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Articles de revues sur le sujet « Pions neutres »

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Auteur : Grafiati
Publié le 28 février 2024

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1

Manga, Peter J., E. W. Likta et P. B. Teru. « COMPARATIVE STUDY ON CHARGED AND NEUTRAL PION-NUCLEON COUPLING CONSTANTS USING YUKAWA POTENTIAL MODEL ». FUDMA JOURNAL OF SCIENCES 5, no 4 (28 janvier 2022) : 167–73. http://dx.doi.org/10.33003/fjs-2021-0504-803.

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The meson field theory based on the Yukawa model for nuclear forces is estimated using a simple relationship between the charged and neutral pion- nucleon coupling constant. This signifies that the charged coupling constant is larger compared to the value obtains for neutral pions. Therefore since np interaction is stronger than the pp interaction, we look at the value obtained for charged pion – nucleon constant which gives good agreement with one of the recent experimental values, and then the splitting between the charged and neutral pion – nucleon coupling constants is practically the same as that between charged and neutral pion mass. In this case, the mass difference between the charged and neutral pion is also calculated to assess the amount of charge dependence of the Neutron – Neutron scattering length
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2

JOULAEIZADEH, L., J. BACELAR, M. ESLAMI-KALANTARI, I. GAŠPARIĆ, N. KALANTAR-NAYESTANAKI, H. LÖHNER, H. MARDANPOUR et al. « PIONIC FUSION AT SUBTHRESHOLD ENERGIES ». International Journal of Modern Physics A 24, no 02n03 (30 janvier 2009) : 539–43. http://dx.doi.org/10.1142/s0217751x09044024.

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In order to study the role of pions and clustering phenomena in nuclei, two experiments have been performed using the AGOR accelerator facility. In collisions of two nuclei a pion and a fused nucleus were produced. The examined reactions were 4He(3He, π0)7Be and 6Li(4He, π0)10B at beam energies about 10 MeV above the coherent pion production threshold (256 MeV and 236.4 MeV, respectively). Since the available energy is well below the pion production threshold in an elementary nucleon-nucleon process, a highly coherent mechanism is needed. We identified the reaction by measuring the fused system in the magnetic spectrometer and the produced neutral pions in the Plastic Ball detection system with large acceptance. Our experimental setup provided the exclusive cross sections by identifying all products in overdetermined kinematics. Here we present the preliminary results of the analysis for the second reaction. Angular distribution of neutral pions will be discussed.
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KO, CHE MING, YONGSEOK OH et JUN XU. « MEDIUM EFFECTS ON CHARGED PION RATIO IN HEAVY ION COLLISIONS ». International Journal of Modern Physics E 19, no 08n09 (septembre 2010) : 1763–72. http://dx.doi.org/10.1142/s0218301310016193.

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We have recently studied in the delta-resonance–nucleon-hole model the dependence of the pion spectral function in hot dense asymmetric nuclear matter on the charge of the pion due to the pion p-wave interaction in nuclear medium. In a thermal model, this isospin-dependent effect enhances the ratio of negatively charged to positively charged pions in neutron-rich nuclear matter, and the effect is comparable to that due to the uncertainties in the theoretically predicted stiffness of nuclear symmetry energy at high densities. This effect is, however, reversed if we also take into account the s-wave interaction of the pion in nuclear medium as given by chiral perturbation theory, resulting instead in a slightly reduced ratio of negatively charged to positively charged pions. Relevance of our results to the determination of the nuclear symmetry energy from the ratio of negatively to positively charged pions produced in heavy ion collisions is discussed.
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4

ROBSON, B. A. « PARITY OF CHARGED PIONS ». International Journal of Modern Physics E 20, no 08 (août 2011) : 1677–86. http://dx.doi.org/10.1142/s0218301311019659.

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This paper discusses the parity of charged pions. It is shown that the original determination of the parity of the negatively charged pion using the capture of negatively charged pions in deuterium to form two neutrons is not conclusive if the pion has a complex substructure. It is demonstrated that this experiment is compatible with the mixed-parity nature of the π- arising in a recent composite model. A major consequence of this is that CP may be conserved in the [Formula: see text] system.
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5

Dominguez, C. A., M. Loewe et M. Lushozi. « Scalar Form Factor of the Pion in the Kroll-Lee-Zumino Field Theory ». Advances in High Energy Physics 2015 (2015) : 1–4. http://dx.doi.org/10.1155/2015/803232.

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The renormalizable Kroll-Lee-Zumino field theory of pions and a neutral rho-meson is used to determine the scalar form factor of the pion in the space-like region at next-to-leading order. Perturbative calculations in this framework are parameter-free, as the masses and the rho-pion-pion coupling are known from experiment. Results compare favorably with lattice QCD calculations.
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6

WOLFE, C. E., S. NOZAWA, M. N. BUTLER et B. CASTEL. « POLARIZABILITY EFFECTS IN PION PHOTOPRODUCTION ». International Journal of Modern Physics E 05, no 01 (mars 1996) : 227–37. http://dx.doi.org/10.1142/s0218301396000116.

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We investigate the pion photoproduction reaction γN→γNπ as a probe of pion electromagnetic polarizability. This reaction had been proposed as having the potential to resolve the long standing discrepancy between measurements of pion polarizabilities and the predictions of Chiral Perturbation Theory. We have carried out a series of calculations of ratios of substructure — related to background contributions for energies below the Δ resonance — but have to report that the largest values are found in the high-energy tail of the photon spectrum and that these are of the order of 0.1% for charged pions and 1% for neutral pions. We conclude that these sensitivities are not yet accessible experimentally, and that this regime of energy should be excluded from current consideration.
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ZHANG, SUN, et FAN WANG. « RELATIVISTIC HYDRODYNAMICS WITH SPONTANEOUS CHIRAL SYMMETRY BREAKING ». International Journal of Modern Physics E 12, no 05 (octobre 2003) : 675–81. http://dx.doi.org/10.1142/s0218301303001491.

