String fragmentation with a time-dependent tension

Abstract

Motivated by recent theoretical arguments that expanding strings can be regarded as having a temperature that is inversely proportional to the proper time, $$\tau $$ τ , we investigate the consequences of adding a term $$\propto 1/\tau $$ ∝ 1 / τ to the string tension in the Lund string-hadronization model. The lattice value for the tension, $$\kappa _0 \sim 0.18\,{\mathrm {GeV}}^2\sim 0.9\,{\mathrm {GeV}}/{\mathrm {fm}}$$ κ 0 ∼ 0.18 GeV 2 ∼ 0.9 GeV / fm , is then interpreted as the late-time/equilibrium limit. A generic prediction of this type of model is that early string breaks should be associated with higher strangeness (and baryon) fractions and higher fragmentation $$\langle p_\perp \rangle $$ ⟨ p ⊥ ⟩ values. It should be possible to use archival ee data sets to provide model-independent constraints on this type of scenario, and we propose a few simple key measurements to do so.

String Interactions as a Source of Collective Behaviour

“…However, developments are also occurring in other areas, both connected and unrelated to these endeavours. For the string hadronization model, this includes attempts to modify the usual Eqution (4) to a thermal one [88], colour reconnection corrections to the top quark mass [89], calculations of spatial vertices in the fragmentation [90] underlying hadronic rescattering, hyperfine splitting effects [91], and more theoretical attempts to investigate the single string entanglement entropy [92], with some phenomenological considerations also made [93]. Similarly, for the HERWIG cluster model, efforts such as cluster reconnections [94,95] have made progress in the production of multi-strange baryons, akin to string interactions.…”

Cluster Hadronisation in Sherpa

“…More recently, a thermodynamic approach to string fragmentation has been studied in [11], modifying, among others, production rates of heavy hadrons. Time-dependent string tension was shown to increase the rates and modify the kinematics of strange and baryon production [12], and similarly, hyper-fine splittings in hadron formation in the string model have been analysed in [13], which also affect the production yields of hadron species, in particular strange hadrons.…”