Magnetic moment of the pentaquark Θ+(1540) as diquark-diquark-antiquark state with QCD sum rules

In this article, we study the magnetic moment of the pentaquark state Θ⁺(1540) as a diquark-diquark-antiquark ( ) state with the QCD sum rules in an external weak electromagnetic field (EFSR) and the light-cone QCD sum rules (LCSR) respectively. The numerical results indicate that the magnetic moment is about for the EFSR and - for the LCSR. As the values obtained from the EFSR are more stable than the corresponding ones from the LCSR, is more reliable. Received: 29 March 2005, Revised: 28 June 2005, Published online: 21 October 2005 PACS: 12.38.Aw, 12.38.Lg, 12.39.Ba, 12.39.-x     

Reanalyzing Pentaquark Θ+(1540) in Framework of QCD Sum Rules Approach with Direct Instantons

In this article, we study the pentaquark state Θ⁺(1540) with a (scalar) diquark-(pseudoscalar) diquark-antiquark type interpolating current in the framework of the QCD sum rules approach by including the contributions from the direct instantons. The numerical results indicate that the contributions from the direct instantons are very small and can be safely neglected.     

A new search for the doubly charmed baryon ■ at the LHC

The standard quark model is capable of predicting the existence of doubly heavy baryons.Similar to doubly heavy mesons,doubly heavy baryons may allow the QCD-inspired potential model,the nonrelativistic QCD(NRQCD)factorization theory[1],etc.,to work on them well,while serving as a fruitful“laboratory”for testing these theories when a greatly enough collection of relevant data is available.Many attempts have been made to observe doubly heavy baryons,yet none of them succeeded due to the difficulties in producing such baryons either at the e^+e^- colliders or at the hadronic colliders.Noticeably,the running of the large hadronic collider(LHC)with a large centre-of-mass protonproton collision energy and a much higher luminosity provides a good opportunity for experimentalists to realize the aforementioned observation.     

Bound-state versus collective-coordinate approaches in chiral soliton models and the width of the Θpentaquark

We thoroughly compare the bound-state and rigid-rotator approaches to three-flavored chiral solitons. We establish that these two approaches yield identical results for the baryon spectrum and kaon-nucleon S-matrix in the limit that the number of colors (N_C) tends to infinity. After proper subtraction of the background phase shift the bound-state approach indeed exhibits a clear resonance behavior in the strangeness S = + 1 channel. We present a first dynamical calculation of the widths of the Θ⁺ and Θ^* pentaquarks for finite N_C in a chiral soliton model.     

Search for rare radiative decays ofΦ-meson at VEPP-2M

Results of the search for rare radiative decay modes of the ?-meson performed with the Neutral Detector at the VEPP-2M collider are presented. For the first time upper limits for the branching ratios of the following decay modes have been placed at 90% confidence level: $$\begin{gathered} B(\phi \to \eta '\gamma )< 4 \cdot 10^{ - 4} , \hfill \\ B(\phi \to \pi ^0 \pi ^0 \gamma )< 10^{ - 3} , \hfill \\ B(\phi \to f_0 (975)\gamma )< 2 \cdot 10^{ - 3} , \hfill \\ B(\phi \to H\gamma )< 3 \cdot 10^{ - 4} , \hfill \\ \end{gathered} $$ whereH is a scalar (Higgs) boson with a mass 600 MeV<m _H <1000 MeV, the real measurement isB(φ→H γ)·B(H→2π⁰)<0.8·10^-4, the quoted result is model dependent, as explained in the text, $$\begin{gathered} B(\phi \to a\gamma ) \cdot B(a \to e^ + e^ - )< 5 \cdot 10^{ - 5} , \hfill \\ B(\phi \to a\gamma ) \cdot B(a \to \gamma \gamma )< 2 \cdot 10^{ - 3} , \hfill \\ \end{gathered} $$ wherea is a particle with a low mass and a short lifetime, $$B(\phi \to a\gamma )< 0.7 \cdot 10^{ - 5} ,$$ wherea is a particle with a low mass not observed in the detector.     

