Narrow States Research Articles

Globin X: A highly stable intrinsically hexacoordinate globin

Several novel members of the vertebrate globin family were recently discovered with unique structural features that are not found in traditional penta-coordinate globins. Here we combine structural tools to better understand and recognize molecular determinants that contribute to the stability of hexacoordinate globin X (GbX) from Danio rerio (zebrafish). pH-induced unfolding data indicates increased stability of GbX with pHmid of 1.9 ± 0.1 for met GbXWT, 2.4 ± 0.1 for met GbXC65A, and 3.4 ± 0.1 for GbXH90V. These results are in good agreement with GbX unfolding experiments using GuHCl, where a ΔGunf 13.8 ± 2.5 kcal mol−1 and 16.3 ± 2.6 kcal mol−1 are observed for metGbXWT, and metGbXC65A constructs, respectively, and diminished stability is measured for GbXH90V, ΔGunf = 9.5 ± 3.6 kcal mol−1. The metGbXWT and metGbXC65A also exhibit high thermal stability (melting points of 118 °C and 107 °C, respectively). Native ion mobility - mass spectrometry (IM-MS) experiments showed a narrow charge state distribution (9–12+) characteristics of a native, structured protein; a single mobility band was observed for the native states. Collision induced unfolding IM-MS experiments showed a two-state transition, in good agreement with the solution studies. GbXWT retains the heme over a wide range of charge states, suggesting strong interactions between the prosthetic group and the apoprotein. The above results indicate that in addition to the disulfide bond and the heme iron hexa-coordination, other structural determinants enhance stability of this protein.

Study of the Electronic Defect States of One-Dimensional Comb-like Quantum Wires Structure with Resonator Defect by Using the Transfer Matrix Method

In this paper using the transfer matrix method (TMM), we consider an electronic comb-like waveguides system composed by the periodicity of segment semiconductor (GaAs type) of length and grafted in its extremity by one semiconductor resonator (GaAlAs type) of length . These segments and resonators are considered quantum wires. The perfect system in question presents the electronic pass bands and electronic band gaps which allow to control and manipulate the electrons waves whose energy is identical to the energy of the gaps. We insert the defect at the resonator level in the middle of this system in question. Hence, very narrow localized defect states are created in the electronic band gaps, with probably high transmission rate and very important quality factor. These localized defect states shift to low energy by increasing the resonator defect length, while is move to high energy when the resonator defect concentration increases. In this study, we consider that the segments and resonators lengths are very small in front of their sections, so that the propagation of electronic waves occurs only in a single dimension.

Study of the doubly charmed tetraquark {{{{{{rm{T}}}}}}}_{{{{{{rm{c}}}}}}{{{{{rm{c}}}}}}}^{+}

Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the D0D0π+ mass spectrum just below the D*+D0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar {{{{{{rm{T}}}}}}}_{{{{{{rm{c}}}}}}{{{{{rm{c}}}}}}}^{+} tetraquark with a quark content of {{{{{rm{c}}}}}}{{{{{rm{c}}}}}}overline{{{{{{rm{u}}}}}}}overline{{{{{{rm{d}}}}}}} and spin-parity quantum numbers JP = 1+. Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D*+ mesons is consistent with the observed D0π+ mass distribution. To analyse the mass of the resonance and its coupling to the D*D system, a dedicated model is developed under the assumption of an isoscalar axial-vector {{{{{{rm{T}}}}}}}_{{{{{{rm{c}}}}}}{{{{{rm{c}}}}}}}^{+} state decaying to the D*D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the {{{{{{rm{T}}}}}}}_{{{{{{rm{c}}}}}}{{{{{rm{c}}}}}}}^{+} state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.

Observation of Two New Excited Ξ_{b}^{0} States Decaying to Λ_{b}^{0}K^{-}π^{+}.