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We study the hydrodynamics of the nuclear matter of two flavors of light quarks with spontaneous chiral symmetry breaking based on the Poisson bracket method. The effects of mass are included and the full hydrodynamic equation for pions is given. The in-medium dispersion relation of pions in the neutron rich background state and the possibility of the phase transition to pion condensation are also discussed.
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8

OBERLE, M., et B. KRUSCHE. « QUASIFREE PHOTOPRODUCTION OF PION-PAIRS OF PROTONS AND NEUTRONS ». International Journal of Modern Physics : Conference Series 26 (janvier 2014) : 1460106. http://dx.doi.org/10.1142/s2010194514601069.

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Beam-helicity asymmetries and mass-differential cross sections have been measured at the MAMI accelerator in Mainz for the photoproduction of neutral and mixed-charge pion pairs in the reactions γp → nπ0π+ and γp → pπ0π0 off free protons and γd → (p)pπ0π-, γd → (n)pπ0π0 and γd → (n)nπ0π+, γd → (p)nπ0π0 off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced in bremsstrahlung processes of longitudinally polarized electrons and tagged with the Glasgow-Mainz magnetic spectrometer. The decay products (photons, protons neutrons and charged pions) were detected in the 4π electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. Using a full kinematic reconstruction of the final state, excellent agreement was found between the results for free and quasi-free protons, indicate that the quasi-free neutron results are also a close approximation of the free-neutron results. Comparison of the results to predictions of model calculations portend that especially the reaction mechanisms in the production of the mixed-charge final states are still not well understood, in particular at low incident photon energies in the second nucleon resonance region.
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9

Prozorov, Alexandr. « Neutral meson production in Ag+Ag at √SNN = 2.55 GeV ». EPJ Web of Conferences 291 (2024) : 04001. http://dx.doi.org/10.1051/epjconf/202429104001.

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Abstract. Relativistic nucleus-nucleus collisions offer a unique possibility for studying nuclear matter under the influence of high temperature and pressure. During the collision a system of interacting nucleons, resonances, and mesons, called hadronic fireball, is created. HADES is a unique experiment capable of simultaneously measuring all three species of pions for this energy regime. Results on neutral pion production in Ag + Ag collisions at √SNN = 2.55 GeV (beam energy 1.58 A GeV) with 14 billion collected events will be presented. A measurement of a directed and elliptic flow, and yields of neutral pions corrected for detector acceptance and efficiency will be shown with respect to transverse momentum and rapidity for certain centrality classes; and further compared with the data, and charged pion data measured in the same experiment. In addition, the obtained results will be confronted with up-to-date model calculations.
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10

Bäni, Lukas, Andreas Alexopoulos, Marina Artuso, Felix Bachmair, Marcin Bartosik, Helge Beck, Vincenzo Bellini et al. « A Study of the Radiation Tolerance of CVD Diamond to 70 MeV Protons, Fast Neutrons and 200 MeV Pions ». Sensors 20, no 22 (20 novembre 2020) : 6648. http://dx.doi.org/10.3390/s20226648.

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We measured the radiation tolerance of commercially available diamonds grown by the Chemical Vapor Deposition process by measuring the charge created by a 120 GeV hadron beam in a 50 μm pitch strip detector fabricated on each diamond sample before and after irradiation. We irradiated one group of samples with 70 MeV protons, a second group of samples with fast reactor neutrons (defined as energy greater than 0.1 MeV), and a third group of samples with 200 MeV pions, in steps, to (8.8±0.9) × 1015 protons/cm2, (1.43±0.14) × 1016 neutrons/cm2, and (6.5±1.4) × 1014 pions/cm2, respectively. By observing the charge induced due to the separation of electron–hole pairs created by the passage of the hadron beam through each sample, on an event-by-event basis, as a function of irradiation fluence, we conclude all datasets can be described by a first-order damage equation and independently calculate the damage constant for 70 MeV protons, fast reactor neutrons, and 200 MeV pions. We find the damage constant for diamond irradiated with 70 MeV protons to be 1.62±0.07(stat)±0.16(syst)× 10−18 cm2/(p μm), the damage constant for diamond irradiated with fast reactor neutrons to be 2.65±0.13(stat)±0.18(syst)× 10−18 cm2/(n μm), and the damage constant for diamond irradiated with 200 MeV pions to be 2.0±0.2(stat)±0.5(syst)× 10−18 cm2/(π μm). The damage constants from this measurement were analyzed together with our previously published 24 GeV proton irradiation and 800 MeV proton irradiation damage constant data to derive the first comprehensive set of relative damage constants for Chemical Vapor Deposition diamond. We find 70 MeV protons are 2.60 ± 0.29 times more damaging than 24 GeV protons, fast reactor neutrons are 4.3 ± 0.4 times more damaging than 24 GeV protons, and 200 MeV pions are 3.2 ± 0.8 more damaging than 24 GeV protons. We also observe the measured data can be described by a universal damage curve for all proton, neutron, and pion irradiations we performed of Chemical Vapor Deposition diamond. Finally, we confirm the spatial uniformity of the collected charge increases with fluence for polycrystalline Chemical Vapor Deposition diamond, and this effect can also be described by a universal curve.
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11

LIU, YAO-BEI, et SHUAI-WEI WANG. « THE PRODUCTION OF THE NEUTRAL AND CHARGED TOP PIONS ASSOCIATED WITH THE W BOSON AT THE ILC ». International Journal of Modern Physics A 23, no 32 (30 décembre 2008) : 5173–80. http://dx.doi.org/10.1142/s0217751x0804264x.

