共查询到20条相似文献,搜索用时 31 毫秒
1.
L. S. Geng E. Oset M. Döring 《The European Physical Journal A - Hadrons and Nuclei》2007,32(2):201-211
We evaluate theoretically the radiative decay widths into γΛ and γΣ
0 of the two poles of the Λ(1405) found in chiral unitary theories and we find quite different results for each of the two poles. We show that, depending
on which reaction is used to measure the Λ(1405) radiative decays, one gives more weight to one or the other pole, resulting in quite different shapes in the γΛ(Σ
0) invariant-mass distributions. Our results for the high-energy pole agree with those of the empirical determination of the
γΛ and γΣ
0 radiative widths (based on an isobar model fitting of the K-p atom data), which are sometimes referred to as “experimental data”. We have made a detailed study of the K
-
p→π
0
γΛ(Σ
0) and π
-
p→K
0
γΛ(Σ
0) reactions and have shown that they, indeed, lead to different shapes for the γΛ(Σ
0) invariant-mass distributions. 相似文献
2.
R. Rückl 《Physics letters. [Part B]》1983,120(4-6):449-454
The inclusive nonleptonic decay of the Λc+ is reanalyzed using a nonrelativistic quark model representation of the Λc+- wavefunction. It is shown that the same approximation which leads to the familiar spectator and annihilation type contributions naturally also gives interference terms as a direct consequence of Fermi statistics. Numerical estimates which include these novel contributions, are presented for the Λc+ lifetime and semileptonic branching ratio. 相似文献
3.
4.
We report a theoretical study of the pp → pK
+Λ(1405) reaction, which was recently investigated at COSY-Jülich by using a 3.65GeV/c circulating proton beam incident on an internal hydrogen target. The reaction is driven by single-kaon exchange, single-pion
exchange, and single-rho exchange terms which have very different shapes due to the two-pole structure of the Λ(1405) and
the presence of background terms. The shape for the sum of the three contributions, as well as the total cross-section, are
consistent with present data within experimental and theoretical uncertainties, using reasonable form factors for the meson-baryon
vertices. 相似文献
5.
L. G. Mann
S. D. Bloom
《Nuclear Physics A》1970,140(3):598-608β-γ(CP) correlation measurements have been carried out on the
sequence in the decay of the ground state of 49Ca to the (presumed) anti-analogue state at 3.105 MeV excitation in 49Sc. An asymmetry parameter of A = −0.132 ± 0.017 was obtained, making any spin-parity assignment other than
very unlikely for the 3.105 MeV state. The deduced Fermi matrix element for the decay is |Mv| = |1.4 ± 9.7| × 10−3, which leads to an isospin impurity (
) corresponding to the mixing of the analogue state (at 11.6 MeV) and the 3.105 MeV state of ||2 1.6 × 10−5. This leads in turn to an effective Coulomb matrix element of |Hc| = |3.9 ± 27.4| keV, a low value compared to the value of 100 keV obtained from a theoretical estimate based on simple shell-model wave functions for the
single-particle states involved. 相似文献
6.
M. Shmatikov 《Nuclear Physics A》1994,580(4):538-550
The contribution of correlated ππ-exchange to the induced Λ-hyperon cay is investigated. This mechanism is shown to give a noticeable contribution to the conversion rate from the spin-singlet state. 相似文献
7.
Larson KD Noble AJ Bassalleck B Burkhardt H Fickinger WJ Hall JR Hallin AL Hasinoff MD Horvath D Jones PG Lowe J McIntyre EK Measday DF Miller JP Roberts BL Robinson DK Sakitt M Salomon M Stanislaus S Waltham CE Warner TM Whitehouse DA Wolfe DM 《Physical review D: Particles and fields》1993,47(3):799-810
8.
《Physics letters. [Part B]》2004,590(3-4):161-169
Coherent Λπ− production on Pb of 600 GeV Σ− hyperons has been studied with the SELEX facility at Fermilab. Using the Primakoff formalism, we set a 90% CL upper limit on the radiative decay width Γ[Σ(1385)−→Σ−γ]<9.5 keV, and estimate the cross section for γΣ−→Λπ− at
GeV to be 56±16 μb. 相似文献
9.
The possibility to construct intercluster interaction potentials in continuous and discrete spectra is shown in one‐channel cluster model based on the classification of orbital states according to Young schemes. These potentials usually contain Pauli forbidden states, and correctly describe elastic scattering phase shifts taking into account resonance behavior and main characteristics of the bound states of nuclei in the considering cluster channel. The versions of intercluster interaction potentials describing the resonance nature of some phase shifts of the n7Li elastic scattering at low energies and the P2 ground state of 8Li in the n7Li cluster channel have been constructed for the demonstration of this approach. The possibility of describing the total cross sections of 7Li (n,γ)8Li within the energies from 5 meV (5 · 10‐3 eV) to 1 MeV, including resonance at 0.25 MeV, has been demonstrated for the potentials obtained in the potential cluster model with forbidden states. 相似文献
10.
JADE Collaboration W. Bartel L. Becker D. Cords R. Felst D. Haidt H. Junge G. Knies H. Krehbiel P. Laurikainen R. Meinke B. Naroska J. Olsson D. Schmidt D. Steffen 《Physics letters. [Part B]》1985,160(6):421-429
The radiative width of the η meson has been measured at PETRA in photon-photon collisions. The resulting value is Γη→γγ = 0.53±0.04±0.04 keV. 相似文献
11.
