Hidden local symmetry and the reaction e+e- → \pi^{+}_{} \pi^{-}_{} \pi^{+}_{} \pi^{-}_{} at energies \sqrt{{s}} ⩽ 1 GeV

Based on the generalized hidden local symmetry as the chiral model of pseudoscalar, vector, and axial vector mesons, the excitation curve of the reaction e ⁺ e ^- → $ \pi^{+}_{}$ $ \pi^{-}_{}$ $ \pi^{+}_{}$ $ \pi^{-}_{}$ is calculated for energies in the interval 0.65 ? $ \sqrt{{s}}$ ? 1 GeV. The theoretical predictions are compared to available data of CMD-2 and BaBaR. It is shown that the inclusion of heavy isovector resonances ρ(1450) and ρ(1700) is necessary for reconciling calculations with the data. It is found that at $ \sqrt{{s}}$ ≈ 1 GeV the contributions of the above resonances are much larger, by a factor of 30, than the ρ(770) one, and amount to a considerable fraction ～ 0.3-0.6 of the latter at $ \sqrt{{s}}$ ～ m _ρ .     

The controversy in theγγ →ρρ process: potential scattering or qq\bar q};\bar q}; resonance?; resonance?

Theγγ →ρ ⁰ ρ ⁰ → 4π reaction shows a broad peak at 1.5 GeV in the (J ^P ,J _z )=(2⁺,2) channel which has no counterpart in theρ ⁺ ρ ^? channel. This “resonance” is considered as a candidate for a qq $\bar q$ ; $\bar q$ state in the “s-channel”. We show, however, that it can also be explained by potential scattering ofρ ⁰ ρ ⁰ via theσ- exchange in the “t-channel”.     

Manifestation of a singlet heavy up-type quark in the branching ratios of rare decays K → πν \bar \nu , B → πν \bar \nu , and B → Kν \bar \nu

The implications of the model with a SU(2)-singlet up-type quark, heavy enough not to be produced at the LHC, namely, the contribution of the new quark to the branching ratios of the K → πν $ \bar \nu $ , B → πν $ \bar \nu $ , and B → Kν $ \bar \nu $ decays are investigated. It is shown that the deviation from the Standard Model can be up to 10% in the case of a 5-TeV quark. Precise measurements of these branching ratios in future experiments will allow for the observation of the contributions of the new quark or to impose stronger constraints on its mass.     

Energy dependence of e + e − → 6π and e + e − → N\bar N cross sections near N\bar N the threshold

Using recent BABAR, CMD-3 and SND data, the sum of e ⁺ e ^? → 3(π⁺π^?), 2(π⁺π^?π⁰), \(p\bar p\) , \(n\bar n\) cross sections is obtained. Unlike e ⁺ e ^? 3(π⁺π^?) and e ⁺ e ^? → 2(π⁺π^?π⁰) processes, no structures in total cross section are found near the \(N\bar N\) threshold within the limits of measurement errors.     

On the radiative decay of orthoquarkonium via two intermediate gluons: 1−− (Q \bar Q) → γ+1++ (q \bar q)

We investigate the decay of a heavy³ S ₁ (Q \(\bar Q\) vector meson into a real photon and two off-shell intermediate gluons which create a³ P ₁(q \(\bar q\) ) axial vector meson. As an application we suggest to look for the decayJ/?→ψ+D(1285) andΥ→γ₁+P _c /χ₁++→γ₁→γ₂+J/ψ.     

The role of the P11(1710) in the NN → NΣK reaction

Using the resonance model, which was successfully applied for the study of the pp → pΛK⁺ reaction, we investigate NN → NΣK reactions that are expected to provide cleaner information about resonance excitations and meson exchange contributions. For this purpose we demonstrate that the invariant mass distribution for the ΣK system, as well as the Dalitz plot for the NN → NΣK reaction, provide direct information about the ΣK production mechanism, which can be tested in the near future by experiments at COSY.     

Testing the nature of the Λ(1520) in the J/ψ → \bar \Lambda K-p and J/ψ → \bar \Lambda π+π-Λ reactions

We study the reactions J/ψ → $ \bar \Lambda $ K ^- p and J/ψ → $ \bar \Lambda $ π⁺π^-Λ with a unitary chiral approach. We predict the ratio of the invariant-mass distributions of these two reactions at the Λ(1520) peak position, which is free of the unknown production mechanism and reflects only the properties of the Λ(1520) . An experimental measurement of this ratio will provide the couplings of the Λ(1520) to its decay channels, allowing to test the predictions of the chiral unitary approach on this resonance, which appears as dynamically generated in that approach.     

Detailed Investigation of Neutron–Neutron Angular Correlations in the Spontaneous Fission of $${}^{{252}}$$ Cf

Physics of Atomic Nuclei - New precise measurements of angular neutron–neutron ( $$nn$$ ) correlations in the spontaneous fission of $${}^{252}$$ Cf were performed with the aim of studying...     

The N*(1710) as a resonance in the ππN system

We study the ππN system by solving the Faddeev equations, for which the input two-body t-matrices are obtained by solving the Bethe-Salpeter equation in the coupled-channel formalism. The potentials for the ππ, πN sub-systems and their coupled channels are obtained from chiral Lagrangians, which have been earlier used to study resonances in these systems successfully. In this work, we find a resonance in the ππN system with a mass of 1704 ? i375/2MeV and with quantum numbers I = 1/2, J ^π = 1/2⁺. We identify this state with the N ^*(1710). This peak is found where the energies of the ππ sub-system fall in the region of the σ-resonance. We do not find evidence for the Roper resonance in our study indicating a more complex structure for this resonance, nor for any state with total isospin I = 3/2 or 5/2.     