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The top pions [Formula: see text] are the typical particles predicted by the top-color-assisted technicolor (TC2) model, and the observation of these particles can be regarded as the direct evidence of the TC2 model. In this paper, we study the charged and neutral top pion production process [Formula: see text]. The results show that the production rates can reach the level of tens of fb with reasonable parameter values. So one can expect that enough signals could be produced in the International Linear Collider (ILC) experiments. Furthermore, the flavor-changing (FC) decay mode [Formula: see text] is the best channel for detecting the neutral top pion, due to the clean SM background. With a large number of events and the clean background, the neutral top pion should be observable in future ILC experiments.
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12

Abratenko, P., R. An, J. Anthony, L. Arellano, J. Asaadi, A. Ashkenazi, S. Balasubramanian et al. « Electromagnetic shower reconstruction and energy validation with Michel electrons and π0 samples for the deep-learning-based analyses in MicroBooNE ». Journal of Instrumentation 16, no 12 (1 décembre 2021) : T12017. http://dx.doi.org/10.1088/1748-0221/16/12/t12017.

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Abstract This article presents the reconstruction of the electromagnetic activity from electrons and photons (showers) used in the MicroBooNE deep learning-based low energy electron search. The reconstruction algorithm uses a combination of traditional and deep learning-based techniques to estimate shower energies. We validate these predictions using two νμ-sourced data samples: charged/neutral current interactions with final state neutral pions and charged current interactions in which the muon stops and decays within the detector producing a Michel electron. Both the neutral pion sample and Michel electron sample demonstrate agreement between data and simulation. Further, the absolute shower energy scale is shown to be consistent with the relevant physical constant of each sample: the neutral pion mass peak and the Michel energy cutoff.
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13

Narimani Charan, Abtin. « Particle identification with the Belle II calorimeter using machine learning ». Journal of Physics : Conference Series 2438, no 1 (1 février 2023) : 012111. http://dx.doi.org/10.1088/1742-6596/2438/1/012111.

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Abstract I present an application of a convolutional neural network (CNN) to separate muons and pions in the Belle II electromagnetic calorimeter (ECL). The ECL is designed to measure the energy deposited by charged and neutral particles. It also provides important contributions to the particle identification (PID) system. Identification of low-momenta muons and pions in the ECL is crucial if they do not reach the outer muon detector. Track-seeded cluster energy images provide the maximal possible information. The shape of the energy depositions for muons and pions in the crystals around an extrapolated track at the entering point of the ECL is used together with crystal positions in θ − ϕ plane and transverse momentum of the track to train a CNN. The CNN exploits the difference between the dispersed energy depositions from pion hadronic interactions and the more localized muon electromagnetic interactions. Using simulation, the performance of the CNN algorithm is compared with other PID methods at Belle II which are based on track-matched clustering information. The results show that the CNN PID method improves muon-pion separation in low momentum.
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14

AHMADOV, A. I., E. A. KURAEV et M. K. VOLKOV. « GENERALIZED POLARIZABILITY OF NEUTRAL PIONS OF THE PROCESS e-e+ →π0π0γ IN THE NJL MODEL ». International Journal of Modern Physics A 26, no 20 (10 août 2011) : 3337–46. http://dx.doi.org/10.1142/s0217751x11053870.

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Differential distributions in the π0π0γ system created in the annihilation channel of an electron–positron collision are considered. The energy fractions of the pions (Dalitz-plot) distribution are presented in a general form and in approximation of intermediate vector mesons (excited and ordinary ones). It is pointed out that in relevant experiments the generalized polarizability of the neutral pion can be measured. Numerical illustrations are presented.
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15

Jerusalimov, Alexander, Susanna Arakelian, Alexander Belyaev, Vladimir Ladygin et Alexander Troyan. « Study of multipion production in np-interaction at intermediate energies ». EPJ Web of Conferences 204 (2019) : 06006. http://dx.doi.org/10.1051/epjconf/201920406006.

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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.
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16

Ferraz, Paulo B., Thomas W. Kephart et João G. Rosa. « Superradiant pion clouds around primordial black holes ». Journal of Cosmology and Astroparticle Physics 2022, no 07 (1 juillet 2022) : 026. http://dx.doi.org/10.1088/1475-7516/2022/07/026.

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Abstract We show that highly spinning primordial black holes of mass M ∼ 1012 kg, potentially born in a matter-dominated era after inflation, can produce clouds of pions in their vicinity via the superradiant instability, with densities up to that of nuclear matter. We discuss the electromagnetic signatures of this process, via neutral pion decay and charged pion annihilation into photons, computing in particular their contribution to the isotropic gamma-ray background. This allows us to place upper bounds on the abundance of such primordial black holes that are comparable to the ones obtained from Hawking evaporation. We also discuss the possibility of directly observing such clouds in high-redshift superclusters.
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Trinhammer, Ole L., Henrik G. Bohr et Mogens Stibius Jensen. « The Higgs mass derived from the U(3) Lie group ». International Journal of Modern Physics A 30, no 14 (14 mai 2015) : 1550078. http://dx.doi.org/10.1142/s0217751x15500785.

