Double-period zero-order metal gratings as effective selective absorbers

W.-C. Tan, J. Roy Sambles, and T. W. Preist, Physical Review B, Vol. 61, pp. 13177-13182 (2000). "Copyright © 2000 by the American Physical Society."The electromagnetic response of a zero-order metal grating having a primary deep short-period component and a shallow long-period component is modeled. It is found that such a metal grating has an unusual surface-plasmon-polariton band structure and exhibits strong selective absorption of incident radiation. This opens up potential for designing metal surfaces with specific optical response features

Dust environment and dynamical history of a sample of short-period comets: II. 81P/Wild 2 and 103P/Hartley 2

Aims. This paper is a continuation of the first paper in this series, where we presented an extended study of the dust environment of a sample of short-period comets and their dynamical history. On this occasion, we focus on comets 81P/Wild 2 and 103P/Hartley 2, which are of special interest as targets of the spacecraft missions Stardust and EPOXI. Methods. As in the previous study, we used two sets of observational data: a set of images, acquired at Sierra Nevada and Lulin observatories, and the Afρ data as a function of the heliocentric distance provided by the amateur astronomical association Cometas-Obs. The dust environment of comets (dust loss rate, ejection velocities, and size distribution of the particles) was derived from our Monte Carlo dust tail code. To determine their dynamical history we used the numerical integrator Mercury 6.2 to ascertain the time spent by these objects in the Jupiter family Comet region. Results. From the dust analysis, we conclude that both 81P/Wild 2 and 103P/Hartley 2 are dusty comets, with an annual dust production rate of 2.8 × 109 kg yr-1 and (0.4-1.5) × 109 kg yr-1, respectively. From the dynamical analysis, we determined their time spent in the Jupiter family Comet region as ~40 yr in the case of 81P/Wild 2 and ~1000 yr for comet 103P/Hartley 2. These results imply that 81P/Wild 2 is the youngest and the most active comet of the eleven short-period comets studied so far, which tends to favor the correlation between the time spent in JFCs region and the comet activity previously discussed

Study of the production of Λb0\Lambda_b^0 and B‾0\overline{B}^0 hadrons in pppp collisions and first measurement of the Λb0→J/ψpK−\Lambda_b^0\rightarrow J/\psi pK^- branching fraction

The product of the $\Lambda_b^0$ ($\overline{B}^0$) differential production cross-section and the branching fraction of the decay $\Lambda_b^0\rightarrow J/\psi pK^-$ ($\overline{B}^0\rightarrow J/\psi\overline{K}^*(892)^0$) is measured as a function of the beauty hadron transverse momentum, $p_{\rm T}$, and rapidity, $y$. The kinematic region of the measurements is $p_{\rm T}<20~{\rm GeV}/c$ and $2.0<y<4.5$. The measurements use a data sample corresponding to an integrated luminosity of $3~{\rm fb}^{-1}$ collected by the LHCb detector in $pp$ collisions at centre-of-mass energies $\sqrt{s}=7~{\rm TeV}$ in 2011 and $\sqrt{s}=8~{\rm TeV}$ in 2012. Based on previous LHCb results of the fragmentation fraction ratio, $f_{\Lambda_B^0}/f_d$, the branching fraction of the decay $\Lambda_b^0\rightarrow J/\psi pK^-$ is measured to be \begin{equation*} \mathcal{B}(\Lambda_b^0\rightarrow J/\psi pK^-)= (3.17\pm0.04\pm0.07\pm0.34^{+0.45}_{-0.28})\times10^{-4}, \end{equation*} where the first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the branching fraction of the decay $\overline{B}^0\rightarrow J/\psi\overline{K}^*(892)^0$, and the fourth is due to the knowledge of $f_{\Lambda_b^0}/f_d$. The sum of the asymmetries in the production and decay between $\Lambda_b^0$ and $\overline{\Lambda}_b^0$ is also measured as a function of $p_{\rm T}$ and $y$. The previously published branching fraction of $\Lambda_b^0\rightarrow J/\psi p\pi^-$, relative to that of $\Lambda_b^0\rightarrow J/\psi pK^-$, is updated. The branching fractions of $\Lambda_b^0\rightarrow P_c^+(\rightarrow J/\psi p)K^-$ are determined.Comment: 29 pages, 19figures. All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-032.htm

