共查询到20条相似文献,搜索用时 234 毫秒
1.
S. R. Gevorkyan 《Physics of Atomic Nuclei》2013,76(8):1004-1009
The isospin symmetry breaking effects in the charged kaons decays to two or three pions are considered. In semileptonic decay K ± → π + π ?e± ν (called K e4) these effects turn out to be crucial for correct extraction of ππ scattering lengths. Taking in account electromagnetic interaction between the pions in the final state and isospin symmetry breaking due to different masses of charged and neutral pions allows to adjust the values of scattering lengths obtained from experimental data on K e4 decay and predictions of Chiral Perturbation Theory (ChPT). Final state interactions of pions in the decay K ± → π ± π 0 π 0 leading to the anomaly (cusp) in the π 0 π 0 invariant mass distribution in the vicinity of charged pions’ threshold are discussed and recent results of accounting of the electromagnetic interaction among charged pions leading to π + π ? bound states (pioniumatom) just under the charged pions’ threshold are presented. 相似文献
2.
H. Kirk G. Rudolph U. Kriegel H. Vogt K. Böckmann H.G. Zobernig H. Bohr V.T. Cocconi M.J. Counihan P.K. Malhotra D.R.O. Morrison H. Saarikko P. Schmid D. Kisielewska K.W.J. Barnham R.M. Eason F. Mandl A. Para 《Nuclear Physics B》1977,128(3):397-407
Recent data on the production ofη, ?0, ω and other mesons in hadron-hadron collisions at intermediate energies are studied. Their transverse spectra dσ/dpT2 are all found to be approximately exponential, with similar slopes, ~3.4 (GeV/c)?2, up to about pT2 = 2(GeV/c)2. The inclusive yields of the mesons are broadly in agreement with quark model predictions. In the case of pions, a distimction is made between those directly produced and those produced indirectly via resonance decay. It is estimated that between 10% and 30% of pions are directly produced. 相似文献
3.
R.R. Whitney J. Källne J.S. McCarthy R.C. Minehart R.L. Boudrie J.F. Davis J.B. McClelland A. Stetz 《Nuclear Physics A》1983,408(3):417-424
Differential cross sections for 3, 4He(π, π') are presented for angles of 60° and 120° at 200 MeV and 120° at 295 MeV. The momentum spectra for the scattered pions are dominated by a peak attributed to quasi-free scattering from individual nucleons. There are significant differences between the scattering on 3He and 4He as well as between the scattering of π+ and π? on 3He. The data are compared to a simple model incorporating the free π+N scattering amplitudes. Modifications for the structure and dynamics of the target nucleus are discussed. 相似文献
4.
M. Deutschmann R. Honecker H. Kirk M. Klein R. Nahnhauer R. Hartmann H. Plothow V.T. Cocconi M.J. Counihan S. Humble G. Kellner D.R.O. Morrison P. Schmid R. Stroynowski L. Aniola T. Coghen K. Dziunikowska A.K. Wroblewski 《Nuclear Physics B》1976,103(2):198-212
Positive correlations are observed for pion pairs of equal charge and similar momentum vectors, produced in the reactions πp→p+5π and πp→p + 7π at 4 to 25 GeV/c. The results are consistent with being due to the second-order interference effects expected for pairs of identical bosons and lead to the determination of the average dimension of the “fire-ball’ from which the pions are emitted (〈R〉 = 1.0 ± ?0.2+0.4 fm). Attempts are made to study the fire-ball shape by selecting pions pair emitted in various polar and azimuthal directions. 相似文献
5.
D. Gotta M. Dörr W. Fetscher G. Schmidt H. Ullrich G. Backenstoss W. Kowald I. Schwanner H.-J. Weyer 《Physics letters. [Part B]》1982,112(2):129-132
The reactions π?3He → nnp and π?3He → nd have been measured in a kinematically complete experiment with stopped pions. The results show strong preference for collinear events. About three quarters of all absorption processes occur as quasi-free absorption on np- or pp-pairs with a ratio of R = 10.1 ± 1.5. The remaining quarter shows energy sharing among all three nucleons and is located in the final-state interaction regions. Branching ratios for all observed final states are given. 相似文献
6.
《Physics letters. [Part B]》1987,199(1):9-12
Data for the elastic scattering of 30–80 MeV positive and negative pions by a wide range of nuclei is analysed with an Ericson-Ericson MSU type optical potential. By use of consistent sets of data for π+ and π− and of experimental results for total reaction cross sections we obtain for the first time optical potentials that describe well all the data without the need of introducing non-standard charge-dependent effects. 相似文献
7.
