Narrow Results

In this contribution, we give a brief overview over the historical development of shell-model-related experimental and theoretical nuclear physics activities at KTH Royal Institute of Technology that benefited from the classic Kuo–Brown interaction and the fundamental insight of Kuo on the core polarization effect.

In this paper, we study the Maxwell equations in the domain of outer-communication of the Schwarzschild black hole. We prove that if the middle components of the non-stationary solutions of the Maxwell equations verify a Morawetz-type estimate supported on a compact region in space around the trapped surface, then the components of the Maxwell fields decay uniformly in the entire exterior of the Schwarzschild black hole, including the event horizon. This is shown by making only use of Sobolev inequalities combined with energy estimates using the Maxwell equations directly. The proof does not pass through the scalar wave equation on the Schwarzschild black hole, does not need to decouple the middle components for the Maxwell fields, and would be in particular useful for the non-abelian case of the Yang–Mills equations where the decoupling of the middle components cannot occur. In fact, the estimates for the hereby argument are still valid for the Yang–Mills fields except for the Lie derivatives of the fields that are involved in the proof.

The conversion ν_L→ν_Rγ* of a neutrino with a magnetic moment is considered, caused by the additional Wolfenstein energy acquired by a left-handed neutrino in medium, with an accurate account of the photon γ* dispersion in medium. It is shown that the threshold arises in the process, caused by the photon (plasmon) effective mass. This threshold leaves no room for the so-called "neutrino spin light" in the most of astrophysical situations.

The complicated processes in medium (decays, reactions and transitions) involving final state absorption are considered. The calculations in the framework of field-theoretical and phenomenological approaches are compared. The reasons for disagreement are studied. The field-theoretical approach can tend to increase the total process probability as well as probability of channel corresponding to absorption, in comparison with phenomenological model.

The status of conventional baryon flux-tubes and hybrid baryons is reviewed. Recent surprises are that a model prediction indicates that hybrid baryons are very weakly produced in glue-rich Ψ decays, and an analysis of electro-production data concludes that the Roper resonance is not a hybrid baryon. The baryon decay flux-tube overlap has been calculated in the flux-tube model, and is discussed here. The behavior of the overlap follows naïve expectations.

We study the radiative ρ, ω and ϕ decay into π⁰π⁰γ and π⁰ηγ taking into account mechanisms in which there are two sequential vector-vector-pseudoscalar or axial-vector–vector–pseudoscalar steps followed by the coupling of a vector meson to the photon, considering the final state interaction of the two mesons. Other mechanisms in which two kaons are produced through the same sequential mechanisms or from vector meson decay into two kaons which undergo final state interaction leading to the final pair of pions or π⁰η, are also considered. The results of the parameter free theory, together with the theoretical uncertainties, are compared with the latest experimental results at Frascati and Novosibirsk.

Investigations of the mass and decays of the J^PC=1^-+ hybrid are reviewed, including calculation of the π₁(1^-+)→ηπ, η′π decay widths within the QCD sum rules technique. In this calculation, the recently-proposed η, η′ quark mixing scheme is employed. The results indicate that the decay width Γ_π1→ηπ≈250 MeV is large compared with the decay width Γ_{π1→η′π}≈20 MeV. Inspired by these results, some phenomenological approaches are suggested to gain an understanding of the underlying mechanism of ηπ and η′π hybrid decays.

We analyze the features of the near-horizon conformal symmetry of black holes from an algebraic point of view. The implications of such a symmetry for black hole entropy and decay are also discussed.

We report on a search for the flavor-changing neutral current decays D⁰ → e⁺e^- and D⁰ → μ⁺μ^-, and the lepton-flavor violating decay D⁰ → e^±μ^∓. The measurement is based on 122 fb^-1 of data collected by the BABAR detector at the PEP-II asymmetric e⁺e^- collider. No evidence is found for any of the decays. The upper limits on the branching fractions, at the 90% confidence level, are 1.2 × 10^-6 for D⁰ → e⁺e^-, 1.3 × 10^-6 for D⁰ → μ⁺μ^-, and 8.1 × 10^-7 for D⁰ → e^±μ^∓.

Studies on the decay and production of meson are briefly reviewed. Considering RUN-II of Tevatron and the schedule of LHC, the theoretical studies of B_c meson will jump to a new stage not only for itself but also to implement the studies of the heavy quarkonia etc.

In this conference presentation I discuss CLEO-c opportunities in Dalitz plot analyzes with the data samples available now and projected by the end of CESR-c run. Using 281 pb^-1 of e⁺e^- collisions at mass of ψ(3770) we present results of the Dalitz plot analysis of D⁺ → π^-π⁺π⁺. Using the CLEO-c and CLEO III samples of 5 pb^-1, accrued at mass of ψ(2S), we study three body decays of χ_cJ produced in the radiative decay ψ(2S) → γχ_cJ, where J=0,1,2. A clear signal from at least one of χ_cJ is found in eight final states: π⁺π^-η, π⁺π^-η′, K⁺K^-π⁰, , ηK⁺K^-, , , and . For these modes we measured or set an upper limit on the branching fraction. A Dalitz plot analysis is performed on three modes χ_c1 → π⁺π^-η, K⁺K^-π⁰, and .

