Multipion Production Research Articles

Studies of π−-12C reactions at 0.7GeV/c with the HADES spectrometer

Abstract. The HADES collaboration has recently studied the π− + C reaction at 0.685 GeV/c, using the GSI pion beam. This provides a first insight in the pion-nucleus dynamics in the energy range above the Δ(1232) resonance, which has been very poorly studied and is relevant for the study of heavy-ion collisions in the few GeV range. Measurements of π±, p, d and t were provided in various exit channels (inclusive, pπ−, pπ+, pp, π+π−, pπ−π+…,) and compared to predictions of the INCL++ cascade and of transport models (SMASH, RQMD.RMF, GIBUU). The results allow to test selectively the capacity ofsuch models to describe the various mechanisms (quasi-elastic, multipion production, rescatterings and pion absoprtion). The sensitivity of the data measured in the quasi-elastic channel to short range correlations is also investigated.

Inferring astrophysical neutrino sources from the Glashow resonance

We infer the ultrahigh energy neutrino source by using the Glashow resonance candidate event recently identified by the IceCube Observatory. For the calculation of the cross section for the Glashow resonance, we incorporate both the atomic Doppler broadening effect and initial state radiation ν¯ee−→W−γ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\overline{\ u}}_e{e}^{-}\ o {W}^{-}\\gamma $$\\end{document}, which correct the original cross section considerably. Using available experimental information, we have set a generic constraint on the ν¯e\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\overline{\ u}}_e $$\\end{document} fraction of astrophysical neutrinos, which excludes the μ-damped pγ source around 2σ confidence level under the assumption that neutrino production is dominated by the ∆-resonance. While a weak preference has been found for the pp source, next-generation measurements will be able to distinguish between ideal pp and pγ sources with a high significance assuming an optimistic single power-law neutrino spectrum. The inclusion of multi-pion production at very high energies for the neutrino source can weaken the discrimination power. In this case additional multimessenger information is needed to distinguish between pp and pγ sources.

Unified thermal model for photohadronic neutrino production in astrophysical sources

High-energy astrophysical neutrino fluxes are, for many applications, modeled as simple power laws as a function of energy. While this is reasonable in the case of neutrino production in hadronuclear pp sources, it typically does not capture the behavior in photohadronic pγ sources: in that case, the neutrino spectrum depends on the properties of the target photons the cosmic rays collide with and on possible magnetic-field effects on the secondary pions and muons. We show that the neutrino production from known photohadronic sources can be reproduced by a thermal (black-body) target-photon spectrum if one suitably adjusts the temperature, thanks to multi-pion production processes. This allows discussing neutrino production from most known pγ sources, such as gamma-ray bursts, active galactic nuclei and tidal disruption events, in terms of a few parameters. We apply this thermal model to study the sensitivity of different classes of neutrino telescopes to photohadronic sources: we classify the model parameter space according to which experiment is most suitable for detection of a specific source class and demonstrate that different experiment classes, such as dense arrays, conventional neutrino telescopes, or radio-detection experiments, cover different parts of the parameter space. Since the model can also reproduce the flavor and neutrino-antineutrino composition, we study the impact on the track-to-shower ratio and the Glashow resonance.

Study of multipion production in np-interaction at intermediate energies

The reactions of the multipion production in np-interactions were studied at the momenta of incident neutrons from 1.73 to 5.20 GeV/c. The pions multiplicity of the studied reactions was from 2 to 6. It was shown that the characteristics of the reactions were satisfactory described within the framework of OPER-model (One Pion Reggeizied Exchange). Additionally the diagrams of one baryon exchange (OBE) were used for a better description of the data at the momenta of incident neutrons below 3 GeV/c.

Pion Fluctuation in High-energy Collisions --- A Chaos-based Quantitative Estimation with Visibility Graph Technique

We propose a new approach for studying pion fluctuation for deeper understanding of the dynamical process involved, from a perspective of fBm-based complex network analysis method called Visibility graph Analysis. This chaos-based, rigorous, non-linear technique is applied to study the erratic behavior of multipion production in \pi^{-}-Ag/Br interactions at 350 GeV. This method can offer reliable results with finite data points. The Power of Scale-freeness of Visibility Graph denoted by-PSVG is a measure of fractality, which can be used as a quantitative parameter for the assessment of the state of a chaotic system. The event-wise fluctuation of the multipion production process can be described by this parameter-PSVG. From the analysis of the PSVG parameter, we can quantitatively confirm that fractal behavior of the particle production process depends on the target excitation and also the fractality decreases with the increase of target excitation.

