Search for charged-particle emission from deuterated palladium foils

Results are presented from the search for energetic charged particles possibly emitted from a deuterium loaded palladium electrode in an electrolysis cell. Within the sensitivity of our experimental set-up, we could not find events originating from ‘cold nuclear fusion’ processes. Based on this outcome, an upper limit for the non-observation of CNF of 2.0×10^?2s^?1 emitted charged particles per cm³(Pd) resp. 1.6×10^?24s^?1 emitted charged particles per D pair has been deduced.     

Spontaneous two-photon emission from a single quantum dot

Spontaneous two-photon emission from a solid-state single quantum emitter is observed. We investigated photoluminescence from the neutral biexciton in a single semiconductor quantum dot coupled with a high Q photonic crystal nanocavity. When the cavity is resonant to the half energy of the biexciton, the strong vacuum field in the cavity inspires the biexciton to simultaneously emit two photons into the mode, resulting in clear emission enhancement of the mode. Meanwhile, the suppression of other single photon emission from the biexciton was observed, as the two-photon emission process becomes faster than the others at the resonance.     

Stimulated two-photon emission from excitonic molecules in ZnO

The M-band emission in ZnO at 1.7 K is investigated by tuning the excitation light through the A-B exciton region. Externally stimulated two-photon emission from excitonic molecules is observed when the pump photon energy is resonant with the upper B-polariton. The experiments suggest two excitonic molecule levels separated by 4.6 meV and with a ground state energy E_M = 6.7394 eV.     

The emission of correlated electrons from surfaces

This work offers a theoretical framework for the treatment of the simultaneous many-electron excitation in solids and surfaces. Starting from the transition operator, an expansion is presented that treats all involved interactions on equal footing. The method is applied to the simultaneous two-orbital excitation and the results are compared with recent experimental findings. It is concluded that such studies provide a useful tool for the investigation of inter-electronic coupling. Received: 23 March 1999 / Accepted: 25 June 1999 / Published online: 23 September 1999     

Search for spontaneous pion emission from252Cf source

An experiment was carried out at Saclay, in order to determine the ratio Γ_π/Γ_SF with a²⁵²Cf source. An upper limit to this ratio is obtained, but the existence of spontaneous pion emission phenomenon is still an open question.     

Search for mass-symmetric ternary fission in the reactions 14N(53 A MeV)+197Au and 232Th

Ternary fission of heavy hot composite systems with excitation energies of 1.5–2.5 MeV$\text{/}$amu has been studied in the reactions of ¹⁴N(53 $\text{A}$ MeV) with ¹⁹⁷Au and ²³²Th. The ternary yields have been explored as a function of the charge $\text{Z}{}_{\mathrm{<mtext>L</mtext>}}$ of the lightest fragment: while $\text{Z}{}_{\mathrm{<mtext>L</mtext>}}$ increases from 6 to 25, the cross sections decrease from 5 to 0.08 mb for N$\text{+}$Au and from 15 to 0.8 mb for N$\text{+}$Th. The velocity vector $\text{v}\text{→}{}_{\mathrm{<mtext>L</mtext>}}$ of the lightest fragment has been investigated in the rest frame of the other two heavier fragments. Two different components are observed: (i) an isotropic one with values of $\text{v}{}_{\mathrm{<mtext>L</mtext>}}$ corresponding to the Coulomb repulsion from the combined heavier fragments before separation and, (ii) an anisotropic contribution with the lightest fragment emitted with lower $\text{v}{}_{\mathrm{<mtext>L</mtext>}}$ perpendicular to the scission axis of the two heavier fragments. The latter component is distinguished from the isotropic one by an enhanced fraction of mass-symmetric ternary events and by up to 50 MeV lower total kinetic fragment energies. These features are indicative of a collinear stretched scission configuration, where the lightest fragment is positioned between the two heavier ones.     

Fission accompanied by alpha particle emission in the12C(85MeV)+232Th reaction

Inclusive and coincident spectra of alpha particles and fission fragments were measured for the²³²Th+¹²C (85 MeV) reaction to study the influence of the excitation energy and the angular momentum on the fission of the compound nucleus and to separate different alpha particle emission mechanisms. At backward angles α emission can be accounted for by the evaporation processes. At forward angles the most important contribution is given by the break-up fusion process. Mass distributions for compound nuclei²⁴⁴Cm (E^*=58 MeV,ff coincidences), and²⁴⁰Pu (E^*=37 MeV,ff α coincidences) were obtained. In the case of²⁴⁰Pu mass distribution has a shape different from those obtained in light ion reactions at the same excitation energy, indicating the strong influence of the entrance channel. The dependence of the mass distribution shape on the α particle energy is also examined.     

