A search for massive photinos at petra

We have searched for the supersymmetric partner of the photon, the photino, by investigating two-photon and single photon final states in e⁺e^? collisions. No significant signals were observed, which excludes the existence of the photino in the mass range 0.08–18 GeV/c² at the 95% confidence level, subject to the assumptions d=(100 GeV)² and $\text{m}{}_{\mathrm{<mtext>e</mtext><mtext>?</mtext>}}\text{=40}\text{GeV}\text{/c}{}^2$, where d is the supersymmetry breaking scale parameter and $\text{m}{}_{\mathrm{<mtext>e</mtext><mtext>?</mtext>}}$ is the scalar electron mass.     

Tamm surface states of films Hg1−xCdxTe

Using Kane model Tamm surface states spectra for semimetal and semiconductor samples Hg_1?xCd_xTe with finite thickness were obtained. In the limit of thin film (qL ? 1, q - quasi-momentum of surface state, L - film thickness) only the spectrum of antisymmetric surface states differs significantly from that of bulk electrons. Ratio of effective mass of these states to that of bulk electrons, in the parabolic limit (ε_g → ∞), is four $\text{(}\text{m}{}_{\mathrm{s}}\text{m}{}_{\mathrm{e}}\text{=4)}$. In the nonparabolic limit (ε_g → 0) the ratio of Kane parameter of these states to that of bulk electrons is half $\text{(}\text{P}{}_{\mathrm{s}}\text{P}{}_{\mathrm{e}}\text{=}\text{1}\text{2}\text{)}$. In the limit of thick film (L → ∞) these ratios differ from unity for some percents (5 + 6%).     

The intermediate weak boson and weak interactions at high energy

The high-energy pire-leptonic weak interaction is investigated based on the assumption of the existence of a charged vector boson which mediates the weak processes. With the aid of the fixed-t dispersion relation the following relation is obtained: The weak boson mass m_W should satisfy $\text{m}{}_{\mathrm{<mtext>W</mtext>}}\text{? G}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}$, with G the Fermi coupling constant, if the asymptotic value of the cross section becomes of the order of the strong interaction in the energy region observable in cosmic rays, etc.The scattering processes $\text{e}\text{+ν→}\text{e}\text{+ν}\text{and}\text{e}\text{+}\text{ν}\text{→}\text{e}\text{+}\text{ν}$ are examined by the aid of the N/D method. For a large vector-boson mass $\text{m}{}_{\mathrm{<mtext>W</mtext>}}\text{?100}\text{GeV}$, an S-wave resonance should exist for the process e+ν→e+ν while for $\text{e}\text{+}\text{ν}\text{→}\text{e}\text{+}\text{ν}$ there should exist a P-wave resonance which corresponds to the intermediate weak boson. The neutral current is then estimated. It is shown that the neutral current produced as a higher-order effect is not inconsistent with the present experiments on the pure-leptonic weak interaction if m_W?1 TeV.     

Full O(αew) electroweak corrections to e+e−→HHZ

We calculate the full $\text{O}\text{(α}{}_{\mathrm{<mtext>ew</mtext>}}\text{)}$ electroweak corrections to the Higgs pair production process e⁺e⁻→HHZ at an electron–positron linear collider in the standard model, and analyze the dependence of the Born cross section and the corrected cross section on the Higgs boson mass m_H and the c.m. energy $\text{s}$. To see the origin of some of the large corrections clearly, we calculate the QED and genuine weak corrections separately. The numerical results show that the corrections significantly suppress or enhance the Born cross section, depending on the values of m_H and $\text{s}$. For the c.m. energy $\text{s}\text{=500}$ GeV, which is the most favorable colliding energy for HHZ production with intermediate Higgs boson mass, the relative correction decreases from −5.3% to −11.5% as m_H increases from 100 to 150 GeV. For the range of the c.m. energy where the cross section is relatively large, the genuine weak relative correction is small, less than 5%.     

Conditions for static balance for the post-Newtonian two-body problem with electric charge in general relativity

The usual condition for static balance, for two bodies with masses and charges m_i and e_i (i = 1, 2), is $\text{e}{}_{\mathrm{i}}\text{=±G}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{m}{}_{\mathrm{i}}$. From a post-Newtonian analysis of the two-body problem, an alternate condition for static balance $\text{e}{}_{\mathrm{i}}\text{=±(Gm}{}_1\text{m}{}_2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ has been found. We do not know if this condition is exact beyond the post-Newtonian approximation.     

Gluinos and lower bounds for squark and slepton masses from jet plus missing-pT events at the pp collider

On the basis of a detailed phenomenological analysis, combined with the minimal N = 1 supergravity model, it is shown that the jet plus missing-p_T events at the p$\text{p}$ collider can only be explained by relatively light gluinos ($\text{m}\text{g}\text{?}\text{< m}\text{q}\text{?}$ with a mass of about 40 GeV. The resulting squark and slepton masses are then found to be $\text{q}\text{?}\text{> 50}$ GeV and $\text{m}\text{e}\text{?}\text{> 35}$ GeV.     