Fractal study of pion void probability distribution in ultrarelativistic nuclear collision and its target dependence

There are numerous existing works on investigating the dynamics of particle production process in ultrarelativistic nuclear collision. In the past, fluctuation of spatial pattern has been analyzed in terms of the scaling behavior of voids. But analysis of the scaling behavior of the void in fractal scenario has not been explored yet. In this work, we have analyzed the fractality of void probability distribution with a completely different and rigorous method called visibility graph analysis, analyzing the void-data produced out of fluctuation of pions in [Formula: see text]S–AgBr interaction at 200 GeV in pseudo-rapidity [Formula: see text] and azimuthal angle [Formula: see text] space. The power of scale-freeness of visibility graph denoted by PSVG is a measure of fractality, which can be used as a quantitative parameter for the assessment of the state of chaotic system. As the behavior of particle production process depends on the target excitation, we can dwell down the void probability distribution in the event-wise fluctuation resulted out of the high energy interaction for different degree of target excitation, with respect to the fractal scenario and analyze the scaling behavior of the voids. From the analysis of the PSVG parameter, we have observed that scaling behavior of void probability distribution in multipion production changes with increasing target excitation. Since visibility graph method is a classic method of complex network analysis, has been applied over fractional Brownian motion (fBm) and fractional Gaussian noises (fGn) to measure the fractality and long-range dependence of a time series successfully, we can quantitatively confirm that fractal behavior of the void probability distribution in particle production process depends on the target excitation.

Choked jets and low-luminosity gamma-ray bursts as hidden neutrino sources

We consider gamma-ray burst (GRB) jets that are choked by extended material as sources of high-energy cosmic neutrinos. We take into account the jet propagation physics both inside the progenitor star and the surrounding dense medium. Radiation constraints, which are relevant for high-energy neutrino production are considered as well. Efficient shock acceleration of cosmic rays is possible for sufficiently low-power jets and/or jets buried in a dense, extended wind or outer envelope. Such conditions also favor GRB jets to become stalled, and the necessary conditions for stalling are explicitly derived. Such choked jets may explain transrelativistic supernovae (SNe) and low-luminosity (LL) GRBs, giving a unified picture of GRBs and GRB-SNe. Focusing on this unified scenario for GRBs, we calculate the resulting neutrino spectra from choked jets including the relevant microphysical processes such as multipion production in pp and pgamma interactions, as well as the energy losses of mesons and muons. We obtain diffuse neutrino spectra using the latest results for the luminosity function of LL GRBs. Although uncertainties are large, we confirm that LL GRBs can potentially give a significant contribution to the diffuse neutrino flux. Our results are consistent with the present IceCube data and do not violate the stacking limits on classical high-luminosity GRBs. We find that high-energy neutrino production in choked jets is dominated by pgamma interactions. These sources are dark in GeV-TeV gamma-rays, and do not contribute significantly to the Fermi diffuse gamma-ray background. Assuming stalled jets can launch a quasi-spherical shock in the dense medium, precursor TeV neutrinos emerging prior to the shock breakout gamma-ray emission can be used as smoking gun evidence for a choked jet model for LL GRBs. Our results strengthen the relevance of wide field-of-view sky monitors.

Multifractality in relativistic charged particles produced at SPS energies

The multifractal analysis of relativistic shower particles produced in 32S–emulsion interactions at 200AGeV has been investigated using the method of modified multifractal moments, Gq, in pseudo-rapidity space. The anomalous fractal dimension, dq, and generalized fractal dimensions, Dq, are determined for the present data for different order of moment. The experimental data reflects multifractal geometry in a multipion production process. The downward concave shape of the multifractal spectral function, f(αq), gives an evidence for self-similar cascade mechanism. The multifractal specific heat has also been evaluated for the present data using the generalized fractal dimensions, Dq. We compared our experimental results with those obtained from simulated events of the Lund Monte Carlo Code FRITIOF and uncorrelated Monte Carlo events, (MC-RAND) generated randomly in pseudorapidity space based on the assumption of independent emission of particles. The experimental data on multifractality has been found to exhibit a remarkable proximity to the analogous data obtained from the FRITIOF code and the uncorrelated Monte Carlo events.

