New hadronic states observed at BES II

The report includes the new observation of X(1835) in J/ψ→γη ^′ π ⁺ π ^-, the ωφ threshold enhancement in J/ψ→γωφ, the ωω structure in J/ψ→γωω and the broad 1^- structure at the low K ⁺ K ^- invariant-mass spectrum in J/ψ→K ⁺ K ^- π ⁰.     

Productions of X(1835) as baryonium with sizable gluon content

X(1835) has been treated as a baryonium with sizable gluon content, and to be almost flavor singlet. This picture allows us to rationally understand X(1835) production in J/ψ radiative decays, and its large couplings with pˉ, η^′ππ. The processes ϒ(1S) → γX(1835) and J/ψ → ωX(1835) have been examined. It has been found that Br(ϒ(1S) → γX(1835))Br(X(1835) → pˉ) < 6.45×10^-7, which is compatible with CLEO's recent experimental result (Phys. Rev. D 73, 032001 (2006) hep-ex/0510015). The branching fractions Br(J/ψ → ωX(1835)), Br(J/ψ → ρX(1835)) with X(1835) → pˉ and X(1835) → η^′π⁺π^- have been estimated by the quark-pair creation model. We show that they are heavily suppressed, so the signal of X(1835) is very difficult, if not impossible, to be observed in these processes. The experimental checks for these estimations are expected. The existence of the baryonium nonet is conjectured, and a model-independent derivation of their production branching fractions is presented.     

Recent Beijing Spectroscopy (BES) results

Recent experimental results from Beijing Spectroscopy (BES) are reviewed, including the hadron spectroscopy from J/ψ decays, and a number of new states are found or confirmed, including σ, κ, X(1835), ωφ threshold enhancement in J/ψ→γωφ, a broad resonance in J/ψ→K ⁺ K ⁻ π ⁰, decay studies of ψ(2S) and χ _CJ , as well as the results of ψ(3770) non-D decays. The current status of BEPCII/BESIII, the major upgrade of BEPC/BESII, is also reported. Supported by the National Natural Science Foundation of China (Grant No. 10491300)     

Study of B c → J / ψ π , η c π decays with?perturbative?QCD?approach

The B _c →J/ψ π, η _c π decays are studied with the perturbative QCD approach. It is found that the form factors and for the B _c →J/ψ, η _c transitions and the branching ratios are sensitive to the parameters ω, v, f _J/ψ and , where ω and v are the parameters of the charmonium wave functions for a Coulomb potential and the harmonic-oscillator potential, respectively, and f _J/ψ and are the decay constants of the J/ψ and η _c mesons, respectively. The large branching ratios and the clear signals of the final states make the B _c →J/ψ π, η _c π decays the prospective channels for measurements at the hadron colliders.     

Probing unparticle theory via lepton-flavor violating process <Emphasis Type="Italic">J</Emphasis>/<Emphasis Type="Italic">ψ</Emphasis>→<Emphasis Type="Italic">ll</Emphasis>′ at BESIII

The lepton-flavor violating process J/ψ→ll′(l≠l′) serves as an ideal place to probe the unparticle theory. Such a process can only occur at loop level in the Standard model (SM), so that should be very suppressed; by contrast, in the unparticle scenario, it happens at tree level and its contribution may be sizable for practical measurement. Moreover, the BESIII will offer the largest database on J/ψ, which makes more accurate measurements possible. Furthermore, for such purely leptonic decays the background is relatively low and the signal would be cleaner. Our work carefully investigates the possibility of observing such processes from both theoretical and experimental aspects.     

Radiative decays,photoproduction and total cross section of theψ particles

It is pointed out that the coupling characterizing theψ-γ vertex must change substantially between the limits,ψ on mass-shell which occurs inψ→e ⁺ e ⁻ and photon on mass-shell which is relevant in radiative decays likeψ→ππγ, ψ→ηγ and photoproduction ofψ. This has the consequence that the value ofψN total cross section must be larger than what is inferred from the use of naive vector dominance in photoproduction.     

