Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userComparing Gluon to Quark Jets with DELPHI
47
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
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.
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.
The energy evolution of average multiplicities of quark and gluon jets is studied in perturbative QCD. Higher order (3NLO) terms in the perturbative expansion of equations for the generating functions are found. First and second derivatives of average multiplicities are calculated. The mean multiplicity of gluon jets is larger than that of quark jets and evolves more rapidly with energy. It is shown which quantities are most sensitive to higher order perturbative and nonperturbative corrections. We define the energy regions where the corrections to different quantities are important. The latest experimental data are discussed.
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).
Jets are a promising way to probe the non-equilibrium physics of quark-gluon plasma (QGP). We study how an out-of-equilibrium medium induces a jet particle to emit gluons. Evaluation of the emission rate is complicated by Weibel instabilities which lead to an exponential growth of chromomagnetic fields. Deriving a quantum field theoretical description of an unstable QGP medium, we show that the chromomagnetic fields deflect jet particles during the gluon emission.
We investigate the effect of a small, gauge-invariant mass of the gluon on the anomalous chromomagnetic moment of quarks (ACM) by perturbative calculations at one loop level. The mass of the gluon is taken to have been generated via a topological mass generation mechanism, in which the gluon acquires a mass through its interaction with an antisymmetric tensor field $B_{mu u}$. For a small gluon mass $(<10$ MeV), we calculate the ACM at momentum transfer $q^2=-M_Z^2$. We compare those with the ACM calculated for the gluon mass arising from a Proca mass term. We find that the ACM of up, down, strange and charm quarks vary significantly with the gluon mass, while the ACM of top and bottom quarks show negligible gluon mass dependence. The mechanism of gluon mass generation is most important for the strange quarks ACM, but not so much for the other quarks. We also show the results at $q^2=-m_t^2$. We find that the dependence on gluon mass at $q^2=-m_t^2$ is much less than at $q^2=-M_Z^2$ for all quarks.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
