Abstract
The number of charged particles inside jets is a widely used discriminant for identifying the quark or gluon nature of the initiating parton and is sensitive to both the perturbative and non-perturbative components of fragmentation. This paper presents a measurement of the average number of charged particles with p_text {T}>500 {mathrm{MeV}} inside high-momentum jets in dijet events using 20.3 fb^{-1} of data recorded with the ATLAS detector in pp collisions at sqrt{s}=8 {mathrm{TeV}} collisions at the LHC. The jets considered have transverse momenta from 50 {mathrm{GeV}} up to and beyond 1.5 {mathrm{TeV}}. The reconstructed charged-particle track multiplicity distribution is unfolded to remove distortions from detector effects and the resulting charged-particle multiplicity is compared to several models. Furthermore, quark and gluon jet fractions are used to extract the average charged-particle multiplicity for quark and gluon jets separately.
Highlights
This paper presents a measurement of the average chargedparticle multiplicity verse momentum in inside jets as a dijet events in fpupncctoilolnisioofntsheatje√t stra=ns8-TeV with the ATLAS detector
The effects of pileup are modelled by adding to the generated hard-scatter events multiple minimum-bias events generated with Pythia 8.160, the A2 tune [44], and the MSTW2008LO [49] Parton distribution function (PDF) set
One important difference between A14 and Monash is that the value of αs governing the amount of final-state radiation is about 10 % lower in A14 than in Monash. This parameter has a large impact on the average charged-particle multiplicity, which is shown by the Pythia 6 lines in Fig. 4 where the Perugia radHi and radLo tunes are significantly separated from the central P2012 tune
Summary
This paper presents a measurement of the average chargedparticle multiplicity verse momentum in inside jets as a dijet events in fpupncctoilolnisioofntsheatje√t stra=ns8-. One ATLAS result [31] used jets that are reconstructed using tracks and have transverse momentum less than 40. A second ATLAS analysis [32] has measured charged particles inside jets with transverse momenta spanning the range from 50 to 500 GeVwith approximately constant 3–4 %. The CMS measurement [33] spans jet transverse momenta between 50 and 800 GeVwith 5–10 % uncertainties in the bins of highest transve√rse analysis presented here uses the full s momentum. 3. In order for the measured charged-particle multiplicity to be compared with particle-level models, the data are unfolded to remove distortions from detector effects, as described in Sect. 4. Systematic uncertainties in the measured charged-particle multiplicity are discussed in Sect.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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.