Hyperentanglement source by intersubband two-photon emission from semiconductor quantum wells

We propose an efficient hyperentanglement source emitting photon pairs entangled in both energy and polarization. The compact electrically driven room-temperature source, based on intersubband two-photon emission from semiconductor quantum wells (QWs) exhibits pair generation rates several orders of magnitude higher than alternative conventional schemes. A theoretical formalism is derived for the calculation of photon pair generation spectra and rates. The results are presented for superlattice structures similar to quantum cascade lasers of GaAs/AlGaAs QWs emitting in the mid-IR and far-IR and for InN/AlN QW structures suitable for telecommunication wavelengths.     

Ternary fission involving4He emission in the16O (144 MeV)+232Th and12C (108 MeV)+197Au reactions

The results of coincidence measurements of⁴He emission with fission fragments in reactions of¹²C(108 MeV) ions with a¹⁹⁷Au target and of¹⁶O(144 MeV) ions with a²³²Th target are presented. On the basis of a Monte Carlo kinematic simulation of nuclear reactions the experimental energy spectra and velocity distributions of alpha particles have been analyzed. A conclusion has been drawn that the main source of⁴ He emission is evaporation from the fissioning compound nucleus. Substantial part of alpha particles was emitted from fully accelerated fission fragments. Some of⁴He nuclei with an average energy of about 16 MeV (in the CM system) emitted mainly perpendicular to the fission axis were identified as being similar long-range alpha particles produced in ternary fission of heavy nuclei at a low excitation energy. The emission multiplicities of these particles are considerably higher than those observed at a low excitation energy. The experimental results are compared with the statistical model predictions.     

Search for correlated neutral strange particles and muon production in π−p interactions at 225 GeV

A measurement is made of the production correlation between neutral strange particles V and muons. The interactions originated in a streamer chamber containing a Lucite target bombarded by 225 GeV π^? mesons. The experiment has a sensitivity of 10 events per nanobarn and yields no evidence for new particles.     

Search for nu(e) from the sun at Super-Kamiokande-I

We present the results of a search for low energy nu(e) from the Sun using 1496 days of data from Super-Kamiokande-I. We observe no significant excess of events and set an upper limit for the conversion probability to nu(e) of the 8B solar neutrino. This conversion limit is 0.8% (90% C.L.) of the standard solar model's neutrino flux for total energy=8-20 MeV. We also set a flux limit for monochromatic nu(e) for E(nu(e))=10-17 MeV.     

Search for large-rapidity-gap events in e+e− annihilation

We investigate the cross section for the production of a low-mass colour-singlet cluster ine ⁺ e ^? annihilation with a large rapidity gap between the colour-singlet cluster and the other jets. It is argued that such events are the cross-channel analogue of large-rapidity-gap events in deep-inelastic scattering, and therefore could in principle be used to investigate the analytic continuation of the BFKL pomeron to the positive-t kinematic regime, where one would expect the trajectory to pass through glueball states. The cross section can be calculated in perturbative QCD, so that the infrared scale arising from non-perturbative effects, which prevents an exponential fall-off with rapidity gap in the case of deep-inelastic scattering, is absent ine ⁺ e ^? annihilation. Correspondingly, the cross section for such events decreases rapidly with increasing rapidity gap.     

中低能入射电子与氦离子碰撞的(e,2e)反应三重微分截面

利用Ｂｅｒａｋｄａｒ和Ｂｒｉｇｇｓ对ＢＢＫ波函数Ｓｏｍｍｅｒｆｅｌｄ参数的修正结果（即考虑第三个粒子存在对两个粒子间相互作用的影响），并考虑了入射道的库仑相互作用及出射电子的交换对称性，计算了在共面－等能分享－固定相对角度几何情况下，入射能量分别为:５８．４、６８、８１．６、１０８．８和１７４．４ｅＶ的Ｈｅ＋（ｅ，２ｅ）反应三重微分截面．结果表明，在较低碰撞能量散射中，入射道库仑场对两体碰撞起主要作用． A corrrelated three body continuum wavefunction proposed by Brauner et al has been recently modified further to allow for three body effects by introducing Somerfeld parameters (Berakdar and Briggs). The triple differential cross sections for electron impact ionization of He+ in coplanar equal energy sharing and fixed relative angle geometry are calculated. The initial channel wavefunction involves a Coulomb wavefunction due to the long range Coulomb attraction between the incident...     

Simultaneous measurements of second-harmonic generation and two-photon photoelectric emission from Au

Received: 1 October 1998 / Accepted: 30 October 1998     

A parton shower model for hadronic two-photon process in e+e− scattering

A new model of QCD parton shower is proposed which is dedicated to two-photon processes in e⁺e^? scattering. When hadron jets are produced, the photon may resolve into quark-antiquark pairs so that the structure functions of the photon should be introduced. Based on the Altarelli-Parisi equation for these functions, an algorithm is formulated that allows us to construct a model for parton showers for the photon. Our model consists of two parts, one of which describes the deep inelastic scattering of the photon and the other one the scattering of two quasi-real photons. Using the model some results are presented on parton distributions and jet production.