Ratio of the color suppressed decays Λ b →ΛJ/ψ andB 0→KJ/ψ

Based on the factorization approximation, we have estimated the ratio of the branching fractions for the color suppressed nonleptonic decays Λ _b →ΛJ/ψ andB ⁰→KJ/ψ. Treating thes-quark as heavy, we have used the HQET to calculate the hadronic matrix elements. The mesonic Isgur-Wise function is calculated in the quark model whereas for the baryonic IW function we have employed the bound state soliton picture. The results obtained agree very well with the recent CDF experimental data.     

Chiral symmetry and charmonium decays to two pseudoscalars

We apply hard pion Chiral Perturbation Theory to charmonium decays to ππ, KK and ηη. We first discuss why we expect to be able to provide results for the chiral logarithms in χc0 and χc2 decays to two pseudoscalars while for the decays from J/ψ, ψ(nS) and χc1 no simple prediction is possible. The leading chiral logarithm turns out to be absent for χc0, χc2 → PP. This result is true for all fully chiral singlet states of spin zero and two.     

Polarized angular distributions in the decays of the ψ’ charmonium state directly produced in unpolarized proton–antiproton collisions

Using the helicity formulism, we calculate the combined angular distribution function of the polarized gamma photons and electron in the cascade process pp̄→ψ’→χ_J+γ₁→ψ+γ₂+γ₁→e⁺+e^-+γ₂+γ₁ (J=0,1,2), when p̄ and p are unpolarized. We also present the partially integrated angular distribution functions in different cases. Our results show that by measuring the two-particle angular distribution of γ₁ and γ₂ and that of γ₂ and e^- with the polarization of either one of the two particles, one can determine the relative magnitudes as well as the relative phases of the helicity amplitudes in the radiative decay processes ψ’→χ_J+γ₁ and χ_J→ψ+γ₂. PACS  11.80.Cr; 13.20.Fc; 13.60.Le; 14.40.Gx     

On the determination of double diffraction dissociation cross section at HERA

The excitation of the proton into undetected multiparticle states (double diffraction dissociation) is an important background to single diffractive deep-inelastic processesep→e′p′ρ ⁰,e′p′J/ψ,e′p′X at HERA. We present estimates of the admixture of the double diffraction dissociation events in all diffractive events. We find that in theJ/ψ photoproduction, electroproduction of theρ ⁰ at largeQ ² and diffraction dissociation of real and virtual photons into high mass statesX the contamination of the double diffraction dissociation can be as large as ∼30%, thus affecting substantially the experimental tests of the pomeron exchange in deep inelastic scattering at HERA. We discuss a possibility of tagging the double diffraction dissociation by neutrons observed in the forward neutron calorimeter. We present evaluations of the spectra of neutrons and efficiency of neutron tagging based on the experimental data for diffractive processes in the protonproton collisions.     

Quark-antiquark states and their radiative transitions in terms of the spectral integral equation: Charmonia

Earlier by the authors (Yad. Fiz. 70, 68 (2007)), the bƃ states were treated in the framework of the spectral integral equation, together with simultaneous calculations of radiative decays of the considered bottomonia. In the present paper, such a study is carried out for the charmonium states. We reconstruct the interaction in the c-c sector on the basis of the data for the charmonium levels with J _PC = 0⁻⁺, 1⁻⁻, 0⁺⁺, 1⁺⁺, 2⁺⁺, 1⁺⁻ and radiative transitions ψ(2S) → γχ _c0(1P), γχ _c1(1P), γχ _c2(1P), γχ _c(1S) and χ _c0(1P), χ _c1(1P), χ _c2(1P) → γJ/ψ. The c-c levels and their wave functions are calculated for the radial excitations with n ≤ 6. Also, we determine the c-c component of the photon wave function using the e ⁺ e ⁻-annihilation data: e ⁺ e ⁻ → J/ψ(3097), ψ(3686), ψ(3770), ψ(4040), ψ(4160), ψ(4415) and perform the calculations of the partial widths of the two-photon decays for the n = 1 states η _c0(1S), χ _c0(1P), χ _c2(1P) → γγ and n = 2 states η _c0(2S) → γγ, χ _c0(2P) → γγ. We discuss the status of the recently observed c-c states X(3872) and Y(3941): according to our results, the X(3872) can be either χ _c1(2P) or η _c2(1D), while Y(3941) is χ _c2(2P). The text was submitted by the authors in English.     

