Testing supersymmetry in the associated production of CP-odd and charged Higgs bosons

In the Minimal Supersymmetric Standard Model (MSSM), the masses of the charged Higgs boson (H±) and the CP-odd scalar (A) are related by MH+2=MA2+mW2. Furthermore, because the coupling of W−–A–H+ is fixed by gauge interaction, the tree level production rate of depends only on one supersymmetry parameter—the mass (MA) of A. We show that to a good approximation this conclusion also holds at the one-loop level. Consequently, this process can be used to distinguish MSSM from its alternatives (such as a general two-Higgs-doublet model) by verifying the above mass relation, and to test the prediction of the MSSM on the product of the decay branching ratios of A and H± in terms of only one single parameter—MA.     

Experimental study of the time-dependent rate of K → πππ

The time-dependence of the decay rate of initially pure K⁰ into the final state (π⁺π⁻π⁰) has been studied in search for the decay k_S⁰→π⁺π⁻π⁰. No evidence is found in a sample of 384 observed events. The ratio of the CP -violating K_S⁰ amplitude and the K_L⁰ amplitude is η₊₋₀ = (0.13_−0.20^+0.17) + i(0.17_−0.26^+0.27); the ratio of the CP-conserving K_S⁰ amplitude and the K_L⁰ amplitude is < 0.4. The energy dependence of the K⁰→π⁺π⁻π⁰ matrix element is found to be a₊₋₀ = −0.31 ± 0.03.     

Nb/Au/(1 1 0)YBa2Cu3O7−δ Josephson junctions: evidence against atomic scaled “corner junctions”

We report on I–V characteristics for in situ formed Nb/Au/(1 1 0)YBa₂Cu₃O_7−δ (YBCO) Josephson junction, where the homoepitaxial (1 1 0)YBCO film shows ultra-smooth surface morphology. The field dependence of critical supercurrent I_c shows anisotropic large junction behavior with normal Fraunhofer patterns expected from BCS model of d_x²−y² wave superconductors. This strongly suggests that the Nb/Au/(1 1 0)YBCO junctions cannot be regarded as atomic scaled corner junctions, in contrast with (0 0 1)/(1 1 0)YBCO grain boundary junctions to show “π-junction” with a pronounced dip near zero fields in field modulation of I_c.     

Electro-pion production on O to bou nd states of the residual nuclei

Differential cross sections for the reactions 16O(γ, π−π+−)16F16F to the sum of the four lowest lying states in 16F and 16N have been measured as a function of angle for pions with a kinetic energy of 30 MeV. The extracted ratios R = σ(γ, π−)/σ(γ, π+), the first ones to discrete final states as a function of angle, are in fair agreement with results obtained for the nucleon. For positive pions the energy dependence of the cross section has been measured at the angles of 45° and 90°. Distorted wave impulse approximation calculations fail to describe the energy dependence.     

Magnetooptical studies of defects and recombination luminescence in LiBaF3

Optically detected EPR investigations have been performed on the recombination luminescence (RL-EPR) of LiBaF₃ crystal, X-irradiated at T=4.2 K. RL-EPR lines of V_K- centres were found, as well as further lines of a defect with and an axial g-tensor with its main axis along a [1 0 0] direction of the crystal.

Measurements of the magnetic circular dichroism of the absorption (MCDA) have been performed on LiBaF₃ crystals X-irradiated at two temperatures (4.2 K and RT). After irradiation at T=4.2 K, the main MCDA bands peak at 453 and 500 nm, but after irradiation at T=300 K, the main bands peak at 444 and 390 nm, there is a change of the sign between the peaks in both cases. The MCDA-detected EPR (MCDA-EPR) consists of one broad EPR line in both cases and belong to electron trap centres. Analysis of half-widths of MCDA-EPR lines showed that both defects should have g-tensors with their axes along the [1 0 0] direction. This symmetry has to be expected for F-type centres in LiBaF₃ crystals. The low-temperature electron centre has a more perturbed ground state as the RT centre.     

Evidence of kaon nuclear and Coulomb potential effects on soft K production from nuclei

The ratio of forward K⁺ production on copper, silver and gold targets to that on carbon has been measured at proton beam energies between 1.5 and 2.3 GeV as a function of the kaon momentum p_K using the ANKE spectrometer at COSY-Jülich. The strong suppression in the ratios observed for p_K<200–250 MeV/c may be ascribed to a combination of Coulomb and nuclear repulsion in the K⁺A system. This opens a new way to investigate the interaction of K⁺-mesons in the nuclear medium. Our data are consistent with a K⁺A nuclear potential of V_K⁰≈20 MeV at low kaon momenta and normal nuclear density. Given the sensitivity of the data to the kaon potential, the current experimental precision might allow one to determine V_K⁰ to better than 3 MeV.     