Multifractality in charged pion production at a few GeV/n

The multifractal analysis of charged pion produced in 16O–AgBr interactions at 2.1 AGeV and 24Mg–AgBr interactions at 4.5 AGeV has been investigated using the Takagi moment method in pseudo-rapidity space. The generalized fractal dimensions Dq are determined for these two interactions for different orders of moment. Experimental data reflects multifractal geometry in the multipion production process. From the knowledge of the generalized fractal dimensions Dq, the multifractal specific heat has also been evaluated for these data. A detailed comparison is presented with the results obtained from 12C–AgBr and 28Si–AgBr interactions at 4.5 AGeV/c, 28Si–AgBr interactions at 14.5 A GeV/c, 16O–AgBr interactions 60 AGeV and 32S–AgBr interactions 200 AGeV from the recent literatures.

Extension of the Liège intranuclear cascade model at incident energies between 2 and 12 GeV. Aspects of pion production

Abstract The validity of the standard version of the Liege Intra-Nuclear Cascade (INCL4) model, which has been shown to be quite successful for the description of spallation reactions, is limited to an upper incident energy of ∼2 GeV, because inelastic elementary processes are restricted to the excitation and de-excitation of the Delta resonance. In this paper, the INCL4 model is extended to higher incident energy by including other inelastic elementary collisions. However, excitation of heavier baryonic resonances is replaced by direct multipion production in elementary nucleon–nucleon and pion–nucleon collisions. The predictions of the modified model for production of charged pions by proton and pion beams off nuclei are compared with experimental data of the HARP Collaboration for beam energies between 2 and 12 GeV. The apparent duality between the approach based on excitation of numerous baryonic resonances and our approach is briefly discussed.

Chaos in compound hadrons in high-energy hadronic interactions

In this paper, a detailed study of the chaotic behavior of compound hadrons (pions plus protons) in π−–AgBr interactions at 350 GeV c−1 has been performed with the help of the parameter ‘entropy index’ μq, which is a measure of the chaotic behavior in multipion production processes. This index describes the event-to-event fluctuation of factorial moments that measures the spatial fluctuation of multiplicity distribution. The analysis reveals a large value for the entropy index signifying the chaotic behavior of the produced compound hadrons in high-energy hadron–nucleus interactions. It was been observed that the multipion production process becomes less chaotic with increasing average multiplicity of the final states. The study has been further extended to pions, and the corresponding results are compared.

Observation of an “ABC” Effect in Proton-Proton Collisions

The cross section for inclusive multipion production in the pp-->ppX reaction was measured at COSY-ANKE at four beam energies, 0.8, 1.1, 1.4, and 2.0 GeV, for low excitation energy in the final pp system, such that the diproton quasiparticle is in the 1S0 state. At the three higher energies, the missing-mass M_{X} spectra show a strong enhancement at low M_{X}, corresponding to an Abashian-Booth-Crowe effect that moves steadily to larger values as the energy is increased. Despite the missing-mass structure looking very different at 0.8 GeV, the variation with M_{X} and beam energy are consistent with two-pion production being mediated through the excitation of two Delta(1232) isobars, coupled to S and D states of the initial pp system. There is no sign of any resonancelike structure in the energy dependence of the type recently observed for the pn-->dpi;{0}pi;{0} total cross section.

Target excitation dependence of the entropy index in 350 GeV/c π−–AgBr collisions

In this paper a detailed study on the erratic behaviour of multiparticle production in π−–AgBr interactions at 350 GeV has been performed with the help of the parameter ‘entropy index’ μq, which is a measure of chaotic behaviour in multipion production processes. This index describes the event-to-event fluctuation of factorial moments which measures the spatial fluctuation of multiplicity distribution. The analysis reveals a large value for the entropy index, signifying the chaotic behaviour of the produced pions in high-energy hadron–nucleus interactions. It has been observed that the multipion production process becomes less chaotic with an increasing average multiplicity of the final states. The study has further been extended to know the target excitation dependence of chaoticity of pions; a positive dependence is indicated by the data.

