More axions from strings

We study the contribution to the QCD axion dark matter abundance that is produced by string defects during the so-called scaling regime. Clear evidence of scaling violations is found, the most conservative extrapolation of which strongly suggests a large number of axions from strings. In this regime, nonlinearities at around the QCD scale are shown to play an important role in determining the final abundance. The overall result is a lower bound on the QCD axion mass in the post-inflationary scenario that is substantially stronger than the naive one from misalignment.

Extracting αs from scaling violations in light-hadron fragmentation functions

We review the status of extracting the strong-coupling constant [Formula: see text] from the scaling violations in fragmentation functions (FFs) by fitting the latter to experimental data of the inclusive production of single light hadrons in [Formula: see text] annihilation. We also discuss the analogous analysis based on the average hadron multiplicities in gluon and quark jets, which correspond to the first Mellin moments of the respective FFs. We then assess the prospects of such [Formula: see text] determinations at future high-luminosity [Formula: see text] colliders such as the CERN Future Circular Collider operated in the [Formula: see text] annihilation mode (FCC-ee).

Charged Particles Multiplicity and Scaling Violation of Fragmentation Functions in Electron-Positron Annihilation

By the use of data from the annihilation process of electron-positron in AMY detector at 60 GeV center of mass energy, charged particles multiplicity distribution is obtained and fitted with the KNO scaling. Then, momentum spectra of charged particles and momentum distribution with respect to the jet axis are obtained, and the results are compared to the different models of QCD; also, the distribution of fragmentation functions and scaling violations are studied. It is being expected that the scaling violations of the fragmentation functions of gluon jets are stronger than the quark ones. One of the reasons for such case is that splitting function of quarks is larger than splitting function of gluon.