Experimental results on radiative muon capture in complex nuclei

Experimental results for the radiative muon capture branching ratio in several nuclei and the photon-muon spin asymmetry in⁴⁰Ca are reported. For the measurements a two arm Nalspectrometer was used. Apart from²⁶O and⁴⁰Ca, where we confirm previous results of our group, new data on¹²C,²⁶Fe,¹⁶⁵Ho and²⁰⁹Bi are presented. No available theoretical models explain all the data consistently. The preliminary results for the asymmetry measurements, obtained using a stroboscopic method are in agreement with previous measurements and with theoretical calculations.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985.     

(n,t) and (n, α) reactions on 9Be

A metallic ⁹Be target was bombarded with 13.99 MeV neutrons; α-particles, tritons and ⁶He recoil nuclei were detected and identified with a telescope consisting of two proportional counters and a solid state detector. Absolute differential cross sections were measured for the (n, t) reactions leading to the ground state and first excited state of ⁷Li and for the (n, α) reactions leading to the ground state and first excited state of ⁶He. No evidence for higher excited states in ⁶He has been found. An attempt has been made to interpret the observed (n, α) angular distributions in terms of the direct reaction model.     

No pre-critical enhancement observed in 13C(π+, γ)13N(g.s.) at q ≅ 2mπ

The cross section and angular distribution for the reaction ¹³C(π⁺, γ)¹³N(g.s.) have been measured from 37 to 85° in the laboratory, at a pion energy of 115.5 MeV. The observed cross section ranges from 320 to 660 $\text{nb}\text{sr}$. These results do not show the large magnitude and wide-angle peaking expected if pre-critical effects due to nascent pion condensation were present. In addition, the observed cross section is less than one-half of the predictions of available theoretical calculations which do not include the pre-critical effect. Data on the reaction ¹H(π^?, γ)n at T_π = 116.6 MeV were also obtained for calibration purposes. These data agree with expectations based on knowledge of the inverse reaction and previous measurements.     

Microfluidically-unified cell culture, sample preparation, imaging and flow cytometry for measurement of cell signaling pathways with single cell resolution

We have developed a microfluidic platform that enables, in one experiment, monitoring of signaling events spanning multiple time-scales and cellular locations through seamless integration of cell culture, stimulation and preparation with downstream analysis. A combination of two single-cell resolution techniques-on-chip multi-color flow cytometry and fluorescence imaging provides multiplexed and orthogonal data on cellular events. Automated, microfluidic operation allows quantitatively- and temporally-precise dosing leading to fine time-resolution and improved reproducibility of measurements. The platform was used to profile the toll-like receptor (TLR4) pathway in macrophages challenged with lipopolysaccharide (LPS)-beginning with TLR4 receptor activation by LPS, through intracellular MAPK signaling, RelA/p65 translocation in real time, to TNF-α cytokine production, all in one small macrophage population (< 5000 cells) while using minute reagent volume (540 nL/condition). The platform is easily adaptable to many cell types including primary cells and provides a generic platform for profiling signaling pathways.     

Search for the lepton-number-violating decay Xi(-)-->pmu(-)mu(-)

A sensitive search for the lepton-number-violating decay Xi(-)-->pmu(-)mu(-) has been performed using a sample of approximately 10(9) Xi(-) hyperons produced in 800 GeV/c p-Cu collisions. We obtain B(Xi(-)-->pmu(-)mu(-))<4.0x10(-8) at 90% confidence, improving on the best previous limit by 4 orders of magnitude.     

n-n Effective range from the photon spectrum of the reaction π−d→γnn

Notable improvements in the treatment of the reaction π^?d→γnn, extending the validity of the calculation to lower photon energies, permit a new analysis of a high statistics photon spectrum. A precise value of the effective range parameter γ_nn = 2.83 ± 0.11 fm has been obtained. The theoretical uncertainty is 0.11 fm. The value of the scattering length previously extracted from the same spectrum is confirmed, with a_nn = ? 18.6 ± 0.5 fm.     

Generating functions for the affine symplectic group

The generating function notion is used to give a representation of the inhomogeneous symplectic group as group of affine canonical transformations. Then the classical action for linear mechanical systems, the Hamiltonians of which belong to the algebrah sp(2n,R), is deduced; it is explicitely constructed for all the Hamiltonians belonging to some particular subalgebras ofh sp(2n,R). The metaplectic representation ofW Sp(2n,R) onL ²(R) and the solutions of the Schrödinger equation for linear systems are also obtained in terms of generating functions. The Maslov index is explicitly constructed for the quantum corresponding sets of Hamiltonians considered in the classical case.Members of the Centre National de la Recherche Scientifique (France)Recipient of aid from the Ministère de l'Education du Gouvernement du Québec