A-dependence of ΛΛ bond energies in double-Λ hypernuclei

The A-dependence of the bond energy ΔB_ΛΛ of the ΛΛ hypernuclear ground states is calculated in a three-body Λ + Λ + ^A Z model and in the Skyrme-Hartree-Fock approach. Various ΛΛ and Λ-nucleus or ΛN potentials are used and the sensitivity of ΔB_ΛΛ to the interactions is discussed. It is shown that in medium and heavy ΛΛ hypernuclei, ΔB_ΛΛ is a linear function of r _Λ ^{? 3} , where r _Λ is rms radius of the hyperon orbital. It looks unlikely that it will be possible to extract ΛΛ interaction from the double-Λ hypernuclear energies only, the additional information about the Λ- core interaction, in particular, on r _Λ is needed.     

Progress in p-shell Λ hypernuclear spectroscopy

The strangeness nuclear physics is an important branch of nuclear physics. The spectroscopic study of A hypernuclei has been used as a tool for investigating the A-N interaction as well as probing the nuclear interior structure. In this paper some high-lights and open questions in the spectroscopic study of p-shell h hypernuclei are presented.     

Consistency of field equations in “Self-Creation” cosmologies

It is pointed out that the field equations in one of Barber's two self-creation cosmologies are not only in disagreement with experiment, but are actually inconsistent, in general. The construction of consistent general relativistic field equations involving field variables, such as, without invoking Lagrangian techniques, requires careful checking that sufficient functional freedom has been provided so as to produce a consistent set of equations.     

The Histories Interpretation: Stability Instead of Consistency?

Using a reformulation of conventional results in decoherence theory, a condition is proposed for singling out a distinguished class of histories which includes those which use the pointer basis of Zurek.     

Consistency of new π N phase-shift analyses with dispersion relations

New phase-shift analyses for pion-nucleon scattering are used to check the dispersion relations for the amplitudesB _±(v _L, 0), which are essentially determined by the pionnucleon spin-flip scattering extrapolated to forward direction. Within the experimental errors, the relations seem to be fulfilled. The pion-nucleon coupling constantf ² turns out to be consistent with the value found byHamilton andWoolcock, who obtainedf ²=0,081±0,003. However, in spite of the newer data and less sensitivity of our calculational procedure toward the high-energy behaviour of the amplitudes, the error off ² is still considered as somewhat larger. Our method also gives some information on the high-energy behavior of the spin-flip amplitude.     

A note on the origin of secondary hypernuclear γ-quanta from Λ 10 B

An alternative interpretation of _Λ ¹⁰ B secondaryγ-quanta due to _Λ ¹⁰ B → _Λ ⁷ Li+³He channel is proposed. Its impact on effectiveΛN interaction properties and on understanding of (s ^?1 s _Λ) configurations is discussed and some verifying experiments are put forward.     

Double-λ hypernuclear production in high-energy heavy-ion collisions

The production of double- hypernuclei was studied regarding three different mechanisms: (1) coalescence of a nuclear fragment from peripheral collisions and two A particles, (2) coalescence of two A particles, neutrons and protons due to central collisions, and (3) conversion of a hypernucleus. The production probability is estimated for several projectile-target combinations at 5 and 14.5 GeV/nucleon.     

Double-Λ hypernuclei and the nuclear medium effective ΛΛ interaction

We fit the ¹S₀ ΛΛ interaction in the nuclear medium to the masses of the experimentally known double-Λ hypernuclei: _ΛΛ⁶He, _ΛΛ¹⁰Be and _ΛΛ¹³B. We derive this effective interaction from OBE Jülich ΛΛ-type potentials and using both Hartree-Fock and variational approaches. We find that the inclusion of ΛΛ correlations in the variational scheme leads to significant differences and a better understanding of the dynamical features of the system. We investigate the sensitivity of the binding energies and the mesonic decay widths of the above double-Λ hypernuclei to the ωΛΛ coupling and the form factor at the σΛΛ vertex. We also use this effective interaction to predict binding energies and pionic decay widths of heavier double-Λ hypernuclei, not discovered yet. Finally, we discard the existence of ¹S₀ ΛΛ bound states provided the ΛΛ-ΞN coupling can be neglected.     

Determination of the number of ψ' events at BES Ⅲ

The number of ψ' events accumulated by the BESⅢ experiment from March 3 through April 14, 2009, is determined by counting inclusive hadronic events. The result is 106.41×(1.00±0.81%)×106 . The error is systematic dominant; the statistical error is negligible.     

Determination of the number of ψ' events at BESⅢ

The number of ψ’ events accumulated by the BESⅢ experiment from March 3 through April 14, 2009, is determined by counting inclusive hadronic events. The result is 106.41×(1.00±0.81%)×106 . The error is systematic dominant; the statistical error is negligible.     

Impurity effects of the Λ hyperon in the hypernuclear systems Λ25Mg and Λ29Si

Based on the beyond-mean-field Skyrme-Hartree-Fock model,impurity effects of the Λ hyperon in the hypernuclear systems Λ25Mg and Λ29Si are investigated,respecti...     

Is nuclear structure relevant to non-mesonic hypernuclear weak decay?

