A search for the rare decays $B^0_s$→$μ$+$μ$- and B0→$μ$+$μ$- is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4 fb-1. An ...excess of $B^0_s$→$μ$+$μ$- decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be $B$($μ$+$μ$-)=(3.0 ± $0.6^{+0.3}_{-0.2}$) × 10-9, where the first uncertainty is statistical and the second systematic. The first measurement of the $B^0_s$→$μ$+$μ$- effective lifetime, τ($B^0_s$→($μ$+$μ$-) = 2.04 ± 0.44 ± 0.05 ps, is reported. No significant excess of B0→($μ$+$μ$- decays is found, and a 95% confidence level upper limit, $B$(B0→($μ$+$μ$-) < 3.4 × 10-10, is determined. All results are in agreement with the standard model expectations.
The $\Xi{^+_c}$$K^-$ mass spectrum is studied with a sample of $pp$ collision data corresponding to an integrated luminosity of 3.3 fb-1, collected by the LHCb experiment. The $\Xi{^+_c}$ is ...reconstructed in the decay mode $pK^-$$π^+$. Five new, narrow excited $Ω_c^0$ states are observed: the $Ω_c$(3000)$^0$, $Ω_c$(3050)$^0$, $Ω_c$(3066)$^0$, $Ω_c$(3090)$^0$, and $Ω_c$(3119)$^0$. Measurements of their masses and widths are reported.
The adsorption of cationic copolymers prepared by the quaternization of poly(4-vinylpyridine) with bromoacetic acid and/or ethyl bromide on the surface of anionic glass microspheres and the stability ...of the as-prepared complexes against dissociation in water-salt solutions are studied. Experiments are performed with the use of two types of copolymers: copolymers carrying cationic and hydrophobic units and copolymers carrying cationic and zwitterionic (electroneutral) units in main chains. For hydrophobic copolymers, the limiting adsorption decreases as the molar fraction of cationic groups in the copolymer, α, increases. In the case of hydrophilic copolymers, the dependence of limiting adsorption on α has a bellshaped pattern with a maximum at α = 0.15 and a horizontal segment at α > 0.4. Hydrophobic copolymers feature irreversible binding with microspheres at α > 0.24; hydrophilic copolymers, at α ≥ 0.15. The obtained data may be used for creation of biocidal polymer coatings and sorption layers that reversibly desorb from the surface with a change in the salt concentration in the surrounding aqueous solution.
The noncovalent immobilization of the protein bovine serum albumin on the surface of spherical nanoparticles 330 ± 60 nm in diameter is described. These nanoparticles are prepared by the thermal ...treatment of tobacco mosaic virus and are preliminarily covered with a layer of the cationic polymer poly(
N
-ethyl-4-vinylpyridinium bromide). The electrostatic adsorption of the polycation on the surface of negatively charged spherical nanoparticles (on average 1.2 × 10
4
macromolecules per particle) is accompanied by recharging of the surface; as a result, the negatively charged protein bovine serum albumin can be adsorbed on it in an amount of 1.7 × 10
4
molecules per particle. The modification of spherical nanoparticles with the polycation and protein does not cause the aggregation of particles. The spherical-nanoparticle-polycation-protein ternary complex demonstrates increased stability in salt solutions relative to the spherical-nanoparticle-polycation binary complex. Because of the simplicity of the method used to modify the surface of spherical nanoparticles, it shows promise for preparation of functionally active complexes.
A search for a long-lived scalar particle χ is performed, looking for the decay B+→K+χ with χ→μ+μ− in pp collision data corresponding to an integrated luminosity of 3 fb−1, collected by the LHCb ...experiment at center-of-mass energies of s=7 and 8 TeV. This new scalar particle, predicted by hidden sector models, is assumed to have a narrow width. The signal would manifest itself as an excess in the dimuon invariant mass distribution over the Standard Model background. No significant excess is observed in the accessible ranges of mass 250<m(χ)<4700 MeV/c2 and lifetime 0.1<τ(χ)<1000 ps. Upper limits on the branching fraction B(B+→K+χ(μ+μ−)) at 95% confidence level are set as a function of m(χ) and τ(χ), varying between 2×10−10 and 10−7. These are the most stringent limits to date. The limits are interpreted in the context of a model with a light inflaton particle.
