Analysis of the X(1835) and related baryonium states with Bethe-Salpeter equation

In this article, we study the mass spectrum of the baryon-antibaryon bound states p [`(p)] \bar{{p}} , S \Sigma [`(S)] \bar{{\Sigma}} , X \Xi [`(X)] \bar{{\Xi}} , L \Lambda [`(L)] \bar{{\Lambda}} , p [`(N)] \bar{{N}}(1440) , S \Sigma [`(S)] \bar{{\Sigma}}(1660) , X \Xi [`(X)]<sup>￠</sup> \bar{{\Xi}}^{{\prime}}_{} and L \Lambda [`(L)] \bar{{\Lambda}}(1600) with the Bethe-Salpeter equation. The numerical results indicate that the p [`(p)] \bar{{p}} , S \Sigma [`(S)] \bar{{\Sigma}} , X \Xi [`(X)] \bar{{\Xi}} , p [`(N)] \bar{{N}}(1440) , S \Sigma [`(S)] \bar{{\Sigma}}(1660) , X \Xi [`(X)]^￠ \bar{{\Xi}}^{{\prime}}_{} bound states maybe exist, and the new resonances X(1835) and X(2370) can be tentatively identified as the p [`(p)] \bar{{p}} and p [`(N)] \bar{{N}}(1440) (or N(1400)[`(p)] \bar{{p}} bound states, respectively, with some gluon constituents, and the new resonance X(2120) may be a pseudoscalar glueball. On the other hand, the Regge trajectory favors identifying the X(1835) , X(2120) and X(2370) as the excited h^￠ \eta^{{\prime}}_{}(958) mesons with the radial quantum numbers n = 3 , 4 and 5, respectively.     

Stable multiquark states with heavy quarks in a diquark model

Based on the color–spin interaction in diquarks, we argue why some multiquark configurations could be stable against strong decay when heavy quarks are included. After showing the stability of previously discussed states we identify new possible stable states. These are the T⁰_cb(ud[`(c)][`(b)])T^{0}_{cb}(ud\bar{c}\bar{b}) tetraquark, the \varTheta _bs(udus[`(b)])\varTheta _{bs}(udus\bar{b}) pentaquark and the H _c (udusuc) dibaryon, and so forth.     

Production of the P-wave excited Bc-states through the Z0 boson decays

In Deng et al. (Eur. Phys. J. C 70:113, 2010), we have dealt with the production of the two color-singlet S-wave (c[`(b)])(c\bar{b})-quarkonium states B<sub>c</sub>(|(c[`(b)])₁[¹S₀]?)B_{c}(|(c\bar {b})_{\mathbf{1}}[^{1}S_{0}]\rangle) and B^*_c(|(c[`(b)])<sub>1</sub>[<sup>3</sup>S<sub>1</sub>]?)B^{*}_{c}(|(c\bar{b})_{\mathbf{1}}[^{3}S_{1}]\rangle) through the Z <sup>0</sup> boson decays. As an important sequential work, we make a further discussion on the production of the more complicated P-wave excited (c[`(b)])(c\bar{b})-quarkonium states, i.e. |(c[`(b)])<sub>1</sub>[<sup>1</sup>P<sub>1</sub>]?|(c\bar{b})_{\mathbf{1}}[^{1}P_{1}]\rangle and |(c[`(b)])₁[³P_J]?|(c\bar{b})_{\mathbf{1}}[^{3}P_{J}]\rangle (with J=(1,2,3)). More over, we also calculate the channel with the two color-octet quarkonium states |(c[`(b)])<sub>8</sub>[<sup>1</sup>S<sub>0</sub>]g?|(c\bar{b})_{\mathbf{8}}[^{1}S_{0}]g\rangle and |(c[`(b)])₈[³S₁]g?|(c\bar{b})_{\mathbf{8}}[^{3}S_{1}]g\rangle, whose contributions to the decay width maybe at the same order of magnitude as that of the color-singlet P-wave states according to the naive nonrelativistic quantum chromodynamics scaling rules. The P-wave states shall provide sizable contributions to the B _c production, whose decay width is about 20% of the total decay width \varGamma _{Z⁰? Bc}\varGamma _{Z^{0}\to B_{c}}. After summing up all the mentioned (c[`(b)])(c\bar {b})-quarkonium states’ contributions, we obtain \varGamma _{Z⁰? Bc}=235.9^+352.8_-122.0\varGamma _{Z^{0}\to B_{c}}=235.9^{+352.8}_{-122.0} KeV, where the errors are caused by the main sources of uncertainty.     