Broadening and shifting of vibrational-rotational lines corresponding to the highly excited rotational states of the water molecule

Self-pressure-induced, as well as argon- and nitrogen-induced, broadening γ and shifting δ coefficients of vibrational-rotational lines of the water molecule have been calculated. The asymptotic behavior of the coefficients γ and δ at J → 42 and K _a → J has been studied. For the calculation of the parameters γ and δ, we used the wave functions obtained from the analysis of highly excited rotational states of the H₂O molecule with the maximal ever observed values of rotational quantum numbers J _max = 42, K _amax = 32. Rotational states were analyzed in the method of effective Hamiltonians using generating functions for the first eight vibrational states of the molecule.     

ψ(3770) and B meson exclusive decay B → ψ(3770)K in QCD factorization

Belle has observed surprisingly copious production of ψ(3770) in the B meson decay B → ψ(3770)K, whose rate is comparable to that of B → ψ(3686)K. We study this puzzling process in the QCD factorization approach with the effect of the S-D mixing considered. We find that the soft scattering effects in the spectator interactions play an essential role. With a proper parametrization for the higher-twist soft end-point singularities associated with kaon, and with the S-D mixing angle θ = - 12^°, the calculated decay rates can be close to the data. Implications of these soft spectator effects to other charmonium production in B exclusive decays are also emphasized.     

<Emphasis Type="Italic">J</Emphasis>/<Emphasis Type="Italic">ψ</Emphasis> suppression and <Emphasis Type="Italic">p</Emphasis><Subscript><Emphasis Type="Italic">T</Emphasis></Subscript> spectra in RHIC and LHC energy collisions

In a hydrodynamic model, we have studied J/ψ production in Au+Au/Cu+Cu collisions at RHIC energy, GeV. At the initial time, J/ψ’s are randomly distributed in the fluid. As the fluid evolves in time, the free streaming J/ψ’s are dissolved if the local fluid temperature exceeds a threshold temperature T _J/ψ . Sequential melting of charmonium states (χ _c , ψ ^′ and J/ψ), with melting temperatures , T _J/ψ ≈2T _c and feed-down fraction F≈0.3, explains the PHENIX data on the centrality dependence of J/ψ suppression in Au+Au collisions. J/ψ p _T spectra and the nuclear modification factor in Au+Au collisions are also well explained in the model. The model however overpredicts the centrality dependence of J/ψ suppression in Cu+Cu collisions by 20–30%. The J/ψ p _T spectra are underpredicted by 20–30%. The model predicts that in central Pb+Pb collisions at LHC energy,  GeV, J/ψ’s are suppressed by a factor of ∼10. The model predicted a J/ψ p _T distribution in Pb+Pb collisions at LHC is similar to that in Au+Au collisions at RHIC.     

ψ′ to J/ψ ratio measurements in PHENIX at RHIC

The ratio of the ψ′ over the J ψ production cross section in the dielectron channel has been measured in $ \sqrt s $ \sqrt s = 200 GeV p + p collisions with the PHENIX detector at RHIC. The analysis is based on fitting of the dielectron invariant mass spectra in the area around the J ψ and ψ′ signals in order to extract a ratio ψ′ over J ψ of 0.019 ± 0.005 (stat) ± 0.002 (sys) and a fractional feed-down contribution to J ψ from ψ′ of 8.6 ± 2.5%.     

