Temperature measurement of 6He?+? ions confined in a transparent Paul trap

The LPCTrap setup is a transparent Paul trap dedicated to the measurement of the ???C?? correlation coefficient a _?|? in the ?? decay of trapped radioactive nuclides. In a first experiment, the system has been used to record ??10⁵ coincidences between the ?? particles and recoiling ions emitted from the decay of ⁶He^?+? ions. The analysis of the collected data has already shown that the size of the ⁶He^?+? ion cloud confined in the Paul trap is a critical parameter, potentially limiting the accuracy on the a _?|? measurement. We report here the precise determination of the trapped ion cloud temperature and size. This was performed by extracting the trapped ions toward a position sensitive micro channel plate detector at different phases of the RF driving field. We find a temperature T _exp ?= 0.107(7) eV, consistent with the temperature values inferred using two other observables but 20% higher than the temperature T _sim ?= 0.09 eV predicted by realistic simulations of the ions interacting with the H₂ buffer gas.     

Could the GSI decay rate oscillations be observed in a standard electron capture decay experiment?

The electron-capture decay of ¹⁸⁰Re has been investigated to search for oscillations in the decay probability as reported from a recent measurement at GSI, Darmstadt. The production period was kept short compared to the reported oscillation period. No such oscillation was observed, indicating that the reported oscillations would not have been observable in a conventional experiment with radioactive atoms in a solid environment but must have to do with the unique conditions in the GSI experiment where hydrogen-like ions are moving independently in a storage ring and decaying directly by a true two-body decay to a long-lived (ground-)state. Our finding could restrict possible theoretical interpretations of the oscillations.     

Controlled synthesis and analysis of He–H+3 in a 3.7 K ion trap

Complexes of the triatomic hydrogen ion with helium were synthesised in a low-temperature 22-pole rf ion trap at He number densities of up to 10¹⁶ cm^?3. Absolute ternary rate coefficients for sequentially attaching He atoms have been determined from the growth of complexes with increasing storage time. The number of helium-tagged ions is significantly reduced when increasing the nominal temperature from 4 to 25 K. Competition between attachment and dissociation via collisions leads to stationary He_n–H⁺₃ (n up to 9) distributions. State-specific excitation of the trapped H⁺₃ ions via IR transitions significantly reduces the formation of complexes. Tuning the laser to Δv₂ = 1 transitions in the range of 2726 cm^?1 leads to LIICG lines, i.e., to spectra caused by laser-induced inhibition of complex growth. In addition, almost 100 lines have been found between 2700 and 2765 cm^?1, which are attributed to laser-induced dissociation of the in situ formed He–H⁺₃ complex ions. These lines are not yet assigned; however, their absorption strength, statistics and predissociation lifetimes provide interesting information on both the stable complexes as well as on scattering resonances in low-energy H⁺₃+He collisions. New calculations of the potential energy surface will help to analyse the dissociation spectrum. There are some indications that para-H⁺₃ is enriched under the conditions of the present experiment.     

Is there a spatial correlation in the distribution of adsorbed atoms in the cages of a zeolite?

Monte Carlo simulations of the cage-to-cage jumps of Xe atoms in a crystalline zeolite using the experimentally observed molecular rate constants for cage-to-cage jumps were carried out to determine if there is a systematic spatial correlation of the distributions of Xe atoms among the cages at equilibrium. The neighbours of cages having an Xe occupancy that is less than the average occupancy are found to have distributions that are skewed toward higher occupancy compared with the overall distribution. On the other hand, the neighbours of cages having an Xe occupancy that is greater than the average occupancy are found to have distributions that are skewed toward lower occupancy than the overall distribution.     

Study of the SF 6 − ion lifetime in a rf quadrupole trap

We use an experimental apparatus to study SF ₆ ^– ions lifetimes. These ions are created inside a quadrupole rf trap by charge exchange between highly excited argon atoms and SF₆ molecules. Ions are observed from 200 s up to 15 ms after their creation time. In order to explain experimental results, collisions with SF₆ molecules and the influence of ionized core of argon are taken into account. A part of SF ₆ ^– ions are stabilized by the last influence. These results evidence a radiative stabilization phenomenon, the lifetime of which is estimated at about 5 ms.Equipe de Recherche associée au C.N.R.S. 0898Laboratoire associé au C.N.R.S. 0282     

Differential branching fraction and angular analysis of the decay B0 → K*0 μ+ μ-

The angular distributions and the partial branching fraction of the decay B0 → K*0 μ+ μ- are studied by using an integrated luminosity of 0.37 fb(-1) of data collected with the LHCb detector. The forward-backward asymmetry of the muons, A(FB), the fraction of longitudinal polarization, F(L), and the partial branching fraction dB/dq2 are determined as a function of the dimuon invariant mass. The measurements are in good agreement with the standard model predictions and are the most precise to date. In the dimuon invariant mass squared range 1.00-6.00 GeV2/c4, the results are A(FB)=-0.06(-0.14)(+0.13)±0.04, F(L)=0.55±0.10±0.03, and dB/dq2=(0.42±0.06±0.03)×10(-7) c4/GeV2. In each case, the first error is statistical and the second systematic.     