Spin correlations of \varLambda[`\varLambda]\varLambda{\bar{\varLambda}} pairs as a probe of quark–antiquark pair production

The polarizations of Λ and [`\varLambda]{\bar{\varLambda}} are thought to retain memories of the spins of their parent s quarks and [`(s)]{\bar{s}} antiquarks, and are readily measurable via the angular distributions of their daughter protons and antiprotons. Correlations between the spins of Λ and [`\varLambda]{\bar{\varLambda}} produced at low relative momenta may therefore be used to probe the spin states of s [`(s)]s {\bar{s}} pairs produced during hadronization. We consider the possibilities that they are produced in a ³P₀ state, as might result from fluctuations in the magnitude of á[`(s)] s ?\langle {\bar{s}} s \rangle, a <sup>1</sup>S<sub>0</sub> state, as might result from chiral fluctuations, or a <sup>3</sup>S<sub>1</sub> or other spin state, as might result from production by a quark–antiquark or gluon pair. We provide templates for the p [`(p)]p {\bar{p}} angular correlations that would be expected in each of these cases, and discuss how they might be used to distinguish s [`(s)]s {\bar{s}} production mechanisms in pp and heavy-ion collisions.     

Cosmological evolution of interacting dark energy in Lorentz violation

The cosmological evolution of an interacting scalar-field model in which the scalar field interacts with dark matter, radiation, and baryons via Lorentz violation is investigated. We propose a model of interaction through the effective coupling, [`(b)]\bar{\beta} . Using dynamical system analysis, we study the linear dynamics of an interacting model and show that the dynamics of critical points are completely controlled by two parameters. Some results can be mentioned as follows. Firstly, the sequence of radiation, the dark matter, and the scalar-field dark energy exist and baryons are subdominant. Secondly, the model also allows for the possibility of having a universe in the phantom phase with constant potential. Thirdly, the effective gravitational constant varies with respect to time through [`(b)]\bar{\beta} . In particular, we consider the simple case where [`(b)]\bar{\beta} has a quadratic form and has a good agreement with the modified ΛCDM and quintessence models. Finally, we also calculate the first post-Newtonian parameters for our model.     

D-mesons and charmonium states in hot isospin asymmetric strange hadronic matter

We study the properties of D and [`(D)] \bar{{D}} mesons in hot isospin asymmetric strange hadronic matter, arising due to their interactions with the hadrons in the hyperonic medium. The interactions of D and [`(D)] \bar{{D}} mesons with these light hadrons are derived by generalizing the chiral SU(3) model used for the study of hyperonic matter to SU(4). The nucleons, hyperons, the scalar isoscalar meson, σ and the scalar-isovector meson, d \delta as modified in the strange hadronic matter, modify the masses of D and [`(D)] \bar{{D}} mesons. It is found that, as compared to the [`(D)] \bar{{D}} mesons ([`(D<sup>0</sup>)] \bar{{D^0}}, D <sup>−</sup>), the properties of the D mesons (D <sup>0</sup>, D <sup>+</sup>) are more sensitive to the isospin asymmetry at high densities. On the other hand, the effects of strangeness fraction are found to be more dominant for the [`(D)] \bar{{D}} mesons as compared to the D mesons and these modifications are observed to be particularly appreciable at high densities. We also study the mass modifications of the charmonium states J/ψ, ψ(3686) and ψ(3770) in the isospin asymmetric strange hadronic matter at finite temperatures and investigate the possibility of the decay of the charmonium states into D [`(D)] \bar{{D}} pairs in the hot hadronic medium. The mass modifications of these charmonium states arise due to their interaction with the gluon condensates of QCD, simulated by a scalar dilaton field introduced to incorporate the broken scale invariance of QCD within the effective chiral model. The effects of finite quark masses are taken into account in the trace of the energy momentum tensor in QCD, while investigating the medium modification of the charmonium masses through the modification of the gluon condensate in the medium. We also compute the partial decay widths of the charmonium states to the D [`(D)] \bar{{D}} pairs in the hadronic medium. The strong dependence on density of the in-medium properties of the D, [`(D)] \bar{{D}} and the charmonium states, as well as the partial decay widths of charmonium states to D [`(D)] \bar{{D}} pairs, found in the present investigation, will be of direct relevance in observables like open charm enhancement as well as J/ψ suppression in the compressed baryonic matter (CBM) experiments at the future Facility for Antiproton and Ion Research, GSI, where the baryonic matter at high densities is planned to be produced.     

