep06(2010)038mentioning

confidence: 99%

Phenomenology of event shapes at hadron colliders

Banfi

Salam

Zanderighi

2010

J. High Energ. Phys.

198

237

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We present results for matched distributions of a range of dijet event shapes at hadron colliders, combining next-to-leading logarithmic (NLL) accuracy in the resummation exponent, next-to-next-to leading logarithmic (NNLL) accuracy in its expansion and next-to-leading order (NLO) accuracy in a pure α s expansion. This is the first time that such a matching has been carried out for hadronic final-state observables at hadron colliders. We compare our results to Monte Carlo predictions, with and without matching to multi-parton tree-level fixed-order calculations. These studies suggest that hadron-collider event shapes have significant scope for constraining both perturbative and non-perturbative aspects of hadron-collider QCD. The differences between various calculational methods also highlight the limits of relying on simultaneous variations of renormalisation and factorisation scale in making reliable estimates of uncertainties in QCD predictions. We also discuss the sensitivity of event shapes to the topology of multi-jet events, which are expected to appear in many New Physics scenarios.

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“…The measured global event shape variables are the thrust [20], T , the scaled heavy jet mass [21], ρ, the total, B T , and wide, B W , jet broadening variables [9] and the C-parameter [22]. The first four observables are defined in terms of the particle four-momenta, while the C-parameter is derived from the spherocity tensor:…”

Section: Measurement Of Event Shape Variablesmentioning

confidence: 99%

Determination of αs from hadronic event shapes in e+e− annihilation at GeV

et al. 2002

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Results are presented from a study of the structure of high energy hadronic events recorded by the L3 detector at √ s ≥ 192 GeV. The distributions of several event shape variables are compared to resummed O(α 2 s ) QCD calculations. We determine the strong coupling constant at three average centre-of-mass energies: 194.4, 200.2 and 206.2 GeV. These measurements, combined with previous L3 measurements at lower energies, demonstrate the running of α s as expected in QCD and yield α s (m Z ) = 0.1227 ± 0.0012 ± 0.0058, where the first uncertainty is experimental and the second is theoretical.Submitted to Phys. Lett. B IntroductionThe measurement of the energy dependence of the strong coupling constant, α s , is an important test of Quantum Chromo-Dynamics (QCD). Hadronic events produced in e + e − annihilation offer a clean environment to perform such measurements. The high energy phase of the LEP collider gives a unique opportunity to measure QCD observables over a wide energy range and to perform a precise test of the energy dependence of the strong coupling constant. In addition, the study of hadronic events allows to check the validity of the QCD models used for background modelling in other studies, such as new particle searches.In its last two years, the LEP collider operated at various centre-of-mass energies, √ s, between 192 and 208 GeV. These are grouped in three samples of average centre-of-mass energies 194.4, 200.2 and 206.2 GeV, corresponding to the ranges 192 ≤ √ s < 196 GeV, 200 < √ s < 202 GeV and √ s > 202 GeV respectively.We report on measurements of five event shape distributions using 436.8 pb −1 of data collected with the L3 detector [1] at these centre-of-mass energies, as detailed in Table 1. To allow a direct comparison with our earlier QCD studies at lower energies [2-6], we follow an identical analysis procedure. The value of α s is extracted in each energy range by comparing the measured event shape distributions with predictions of second order QCD calculations [7] supplemented by resummed leading and next-to-leading order terms [8][9][10][11]. These values are used, together with previous L3 measurements at lower effective centre-of-mass energies, from 30 GeV to 189 GeV, to study the energy evolution of α s . Event SelectionThe criteria for the selection of e + e − → qq → hadrons events are identical to those used in our previous QCD study at √ s = 189 GeV [6]. They are based on the measured total visible energy, E vis , the energy imbalances parallel, E , and perpendicular, E ⊥ , to the beam direction and on the cluster multiplicity, N cl . These variables are constructed using energy clusters in the electromagnetic and hadronic calorimeters with a minimum energy of 100 MeV.The efficiency of the selection criteria and the purity of the data sample are estimated using Monte Carlo events for the process e + e − → qq(γ) generated by the KK2F [12] program, interfaced with JETSET PS [13] routines to describe the QCD parton shower evolution and hadronisation. The events are then p...

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Consequences of 2nd order QCD for jet structure in e+e− annihilation

Cited by 64 publications

References 13 publications

Jet mass spectra in Higgs boson plus one jet at next-to-next-to-leading logarithmic order

Jet mass spectra in Higgs boson plus one jet at next-to-next-to-leading logarithmic order

Phenomenology of event shapes at hadron colliders

Determination of αs from hadronic event shapes in e+e− annihilation at GeV

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