Resonant Intermediate State Research Articles

Analysis of three-body decays B→D(V→)PP under the factorization-assisted topological-amplitude approach

Motivated by the accumulated experimental results on three-body charmed B decays with resonance contributions in , LHCb, and Belle (II), we systematically analyze B(s)→D(s)(V→)P1P2 decays with V representing a vector resonance (ρ,K*,ω, or ϕ) and P1,2 as a light pseudoscalar meson (pion or kaon). The intermediate subprocesses B(s)→D(s)V are calculated with the factorization-assisted topological-amplitude (FAT) approach and the intermediate resonant states V described by the relativistic Breit-Wigner distribution successively decay to P1P2 via strong interaction. Taking all lowest resonance states (ρ,K*,ω,ϕ) into account, we calculate the branching fractions of these decay modes as well as the Breit-Wigner-tail effects for B(s)→D(s)(ρ,ω→)KK. Our results agree with the data by , LHCb, and Belle (II). Among the predictions that are still not observed, there are some branching ratios of order 10−6–10−4 which are hopeful to be measured by LHCb and Belle II. Our approach and the perturbative QCD approach (PQCD) adopt the compatible theme to deal with the resonance contributions. What is more, our data for the intermediate two-body charmed B-meson decays in FAT approach are more precise. As a result, our results for branching fractions have smaller uncertainties, especially for color-suppressed emission diagram dominated modes. Published by the American Physical Society 2024

Experimental upper bounds for resonance-enhanced entangled two-photon absorption cross section of indocyanine green.

Resonant intermediate states have been proposed to increase the efficiency of entangled two-photon absorption (ETPA). Although resonance-enhanced ETPA (r-ETPA) has been demonstrated in atomic systems using bright squeezed vacuum, it has not been studied in organic molecules. We investigate for the first time r-ETPA in an organic molecular dye, indocyanine green (ICG), when excited by broadband entangled photons in near-IR. Similar to many reported virtual state mediated ETPA (v-ETPA) measurements, no r-ETPA signals are measured, with an experimental upper bound for the cross section placed at 6(±2) × 10-23 cm2. In addition, the classical resonance-enhanced two-photon absorption (r-TPA) cross section of ICG at 800nm is measured for the first time to be 20(±13) GM, where 1 GM equals 10-50 cm4 s, suggesting that having a resonant intermediate state does not significantly enhance two-photon processes in ICG. The spectrotemporally resolved emission signatures of ICG excited by entangled photons are also presented to support this conclusion.

Normal single-spin asymmetries in electron-proton scattering: Two-photon exchange with intermediate-state resonances

Normal single-spin asymmetries in electron-proton scattering: Two-photon exchange with intermediate-state resonances

Study of the e+e−→ π+π−ω process at center-of-mass energies between 4.0 and 4.6 GeV

Using 15.6 fb−1 of e+e− collision data collected at twenty-four center-of-mass energies from 4.0 to 4.6 GeV with the BESIII detector, the helicity amplitudes of the process e+e− → π+π−ω are analyzed for the first time. Born cross section measurements of two-body intermediate resonance states with statistical significance greater than 5σ are presented, such as f0(500), f0(980), f2(1270), f0(1370), b1(1235)±, and ρ(1450)±. In addition, evidence of a resonance state in e+e− → π+π−ω production is found. The mass of this state obtained by line shape fitting is about 4.2 GeV/c2, which is consistent with the production of ψ(4160) or Y(4220).

Second harmonic generation and two photon absorption assisted power limiting mechanism of l-Phenylalanine (LPA) - poly-ethylene-oxide (PEO) electrospun nanofibers

Nanofibers consisting of organic nonlinear optical l-Phenylalanine (LPA) nanocrystals embedded in poly-ethylene-oxide (PEO) polymer were synthesized by the electrospinning technique. The preferred crystallographic orientation of the organic molecules that crystallized inside the nanofibers was demonstrated through X-ray diffraction and calculations show that the average crystallite size is around 28 nm. SEM images clearly show the formation of smooth fibers with average diameter of 246 nm. The emission of green light from the nanofiber powder sample approved the second harmonic generation (SHG) under the excitation of Nd: YAG laser (1064 nm). Further the generation of second harmonic from the fibers was confirmed by nonlinear microscope imaging and power dependent SHG studies, performed using femtosecond fiber laser (1040 nm). The nonlinear absorption and its power limiting characteristics of LPA-PEO electro-spun nanofibers were studied utilizing the Z-scan method employing Q switched Nd: YAG laser as an excitation source (532 nm, 5 ns, 10 Hz). Open aperture Z-scan measurement (with intensity 1.23 × 1012 W/m2 and 2.4623 × 1012 W/m2) revealed the reverse saturable absorption property of LPA-PEO nanofibers. The existence of a sequential two-photon absorption process involving real resonant intermediate states has been demonstrated by the intensity dependent two-photon absorption coefficient. The usefulness of LPA optical fibers as power limiters is ensured by their lower optical limiting threshold than other optical limiting materials.