A search for decays of heavy neutrinos in the mass range 0.5–2.8 GeV

A search for decays of heavy neutrinos was conducted by the CHARM Collaboration in a prompt neutrino beam produced by dumping 400 GeV protons in a Cu target, and in the CERN wide-band neutrino beam produced by 400 GeV primary protons. No candidate event was found. In the beam-dump experiment heavy neutrinos have been assumed to be produced by mixing in charmed D meson decays. Neutrinos decaying into e⁺e⁻v_e, μ⁺e⁻v_μ, and μ⁺μ⁻v_μ were searched for. Limits of |U_ei|², |U_μi|² < 10⁻⁷ were obtained for neutrino masses around 1.5 GeV. In the wide-band experiment heavy neutrinos were assumed to be produced by neutral-current neutrino interactions in the CHARM calorimeter. Here a search was made for neutrinos decaying into a μ and hadrons. This experiment is sensitive to decays of neutrinos with mass in the range 0.5–2.8 GeV with limits of |U_μi|² < 3 × 10⁻⁴ for masses around 2.5 GeV. These measurements extend our previous results in the mass range 10–400 MeV.     

Observation of Cabibbo-suppressed and W-exchange Λ c + baryon decays

We present measurements of the Cabibbo-suppressed decays Λ _c ⁺→Λ ⁰ K ⁺ and Λ _c ⁺→Σ ⁰ K ⁺ (both first observations), Λ _c ⁺→Σ ⁺ K ⁺ π ⁻ (seen with large statistics for the first time), Λ _c ⁺→pK ⁺ K ⁻ and Λ _c ⁺→pφ (measured with improved accuracy). Improved branching ratio measurements for the decays Λ _c ⁺→Σ ⁺ K ⁺ K ⁻ and Λ _c ⁺→Σ ⁺ φ, which are attributed to W-exchange diagrams, are shown. We also present the first evidence for Λ _c ⁺→Ξ(1690)⁰ K ⁺ and set an upper limit on the non-resonant decay Λ _c ⁺→Σ ⁺ K ⁺ K ⁻. This analysis was performed using 32.6 fb⁻¹ of data collected by the Belle detector at the asymmetric e ⁺ e ⁻ collider KEKB.     

Production of light superpartners in π0 radiative decays

The production rate of light photinos in radiative pion decay \(\pi ^0 \to \gamma \tilde \gamma \tilde \gamma\) is calculated. Experimental constraints on masses and mass splittings of scalar quarks imply the following upper bound on the decay rate \(BR(\pi ^0 \to \gamma \tilde \gamma \tilde \gamma ) \lesssim 10^{ - 16}\) .     

K→ππγ decays: A search for novel couplings in kaon decays

We analyzeK decays in the framework of Chiral Perturbation Theory. We study the different Dalitz plot distributions, trying to find regions whereo(p ⁶) contributions could be more easily detected. To fulfill this program we compute all theo(p ⁴) loop and counterterm contributions, finding a substantial agreement with the existing calculations and adding some small missing terms inK _S ^+–.Work supported in part by the Human Capital and Mobility Program, EEC Contract N. CHRX-CT920026     

Search for hadronic decays of a light Higgs boson in the radiative decay Υ→γA0

We search for hadronic decays of a light Higgs boson (A(0)) produced in radiative decays of an Υ(2S) or Υ(3S) meson, Υ→γA(0). The data have been recorded by the BABAR experiment at the Υ(3S) and Υ(2S) center-of-mass energies and include (121.3±1.2)×10(6) Υ(3S) and (98.3±0.9)×10(6) Υ(2S) mesons. No significant signal is observed. We set 90% confidence level upper limits on the product branching fractions B(Υ(nS)→γA(0))B(A(0)→hadrons) (n=2 or 3) that range from 1×10(-6) for an A(0) mass of 0.3 GeV/c(2) to 8×10(-5) at 7 GeV/c(2).     

First lattice QCD calculation of semileptonic decays of charmed-strange baryon Ξc

While the standard model is the most successful theory to describe all the interactions and constituents of elementary particle physics,it has been constantly s...     

