共查询到20条相似文献,搜索用时 15 毫秒
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A model is explored in which the fragmentation region is populated by the hadronization of a string which stretches from a fast forward quark to a quark in the backward hemisphere of the p collision. This model is a part of more complicated models which have been studied elsewhere. It successfully fits observed inclusive production of 0-mesons, 0-mesons and -mesons, and agrees with the result that their production in p collisions is harder than in electron-position annihilation if: (a) the forward quark has an initial momentum which is at least 0·9 of that of the 0-mesons (b) gluon radiation is weaker than in electron-positron annihilation. 相似文献
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M. Anikina L. Chkhaidze T. Djobava V. Garsevanishvili L. Kharkhelauri 《The European Physical Journal A - Hadrons and Nuclei》2000,7(1):139-145
The light front analysis of π− mesons in He(Li,C), C-Ne, C-Cu and O-Pb collisions is carried out. The phase space of secondary pions is divided into two
parts in one of which the thermal equilibrium assumption seems to be in a good agreement with the data. Corresponding temperatures
T are extracted and their dependence on (A
P·A
T)1/2 is studied. The results are compared with the predictions of the Quark-Gluon String Model (QGSM). The QGSM satisfactorily
reproduces the experimental data for light and intermediate-mass nuclei.
Received: 29 September 1999 相似文献
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A. B. Clegg 《Zeitschrift fur Physik C Particles and Fields》1992,55(1):135-143
The systematic features of ten reactions, in which vector mesons are produced in the meson fragmentation region in p orKp collisions, are explored. Published experimental results are compared with a model in which the vector mesons result from the fragmentation of a forward quark and a string disappearing into the central region (the detailed implementation uses the LUND JETSET generator). The cross sections for six of the reactions fit well with this model, with only two parameters, while the remaining four reactions have larger cross sections. An interpretation involves a further contribution to these latter four reactions which requires exchange of a system withI=1,G=–1, and which agrees with -meson exchange. The relation between these production processes and the results of a set of simple models is discussed. 相似文献
6.
Azimuthal distributions of final-state particles and fragments and transverse structure of emission source in high-energy nucleus-nucleus collisions
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The azimuthal distributions of final-state particles and fragments produced in high-energy nucleus--nucleus collisions are described by a modified multisource ideal gas model which contains the expansions and movements of the emission sources. The transverse structures of the sources are
given in the transverse plane by momentum components p_x and p_y,and described by parameters in the model. The results of the azimuthal distributions, calculated by the Monte Carlo method, are in good agreement with the experimental data in nucleus--nucleus collisions at high energies. 相似文献
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I. Koenig E. Berdermann F. Bosch P. Kienle W. Koenig C. Kozhuharov A. Schröter H. Tsertos 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(2):153-168
We present the results obtained from a series of +–-coincidence measurements in heavy-ion collisions using the double-Orange-spectrometer at GSI. The collision systems U+U, U+Pb, and U+Ta were investigated at bombarding energies close to and slightly above (U+Ta) the Coulomb barrier. For all systems studied, very narrow (FWHM–20 keV) +– lines were observed in the sum-energy spectra, with kinetic energies ranging from 555 keV to 810 keV, superimposed on a continuous distribution mainly due to uncorrelated +– emission. Particularly in the U+Ta system, a pronounced sum-energy line appears at 634 keV, predominantly in deep-inelastic collisions. In some cases (e.g. U+Pb) the line characteristics is consistent with a two-body decay mode of an emitter which moves with the c.m. velocity of the colliding ions. However, other lines, and in particular the 634 keV line (U+Ta), exhibit a rather isotropical opening-angle distribution whereas their energy is unequally shared between positrons and electrons, thus being in clear disagreement with this scenario. In general, the data preclude an emission from the separated (moving) nuclei, and, in the latter cases, provide evidence that the e+e–-pair decay occurs in the vicinity of the Coulomb field of a third heavy (positively charged) partner having only a small transverse velocity (|v|<>Dedicated to Prof. B. Povh on the occasion of his 60th birthday 相似文献
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Yu. M. Antipov V. A. Batarin V. A. Bessubov M. S. Bilenky N. P. Budanov D. S. Denisov O. V. Eroshin P. L. Frabetti Yu. P. Gorin Yu. A. Gornushkin V. G. Kartasheva P. A. Kulinich A. A. Nosdrin A. G. Olshevski F. Palombo A. I. Petrukhin R. V. Pirtzkhalava S. A. Polovnikov V. N. Roinishvili D. A. Stoianova A. V. Vishnevski 《Zeitschrift fur Physik C Particles and Fields》1989,42(2):185-187
In the diffraction dissociation of π? into μ+μ?π? on a Cu nucleus at 50 GeV/c, the cross section \(\sigma _{\mu ^ + \mu ^ - \pi ^ - } \) for the 1+S(ρ0π) wave was measured. The branching ratio of ρ0→μ+μ? could be calculated from the ratio of this and the corresponding cross sections in the diffraction dissociation of π? into π+π?π?. The obtained value \(BR_{\rho ^0 \to \mu ^ + \mu ^ - } = (4.6 \pm 0.2_{stat^ \pm } \pm 0.2_{syst} )10^{ - 5} \) is in good agreement with the branching ratio \(BR_{\rho ^0 \to e^ + e^ - } \) , as expected ifeμ universality holds. 相似文献
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《Physics letters. [Part B]》1986,166(1):106-110
The process of multijet production in e+e− collisions is interpreted as a critical phenomenon in the quark-gluon system formed at small distances and distributed along the hyperbolas t2 − x2 = τ2 during its space-time evolution. The appearance of colourless hadronic jets in the critical region τ ≈ τc ± Δτ is assumed to imply Kadanoff scaling in the one-dimensional system specified by the rapidity distribution of jets along the original qq̄ direction. The consequences of the model for multijet production at present and future experiments is discussed. 相似文献
