Search for the rare decays , , and

Rare decay modes , J/ψ→D⁻π⁺+c.c., and are searched for using events collected with the BESII detector at the BEPC. No signal above background is observed. We present upper limits on the branching fractions of , B(J/ψ→D⁻π⁺)<7.5×10⁻⁵, and at the 90% confidence level.     

Observation of γ-delayed 3α breakup of the 15.11 and 12.71 MeV states in C

The reactions at 4.9 MeV and at 8.5 MeV have been used to investigate the γ decay of states in ¹²C. By measuring the four-body final state in complete kinematics we are able to detect γ transitions indirectly. We find γ transitions from the 15.11 MeV state in ¹²C to the 12.71, 11.83, 10.3 and 7.65 MeV states followed by their breakup into three α particles. The relative γ-ray branching ratios obtained are (1.2±0.3), (0.32±0.12), (1.4±0.2) and (4.4±0.8)%, respectively, with the remaining (92.7±1.0)% of the γ decays going to the bound states. We obtain Γ_α/Γ=(2.8±1.2)% for the isospin-forbidden α decay of the 15.11 MeV state. From the 12.71 MeV state we find γ transitions to the 10.3 and 7.65 MeV states. The relative γ-ray branching ratios are and , respectively, with the remaining of the γ decays going to the bound states. Finally, we discuss the relation between the β decay of ¹²N and ¹²B to states in ¹²C and the γ decay of the 15.11 MeV analog in ¹²C to the same states.     

Graphic Bernstein results in curved pseudo-Riemannian manifolds

We generalize a Bernstein-type result due to Albujer and Alías, for maximal surfaces in a curved Lorentzian product 3-manifold of the form , to higher dimension and codimension. We consider M a complete spacelike graphic submanifold with parallel mean curvature, defined by a map f:Σ₁→Σ₂ between two Riemannian manifolds and of sectional curvatures K₁ and K₂, respectively. We take on Σ₁×Σ₂ the pseudo-Riemannian product metric g₁−g₂. Under the curvature conditions, and K₁≥K₂, we prove that, if the second fundamental form of M satisfies an integrability condition, then M is totally geodesic, and it is a slice if at some point. For bounded K₁, K₂ and hyperbolic angle θ, we conclude that M must be maximal. If M is a maximal surface and , we show M is totally geodesic with no need for further assumptions. Furthermore, M is a slice if at some point pΣ₁, K₁(p)>0, and if Σ₁ is flat and K₂<0 at some point f(p), then the image of f lies on a geodesic of Σ₂.     

Resonant Auger decay study of core-excited OCS

The present work aims at characterizing short-lived C1s⁽⁻¹⁾π^*(1) core-excited states of the OCS molecule based on the analysis of the vibrational fine structure and lineshape profiles of the high-resolution resonant Auger decay spectra recorded at the excitation energies along the C1s→π^* resonance in the binding energy region 15–19 eV. Very different behavior in terms of lineshape and resonant enhancement is observed for the , and final states. This is explained by (1) the variation in the C–O bond lengths for the states involved in the electronic relaxation and (2) different contributions in terms of Mulliken population to the molecular orbitals determining the electronic character of the corresponding states. Since the final-state geometries are known from a number of previous experiments and ab initio calculations, the geometry of the C1s⁽⁻¹⁾π^*(1) intermediate states can be predicted in analogy with e.g. the N₂, CO₂ and N₂O molecules.     

Photoproduction of and of high mass in ultra-peripheral Au + Au collisions at

We present the first measurement of photoproduction of J/ψ and of two-photon production of high-mass e⁺e⁻ pairs in electromagnetic (or ultra-peripheral) nucleus–nucleus interactions, using Au + Au data at . The events are tagged with forward neutrons emitted following Coulomb excitation of one or both Au nuclei. The event sample consists of 28 events with m_e⁺e⁻>2 GeV/c² with zero like-sign background. The measured cross sections at midrapidity of and for m_e⁺e⁻[2.0,2.8] GeV/c² have been compared and found to be consistent with models for photoproduction of J/ψ and QED based calculations of two-photon production of e⁺e⁻ pairs.     

