Evidence for the h_b(1P) meson in the decay Upsilon(3S) --> pi0 h_b(1P)

Using a sample of 122 million Upsilon(3S) events recorded with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC, we search for the $h_b(1P)$ spin-singlet partner of the P-wave chi_{bJ}(1P) states in the sequential decay Upsilon(3S) --> pi0 h_b(1P), h_b(1P) --> gamma eta_b(1S). We observe an excess of events above background in the distribution of the recoil mass against the pi0 at mass 9902 +/- 4(stat.) +/- 2(syst.) MeV/c^2. The width of the observed signal is consistent with experimental resolution, and its significance is 3.1sigma, including systematic uncertainties. We obtain the value (4.3 +/- 1.1(stat.) +/- 0.9(syst.)) x 10^{-4} for the product branching fraction BF(Upsilon(3S)-->pi0 h_b) x BF(h_b-->gamma eta_b).Comment: 8 pages, 4 postscript figures, submitted to Phys. Rev. D (Rapid Communications

Measurement of the Top Pair Production Cross Section in the Dilepton Decay Channel in ppbar Collisions at sqrt s = 1.96 TeV

Submitted to Phys. Rev. DA measurement of the \ttbar production cross section in \ppbar collisions at $\sqrt{{\rm s}}$ = 1.96 TeV using events with two leptons, missing transverse energy, and jets is reported. The data were collected with the CDF II Detector. The result in a data sample corresponding to an integrated luminosity 2.8 fb$^{-1}$ is: \sigma_{\ttbar} = 6.27 $\pm$ 0.73(stat) $\pm$ 0.63(syst) $\pm$ 0.39(lum) pb. for an assumed top mass of 175 GeV/$c^{2}$.A measurement of the tt̅ production cross section in pp̅ collisions at √s=1.96  TeV using events with two leptons, missing transverse energy, and jets is reported. The data were collected with the CDF II detector. The result in a data sample corresponding to an integrated luminosity 2.8  fb-1 is σtt̅ =6.27±0.73(stat)±0.63(syst)±0.39(lum)  pb. for an assumed top mass of 175  GeV/c2.Peer reviewe

L'Air : revue mensuelle : organe de la Ligue nationale populaire de l'aviation

octobre 19421942/10 (N523)-1942/10

Epitaxial crystallization of insulin on an ordered 2D polymer template

Two-dimensional polymers (2DP) are a new class of materials that consist of a monolayer of ordered molecular building blocks, which have been covalently linked. One of these monomers was self-assembled on a flat muscovite mica scaffold and subsequently the organic layer was polymerized. The resulting flat and stable 2DP layer was used as a template for protein crystallization. Crystals of insulin were epitaxially grown on the template, whereas insulin crystals grown on clean muscovite mica had a random orientation. The template was selective, considering that no epitaxially ordered crystals formed of hen egg white lysozyme, bovine serum albumin, or talin

The Crystalline Sponge Method in Water

The crystalline sponge method entails the elucidation of the (absolute) structure of molecules from a solution phase using single-crystal X-ray diffraction and eliminates the need for crystals of the target compound. An important limitation for the application of the crystalline sponge method is the instability of the available crystalline sponges that can act as host crystals. The host crystal that is most often used decomposes in protic or nucleophilic solvents or when guest molecules with Lewis basic substituents are introduced. Here we disclose a new class of (water) stable host crystals based on f-block metals. We show that these hosts not only increase the scope of the crystalline sponge method to a wider array of solvents and guests, but that they can even be applied to aqueous solutions containing hydrophilic guest molecules, thereby extending the crystalline sponge method to the important field of water-based chemistry

Solid–Liquid Interface Structure of Muscovite Mica in SrCl 2

International audienceThe structure of the solid-liquid interface formed by muscovite mica in contact with two divalent ionic solutions (SrCl2 and BaCl2) is determined using in situ surface X-ray diffraction using both specular and non-specular crystal truncation rods. The 0.5 monolayer of monovalent potassium present at the surface after cleavage is replaced by approximately 0.25 monolayer of divalent ions, closely corresponding to ideal charge compensation within the Stern layer in both cases. The adsorption site of the divalent ions is determined to be in the surface ditrigonal cavities with minor out-of-plane relaxations that are consistent with their ionic radii. The divalent ions are adsorbed in a partly hydrated state (partial solvation sphere). The liquid ordering induced by the presence of the highly ordered crystalline mica is limited to the first 8-10 angstrom from the topmost crystalline surface layer. These results partly agree with previous studies in terms of interface composition, but there are significant differences regarding the structural details of these interfaces

The structure of PbCl2 on the {100} surface of NaCl and its consequences for crystal growth

Contains fulltext : 191022.pdf (publisher's version ) (Open Access)6 p

Muscovite mica as a growth template of PC61BM crystallites for organic photovoltaics

Controlling the microscopic organization of active components is crucial for the performance of organic photovoltaic (OPV) cells. In this work, (001) muscovite mica was used as a growth template to study the formation of PCBM crystallites in the active layer structure of OPV cells. The structures were spin-coated from a PCBM:P3HT solution and subsequently annealed. The parameter range to produce layers with high surface density of (sub)micrometer sized PCBM crystallites was significantly larger for mica than for other substrates. The enhanced PCBM nucleation is attributed to an epitaxial relation between the mica surface and PCBM, which was found to crystallise in a hexagonal crystal structure. Through a float-off procedure, the active layer was transferred from the mica substrate to a conductive substrate, which formed the basis of the transferred inverted solar cell. A power conversion efficiency of 2.1% was obtained for this transferred device, which with a 22% higher short-circuit current density outperforms its conventional counterpart that was directly produced on the conductive substrate. A set-up for simultaneous laser beam induced current (LBIC) and surface reflection analysis revealed that the increased current density originates from large circular areas with a radius of about 10 μm around the PCBM crystallites

Muscovite mica as a growth template of PC61BM crystallites for organic photovoltaics

Controlling the microscopic organization of active components is crucial for the performance of organic photovoltaic (OPV) cells. In this work, (001) muscovite mica was used as a growth template to study the formation of PCBM crystallites in the active layer structure of OPV cells. The structures were spin-coated from a PCBM:P3HT solution and subsequently annealed. The parameter range to produce layers with high surface density of (sub)micrometer sized PCBM crystallites was significantly larger for mica than for other substrates. The enhanced PCBM nucleation is attributed to an epitaxial relation between the mica surface and PCBM, which was found to crystallise in a hexagonal crystal structure. Through a float-off procedure, the active layer was transferred from the mica substrate to a conductive substrate, which formed the basis of the transferred inverted solar cell. A power conversion efficiency of 2.1% was obtained for this transferred device, which with a 22% higher short-circuit current density outperforms its conventional counterpart that was directly produced on the conductive substrate. A set-up for simultaneous laser beam induced current (LBIC) and surface reflection analysis revealed that the increased current density originates from large circular areas with a radius of about 10 μm around the PCBM crystallites