Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSubjet Multiplicity in Quark and Gluon Jets at Dzero
50
0
0.0
(
0
)
Authors
The Dzero Collaboration
Ask ChatGPT about the research
No Arabic abstract
We measure the subjet multiplicity M in jets reconstructed with a successive combination type of jet algorithm (kT). We select jets with 55<pT<100 GeV and |eta|<0.5. We compare similar samples of jets at sqrt(s)=1800 and 630 GeV. The HERWIG Monte Carlo simulation predicts that 59% of the jets are gluon jets at sqrt(s)=1800 GeV, and 33% at sqrt(s)=630 GeV. Using this information, we extract the subjet multiplicity in quark (Mq) and gluon (Mg) jets. We also measure the ratio R= (<Mg> -1)/(<Mq>-1)= 1.84 +- 0.15(stat) +0.22-0.18(sys).
rate research
Read More
Recent developments and results on the comparison of gluon to quark jets are discussed. A most important topic is the introduction of explicit energy scales of the jets. The scaling violation of the fragmentation function and the increase of the multiplicity with scale is shown to be directly proportional to the corresponding gluon or quark colour factor. The ratio of the hadron multiplicity in gluon to quark jets is understood to be smaller than the colour factor ratio due to differences in the fragmentation of the leading quark or gluon. Novel algorithms to reconstruct the colour portraits or the colour flow of an event are presented.
We show that in studies of light quark- and gluon-initiated jet discrimination, it is important to include the information on softer reconstructed jets (associated jets) around a primary hard jet. This is particularly relevant while adopting a small radius parameter for reconstructing hadronic jets. The probability of having an associated jet as a function of the primary jet transverse momentum ($p_T$) and radius, the minimum associated jet $p_T$ and the association radius is computed upto next-to-double logarithmic accuracy (NDLA), and the predictions are compared with results from Herwig++, Pythia6 and Pythia8 Monte Carlos (MC). We demonstrate the improvement in quark-gluon discrimination on using the associated jet rate variable with the help of a multivariate analysis. The associated jet rates are found to be only mildly sensitive to the choice of parton shower and hadronization algorithms, as well as to the effects of initial state radiation and underlying event. In addition, the number of $k_T$ subjets of an anti-$k_T$ jet is found to be an observable that leads to a rather uniform prediction across different MCs, broadly being in agreement with predictions in NDLA, as compared to the often used number of charged tracks observable.
We present details of a search for electroweak production of single top quarks in the electron+jets and muon+jets decay channels. The measurements use ~90 pb^-1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DZero detector. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process ppbar->tb+X of 39 pb. The upper limit for the t-channel process ppbar->tqb+X is 58 pb.
We report a measurement of the fraction of top quark pair events produced via gluon-gluon fusion in $pbar{p}$ collisions at $sqrt{s} = 1.96 ~rm TeV$ in lepton+jets final states using the full RunII data set corresponding to $9.7 ~rm fb^{-1}$ of integrated luminosity collected by the DO experiment. We utilize a boosted decision tree to distinguish top quark pair events produced by $qbar{q}$ annihilation and $gg$ fusion. We perform a template fit to extract the $tbar{t}$ production fraction via $gg$ fusion and find $f_{gg} = 0.096 pm 0.039 ~(rm stat.) ~^{+0.077}_{-0.062} ~(rm syst.)$.
This is a summary of the latest results of the DELPHI Collaboration on the properties of identified quark and gluon jets. It covers the measurement of the fragmentation functions of gluons and quarks and their scaling violation behaviour as well as an analysis of the scale dependence of the multiplicities in gluon and quark jets. Further, a precision measurement of CA/CF from the multiplicities in symmetric three jet events is discussed.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