The fermion spin–flip conversion f_L → f_R + γ is considered, caused by the difference of the additional energies of the electroweak origin, acquired by left- and right-handed fermions (neutrino, electron) in medium. An accurate analysis of the fermion and photon dispersion in medium is performed. It is shown that the threshold arises in the process, caused by the photon (plasmon) effective mass. This threshold leaves no room for the so-called "spin light of neutrino" and "spin light of electron" in the real astrophysical situations.

We reported the observation of Y(2175) in ϕf₀(980) mass spectrum in J/ψ → ηϕf₀(980) with f₀(980) → π⁺π^-, the partial wave analysis results of J/ψ → γϕϕ, the measurement of , , and the observation of threshold enhancement in , based on 5.8 × 10⁷ J/ψ events collected at BESII. The measurement of ψ(2S) radiative decays with 1.4 × 10⁷ ψ(2S) events as well as the measurement of D decay branching fractions with 33 pb^-1 data collected at and around 3.773 GeV are also presented.

In this paper, we investigate the three-body decays of $D_s$ meson to $\eta \pi \pi$ and ${\eta }^{\prime }\pi \pi$ final state mesons, using a simple model based on the framework of the factorization approach. As we know, there are tree and emission-annihilation diagrams for these decay modes in the factorization approach. We calculate the total $D_s^{+}\to \eta {\pi }^{+}{\pi }^0$ and $D_s^{+}\to {\eta }^{\prime }{\pi }^{+}{\pi }^0$ branching ratios, including the nonresonant and resonances contributions, and in view of the $\eta -{\eta }^{\prime }$ mixing, by applying the Dalitz plot analysis and obtain $(5.55\pm 0.08)\times 10^{-2}$ and $(3.69\pm 0.07)\times 10^{-2}$, while the experimental values are $(9.2\pm 1.2)\times 10^{-2}$ and $(5.6\pm 0.8)\times 10^{-2}$, respectively. The branching ratios obtained in our model are partly compatible with the experimental results.

In this work, the mass spectrum of the first radial excitation axial vector meson nonet is considered in the framework of the nonrelativistic constituent quark model and Regge phenomenology. After that, we investigate the strong decay characteristics of these states within the ${}^3{P}_0$ model. The results are compared to values from other phenomenological models, and they may be beneficial in the prospective search for $2^3{P}_1$ meson nonets.

In this study, singly charm baryons ${\mathrm{\Lambda }}_c$, ${\mathrm{\Sigma }}_c$, ${\mathrm{\Xi }}_c$ and ${\mathrm{\Omega }}_c$ have been studied. The known hypercentral Constituent Quark Model (hCQM) has been subjected to an addition of second-order correction term to the mass in spin-dependent term. This has allowed to observe the expected spin-splitting in the correct order and modify the previous findings to a new level. All the other properties have been obtained ranging from magnetic moment to strong decay width along with the linearly observed Regge trajectories.

We study the global well-posedness and asymptotic behavior for a semilinear damped wave equation with Neumann boundary conditions, modeling a one-dimensional linearly elastic body interacting with a rigid substrate through an adhesive material. The key feature of of the problem is that the interplay between the nonlinear force and the boundary conditions allows for a continuous set of equilibrium points. We prove an exponential rate of convergence for the solution towards a (uniquely determined) equilibrium point.

The decay of bromine-76 was studied using high resolution HpGe detectors in singles and coincidence mode. Bromine-76 was produced via two reactions: ⁷⁵As(α,3n)⁷⁶Br and ⁷⁶Se(p,n)⁷⁶Br. The results of these experiments verified the previously reported levels of ⁷⁶Se. In addition to the previously described transitions and levels, 37 new γ-rays and 15 new energy levels were found for the first time.

The history and importance of superdeformation in nuclei is briefly discussed. A simple two-level model is then employed to obtain an elegant expression for the branching ratio for the decay via the E1 process in the normal-deformed band of superdeformed nuclei. From this expression, the spreading width Γ^↓ for superdeformed decay is found to be determined completely by experimentally known quantities. The accuracy of the two-level approximation is verified by considering the effects of other normal-deformed states. Furthermore, by using a statistical model of the energy levels in the normal-deformed well, we can obtain a probabilistic expression for the tunneling matrix element V.

The decay of ⁷²As has been investigated by means of γ-ray spectroscopy. The ⁷²As nuclei were produced through the ⁷²Ge(p, n)⁷²As reaction. The Compton-suppressed spectrometer and high-purity Ge detectors have been used in singles and in coincidence modes respectively to study γ-rays in the β⁺+EC decay of ⁷²As to ⁷²Ge. 79 γ-rays, among which 3 were observed for the first time, were reported. A decay scheme of ⁷²As including 1 new level is proposed that accommodates 77 of these transitions. Tentative spin and parity assignments are suggested for a number of levels according to the log ft values and γ-branching ratios.