This work studies the relevance of nuclear structure in the nonmesonic weak decay of Λ-hypernuclei, with the mechanism of ΛN → NN transition being restricted to one pion exchange (OPE) only. As an application, for the hypernucleus _Λ ¹² C a comparison between the L-S coupling and the j-j coupling gives an estimate of the range of nuclear structure effects. A considerable dependence is found of the total decay rate and the ratio Г _n /qG _p on the single particle properties of nuclear models. The possible contribution from the ΔI = 3/2 channel is investigated in a phenomenological manner.     

Estimation of parameters of an alternate stream of events in “dead” time conditions

An alternate stream of events is examined in circumstances where each successive event gives rise to some unobservability period (“dead” time) of fixed duration during which other events are unobservable. The parameters of the alternate stream of events are estimated by the moment method. The dead time estimate is chosen empirically. Confidence intervals for the estimates are constructed using the data from a statistical experiment. Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 8–13, April, 1999.     

Determination of the number of ψ(3686)events at BESⅢ

The numbers of ψ(3686) events accumulated by the BESⅢ detector for the data taken during 2009 and2012 are determined to be(107.0±0.8)×10~6 and(341.1±2.1)×10~6, respectively, by counting inclusive hadronic events,where the uncertainties are systematic and the statistical uncertainties are negligible. The number of events for the sample taken in 2009 is consistent with that of the previous measurement. The total number of ψ(3686) events for the two data taking periods is(448.1±2.9)×10~6.     

Pressure－Balance Consistency in Magnetospheric Modelling

There have been many magnetic field models for geophysical and astrophysicM bodies. These theoretical or empirical models represent the reality very well in some cases, but in other cases they may be far from reality. We argue that these models will become more reasonable if they are modified by some coordinate transformations. In order to demonstrate the transformation, we use this method to resolve the “pressure-balance inconsistency” problem that occurs when plasma transports from the outer plasma sheet of the Earth into the inner plasma sheet.     

Trend of extreme precipitation events over China in last 40 years

Using the daily precipitation data of 740 stations in China from 1960 to 2000, the analysis on the variations and distributions of the frequency and the percentage of extreme precipitation to the annual rainfall have been performed in this paper. Results indicate that the percentage of heavy rains （above 25mm/day） in the annual rainfall has increased, while on average the day number of heavy rains has slightly reduced during the past 40 years. In the end of 1970s and the beginning of 1980s, both the number of days with extreme precipitation and the percentage of extreme precipitation abruptly changed over China, especially in the northern China. By moving t test, the abrupt change year of extreme precipitation for each station and its spatial distribution over the whole country are also obtained. The abrupt change years concentrated in 1978-1982 for most regions of northern China while occurred at various stations in southern China in greatly different/diverse years. Besides the abrupt change years of extreme precipitation at part stations of Northwest China happened about 5 years later in comparison with that of the country＇s average.     

On the Renormalization of the One–Pion Exchange Potential and the Consistency of Weinberg’s Power Counting

Nogga, Timmermans and van Kolck recently argued that Weinberg’s power counting in the few–nucleon sector is inconsistent and requires modifications. Their argument is based on the observed cutoff dependence of the nucleon–nucleon scattering amplitude calculated by solving the Lippmann–Schwinger equation with the regularized one–pion exchange potential and the cutoff Λ varied in the range Λ = 2 . . . 20 fm^?1. In this paper we discuss the role the cutoff plays in the application of chiral effective field theory to the two–nucleon system and study carefully the cutoff–dependence of phase shifts and observables based on the one–pion exchange potential. We show that (i) there is no need to use the momentum–space cutoff larger than Λ ~ 3 fm^?1; (ii) the neutron–proton low–energy data show no evidence for an inconsistency of Weinberg’s power counting if one uses Λ ~ 3 fm^?1.     

Excitation and structure of hypernuclear resonances in (K −,π ¯0)-reactions on 1p-shell nuclei

The available experimental data on the excitation functions (EF) of the 1p-shellΛ-hy-pernuclei in (K ^?, π^?) reactions atθ _π = 0^° has been analysed in terms of shell model and weak coupling scheme. It is substantiated by the experimental data on the neutron spectroscopic factors and on the fragmentation of nuclear hole excitations. The pronounced nuclear spectroscopic characteristics in the hypernuclear spectra are indicative of a weak coupling ofΛ-hyperon with nuclear subsystem. The analysis has made it possible to determine the difference is single-particle energies ofΛ-hyperon in the 1p- and 1s-states and to obtain additional evidence for the smallness of theΛ-nucleus spin-orbit interaction. The resonance structure of EF of hypernuclei, which were not studied in (K ^?,π ₀ ^? ) reactions, is predicted. The interrelated aspects of the studies of the (K ^?,π ₀ ^? ), (K ^?,π ₀ ^? β^′), and (K ^?, π⁺) reactions which are of interest to spectroscopy ofΛ-andΣ-hypernuclei are discussed.     

Determination of the number of J/ψ events with inclusive J/ψ decays

A measurement of the number of J/ψ events collected with the BESⅢ detector in 2009 and 2012 is performed using inclusive decays of the J/ψ. The number of J/ψ events taken in 2009 is recalculated to be(223.7±1.4)×10~6, which is in good agreement with the previous measurement, but with significantly improved precision due to improvements in the BESⅢ software. The number of J/ψ events taken in 2012 is determined to be(1086.9±6.0)×10~6. In total, the number of J/ψ events collected with the BESⅢ detector is measured to be(1310.6±7.0)×106, where the uncertainty is dominated by systematic effects and the statistical uncertainty is negligible.