Electromagnetic Decay Research Articles

Enhanced luminescence properties of Eu3+-doped high silica glass by Ag nanoparticles

Eu3+ and Ag nanoparticles (Ag-NPs) doped high silica glass (HSG) was synthesized by absorbing and sintering porous glass. The effect of localized surface plasmon resonance (LSPR) of Ag-NPs on absorbance, luminescence properties and decay curves was investigated. The results indicate that Ag-NPs are effectively doped into HSG. The surface plasmon coupling can be formed between the Eu3+ ions and the Ag-NPs surface because the broad absorption band of Ag-NPs overlaps with the excitation peaks of Eu3+. The profiles of the excitation and emission spectra were not affected by Ag-NPs. By optimizing the Ag concentration, the emission intensity and quantum yield (QY) of HSG-Eu3+-0.1%Ag are significantly higher than those of HSG-Eu3+. Plasmon-enhanced luminescence can occur through enhancement of local electromagnetic field and radiative decay rate.

Lifetime of the recently identified 10+ isomeric state at 3279 keV in the Nd136 nucleus

Background: The γ softness of 136Nd makes it possible to study the shape changes induced by two-proton or two-neutron excitation. Purpose: We measure the lifetimes of two-quasiparticle states of the bands based on the 10+ states at 3296 and 3279 keV to investigate the shape change induced by the alignment of two protons or two neutrons in the h11/2 orbital. Methods: The recoil-distance Doppler shift method was used for the study of 136Nd studies, which was formed by the fusion reaction 120Sn(20Ne, 4n)136Nd, at Ebeam = 85 MeV. Calculations were performed within the microscopic-macroscopic approach, based on the deformed Woods-Saxon single-particle potential and the Yukawa-plus-exponential macroscopic energy. Results: The lifetime of the 10+ state at 3279 keV of 136Nd was measured to be T 10+1/2 = 1.63(9) ns. The lifetimes of the 2+ state at 374 keV and of the 12+ state at 3686 keV of the ground band were also measured to be T 2+1/2 = 26.5(14) ps and T 12+1/2 = 22.5(14) ps. Conclusions: The measured lifetime of 10+ the state at 3279 keV together with other observables confirm the structure change in 136Nd. A rather small reduced hindrance of the electromagnetic decay of the 10+ state at 3279 keV would be consistent with its K-mixed character.

Decay properties of the level in 96Mo

The first excited level of 96Mo was investigated in a high-statistics experiment using the 95Mo(n, γγ) cold neutron capture reaction. The measurements used the high cold neutron flux from the research reactor at Institut Laue-Langevin and employed the highly-efficient EXILL array to detect γ-ray coincidences. The recorded statistics allow identification of decay branches with only a small relative intensity including the E3 decay. With the knowledge of the newly measured branching ratio and the known transition probability, the lifetime of the level was determined and, subsequently, the strength of the other decay branches of the octupole phonon were calculated. The extracted electromagnetic decay strengths are compared to the systematics of the stable even–even molybdenum isotopes and values calculated in a Skyrme-force based quasiparticle random phase approximation and in a cluster approach. Additionally, the decay branch to the low-lying quadrupole isovector level was observed.

An estimate of the inclusive branching ratio to [formula omitted] in Ξbbq decay

We estimate the branching ratio for the inclusive decays Ξbbq→B¯c(⁎)+Xc,s,q to be approximately 1%. Our estimate is performed using non-relativistic potential quark model methods that are appropriate if the bottom and charm quarks are heavy compared to the strong interaction scale. Here the superscript (⁎) denotes that we are summing over spin zero B¯c and spin one B¯c⁎ mesons and the subscript q denotes a light quark. Our approach treats the two bottom quarks in the baryon Ξbbq as a small color anti-triplet. This estimate for the inclusive branching ratio to B¯c and B¯c⁎ mesons also holds for decays of the lowest lying Tbbq¯q¯ tetraquark states, provided they are stable against strong and electromagnetic decay.