Study of $$qqqc\bar c$$ five quark system with three kinds of quark-quark hyperfine interaction

The low-lying energy spectra of five quark systems uudc[`(c)]uudc\bar c (I = 1/2, S = 0) and udsc[`(c)]udsc\bar c (I = 0, S = 1) are investigated with three kinds of schematic interaction: the chromomagnetic interaction, the flavor-spin-dependent interaction and the instanton-induced interaction. In all the three models, the lowest five-quark state (uudc[`(c)]uudc\bar c or udsc[`(c)]udsc\bar c) has an orbital angular momentum L = 0 and the spin-parity J ^P = 1/2⁻; the mass of the lowest udsc[`(c)]udsc\bar c state is heavier than the lowest uudc[`(c)]uudc\bar c state.     

Three-wave diffraction in damaged epitaxial layers with a wurtzite structure

Three-wave diffraction of X-rays is measured using the Renninger scheme for a series of GaN epitaxial layers of various thicknesses and degrees of structural perfection. In each 30°-angular interval of azimuthal rotation, all ten three-wave peaks determined by the geometry of diffraction with the 0001 first forbidden reflection and CuK _α radiation are observed. The φ- and θ-scanned diffraction curves are measured for each three-wave combination. The angular FWHM of the diffraction peaks formed in experiments and its relation with the parameters of the two-wave diffraction pattern and the dislocation structure of the layers are analyzed. It is shown that the φ-scan peaks are less sensitive to the degree of structural perfection than the γ-mode peaks. The strongest dependence on the dislocation density for the latter peaks is observed for the (1[`1]00)/([`1]101)(1\bar 100)/(\bar 1101) and (3[`2][`1]0)/([`3]211)(3\bar 2\bar 10)/(\bar 3211) three-wave combinations with a pure Laue component of secondary radiation, while the (01[`1]3)/(0[`1]1[`2])(01\bar 13)/(0\bar 11\bar 2) combination with a large Bragg component exhibits the weakest dependence. Splitting of three-wave Renninger peaks associated with the coarse-block structure of some of the layers with rotations of the blocks about the normal to the surface is detected. The total integrated intensity of all three-wave combinations is determined and their ratios are in qualitative agreement with the theory.     

Electromagnetic structure of W± bosons in the e–e+ → W+W– reaction

A model-independent analysis of anomalous gauge coupling constants of W ^± bosons is presented and the corresponding restrictions on them and on the electromagnetic characteristics of W ^± bosons following from the experiments on measuring the e⁺ e^- ? W⁺ W^- ? ( e

Light flavor asymmetry of nucleon sea

The light flavor antiquark distributions of the nucleon sea are calculated in the effective chiral quark model and compared with experimental results. The contributions of the flavor-symmetric sea-quark distributions and the nuclear EMC effect are taken into account to obtain the ratio of Drell–Yan cross sections σ ^pD/2σ ^pp, which can match well with the results measured in the FermiLab E866/NuSea experiment. The calculated results also match the [`(d)](x)-[`(u)](x)\bar{d}(x)-\bar{u}(x) measured in different experiments, but unmatch the behavior of [`(d)](x)/[`(u)](x)\bar{d}(x)/\bar{u}(x) derived indirectly from the measurable quantity σ ^pD/2σ ^pp by the FermiLab E866/NuSea Collaboration at large x. We suggest to measure again [`(d)](x)/[`(u)](x)\bar{d}(x)/\bar{u}(x) at large x from precision experiments with careful treatment of the experimental data. We also propose an alternative procedure for experimental data treatment.     