Search for resonant and nonresonant production of pairs of dijet resonances in proton-proton collisions at sqrt{s} = 13 TeV

A search for pairs of dijet resonances with the same mass is conducted in final states with at least four jets. Results are presented separately for the case where the four jet production proceeds via an intermediate resonant state and for nonresonant production. The search uses a data sample corresponding to an integrated luminosity of 138 fb−1 collected by the CMS detector in proton-proton collisions at sqrt{s} = 13 TeV. Model-independent limits, at 95% confidence level, are reported on the production cross section of four-jet and dijet resonances. These first LHC limits on resonant pair production of dijet resonances via high mass intermediate states are applied to a signal model of diquarks that decay into pairs of vector-like quarks, excluding diquark masses below 7.6 TeV for a particular model scenario. There are two events in the tails of the distributions, each with a four-jet mass of 8 TeV and an average dijet mass of 2 TeV, resulting in local and global significances of 3.9 and 1.6 standard deviations, respectively, if interpreted as a signal. The nonresonant search excludes pair production of top squarks with masses between 0.50 TeV to 0.77 TeV, with the exception of a small interval between 0.52 and 0.58 TeV, for supersymmetric R-parity-violating decays to quark pairs, significantly extending previous limits. Here, the most significant excess above the predicted background occurs at an average dijet mass of 0.95 TeV, for which the local and global significances are 3.6 and 2.5 standard deviations, respectively.

Dispersion relations for hadronic light-by-light scattering in triangle kinematics

We present a new strategy for the dispersive evaluation of the hadronic light-by-light contribution to the anomalous magnetic moment of the muon aμ. The new approach directly applies in the kinematic limit relevant for aμ: one of the photons is treated as an external electromagnetic field with vanishing momentum, so that the kinematics corresponds to a triangle. We derive expressions for the relevant single-particle intermediate states, as well as the tensor decompositions of the two-pion sub-processes that appear in addition to those needed in the established dispersive approach. The existing approach is based on a set of dispersion relations for the hadronic light-by-light tensor in four-point kinematics. At present it is not known how to consistently include in this framework resonant intermediate states of spin 2 or larger, due to the appearance of kinematic singularities that can be traced back to the redundancy of the tensor decomposition. We show that our new approach circumvents this problem and enables dispersion relations in the limit of triangle kinematics that are manifestly free from kinematic singularities, paving the way towards a data-driven evaluation of all relevant exclusive hadronic intermediate states.

Theory of resonant Raman scattering due to spin flips of resident charge carriers and excitons in perovskite semiconductors

Recently, the double spin-flip Raman scattering with simultaneous spin reversal of nonequilibrium, localized, and long-lived electrons and holes has been observed in semiconductor perovskites. The authors propose as mechanisms responsible for the double spin-flip processes (i) optical excitation of a localized exciton and its exchange interaction with localized particles, (ii) the process involving biexciton as a resonant intermediate state, and (iii) direct excitation of exciton-polaritons and their scattering by localized carriers. The conditions are discussed, under which the efficiency of double and triple spin-flip scattering can be comparable to that of the first-order process.

High-order Gundlach resonances at exceptional large voltages: Consequences for determining work functions

We report a combined experimental and theoretical study of Gundlach resonances Un in scanning tunneling spectroscopy at constant current over an exceptional range of energy and number, typically tens of an eV and over thirty in order n. By performing (1) three-dimensional electrostatic calculations, (2) WKB quantum calculations of the current, and (3) one-dimensional solutions of the Schrödinger equation along the perpendicular line from the surface to the tip apex, we provide a theoretical understanding and prediction of the experimental U(n) curve. Unlike commonly assumed, the triangular potential well is not found to be a good approximation for the high-n states. We show that although the spectroscopy mode assures a constant electric field at the tip apex, this leads only for the intermediate resonance states (approximately 2<n<6) to reside in a linear potential between the tip and the surface. Whereas the low lying (n <6) states all lie approximately in the same quantum well, at higher tip-sample distances d and bias voltages V(d), the quantum well is no longer triangular but attains a curvature, which is d dependent. Each high-n state resides in its own well that can be well-approximated by a polynomial of second order. Hence, the range of Un to be analyzed in terms of spectroscopic positions needs to be chosen with great care when deducing surface work functions.