Higgs-pair production and decay in simplest little Higgs model

In the framework of the simplest little Higgs model (SLHM), we study the production of a pair of neutral CP-even Higgs bosons at the LHC. First, we examine the production rate and find that it can be significantly larger than the SM prediction. Then we investigate the decays of the Higgs-pair and find that for a low Higgs mass their dominant decay mode is hh→ηηηη (η is a CP-odd scalar) while and hh→ηηWW may also have sizable ratios. Finally, we comparatively study the rates of , , and pp→hh→WWWW in the SLHM and the littlest Higgs models (LHT). We find that for a light Higgs, compared with the SM predictions, all the three rates can be sizably enhanced in the LHT but severely suppressed in the SLHM; while for an intermediately heavy Higgs, both the LHT and SLHM can enhance sizably the SM predictions.     

Cold nuclear matter effects on production: Intrinsic and extrinsic transverse momentum effects

Cold nuclear matter effects on J/ψ production in proton–nucleus and nucleus–nucleus collisions are evaluated taking into account the specific J/ψ-production kinematics at the partonic level, the shadowing of the initial parton distributions and the absorption in the nuclear matter. We consider two different parton processes for the -pair production: one with collinear gluons and a recoiling gluon in the final state and the other with initial gluons carrying intrinsic transverse momentum. Our results are compared to RHIC observables. The smaller values of the nuclear modification factor R_AA in the forward rapidity region (with respect to the mid rapidity region) are partially explained, therefore potentially reducing the need for recombination effects.     

Transition from resonances to surface waves in elastic scattering

In this article, we study resonances and surface waves in π⁺–p scattering. We focus on the sequence whose spin-parity values are given by . A widely-held belief takes for granted that this sequence can be connected by a moving pole in the complex angular momentum (CAM)-plane, which gives rise to a linear trajectory of the form , which is the standard expression of the Regge pole trajectory. But the phenomenology shows that only the first few resonances lie on a trajectory of this type. For higher J^p this rule is violated and is substituted by the relation JkR, where k is the pion-nucleon c.m.s. momentum, and R1 fm. In this article we prove: (a) Starting from a non-relativistic model of the proton, regarded as composed by three quarks confined by harmonic potentials, we prove that the first three members of this π⁺–p resonance sequence can be associated with a vibrational spectrum of the proton generated by an algebra . Accordingly, these first three members of the sequence can be described by Regge poles and lie on a standard linear trajectory. (b) At higher energies the amplitudes are dominated by diffractive scattering, and the creeping waves play a dominant role. They can be described by a second class of poles, which can be called Sommerfeld’s poles, and lie on a line nearly parallel to the imaginary axis of the CAM-plane. (c) The Sommerfeld’s pole which is closest to the real axis of the CAM-plane is dominant at large angles, and describes in a proper way the backward diffractive peak in both the following cases: at fixed k, as a function of the scattering angle, and at fixed scattering angle θ=π, as a function of k. (d) The evolution of this pole, as a function of k, is given in first approximation by JkR.     

Real next-to-next-to-leading-order QCD corrections to and hadroproduction in association with a photon

We update the study of the QCD corrections to direct J/ψ and hadroproduction in association with a photon in the QCD-based approach of the Colour-Singlet (CS) Model. After comparison with the recent full next-to-leading-order (NLO) computation for this process, we provide an independent confirmation to the inclusive case that NLO QCD corrections to quarkonium-production processes whose LO exhibits a non-leading P_T behaviour can be reliably computed at mid and large P_T by considering only the real emission contributions accompanied with a kinematical cut. In turn, we evaluate the leading part of the contributions, namely those coming from (J/ψ,)+γ associated with two light partons. We find that they are dominant at mid and large P_T. This confirms our expectations from the leading P_T scaling of the new topologies appearing at NNLO. We obtain that the yield from the CS becomes one order of magnitude larger than the upper value of the potential colour-octet yield. The polarisation of the quarkonia produced in association with a photon is confirmed to be longitudinal at mid and large P_T.     

