36,046 research outputs found
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Observation of Electromagnetic Dalitz Decays to , and
No full textUsing a sample of about 10^{10} J/ψ events collected at a center-of-mass energy sqrt[s]=3.097 GeV with the BESIII detector, the electromagnetic Dalitz decays J/ψ→e^{+}e^{-}π^{+}π^{-}η^{'}, with η^{'}→γπ^{+}π^{-} and η^{'}→π^{+}π^{-}η, have been studied. The decay J/ψ→e^{+}e^{-}X(1835) is observed with a significance of 15σ, and also an e^{+}e^{-} invariant-mass dependent transition form factor of J/ψ→e^{+}e^{-}X(1835) is presented for the first time. The intermediate states X(2120) and X(2370) are also observed in the π^{+}π^{-}η^{'} invariant-mass spectrum with significances of 5.3σ and 7.3σ. The corresponding product branching fractions for J/ψ→e^{+}e^{-}X, X→π^{+}π^{-}η^{'} [X=X(1835), X(2120), and X(2370)] are reported
Observation of X(2370) and search for X(2120) in J/ ψ→ γKK ̄ η′
No full textUsing a sample of 1.31×109J/ψ events collected with the BESIII detector, we perform a study of J/ ψ→ γKK ̄ η′. X(2370) is observed in the KK ̄ η′ invariant-mass distribution with a statistical significance of 8.3 σ. Its resonance parameters are measured to be M=2341.6±6.5(stat.)±5.7(syst.)MeV/c2 and Γ=117±10(stat.)±8(syst.)MeV. The product branching fractions for J/ ψ→ γX(2370) , X(2370) → K+K-η′ and J/ψ→γX(2370),X(2370)→KS0KS0η′ are determined to be (1.79±0.23(stat.)±0.65(syst.))×10-5 and (1.18±0.32(stat.)±0.39(syst.))×10-5, respectively. No evident signal for X(2120) is observed in the KK ̄ η′ invariant-mass distribution. The upper limits for the product branching fractions of B(J/ ψ→ γX(2120) → γK+K-η′) and B(J/ψ→γX(2120)→γKS0KS0η′) are determined to be 1.49 × 10 - 5 and 6.38 × 10 - 6 at the 90% confidence level, respectively
Observation of J /? Electromagnetic Dalitz Decays to X (1835), X (2120), and X (2370)
No full textAbstract: Using a sample of about 1010 J/? events collected at a center-of-mass energy s=3.097 GeV with the BESIII detector, the electromagnetic Dalitz decays J/??e+e-?+?-??, with ?????+?- and ????+?-?, have been studied. The decay J/??e+e-X(1835) is observed with a significance of 15?, and also an e+e- invariant-mass dependent transition form factor of J/??e+e-X(1835) is presented for the first time. The intermediate states X(2120) and X(2370) are also observed in the ?+?-?? invariant-mass spectrum with significances of 5.3? and 7.3?. The corresponding product branching fractions for J/??e+e-X, X??+?-?? [X=X(1835), X(2120), and X(2370)] are reported. © 2022 authors. Published by the American Physical Society. 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
Search for X (1870) via the decay J/ψ →ωK+K-η
No full textUsing a sample of (10087±44)×106 J/ψ events collected by the BESIII detector at the BEPCII collider, we search for the decay X(1870)→K+K-η via the J/ψ→ωK+K-η process for the first time. No significant X(1870) signal is observed. The upper limit on the branching fraction of the decay J/ψ→ωX(1870)→ωK+K-η is determined to be 9.55×10-7 at the 90% confidence level. In addition, the branching faction B(J/ψ→ωK+K-η) is measured to be (3.33±0.02(stat)±0.12(syst))×10-4
Search for the X (2370) and observation of eta(c) -> eta eta eta ' in J/psi -> gamma eta eta eta '
No full textUsing a sample of 1.31×109 J/ψ events collected with the BESIII detector, we perform a study of J/ψ→γηηη′ to search for the X(2370) and ηc in the ηηη′ invariant mass distribution. No significant signal for the X(2370) is observed, and we set an upper limit for the product branching fraction of B(J/ψ→γX(2370)·B(X(2370)→ηηη′)<9.2×10-6 at the 90% confidence level. A clear ηc signal is observed for the first time, yielding a product branching fraction of B(J/ψ→γηc)·B(ηc→ηηη′)=(4.86±0.62(stat)±0.45(sys))×10-5
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Measurement of the branching fraction of J /ψ →ωη′π+π- and search for J /ψ →ωX (1835), X (1835) →η′π+π- decay