Measurement of the phase between strong and electromagnetic amplitudes of J/ψ decays

Using 16 energy points of e+e− annihilation data collected in the vicinity of the J/ψ resonance with the BESIII detector and with a total integrated luminosity of around 100pb−1, we study the relative phase between the strong and electromagnetic amplitudes of J/ψ decays. The relative phase between J/ψ electromagnetic decay and the continuum process (e+e− annihilation without the J/ψ resonance) is confirmed to be zero by studying the cross section lineshape of μ+μ− production. The relative phase between J/ψ strong and electromagnetic decays is then measured to be (84.9±3.6)∘ or (−84.7±3.1)∘ for the 2(π+π−)π0 final state by investigating the interference pattern between the J/ψ decay and the continuum process. This is the first measurement of the relative phase between J/ψ strong and electromagnetic decays into a multihadron final state using the lineshape of the production cross section. We also study the production lineshape of the multihadron final state ηπ+π− with η→π+π−π0, which provides additional information about the phase between the J/ψ electromagnetic decay amplitude and the continuum process. Additionally, the branching fraction of J/ψ→2(π+π−)π0 is measured to be (4.73±0.44)% or (4.85±0.45)%, and the branching fraction of J/ψ→ηπ+π− is measured to be (3.78±0.68)×10−4. Both of them are consistent with the world average values. The quoted uncertainties include both statistical and systematic uncertainties, which are mainly caused by the low statistics.

Hyperbolic Meta-Antennas Enable Full Control of Scattering and Absorption of Light.

We introduce a novel concept of hybrid metal-dielectric meta-antenna supporting type II hyperbolic dispersion, which enables full control of absorption and scattering of light in the visible/near-infrared spectral range. This ability lies in the different nature of the localized hyperbolic Bloch-like modes excited within the meta-antenna. The experimental evidence is corroborated by a comprehensive theoretical study. In particular, we demonstrate that two main modes, one radiative and one non-radiative, can be excited by direct coupling with the free-space radiation. We show that the scattering is the dominating electromagnetic decay channel, when an electric dipolar mode is induced in the system, whereas a strong absorption process occurs when a magnetic dipole is excited. Also, by varying the geometry of the system, the relative ratio of scattering and absorption, as well as their relative enhancement and/or quenching, can be tuned at will over a broad spectral range, thus enabling full control of the two channels. Importantly, both radiative and nonradiative modes supported by our architecture can be excited directly with far-field radiation. This is observed to occur even when the radiative channels (scattering) are almost totally suppressed, thereby making the proposedarchitecture suitable for practical applications. Finally, the hyperbolic meta-antennas possess both angular and polarization independent structural integrity, unlocking promising applications as hybrid meta-surfaces or as solvable nanostructures.

B¯(*)B¯(*) interactions in chiral effective field theory

In this work, the intermeson interactions of double-beauty $\bar{B}\bar{B}$, $\bar{B}\bar{B}^\ast$, and $\bar{B}^\ast\bar{B}^\ast$ systems have been studied with heavy meson chiral effective field theory. The effective potentials are calculated with Weinberg's scheme up to one-loop level. At the leading order, four body contact interactions and one pion exchange contributions are considered. In addition to two pion exchange diagrams, we include the one-loop chiral corrections to contact terms and one pion exchange diagrams at the next-to-leading order. The behaviours of effective potentials both in momentum space and coordinate space are investigated and discussed extensively. We notice the contact terms play important roles in determining the characteristics of the total potentials. Only the potentials in $I(J^P)=0(1^+)$ $\bar{B}\bar{B}^\ast$ and $\bar{B}^\ast\bar{B}^\ast$ systems are attractive, and the corresponding binding energies in these two channels are solved to be $\Delta E_{\bar{B}\bar{B}^\ast}\simeq -12.6^{+9.2}_{-12.9}$ MeV and $\Delta E_{\bar{B}^\ast\bar{B}^\ast}\simeq -23.8^{+16.3}_{-21.5}$ MeV, respectively. The masses of $0(1^+)$ $\bar{B}\bar{B}^\ast$ and $\bar{B}^\ast\bar{B}^\ast$ states lie above the threshold of their electromagnetic decay modes $\bar{B}\bar{B}\gamma$ and $\bar{B}\bar{B}\gamma\gamma$, and thus they can be reconstructable via electromagnetic interactions. Our calculation not only provides some useful information to explore exotic doubly-bottomed molecular states for future experiments, but also is helpful for the extrapolations of Lattice QCD simulations.