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The Higgs mass value is derived from a Hamiltonian on the Lie group U(3) where we relate strong and electroweak energy scales. The baryon states of nucleon and delta resonances originate in specific Bloch wave degrees of freedom coupled to a Higgs mechanism which also gives rise to the usual gauge boson masses. The derived Higgs mass is around 125 GeV. From the same Hamiltonian, we derive the relative neutron to proton mass ratio and the N and Delta mass spectra. All compare rather well with the experimental values. We predict scarce neutral flavor baryon singlets that should be visible in scattering cross-sections for negative pions on protons, in photoproduction on neutrons, in neutron diffraction dissociation experiments and in invariant mass spectra of protons and negative pions in B-decays. The fundamental predictions are based on just one length scale and the fine structure constant. More particular predictions rely also on the weak mixing angle and the up–down quark flavor mixing matrix element. With differential forms on the measure-scaled wave function, we could generate approximate parton distribution functions for the u and d valence quarks of the proton that compare well with established experimental analysis.
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18

Naderi Beni, A., J. Esmaili et M. Mohseni. « Signature of Λ(1405) resonance in K− +6Li reaction ». International Journal of Modern Physics E 28, no 01n02 (février 2019) : 1950003. http://dx.doi.org/10.1142/s0218301319500034.

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We investigate whether the mass and momentum spectra of emitted particles in [Formula: see text] reaction can be used for disentangling the nature of [Formula: see text](1405) and how the signature of the [Formula: see text](1405) resonance appears in the cross-sections of the kaon-lithium reaction on the physical real energy. We used different types of [Formula: see text] potentials to study the dependence of the results to the fundamental kaon-nucleon interaction. The momentum spectra are calculated for final pions and neutrons. The possibility of the observation of the [Formula: see text](1405) resonance in the mass spectra is studied. It was demonstrated that the [Formula: see text] mass and neutron momentum spectra are more suitable than the pion momentum spectra to see the trace of the [Formula: see text](1405) resonance and it is a useful tool for investigating the subthreshold behavior of the [Formula: see text] interaction.
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19

Letizia, Peruzzo. « Search for heavy neutrinos at the NA48/2 and NA62 experiments at CERN ». EPJ Web of Conferences 182 (2018) : 02095. http://dx.doi.org/10.1051/epjconf/201818202095.

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The NA48/2 experiment at CERN has collected large samples of charged kaons decaying into a pion and two muons for the search of heavy nuetrinos. In addition, its successor NA62 has set new limits on the rate of charged kaon decay into a heavy neutral lepton (HNL) and a lepton, with l = e; μ, using the data collected in 2007 and 2015. New limits on heavy neutrinos from kaon decays into pions, muons and positrons are presented in this report.
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Bulychev, S. A., A. E. Kudryavtsev, V. V. Kulikov, M. A. Martem’yanov, V. E. Tarasov, W. J. Briscoe et I. I. Strakovsky. « Neutral Pion Photoproduction on Neutron ». Physics of Atomic Nuclei 80, no 9 (décembre 2017) : 1549–52. http://dx.doi.org/10.1134/s1063778817090022.

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21

Zhang, Jingbo, et Nader Mobed. « Threshold pion photoproduction in the Skyrme model ». Canadian Journal of Physics 70, no 9 (1 septembre 1992) : 711–18. http://dx.doi.org/10.1139/p92-114.

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Threshold photoproduction of pions on the nucleon is studied in the Skyrme model. Both the rotational and translational degrees of freedom of the Skyrmion are included in the calculations. It is found that in the case of neutral pion production there is a sizeable cancellation between the nucleon pole term and the anomalous contact term. This cancellation is a unique feature of the model and provides an important test of the validity of the model. A definitive conclusion must await a resolution of the existing controversies about the experimental data.
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Smolyanskiy, P., M. Bacak, B. Bergmann, P. Broulím, P. Burian, T. Čelko, D. Garvey et al. « A two-layer Timepix3 stack for improved charged particle tracking and radiation field decomposition ». Journal of Instrumentation 19, no 02 (1 février 2024) : C02016. http://dx.doi.org/10.1088/1748-0221/19/02/c02016.

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Abstract We characterize a novel instrument designed for radiation field decomposition and particle trajectory reconstruction for application in harsh radiation environments. The device consists of two Timepix3 assemblies with 500 µm thick silicon sensors in a face-to-face geometry. These detectors are interleaved with a set of neutron converters: 6LiF for thermal neutrons, polyethylene (PE) for fast neutrons above 1 MeV, and PE with an additional aluminum recoil proton filter for neutrons above ∼4 MeV. Application of the coincidence and anticoincidence technique together with pattern recognition allows improved separation of charged and neutral particles, their discrimination against γ-rays and assessment of the overall directionality of the fast neutron field. The instrument's charged particle tracking and separation capabilities were studied at the Danish Center for Particle Therapy (DCPT), the Proton Synchrotron, and Super Proton Synchrotron with protons (50–240 MeV), pions (1–10 GeV/c and 180 GeV/c). After developing temporal and spatial coincidence assignment methodology, we determine the relative amount of coincident detections as a function of the impact angle, present the device's impact angle resolving power (both in coincidence and anticoicidence channels). The detector response to neutrons was studied at the Czech Metrology Institute (CMI), at n_ToF and the Los Alamos Neutron Science Center (LANSCE), covering the entire spectrum from thermal up to 600 MeV. The measured tracks were assigned to their corresponding neutron energy by application of the time of flight technique. We present the achieved neutron detection efficiency as a function of neutron kinetic energy and demonstrate how the ratio of events found below the different converters can be used to assess the hardness of the neutron spectrum. As an application, we determine the neutron content within a PMMA phantom just behind the Bragg-peak during clinical irradiation condition with protons of 160 MeV.
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Klevansky, S. P. « Neutral-pion photodecay and weak decays of charged pions at finite temperature ». Nuclear Physics A 575, no 4 (août 1994) : 605–22. http://dx.doi.org/10.1016/0375-9474(94)90159-7.