Two narrow resonant states are observed in the Λ_{b}^{0}K^{-}π^{+} mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb^{-1}. The minimal quark content of the Λ_{b}^{0}K^{-}π^{+} system indicates that these are excited Ξ_{b}^{0} baryons. The masses of the Ξ_{b}(6327)^{0} and Ξ_{b}(6333)^{0} states are m[Ξ_{b}(6327)^{0}]=6327.28_{-0.21}^{+0.23}±0.12±0.24 and m[Ξ_{b}(6333)^{0}]=6332.69_{-0.18}^{+0.17}±0.03±0.22 MeV, respectively, with a mass splitting of Δm=5.41_{-0.27}^{+0.26}±0.12 MeV, where the uncertainties are statistical, systematic, and due to the Λ_{b}^{0} mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Γ[Ξ_{b}(6327)^{0}]<2.20(2.56) and Γ[Ξ_{b}(6333)^{0}]<1.60(1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths, and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Ξ_{b}^{0} resonances.

Doubly-heavy tetraquark states and * *Partly supported by the National Natural Science Foundation of China (11847145, 11865019)

Inspired by the recent observation of a very narrow state, called , by the LHCb collaboration, the possible bound states and low-lying resonance states of the doubly-heavy tetraquark states ( ) and ( ) are searched in the framework of a chiral quark model with an accurate few-body method, the Gaussian expansion method. The real scaling method is also applied to identify the genuine resonance states. In the calculation, the meson–meson structure, diquark–antidiquark structure, and their coupling are all considered. The numerical results show: (i) For and , only states are bound in different quark structures. The binding energy varies from a few MeV for the meson–meson structure to over 100 MeV for the diquark–antidiquark structure. For example, for , in the meson–meson structure, there exists a weakly bound molecule state around 3841.4 MeV, 1.8 MeV below the , which may be a good candidate for the observed state by LHCb; however in the diquark–antidiquark structure, a deeper bound state with mass 3700.9 MeV is obtained. When considering the structure mixing, the energy of system decreases to 3660.7 MeV and the shallow bound state disappears. (ii) Besides bound states, several resonance states for with are proposed.

Electrical Regulation of CO2 Adsorption in the Metal-Organic Framework MIL-53.

Active regulation of pore accessibility in microporous materials by external stimuli has aroused great attention in recent years. Here, we show the first experimental proof that guest adsorption in a dielectric microporous material can be regulated by a moderate external E-field below the gas breakdown voltage. CO2 adsorption capacity in MIL-53 (Al) was significantly reduced, whereas that of NH2-MIL-53 (Al) changed insignificantly under a direct current E-field gradient of 286 V/mm. Ab initio DFT calculations revealed that the E-field decreased the charge transfer between the CO2 molecule and the adsorption site in the MIL-53 framework, which resulted in reduced binding energy and consequently lowered CO2 adsorption capacity. This effect was only observed in the narrow pore state MIL-53 (Al) but not in its large pore configuration. Our results demonstrate the feasibility of regulating the adsorption of gas molecules in microporous materials using moderate E-fields.

Hydrogen effect on structural and optical properties of in-situ fabricated nc-Si:H prepared by facing targets sputtering

We report high-quality hydrogenated nanocrystalline silicon (nc-Si:H) thin films were prepared by facing targets sputtering (FTS) in the environment of Ar and H2 mixture gases. By increasing hydrogen dilution (RH) of FTS deposition, the structural evolution of as-fabricated Si-based films was observed. Fourier infrared spectroscopy (FTIR) shows that decrease in bonded hydrogen (CH) concentration, especially that of (Si-H2)n with increasing RH, indicating that the H etching effect increased atomic density of these films, thus improving film quality. With the RH increased, the Raman spectra show that the morphological transition from amorphous to crystalline states. We further reveal correlations between the degree of structural order in the amorphous network and the RH by calculating experimental data from the Raman measurements. Moreover, as-fabricated nc-Si:H films show large bandgap and narrow band tail states with increasing RH, which allows potential applications in the window passivation layer for HIT solar cells and Si-based charge-coupled devices (CCD). This work offers a novel route to fabricate high-quality nc-Si:H films for optoelectronic applications.

