Abstract
Using a simple geometric framework with a realistic nuclear density distribution, we fit published HERMES data to determine fundamental properties of hadronization using the nuclear medium as a spatial analyzer. Our approach uses a fit to the transverse momentum broadening observable and the hadronic multiplicity ratio; the simultaneous fit to two different observables strongly constrains the outcome. Using the known sizes of the target nuclei, we extract the color lifetime, finding a zh-dependent range of values from 2 to 8 fm/c for these data. We also extract estimates for the qˆ transport coefficient characterizing the strength of the interaction between the quark and the cold nuclear medium, finding an average value of 0.035±0.011 GeV2/fm. With a three-parameter model we obtain satisfactory fits to the data with a goodness-of-fit parameter χ2/dof of 1.1 or less. In a secondary fit of the results from that model we independently find a value for the Lund String Model string tension of 1.00±0.05 GeV/fm. We evaluated the sensitivity for extracting quark energy loss and effective in-medium hadronic cross sections using four-parameter variants of the model, finding large uncertainties in both cases. Our results suggest that hadronic interaction of forming hadrons in the nuclear medium is the primary dynamical cause of meson attenuation in the HERMES data, with quark energy loss playing a more minor role.
Highlights
Data from the highest energy scattering achieved to date continue to be successfully described by perturbative Quantum Chromo Dynamics [1]
We find the dependence on zh to be compatible with the form given by the Lund string model [60] for the struck quark which is: τc MP + ν +
If we subsequently fit our results to the Lund string model form of Equation (10), leaving the string constant as a free parameter, we independently find a value that is consistent with the well-established value of 1 GeV/fm, as seen in Fig. 4; Table 1 gives the fitting results for the baseline model and two model variants
Summary
Important progress continues to be made in various nonperturbative sectors and closely related areas, such as lattice QCD [2, 3], AdS/QCD [4, 5, 6], effective field theory [7, 8], and two-particle correlations in collisions of hadronic systems [9, 10]. Breakthrough progress is expected in key areas such as understanding quark confinement in QCD [11, 12].Data from the highest energy scattering achieved to date continue to be successfully described by perturbative Quantum Chromo Dynamics (pQCD) [1].
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