Weak decays of the axial-vector tetraquark Tbb;u¯d¯−

The weak decays of the axial-vector tetraquark $T_{bb;\bar{u} \bar{d}}^{-}$ to the scalar state $Z_{bc;\bar{u} \bar{d}}^{0}$ are investigated using the QCD three-point sum rule approach. In order to explore the process $T_{bb; \bar{u} \bar{d}}^{-} \to Z_{bc;\bar{u} \bar{d}}^{0}l \bar{\nu_l}$, we recalculate the spectroscopic parameters of the tetraquark $T_{bb;\bar{u} \bar{d}}^{-}$ and find the mass and coupling of the scalar four-quark system $Z_{bc;\bar{u} \bar{d}}^{0}$, which are important ingredients of calculations. The spectroscopic parameters of these tetraquarks are computed in the framework of the QCD two-point sum rule method by taking into account various condensates up to dimension ten. The mass of the $T_{bb;\bar{u} \bar{ d}}^{-}$ state is found to be $m=(10035~\pm 260)~\mathrm{MeV}$, which demonstrates that it is stable against the strong and electromagnetic decays. The full width $\Gamma$ and mean lifetime $\tau$ of $T_{bb;\bar{u} \bar{d} }^{-}$ are evaluated using its semileptonic decay channels $T_{bb; \bar{u} \bar{d}}^{-} \to Z_{bc;\bar{u} \bar{d}}^{0}l \bar{\nu_l}$, $l=e,\mu$ and $\tau$. The obtained results, $\Gamma=(7.17\pm 1.23)\times 10^{-8\ \ } \mathrm{MeV}$ and $\tau =9.18_{-1.34}^{+1.90}~\mathrm{fs}$, can be useful for experimental investigations of the doubly-heavy tetraquarks.

Measurement of B(J/ψ→η′e+e−) and search for a dark photon

Using a data sample of $(1310.6\pm7.0)\times10^{6}$ $J/\psi$ decay events collected with the BESIII detector at BEPCII, we study the electromagnetic Dalitz decay $J/\psi \to \eta' e^+e^-$ with two dominant $\eta'$ decay modes, $\eta' \to \gamma \pi^+ \pi^-$ and $\eta' \to \pi^+\pi^-\eta$. The branching fraction is determined to be $\mathcal{B}(J/\psi \to \eta' e^+e^-) = (6.59\pm0.07\pm0.17) \times 10^{-5}$, which improves in precision by a factor of 2 over the previous BESIII measurement. A search for the dark photon ($\gamma '$) is performed via $J/\psi \to\eta' \gamma ', \gamma' \to e^{+}e^{-}$. Excluding the $\omega$ and $\phi$ mass regions, no significant signal is observed in the mass range from 0.1 to 2.1 GeV/$c^{2}$. We set upper limits at the 90\% confidence level on $\mathcal{B}(J/\psi \to \eta' \gamma ')\times\mathcal{B}(\gamma ' \to e^+e^-)$, $\mathcal{B}(J/\psi \to\eta' \gamma'$) and the mixing strength as a function of dark photon mass. This is among the first searches for dark photons in charmonium decays.

Study of the Dalitz decayJ/ψ→e+e−η

We study the electromagnetic Dalitz decay J/ψ→e+e−η and search for dielectron decays of a dark gauge boson (γ′) in J/ψ→γ′η with the two η decay modes η→γγ and η→π+π−π0 using (1310.6±7.0)×106 J/ψ events collected with the BESIII detector. The branching fraction of J/ψ→e+e−η is measured to be (1.43±0.04(stat)±0.06(syst))×10−5, with a precision that is improved by a factor of 1.5 over the previous BESIII measurement. The corresponding dielectron invariant mass dependent modulus square of the transition form factor is explored for the first time, and the pole mass is determined to be Λ=2.84±0.11(stat)±0.08(syst) GeV/c2. We find no evidence of γ′ production and set 90% confidence level upper limits on the product branching fraction B(J/ψ→γ′η)×B(γ′→e+e−) as well as the kinetic mixing strength between the standard model photon and γ′ in the mass range of 0.01≤mγ′≤2.4 GeV/c2.1 MoreReceived 8 October 2018DOI:https://doi.org/10.1103/PhysRevD.99.012006Published by the American Physical Society under the terms of the 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.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasMagnetic momentParticle decaysParticles & Fields

Limits from BBN on light electromagnetic decays

Injection of electromagnetic energy — photons, electrons, or positrons — into the plasma of the early universe can destroy light elements created by primordial Big Bang Nucleosynthesis (BBN). The success of BBN at predicting primordial abundances has thus been used to impose stringent constraints on decay or annihilation processes with primary energies near or above the electroweak scale. In this work we investigate the constraints from BBN on electromagnetic decays that inject lower energies, between 1–100 MeV. We compute the electromagnetic cascade from such injections and we show that it can deviate significantly from the universal spectrum commonly used in BBN calculations. For electron injection below 100 MeV, we find that the final state radiation of photons can have a significant impact on the resulting spectrum relevant for BBN. We also apply our results on electromagnetic cascades to investigate the limits from BBN on light electromagnetic decays prior to recombination, and we compare them to other bounds on such decays.