Understanding the Role of Order in Y‐Series Non‐Fullerene Solar Cells to Realize High Open‐Circuit Voltages

AbstractNon‐fullerene acceptors (NFAs) as used in state‐of‐the‐art organic solar cells feature highly crystalline layers that go along with low energetic disorder. Here, the crucial role of energetic disorder in blends of the donor polymer PM6 with two Y‐series NFAs, Y6, and N4 is studied. By performing temperature‐dependent charge transport and recombination studies, a consistent picture of the shape of the density of state distributions for free charges in the two blends is developed, allowing an analytical description of the dependence of the open‐circuit voltage VOC on temperature and illumination intensity. Disorder is found to influence the value of the VOC at room temperature, but also its progression with temperature. Here, the PM6:Y6 blend benefits substantially from its narrower state distributions. The analysis also shows that the energy of the equilibrated free charge population is well below the energy of the NFA singlet excitons for both blends and possibly below the energy of the populated charge transfer manifold, indicating a down‐hill driving force for free charge formation. It is concluded that energetic disorder of charge‐separated states has to be considered in the analysis of the photovoltaic properties, even for the more ordered PM6:Y6 blend.

Multiply Charged Cation Attachment to Facilitate Mass Measurement in Negative-Mode Native Mass Spectrometry.

Native mass spectrometry (MS) is usually conducted in the positive-ion mode; however, in some cases, it is advantageous to use the negative-ion polarity. Challenges associated with native MS using ensemble measurements (i.e., the measurement of many ions at a time as opposed to the measurement of the charge and the mass-to-charge ratio of individual ions) include narrow charge state distributions with the potential for an overlap in neighboring charge states. These issues can either compromise or preclude confident charge state (and hence mass) determination. Charge state determination in challenging instances can be enabled via the attachment of multiply charged ions of opposite polarity. Multiply charged ion attachment facilitates the resolution of charge states and generates mass-to-charge (m/z) information across a broad m/z range. In this work, we demonstrated the attachment of multiply charged cations to anionic complexes generated under native MS conditions. To illustrate the flexibility available in selecting the mass and charge of the reagents, the 15+ and 20+ charge states of horse skeletal muscle apomyoglobin and the 20+ and 30+ charge states of bovine carbonic anhydrase were demonstrated to attach to model complex anions derived from either β-galactosidase or GroEL. The exclusive attachment of reagent ions is observed with no evidence for proton transfer, which is the key for the unambiguous interpretation of the post-ion/ion reaction product ion spectrum. To illustrate the application to mixtures of complex ions, the 10+ charge state of bovine ubiquitin was attached to mixtures of anions generated from the 30S and 50S particles of the Escherichia coli ribosome. Six and five major components were revealed, respectively. In the case of the 50S anion population, it was shown that the attachment of two 30+ cations of carbonic anhydrase revealed the same information as the attachment of six 10+ cations of ubiquitin. In neither case was the intact 50S particle observed. Rather, particles with different combinations of missing components were observed. This work demonstrated the utility of multiply charged cation attachment to facilitate charge state assignments in native MS ensemble measurements of heterogeneous mixtures.

Tracking Conical Intersections with Nonlinear X-ray Raman Spectroscopy

Conical intersections are formed when 2 or more electronic states become degenerate and give rise to ultrafast nonadiabatic processes such as radiation-less decay channels and geometric phase effects. The branching of nuclear wave packets near a conical intersection creates a coherent superposition of electronic states, which carries information about the energy difference of the involved states. X-ray Raman techniques have been proposed to observe the coherent superposition of the electronic states and to monitor the evolving electronic state separation. However, these techniques rely on the coherence generated as the wave packet passes through the conical intersection, and the electronic energy gap before the wave packet passes through the conical intersection is not tracked. In this paper, we theoretically demonstrate how a nonlinear Raman detection scheme can be used to gain further insight into the nonadiabatic dynamics in the vicinity of the conical intersection. We employ a combination of a resonant visible/infrared pulse and an off-resonant x-ray Raman probe to map the electronic state separation around the conical intersection. We demonstrate that this technique can achieve high contrast and is able to selectively probe the narrow electronic state separation around the conical intersection.