Weak pion-production and the second resonance region

In this work we report the calculation of the total cross section for pion-production by the dispersion of neutrinos on nucleons. We use a consistent formalism for the intermediate resonance states of spin-$\frac{3}{2}$, taking care on the conditions imposed by the invariance on contact transformations and using the Sachs parametrization for the form factors. In addition, we incorporate states in the second resonance region up to 1.6 GeV and implement different approaches for all the dressed resonance propagators. In addition to the $\mathrm{\ensuremath{\Delta}}(1232)$, we include the ${N}^{*}(1440)$, ${N}^{*}(1535)$, and ${N}^{*}(1520)$ resonance contributions, and it is shown that this inclusion improves the description of the total cross section regarding a model where only the $\mathrm{\ensuremath{\Delta}}(1230)$ resonance is considered. Also, results for antineutrinos are properly described.

Role of D(s)* and their contributions in B(s)→D(s)hh′ decays

We demonstrate the roles of $D_{(s)}^\ast$ and their contributions in the quasi-two-body decays $B_{(s)} \to D_{(s)} h h^\prime$ ($h, h^\prime = \{\pi, K\}$) in the perturbative QCD approach, stemming from the quark flavour changing $\bar{b} \to \bar{c} \, q_2 \, \bar{q}_1$ and $\bar{b} \to c \, \bar{q_1} \, \bar{q_2}$ with $q_1, q_2 = \{s/d, u\}$. The main motivation of this study is the measurements of significant derivations from the simple phase-space model in the channels $B_{(s)} \to D_{(s)} h h^\prime$ at $B$ factories and LHC, which is now clarified as the Breit-Wigner-tail effects from the corresponding intermediate resonant states $D_{(s)}^\ast$. We confirm that these effect from $D^\ast$ is small ($\sim 5\%$) in the quasi-two-body $B_{(s)} \to D \pi \pi (K)$ decaying channels, and predict the tiny ($< 1 \%$) contributions from $D^\ast$ in the $B_{(s)} \to D_s K \pi (K)$ decaying channels, our result for the $B_s \to D K \pi (K)$ decaying channels contributed only from the Breit-Wigner-tail effect of $D_s^\ast$ is in agreement with the current LHCb measurement. We recommend the Belle-II and the LHCb collaborations to restudy the processes $B^+\to \bar D^{\ast 0}\pi^+(K^+) \to D^-\pi^+\pi^+(K^+)$ to reveal the structure of $D^{\ast 0}$ and the strong decay $D^{\ast 0} \to D^+ \pi^-$.

Time-resolved photoelectron imaging of complex resonances in molecular nitrogen.

We have used the FERMI free-electron laser to perform time-resolved photoelectron imaging experiments on a complex group of resonances near 15.38 eV in the absorption spectrum of molecular nitrogen, N2, under jet-cooled conditions. The new data complement and extend the earlier work of Fushitani et al. [Opt. Express 27, 19702-19711 (2019)], who recorded time-resolved photoelectron spectra for this same group of resonances. Time-dependent oscillations are observed in both the photoelectron yields and the photoelectron angular distributions, providing insight into the interactions among the resonant intermediate states. In addition, for most states, we observe an exponential decay of the photoelectron yield that depends on the ionic final state. This observation can be rationalized by the different lifetimes for the intermediate states contributing to a particular ionization channel. Although there are nine resonances within the group, we show that by detecting individual photoelectron final states and their angular dependence, we can identify and differentiate quantum pathways within this complex system.