Vibrationally resolved band profiles for autoionisation of NO (cΠ) nℓλ (vR=0) Rydberg states into NO AΠ (vi=0, 1, 2) vibronic levels

Excitation spectra for dispersed VUV-fluorescence of NO (λ_fl=134–152 nm) were measured in the exciting-photon energy range between 16.9 and 24.8 eV using monochromatised synchrotron radiation at medium bandwidth of 29 meV. Fluorescence from A¹Π (v_i=0, 1, 2) vibronic NO⁺-levels and fluorescence from excited dissociation fragments NI (3s ²P_J) was observed simultaneously by recording the dispersed fluorescence with a monochromator–position-sensitive detector combination. The autoionisation of NO (c³Π) nℓλ (v_R=0) Rydberg levels into the NO⁺ A¹Π (v_i=0, 1, 2) vibronic levels was observed vibrationally resolved. Different Beutler–Fano profiles for autoionisation of one Rydberg level NO (c³Π) nℓλ (v_R=0) into the different vibronic NO⁺ A¹Π (v_i=0, 1, 2) levels are clearly visible. The dependence of the Beutler–Fano profiles on the quantum numbers n, ℓ, and λ of the Rydberg electron is discussed. For the direct photoionisation into the NO⁺ A¹Π (v_i=0, 1, 2) vibronic levels a non-Franck–Condon behaviour was observed.     

Strangeness production in proton collisions close to threshold at COSY-TOF

The K-meson production in elementary proton induced reactions is studied exclusively at the external COSY beam using the time-of-flight spectrometer TOF. The complete measurement of all primary and decay particle tracks allows the extraction of total and differential cross sections as well as Dalitz plots and invariant mass spectra of the subsystems for the channels pp → K⁺ Δp, K⁰Σ⁺p, K⁺Σ⁰p and K⁺Σ⁺n. For all channels the full phase space is covered from the reaction threshold up to the COSY-limit of about 3.5 GeV/c. Especially the analysis of the Dalitz plots of the channel pp→K⁺Δp show a strong influence of N₋^* resonances.     

Relationship between electronic and crystal structure in Cu–Ni–Co–Mn–O spinels: Part A: Temperature-induced structural transformation

Local atomic and crystal structures around Cu and Mn atoms in Mn_1.68Cu_0.6Ni_0.48Co_0.24O₄ spinel samples fabricated by metal–organic decomposition synthesis at different annealing temperatures were investigated by X-ray absorption fine structure analysis. There are two distinct copper cations, Cu¹⁺ and Cu²⁺, both of which maintain tetrahedral coordination. The bond-length distances are Cu¹⁺–O = 2.00 Å and Cu²⁺–O = 1.80 Å. The manganese cations are for the most part octahedral. The spinels prepared at low temperature (600 °C) contain smaller (Mn⁴⁺–O = 1.88 Å) undistorted MnO₆ octahedrons corresponding to Mn⁴⁺ valence, whereas the manganese octahedrons in high-temperature materials (800 °C and higher) were larger and had a pronounced tetragonal distortion pertaining to Mn³⁺ oxidation state (Mn³⁺–O = 1.93 Å and 2.11 Å). By rising the fabrication temperatures, relative concentration of the species of Mn⁴⁺ and Mn³⁺ varies as a result of the reaction represented by Cu¹⁺ + Mn⁴⁺  Cu²⁺ + Mn³⁺, implying irreversible temperature-induced structural transformation. Atomic coordinates in the low-temperature phase are similar to those found in the ideal cubic spinel with oxygen parameter u = 0.27, whereas local environments of the Cu and Mn atom correspond to the tetragonal CuMn₂O₄ phase (space group I4₁/amd). Unlike in CuMn₂O₄, orientation of the lattice distortions is random, however, the long-range cubic spinel structure is retained at all time.     

