Pion-induced Reactions Research Articles

Hadron production and propagation in pion-induced reactions on nuclei

Hadron production (π±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi ^\\pm $$\\end{document}, proton, Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda $$\\end{document}, KS0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$K_S^0$$\\end{document}, K±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$K^\\pm $$\\end{document}) in π-+C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi ^- + \ extrm{C}$$\\end{document} and π-+W\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi ^- + \ extrm{W}$$\\end{document} collisions is investigated at an incident pion beam momentum of 1.7GeV/c\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1.7~\ extrm{GeV}/c$$\\end{document}. This comprehensive set of data measured with HADES at SIS18/GSI significantly extends the existing world data on hadron production in pion induced reactions and provides a new reference for models that are commonly used for the interpretation of heavy-ion collisions. The measured inclusive differential production cross-sections are compared with state-of-the-art transport model (GiBUU, SMASH) calculations. The (semi-) exclusive channel π-+A→Λ+KS0+X\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi ^- + A \\rightarrow \\Lambda + K_S^0 +X$$\\end{document}, in which the kinematics of the strange hadrons are correlated, is also investigated and compared to a model calculation. Agreement and remaining tensions between data and the current version of the considered transport models are discussed.

Production of nuclei and hypernuclei in pion-induced reactions near threshold energies

Production of nuclei and hypernuclei in pion-induced reactions near threshold energies

Partial Wave Amplitude Analysis in Pion-Induced Reactions at the HADES Experiment

The High Acceptance Di-Electron Spectrometer (HADES) collaboration at GSI employs a pion beam to examine the characteristics of baryonic resonances and their decay channels. This pion-beam facility enables the generation of baryonic resonances at a fixed center of mass energy (√s), i.e. in the S-channel. In anticipation of conducting a more comprehensive exploration of the resonance regions in pion-proton collisions, a new implementation of the K-matrix & D-matrix frameworks is currently under development. This updated implementation aims to offer a refined mapping of these regions. Example fits are presented showing the current status and the potential of the new framework.

Observable signatures of enhanced axion emission from protoneutron stars

We perform general relativistic one-dimensional supernova (SN) simulations to identify observable signatures of enhanced axion emission from the pion-induced reaction $\pi^- + p \rightarrow n + a$ inside a newly born protoneutron star (PNS).We focus on the early evolution after the onset of the supernova explosion to predict the temporal and spectral features of the neutrino and axion emission during the first 10 s. Pions are included as explicit new degrees of freedom in hot and dense matter. Their thermal population and their role in axion production are both determined consistently to include effects due to their interactions with nucleons. For a wide range of ambient conditions encountered inside a PNS, we find that the pion-induced axion production dominates over nucleon-nucleon bremsstrahlung processes. By consistently including the role of pions on the dense matter equation of state and on the energy loss, our simulations predict robust discernible features of neutrino and axion emission from a galactic supernova that can be observed in terrestrial detectors. For axion couplings that are compatible with current bounds, we find a significant suppression with time of the neutrino luminosity during the first 10 s. This suggests that current bounds derived from the neutrino signal from SN 1987A can be improved and that future galactic supernovae may provide significantly more stringent constraints.

Theory and applications of nuclear direct reactions

These lectures, held at a school at the Galileo Galilei Institute for Theoretical Physics, give a survey of the formalism, the methods and achievements of nuclear direct reaction theory. After recapitulating the principles of quantum scattering theory, projection techniques are used to reduce the complexities of nuclear reactions to the manageable level of a set of a few selected coupled channels interacting via effective operators. Direct reactions are introduced as fast reactions proceeding preferentially through the excitation of doorway components of the nuclear many-body configurations, corresponding to a separation of scales in energy and momentum transfer. The concept of the optical model is introduced and applied to elastic scattering on nuclei. The coupled channel T-matrix formalism is discussed for pion-induced reactions on the nucleon. Applications of direct reaction to theory are illustrated for transfer reactions, inelastic scattering, and single and double charge exchange reactions with light and heavy ions.