Electromagnetic Form Factors of Λ Hyperon in the Vector Meson Dominance Model and a Possible Explanation of the Near-Threshold Enhancement of the Reaction

The near-threshold reaction is studied with the assumption that the production mechanism is due to a near--threshold bound state. The cross section of the reaction is parameterized in terms of the electromagnetic form factors of λ hyperon, which are obtained with the vector meson dominance model. It is shown that the contribution to the reaction from a new narrow state with quantum numbers JPC = 1− is dominant for energies very close to threshold. The mass of this new state is around 2231 MeV, which is very close to the mass threshold of , while its width is just a few MeV. This gives a possible solution to the problem that all previous calculations seriously underestimated the near-threshold total cross section of the reaction. We also note that the near-threshold enhancement can also be reproduced by including these well established vector resonances ω(1420), ω(1650), ϕ(1680), or ϕ(2170) with a Flatté form for their total decay width, and a strong coupling to the channel.

Toward discovering low-lying P-wave excited Σ c baryon states * *Supported by the National Natural Science Foundation of China (U1832173, 11775078) and Scientific and Technological Innovation Programs of Higher Education Institutions of Shanxi Province, China (2020L0617)

In this study, by combining the equal spacing rule with recent observations of and baryons, we predict the spectrum of the low-lying -mode -wave excited states. Furthermore, their strong decay properties are predicted using the chiral quark model and the nature of is investigated by analyzing the invariant mass spectrum. The structure observed in the mass spectrum was found to potentially arise from two overlapping -wave resonances, and . These resonances have similar decay widths of MeV and predominantly decay into the channel. The state is likely to be a very narrow state with a width of MeV, with its decays almost saturated by the channel. Additionally, evidence of the resonance as a very narrow peak may be seen in the invariant mass spectrum. The other two -wave states, and , are relatively narrow states with similar widths of MeV and predominantly decay into and , respectively. This study can provide useful references for discovering these low-lying -wave states in forthcoming experiments.

Doubly heavy tetraquark resonant states

Spectrum of the doubly heavy tetraquarks, bbq¯q¯, is studied in a constituent quark model. Four-body problem is solved in a variational method where the real scaling technique is used to identify resonant states above the fall-apart decay thresholds. In addition to the two bound states that were reported in the previous study we have found several narrow resonant states above the BB⁎ and B⁎B⁎ thresholds. Their structures are studied and are interpreted by the quark dynamics. A narrow resonance with spin-parity JP=1+ is found to be a mixed state of a compact tetraquark and a B⁎B⁎ scattering state. This is driven by a strong color Coulombic attraction between the bb quarks. Negative-parity excited resonances with JP=0−, 1− and 2− form a triplet under the heavy-quark spin symmetry. It turns out that they share a similar structure to the λ-mode of a singly heavy baryon as a result of the strongly attractive correlation for the doubly heavy diquark.

Holographic bottomonium formation in a cooling strong-interaction medium at finite baryon density

The shrinking of the bottomonium spectral function towards narrow quasi-particle states in a cooling strong-interaction medium at finite baryon density is followed within a holographic bottom-up model. The 5-dimensional Einstein-dilaton-Maxwell background is adjusted to lattice-QCD results of sound velocity and susceptibilities. The zero-temperature bottomonium spectral function is adjusted to experimental $\Upsilon$ ground-state mass and first radial excitations. At baryo-chemical potential $\mu_B = 0$, these two pillars let emerge the narrow quasi-particle state of the $\Upsilon$ ground state at a temperature of about 150 MeV. Excited states are consecutively formed at lower temperatures by about 10 (20) MeV for the $2S$ ($3S$) vector states. The baryon density, i.e. $\mu_B > 0$, pulls that formation pattern to lower temperatures. At $\mu_B =$ 200 MeV, we find a shift by about 15 MeV.

