The top quark, the heaviest quark and, indeed, the heaviest elementary particle known today, constitutes a novel probe of the long-lived medium in quark-gluon phase which, as expected, can be ...produced even in light nuclei collisions at ultra-high energies. Some distinctive features are considered for particle production in the top sector in ultra-high energy domain. The antitop-top pair production is studied within the quantum chromodynamics and effective field theory approach used for calculations of total partonic cross sections. Predictions for all observables are computed at NNLO in quantum chromodynamics and at LO in effective field theory. These quantitative results can be important for both the future collider experiments at center-of-mass energy frontier and the improvement of the phenomenological models for development of the cosmic ray cascades in ultra-high energy domain. Thus the study allows the better understanding of heavy particle production and emphasizes the exciting interrelation between the high-energy physics on accelerators and ultra-high energy cosmic ray measurements.
Collisions of cosmic ray particles with ultrahigh initial energies with nuclei in the atmosphere open a wide room for appearing of the novel dynamical features for multiparticle production processes. ...In particular, the laser-like behavior of pions driven by Bose–Einstein condensation would result in the shift to larger multiplicities and, as a consequence, could provide, in general, the enhanced yield of cosmic muons. In the present work the critical value of the space charged particle density for onset of Bose–Einstein condensation of the boson (pion) wave packets into the same wave-packet state is estimated within the model with complete multiparticle symmetrization for the energy domain corresponding to the ultrahigh energy cosmic rays (UHECR). Energy dependence of mean density of charged pions is evaluated for the cases of absence of the Bose–Einstein effects and for presence of laser-like behavior of pions. The possible influence of the Bose–Einstein condensation is discussed for the muon production in UHECR particle collisions with the atmosphere.
The processes with single top quark production provide a prototype search for the types of final state that are expected in many new physics scenarios. Some distinctive features are considered for ...particle production in the top sector in ultra-high energy domain which can be covered partly in the collisions of cosmic ray particles with atmosphere. The single top quark production through electroweak interaction is studied within the Standard Model and the Effective Field Theory approach used for calculations of total partonic cross sections in
–channel. These quantitative results can be important for both the future collider experiments at center-of-mass energy frontier and the improvement of the phenomenological models for development of the cosmic ray cascades in ultra-high energy domain. Thus the study allows the better understanding of heavy particle production and emphasizes the exciting interrelation between the high-energy physics on accelerators and ultra-high energy cosmic ray measurements.
Estimations of some geometrical and bulk parameters are presented for the matter produced in various type collisions with ultra-high energy cosmic ray (UHECR) particles. Results for multiplicity ...density at midrapidity, decoupling time, and energy density are discussed for small and larger collision systems. Based on the analytic functions suggested previously elsewhere, estimations for a wide set of space—time quantities are obtained for emission region created in various particle collisions at energies of UHECR. The space particle densities at freeze-out are derived also and allow the possibility of novel features for secondary particle production like Bose—Einstein condensation at least for nuclear interactions with UHECR particles. The estimations obtained for global and geometrical parameters indicate the creation of deconfined quark—gluon matter with large enough volume and lifetime even in light nuclear collisions at UHECR energies. These quantitative results can be important for both the future collider experiments at center-of-mass energy frontier and the improvement of the phenomenological models for development of the cosmic ray cascades in ultra-high energy domain.
The results obtained from a phenomenological analysis of the ratio of the elastic-to-total cross sections for proton-proton (
pp
) and antiproton-proton (
(
p
¯
p
)
) scattering as a function of ...energy are presented. Analytic functions proposed on the basis of studying low- and high-energy experimental data for various scattering parameters make it possible to obtain a statistically acceptable quantitative description of the energy dependence of this ratio over a broad energy region of
s
≥
3
GeV for individual samples of
pp
and
p
¯
p
collisions and over the region of
s
≥
5
GeV for a combined ensemble of experimental data. On the basis of the resulting approximations, the ratio of the elastic-to-total cross sections
for pp
collisions are estimated at various values of
s
up to an ultrahigh energy of
s
=
10
PeV. The resulting estimates may prove to be useful for experiments at currently operating and future hadron colliders, as well as for measurements of ultrahigh-energy cosmic rays. An indication of the onset of the asymptotic region for the cross-section ratio in question is observed in the region of
s
≳
5
−
10
PeV.
Results obtained by studying the energy dependence of the total cross section for nucleon–nucleon interaction are presented. The analytic parametrization proposed within axiomatic quantum field ...theory describes quantitatively a unified set of experimental data on proton–proton and antiproton–proton scattering. At collision energies above 86 GeV, the parameter values fitted to subsets of all available data and accelerator data alone were found to deviate from the respective asymptotic values. This indicates that the Froissart–Martin limit for the total cross section has not yet been reached in the case of these subsets. An approximation of the total nucleon–nucleon cross section measured in cosmic rays leads for some parameters to fitted values that, within 1.0 to 1.3 standard deviations, agree with the respective asymptotic values. This resultmay be viewed as an indication of the beginning of the asymptotic functional behavior of the total nucleon–nucleon cross section measured in cosmic rays of ultrahigh energy
O
(100 TeV). This is confirmed within the color glass condensate approach.
A survey of experimental results obtained by studying chiral effects in nucleus–nucleus collisions at various energies is presented. The entire body of these experimental results confirms indirectly ...a topologically nontrivial structure of the QCD vacuum and the possibility of a local violation of discrete QCD symmetries at finite temperature. A significant decrease in the asymmetry of the distribution of electrically charged particles with respect to the reaction plane in heavy-ion collisions in the energy range of
s
N
N
GeVmay be indicative of a possible transition to the region where hadron states dominate over quark–gluon degrees of freedom in a mixed phase formed in nucleus–nucleus collisions at intermediate energies.
This paper presents a qualitative explanation for the hollowness effect based on the inelastic overlap function, claiming this result is a consequence of fundamental thermodynamic processes. Using ...the Tsallis entropy, one identifies the entropic index w with the ratio of the collision energy to critical one in the total cross-section. The integrated probability density function is replaced by the inelastic overlap function, which represents the probability of occurrence of an inelastic event depending on both the collision energy and impact parameter. The Coulomb potential, as well as the confinement potential, are used as naive approaches to describe the (internal) energy of the colliding hadrons. The Coulomb potential in the impact parameter picture is not able to furnish any reliable physical result near the forward direction. However, the confinement potential in the impact parameter space results in the hollowness effect shown by the inelastic overlap function near the forward direction.
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