Measurements have been made of the β-γ circular-polarization correlation paramter A for the 273 keV β-branch in the decay of 59Fe. It has recently been established that each of the principal β-branches of 59Fe involves ΔJ=0 and thus has a possible non-zero Fermi matrix element MF which can be determined from the ƒt value and A. Previous β-γ (_CP) measurements on this nucleide have all employed the usual γ-ray scattering technique. This method is suitable for the 475 keV β-branch but does not produce an accurate measurement of the lower energy branch because of energy discrimination difficulties. A transmission polarimeter with γ-discrimination has been used in the present work to obtain clean data on the 273 keV β-1.29 MeV γ-cascade. Calibration with 60Co (1.33 MeV) and 28Al (1.79 MeV) yielded A = −0.154±0.023. This gives for the isospin impurity coefficient and the effective Coulomb matrix element of the 1.29 MeV state (1.1±1.4) × 10−3 and 9±11 keV, respectively. 相似文献
12.
The quark-meson coupling (QMC) model, which has been successfully used to describe the properties of both infinite nuclear matter and finite nuclei, is applied to a systematic study of Λ, Σ and Ξ hypernuclei. Assumptions made in the present study are, (i) the (self-consistent) exchanged scalar, and vector, mesons couple only to the u and d quarks, and (ii) an SU(6) valence quark model for the bound nucleons and hyperon. The model automatically leads to a very weak spin-orbit interaction for the Λ in a hypernucleus. Effects of the Pauli blocking at the quark level, particularly in the open, coupled, ΣN-ΛN chanel (strong conversion), is also taken into account in a phenomenological way. 相似文献
13.
T. Takahashi S. Ajimura K. Aoki H. Bhang T. Endo Y. Fujii O. Hashimoto H. Hotchi E. Hungerford J. H. Kim T. Kishimoto K. Koshino K. Kubota K. Maeda T. Nagae H. Noumi Y. Ohta K. Omata H. Outa H. Park T. Saito Y. Saito Y. Sato M. Sekimoto T. Shibata T. Tamagawa H. Tamura L. Tang K. Tanida M. Youn 《Nuclear Physics A》2000,670(1-4):265-268
We recently measured high-statistics and high-resolution spectra of p-shell Λ hypernuclei produced by the (π+, K+) reaction. In this article, cross sections and their angular distributions of Λ12C and Λ16O are reported. The obtained cross sections are well reproduced by DWIA calculations. 相似文献
14.
15.
We report on the final analysis of a search for the decay μ+→e+γ performed at SIN. No evidence for the existence of the process has been found. An upper limit for the branching ratio of 1.0 × 10?9 (90% confidence) is presented. The measured positron-photon energy distributions are completely described by the decay and accidental coincidences. 相似文献
16.
17.
Following the method proposed by Kozlov et al. [Victor V. Kozlov, Yuri Rostovtsev, Marlan O. Scully, Phys. Rev. A 74 (2006) 063829], we have investigated the atomic coherence induced by incoherent pump and vacuum spontaneous decay process in a Λ type three-level atomic system. The system can be in a coherent population trapping state and multi-steady states in different conditions. Interestingly, two kinds of new states are derived from the system with different pumping rate and decaying rate. They are the “robust” steady state and the “weak” steady state. Under the action of pump field and vacuum reservoir, these two kinds of states exhibit stable or unstable characteristics, respectively. Moreover, by investigating the difference between these states, we reveal the mechanism of coherence excitation and level-population transition. The special feature of the Λ atomic system will promise fruitful applications in quantum optics. 相似文献
18.
D. Gamermann E. Oset B. S. Zou 《The European Physical Journal A - Hadrons and Nuclei》2009,41(1):85-91
We calculate the radiative decay width of the (3770) into the dynamically generated scalar resonance X(3700) which is predicted in a previous paper. The results show that it is possible that the upgraded BEPC-II facility will
generate enough statistics in order to observe this decay and thus confirm the existence of the X(3700) . 相似文献
19.
Tomofumi NagaeH. Hotchi H. Outa H. Noumi M. Sekimoto T. Fukuda H. C. Bhang Y. D. Kim J. H. Kim H. Park L. I. Tang R. Sawafta K. Tanida O. Hashimoto H. Tamura T. Saito T. Takahashi Y. Sato T. Endo S. Satoh J. Nishida T. Miyoshi T. Kishimoto A. Sakaguchi S. Ajimura Y. Shimizu T. Mori S. Minami M. Sumihama 《Nuclear Physics A》2000,670(1-4):269-272
We have measured an excitation energy spectrum of a Λ-hypernucleus Λ89Y via the (π+, K+) reaction by using the SKS spectrometer at KEK. The best quality data with the energy resolution of 1.63 MeV(FWHM) was obtained in the highest statistics so far. In the spectrum, we can find a splitting of the f-orbital of a Λ particle with the separation of 1.6±0.15 MeV(statistical error only), which may be attributed to the spin-orbit splitting. 相似文献
20.
We give a more complete calculation of b → se+ e− decay including leading log QCD corrections from mtop to MW in addition to corrections from MW to mb. The differential decay rate is found to be slightly suppressed for a large invariant mass of the e+ e− pair; while the integrated width is slightly enhanced comparing with the results without the QCD running from mtop to MW. 相似文献