Evidence for a negative-parity spin-doublet of nucleon resonances at 1.88 GeV

Evidence is reported for two nucleon resonances with spin-parity J^P=1/2⁻$J^P=1/2^{-}$ and J^P=3/2⁻$J^P=3/2^{-}$ at a mass just below 1.9 GeV. The evidence is derived from a coupled-channel analysis of a large number of pion and photo-produced reactions. The two resonances are nearly degenerate in mass with two resonances of the same spin but positive parity. Such parity doublets are predicted in models claiming restoration of chiral symmetry in high-mass excitations of the nucleon. Further examples of spin parity doublets are found in addition. Alternatively, the spin doublet can be interpreted as member of the 56-plet expected in the third excitation band of the nucleon. Implications for the problem of the missing resonances are discussed.     

Two-pion spectra for the reaction π− p → π0π0 n at a pion momentum of 38 GeV/c and combined analysis of GAMS, Crystal Barrel, and BNL data

We perform a K-matrix analysis of IJ ^PC =00⁺⁺, 10⁺⁺, 02⁺⁺, and 12⁺⁺ meson partial waves using GAMS data on π^? p → π⁰π⁰ n, ηηn, ηη'n that are supplemented with BNL data on π^? p → K $\bar K$ n and Crystal Barrel data on p $\bar p$ (at rest) → π⁰π⁰π⁰, π⁰ηη, π⁰π⁰η. The positions of the amplitude poles (physical resonances) are determined, together with the positions of the K-matrix poles (bare states) and the values of barestate couplings to two-meson channels. The nonet classification of the bare states found in the present analysis is discussed.     

Bonn-Gatchina partial wave analysis

The present status of the Bonn-Gatchina partial wave analysis of the photoproduction and pion induced data is presented. An observation of signals which can be associated with new baryon resonances and possible interpretations of the baryon spectrum is discussed.     

Problem of the complete measurement forCP-violating parameters in neutralB-meson decays

PhenomenologicalCP-violating parameters in decays of neutralB-mesons are discussed. Special attention is given to the degree of their measurability. We emphasize important role of the sign ofΔm _B and suggest how it could be determined experimentally.     

The study of the proton-proton collisions at the beam momentum 1628 MeV/c

The detailed investigation of the single pion production reactions pp → pnπ and pp → ppπ at the incident proton momentum 1628 MeV/c has been carried out. The data are analyzed in the framework of the event-by-event maximum-likelihood method together with the pp → ppπ ⁰ data measured earlier in the energy region below 1 GeV. At 1628 MeV/c the largest contributions stem from the ³ P ₂, ³ P ₁, ³ P ₀, ¹ D ₂ and ³ F ₂ initial partial waves.     

Deuteron Breakup Induced by 778-MeV Protons

Physics of Atomic Nuclei - An experiment devoted to studying deuteron breakup induced by 778 MeV protons was performed with the aid of a deuterium bubble chamber. Experimental spectra are compared...     

Further study of D+ s decays into π-π+π+

A Dalitz plot analysis of the OZI rule violating decay D⁺ _s into π^-π⁺π⁺ is presented using different partial wave approaches. Scalar and vector waves are described by K-matrices; their production is parameterized in a P-vector approach. Alternatively, Breit–Wigner amplitudes and Flatté parametrization are used. Special emphasis is devoted to scalar mesons. The f₀(980) resonance provides the most significant contribution. Adding f₀(1500) to the scalar wave leads to an acceptable fit while introduction of f₀(1370) and/or f₀(1710) does not lead to significant improvements. A scan of the scalar wave optimizes for M=1452 ± 22 MeV/c ². When f₀(1710) is added, the mass uncertainty increases, and the fit yields M=1470 ± 60 MeV/c ² which is fully compatible with the nominal f₀(1500) mass. The scalar wave seems to exhibit a phase motion of 270° units in the mass range from 1200 to 1650 MeV/c ². PACS 11.80.Et; 13.20.Fc; 14.40.Cs     

Photoproduction of η -mesons off protons

Photoproduction of η -mesons was studied with the Crystal-Barrel detector at ELSA for photon energies in the range from 0.75 to 3GeV. Total and differential cross-sections are presented. The η mesons are detected in two decay modes, in η → 2γ and in η → 3π⁰ → 6γ . The cross-sections vary slowly as functions of energy and η production angle suggesting that only few resonances make significant contributions to the cross-section. For photon energies above 1.5GeV, the differential cross-sections show a strong forward peak due to meson exchanges in the t channel. A comparison of the η -photoproduction cross-sections with SAID and MAID as well as with a partial-wave analysis performed on our data in combination with other data sets shows good agreement. The Bonn-Gatchina partial-wave analysis suggests that the largest contribution to η photoproduction for energies below 3GeV proceeds via three resonances, the well-known N(1535)S ₁₁ , via N(1720)P ₁₃ , and a newly suggested N(2070)D ₁₅ .     

Photoproduction of pions and properties of baryon resonances from a Bonn-Gatchina partial-wave analysis

Masses, widths and photocouplings of baryon resonances are determined in a coupled-channel partial-wave analysis of a large variety of data. The Bonn-Gatchina partial-wave formalism is extended to include a decomposition of t and u exchange amplitudes into individual partial waves. The multipole transition amplitudes for $ \gamma$ p $ \rightarrow$ p $ \pi^{0}_{}$ and $ \gamma$ p $ \rightarrow$ n $ \pi^{+}_{}$ are given and compared to results from other analyses.