Study of resonant processes for multi-pion production in [formula omitted] annihilation

In frame of a phenomenological approach based on Compton-like Feynman amplitudes, we study multi-pion production in antiproton nucleon collisions. The main interest of this reaction is related to the possibility to study the properties of the presumable N¯N atom and of its resonances. For the case of formation of a scalar or pseudoscalar resonant state, with IG(JP)=1−(0±), 0+(0−) numerical results are obtained. The differential cross section in an experimental set-up where the pions invariant mass is measured, is given with explicit dependence on the lepton pair and pions invariant mass.

Signature of void probability scaling in multipion production at a few GeV∕nucleon

A study of rapidity gap probability has been carried out in $^{16}\mathrm{O}\text{\ensuremath{-}}\text{AgBr}$ interactions at $2.1A\phantom{\rule{0.3em}{0ex}}\text{GeV}$. The study reveals scaling behavior of the void probability. This analysis also confirms the validity of the linked-pair approximation for the $N$-particle cumulant correlation functions in the low energy regime.

Multiplicity-dependent chaotic pionization in ultra-relativistic nuclear interactions

The fluctuation of spatial patterns from event to event has been investigated by analysing the pionization data of 32S–AgBr interactions at 200 A GeV in terms of a new parameter entropy index, μq, which is a measure of chaotic behaviour in multipion production process. It is observed that the multipion production process becomes more chaotic with the increase of average multiplicities of the final states.

Analysis of fluctuation of fluctuations in 32S–AgBr interactions at 200 A GeV

The possible signature of chaotic behavior of multiparticle production in nucleus–nucleus collision has been investigated with the help of a new parameter, the entropy index μ q . This index describes the event-to-event fluctuation of factorial moments which measures the spatial fluctuation of the multiplicity distribution. An analysis of 32S–AgBr interaction data at 200 A GeV reveals a large value for the entropy index signifying chaotic behavior of the multipion production process in ultrarelativistic nuclear interactions.

Multipion coherent effects in high energy heavy-ion collisions

Multipion production in high energy nucleus-nucleus collisions is considered in the model of the pion radiation by classical current. Strong coherent effects of narrowing of pion longitudinal and transverse momenta distributions are predicted at the RHIC energy. The coherence enhances the large pseudorapidities producing the bump in the distribution. The growth of the average pion multiplicity and the oscillation effect in the multiplicity distribution are caused by the coherence as well.

Multi-pion production in the dd→ αX reaction

A simple model, based on two parallel and independent NN→ dπ processes, has recently been proposed for two-pion production in the dd→ αX reaction. It reproduces all observed features, including the sharp peak structure in momentum distributions (the ABC effect) and the strong oscillations in the deuteron vector and tensor analyzing powers. This model is now extended to describe also four-pion production with the same basic mechanism, but with two np→ dππ processes as input. The calculations of the high missing mass spectra are in fair agreement with the experimental data for beam energies in the range 1.9< T d <2.4 GeV.

Factorial and fractal analysis of the multipion production process at 350 GeV/c.

The self-similarity property of the multiparticle production process is investigated from different angles using 350 GeV/c ${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$-AgBr data of our own. An intermittency analysis in pseudorapidity-azimuthal angle space shows that a one-dimensional analysis gives considerably underestimated exponent values and thus proves the necessity of probing higher dimensions. The study of factorial correlators at different bin widths reveals an approximate linearity of log-log plots of correlators versus the inverse rapidity distance over a limited region and bin width independence of correlators calculated at a small rapidity distance. A dimension-independent relation between factorial correlators and moments is utilized to eliminate the intermittency-nonintermittency ambiguity. A newly defined G moment, which can suppress the statistical bias, is used to extract the dynamical signals in the framework of a fractal analysis. It also indicates a rough link between factorial and fractal moment methods, which has been missing so far.