Two-pion production in the second resonance region in π−p collisions with the High-Acceptance Di-Electron Spectrometer (HADES)

Pion-induced reactions provide unique opportunities for an unambiguous description of baryonic resonances and their coupling channels by means of a partial-wave analysis. Using the secondary pion beam at SIS18, the two-pion production in the second resonance region has been investigated to unravel the role of the N(1520)32− resonance in the intermediate ρ-meson production. Results on exclusive channels with one pion (π−p) and two pions (π+π−n, π0π−p) in the final state measured in the π−−p reaction at four different pion beam momenta (0.650, 0.685, 0.733, and 0.786 GeV/c) are presented. The excitation function of the different partial waves and Δπ, Nσ, and Nρ isobar configurations is obtained, using the Bonn-Gatchina partial-wave analysis. The N(1520)32− resonance is found to dominate the Nρ final state with the branching ratio BR=12.2%±1.9%.5 MoreReceived 20 April 2020Accepted 22 June 2020DOI:https://doi.org/10.1103/PhysRevC.102.024001©2020 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasMeson & hyperon induced nuclear reactionsNuclear many-body theoryParticle interactionsPhysical SystemsBaryonsNuclear Physics

Pion-induced production of hidden-charm pentaquarks Pc(4312),Pc(4440), and Pc(4457)

The production of the hidden-charm pentaquarks via a pion-induced reaction on a proton target is investigated within an effective Lagrangian approach. Three experimentally observed states, Pc(4312), Pc(4440), and Pc(4457), are considered in calculation, and the Reggeized t-channel meson exchange is considered as main background for the reaction π−p→J/ψn. The numerical results show that the experimental data of the total cross section at W≃5 GeV can be well explained by the contribution from the Reggeized t channel with reasonable cutoff. If the branching ratios Br[Pc→J/ψN]≃3% and Br[Pc→πN]≃0.05% are taken, the average value of the cross section from the Pc(4312) is about 1.2 nb/100 MeV, which is consistent with existing rude data at near-threshold energies. The results indicate that the branching ratios of the Pc state decays into J/ψN and πN should be small. The differential cross section shows a sharp increase at extreme forward angles due to the Reggeized t-channel contribution while the contributions from the Pc states are relatively flat. High-precision experimental measurement on the reaction π−p→J/ψn at near-threshold energies is suggested to confirm the LHCb hidden-charm pentaquarks as genuine states, and such measurement is also helpful to understand the origins of these resonance structures.

In-Medium Strangeness Production and Hyperon-Potentials

A hot topic of current research concerns the Equation of State (EoS) of nucleons and, in particular, of hyperons in dense nucleonic media. The study of the EoS at nucleon densities far beyond saturation has been initiated several decades ago, however, the behavior of the EoS for strangeness particles is still an open issue. The strangeness part of the EoS is very important not only for the physics of exotic (hyper)nuclei, but also crucial for nuclear astrophysics, e.g., neutron star physics.Here we present our recent investigations related to the theoretical treatment of in-medium hyperon-interactions as well as first preliminary experimental results from pion-induced reactions. The theoretical study is based on the well-established Non-Linear Derivative (NLD) model, which is extended to the strangeness sector via SU(6) symmetry arguments. It turns out that the NLD-predictions are consistent with microscopic models based on the chiral-EFT theory. On the other hand, recent experimental HADES-data on hyperon and kaon production from pion-induced reactions indicate sensitivities on the underlying in-medium hyperon potentials. We thus conclude that, the recent experimental data from pion-induced reactions will definitely set stringent constraints on the still less understood hyperon-potentials in nucleonic matter.

The impact of $K^{+}\Lambda$ K + Λ photoproduction on the resonance spectrum

The J\"ulich-Bonn coupled-channel framework is extended to $K^+\Lambda$ photoproduction. The spectrum of nucleon and $\Delta$ resonances is extracted from simultaneous fits to several pion-induced reactions in addition to pion, eta and $K^+\Lambda$ photoproduction off the proton. More than 40,000 data points up to a center-of-mass energy of E$\sim$2.3 GeV including recently measured double-polarization observables are analyzed. The influence of the $\gamma p\to K^+\Lambda$ channel on the extracted resonance parameters and the appearance of states not seen in other channels is investigated. The J\"ulich-Bonn model includes effective three-body channels and guarantees unitarity and analyticity, which is a prerequisite for a reliable determination of the resonance spectrum in terms of poles and residues.