The spectra of pions are studied in the inclusive reactions p + p → π± + anything in bubble chamber data at 28.5 GeV/c. Comparisons are made with ISR π+ spectra to examine energy dependence. 相似文献
8.
The elastic scattering of pions from3He and the single charge exchange reaction3He(π ?,π 0)3H are calculated in the energy domain of the (3,3)-resonance within the framework of Glauber's theory, including spin and isospin degrees of freedom in all orders. It is pointed out that, from the first minimum on, the differential cross section strongly depends on the parametrization of theπN amplitude, especially on its continuation into the unphysical region of momentum transfer. Single and double spin flip contributions prove to be very important in the charge exchange reaction. Within a modified version of Glauber's formalism, directly usingπN phase shifts rather than amplitudes, the3He charge exchange scattering is reexamined. Whereas the shape of the angle-integrated cross section as a function of pion energy is confirmed, the magnitude is still uncertain within a factor of 2. 相似文献
9.
《Nuclear Physics A》1997,625(4):873-892
We develop the formalism for coherent two pion photoproduction in nuclei and perform actual calculations of cross sections for π−π+ and π0π0 photoproduction on 12C. We find that due to the isospin symmetry the cross section for π0π0 production is very small and has a maximum when the pions propagate together. However, the kinematical region where the energies and polar angles of the two π0 mesons are equal and their relative azimuthal angle Ø = 180° is forbidden. Conversely in the π−π+ production the pions prefer to have a relative azimuthal angle 180° and the production of the pions propagating together is suppressed. The dominant one-body mechanism in both channels is related to the excitation of the Δ isobar. Hence the reaction can serve as a source of information about Δ's properties in nucleus. We have found that the reaction is sensitive to effects of the pion and Δ renormalization in the nuclear medium, similar to those found in the coherent (γ, π0) reaction, but magnified because of the presence of the two pions. 相似文献
10.
The reaction channel (π?, NN) for the absorption of bound negative pions by nuclei is used as a means to study nuclear short range correlations. A three-body partial-wave analysis has been carried out for the final-state scattering which includes a Reid soft-core nucleon-nucleon interaction and an optical potential. This coupled-channel formalism rapidly converges as we eliminate the asymptotic single-nucleon and deuteron interactions. It is found that for 12C reasonable agreement with experiment cannot be obtained in this model without modification of the high relative-momentum components of bound shell model pair wave functions. 相似文献
11.
In an investigation ofT=7/2 analogue states in51V the50Ti(p, γ) excitation curve has been measured for proton bombarding energies 1280–1480 keV and 2340–2660 keV. From the (p, γ) resonances 29 new virtual levels in the region of 9316–9510 keV excitation energy in51V were determined. The strong resonance atE p=1 371 keV has been identified as the isobaric analogue state of the51Ti ground state by determining spin and parity of this resonance to be 3/2?. There is no evidence for a strong analogue resonance in51V corresponding to the 1.16 MeV p 1/2 state in51Ti. The γ-decay of the p 3/2 analogue state has been studied by measuring branching ratios and angular distributions of primary γ-transitions with a Ge(Li) detector.M1E2 mixing ratios have been determined for these transitions. The total width of the resonance for γ-decay is found to be Γγ=1.6±0.4 eV. New bound levels in51V have been introduced at 3576, 4651 and 4661 keV excitation energy. TheJ π values of the 3085, 4770, and 4863 keV states are determined to be 5/2?, 5/2?, 3/2?, respectively. The analogue-antianalogueM1 transition strength is found to be considerably reduced compared to the situation ins-d shell nuclei. 相似文献
12.
In the framework of the Coleman-Glashow hypothesis of an extremely weak violation of Lorentz invariance, neutral and charged pions can be stable for energies above 1019 eV and enter into the composition of primary cosmic rays of ultrahigh energies. The kinematic exclusion of reactions of pions with relic photons is particularly important, because it allows the Greisen-Zatsepin-Kuzmin paradox to be resolved. The parameters of extensive air showers induced by primary pions calculated within the model of quark-gluon strings with allowance for the Landau-Pomeranchuk-Migdal effect and interactions of neutral pions of ultrahigh energies are not contradictory to the available data of observations. It has been shown that observations of production heights of muons with energies above 10GeV will make it possible to distinguish between primary nuclei, protons, and pions; to verify Lorentz invariance for energies above 1020 eV; and to obtain a new limit on the difference between the maximum possible velocities of muons and pions (cµ?cπ)<4×10?26. 相似文献
13.
14.