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Bulychjov, S. A., A. E. Kudryavtsev, V. V. Kulikov, M. A. Martemianov, V. E. Tarasov, M. A. Lizunova, W. J. Briscoe et I. I. Strakovsky. « Neutron Detection in the A2 Collaboration Experiment on Neutral Pion Photo-production on Neutron ». KnE Energy 3, no 1 (9 avril 2018) : 51. http://dx.doi.org/10.18502/ken.v3i1.1722.

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Neutron detection is of crucial importance for the neutral pion photo-production study on a neutron target that now is in progress at MAMI. Two electro-magnetic calorimeters, based on NaI and BaF2 crystals, are used in the A2 experiment. While these calorimeters are optimized for pion decay photon detection, they have a reason able efficiency for neutron detection also. The paper describes the method, which has been used to measure this efficiency using the same data taken for pion photo-production study on deuterium target with tagged photon been of 800 MeV maximal energy. The detection efficiency is a rising function of neutron momentum that reaches 40% near 1 GeV/c.
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Dey, Rajat K., et Animesh Basak. « Behaviour of the lateral shower age of cosmic ray extensive air showers ». Journal of Physics : Conference Series 2156, no 1 (1 décembre 2021) : 012174. http://dx.doi.org/10.1088/1742-6596/2156/1/012174.

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Abstract Some simple arguments are introduced for a possible explanation of the behavior of the lateral shower age of proton-initiated showers. The corresponding analytical treatment based on the proposed argument is then illustrated. Using the Monte Carlo simulation (MC) code CORSIKA, we have validated how the different characteristics associated with the lateral shower age predicted in the present analytical parametrization, can be understood. The lateral shower age of a proton-initiated shower and its correlations with the lateral shower ages of electron- and neutral pion-initiated showers supports the idea that the result of superposition of several electromagnetic sub-showers initiated by neutral pions might produce the lateral density distribution of electrons of a proton initiated shower. It is also noticed with the simulated data that the stated feature still persists even in the local shower age representation.
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Lu, Zhun, et Wenjuan Mao. « Single-Spin Asymmetries AULsinϕh in Semi-Inclusive Pions Production ». International Journal of Modern Physics : Conference Series 40 (janvier 2016) : 1660045. http://dx.doi.org/10.1142/s2010194516600454.

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The single-spin asymmetry [Formula: see text] of charged and neutral pion production in semi-inclusive deep-inelastic scattering on longitudinally polarized nucleon targets is studied. We particularly consider the effects of the twist-3 transverse-momentum dependent distribution functions [Formula: see text] and [Formula: see text], which are calculated in two different spectator-diquark models. We estimate the asymmetry for [Formula: see text], [Formula: see text] and [Formula: see text] produced off the proton target at HERMES and compare the results with the HERMES measurements. We also predict the same asymmetric moment for different pions at the kinematics of CLAS 5.5 GeV on a proton target, as well as at COMPASS on a deuteron target for comparison.
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Duffy, K. E., A. P. Furmanski, E. Gramellini, O. Palamara, M. Soderberg et T. Yang. « Neutrino interaction measurements with the MicroBooNE and ArgoNeuT liquid argon time projection chambers ». European Physical Journal Special Topics 230, no 24 (décembre 2021) : 4275–91. http://dx.doi.org/10.1140/epjs/s11734-021-00297-5.

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AbstractPrecise modeling of neutrino interactions on argon is crucial for the success of future experiments such as the Deep Underground Neutrino Experiment (DUNE) and the Short-Baseline Neutrino (SBN) program, which will use liquid argon time projection chamber (LArTPC) technology. Argon is a large nucleus, and nuclear effects—both on the initial and final-state particles in the interaction—are expected to be large in neutrino–argon interactions. Therefore, measurements of neutrino scattering cross sections on argon will be of particular importance to future DUNE and SBN oscillation measurements. This article presents a review of neutrino–argon interaction measurements from the MicroBooNE and ArgoNeuT collaborations, using two LArTPC detectors that have collected data in the NuMI and Booster Neutrino Beams at Fermilab. Measurements are presented of charged-current muon neutrino scattering in the inclusive channel, the ‘0$$\pi $$ π ’ channel (in which no pions but some number of protons may be produced), and single pion production (including production of both charged and neutral pions). Measurements of electron neutrino scattering are presented in the form of $$\nu _e+\bar{\nu }_e$$ ν e + ν ¯ e inclusive scattering cross sections.
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Chadeeva, M., et S. Korpachev. « Machine-learning-based prediction of parameters of secondaries in hadronic showers using calorimetric observables ». Journal of Instrumentation 17, no 10 (1 octobre 2022) : P10031. http://dx.doi.org/10.1088/1748-0221/17/10/p10031.

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Abstract The paper describes a novel neural-network-based approach to study the distributions of secondaries produced in hadronic showers using observables provided by highly granular calorimeters. The response is analysed of the highly granular scintillator-steel hadron calorimeter to negative pions with momenta from 10 to 80 GeV simulated with two physics lists from the Geant4 package version 10.3. Several global observables, which characterise different aspects of hadronic shower development, are used as inputs for a deep neural network. The network regression model is trained using a supervised learning and exploiting true information from the simulations. The trained model is applied to predict a number of neutrons and energy of neutral pions produced within a hadronic shower. The achieved performance and possible application of the model to validation of simulations are discussed.
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Lehmann, Eberhard, Knud Thomsen, Markus Strobl, Pavel Trtik, Johannes Bertsch et Yong Dai. « NEURAP—A Dedicated Neutron-Imaging Facility for Highly Radioactive Samples ». Journal of Imaging 7, no 3 (16 mars 2021) : 57. http://dx.doi.org/10.3390/jimaging7030057.