Radiative decays of the Jψ and evidence for a new heavy resonance

The three photon final state produced in e⁺e^? collisions has been measured at the mass of the $\text{J}\text{ψ}$ resonance using the nonmagnetic part of the double arm spectrometer DASP. The decays $\text{J}\text{ψ}\text{→ ηγ, η'γ}$ and π^oγ were observed and their branching ratios are given. A four standard deviation signal was observed in the γγ mass spectrum at a mass of (2.83 ± 0.03) GeV. An upper limit is given for the direct decay $\text{J}\text{ψ}\text{→ 3γ}$.     

Electron-exciton elastic scattering cross sections in the central field and the exchange approximations

The elastic scattering cross sections for the semiconductors ZnO, CdS, CdSe, Si and Cu₂O have been calculated in the central field and exchange approximations. The calculations are carried out as function of the different available values of $\text{σ=}\text{m}{}^1{}_{\mathrm{e}}\text{m}{}^1{}_{\mathrm{h}}\text{where}\text{m}{}^1{}_{\mathrm{e}}\text{and}\text{m}{}^1{}_{\mathrm{h}}$ are, respectively, the electr masses for the corresponding semiconductors. The effect of exchange decreases as σ increases. Good agreement between the experiment and the central field approximation is obtained for Si with the value of σ = 0.24.     

Thermal desorption of cyanogen from Pt(100)

Thermal desorption of cyanogen adsorbed on Pt(100) was studied by flash desorption mass spectrometry. By investigating the parent ion and all possible fragmentation products in the mass spectrometer during desorption it was concluded, that desorption takes place exclusively as molecular C₂N₂. Three desorption peaks were observed at 140, 410 and 480°C denoted as α, β₁ and β₂. The respective surface coverages at saturation were determined by quantitative evaluation of the flash desorption curves to be 2.0 ± 0.2 × 10¹⁴ and 5.5 ± 1.0 × 10¹⁴$\text{molecules}\text{cm}{}^2$ for the α and the β states, respectively. First order desorption kinetics was suggested by the coverage dependencé of the desorption spectra for both α and β states with desorption energies of 12 and 38–42 $\text{kcal}\text{mole}$, respectively. A large difference in the sticking probabilities of α and β states was observed with initial values of 0.06 (α) and 0.9 (β). Adsorption experiments at elevated temperatures led to the assumption, that α and β states coexist on the surface with no or very little interactions between them. The results are discussed in terms of different models for the adsorption states.     

Exciton-exciton elastic scattering cross sections for different semiconductors

The exciton-exciton elastic scattering cross sections for the different semiconductors ZnO, CdS, CdSe and Si have been calculated in the central field approximation with and without the symmetry effect in the collision of the two identical excitons. The calculations are carried out as function of the different available values of $\text{σ =}\text{m}{}_{\mathrm{e}}{}^1\text{m}{}_{\mathrm{h}}{}^1$, where m¹_e, and m¹_h are, respectively, the electron and t semiconductors.     

On the geometrical aspects of electromagnetism,I

The trajectory of a charged test particle under a Lorentz force is obtained as the geodesic of a riemannian four dimensional manifold. Originally, the geodesic equation is nonlinear in some vector field A′_μ. The nonlinearity is traded in for the correct characteristic $\text{e}\text{m}$ of the test particle through a gauge condition, imposed upon A′_μ, which turns the geodesic into the fully covariant linear and gauge invariant Lorentz equation. Fitting the $\text{e}\text{m}$ ratio inside the gauge leaves F′_μν independent of $\text{e}\text{m}$ and allows its identification with the E.-M. tensor F_μν. This four dimensional approach allows the identification of the fifth coordinate used in Kaluza's geometrization |1,2|. The gauge function appears as the sum of Hamilton-Jacobi function plus an additional term, related to the “length” of the trajectory. It is this latter term which guarantees the correct “normalisation” of the $\text{e}\text{m}$ ratio.     

Infrared cyclotron resonance in InSb,GaAs and Ge in very high magnetic fields

Infrared cyclotron resonance was observed in n-type InSb, GaAs and Ge in very high magnetic fields up to 1.3 MOe at room temperature using a CO₂ laser. A large shift of the cyclotron mass due to the non-parabolicity of the energy band was found in each material. The band edge masses of electrons at room temperature were evaluated to be $\text{m}{}^1\text{= 0.0127 m}$ for InSb, $\text{m}{}^1\text{= 0.065}$m for GaAs and $\text{m}{}^1{}_{\mathrm{t}}\text{= 0.086}$m for Ge. The linewidth was measured in GaAs and Ge in the high fields.     