EPR and optical measurements of weakly doped LiNbO3: Er

Optical spectroscopy measurements of the congruent LiNbO₃ (LN) single crystals, weakly doped with Er (0.1–0.3 wt%) and Er (0.3 wt%) and Yb (0.5 wt%), have been carried out. The shape of the optical absorption and additional absorption bands registered after γ-irradiation suggests the presence of Er³⁺ ion pairs. EPR investigations were performed for LN single crystal doped with Er (0.1 wt%). Unusual behaviour of the temperature dependence of the intensity and linewidth of the main EPR line—corresponding to the fine transition of ^evenEr³⁺—ions, is reported. The main EPR line appears to be a superposition of several paramagnetic centres originating from isolated ^evenEr³⁺ ions and ^evenEr³⁺–^evenEr³⁺ pairs of ions. In low temperature region (below 20 K), the main EPR signal is dominated by signals arising from ^evenEr³⁺–^evenEr³⁺ pairs of ions. The inverse intensity of the EPR line at low temperature region fulfils the Curie–Weiss law and enabled to determine the Curie–Weiss constant Θ=1.5±0.5 K. The positive sign of Θ suggests that the ferromagnetic interactions arise in the system of ^evenEr³⁺–^evenEr³⁺ ion pairs in LN. Our results suggest that the distribution of Er ions in congruent LN is not homogeneous and Er impurity ions can form clusters in host lattice even in the case of weak erbium doping.     

Analytical result for dimensionally regularized massless master non-planar double box with one-leg off shell

The dimensionally regularized massless non-planar double box Feynman diagram with powers of propagators equal to one, one leg off the mass shell, i.e., with p₁²=q²≠0, and three legs on shell, p_i²=0, i=2,3,4, is analytically calculated for general values of q² and the Mandelstam variables s,t and u (not necessarily restricted by the physical condition s+t+u=q²). An explicit result is expressed through (generalized) polylogarithms, up to the fourth order, dependent on rational combinations of q²,s,t and u, and simple finite two- and three-fold Mellin–Barnes integrals of products of gamma functions which are easily numerically evaluated for arbitrary non-zero values of the arguments.     

Precision flavour physics and supersymmetry

We review the salient features of a comparative study of the profile of the CKM unitarity triangle, and the resulting CP-violating phases , β and γ in B decays, in the standard model and in several variants of the minimal supersymmetric standard model (MSSM), reported recently by us. These theories are characterized by a single phase in the quark flavour mixing matrix and give rise to well-defined contributions in the flavour-changing-neutral-current transitions in K and B decays. We analyse the supersymmetric contributions to the mass differences in the B_d⁰– and B_s⁰– systems, ΔM_d and ΔM_s, respectively, and to the CP-violating quantity || in K decays. Our analysis shows that the predicted ranges of β in the standard model and in MSSM models are very similar. However, precise measurements at B-factories and hadron machines may be able to distinguish these theories in terms of the other two CP-violating phases and γ.     

What can we learn from B→DsKπ, Bd→DsKπ and Bd→DsK decays?

We study the nonresonant three-body decays of B⁺→D^(*)−_sK⁺π⁺ and B_d→D_s^(*)−K⁰π⁺. We find that these decays can provide the information on the time-like form factors of D^(*)_sK. We also explicitly investigate B_d→D_s^(*)−K^*+ decays by discriminating the nonresonant contributions with the unknown D^(*)_s wave functions being fixed by the measured mode of B_d→D_s⁻K⁺.     

Search for narrow NNπ resonances in exclusive pp→ppππ measurements

Narrow structures in the range of a few MeV have been searched for in ppπ⁺ and ppπ⁻ invariant mass spectra (M_ppπ⁺ and M_ppπ⁻) obtained from exclusive measurements of the pp→ppπ⁺π⁻ reaction at T_p=725,750 and 775 MeV using the PROMICE/WASA detector at CELSIUS. The selected reaction is particularly well suited for the search for dibaryon resonances decoupled from NN and/or NΔ. In the mass range 2020 MeV/c²<m_dibaryon<2085 MeV/c² no narrow structures could be identified on the 3σ level of statistical significance neither in M_ppπ⁻ nor in M_ppπ⁺ giving an upper limit (95% C.L.) for dibaryon production in this reaction of σ<20 nb.     

Understanding DsJ(2317)

We analyze the hadronic and radiative decay modes of the recently observed D_sJ(2317) meson, in the hypothesis that it can be identified with the scalar state of spectrum (D_s0). The method is based on heavy quark symmetries and vector meson dominance ansatz. We find that the hadronic isospin violating mode D_s0→D_sπ⁰ is enhanced with respect to the radiative mode D_s0→D_s^*γ. The estimated width of the meson is Γ(D_s0)7 keV.     