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NEURAP is a dedicated set-up at the Swiss neutron spallation source (SINQ) at the Paul Scherrer Institut (PSI), optionally implemented as a special configuration of the neutron-imaging station NEUTRA. It is one of very few instrumentations available worldwide enabling neutron-imaging of highly radioactive samples to be performed routinely, with special precautions and following a specific procedure. Since the relevant objects are strong γ-sources, dedicated techniques are needed to handle the samples and to perform neutron-imaging despite the radiation background. Dysprosium (Dy)-loaded imaging plates, effectively made sensitive to neutrons only, are employed. Neutrons are captured by Dy during neutron irradiation. Then the imaging plate is erased removing gamma detections. A subsequent relatively long self-exposure by the radiation from the intrinsic neutron-activated Dy within the imaging plate yields the neutron-only radiograph that is finally read out. During more than 20 years of NEURAP operation, images have been obtained for two major applications: (a) highly radioactive SINQ target components were investigated after long-term operation life; and (b) spent fuel rods and their cladding from Swiss nuclear power plants were characterized. Quantitative analysis of the image data demonstrated the accumulation of spallation products in the lead filled “Cannelloni” Zircaloy tubes of the SINQ target and the aggregation of hydrogen at specific sites in used fuel pins of power plants and their cladding, respectively. These results continue to help understanding material degradation and optimizing the operational regimes, which might lead to extending the safe lifetimes of these components.
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PERKINS, W. A. « EVIDENCE FOR TWO NEUTRAL PIONS ». International Journal of Modern Physics A 16, supp01c (septembre 2001) : 919–21. http://dx.doi.org/10.1142/s0217751x01008497.

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Experimental results from π-, K-, Σ- capture, [Formula: see text] and [Formula: see text] annihilations in liquid H2 show that the fraction of captures and annihilations from atomic P states is less than 5% in agreement with theoretical expectations. However, an anomalously large fraction from P states by a factor of ten is inferred from the branching ratios for the reactions [Formula: see text] and [Formula: see text] at rest in liquid H2 and liquid D2 respectively. One explanation for this inconsistenct is that the reaction [Formula: see text] is occurring from an atomic S state of protnium, which is possible if the two π0's are not identical. It should be noted that a second neutral pion (with different lifetime and decay properties) was observed in antinucleon-nucleon reactions in a 1964 experiment. We describe two experimental tests, one to determine whether [Formula: see text] can occur from an atomic S state, and another to search for the π0π0 decay mode of neutral vector mesons with JPC = 1--.
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TABACHENKO, A. N. « NEUTRAL PION PHOTOPRODUCTION ON THE PROTON AND THE CLOUDY-BAG MODEL ». International Journal of Modern Physics A 07, no 21 (20 août 1992) : 5231–44. http://dx.doi.org/10.1142/s0217751x92002398.

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In the cloudy-bag model, the value of the electric dipole amplitude of the photoproduction of neutral pions off protons at threshold connected with the additional contribution from the chiral symmetry breaking interaction is evaluated. If this additional contribution is included in the amplitude of the photoproduction of neutral pions off protons at threshold, the discrepancy between the LET predictions and the measured value of the electric dipole amplitude [Formula: see text] can be resolved for the values of quark masses and bag radii which are close to the generally used values.
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32

Heiselberg, Henning, et Vijay Pandharipande. « Recent Progress in Neutron Star Theory ». Annual Review of Nuclear and Particle Science 50, no 1 (décembre 2000) : 481–524. http://dx.doi.org/10.1146/annurev.nucl.50.1.481.

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▪ Abstract We review recent progress in the theory of neutron stars and compare its predictions with the observational data on masses, radii, and temperatures. The theory of neutron stars made up of neutrons, protons, and leptons is discussed in detail along with recent models of nuclear forces and modern many-body techniques. The possibilities of pion and kaon condensation in dense neutron star matter are considered, as is the possible occurrence of strange hyperons and quark-matter drops in the stellar core. The structure of mixed-phase matter in neutron stars, as well as the probable effect of phase transitions on the spin down of pulsars, is also discussed.
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Takumi, Muto, et Tatsumi Toshitaka. « On the Existence of Combined Condensation of Neutral and Charged Pions in Neutron Matter ». Progress of Theoretical Physics 78, no 6 (1 décembre 1987) : 1405–27. http://dx.doi.org/10.1143/ptp.78.1405.

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ROBSON, B. A. « PARITY OF NEUTRAL PION ». International Journal of Modern Physics E 20, no 09 (septembre 2011) : 1961–65. http://dx.doi.org/10.1142/s0218301311019672.

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The paper discusses the parity of the neutral pion. It is shown that the recent determination of the parity of the neutral pion using the double Dalitz decay π0→e+e-e+e- is compatible with the mixed-parity nature of the neutral pion predicted by a recent composite model.
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35

Michaličková, Katarína, S. V. Afanasiev, D. K. Dryablov et S. Vokál. « η-nuclei in the SCAN experiment ». EPJ Web of Conferences 204 (2019) : 09001. http://dx.doi.org/10.1051/epjconf/201920409001.