Finite-width effects in three-body B decays

It is customary to apply the so-called narrow width approximation $\Gamma(B\to RP_3\to P_1P_2P_3)=\Gamma(B\to RP_3)Br(R\to P_1P_2)$ to extract the branching fraction of the quasi-two-body decay $B\to RP_3$, with $R$ and $P_3$ being an intermediate resonant state and a pseudoscalar meson, respectively. However, the above factorization is valid only in the zero width limit. We consider a correction parameter $\eta_R$ from finite width effects. Our main results are: (i) We present a general framework for computing $\eta_R$ and show that it can be expressed in terms of the normalized differential rate and determined by its value at the resonance. (ii) We introduce a form factor $F(s_{12},m_R)$ for the strong coupling involved in the $R(m_{12})\to P_1P_2$ decay when $m_{12}$ is away from $m_R$. We find that off-shell effects are small in vector meson productions, but prominent in the $K_2^*(1430)$, $\sigma/f_0(500)$ and $K_0^*(1430)$ resonances. (iii) We evaluate $\eta_R$ in the theoretical framework of QCD factorization (QCDF) and in the experimental parameterization (EXPP) for three-body decay amplitudes. In general, $\eta_R^{\rm QCDF}$ and $\eta_R^{\rm EXPP}$ are similar for vector mesons, but different for tensor and scalar resonances. A study of the differential rates enables us to understand the origin of their differences. (iv) Finite-width corrections to $Br(B^-\to RP)_{\rm NWA}$ obtained in the narrow width approximation are generally small, less than 10\%, but they are prominent in $B^-\to\sigma/f_0(500)\pi^-$ and $B^-\to \overline K_0^{*0}(1430)\pi^-$ decays. The EXPP of the normalized differential rates should be contrasted with the theoretical predictions from QCDF calculation as the latter properly takes into account the energy dependence in weak decay amplitudes.

Intensity-dependent two-photon absorption and its saturation in 2-methyl 4-nitroaniline nanofibers

The Nonlinear absorption and its optical limiting properties of 2-methyl 4-nitroaniline-polymethylmethacrylate (2M4NA-PMMA) electro-spun nanofibers are investigated by Z-scan technique using Q switched Nd:YAG laser as an excitation source (532 nm, 5 ns, 10 Hz). Open-aperture measurements show that 2M4NA-PMMA nanofibers exhibit reverse saturable absorption. Intensity-dependent two-photon absorption coefficient demonstrates the presence of sequential two-photon absorption process involving real resonant intermediate states. The incorporation and orientation of 2M4NA in PMMA nanofibers are analyzed by XRD and it is found to range from 38 nm to 43 nm of crystallite size. SEM images illustrate the formation of smooth fibers using electrospinning by applying different voltages (12, 14, 17 kV). Ground-state absorption analysis shows that the nanofibers possess maximum absorption around 400 nm with a optical transmittance window (410–1200 nm) in the wide range of entire visible and NIR region. Lower optical limiting threshold (0.97 to 1.79 × 1012 W/m2) of 2M4NA-PMMA nanofibers ensures the suitability of optical fibers as optical limiters towards the development of laser goggles for pulsed green laser.

Two-photon exchange from intermediate state resonances in elastic electron-proton scattering

We use a recently developed dispersive approach to compute the two-photon exchange (TPE) correction to elastic electron-proton scattering, including contributions from hadronic $J^P=1/2^\pm$ and $3/2^\pm$ resonant intermediate states below~1.8~GeV. For the transition amplitudes from the proton ground state to the resonant excited states we employ new exclusive meson electroproduction data from CLAS at $Q^2 \lesssim 5$~GeV$^2$, and we explore the effects of both fixed and dynamic widths for the resonances. Among the resonant states, the $N(1520)~\!3/2^-$ becomes dominant for $Q^2 \gtrsim 2$~GeV$^2$, with a sign opposite to the comparably sized $\Delta(1232)~\!3/2^+$ contribution, leading to an overall increase in the size of the TPE correction to the cross section relative to the nucleon only contribution at higher $Q^2$ values. The results are in good overall agreement with recent $e^+ p$ to $e^- p$ cross section ratio and polarization transfer measurements, and provide compelling evidence for a resolution of the electric to magnetic form factor ratio discrepancy.

Spectroscopy of Resonant Intermediate States for Triplet-Triplet Annihilation Upconversion in Crystalline Rubrene: Radical Ions as Sensitizers.

Photoluminescence upconversion in crystalline rubrene can proceed without an added sensitizer, but the mechanism for this process has not been well-understood. In particular, the species responsible for photon absorption has not been identified to date. To gain insight into the identity of the intermediate state, we measured the near-infrared (NIR) upconversion photoluminescence (UCPL) excitation spectrum of rubrene crystals and found three distinct spectral features. The UCPL yield has a quartic dependence on the laser intensity, implying a four-photon process. On the basis of electronic spectra of radical cations and anions of rubrene, we propose a mechanism in which photoexcited radical anions and cations undergo recombination, forming an excited neutral triplet while conserving spin. The triplets formed this way ultimately undergo triplet-triplet annihilation, resulting in the observed photoluminescence. This mechanism explains the origin of the NIR absorption as well as the four-photon nature of the UCPL process.

