Hadron Attenuation Research Articles

Quenching of high p⊥ hadrons by (pre-)hadronic FSI at RHIC

Recently we have conjectured that (in-)elastic collisions of (pre-)hadronic high momentum states with the bulk of hadrons in the late fireball might substantially account for the attenuation of the high transverse momentum hadrons at RHIC. The potential hadronic attenuation has therefore to be addressed in further detail before definite conclusions on possible QCD effects in a deconfined QGP phase can be drawn with respect to the materializing jets. From our transport studies we find that the interactions of fully formed hadrons are practically negligible in central Au+Au collisions at for p⊥ ⩾ 6 GeV/c, but have some importance for the shape of the ratio RAA at lower p⊥ (⩽6 GeV/c). However, a significant part of the large suppression seen experimentally is attributed to inelastic interactions of ‘leading’ jet-like pre-hadrons with the dense hadronic environment. In addition, we also show within this scenario first (preliminary) results of near-side and far-side correlations of high p⊥ particles from central Au+Au collisions at . It turns out that the near-side correlations are unaltered in accordance with experiment, whereas the far-side correlations are suppressed by ∼60%. Since the experimental observation is a nearly complete disappearance of the far-side jet there should be some additional and earlier partonic interactions in the dense and possibly coloured medium.

Dynamics of strange, charm and high momentum hadrons in relativistic nucleus–nucleus collisions

We investigate hadron production and attenuation of hadrons with strange and charm quarks (or antiquarks) as well as high transverse momentum hadrons in relativistic nucleus–nucleus collisions from 2 A GeV to 21.3 A TeV within two independent transport approaches (UrQMD and HSD). Both transport models are based on quark, diquark, string and hadronic degrees of freedom, but do not include any explicit phase transition to a quark–gluon plasma. From our dynamical calculations we find that both models do not describe the maximum in the K +/ π + ratio at 20–30 A GeV in central Au+Au collisions found experimentally, though the excitation functions of strange mesons are reproduced well in HSD and UrQMD. Furthermore, the transport calculations show that the charmonium recreation by D+ D ̄ →J/Ψ+ meson reactions is comparable to the dissociation by ‘comoving’ mesons at RHIC energies contrary to SPS energies. This leads to the final result that the total J/ Ψ suppression as a function of centrality at RHIC should be less than the suppression seen at SPS energies where the ‘comover’ dissociation is substantial and the backward channels play no role. Furthermore, our transport calculations—in comparison to experimental data on transverse momentum spectra from pp, d+Au and Au+Au reactions—show that pre-hadronic effects are responsible for both the hardening of the hadron spectra for low transverse momenta (Cronin effect) as well as the suppression of high p T hadrons. The mutual interactions of formed hadrons are found to be negligible in central Au+Au collisions at s =200 GeV for p T ≥6 GeV/c and the sizeable suppression seen experimentally is attributed to a large extent to the interactions of ‘leading’ pre-hadrons with the dense environment.

Nuclear attenuation of fast hadrons produced in charged-currentν and $$\bar \nu $$ interactions in neoninteractions in neon

The production of hadrons in charged-current (anti)neutrino interactions is studied with the bubble chamber BEBC exposed to the CERN (anti)neutrino wide-band beam. Fast-hadron production in a neon target is found to be attenuated as compared to that in a hydrogen target. This feature is discussed within theoretical models based on the idea of a hadron formation length. The experimental results favour the ‘constituent’ over the ‘yo-yo’ length concept, and suggest a quark cross section in the order of 3 mb.

Fragmentation of coloured strings in nuclear matter

The attenuation of hadrons produced in leptonnucleus collisions is calculated in the string model of hadronization. The end points of the coloured string are assumed to interact in nuclear matter via colour exchange without changing their energy and momentum. It is shown that the interactions of the leading quark and of those produced in the colour field cause different rearrangement of the string and contribute differently to the particle production. Comparison to the data shows reasonable agreement in the region of higher energies but does not improve the previous fits at 10 GeV.

Review of data related to our understanding of the attenuation of photons (real and virtual) and hadrons as they pass through nuclear matter

Review of data related to our understanding of the attenuation of photons (real and virtual) and hadrons as they pass through nuclear matter

Interaction of jets in nuclear matter

Space-time evolution of strongly interacting systems of partons and hadrons of high energy (jets) can be investigated in experiments using nuclear targets. Lepton-nucleus collisions are particularly suitable for this task, because they allow a precise determination of the initial conditions of the jet evolution. Attenuation of hadrons leptoproduced in nuclei is analysed in two basically different models. Applications to hadron-nucleus and nucleus-nucleus collisions are indicated.

D∅ muon system with proportional drift tube chambers

The muon detection system for the Fermilab D∅ detector is described. It has better muon detection performance than other existing hadron collider detectors, with respect to both hadron attenuation length and position resolution. In the large angle region there are three large magnetized toroids and a total of 10 planes of proportional drift tube chambers made of 10 cm wide cells. At both small angles there are magnetized toroids and 9 planes of proportional drift tubes made of 3 cm diameter stainless steel tubes. The 10 cm wide cell structure is made of specially designed aluminum extrusions, which make the assembly of a whole chamber easy. The chamber is provided with vernier pads so that the position of a charged particle can be simultaneously detected in both directions perpendicular and parallel to the sense wire. The system resolution goal along the wire is ±2.0 mm and perpendicular to the wire ±0.5 mm.

Leptoproduction of hadrons from nuclear targets and fragmentation of quarks into hadrons

The attenuation of high-energy hadrons leptoproduced in heavy nuclei is discussed. It is shown that measurements of energy dependence of the attenuation can give information on the nature of the fragmentation process and also allow to determine its characteristic time.

Low Attenuation of Hadrons in Nucleus at High Energies(Hadron-Nucleus Collisions,Proceedings of the Multiparticle Dynamics)

Low Attenuation of Hadrons in Nucleus at High Energies(Hadron-Nucleus Collisions,Proceedings of the Multiparticle Dynamics)