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η-mesic nucleus or the quasibound nuclear state of an η-meson in a nucleus is caused by the strong-interaction force alone. The project SCAN2 is aimed at searching and studying the η-meson nuclei production. The experiment is based on two-arms spectrometer using internal target at the Nuclotron. The setup was designed to study products from η-meson nucleus decay in the reaction d + 12C → (A)η + X → π + p + (A – 2) at deuteron energies from 0:5 to 2:5 GeV/nucl. The energy spectrum of secondary protons has been measured. The dependence of the yields of protons and pions on the beam energy has been obtained. This dependence can show us the minimum energy for the S 11 resonance formation. The first prototype of the neutron detector, which will be used in a new modified experimental setup SCAN3 for recording of neutrons from η-nucleus decays in the πn and pn channels, has been tested. The time-offlight method to obtain the neutron spectrum was used. The time resolution and efficiency of the neutron detector have been obtained.
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36

Anselm, A. A., et M. G. Ryskin. « The production of a non-homogeneous classical pion field and the distribution of the neutral and charged pions ». Zeitschrift für Physik A Hadrons and Nuclei 358, no 3 (septembre 1997) : 353–55. http://dx.doi.org/10.1007/s002180050338.

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Kurt, Viktoria, Karel Kudela, Boris Yushkov et Vladimir Galkin. « On the Onset Time of Several SPE/GLE Events : Indications from High-Energy Gamma-Ray and Neutron Measurements by CORONAS-F ». Advances in Astronomy 2013 (2013) : 1–15. http://dx.doi.org/10.1155/2013/690921.

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We analyzed the high-energy gamma and neutron emissions observed by the SONG instrument onboard the CORONAS-F satellite during August 25, 2001, October 28, 2003, November 4, 2003, and January 20, 2005 solar flares. These flares produced neutrons and/or protons recorded near Earth. The SONG response was consistent with detection of the pion-decay gamma emission and neutrons in these events. We supposed that a time profile of the soft X-ray derivative was a good proxy of time behavior of the flare energy release. Then we showed that time intervals of the maximum both of energy release and pion-decay-emission coincided well. We determined the onset time of GLEs 65, 69 on the basis of neutron monitor data using the superposed epoch method. The time of high-energy proton onset on November 4, 2003 was found from the GOES data. The time delay between the high-energy gamma ray observation and the high-energy protons onset time was <5 minutes. This time lag corresponds to the least possible proton propagation time. So, we conclude that in these events both protons interacted in the solar atmosphere and the first protons which arrived to Earth, belonged to one and the same population of the accelerated particles.
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38

Muto, T., et T. Tatsumi. « Extra Neutrino Emissivity of Neutron Stars under the Combined Condensation of Neutral and Charged Pions ». Progress of Theoretical Physics 79, no 2 (1 janvier 1988) : 461–79. http://dx.doi.org/10.1143/ptp.79.461.

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Kumano, S. « Spin Physics at J-PARC ». International Journal of Modern Physics : Conference Series 40 (janvier 2016) : 1660009. http://dx.doi.org/10.1142/s2010194516600090.

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Spin-physics projects at J-PARC are explained by including future possibilities. J-PARC is the most-intense hadron-beam facility in the high-energy region above multi-GeV, and spin physics will be investigated by using secondary beams of kaons, pions, neutrinos, muons, and antiproton as well as the primary-beam proton. In particle physics, spin topics are on muon [Formula: see text], muon and neutron electric dipole moments, and time-reversal violation experiment in a kaon decay. Here, we focus more on hadron-spin physics as for future projects. For example, generalized parton distributions (GPDs) could be investigated by using pion and proton beams, whereas they are studied by the virtual Compton scattering at lepton facilities. The GPDs are key quantities for determining the three-dimensional picture of hadrons and for finding the origin of the nucleon spin including partonic orbital-angular-momentum contributions. In addition, polarized parton distributions and various hadron spin topics should be possible by using the high-momentum beamline. The strangeness contribution to the nucleon spin could be also investigated in principle with the neutrino beam with a near detector facility.
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PANDA, P. K., J. DA PROVIDÊNCIA et S. SARANGI. « PION CORRELATIONS IN NUCLEAR MATTER ». International Journal of Modern Physics E 20, no 01 (janvier 2011) : 63–80. http://dx.doi.org/10.1142/s0218301311017338.

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The saturation properties of the nuclear matter taking pion correlations into account are studied. We construct a Bogoliubov transformation for the pion pair operators and calculate the energy associated with the pion pairs. The pion dispersion relation is investigated. The correlation energy due to one-pion exchange in nuclear matter and neutron matter at random phase approximation using the generator coordinate method is also studied. The techniques of the charged pion correlations are discussed in the neutron matter calculations. We observe that there is no sign of the pion condensation in this model.
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BRISCOE, W. J., R. A. ARNDT, I. I. STRAKOVSKY et R. L. WORKMAN. « RESULTS FROM THE ANALYSIS OF CRYSTAL BALL MESON PRODUCTION MEASUREMENTS AT BNL ». International Journal of Modern Physics A 22, no 02n03 (30 janvier 2007) : 349–56. http://dx.doi.org/10.1142/s0217751x07035525.

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The Crystal Ball spectrometer, with its nearly complete angular coverage, is an efficient detector of photon and neutron final states. While installed in the C6 beamline of the Alternating Gradient Synchrotron (AGS) of Brookhaven National Laboratory (BNL), this feature was used in a series of precise measurements of reactions with all-neutral final states. Here we concentrate on the analysis of data from the pion-induced reactions: π-p → γn, π0n, ηn, and π0π0n.
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Miskimen, R. « Neutral Pion Decay ». Annual Review of Nuclear and Particle Science 61, no 1 (23 novembre 2011) : 1–21. http://dx.doi.org/10.1146/annurev-nucl-102010-130426.