Interactions of charmed mesons with nucleons in the ¯<Emphasis Type="Italic">p</Emphasis><Emphasis Type="Italic">d</Emphasis> reaction

We study the possibility to measure the elastic ΦN (Φ≡J/ψ,ψ(2S), ψ(3770), χ_2c) scattering cross section in the reaction ˉp+d→Φ+n _sp and the elastic D(ˉD)N scattering cross section in the reaction ˉp+d→D ⁻ D ⁰ p _sp. Our studies indicate that the elastic scattering cross sections can be determined for Φ momenta about 4–6 GeV/c and D/ˉD momenta 2–5 GeV/c by selecting events with p _t≥ 0.4 GeV/c for Φ's and p _t(p _sp) ≥ 0.5 GeV/c for D/ˉD-meson production. Received: 8 November 1999     

η(1475) and <Emphasis Type="Italic">f</Emphasis><Subscript>1</Subscript>(1420) resonances in the decay processes <Emphasis Type="Italic">J</Emphasis>/ψ → γ(ρρ, γρ<Superscript>0</Superscript>, γϕ) and in γγ* collisions

A scenario that removes the contradiction between the suppression of the η(1475) → γγ decay width and the strong coupling of η(1475) to the ρρ, ωω, and γρ⁰ channels and which leads to a nontrivial prediction for the manifestation of η(1475) in γγ*(Q ²) collisions is considered. Data on the dependence of the cross section for the reaction γγ*(Q ²) → K[`(K)]pK\bar K\pi on the photon virtuality in the energy range 1.35–1.55 GeV are explained here by the production of an η(1475) resonance in contrast to their standard interpretation in terms of the f <sub>1</sub>(1420) resonance. Experimental verification of the present explanation requires determining the spin-parity of resonance contributions, R, in the reactions γγ*(Q <sup>2</sup>) R → R → K[`(K)]pK\bar K\pi and J/ψ → γR → γ(γρ⁰, γϕ).     

Rotational excitation of H2 and N2 molecules by electron impact

The rotational excitation of the H₂ and N₂ molecules from (J→J+2,J=0) and (J→J+2,J=1) states by electron impact is studied, in the framework of the regional-plane-wave approximation. The empirical cut-off parameterρ, involved in these calculations, is varied to give the best fit to the experimental data of Srivastava and co-workers.     

Delicate interplay between the D0D?0, ρ0J/ψ, and ωJ/ψ channels in the X(3872) resonance

The nature of the X(3872) enhancement is analyzed in the framework of the Resonance-Spectrum Expansion, by studying it as a regular J ^PC =1⁺⁺ charmonium state, though strongly influenced and shifted by open-charm decay channels. The observed but Okubo–Zweig–Iizuka-forbidden ρ ⁰ J/ψ and ωJ/ψ channels are coupled as well, but effectively smeared out by using complex ρ ⁰ and ω masses, in order to account for their physical widths, followed by a rigorous algebraic procedure to restore unitarity. A very delicate interplay between the D ⁰ D ^∗0, ρ ⁰ J/ψ, and ωJ/ψ channels is observed. The data clearly suggest that the X(3872) is a very narrow axial-vector c[`(c)]c\bar{c} resonance, with a pole at or slightly below the D ⁰ D ^∗0 threshold.     

Analysis of the decays ψ′ → J/ψπ+π? and η′c → ηcπ+π? with the heavy-quark symmetry

In this article, we study the decays ψ′ → J/ψπ ⁺ π ⁻ and η′_c → η _c π ⁺ π ⁻ by taking into account the chiral symmetry breaking effects, the final-state interactions and the heavy-quark symmetry. We can confront the predictions of the η′_c → η _c π ⁺ π ⁻ decay width and differential decay width with the experimental data in the future, and obtain powerful constraints on the chiral breaking effects and the final-state interactions, and test the heavy-quark symmetry.