Hunting for states in the recent LHCb di- J/ψ invariant mass spectrum

Partial wave analysis is performed, with effective potentials as dynamical inputs, to scrutinize the recent LHCb data on the di-$J/\psi$ invariant mass spectrum. Coupled-channel effects are incorporated in the production amplitude via final state interactions. The LHCb data can be well described. A dynamical generated pole structure, which can be identified as the $X(6900)$ state, is found. Our analysis also provides hints for the existence of three other possible states: a bound state $X(6200)$, a broad resonant state $X(6680)$ and a narrow resonant state $X(7200)$. The $J^{PC}$ quantum numbers of the $X(6680)$ and $X(6900)$ states should be $2^{++}$, while the $X(6200)$ and $X(7200)$ states prefer $0^{++}$. To determine the above states more precisely, more experimental data for the channels, such as $J/\psi\psi(2S)$, $J/\psi\psi(3770)$, di-$\psi(2S)$, are required.

Revisiting the nature of the Pc pentaquarks

The nature of the three narrow hidden-charm pentaquark Pc states, i.e., Pc(4312), Pc(4440) and Pc(4457), is under intense discussion since their discovery from the updated analysis of the process {Lambda}_b^0to J/psi {pK}^{-} by LHCb. In this work we extend our previous coupled-channel approach [Phys. Rev. Lett. 124, 072001 (2020)], in which the Pc states are treated as {Sigma}_c^{left(ast right)}{overline{D}}^{left(ast right)} molecules, by including the {Lambda}_c{overline{D}}^{left(ast right)} and ηcp as explicit inelastic channels in addition to the J/ψp, as required by unitarity and heavy quark spin symmetry (HQSS), respectively. Since inelastic parameters are very badly constrained by the current data, three calculation schemes are considered: (a) scheme I with pure contact interactions between the elastic, i.e., {Sigma}_c^{left(ast right)}{overline{D}}^{left(ast right)} , and inelastic channels and without the {Lambda}_c{overline{D}}^{left(ast right)} interactions, (b) scheme II, where the one-pion exchange (OPE) is added to scheme I, and (c) scheme III, where the {Lambda}_c{overline{D}}^{left(ast right)} interactions are included in addition. It is shown that to obtain cutoff independent results, OPE in the multichannel system is to be supplemented with S-wave-to-D-wave mixing contact terms. As a result, in line with our previous analysis, we demonstrate that the experimental data for the J/ψp invariant mass distribution are consistent with the interpretation of the Pc(4312) and Pc(4440)/Pc(4457) as {Lambda}_coverline{D} and {Sigma}_c{overline{D}}^{ast } hadronic molecules, respectively, and that the data show clear evidence for a new narrow state, Pc(4380), identified as a {Sigma}_c^{ast}overline{D} molecule, which should exist as a consequence of HQSS. While two statistically equally good solutions are found in scheme I, only one of these solutions with the quantum numbers of the Pc(4440) and Pc(4457) being JP = 3/2− and 1/2−, respectively, survives the requirement of regulator independence once the OPE is included. Moreover, we predict the line shapes in the elastic and inelastic channels and demonstrate that those related to the Pc(4440) and the Pc(4457) in the {Sigma}_c^{left(ast right)}overline{D} and ηcp mass distributions from {Lambda}_b^0to {Sigma}_c^{left(ast right)}overline{D}{K}^{-} and {Lambda}_b^0to {eta}_c{pK}^{-} will shed light on the quantum numbers of those states, once the data are available. We also investigate possible pentaquark signals in the {Lambda}_c{overline{D}}^{left(ast right)} final states.