No full textUsing a sample of 1.31 x 10(9) J/psi events collected by the BESIII detector at BEPCII during 2009 and 2012, we study the J/psi -> omega eta'pi(+)pi(-) thorn p-hadronic process. For the first time, we measure the branching ratio B(J/psi -> omega eta'pi(+)pi(-)) = (1.12 +/- 0.02 +/- 0.13) x 10(-3). We search for the X(1835) state in the eta'pi(+)pi(-) invariant mass spectra. No evidence is found and we estimate the upper limit on the branching fraction at 90% confidence level to be B(J/psi -> omega X(1835), X(1835) -> eta'pi(+)pi(-)) < 6.2 x 10(-5)
Development of metacage for noise control and natural ventilation in a window system
No full textVentilation window is one of the critical elements in sustainable building development, although frequently, outdoor factors such as environmental noise can limit their use. It is necessary to develop windows with both natural ventilation and noise mitigation functions. Acoustic Metamaterials (AMMs) set a new trend in solving physical challenges related to sound wave control, which can find their applications in ventilation window. This study presents a design based on acoustic metacage concept to enhance the window’s natural ventilation and acoustic performance. Finite Element Method (FEM) is used to study and optimise the acoustic performance of the metacage window. The ventilation is evaluated at the same time following predefined guidelines related to the window’s opening ratio and air-flow directivity. The metacage window structure finally, reduces the noise transmission with a mean value of 30 dB within a frequency range of 350–5000 Hz and has an opening ratio of the 33% compared to the whole system surface. The front panel gives a mean high frequencies TL contribution of 17 dB (2000–5000 Hz). Additional lateral constraint and cavities increase the TL performance up to 70% on a wider lower frequency range (350–5000 Hz). Thanks to the cavities, the resonant unit cells among the acoustic metasurface (AMS) significantly suppress sound from exiting the structure in broadband frequencies and allow bigger opening on the lateral side. This significantly contributes to the natural ventilation potential of the metacage window, which in the long term, becomes equally effective to the conventional open windows
Determination of Spin-Parity Quantum Numbers of X (2370) as 0-+ from J/ψ →γ KS0 KS0 η′
No full textBased on (10087±44)×10^{6} J/ψ events collected with the BESIII detector, a partial wave analysis of the decay J/ψ→γK_{S}^{0}K_{S}^{0}η^{'} is performed. The mass and width of the X(2370) are measured to be 2395±11(stat)_{-94}^{+26}(syst) MeV/c^{2} and 188_{-17}^{+18}(stat)_{-33}^{+124}(syst) MeV, respectively. The corresponding product branching fraction is B[J/ψ→γX(2370)]×B[X(2370)→f_{0}(980)η^{'}]×B[f_{0}(980)→K_{S}^{0}K_{S}^{0}]=(1.31±0.22(stat)_{-0.84}^{+2.85}(syst))×10^{-5}. The statistical significance of the X(2370) is greater than 11.7σ and the spin parity is determined to be 0^{-+} for the first time. The measured mass and spin parity of the X(2370) are consistent with the predictions of the lightest pseudoscalar glueball
Dielectric and non-ohmic properties of BixNa1-xNb2O5.5+x ceramics
No full textA series of BixNa1-xNb2O5.5+x (0.3 <= x <= 0.7) samples were prepared by solid state reaction method and their structures, electric field-current density (E-J) relationship and dielectric properties were investigated. It was found that the main phase of Bi0.4Na0.6Nb2O5.9 is tungsten bronze structure and the content of tungsten bronze structure phase decreases with increasing Bi content (x). The sample with Bi content (x) around 0.5 shows nonlinear E-J characteristic. Dielectric result shows that Bi0.5Na0.5Nb2O6 is a relaxor type material, and the breakdown field and nonlinear coefficient decrease with increasing temperature. The nonlinear coefficient (alpha) of 24.8 and dielectric constant of 5.0 x 10(5) (1 kHz) at 225 degrees C suggest that Bi0.5Na0.5Nb2O6 is a potential candidate for varistor application at high temperature. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved
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