Abstract
Measurements of jet substructure describing the composition of quark- and gluon-initiated jets are presented. Proton-proton (pp) collision data at sqrt{s} = 13 TeV collected with the CMS detector are used, corresponding to an integrated luminosity of 35.9 fb−1. Generalized angularities are measured that characterize the jet substructure and distinguish quark- and gluon-initiated jets. These observables are sensitive to the distributions of transverse momenta and angular distances within a jet. The analysis is performed using a data sample of dijet events enriched in gluon-initiated jets, and, for the first time, a Z+jet event sample enriched in quark-initiated jets. The observables are measured in bins of jet transverse momentum, and as a function of the jet radius parameter. Each measurement is repeated applying a “soft drop” grooming procedure that removes soft and large angle radiation from the jet. Using these measurements, the ability of various models to describe jet substructure is assessed, showing a clear need for improvements in Monte Carlo generators.
Highlights
(CF = 4/3) and gluons (CA = 3) leads to a higher probability for gluons to radiate a soft gluon by a factor of CA/CF = 9/4 [6]
Where zi is the fractional transverse momentum carried by the ith jet constituent, R is the jet radius parameter, and ∆Ri is the displacement of the constituent from the jet axis, defined as ∆Ri = (∆yi)2 + (∆φi)2 where ∆yi and ∆φi are the separations in rapidity and azimuthal angle, respectively, between the jet axis and the ith constituent
Each quantity is measured as a function of jet transverse momentum pT, with different jet radius parameters, including all particles and only charged particles, and with and without applying a soft drop grooming procedure [56] that removes soft and wide angle radiation from the jet, thereby making the jet substructure observables more resilient to effects from pileup, underlying event, and initial state radiation
Summary
The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. Matching muons to tracks measured in the silicon tracker results in a relative transverse momentum resolution, for muons with pT up to 100 GeV, of 1% in the barrel and 3% in the endcaps. The energy of electrons is determined from a combination of the electron momentum at the primary interaction vertex as determined by the tracker, the energy of the corresponding ECAL cluster, and the energy sum of all bremsstrahlung photons spatially compatible with originating from the electron track. The energy of charged hadrons is determined from a combination of their momentum measured in the tracker and the matching ECAL and HCAL energy deposits, corrected for the response function of the calorimeters to hadronic showers. The probability to originate from the primary interaction vertex is deduced by comparing the momentum distribution variable to its event median characterizing the expected value for particles from pileup vertices. The second level, known as the high-level trigger, consists of a farm of processors running a version of the full event reconstruction software optimized for fast processing, and reduces the event rate to around 1 kHz before data storage
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
