Measurement of jet-substructure observables in top quark, W boson and light jet production in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV with the ATLAS detector

Abstract

A measurement of jet substructure observables is presented using data collected in 2016 by the ATLAS experiment at the LHC with proton-proton collisions at √ s = 13 TeV. Large-radius jets groomed with the trimming and soft-drop algorithms are studied. Dedicated event selections are used to study jets produced by light quarks or gluons, and hadronically decaying top quarks and W bosons. The observables measured are sensitive to substructure, and therefore are typically used for tagging large-radius jets from boosted massive particles. These include the energy correlation functions and the N-subjettiness variables. The number of subjets and the Les Houches angularity are also considered. The distributions of the substructure variables, corrected for detector effects, are compared to the predictions of various Monte Carlo event generators. They are also compared between the large-radius jets originating from light quarks or gluons, and hadronically decaying top quarks and W bosons.The ATLAS experiment uses a multipurpose particle detector [25, 26] with a forward-backward symmetric cylindrical geometry and a near 4π coverage in solid angle.1 It consists of an inner tracking detector (ID) surrounded by a thin superconducting solenoid providing a 2 T axial magnetic field, electromagnetic (EM) and hadron calorimeters, and a muon spectrometer. The ID consists of silicon pixel, silicon microstrip, and straw-tube transition-radiation tracking detectors, covering the pseudorapidity range |η| < 2.5. The calorimeter system covers the pseudorapidity range |η| < 4.9. Electromagnetic calorimetry is performed with barrel and endcap high-granularity lead/liquid-argon (LAr) sampling calorimeters, within the region |η| < 3.2. There is an additional thin LAr presampler covering |η| < 1.8, to correct for energy loss in material upstream of the calorimeters. For |η| < 2.5, the LAr calorimeters are divided into three layers in depth. Hadronic calorimetry is performed with a steel/scintillator-tile calorimeter, segmented into three barrel structures within |η| < 1.7, and two copper/LAr hadronic endcap calorimeters, which cover the region 1.5 < |η| < 3.2. The forward solid angle up to |η| = 4.9 is covered by copper/LAr and tungsten/LAr calorimeter modules, which are optimised for energy measurements of electrons/photons and hadrons, respectively. The muon spectrometer consists of separate trigger and high-precision tracking chambers that measure the deflection of muons in a magnetic field generated by superconducting air-core toroids.The ATLAS detector selects events using a tiered trigger system [27]. The first level is implemented in custom electronics. The second level is implemented in software running on a general-purpose processor farm which processes the events and reduces the rate of recorded events to 1 kHz. Monte Carlo samplesSimulated events are used to optimise the event selection, correct the data for detector effects and estimate systematic uncertainties. The predictions of different phenomenological models implemented in t...

The soft drop groomed jet radius at NLL

“…In this work, we focus on the soft drop grooming algorithm of [4]. Both on the experimental [5][6][7][8] and the theoretical side [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], significant progress has been made recently in improving our understanding of soft drop groomed jet observables. In the heavy-ion community, soft drop groomed jet substructure observables have also received increasing attention from both experiment [25][26][27][28] and theory [29][30][31][32][33][34][35][36][37][38][39].…”

The leading jet transverse momentum in inclusive jet production and with a loose jet veto

“…As such, the contribution from the α 2 s ln 2 R terms, as a fraction of the NLO predictions, grows at larger p T,J for these smaller values of R. While this is potentially an interesting indication of where ln 2 R terms could become large enough to warrant resummation, it is also well known that the NNLO QCD corrections to Higgs plus jet production cross sections lead to large K-factors [40,41]. We would therefore also expect large corrections from the dσ (2) term in the factorization formula, as well as potentially large contributions from dσ (1) ⊗ J (1) . The plot on the right of figure 6 instead displays the inclusive cross section, where we also assess the impact of the α 2 s L 2 terms.…”

“…Collinear final-state radiation is already encoded by the jet functions and is not part of dσ pp→Hij , since it would otherwise be double counted. 2 Furthermore, dσ pp→Hij also includes the one-loop virtual corrections to pp → Hi, for which p T,j = 0 and the integral over J l,j gives unity from the conservation of probability (see eq. (2.8)).…”

Fast simulation of detector effects in Rivet

“…Figure 7: The effect of tuned jet constituent smearing without a calorimeter granularity emulation, on reconstruction-level data in Ref. [40]. The LHA, D 2 , and ECF 2 norm observables are shown respectively in the rows from top to bottom, with the observed data compared to truth & smeared predictions in the left column, and the bin-by-bin transfer functions used for tuning in the right column.…”