Study of exotic mesons in pp and AA collisions

The possibility of study of exotic mesons is discussed. The paper includes detailed analysis of strong, weak and electromagnetic decays containing charmed quark-antiquark pair, physics simulation and event reconstruction at NICA.

Status and perspectives of hyperon production and electromagnetic decays with HADES at FAIR

The Hades spectrometer is a versatile detector device operating at the SIS18 synchrotron at GSI Darmstadt with a vital list of results on strangeness production including Λ(1405) and Σ(1385) exclusive production cross-sections, Λ polarization, Λ-p correlation and Kaons in-medium. With the upgrade of the SIS18 synchrotron for the FAIR facility and the upgrade of HADES with a new Forward Detector, the experiment will have an unique opportunity to study also excited hyperon states. Among others, production and electromagnetic decays of excited Λ and Σ hyperons states, Ξ− cascade spectroscopy and - production and correlation are planned. We have studied the reconstruction feasibility using two benchmark channels of Λ(1520) → Λe+e− Dalitz decay and exclusive Ξ− production in pp→Ξ−K+K+p reaction. The Forward Detector consisting of a forward tracker made of PANDA straw tubes prototypes and a RPC time of flight detector will enlarge HADES acceptance to forward angles (0.5-7°), important for Λ tagging. The magnetic field-free forward region will require employment of kinematical refit and neural networks analysis methods to perform particle identification. In this contribution highlights of strangeness production in p-p and p-A reactions will be presented together with perspectives for the future hyperon programme.

Surface Enhanced Raman Spectroscopy for Molecular Identification- a Review on Surface Plasmon Resonance (SPR) and Localised Surface Plasmon Resonance (LSPR) in Optical Nanobiosensing

Surface plasmon resonance (SPR) allows for real-time, label-free optical detection of many chemical and biological substances. Having emerged in the last two decades, it is a widely used technique due to its non-invasive nature, allowing for the ultra-sensitive detection of a number of analytes. This review article discusses the principles, providing examples and illustrating the utility of SPR within the frame of plasmonic nanobiosensing, while making comparisons with its successor, namely localized surface plasmon resonance (LSPR). In particular LSPR utilizes both metal nanoparticle arrays and single nanoparticles, as compared to a continuous film of gold as used in traditional SPR. LSPR, utilizes metal nanoparticle arrays or single nanoparticles that have smaller sizes than the wavelength of the incident light, measuring small changes in the wavelength of the absorbance position, rather than the angle as in SPR. We introduce LSPR nanobiosensing by describing the initial experiments performed, shift-enhancement methods, exploitation of the short electromagnetic field decay length, and single nanoparticle sensors are as pathways to further exploit the strengths of LSPR nanobiosensing. Coupling molecular identification to LSPR spectroscopy is also explored and thus examples from surface-enhanced Raman spectroscopy are provided. The unique characteristics of LSPR nanobiosensing are emphasized and the challenges using LSPR nanobiosensors for detection of biomolecules as a biomarker are discussed.

Feasibility studies of production and electromagnetic decay studies of hyperons for HADES

The spectrum of excited states of single and double strange hyperons is only poorly known. Their internal structure is controversially discussed within quark, bag and molecular models. The most famous example is Λ(1405). In this context radiative decays are predicted to be an ideal tool to discriminate between various predictions. Moreover, Ξ−production yield measured by HADES in Ar+KCl@1.76 GeV andp+Nb@3.5 GeV experiments strongly overshoots theory predictions and calls for more detailed studies in elementary collisions. In our poster we show results of the feasibility studies for the HADES detector of the cascade production close to the threshold and also the radiative decays of the excited hyperon states. Three bench mark channels: $pp \to \Lambda (15020){K^ + }p \to \Lambda {e^ + }{e^ - }{K^ + }p$, $pp \to \Lambda (1405){K^ + }p \to \Lambda {e^ + }{e^ - }{K^ + }p$ and $pp \to \Sigma (1385){K^ + }p \to \Lambda {e^ + }{e^ - }{K^ + }p$, at beam energyEk= 4.5 GeV have been put into extensive simulation studies together with the most significant background channels. We will show the results including expected count rates and signal to background ratios.

