R.J. Cashmore

Q1 (1290) and Q2 (1400) Decay Rates and their SU(3) Implications

Abstract We summarize and combine the known information on the decay rates of the strangeness-one axial vector mesons, Q 1 and Q 2 . From this information and the rate for B→ωπ, we determine the Q A −Q B mixing angle and the S -wave, symmetric and antisymmetric octet couplings for vector-pseudoscalar decays of axial vector mesons. If we assume the D(1285) and the E(1420) belong to the J PC =1 ++ nonet, we find the A 1 to have a mass of ∼1.47 GeV and a large (>0.3 GeV) width.

Analysis of K−K+ and π−π+ final states in 13 GeV K−p interactions☆

Abstract The differential cross sections and density matrix elements for the φ and ϱ0 mesons have been measured in the reactions K−p → K−K+ (Λ, Σ0) and K−p → π−π+ (Λ, Σ0) at 13 GeV using a wire chamber spectrometer. The analysis shows that while the vector meson production is dominated by the natural parity exchange amplitude, some unnatural parity exchange is also required. Furthermore the φ and ϱ natural exchange cross sections are identical in shape and have the 2:1 relative strength expected in the quark model with K∗ and K∗∗ exchange degeneracy. The analysis of the clear peak-dip ϱ0−ω interference pattern observed in the π−π+ data indicates that the ω production is in phase with the ϱ and of similar magnitude. Both the S∗ and f′ meson are clearly observed in this experiment. The S∗ data are found to be consistent with S∗ parameters deduced from ππ scattering analyses. The f′ density matrix elements and a new limit of the f′ → π−π+ branching ratio are presented.

A simple description of the JP = 1+K±π+π− system in the reactions K±p→K±π+π−p

A model in which Q1 and Q2 resonance contributions add coherently to a Gaussian background is shown to reproduce the mass dependence of the JP = 1+K∗π and ϱK partial waves in K±p→K±π+π− at 13 GeV/c. Through a fit to the data, the mass and total width for Q1 are found to be m = 1289 ± 3 ± (25) MeV, Λ = 150 ± 9 (±70) MeV and for Q2, m = 1404 ± 3 (±10) MeV, Λ = 142 ± 4 (±15) MeV, where estimated systematic errors are given in parentheses. While a significant background is required for the 1+K∗π system, none is needed for the 1+ϱK system.

Determination of the K∗(1800) spin parity

Abstract A spherical harmonic moment analysis of the reactions K − p → K − π + n and K + p → K + π − Δ ++ at 13 GeV/ c demonstrates the existence of a broad K ∗ state with mass in the vicinity of 1800 MeV and spin parity 3 − .

N* resonance parameters and K-matrix fits to the reactions πN→Δπ+ϱN+ɛN

Abstract From a partial wave analysis of the reaction πN→ππN we extract 50 cuoplings and partial widths for N * resonance decaying into Δπ, ϱN and eN. Three different methods of determining the resonance parameters are compared. The signs of the πΔ couplings are found to be consistent with the predictions of l-broken SU(6) w , if one assigns P′ 11 (1415), P″ 11 (1730) and P 33 (1700) to [56, L=0 + ] supermultiplets. The signs of the ϱN couplings are inconsistent with SU(6) w symmetry in its l-broken form, but in good agreement with the observed photon couplings.

Measurement of particle and antiparticle elastic scattering on protons between 6 and 14 GeV

Abstract Differential cross sections in the t -range between 0.02 and 1.5 GeV 2 have been measured for the elastic scattering of particles and antiparticles on protons at 6.4, 10.4 and 14 GeV for K ± p and 10.4 GeV for π ± p and p ± p . Large statistics have been achieved and systematic uncertainties have been minimized. The relative systematic uncertainty between particle and antiparticle data is less than 0.5%. Accurate measurements of the position of the first crossover between particle and antiparticle differential cross sections have been performed. As the energy increases from 6.4 to 14 GeV the K ± p crossover moves to smaller values by 0.010 GeV 2 with a statistical error of 0.006 GeV 2 and a systematic uncertainty of 0.005 GeV 2 . The crossover positions at 10.4 GeV for π ± , K ± and p ± scale approximately with the interaction radii.

Amplitudes and exchange mechanisms for K∗(890) and K∗(1420) production

Abstract The K ∗ (890) and K ∗ (1420) production amplitudes are determined using data on the reaction K − p → K − π + n at 13 GeV/ c . The energy dependence of K ∗ (890) production is investigated by using in addition the corresponding data at 4 GeV/ c . A simple model, based on exchange degenerate Regge poles together with non-evasive ‘cut’ contributions is found to provide a good description of all features of the data.

A partial wave analysis of πN → ππN at center-of-mass energies below 2000 MeV

Abstract We present the results of a partial wave analysis of πN → ππN in the energy region 1300–2000 MeV. Two continuous solutions have been found, in which all the major resonances are observed in the inelastic channels. The existence of P 13 (1700) and P 11 (1700) states are confirmed, and evidence for a new resonance, D 13 (1700), is presented. Further, our best solution (“B”) indicates the presence of resonant structure in the 1700–1900 MeV region for the P 33 wave. Finally, analysis of data on π + p → π + pπ 0 at 1610 MeV demonstrates that this solution (“B”) is the best description of inelastic πN scattering at these energies.

Study of K−p→K∗(890)n at 13 GeV

The results of a wire chamber spectrometer experiment studying K∗ (890) production in the reaction K−p→ K−π+n at 13 GeV are presented. Strong forward structure is observed for |t|< m2π in the s-channel density matrix elements and differential cross section. These features are similar to those observed in π−p→ϱ0n data and are characteristics of π exchange. In contrast in the intermediate, |t| ∼ 0.2 GeV2, and large momentum transfer regions K∗ (890) production is demonstrated by the natural parity ϱ−A2 exchange contribution.

The structure of the forward elastic cross section in (10–14) GeV range☆

Abstract The logarithmic slope of the differentical cross section for K ± p elastic scattering at 10 and 14 GeV, and for π ± p and p ± p at 10GeV has been measured. Rich structure is observed in the forward slope for all processes, which is well accounted for by the properties of a peripheral exchange amplitude for the nonexotic reactions, and by a peripheral component of the diffractive amplitude as clearly seen in the exotic processes, K ± p and pp.