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van den Brink, H. B., H. P. Blok, I. Bobeldijk, G. E. Dodge, C. W. de Jager, W. J. Kasdorp, T. J. Ketel et al. « Electroproduction of neutral pions on the proton ». Nuclear Physics A 612, no 3-4 (janvier 1997) : 391–417. http://dx.doi.org/10.1016/s0375-9474(96)00397-1.

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Pokrovskiy, N. S. « TO THE QUESTION OF THE EXISTENCE OF CENTAURS - EVENTS IN COSMIC RAYS ». PHYSICO-MATHEMATICAL SERIES 5, no 333 (15 octobre 2020) : 113–18. http://dx.doi.org/10.32014/2020.2518-1726.90.

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One of the first exotic phenomena observed in the 80s of the last century was an event registered by a calorimetric type installation. In this event, an anomalous relationship was observed between charged and neutral hadrons, arising from the collision of a high-energy particle with a carbon nucleus. In accordance with the principle of isotopic invariance, the number of neutral pions should be equal to the number of charged pions. The event, which was recorded by Japanese physicists, contained only charged peonies with no neutral [1]. This event was named "Centaur". Until now, such events have not been observed in accelerator experiments. The article presents the results of searching for such events in experiments at the DESY HERA collider. For the candidates for Centaur events and for all other events, constructed distributions by the type of fitability of charged tracks in CTD. Since the absence of neutral particles in events is explained by methodological reasons, "Centaur" events were not detected in electron-proton interactions at the ZEUS facility.
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Liu, Lei, Nikolaos Vassilopoulos, Yu Bao, Gang Zhang, Cong Chen, Zhixin Tan et Ning He. « Target Design of MELODY ». Journal of Physics : Conference Series 2462, no 1 (1 mars 2023) : 012020. http://dx.doi.org/10.1088/1742-6596/2462/1/012020.

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Abstract The Muon station for sciEnce, technoLOgy and inDustrY (MELODY) is foreseen to be the first muon source in China and to be located at the China Spallation Neutron Source in Dongguan. The stand-alone target station has been studied for the surface muons and the pions production. In this report, we aim to describe the design of the target station, including the mechanical design, the radiation shielding and optimization of the target in order to provide the highest rates of surface muons and pions to the capture solenoids under certain emittance selections.
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46

Krutenkova, A. P., et I. S. Tsukerman. « Inclusive pion production by pions on nuclei and determination of root-mean-square radii of proton and neutron distributions ». Physics of Atomic Nuclei 70, no 12 (décembre 2007) : 2120–30. http://dx.doi.org/10.1134/s1063778807120137.

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Muto, T., et T. Tatsumi. « On the Cooling of Neutron Stars under the Neutral Pion Condensed Phase ». Progress of Theoretical Physics 80, no 1 (1 juillet 1988) : 28–33. http://dx.doi.org/10.1143/ptp.80.28.

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Nam, J. W. « Results on Inclusive and Semileptonic B decays from Belle ». International Journal of Modern Physics A 16, supp01b (septembre 2001) : 625–27. http://dx.doi.org/10.1142/s0217751x01007637.

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We report on studies of inclusive and semileptonic B decay from Belle. The measurement of branching ratios of exclusive semileptonic B decays [Formula: see text] and inclusive B→π0X and the momentum spectrum of neutral pions are presented.
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49

Bruce, Stanley A. « Scalar electrodynamics and the decays of the neutral pion ». International Journal of Modern Physics A 36, no 05 (20 février 2021) : 2150037. http://dx.doi.org/10.1142/s0217751x21500378.

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We propose an effective model of scalar electrodynamics (SED) in which a (nonscalar) Dirac electron field is included in the general Lagrangian density. This approach is intended to predict possible electrodynamics processes with a discussion of the role of pions that might be significant in QED.
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Olimov, Khusniddin K., Kosim Olimov, K. G. Gulamov, Alisher K. Olimov, Sagdulla L. Lutpullaev, B. S. Yuldashev et Mahnaz Q. Haseeb. « Partial inelasticity coefficients of negative pions in p, d, α, 12C+12C and p, 12C+181Ta collisions at 4.2 GeV/c per nucleon ». International Journal of Modern Physics E 24, no 10 (octobre 2015) : 1550070. http://dx.doi.org/10.1142/s0218301315500706.

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The partial inelasticity coefficients of the negative pions were determined in minimum bias p, d, α, 12 C +12 C and p, 12 C +18 Ta collisions at 4.2A GeV/c taking into account the average number of participant nucleons of a projectile nucleus. In nucleus–nucleus collisions, the average values of partial inelasticity coefficients (〈K(π-)〉) of the negative pions did not depend on the mass numbers of projectile and target nuclei. Increase of 〈K(π-)〉 in going from p+12 C to d, α, 12 C +12 C collisions was due to an additional source of production of fast negative pions in nucleus–nucleus collisions — a charge exchange conversion of one or more neutrons of a projectile nucleus into a proton and π-. Linking the experimental results of the present analysis at intermediate energy with those obtained at high and ultra-high energies, it was concluded that the average values of partial inelasticity coefficients of pions in nucleon–nucleus and nucleus–nucleus collisions manifest a transitive behavior. At intermediate energies, the values of 〈K(π-)〉 were smaller by a factor of two and more as compared to those at high energies, and they increased further with increasing incident energy, reaching a plateau at E0 > 100A GeV.
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