An Electron Propagator Approach Based on a Multiconfigurational Reference State for the Investigation of Negative-Ion Resonances Using a Complex Absorbing Potential Method.

Negative-ion resonances are important metastable states that result from the collision between an electron and a neutral target. The course of many chemical processes in nature is often dictated by how an intermediate resonance state falls apart. This article reports on the development of an electron propagator (EP) based on a Hamiltonian Ĥ perturbed by a complex absorbing potential (CAP) and a multiconfigurational self-consistent field (MCSCF) initial state to study these resonances. Perturbation of Ĥ by a CAP makes the resonances amenable to a bound-state method like MCSCF. Resonances stand out among the non-resonant states as persistent complex eigenvalues of the perturbed Ĥ when the strength (η) of the CAP is varied. The MCSCF method gives a reliable and accurate description of the target states, especially when the non-dynamical correlations are dominant. The resonance energies are obtained from the poles of the EP. We propose three variants of our EP depending on how the effect of the CAP is introduced. We find that the computationally most efficient variant is the one in which the reference state of the EP is an unperturbed MCSCF wavefunction and a non-zero CAP is defined only on the virtual orbital subspace of the reference state. The onset of the CAP is carefully optimized in order to minimize the artifacts due to reflections from the CAP. An extrapolation method (based on a Padé approximant) and a de-perturbation method are adopted in order to account for the limitations of finite basis sets used and determine the resonance energy in the limit of η → 0. 2P Be-, 2Πg N2-, and 2Π CO- shape resonances are investigated. The position and width of these resonances computed in this study agree well with those reported earlier in the literature.

Resonant contributions to three-body Brightarrow KKK decays in perturbative QCD approach

In this work, we study the (S, P and D)-wave K^+K^- contributions to Brightarrow KKK decays in the perturbative QCD approach at leading order. Within the two-meson wave functions describing the nonperturbative dynamics in the kaon-pair for different waves, we calculate the branching fractions and the direct CP asymmetries of these decay modes in the corresponding resonance regions. Most of our numerical results are well consistent with the current measurements. We note that the narrow-width approximation is invalid in the quasi-two-body decays Brightarrow Kf_0(980)rightarrow KKK. For other decays, under the narrow-width approximation we can extract the branching fractions of the corresponding two-body decays involving the intermediate resonant states, and the related branching fractions agree with the current experimental data well. Furthermore, we also predict the branching fractions of the corresponding quasi-two-body decays Brightarrow Kpi ^+pi ^-, which are expected to be tested in the ongoing LHCb and Belle-II experiments.

Resonant two-photon spectroscopy of the 2s3d 1D2 level of neutral Be9

We report an absolute frequency measurement of the $2s3d{\phantom{\rule{0.16em}{0ex}}}^{1}{D}_{2}$ state in neutral $^{9}\mathrm{Be}$ using two-photon spectroscopy with a resonant intermediate state. The absolute center-of-gravity energy is determined to be 64 428.40 321(55) ${\mathrm{cm}}^{\ensuremath{-}1}$, a factor of 180 more precise than the previous experimental measurement. We also confirm our previous result for the energy of the intermediate $2s2p{\phantom{\rule{0.16em}{0ex}}}^{1}{P}_{1}$ level. Precision is limited by unresolved hyperfine structure and the complications of performing resonant two-photon spectroscopy on an atomic beam. A three-level rate-equation analysis is presented to explore, and minimize, systematic uncertainties arising from small deviations of the angle between the atomic and optical beams off-perpendicular.

Four α-particle decay of the excited 16O* quasi-projectile in the 16O + 12C reaction at 130 MeV

The four α-particle decay of the excited 16O* quasi-projectile (QP) produced in peripheral 16O + 12C reactions at 130 MeV is studied in detail. The different decay channels leading to the four α-particle final state are reconstructed from an event-by-event analysis of α correlations through the population of intermediate 8Be and 12C resonant states. A small but non-negligible contribution of 8Begs evaporation is observed. The branching ratios of the different evaporation channels are compared to the prediction of an Hauser-Feshbach code (once characteristics of the QP source are extracted from the experimental data), which very accurately reproduces all the inclusive observables of the reaction. However, significative deviations are observed. In particular, the experimental population of the Hoyle state is significantly lower than the predictions of the statistical model, suggesting possible structure effects in the Coulomb barrier and/or in the transmission coefficients.