Quasi-periodic solutions of nonlinear wave equations with quasi-periodic forcing

This work focuses on one-dimensional (1D) quasi-periodically forced nonlinear wave equations. This means studying with Dirichlet boundary conditions, where ε is a small positive parameter, (t) is a real analytic quasi-periodic function in t with frequency vector ω=(ω₁,ω₂…,ω_m) and the nonlinearity h is a real analytic odd function of the form It is shown that, under a suitable hypothesis on (t) and h, there are many quasi-periodic solutions for the above equation via KAM theory.     

Tree-level contributions to the rare decays , , and in the Standard Model

The tree-level contributions to the rare decays , , and are analyzed and compared to those occurring in , , and . It is shown that these purely long-distance contributions, arising from the exchange of a charged lepton, can be significant in B⁺ decays for an intermediate τ, potentially blurring the distinction between the modes used to extract B⁺→τ⁺ν_τ and those used to probe the genuine short-distance and FCNC transitions. Numerically, the tree-level contributions are found to account for 98%, 12% and 14% of the total , , and rates, respectively.     

Pseudo scalar contributions to light-by-light correction of muon in AdS/QCD

We have performed a holographic calculation of the hadronic contributions to the anomalous magnetic moment of the muon, using the gauge/gravity duality. As a gravity dual model of QCD with three light flavors, we study a U(3)_L×U(3)_R flavor gauge theory in the five-dimensional AdS background with a hard-wall cutoff. The anomalous (electromagnetic) form factors for the pseudo scalars, π⁰, η and η^′, are obtained from the 5D Chern–Simons term of the gravity dual, which correctly reproduce the asymptotic behavior of the form factor, dictated by QCD. We find the total light-by-light contributions of pseudo scalars to the muon anomalous magnetic moment, , which is consistent with previous estimates, based on other approaches.     

Fractional quasiexcitons in incompressible electron liquids

A new kind of many-body excitonic state composed of fractionally charged constituents is introduced. The constituents are a trion (X^-) embedded in an incompressible electron liquid and Laughlin quasiholes (QH's). Laughlin electron–trion correlations lead to an effective trion charge of -e/3. This many-body excitation is called “quasiexciton” and denoted by to distinguish it from a normal trion. The can bind one or two (e/3)-charged QH's, giving a neutral or a positive . The energy spectra and photoluminescence from radiative quasiexciton decay are studied numerically and interpreted using a generalized composite Fermion model of the e–X^- fluid.     

Flame stabilization in high pressure LOx/GH2 and GCH4 combustion

Planar laser induced fluorescence (PLIF) of OH is used to examine flame stabilization in high pressure cryogenic flames formed by injecting a central jet of low speed liquid oxygen surrounded by a high speed gaseous stream of hydrogen or methane. In the LO_x/GH₂ experiments injection conditions are transcritical as the chamber pressure is above critical but the temperature is below critical . In the LO_x/GCH₄ experiments the chamber pressure and LO_x injection temperature are below critical , . Hydrogen or methane are injected at room temperature LIF images delineate the flame edge in the injector nearfield. The two flames are stabilized in the vicinity of the liquid oxygen injector lip but the anchor point is found to lie closer to the lip in the LO_x/GH₂ case and its displacement from shot to shot is of a smaller amplitude than that corresponding to the LO_x/GCH₄ flame. Interpretation of these data is based on a previous analysis which indicates that stabilization is essentially controlled by a dimensionless group formed by comparing the lip thickness to the flame edge thickness Ψ = h_s/δ_f. It is found that Ψ slightly exceeds unity in the LO_x/GH₂ case essentially fulfilling the stability condition while Ψ < 1 in the LO_x/GCH₄ case. In this last situation the flame is thicker than the characteristic thickness h_s and it is therefore sensitive to the high speed methane stream. Anchoring is imperfect and the flame edge moves with the turbulent eddies shed from the lip. Global stabilization is achieved dynamically but the reactive layer is not well established and the large amplitude motion of the edge is a symptom of a possible lift-off. Theoretical estimates indicate that LO_x/GCH₄ flame stabilization requires a thicker lip size than the LO_x/GH₂ propellant couple.     