A new approach to diffusion-limited reaction rate theory

A new approach to the diffusion-limited reaction rate theory is developed on the base of a similar approach to consideration of Brownian coagulation, recently proposed by the author. The traditional diffusion approach to calculation of the reaction rate is critically analyzed. In particular, it is shown that the traditional approach is applicable only to the special case of reactions with a large reaction radius, [`(r)]<sub>A</sub> << R<sub>AB</sub> << [`(r)]_B\bar r_A \ll R_{AB} \ll \bar r_B (where [`(r)]<sub>A</sub>\bar r_A, [`(r)]_B\bar r_B are the mean interparticle distances), and becomes inappropriate to calculation of the reaction rate in the case of a relatively small reaction radius, R_AB << [`(r)]<sub>A</sub>R_{AB} \ll \bar r_A, [`(r)]_B\bar r_B. In the latter, most general case particles collisions occurmainly in the kinetic regime (rather than in the diffusion one) characterized by a homogeneous (at random) spatial distribution of particles. Homogenization of particles distribution occurs owing to particles diffusion mixing on the length scale of the mean interparticle distance with the characteristic diffusion time being small in comparison with the characteristic reaction time. The calculated reaction rate for a small reaction radius in 3D formally (and casually) coincides with the expression derived in the traditional approach for reactions with a large reaction radius, however, notably deviates at large times from the traditional result in the plane (2D) geometry.     

Analysis of the <Emphasis Type="Italic">Y</Emphasis>(4140) and related molecular states with QCD sum rules

In this article, we assume that there exist scalar D^*[`(D)]<sup>*</sup>{D}^{\ast}{\bar {D}}^{\ast}, D<sub>s</sub><sup>*</sup>[`(D)]_s^*{D}_{s}^{\ast}{\bar{D}}_{s}^{\ast}, B^*[`(B)]<sup>*</sup>{B}^{\ast}{\bar {B}}^{\ast} and B<sub>s</sub><sup>*</sup>[`(B)]_s^*{B}_{s}^{\ast}{\bar{B}}_{s}^{\ast} molecular states, and study their masses using the QCD sum rules. The numerical results indicate that the masses are about (250–500) MeV above the corresponding D ^*–[`(D)]<sup>*</sup>{\bar{D}}^{\ast}, D <sub>s</sub> <sup>*</sup>–[`(D)]_s^*{\bar {D}}_{s}^{\ast}, B ^*–[`(B)]<sup>*</sup>{\bar{B}}^{\ast} and B <sub>s</sub> <sup>*</sup>–[`(B)]_s^*{\bar {B}}_{s}^{\ast} thresholds, the Y(4140) is unlikely a scalar D_s^*[`(D)]<sub>s</sub><sup>*</sup>{D}_{s}^{\ast}{\bar{D}}_{s}^{\ast} molecular state. The scalar D<sup>*</sup>[`(D)]^*D^{\ast}{\bar{D}}^{\ast}, D_s^*[`(D)]<sub>s</sub><sup>*</sup>D_{s}^{\ast}{\bar{D}}_{s}^{\ast}, B<sup>*</sup>[`(B)]^*B^{\ast}{\bar{B}}^{\ast} and B_s^*[`(B)]<sub>s</sub><sup>*</sup>B_{s}^{\ast}{\bar{B}}_{s}^{\ast} molecular states maybe not exist, while the scalar D￠<sup>*</sup>[`(D)]^￠*{D'}^{\ast}{\bar{D}}^{\prime\ast}, D_s^￠*[`(D)]<sub>s</sub><sup>￠*</sup>{D}_{s}^{\prime\ast}{\bar{D}}_{s}^{\prime\ast}, B<sup>￠*</sup>[`(B)]^￠*{B}^{\prime\ast}{\bar{B}}^{\prime\ast} and B_s^￠*[`(B)]_s^￠*{B}_{s}^{\prime\ast}{\bar{B}}_{s}^{\prime\ast} molecular states maybe exist.     

Radiative QCD backgrounds to exclusive $H\to b\bar{b}$ production: radiation from the screening gluon

Central exclusive Higgs boson production, pp→p ⊕ H ⊕ p, at the LHC can provide an important complementary contribution to the comprehensive study of the Higgs sector in a remarkably clean topology. The \(b\bar{b}\) Higgs decay mode is especially attractive, and for certain BSM scenarios may even become the discovery channel. Obvious requirements for the success of such exclusive measurements are strongly suppressed and controllable backgrounds. One potential source of background comes from additional gluon radiation which leads to a three-jet \(b\bar{b}g\) final state. We perform an explicit calculation of the subprocesses \(gg\to q\bar{q}g\), gg→ggg in the case of ‘internal’ gluon radiation from the spectator, t-channel screening gluon, when the two incoming active t-channel gluons form a color octet. We find that the overall contribution of this source of background is orders of magnitude lower than that caused by the main irreducible background resulting from the \(gg^{\mathrm{PP}}\to b\bar{b}\) subprocess. Therefore, this background contribution can be safely neglected.     