Aliskiren, an octanamide, is nonpeptide, low molecular weight, orally active renin inhibitor effectively preventing angiotensin and aldosterone release. This drug has been recently approved for the ...treatment of hypertension. Considering potential links between hypertension, platelets, the coagulation cascade and fibrinolysis we sought to evaluate the effect of aliskiren on human biomarkers of hemostasis. In vitro effects of whole blood preincubation with escalating concentrations of aliskiren (500, 1,000 and 2,000 ng ml(-1)) were assessed in 20 aspirin-naive volunteers with multiple risk factors for vascular disease. A total of 33 biomarkers were measured, of which 18 are related to platelet function, 12 to coagulation and 3 to fibrinolysis. Pretreatment of blood samples with aliskiren 500 ng ml(-1) resulted in a significant increase of antithrombin-III (AT-III) activity (P=0.003). All other tested biomarkers were not significantly affected. Spiking whole blood with the higher aliskiren doses was associated with various trends in biomarker activity, where 1000 ng ml(-1) concentration mostly decreased (7/33), and 2,000 ng ml(-1) mostly increased (6/33) some biomarkers. In the therapeutic concentration of 500 ng ml(-1) aliskiren does not affect hemostatic biomarkers, except for a moderate but highly significant (P=0.003) increase of AT-III activity. Higher aliskiren doses were associated with more profound biomarker changes, but they are likely not to be clinically relevant since they show diverging (that is, both mild antiplatelet and platelet-activating) trends, and considering the 2- to 4-fold safety margin. It is suggested that antithrombotic properties of aliskiren be explored further in an ex vivo clinical setting.
Observation of a New Ξ b − Resonance Albrecht, J.; Amerio, S.; d’Argent, P. ...
Physical review letters,
08/2018, Letnik:
121, Številka:
7
Journal Article
Recenzirano
Odprti dostop
From samples of pp collision data collected by the LHCb experiment at s=7, 8 and 13 TeV, corresponding to integrated luminosities of 1.0, 2.0 and 1.5 fb−1, respectively, a peak in both the Λb0K− and ...Ξb0π− invariant mass spectra is observed. In the quark model, radially and orbitally excited Ξb− resonances with quark content bds are expected. Referring to this peak as Ξb(6227)−, the mass and natural width are measured to be mΞb(6227)−=6226.9±2.0±0.3±0.2 MeV/c2 and ΓΞb(6227)−=18.1±5.4±1.8 MeV/c2, where the first uncertainty is statistical, the second is systematic, and the third, on mΞb(6227)−, is due to the knowledge of the Λb0 baryon mass. Relative production rates of the Ξb(6227)−→Λb0K− and Ξb(6227)−→Ξb0π− decays are also reported.
Performance of the CREAM-III Calorimeter Moo Hyun Lee; Ho Seok Ahn; Ganel, O. ...
IEEE transactions on nuclear science,
06/2009, Letnik:
56, Številka:
3
Journal Article
Recenzirano
Cosmic Ray Energetics And Mass (CREAM) is a balloon-borne experiment to directly measure the elemental spectra of protons to iron nuclei with energies up to ~ 10 15 eV. Energies of these cosmic-ray ...particles are measured by an ionization calorimeter comprised of 20 layers of 1 radiation length thick tungsten plates and 20 layers of 0.5 mm diameter scintillating fibers. Each tungsten plate is 500 times 500 times 3.5 mm 3 and the fibers are grouped into fifty 1 cm wide ribbons. After construction, the CREAM-III calorimeter was tested at CERN, the European high energy physics lab, in the H2 beam line of the SPS. Following the CERN test, the calorimeter was integrated into the CREAM-III instrument, and flown successfully in the 3rd flight of the project, during the 2007/8 Antarctic campaign. We present the performance of the CREAM-III calorimeter in lab and beam tests.
Research of the composite materials destruction under extreme pulsed loads is an important task, both for different materials science applications and development of a fundamental understanding of ...the formation and propagation of shock waves in materials with a complex internal structure. In this paper, we present an experimental study of the interaction of a high-current electron beam with a low-modulus polymer material characterized by high elasticity. It has been demonstrated that this effect also causes multiple cracks in the peripheral regions of the sample (∼10 mm in length).
PDF
