Narrow Results

The famous formula for the emission angle of Cherenkov radiation should be modified when applied to hadronic reactions because of recoil effects and the color nature of the participants. They impose an upper limit on the energy of the gluon emitted at a given angle. Also, it leads to essential corrections to the nuclear refractive index value as determined from the angular position of Cherenkov rings.

Currently the quantitative description of confinement inside nuclear matter is exclusively limited to computer experiments, mainly on lattices, and concentrating upon calculating the static potential. There is no independent reference for comparison and support of the results, especially when it comes to the quark potential in the continuum limit. Yet, we are entitled to be optimistic, for the basic results of these calculations seem to be correct from an entirely different point of view, suggested by Manton's geometrization of Skyrme theory. The present work shows the reasons of this point of view, and offers a static potential that might serve as independent reference for comparison and endorsement of any lattice calculations, and in fact of any structural hypotheses of nuclear matter. A historical review of the pertinent key moments in the history of modeling of nuclear matter, as well as an outlook anticipating the necessary future work, close the argument.

In this paper, we describe the gluon parton distribution function (PDF) in the proton, deduced by data from the ATLAS and HERA experiments, in the framework of the parton statistical model. The best fit parameters involved in the Planck formula that describes the gluon distribution are consistent with the results obtained from analysis of LHC deep inelastic proton–proton scattering processes. Remarkably, the agreement between the statistical model and the experimental gluon distributions is obtained with the same value of the “temperature” parameter $\bar{x}$ found by fitting the valence parton distributions from deep inelastic scattering. This result corroborates the validity of the statistical approach in the gluon sector.

Using new data on pion production in p+p interactions from the NA49 experiment, it is demonstrated that the detailed features of double differential pion cross sections are well reproduced over most of the phase space from the decay of a representative sample of known mesonic and baryonic resonances.

Thirteen resonances reaching up to spin four tensor-mesons and including the newly measured N* states up to the N*(1680) have been used. The p_T integrated Feynman x_F distributions in the high-x_F region 0.4 < x_F < 0.9 are quantitatively reproduced as well as the p_T distributions up to 2 GeV/c and beyond at all x_F.

In both these phase space regions direct effects of parton dynamics such as valence quark fragmentation or parton scattering are generally evoked in order to provide a basis of understanding. The saturation of the measured yields by resonance decay casts a doubt on these assumptions.

A short comment on modern experimental status of extraction of the nucleon transversity distribution and Collins fragmentation function based on the work¹ is given.

The following sections are included:

• INTRODUCTION

• EXPERIMENTAL DETERMINATIONS OF α_s(Q)²

• THE QCD THEORY OF HARD PROCESSES

• CONCLUSIONS

• ACKNOWLEDGMENTS

• Literature Cited

• NOTES ADDED