Event patterns (particle scatter plots) extracted from charged particle spectra inppand Pb–Pb collisions at 2.76 TeV

Abstract

Event patterns extracted from anisotropic spectra of charged particles produced in lead-lead collisions at 2.76 TeV are investigated. We use an inverse power-law resulted from the QCD calculus to describe the transverse momentum spectrum in the hard scattering process, and a revised Erlang distribution resulted from a multisource thermal model to describe the transverse momentum spectrum and anisotropic flow in the soft excita-tion process. The pseudorapidity distribution is described by a three-Gaussian function which is a revision of the Landau hydrodynamic model. Thus, the event patterns at the kinetic freeze-out are displayed by the scatter plots of the considered particles in the three-dimensional velocity, momentum, and rapidity spaces.

Event patterns extracted from top quark-related spectra in proton-proton collisions at 8 TeV

“…In any case, conservation of energy and momentum is satisfied in the calculation. For comparisons with our recent works [23][24][25], as an example, we can see the similarities and differences in the three-dimensional β x -β y -β z space. The scatter plots of t t systems and (hadronic) top quarks are similar to those of Z bosons and quarkonium states [25] due to them being heavy particles.…”

“…In our opinion, the present work supports the methodology which restructures the event patterns or particle scatter plots from both p T and y spectra. This method can be used in the studies of other particles [23][24][25]31] as discussed above, which allows us to give comparisons of the production of different types of particles. Indeed, from the three-dimensional distribution, we have obviously observed some differences for different type of particles.…”

Event patterns extracted from anisotropic spectra of charged particles produced in Pb-Pb collisions at 2.76 TeV

“…It is expected that the event patterns displayed by the scatter plots of different particles produced in different centralities at different energies have some similarities or differences. In particular, the event patterns displayed by the scatter plots of charged particles in the three-dimensional velocity space are rough sphericity (or fat ellipsoid along Oz axis) with high density close to β z = 1 [22]. This rough sphericity does not depend obviously on the centrality at dozens of GeV and above.…”

“…It should be noted that the elliptic flow v 2 is not zero in most cases such as in non-central collisions, which renders anisotropic flow in the xOy plane in the rest source frame. That is, the assumption of isotropic emission in the xOy plane used in our previous works [20][21][22][23] is only an approximate treatment and should be revised due to non-zero anisotropic flow. To include anisotropic flow in the event patterns, we have to use simultaneously p T , v 2 , and Y (or η) spectra for extracting parameters and structuring event patterns.…”

“…In our previous works [20][21][22][23], the event patterns extracted from the transverse momentum and rapidity (or pseudorapidity) spectra were studied, and an isotropic assumption in the transverse plane was used. In this paper, a non-zero elliptic flow is considered in the model treatment.…”