Magnetic moments of composite fermions

There have been a considerable number of papers proposing composite models for leptons and quarks. Recently, Glück and Lipkin have stated that reproducing the observed magnetic moments of these fermions presents a serious difficulty for these composite models. We show for a renormalizable theory that, in contrast to Glück's and Lipkin's nonrelativistic arguments, a deeply bound system (with heavy constituent particle masses m_c) of (total) spin $\text{1}\text{2}$, charge e and mass m has the magnetic moment $\text{(e/2m) [1 +}\text{“usual” (QED + QCD + weak) corrections +O}\text{(m/m}{}_{\mathrm{<mtext>c</mtext>}}\text{)}\text{“new” bindng corrections]}$. Although there remains the considerable dynamical problem of obtaining “light” bound fermions from heavy constituents, there is no separate, additional magnetic moment difficulty.     

Observation of a narrow resonance formed in e+e− annihilation at 9.46 GeV

An experiment using the PLUTO detector has observed the formation of a narrow, high mass, resonance in e⁺e^? annihilations at the DORIS storage ring. The mass is determined to be 9.46±0.01 GeV which is consistent with that of the Upsilon. The gaussian width σ is observed as 8±1 MeV and is equal to the DORIS energy resolution. This suggests that the resonance is a bound state of a new heavy quark-antiquark pair. An electronic width Γ_ee=1.3±0.4 keV was obtained. In standard theoretical models, this favors a quark charge assignment of $\text{1}\text{3}$.     

Search for new flavour production at PETRA

The topological distribution of hadrons from the reaction e⁺e^?→multihadrons has been studied at PETRA energies between $\text{s}\text{=22}\text{and}\text{31.6 GeV}$. No evidence is seen for spherical events which would be expected if massive particles bearing new flavours were produced.     

Polaron cyclotron resonance in n-CdTe and n-InP

The interaction of electrons and polar-optical phonons is investigated for CdTe and InP in cylotron resonance (CR) emission and absorption experiments. Under hot electron conditions three different Landau level transitions are observed. From the positions of the fundamental transition and the CR line splittings the nonparabolicity and the polaron contribution to the effective mass are analysed using a variational approach for the polaron shifts. The bare band edge masses and the polaron coupling constants are determined to be $\text{m}{}^1{}_{\mathrm{<mtext>0</mtext>}}\text{=}\text{0.0900±0.0005}$, α=0.35+-0.03 for CdTe and $\text{m}{}^1{}_{\mathrm{<mtext>0</mtext>}}\text{=}\text{0.0765±0.0005}$, α=0.15±0.01 for InP.     

A search for stable particles heavier than the proton and for Q = −23 quarks produced in e+e− annihilation

We have searched 1.4 × 10⁶e⁺e^? annihilation events for particles with 1–3 GeV/c² mass and charge $\text{Q = ?}\text{2}\text{3}$ from the processes e⁺e^?→q$\text{q}$X and e⁺e^? → q$\text{q}$. Upper limits of RQ ～ 10^?4 for each process are presented which improve the previous limits on free quark production in electromagnetic interactions by 2 orders of magnitude.     

Electron and hole conductivity in CuInS2

Single crystals of CuInS₂ have been grown from the melt and annealed in In or S to produce good n- or p-type conductivity, respectively. Two donor levels, one shallow and one deep (0.35 eV), and one acceptor level at 0.15 eV are identified. The hole-mobility data are best fitted with an effective mass $\text{m}{}_{\mathrm{<mtext>p</mtext>}}\text{1?1.3m}{}_{\mathrm{e}}$, which can be explained by simple, two band $\text{k}$. $\text{p}$ theory if the valence band has appreciable d character. Above 300°K, the hole mobility falls rapidly, evidently due to multiband conduction and/or interband scattering between the nondegenerate and degenerate valence bands. The conduction band mobility appears to be dominated, in many samples, by large concentrations ( >10¹⁸cm^?3) of native donors and acceptors, which are closely compensated.     

Optical properties of (TTF) (TCNQ) in the visible and infrared

Polarized optical studies of single crystals and polycrystalline compactions of the organic salt (TTF) (TCNQ) are reported. Metallic behavior is observed for light polarized parallel to the conducting axis. The plasma edge occurs at 1.4 μm with metallic reflection observed in the i.r. The plasma frequency $\text{(}\text{h}\text{?}\text{ω}{}_{\mathrm{p}}\text{=}\text{1.2eV}\text{)}$ leads to an optical effective mass $\text{m}{}^1\text{=}\text{5}\text{m}{}_{\mathrm{e}}$ implying a tight-binding transfer integral of 0.1 eV in agreement with estimates obtained from other measurements. The scattering time, τ, as determined from the shape of the reflectance curve, yields a room temperature metallic conductivity of 10³(Ω-cm)^-1 in good agreement with the measured d.c. value. An estimate of the dimensionless electron-phonon coupling constant is obtained from the measured value of τ,λ_ph?1.3. The strong anisotropic absorption in the visible portion of the spectrum is attributed to interband transitions.