Calibration of absolute jet energy scale in CMS detector using W → q \bar q process in pp-Collisions at \sqrt s = 7 TeV

Calibration of absolute jet energy scale in CMS experiment at $\sqrt s = 7$ TeV using the W-mass constraint in t $\bar t$ -events with W ?? q $\bar t$ decay is made. Data sample with an integrated luminosity of 3 fb^?1 is used. Calibration procedure is made for calorimetric jets, ??Jet-Plus-Track?? jets, and ??Particle-Flow?? jets. Statistical errors of calibration as well as systematical uncertainties of the method are up to 3%. The results are abstracted from degree thesis.     

Determination of the Dalitz plot parameter \alpha for the decay \eta → 3 \pi^{0}_{} with the Crystal Ball at MAMI-B

A precise measurement of the Dalitz plot parameter, $ \alpha$ , for the $ \eta$ → 3 $ \pi^{0}_{}$ decay is presented. The experiment was performed with the Crystal Ball and TAPS large-acceptance photon detectors at the tagged photon beam facility of the MAMI-B electron accelerator in Mainz. High statistics of 1.8 · 10⁶ $ \eta$ → 3 $ \pi^{0}_{}$ events were obtained, giving the result $ \alpha$ = - 0.032±0.002_stat±0.002_syst .     

On the contribution of interference of electromagnetic and chromomagnetic dipole operators in the $$ \bar B $$ → Xsγ decay at O(αs2)

The contribution of c-quark loops into the interference of the electromagnetic and chromomagnetic dipole operators in the \(\bar B\) → X _s γ decay is calculated to O(α _s ² ) within the framework of the Standard Model (SM). Several new calculation techniques, such as Laporta’s automated algorithm, the second order decomposition method, and Mellin-Barnes representation, have been used.     

Comparison of Methods for Eliminating the Bohr–Weisskopf Effect in Atomic Spectra of $${}^{{209}}$$ Bi Heavy Ions

Physics of Atomic Nuclei - The methods of the ratio and specific differences of values of hyperfine splitting in different shells for eliminating the Bohr–Weisskopf effect in...     

Measurement of \Sigma beam asymmetry in \pi^{0}_{} photoproduction off the neutron in the second and third resonances region⋆

The $ \Sigma$ beam asymmetry in the photoproduction of neutral pions from quasi-free nucleons in a deuteron target was measured for the first time between 0.60 and 1.50GeV, with the GRAAL polarized and tagged photon beam. The asymmetry values from the quasi-free proton were found equal to the ones extracted from a pure proton target. The asymmetries from quasi-free proton and quasi-free neutron were found equal up to 0.82GeV and substantially different at higher energies. The results are compared with recent partial-wave analyses.     

Experimental test of the PCAC hypothesis in the reactionsv μ p→ μ− pπ+ and \bar v_\mu p \to \mu ^ + p\pi ^ - in theΔ(1232) region

Data on the reactionsv _μ p→ μ^? pπ⁺ and \( \bar v_\mu p \to \mu ^ + p\pi ^ - \) in the Δ(1232) region are presented and a test of the PCAC hypothesis, using a modified version of the Adler model, is performed. The analysis is based on 1081 events in the neutrino and on 180 events in the antineutrino reaction, obtained in a bubble chamber experiment with BEBC at CERN. The experimental cross-sections for an invariant hadronic massW<1.4 GeV and an (anti-)neutrino energyE _v ^L >10 GeV are determined to be (0.628±0.059)·10^?38 cm² for the neutrino and (0.168±0.023)·10^?38 cm² for the antineutrino reaction. TheQ ² andW distributions, the density matrix elements of the Δ resonance, and moments of the pion angular distribution are discussed. The data are found to be in good agreement with the Adler model in theQ ² region below 1 GeV². A maximum likelihood fit for the axial massm _A in the axial-vector form factor yields a value ofm _A =1.31±0.12 GeV. At lowQ ² the data confirm the PCAC hypothesis and the discrepancy, formerly observed between the experimental and theoretical cross-sections forv _μ p→ μ^? pπ⁺ at low momentum transfers (Q ²?0.2 GeV²), is understood as being due to inadequate pion ‘off-mass-shell’ corrections.     

Dispersive analysis of low energyγN→πN process and studies on the N^*(890)resonance

We present a dispersive representation of the γN→πN partial-wave amplitude based on unitarity and analyticity.In this representation,the right-hand-cut contribution responsible for πN final-state-interaction effects is taken into account via an Omnes formalism with elastic πN phase shifts as inputs,while the left-hand-cut contribution is estimated by invoking chiral perturbation theory.Numerical fits are performed to pin down the involved subtraction constants.Good fit quality can be achieved with only one free parameter,and the experimental data regarding the multipole amplitude E0+ in the energy region below the △(1232) are well described.Furthermore,we extend the γN →μN partial-wave amplitude to the second Riemann sheet to extract the couplings of the N*(890).The modulus of the residue of the multipole amplitude E0+(S11pE) is 2.41 mfm·GeV2,and the partial width of N*(890)→ yN at the pole is approximately 0.369 MeV,which is almost the same as that of the N*(1535) resonance,indicating that N*(890) strongly couples to the πN system.     

Dispersive analysis of low energy yN→nN process and studies on the N*(890)resonance

We present a dispersive representation of the yN → nN partial-wave amplitude based on unitarity and analyticity.In this representation,the right-hand-cut contri...