Search for f(J)(2220) in radiative J/ψ decays

We present a search for f(J)(2220) production in radiative J/ψ→γf(J)(2220) decays using 460 fb?1 of data collected with the BABAR detector at the SLAC PEP-II e(+)e? collider. The f(J)(2220) is searched for in the decays to K(+)K? and K(S)?K(S)?. No evidence of this resonance is observed, and 90% confidence level upper limits on the product of the branching fractions for J/ψ→γf(J)(2220) and f(J)(2220)→K(+)K?(K(S)?K(S)?) as a function of spin and helicity are set at the level of 10??, below the central values reported by the Mark III experiment.     

Experimental evidence for the box anomaly inη/η′ decays and the electric charge of quarks

Motivated by nearly unanimous claim that the observed mass spectrum ^+- is not that expected from pure ⁰ dominance, we reanalyze all the published data on / ^+- decays. We find non-resonant contributions. In order to evaluate precisely the magnitude of these terms, we also refit the e⁺e^{- +-} data to get reliably the ⁰ parameters and decay amplitude. We show that identifying the non-resonant contribution with the box anomaly predicted by QCD and chiral theories, one achieves a consistent picture. Several checks are performed which show the consistency of our fitted parameters. From four measurements, we determinef ₁,f ₈ and _PS on purely experimental grounds, and we find them in the expected range. Presently available data allow for two solutions, one is consistent with QCD, the other favours integral charge quark models. We show that presently available data do not allow to choose among these two solutions. We discuss the interrelation of uncertainties in e⁺e^{- +-} physics with our two solutions.     

Search for the Θ<Superscript>+</Superscript> pentaquark: experimental statuspentaquark: experimental status

The possible existence of a baryon with strangeness S=+1, the Θ⁺(1540), is presently one of the most exciting topics in hadron physics. Such a state must minimally posses 4 quarks together with one valence\(\bar s\) antiquark. The current experimental status of searches for the Θ⁺(1540) is reviewed, open questions and future prospects are discussed.     

Production of pseudoscalar glueballs in J/ψ radiative decays

Using a previously developed framework for relativistic bound states we calculate the production of pseudoscalar glueballs in J/ψ radiative decays. The results favour the interpretation of ι(1460) as a fairly pure glueball state. Radiative production of ι(1460) in ϒ and toponium decays should be suppressed.     

Search for the doubly charmed baryon ■

A search for the doubly charmed baryon Ξ_(cc)~+ is performed through its decay to the Λ_c~+K~-π~+ final state, using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 Te V. The data correspond to a total integrated luminosity of 9 fb~(-1). No significant signal is observed in the mass range from 3.4 to 3.8 Ge V/c~2. Upper limits are set at 95% credibility level on the ratio of the Ξ_(cc)~+ production cross-section times the branching fraction to that of Λ_c~+ and Ξ_(cc)~(++) baryons. The limits are determined as functions of the Ξ_(cc)~+ mass for different lifetime hypotheses, in the rapidity range from 2.0 to 4.5 and the transverse momentum range from 4 to 15 GeV/c.     

Measurement of polarization and search for CP violation in B(s)0→φφ decays

We present the first measurement of polarization and CP-violating asymmetries in a B(s)(0) decay into two light vector mesons, B(s)(0)→φφ, and an improved determination of its branching ratio using 295 decays reconstructed in a data sample corresponding to 2.9 fb(-1) of integrated luminosity collected by the CDF experiment at the Fermilab Tevatron collider. The fraction of longitudinal polarization is determined to be f(L)=0.348±0.041(stat)±0.021(syst), and the branching ratio B(B(s)(0)→φφ)=[2.32±0.18(stat)±0.82(syst)]×10(-5). Asymmetries of decay angle distributions sensitive to CP violation are measured to be A(u)=-0.007±0.064(stat)±0.018(syst) and A(v)=-0.120±0.064(stat)±0.016(syst).     

Experimental search for the radiative capture reaction d + d → 4He + γ from the ddμ muonic molecule state J = 1

A search for the muon-catalyzed fusion reaction d + d → ⁴He + γ in the ddμ muonic molecule was performed using the experimental installation TRITON with BGO detectors for γ-quanta. A high-pressure target filled with deuterium was exposed to the negative muon beam of the JINR Phasotron to detect γ-quanta with the energy 23.8 MeV. An experimental estimation for the yield of radiative deuteron capture from the ddμ state J = 1 was obtained at the level of η _γ ≤ 8 × 10^?7 per fusion.