Lambda - Proton Correlation in Pion-Induced Reactions at 1.7 GeV/c

World data on Λ – p scattering in pion-induced redactions are quite scare. In 2014 the HADES Collaboration performed an experiment campaign with pionnucleon reactions π¯ + A (A = C,W) at 1.7 GeV/c. Hereby, the exclusive channel π¯ + p → K0 + Λ (Λ + p → Λ + p) may provide information on Λ proton scattering and moreover shed light on the short range interaction using dedicated simulations for comparison. The on-going analysis of the exclusive channel with especial emphasis on the event selection is outlined.

Observation of Narrow N+(1685) and N0(1685) Resonances in γN → πηN Reactions

Observation of a narrow structure at $W\sim 1.68$ GeV in the excitation functions of some photon- and pion-induced reactions may signal a new narrow isospin-1/2 $N(1685)$ resonance. New data on the $\gamma N \to \pi \eta N$ reactions from GRAAL seems to reveal the signals of both $N^+(1685)$ and $N^0(1685)$ resonances.

Understanding the nature of heavy pentaquarks and searching for them in pion-induced reactions

We investigate the reaction π−p→π−J/ψp via the open-charm hadron rescattering diagrams. Due to the presence of the triangle singularity (TS) in the rescattering amplitudes, the TS peaks can simulate the pentaquark-like resonances arising in the J/ψp invariant mass distributions, which may bring ambiguities on our understanding of the nature of the exotic states. Searching for the heavy pentaquark in different processes may help us to clarify the ambiguities, because of the highly process-dependent characteristic of the TS mechanism.

Production and decay of baryonic resonances in pion induced reactions

Pion induced reactions give unique opportunities for an unambiguous description of baryonic resonances and their coupling channels. A systematic energy scan and high precision data, in conjunction with a partial wave analysis, allow for the study of the excitation function of the various contributions. A review of available world data unravels strong need for modern facilities delivering measurements with a pion beam. Recently, HADES collaboration collected data in pion-induced reactions on light ( 12 C) and heavy ( 74 W) nuclei at a beam momentum of 1.7 GeV/c dedicated to strangeness production. It was followed by a systematic scan at four different pion beam momenta (0.656, 0.69, 0.748 and 0.8 GeV/c) in π − − p reaction in order to tackle the role of N (1520) resonance in conjunction with the intermediate ρ production. First results on exclusive channels with one pion ( π − p ) and two pions ( n π + π − , p π − π 0 ) in the final state are discussed.

Studyingρ–N couplings with HADES in pion-induced reactions

The High-Acceptance Di-Electron Spectrometer (HADES) operates at the GSI Helmholtzzentrum fur Schwerionenforschung in Darmstadt with pion, proton and heavyion beams provided by the synchrotron SIS18. In summer 2014, HADES took data using a pion beam on carbon and polyethylene targets. A large part of the data was taken at a pion beam momentum of 0.69 GeV/c in order to explore di-pion and di-electron production in the second resonance region and the sub-threshold coupling of the ρ to baryonic resonances. In this contribution lepton identification will be discussed as well the purity of reconstructed e + e − . Finally we will show the preliminary di-electon raw spectra.

Pion-induced reactions for charmed baryons

We study pion induced reactions for charmed baryons $B$, $\pi$ + N $\rightarrow$ $D^*$ + $B$. First we estimate charm production rates in comparison with strangeness production using a Regge model which is dominated by vector ($D^*$ or $K^*$ ) Reggeon exchange. Then we examine the production rates of various charmed baryons $B$ in a quark-diquark model. We find that the production of excited states are not necessarily suppressed, a sharp contrast to strangeness production, which is a unique feature of the charm production with a large momentum transfer.