The polarised valence quark distribution from semi-inclusive DIS

The semi-inclusive difference asymmetry A^h+−h− for hadrons of opposite charge has been measured by the COMPASS experiment at CERN. The data were collected in the years 2002–2004 using a 160 GeV polarised muon beam scattered off a large polarised ⁶LiD target in the kinematic range 0.006<x<0.7 and 1<Q²<100 (GeV/c)². In leading order QCD (LO) the deuteron asymmetry A^h+−h− measures the valence quark polarisation and provides an evaluation of the first moment of Δu_v+Δd_v which is found to be equal to 0.40±0.07(stat.)±0.06(syst.) over the measured range of x at Q²=10 (GeV/c)². When combined with the first moment of previously measured on the same data, this result favours a non-symmetric polarisation of light quarks at a confidence level of two standard deviations, in contrast to the often assumed symmetric scenario .     

Unfamiliar integrals and motions down the ‘plug-hole’ potential

The orbits in the potentials ψ=−CzR⁻²+ζ(R), (ζ arbitrary) have integrals E, and . Thus the z-velocity is proportional to the number of turns made around the axis! The Poisson Bracket [h,I] is not zero so Liouville’s integrability theorem does not apply. Starting from the self-similar potential with ζ∝R⁻¹, we find some orbits that spiral around cones and explore general orbits in this strange system.     

Effects of time reversal symmetry on phonons in sapphire substrate for ZnO and GaN

Vibrational states in a crystal are classified according to the irreducible representations (irreps) of the corresponding factor group . The wave vector k runs over the entire Brillouin zone (BZ). For trigonal BZs, the factor groups are determined by the symmetry points Γ, F, L, T, and the symmetry lines Λ, Σ, Y. When the irreps are complex, the time reversal symmetry has to be taken into account. Using the Frobenuis–Schur criterion adapted to space groups with real and complex irreps, we have investigated high symmetry points and lines of the phonons in trigonal crystals: Cr₂O₃,Fe₂O₃,Ti₂O₃,V ₂O₃,FeCO₃,CaCO₃,CdCO₃,MgCO₃,MnCO₃,NaCO₃ and ZnCO₃, with the common space group (). We have found several phonons which are influenced by the time reversal symmetry. Therefore, an extra degeneracy of phonons arises. The theoretical results are also compared with available experimental data.     

On the high resolution spectroscopy and intramolecular potential function of SO2

Two weak stretching bands, ν₁ + 3ν₃ and 3ν₁ + ν₃, of the sulfur dioxide molecule have been recorded at high resolution and analyzed for the first time with using a Fourier transform Bruker IFS-120 HR interferometer. About 1000 transitions with J^max. = 51, , and 900 transitions with J^max. = 53, have been assigned to the bands ν₁ + 3ν₃ and 3ν₁ + ν₃, respectively. Analysis of the recorded spectra was made using the model of isolated vibrational states. Parameters obtained from the fit reproduce the initial experimental ro-vibrational energies with the rms deviation of 0.0006 and 0.0012 cm⁻¹ for the bands, 3ν₁ + ν₃ and ν₁ + 3ν₃, respectively. The problem of determination of the intramolecular potential function of SO₂ is discussed.     

Non-Abelian duality from vortex moduli: A dual model of color-confinement

It is argued that the dual transformation of non-Abelian monopoles occurring in a system with gauge symmetry breaking G→H is to be defined by setting the low-energy H system in Higgs phase, so that the dual system is in confinement phase. The transformation law of the monopoles follows from that of monopole-vortex mixed configurations in the system (with a large hierarchy of energy scales, v₁v₂) , under an unbroken, exact color-flavor diagonal symmetry . The transformation property among the regular monopoles characterized by π₂(G/H), follows from that among the non-Abelian vortices with flux quantized according to π₁(H), via the isomorphism π₁(G)π₁(H)/π₂(G/H). Our idea is tested against the concrete models—softly-broken supersymmetric SU(N), SO(N) and USp(2N) theories, with appropriate number of flavors. The results obtained in the semiclassical regime (at v₁v₂Λ) of these models are consistent with those inferred from the fully quantum-mechanical low-energy effective action of the systems (at v₁,v₂Λ).