Resonance absorption of a broadband laser pulse

Broad bandwidth, infrared light sources have the potential to revolutionize inertial confinement fusion (ICF) by suppressing laser-plasma instabilities. There is, however, a tradeoff: The broad bandwidth precludes high efficiency conversion from the infrared to the ultraviolet, where laser-plasma interactions are weaker. Operation in the infrared could intensify the role of resonance absorption, an effect long suspected to be the shortcoming of early ICF experiments. Here, we present simulations exploring the effect of the bandwidth on resonance absorption. In the linear regime, the bandwidth has little effect on resonance absorption; in the nonlinear regime, the bandwidth suppresses enhanced absorption resulting from the electromagnetic decay instability. These findings evince that, regardless of the bandwidth, an ICF implosion will confront at least linear levels of resonance absorption.

ρ-Meson properties in medium

Properties of ρ-meson in symmetric nuclear matter are investigated in a light-front constituent quark model (LFCQM), using the in-medium inputs calculated by the quark–meson coupling (QMC) model. The LFCQM used in this study was already applied for the studies of the electromagnetic properties of ρ-meson in vacuum, namely, the charge G0, magnetic G1, and quadrupole G2 form factors, electromagnetic charge radius, and electromagnetic decay constant. Using the two different density dependence of the regulator mass in medium, we predict that the charge radius, and quadrupole moment are enhanced as increasing the nuclear matter density, while the magnetic moment is slightly quenched. Furthermore, we predict the value Qzero2, which crosses zero of the charge form factor, G0(Qzero2)=0 (Q2=−q2>0 with q being the four-momentum transfer), decreases as increasing the nuclear matter density by the two different density dependence of the regulator mass. On the other hand, for the electromagnetic decay constant of the ρ-meson, the two different density dependence of the regulator mass predict the opposite density dependence. Namely, as increasing the nuclear matter density, the naive treatment with the density independent regulator mass as in the vacuum, predicts the increase of the decay constant, while the other that assumes the same density dependence of the regulator mass as that of the in-medium constituent quark mass, predicts the decrease of the decay constant. Thus, although the other physical quantities are predicted to have similar density dependence by the two different density dependence of the regulator mass applied, the density dependence of the ρ-meson electromagnetic decay constant is predicted to have opposite density dependence, and the facts suggest that the in-medium ρ-meson decay constant needs to be investigated further in the future.

End-to-End Event Classification of High-Energy Physics Data

Feature extraction algorithms, such as convolutional neural networks, have introduced the possibility of using deep learning to train directly on raw data without the need for rule-based feature engineering. In the context of particle physics, such end-to-end approaches can be used for event classification to learn directly from detector-level data in a way that is completely independent of the high-level physics reconstruction. We demonstrate a technique for building such end-to-end event classifiers to distinguish simulated electromagnetic decays in a high-fidelity model of the CMS Electromagnetic Calorimeter.

Electromagnetic and weak decays of baryons in the unquenched quark model

In this contribution, we discuss the electromagnetic and weak decays of baryons in the unquenched quark model and show that the observed discrepancies between the experimental data and the predictions of the constituent quark model can be accounted for in large part by the effects of sea quarks. Finally, the obtained results are discussed in terms of flavor-symmetry breaking.

Hindered α decays of heaviest high- K isomers

To find candidates for long-lived high-$K$ isomers in even-even $Z=106\text{--}112$ superheavy nuclei, we study dominant $\ensuremath{\alpha}$-decay channels of two- and four-quasiparticle configurations at a low excitation. Energies are calculated within the microscopic-macroscopic approach with the deformed Woods-Saxon potential. Configurations are fixed by a standard blocking procedure and their energy found by a subsequent minimization over deformations. Different excitation energies of a high-$K$ configuration in parent and daughter nucleus seem particularly important for hindrance of the $\ensuremath{\alpha}$ decay. A strong hindrance is found for some four-quasiparticle states, particularly ${K}^{\ensuremath{\pi}}={20}^{+}$ and/or ${19}^{+}$ states in $^{264\text{--}270}\mathrm{Ds}$. Contrary to what was suggested in experimental papers, it is rather a proton configuration that leads to this strong hindrance. If not shortened by the electromagnetic decay, $\ensuremath{\alpha}$ half-lives of $\ensuremath{\sim}1\phantom{\rule{0.28em}{0ex}}\mathrm{s}$ could open new possibilities for studies of chemical/atomic properties of related elements.