Er3+ doped boro-tellurite glasses have been prepared by the conventional melt quenching technique with the chemical composition (39?x) B2O3+30TeO2+15MgO+15K2O+xEr2O3 (where x=0.01, 0.1, 1, 2 and 3 wt%). The structural analysis of the glasses were made through XRD, FTIR spectral measurements and the optical absorption, luminescence measurements were made to analyze the optical behavior of the prepared glasses. The bonding parameters were determined from the optical absorption spectra and were found to be ionic in nature. The experimental oscillator strengths were determined from the absorption spectra have been used to determine the Judd–Ofelt parameters. The Judd?Ofelt parameters were used to explore the important radiative parameters such as transition probability (A), stimulated emission cross-section (σPE) and branching ratios (βR) of the emission transitions 2H9/2→4I15/2 and 2H11/2 and 4S3/2→4I15/2 of the trivalent erbium ions. The optical band gap energy (Eopt) values corresponding to the direct and indirect allowed transitions and the Urbach energy values of the prepared Er3+ doped boro-tellurite glasses have been calculated and discussed with similar studies. The spectroscopic behavior of the Er3+ boro-tellurite glasses have been studied by varying the trivalent erbium ion content and the results were discussed and compared with similar studies. 相似文献
15.
16.
K. Olimov V. V. Glagolev K. G. Gulamov A. Kurbanov S. L. Lutpullaev A. K. Olimov V. I. Petrov A. A. Yuldashev 《Physics of Atomic Nuclei》2014,77(3):325-329
The results obtained by studying the production of six-nucleon systems and nuclei that is accompanied by the yield of charged pions in 16Op collisions at a momentum of 3.25 GeV/c per nucleon are presented. It is shown that the correlation of the yield of mirror 3H (3He) nuclei with the production of π + (π ?) mesons is due to the charge-exchange process involving an oxygen-nucleus proton (neutron) knocked out predominantly from an alpha-particle cluster. 相似文献
17.
N. Akhababian N. Angelov V. G. Grishin M. Kowalski 《Zeitschrift fur Physik C Particles and Fields》1983,18(2):97-100
The interference of positive and negative pions produced in π? p interactions at 40 GeV/c is studied. It is shown that negative pions are emitted from larger distance than positive ones. The influence of resonance production on the size of pion emission volume is observed. 相似文献
18.
J. Amirzadeh R.E. Ansorge M. Baubillier I.J. Bloodworth G.J. Bossen A. Burns J.N. Carney J.R. Carter C.A. Cowan G.F. Cox U. Dore Ph. Gavillet J.K. Hassall J.B. Kinson K. Knudson F. Levy P.F. Loverre R. Zitoun 《Physics letters. [Part B]》1979,89(1):125-130
We present evidence for a narrow Y1 with a mass of 3.17 GeV and a width ? 20 MeV decaying to ΣKK? + pions, ΛKK? + pions and ΞK + pions. The data come from two high statistics K?p bubble chamber experiments with a sensitivity of ≈100 eV/μbat 8.25 GeV/c and ≈ 45 eV/μbat 6.5 GeV/c. 相似文献
19.
S. Teis W. Cassing M. Effenberger A. Hombach U. Mosel Gy. Wolf 《Zeitschrift für Physik A Hadrons and Nuclei》1997,359(3):297-304
We study the dynamics of charged pions in the nuclear medium via the ratio of differential π? - and π+-spectra in a coupled-channel BUU (CBUU) approach. The relative energy shift of the charged pions is found to correlate with the pion freeze-out time in nucleus-nucleus collisions as well as with the impact parameter of the heavy-ion reaction. Furthermore, the long-range Coulomb force provides valuable information on the expansion dynamics of the hot nuclear system. Detailed comparisons with experimental data for Au + Au at 1 AGeV and Ni + Ni at 2.0 AGeV are presented. 相似文献
20.
Yu. B. Gurov K. N. Kovalev L. Yu. Korotkova S. V. Lapushkin R. V. Pritula V. G. Sandukovsky B. A. Chernyshev 《Bulletin of the Russian Academy of Sciences: Physics》2014,78(5):355-357
Correlation measurements of the reaction of stopped pion absorption 11B(π?, tt)X are made with a semiconductor double-arm charged particle spectrometer on a low-energy pion beam at the LAMPF meson factory. Analysis of a two-dimensional Dalitz plot and the momentum distribution of the residual nucleus allows us to identify the absorption of pions in a 6Li intranuclear cluster and demonstrate the configuration 6Li + 5Heg.s is present in the 11B nucleus. 相似文献