90 research outputs found
Hydrodynamic force measurements under precisely controlled conditions: Correlation of slip parameters with the mean free path
No full textA customized atomic forcemicroscope has been utilized in dynamic mode to measure
hydrodynamic forces between a sphere and a flat plate, both coated with gold. In
order to study the influence of the mean free path on slippage without systematic
errors due to varying surface properties, all data have been acquired at precisely
the same spot on the plate. Local accommodation coefficients and slip lengths have
been extracted from experimental data for He, Ne, Ar, Kr, as well as N2, CO2, and
C2H6, at Knudsen numbers between 3 × 10−4 and 3. We found that slippage is
effectively suppressed if the mean free path of the fluid is lower than the roughness
amplitude on the surface, while we could not observe a clear correlation between
the accommodation coefficient and the molecular mass
Ferrule-top cantilever optical fiber sensor for velocity measurements of low speed air flows
No full textNumerical and experimental characterization of a ferrule-top cantilever optical fiber sensor for flow velocity measurements
No full textExplaining , and in a two-Higgs-doublet model with gauged
No full textThe LHC observed so far three deviations from the Standard Model (SM) predictions in flavour observables: LHCb reported anomalies in and while CMS found an excess in . We show, for the first time, how these deviations from the SM can be explained within a single well-motivated model: a two-Higgs-doublet model with gauged symmetry. We find that, despite the constraints from and -- mixing, one can explain , and simultaneously, obtaining interesting correlations among the observables.The LHC has observed, so far, 3 deviations from the Standard Model (SM) predictions in flavor observables: LHCb reported anomalies in B→K*μ+μ- and R(K)=B→Kμ+μ-/B→Ke+e-, while CMS found an excess in h→μτ. We show, for the first time, how these deviations from the SM can be explained within a single well-motivated model: a two-Higgs-doublet model with gauged Lμ-Lτ symmetry. We find that, despite the constraints from τ→μμμ and Bs-B¯s mixing, one can explain h→μτ, B→K*μ+μ- and R(K) simultaneously, obtaining interesting correlations among the observables.The LHC observed so far three deviations from the Standard Model (SM) predictions in flavour observables: LHCb reported anomalies in and while CMS found an excess in . We show, for the first time, how these deviations from the SM can be explained within a single well-motivated model: a two-Higgs-doublet model with gauged symmetry. We find that, despite the constraints from and -- mixing, one can explain , and simultaneously, obtaining interesting correlations among the observables
Unbroken B–L symmetry
No full textAbstractThe difference between baryon number B and lepton number L is the only anomaly-free global symmetry of the Standard Model, easily promoted to a local symmetry by introducing three right-handed neutrinos, which automatically make neutrinos massive. The non-observation of any (B–L)-violating processes leads us to scrutinize the case of unbroken gauged B–L; besides Dirac neutrinos, the model contains only three parameters, the gauge coupling strength g′, the Stückelberg mass MZ′, and the kinetic mixing angle χ. The new force could manifest itself at any scale, and we collect and derive bounds on g′ over the entire testable range MZ′=0–1013 eV, also of interest for the more popular case of spontaneously broken B–L or other new light forces. We show in particular that successful Big Bang nucleosynthesis provides strong bounds for masses 10 eV<MZ′<10 GeV due to resonant enhancement of the rate f¯f↔ν¯RνR. The strongest limits typically arise from astrophysics and colliders, probing scales MZ′/g′ from TeV up to 1010 GeV
Numerical study of a ferrule-top cantilever optical fiber sensor for wind-tunnel applications and comparison with experimental results
No full textWe present a numerical analysis of an air flow velocity sensor based on a fiber-optic ferrule-top cantilever. The device forms a low-finesse Fabry-Perot interferometer, with one of the two reflecting surfaces constituted by a cantilever beam. Under the effect of the flow pressure, the cantilever bends producing a change in the cavity length of the Fabry-Perot and therefore a modification of its optical response. The numerical analysis, performed by use of finite-element method (FEM), is then compared with a set of experimental results obtained in a small wind-tunnel. © 2012 Elsevier B.V
Tritium beta decay with additional emission of new light bosons
No full textWe consider tritium beta decay with additional emission of light pseudoscalar or vector bosons coupling to electrons or neutrinos. The electron energy spectrum for all cases is evaluated and shown to be well estimated by approximated analytical expressions. We give the statistical sensitivity of Katrin to the mass and coupling of the new bosons, both in the standard setup of the experiment as well as for future modifications in which the full energy spectrum of tritium decay is accessible.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Addressing the LHC flavour anomalies with horizontal gauge symmetries
No full textWe study the impact of an additional gauge symmetry with flavour-dependent charges for quarks and leptons on the LHC flavour anomalies observed in , , and . In its minimal version with two scalar doublets, the resulting model naturally explains the deviations from the Standard Model observed in and . The CMS access in can be explained by introducing a third scalar doublet, which gives rise to a prediction for . We investigate constraints from flavour observables and direct LHC searches for . Our model successfully generates the measured fermion-mixing matrices and does not require vector-like fermions, unlike previous attempts to explain these anomalies.We study the impact of an additional U(1)′ gauge symmetry with flavor-dependent charges for quarks and leptons on the LHC flavor anomalies observed in B→K*μ+μ-, R(K)=B→Kμ+μ-/B→Ke+e-, and h→μτ. In its minimal version with two scalar doublets, the resulting model naturally explains the deviations from the Standard Model observed in B→K*μ+μ- and R(K). The CMS access in h→μτ can be explained by introducing a third scalar doublet, which gives rise to a prediction for τ→3μ. We investigate constraints from flavor observables and direct LHC searches for pp→Z′→μ+μ-. Our model successfully generates the measured fermion-mixing matrices and does not require vectorlike fermions, unlike previous attempts to explain these anomalies.We study the impact of an additional gauge symmetry with flavour-dependent charges for quarks and leptons on the LHC flavour anomalies observed in , , and . In its minimal version with two scalar doublets, the resulting model naturally explains the deviations from the Standard Model observed in and . The CMS access in can be explained by introducing a third scalar doublet, which gives rise to a prediction for . We investigate constraints from flavour observables and direct LHC searches for . Our model successfully generates the measured fermion-mixing matrices and does not require vector-like fermions, unlike previous attempts to explain these anomalies
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