In the framework of the model with quark-gluon strings considered as color flux tubes we study the correlations between various observables in two acceptance windows separated in rapidity and azimuth, used in the analysis of the multiparticle production in hadronic interactions at high energy. To take into account the string fusion effects leading to a formation of string clusters with new properties we introduce in the model the finite lattice (grid) in the transverse (impact parameter) plane.
In the framework of this approach, for a realistic case with an inhomogeneous distribution of strings in the transverse plane, we find explicit analytical formulas for the asymptotes of the coefficients of the long-range rapidity correlations between various quantities, including intense (the mean transverse momentum) at large string density.
We study also a strongly intense variable between the multiplicities of particles produced in two observation windows separated in rapidity and azimuth. We show that in the case of independent identical strings, this observable is indeed a strongly intense quantity. It depends only on the string characteristics and does not depend on the trivial, so-called "volume" fluctuations in the number of strings, arising, in particular, from inevitable impact parameter fluctuations. When taking into account the formation of string clusters with new properties, this variable becomes equal to the weighted average of its values for different clusters. The weights depend on the conditions of the collision, and the variable loses its strongly intensive property.
We analyze the properties of the obtained correlation coefficients and the strongly intensive variable under study, and also the possibilities of its experimental observation.
We also show that long-range azimuthal-rapidity correlations (the ridge) can arise from the superposition of many events with exchange of cluster of different number of strings and not from two-particle correlations in a single event. In this case it appears in the resulting two-particle correlation function due to the event-by-event fluctuation of the azimuthal distribution. The physical reason, which leads to the event anisotropy of the azimuthal distribution in this approach, is the final state interaction of produced particles with the fused string medium.
The presentation is based on the papers [1-5].
The research was supported by the Russian Foundation for Basic Research grant (No. 18-02-40075) and the St. Petersburg State University grant (Id: 43319394).
- S.N. Belokurova, V.V. Vechernin, Strongly intensive variables and long-range correlations in the model with a lattice in the transverse plane,
Theor. Math. Phys. 200 (2019) 1094–1109 [to be appear in the August issue]
- E. Andronov, V. Vechernin, Strongly intensive observable between multiplicities in two acceptance windows in a string model,
Eur. Phys. J. A 55 (2019) 14_1-12.
- V. Vechernin, Short- and long-range rapidity correlations in the model with a lattice in transverse plane,
EPJ Web Conf. 191 (2018) 04011_1-8.
- M.A. Braun, C. Pajares and V.V. Vechernin, Ridge from strings,
Eur. Phys. J. A 51 (2015) 44_1-11.
- V.V. Vechernin, Forward-backward correlations between multiplicities in windows separated in azimuth and rapidity,
Nucl. Phys. A 939 (2015) 21-45.