Measurement of the slope parameter for the neutral pion spectrum in KL → πππ decay

The π⁰ spectrum in the K_L⁰ → 3π decay was measured using a wire chambers magnetic spectrometer. In the usual approximation, the matrix element can be expressed as: M² ≈ 1 + 2a₀(M_K/M_π²)(2T_π⁰−T_π⁰max) + a₁(M_K²/M_π⁴)(2T_π⁰−T_π⁰max)². We obtained a₀ = −0.282 ± 0.011 and a₁ consistent with zero.     

Ion-pair and triple-ion studies of some tetraalkylammonium halides in pure 1,3-dioxolane at 298.15 K

Conductivities of some tetraalkylammonium halides, viz. tetramethylammonium iodide (Me₄NI), tetraethylammonium bromide (Et₄NBr), tetraethylammonium iodide (Et₄NI), tetra-n-propylammonium bromide (Pr₄NBr), tetra-n-butylammonium bromide (Bu₄NBr), tetra-n-butylammonium iodide (Bu₄NI) and tetra-n-heptylammonium bromide (Hp₄NBr) were measured at 298.15 K in 1,3-dioxolane which has a low permittivity (ε = 7.13). A minima in the conductometric curves (molar conductance, Λ vs. square root of concentration, √c) was observed for concentrations which were dependant upon both the salt and the solvent. The observed molar conductivities were explained by the formation of ion-pairs (M⁺ + X⁻ ↔ MX, K_P) and triple-ions (2M⁺ + X⁻ ↔ M₂X⁺; M⁺ + 2X⁻ ↔ MX₂⁻, K_T). A linear relationship between the triple-ion formation constants [log (K_T/K_P)] and the salt concentrations at the minimum conductivity (log C_min) was given for all the salts in 1,3-dioxolane. The formation of triple-ions might be attributed to the ion sizes in solutions in which Coulombic interactions and non-Coulombic interactions act as the main forces between the ions (R₄N⁺…..X⁻).     

The pionium lifetime in generalized chiral perturbation theory

Pionium lifetime corrections to the nonrelativistic formula are calculated in the framework of the quasipotential–constraint theory approach. The calculation extends an earlier evaluation, made in the scheme of standard chiral perturbation theory, to the scheme of generalized chiral perturbation theory, in which the quark condensate is left as a free parameter. The pionium lifetime is calculated as a function of the combination (a₀⁰−a₀²) of the ππ S-wave scattering lengths with isospin I=0, 2.     

Temperature dependence of intensities and widths of N2-broadened lines in the 15 μm CO2 band from tunable laser measurements

Intensities and nitrogen-broadened widths of several low-J lines in the Q-branch of the 15 μm band of CO₂ have been determined over the temperature range 200–300 K. Measurements were made with a tunable infra-red diode laser spectrometer having a spectral resolution 10^-4 cm^-1. Measured intensities are uniformly about 7% lower than available calculations which were based on previous measurements of band intensity. Measured line widths are higher than available calculations and generally followed the relation

b_L⁰(T)=b_L⁰(T₀)(T₀|T)ⁿ

with n = 0.74 (standard deviation 0.08).     

Magnetic properties in BaFe12O19 nanoparticles prepared under a magnetic field

It was observed that the nanocrystallites of BaFe₁₂O₁₉ formed at 140°C under a 0.25 T magnetic field exhibited a higher saturation magnetization (6.1 emu/g at room temperature) than that of the sample (1.1 emu/g) obtained under zero magnetic field. Both of the two approaches yielded plain-like particles with an average particle size of 12 nm. However, the Curie temperature (T_c), a direct measuring of the strength of superexchange interaction of Fe³⁺–O²⁻–Fe³⁺, increased from 410°C for the nanoparticles prepared without an external field applied to 452°C for the particles formed under a 0.25 T magnetic field, which indicates that external magnetic fields can improve the occupancy of magnetic ions and then increase the superexchange interaction. This was confirmed by electron paramagnetic resonance and Mössbauer spectrum analysis. The results present in this paper suggest that in addition to oxygen defects, surface non-magnetic layer and a fraction of finer particles in the superparamagnetic range, cation vacancies should be responsible for the decreasing of saturation magnetization in magnetic nanoparticles.