Search for A →μ+μ-Decays

Searches are performed for both promptlike and long-lived dark photons, A, produced in proton-proton collisions at a center-of-mass energy of 13 TeV. These searches look for A→μ+μ-decays using a data sample corresponding to an integrated luminosity of 5.5 fb-1 collected with the LHCb detector. Neither search finds evidence for a signal, and 90% confidence-level exclusion limits are placed on the γ-A kinetic mixing strength. The promptlike A search explores the mass region from near the dimuon threshold up to 70 GeV and places the most stringent constraints to date on dark photons with 21

Updated measurement of decay-time-dependent CP asymmetries in D0 →k+K- A nd D0 →π+π-decays

A search for decay-time-dependent charge-parity (CP) asymmetry in D0→K+K- A nd D0→π+π-decays is performed at the LHCb experiment using proton-proton collision data recorded at a center-of-mass energy of 13 TeV, and corresponding to an integrated luminosity of 5.4 fb-1. The D0 mesons are required to originate from semileptonic decays of b hadrons, such that the charge of the muon identifies the flavor of the neutral D meson at production. The asymmetries in the effective decay widths of D0 and D0 mesons are determined to be AΓ(K+K-)=(-4.3±3.6±0.5)×10-4 and AΓ(π+π-)=(2.2±7.0±0.8)×10-4, where the uncertainties are statistical and systematic, respectively. The results are consistent with CP symmetry and, when combined with previous LHCb results, yield AΓ(K+K-)=(-4.4±2.3±0.6)×10-4 and AΓ(π+π-)=(2.5±4.3±0.7)×10-4. © 2020 CERN. © 2020 CERN, for the LHCb Collaboration. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/" Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3

Measurement of the B-c(-) meson production fraction and asymmetry in 7 and 13 TeV pp collisions

The production fraction of the B − c meson with respect to the sum of B − and ¯ B 0 mesons is measured in both 7 and 13 TeV center-of-mass (c.m.) energy p p collisions produced by the Large Hadron Collider (LHC), using the LHCb detector. The rate, approximately 3.7 per mille, does not change with energy, but shows a transverse momentum dependence. The B − c − B + c production asymmetry is also measured and is consistent with zero within the determined statistical and systematic uncertainties of a few percent

Isospin Amplitudes in Λb0 →J/ψ Λ (ς0) and Ξb0 →J/ψ Ξ0 (Λ) Decays

Ratios of isospin amplitudes in hadron decays are a useful probe of the interplay between weak and strong interactions and allow searches for physics beyond the standard model. We present the first results on isospin amplitudes in b-baryon decays, using data corresponding to an integrated luminosity of 8.5 fb-1, collected with the LHCb detector in pp collisions at center of mass energies of 7, 8, and 13 TeV. The isospin amplitude ratio |A1(Λb0→J/ψς0)/A0(Λb0→J/ψΛ)|, where the subscript on A indicates the final-state isospin, is measured to be less than 1/21.8 at 95% confidence level. The Cabibbo suppressed Ξb0→J/ψΛ decay is observed for the first time, allowing for the measurement |A0(Ξb0→J/ψΛ)/A1/2(Ξb0→J/ψΞ0)|=0.37±0.06±0.02, where the uncertainties are statistical and systematic, respectively. © 2020 CERN. for the LHCb Collaboration

Isospin amplitudes in lambda(0)(b) -> J/psi lambda (Sigma(0)) and Xi(0)(b)-> J/psi Xi(0) (Lambda) decays

Ratios of isospin amplitudes in hadron decays are a useful probe of the interplay between weak and strong interactions and allow searches for physics beyond the standard model. We present the first results on isospin amplitudes in b -baryon decays, using data corresponding to an integrated luminosity of 8.5     fb − 1 , collected with the LHCb detector in p p collisions at center of mass energies of 7, 8, and 13 TeV. The isospin amplitude ratio | A 1 ( Λ 0 b → J / ψ Σ 0 ) / A 0 ( Λ 0 b → J / ψ Λ ) | , where the subscript on A indicates the final-state isospin, is measured to be less than 1 / 21.8 at 95% confidence level. The Cabibbo suppressed Ξ 0 b → J / ψ Λ decay is observed for the first time, allowing for the measurement | A 0 ( Ξ 0 b → J / ψ Λ ) / A 1 / 2 ( Ξ 0 b → J / ψ Ξ 0 ) | = 0.37 ± 0.06 ± 0.02 , where the uncertainties are statistical and systematic, respectively