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《Physics letters. [Part B]》1987,199(3):457-461
The production of the pseudoscalar meson η'(958) is observed in the reaction e+e−→ e+e−η′→e+e−π+π−γ with the ARGUS detector at DESY. We measure the product Γγγ(η')Br(η′ →ϱγ) to be 1.13±0.04±0.13 keV. Using the known branching ratio s, we calculate Γγγ(η′) to be 3.76±0.13±0.47 keV and Γη' to be 203±32 keV. 相似文献
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Experimental data on
0 meson polarization in
–
p reaction at 5 GeV/c are presented. Change in
0 meson polarization for mesons produced at smallP
2
and atP
2
0·3 or produced in backward direction in CMS is demonstrated. Natural explanation of these phenomena is one pion exchange mechanism and mechanism of quark-antiquark annihilation as observed for
0 meson production in¯pp reactions.The authors are indebted to Ján Piút, Richard Lednický, V. S. Rumiancev and N. K. Koutsidi for discussions and critical comments. 相似文献
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《Physics letters. [Part B]》1988,201(1):160-164
Significant production of G(1590), a scalar glueball candidate, is observed in a study of η pairs produced in π−N central collisions at 300 GeV/c. 相似文献
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《Physics letters. [Part B]》1988,215(2):218-222
A J/ψ meson is mainly formed by gluon fusion for 200 GeV pp collisions. In reactions with nuclei the gluons (g) scatter off other nucleons (N) before fusing to a J/ψ, which thenshows additional transverse momentum pT. Fitting the value of the parameter σgN〈p2T〉gN to describe the gluon multiple scattering effect in proton-nucleus data, we can reproduce the pT distribution of J/ψ production in 200 GeV/A nucleus-nucleus collisions. The origin of the pT distribution is traced to soft gluon radiation via the Sudakov form factor. 相似文献
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We investigate transverse hadron spectra from relativistic nucleus-nucleus collisions within two independent transport approaches that are based on quark, diquark, string, and hadronic degrees of freedom. Both transport models show their reliability for elementary pp as well as light-ion (C+C, Si+Si) reactions. However, for central Au+Au (Pb+Pb) collisions above approximately 5A GeV the measured K+/- transverse mass spectra have a larger inverse slope parameter than expected from the calculation. Thus, the pressure generated by hadronic interactions in the transport models above approximately 5A GeV is lower than observed in the experimental data. This finding shows that the additional pressure--as expected from lattice QCD calculations at finite quark chemical potential and temperature--is generated by strong partonic interactions in the early phase of central Au+Au (Pb+Pb) collisions. 相似文献
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《Journal of Quantitative Spectroscopy & Radiative Transfer》1987,38(3):209-210
The asymmetry parameter δI of the Hβ central part has been measured as a function of the plasma electron density. The results are compared with recently published theories and measurements. The plasma source was a small electromagnetic T-shaped shock tube. The electron density varied between 0.7 x 1023 and 3 x 1023m-3, while the temperatures were 20,000 K and more. 相似文献
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V. N. Zabaev V. M. Kuznetsov A. P. Potylitsin E. V. Repenko O. I. Stukov B. K. Tomchakov 《Russian Physics Journal》1978,21(5):626-632
This article presents measurements of the asymmetry of formation of + mesons on a proton by linearly polarized photons in the energy region from 220 to 320 MeV and for pion emission angles 90–135° in the c.m.s. Aphenomenological analysis is carried out on the basis of 25 measured values of the asymmetry and the data of other laboratories. As a result of the analysis, five independent values are obtained for the multipole amplitude functions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 94–101, May, 1978. 相似文献
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《Physics letters. [Part B]》1999,441(2-3):244-250
We apply Chiral perturbation theory at one loop to analyze the general formula for the π+π− atom lifetime derived recently in the framework of QCD [A. Gall et al., Phys. Lett. B 462 (1999) 335]. The corresponding analytic expression is investigated numerically, and compared with recent work in the literature. 相似文献
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Ye.S. Golubeva L.A. Kondratyuk M. Büscher W. Cassing V. Hejny H. Ströher 《The European Physical Journal A - Hadrons and Nuclei》2001,11(2):237-245
The ω resonance production and its π0γ decay in pA reactions close to threshold is considered within the Intranuclear Cascade (INC) model. The π0γ invariant-mass distribution shows two components which correspond to the ω decay “inside” and “outside” the nucleus, respectively.
The “inside” component is distorted by medium effects, which introduce a mass shift as well as collisional broadening for
the ω-meson and its decaying pion. The relative contribution of the “inside” component is analyzed in detail for different
kinematical conditions and nuclear targets. It is demonstrated that a measurement of the correlation in azimuthal angle between
the π0 and γ momenta allows to separate events related to the “inside”ω decay from different sources of background when uncorrelated
π0's and γ's are produced.
Received: 2 April 2001 / Accepted: 5 June 2001 相似文献
20.
Possible generation of π-condensation in a free space by collisions between photons and protons
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《中国物理 B》2018,(12)
A sharply peaked structure is found in the angular distribution of emitted π~+ mesons from photon–proton collisions.This offers a possible way to generate a π~+-condensation in free space. To make the stimulated emission of π~+-mesons efficient, a ring resonator is designed. 相似文献