Monochromatization of e⁺e⁻ Colliders with a Large Crossing Angle

The relative center-of-mass energy spread at $e^+e^-$ colliders is about $10^{-3}$, which is much larger than the widths of narrow resonances produced in the s-channel in $e^+e^-$ collisions. This circumstance greatly lowers the resonance production rates of J/Psi, Upsilon(1S), Upsilon(2S), Upsilon(3S) and makes it extremely difficult to observe resonance production of the Higgs boson. Thus, a significant reduction of the center-of-mass energy spread would open up great opportunities in the search for new physics in rare decays of narrow resonances, the search for new narrow states with small $\Gamma_{e^+e^-}$, the study of true muonium and tauonium, etc. The existing monochromatization scheme is only suitable for head-on collisions, while $e^+e^-$ colliders with crossing angles (the so-called Crab Waist collision scheme) can provide significantly higher luminosity due to reduced collision effects. In this paper, we propose a new monochromatization method for colliders with a large crossing angle. The contribution of the beam energy spread to the spread of the center-of-mass energy is canceled by introducing an appropriate energy-angle correlation at the interaction point; $\sigma_W/W \sim (3-5)10^{-6}$ appears possible. Limitations of the proposed method are also considered.

Does the party in power affect FDI? First causal evidence from narrow margin US state elections

Does the party of government influence the amount and type of inward foreign investment? Correlational studies provide inconsistent evidence. Moreover no existing study, for any level of government or any jurisdiction, uses methods that allow for causal inference. We apply regression discontinuity methods to a set of narrow margin US gubernatorial elections. Over the course of a 4-year term the election of a Republican governor causes a 17% boost in the growth of manufacturing-oriented FDI stock, compared to a Democrat. However, the same approach provides no evidence that partisanship matters for the overall level of FDI.

Implications of the [formula omitted] and [formula omitted] as two different states

Recently, the hidden charm tetraquark states Zcs(3985) and Zcs(4000) with strangeness were observed by the BESIII and LHCb collaborations, respectively, which are great breakthroughs for exploring exotic quantum chromodynamics (QCD) structures. The first and foremost question is whether they are the same state. In this work, we explore the implications of the narrower state Zcs(3985) in BESIII and the wider one Zcs(4000) in LHCb as two different states. Within a solvable nonrelativistic effective field theory, we include the possible violations of heavy quark spin symmetry and SU(3) flavor symmetry in a comprehensive approach. If Zcs(3985) and Zcs(4000) are two different states, our results show that Zcs(4000)/Zcs(3985) is the pure (|D‾s∗D〉+/-|D‾sD∗〉)/2 state, and the SU(3) flavor partner of Zc(3900) is Zcs(4000) rather than the Zcs(3985). Another two important consequences are the existence of a tensor D‾s∗D∗ resonance with mass about 4126 MeV and width 13 MeV, and the suppression of the decay mode Zcs(3985)→J/ψK. The two consequences can be tested in experiments and distinguish the two-state interpretation from the one-state scheme.

Sensing mechanism of photonic crystal nanobeam side coupling cascaded aperture chirped nanobeam cavities structure

A photonic crystal nanobeam (PCN) side coupling cascaded aperture chirped photonic crystal nanobeam cavities (PCNCs) structure is proposed to obtain dual-Fano resonances to solve the problem of differential sensitivity. The wider continuous state provided by the photonic crystal nanobeam interferes with the two narrow discrete states generated by the cascaded aperture chirped photonic crystal nanobeam cavities structure to form dual-Fano resonances. Based on the coupled mode theory, the formation mechanism of the dual-Fano resonances is analyzed. The structure is numerically simulated by the finite-difference time-domain method, and the structural parameters are adjusted to optimize the Fano line shape. And the physical mechanism of the differential sensing of the structure and the sensing characteristics are analyzed. The structure can detect the change of the refractive index of the analyte and eliminate the error caused by the interference caused by the change of ambient temperature, which demonstrates the effectiveness of the dual-Fano resonant sensing structure in solving the cross-sensitive problem.