Proton femtoscopy at STAR

The analysis of two-particle femtoscopy provides a powerful tool to study the properties of matter created in heavy ion collisions. Applied to identical and nonidentical hadron pairs, it makes the study of space-time evolution of the source in femtoscopic scale possible. Baryon femtoscopy allows extraction of the radii of produced sources which can be compared to those deduced from identical pion studies, providing additional information about source characteristics. In this paper we present the correlation functions obtained for protons and antiprotons for Au + Au collisions √s _NN = 62.4 and 200 GeV. On the other hand, as STAR experiment participates in Beam Energy Scan program, we present theoretical predictions of p − p, [`(p)] - [`(p)]\bar p - \bar p and p - [`(p)]p - \bar p femtoscopic measurements, based on UrQMD simulation for √s _NN = 5–39 GeV.     

Scaling and self-averaging in the three-dimensional random-field Ising model

We investigate, by means of extensive Monte Carlo simulations, the magnetic critical behavior of the three-dimensional bimodal random-field Ising model at the strong disorder regime. We present results in favor of the two-exponent scaling scenario, [`(h)]\bar{\eta} = 2η, where η and [`(h)]\bar{\eta} are the critical exponents describing the power-law decay of the connected and disconnected correlation functions and we illustrate, using various finite-size measures and properly defined noise to signal ratios, the strong violation of self-averaging of the model in the ordered phase.     

Processes of ordering of structural elements, critical and noncritical parameters of phase transitions in the (NH4)3WO3F3 crystal

The structure of the low-temperature triclinic phase of the (NH₄)₃WO₃F₃ crystal has been determined and the structure of the cubic phase of this crystal has been refined from data of an X-ray diffraction experiment performed for a powder sample. The profile and structural parameters have been refined according to the procedure implemented in the DDM program. The results obtained have been discussed with invoking the group-theoretical analysis of the complete order parameter condensate, which takes into account the critical and noncritical atomic orderings and allows one to interpret the obtained experimental data. It has been found that the symmetry transformation in the crystal can be schematically represented in the following form: Fm[`3]m(Z = 4) ? P[`1](Z = 1) ? P[`1](Z = 6)Fm\bar 3m(Z = 4) \to P\bar 1(Z = 1) \to P\bar 1(Z = 6). This transformation is accompanied by the complete ordering of WO₃F₃ polyhedra and the displacement of NH₄ ions.     

Effects of the anomalous Higgs couplings on the Higgs boson production at the Large Hadron Collider

We study the impact of dimension-six operators on single- and double-Higgs production rates via gluon fusion at the Large Hadron Collider (LHC). If the top-Yukawa coupling is modified by some new physics whose scale is of the TeV scale, its effect changes the cross sections of single-Higgs production gg→H and double-Higgs production gg→HH through the top-loop diagram. In particular, double-Higgs production can receive significant enhancement from the effective top-Yukawa coupling and the new dimension-five coupling t[`(t)]HHt{\bar{t}}HH which are induced by the dimension-six operator. Comparing these results to the forthcoming data at the LHC, one can extract information of the dimension-six operators relevant to the top quark and the Higgs boson.     

Observability of Charged Higgs Contribution in t-channel Single Top at LHC

In this paper, the charged Higgs contribution in t-channel single top production is studied. The production process is a t-channel single top event with charged Higgs exchange. Therefore the signal is similar with Standard Model single top production in terms of the final state. In the first step, the signal cross section is calculated and compared to the other main production processes which are used for a heavy charged Higgs search at LHC, i.e., \(pp\rightarrow t\bar {b}H^{-}\) and \(pp\rightarrow H^{+} \rightarrow t\bar {b}\). In the next step, an event generation and analysis is applied on signal and background events, in order to estimate the signal significance. The signal cross section is typically smaller than the associated production (\(t\bar {b}H^{-}\)) and resonance production (\(t\bar {b}\)) by a factor of 10^?3 and ranges from 10 f b to 1 f b for charged Higgs mass from 200 to 500 GeV at tanβ = 50. Due to the small cross section of signal events and large SM background, the signal significance is small even after a dedicated kinematic analysis and selection of events, however, tanβ values above 120 can be excluded at an integrated luminosity of 3000 f b ^?1.