Diffractive and non-diffractive wounded nucleons and final states in pA collisions

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166

183

We present a new model for building up complete exclusive hadronic final states in high energy nucleus collisions. It is a direct extrapolation of high energy pp collisions (as described by PYTHIA), and thus bridges a large part of the existing gap between heavy ion and high energy physics phenomenology. The model is inspired by the old Fritiof model and the notion of wounded nucleons. Two essential features are the treatment of multi-parton interactions and diffractive excitation in each N N sub-collision. Diffractive excitation is related to fluctuations in the nucleon partonic sub-structure, and fluctuations in both projectile and target are here included for the first time. The model is able to give a good description of general final-state properties such as multiplicity and transverse momentum distributions, both in pA and AA collisions. The model can therefore serve as a baseline for understanding the non-collective background to observables sensitive to collective behaviour. As PYTHIA does not include a mechanism to reproduce the collective effects seen in pp collisions, such effects are also not reproduced by the present version of Angantyr. Effects of high string density, shown to be able to reproduce e.g. higher strangeness ratios and the ridge in pp, will be added in future studies.

Section: Introductionmentioning

confidence: 99%

The Angantyr model for heavy-ion collisions in Pythia8

Bierlich

Gustafson

Lönnblad

et al. 2018

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166

183

“…This cross section was dubbed the "wounded cross section" in ref. [35], and can be constructed by generalizing the inelastic cross section, using eq. (7.4).…”

Section: Results III -Dynamic Colour Fluctuations In Glauber Calculatmentioning

confidence: 99%

“…In ref. [35] is was found that a log-normal distribution (see eq. (B.2) in appendix B) describes fluctuations generated by a dipole approach better.…”

Section: Results III -Dynamic Colour Fluctuations In Glauber Calculatmentioning

confidence: 99%

“…The notion of "participating" is, however, a model dependent statement. We use the definition from Angantyr [35,36], which defines participating nucleons as either "inelastically" or "absorptively" (inelastic non-diffractively) wounded, see appendix B for a brief review. For pp collisions, and for fluctuations in nuclear collisions, we follow Avsar et al [25], and define a participant parton eccentricity (though somewhat modified from the cited exploratory work).…”

Section: Eccentricity Scaling Of Flow Observablesmentioning

confidence: 99%

“…cross sections) in cases where little guidance from data exists. In this paper (see section 7) we will also apply the formalism to extract Glauber-Gribov (GG) colour fluctuations in γ * p collisions, in order to take the initial steps towards a generation of electron-ion (eA) collisions within the Angantyr framework [35,36] -a possibility which is foreseen to aid the preparation of an eA program currently being planned [37].…”

mentioning

confidence: 99%

See 2 more Smart Citations

Dipole evolution: perspectives for collectivity and γ*A collisions

Bierlich

Rasmussen

2019

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The transverse, spatial structure of protons is an area revealing fundamental properties of matter, and provides key input for deeper understanding of emerging collective phenomena in high energy collisions of protons, as well as collisions of heavy ions. In this paper eccentricities and eccentricity fluctuations are predicted using the dipole formulation of BFKL evolution. Furthermore, first steps are taken towards generation of fully exclusive final states of γ * A collisions, by assessing the importance of colour fluctuations in the initial state. Such steps are crucial for the preparation of event generators for a future electron-ion collider. Due to the connection between an impact parameter picture of the proton structure, and cross sections of ep and pp collisions, the model parameters can be fully determined by fits to such quantities, leaving results as real predictions of the model.

A multi-channel U-Matrix model of hadron interaction at high energy

Oueslati

2023

The present phenomenological study investigates a multi-channel model of high-energy hadron interactions by considering a full parton configurations space and the U-matrix unitarisation scheme of the elastic amplitude, comparing it to the two-channel model, and examining the consequences of up-to-date high-energy collider data on the best fits to various hadronic observables in pp and $$ p\overline{p} $$ p p ¯ collisions. The findings of this study reveal that the data are well-fitted with the multi-channel model and that the difference compared to the two-channel one is negligible. Of particular significance is the observation that the U-matrix unitarisation is likely incompatible with uncorrelated pomeron exchange, as suggested by the equivalence between the U-matrix multi-channel and eikonal two-channel descriptions. Based on our best fit, predictions for the ρ parameter, the double diffractive cross-section, and the elastic differential cross-section are provided. We shed light on the effect of taking into account a multi-channel model on present and future cosmic ray data.