Spallation cross sections for natFe and natCu targets for 120 GeV/c protons and pions

Spallation cross sections from thin natural copper and iron targets bombarded by a mixed 120 GeV/c proton/pion beam were measured in an activation experiment at CERN. The beam intensity was monitored by a calibrated ionization chamber and the activity of several spallation products was measured (14 for copper and 16 for iron) by \ensuremath{\gamma} spectrometry, allowing the absolute cross section of the mixed hadron beam to be derived. Monte Carlo simulations with the FLUKA code provided the ratio between the proton- and pion-induced reaction cross sections for a given spallation product, allowing us to extrapolate the individual cross sections for the proton- and the pion-induced reactions. Where possible the values were compared with literature data and showed to be generally in agreement with the highest energy data available.

Search for Θ + via the Pion Induced Reaction at J-PARC: J-PARC E19

The Θ+ pentaquark baryon was searched for via the π−p → K−X reaction at J-PARC. π− meson beams were irradiated on the liquid hydrogen target with the beam momentum of 1.92 GeV/c. In the missing mass spectrum, no peak structure corresponding to Θ+ mass was observed. The preliminary upper limit of the differential cross section averaged over the scattering angle of 2° to 15° at the laboratory frame was less than 0.3 μb/sr at the 90 % confidence level in the missing mass region over 1.51 to 1.55 GeV/c2.

HADRON PHYSICS AT J-PARC — CURRENT STATUS AND FUTURE PROSPECTS

The J-PARC Hadron Facility is designed as a multipurpose experimental facility for a wide range of particle and nuclear physics programs, aiming to provide the world highest intensity secondary beams. The first primary beam has been successfully extracted and transported to the beam dump on January 2009. Currently three secondary beam lines come into operation, and the new beam line will be completed in the early summer of 2010. Various experimental programs are proposed at each beamline and some of them are preparing to start physics run. Most of the experimental researches concerns the studies of hypernuclei and searches for new hadronic states. As the first experiment at the J-PARC Hadron Facility, search for the Θ+ pentaquark via pion-induced hadronic reaction will be performed in the autumn of 2010. The current status and recent results of the commissioning for the beam line are reported.

Theoretical study and systematic analysis of positive pion-induced fission cross-sections of heavy nuclei

The study of pion-induced nuclear reactions are important because pion not only plays the role of a projectile, but also serves as intermediate step particle as in the case of interaction of other projectiles like photon and antiproton. The studies of pion-induced nuclear reaction have important applications, such as in accelerator-driven system (ADS) and in basic nuclear research to probe the nuclear structure. The studies of pion-induced reaction, particularly fission, are as important as the studies of nucleon-induced nuclear reactions, because inter-nuclear cascades in spallation targets are partly propagated by pions. The pion-induced fission has not been as much studied as fission induced by nucleons. The reason is that there is a limited number of facilities available for production of pions, and beam time is scant. Previously, pion-induced fission has been studied using dielectric track-detectors; at present the work has not been carried out using this technique due to non-availability of exposure facilities. So there is a need of computer codes to study cross-section of pion-induced fission, and the proper documentation of existing experimental data. In the present work, fission cross-sections induced by positive pions, for targets 209Bi, 231Pa, 232Th, 238U and 239Pu are computed using the cascade–exciton model code CEM95 upto 2500 MeV energy. Also a systematics of positive pion-induced fission is performed on the basis of that performed cross-sections of proton-induced fission. The computed cross-sections of fission using CEM95 have been compared with the available experimental data and with the fission cross-sections obtained using the systematics analysis. A reasonable agreement has been observed.

Further evidence for [formula omitted] from photoproduction of hyperons

We report further evidence for N(1900)P13 from an analysis of a large variety of photo- and pion-induced reactions, in particular from the new CLAS measurements of double polarization observables for photoproduction of hyperons. The data are consistent with two classes of solutions both requiring contributions from N(1900)P13 but giving different N(1900)P13 pole positions. (M−iΓ/2)=(1915±50)−i(90±25) MeV covers both solutions. The small elasticity of 10% or less explains why it was difficult to observe the state in πN elastic scattering.N(1900)P13 is a 2-star resonance which is predicted by symmetric three-quark models. In diquark–quark models, the existence of the state is not expected.