Energy-charge correlation in the π+π−π0 decay ofK L and of tagged neutral kaons

We relate the asymmetries in the charged pions energy in the decay into π⁺π^?π⁰ ofK _L and of the tagged neutral kaons. The former asymmetry is a given combination of $\Re (\varepsilon ), \Im (\varepsilon )$ , and üε'ü. Moreover, the non-violating CP asymmetry allows a test for the_χ PT predictions within the Zel'dovich approach for the final state interaction.     

Is there a puzzle in the π0→e + e − decay?

We show the importance of precise experimental cuts in π⁰→e ⁺ e ^? decay measurements. Similar cuts have little effect in η(K _L ⁰ )→μ⁺μ^? decays.     

Measurement of the nuclear g-factor of the 1579 keV 3- state of 146Gd using a β-free measurement system

A target heating system which consists of an infrared lamp and quartz rods has been constructed. Using this system, the g-factor of the 1579 keV 3^- state of ¹⁴⁶Gd has been measured to be g(3^-)=+1.14± 22. As a result, the amplitude of the (ν f_{7/2} \otimes 3^-) component admixture in 13/2⁺ state of ¹⁴³Nd is evaluated to be 40± 9%. This revised version was published online in August 2006 with corrections to the Cover Date.     

Production of high energy deuterons in the reaction:3He+3He→4He+2H+e ++v

Experiments on the reaction:³He+³He→⁴He+²He using a single four detector telescope have shown evidence for the production of deuteron pulses, consistent with the²He→²H+e⁺+v fusion reaction in the final state. New measurements on the same reaction using improved techniques viz.A) a windowless³He gas target andB) α- d correlation detection with 5 ns resolving time and antipileup circuitry have been performed. Calibrations were obtained from the⁷Li+³He→²H+⁴He+⁴He reaction spectra. The correlation angles were 30° and 97° for the alphas and deuterons respectively. Deuteron pulses have been observed, correlated with alpha particles. A cross section of (1.7 ±0.5)nbsr^?1MeV^?1 was obtained consistent with previous measurements using a single telescope.     

Microscopic calculations of signals of double beta decay in a Ge detector and first application to the Heidelberg–Moscow experiment

The identification of signals of neutrinoless double beta decay is a question of extreme interest. Starting from the Monte Carlo calculated time history and spatial energy distribution of neutrinoless double beta events, for the first time the expected pulse shapes to be observed in a big ⁷⁶Ge detector have been calculated ‘microscopically  ’, by using the Poisson Superfish code for determination of the field distribution in the detector. It is shown, that for the majority of 0νββ$0\nu \beta \beta$ events it is not possible to differentiate between the contributions of different particle physics parameters entering into the 0νββ$0\nu \beta \beta$ decay process—in the mass mechanism the effective neutrino mass and the right-handed weak current parameters 〈λ〉$〈\lambda 〉$, 〈η〉$〈\eta 〉$. It is shown, that on the other hand it is possible in a ⁷⁶Ge double beta decay experiment to reject a background of larger sizes (high multiplicity) gamma events by selecting low size (low multiplicity) events. First application of the theoretical ββ   pulses to events from the line observed at Q_ββ$Q_{\beta \beta }$ [H.V. Klapdor-Kleingrothaus, I.V. Krivosheina, A. Dietz, et al., Phys. Lett. B 586 (2004) 198; H.V. Klapdor-Kleingrothaus, A. Dietz, I.V. Krivosheina, et al., Nucl. Instrum. Methods A 522 (2004) 371] shows very good agreement. It is shown further, and confirmed by measurements with a collimated source, that a rather good radial position determination of ββ events in the detector is possible. By the same type of calculation it is shown that use of the pulse shapes of the 1592 keV double escape line of the 2614 keV γ-transition from ²²⁸Th for calibrating a neuronal net for search of events of neutrinoless double beta decay can be helpful.     

P-invariance violation in the electrosplitting of6Li∶e− +6Li→e−+D+4He

P-odd polarization phenomena near the threshold of the reaction e^– +⁶Li e^– + D +⁴He, due to the P-odd nuclear forces, are studied in general. The analysis is performed in terms of structure functions and threshold electromagnetic form-factors.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 37–41, May, 1990.     

The radiative decay ϕ → γππ in a coupled-channel model and the structure of f0(980)

A coupled-channel model is used to study the nature of the scalar mesons produced in the decay ϕ → γππ. The K molecular picture of f₀(980) is found to be in a good agreement with the recent experimental data from SND and CMD-2. The structure of the light scalar mesons is elucidated by investigating the S-matrix poles and the q spectral density.