W. Männer

ππ Phase‐Shift Analysis from 600 to 1900 MeV

Wa have performed an energy‐dependent and an energy‐independent analysis of elastic ππ scattering, using data for the reaction π−p ⇒ π−π+n at 17.2 GeV/c. The ππ energy covers the range from 600 MeV to 1900 MeV. Apart from the well‐known resonances ρ, f and g, we find a strong S‐wave in the ρ and also in the f‐meson region. A P‐wave resonance occurs in both analyses at ∼ 1600 MeV with a total width of 180 MeV and an elasticity of 0.25, which can be identified with the ρ′ meson in its ππ decay mode. The zeros in the complex cos Θ plane of the scattering amplitude are studied as a function of the energy. The position of the real parts of the zeros are in qualitative agreement with the prediction of the Veneziano model. Furthermore, we show that an analogous relation holds also for the imaginary parts of the zero trajectories.

High statistics study of the reaction π−p→π−π+n: Apparatus, method of analysis, and general features of results at 17 GeV/c

Abstract A detailed account is given of a high statistics experiment measuring the reaction π−p→π−π+n at 17.2 GeV/c. The spark chamber and counter triggering system are desribed. The methods of data analysis are described, in particular the determination of angular distributions from apparatus with limited acceptance. Experimental data and their interpretation are presented.

Measurement and analysis of the π+π+ system produced at small momentum transfer in the reaction π+p→π+π+n at 12.5 GeV

Abstract From a wire chamber experiment 45 452 events were obtained from the reaction π + p→ π + π + n. The I =2 phase shifts were determined in the π + π + mass region 0.3–1.5 GeV. An amplitude analysis was performed. The results are compared with some theoretical predictions.

A study of the ππ phase-shift solutions in the mass region 1.0 to 1.8 GeV from π−p → π−π+n at 17.2 GeV

Abstract The ππ phase shifts from 1 to 1.8 GeV are presented. The method used was an essentially energy-independent parametrization of the amplitudes fitted simultaneously to the M ππ and t -dependence of the moments of the dipion angular distribution from the reaction π − p → π − π + n at 17.2 GeV. The various ambiguous solutions are discussed.

Diffractive Production of Strange Mesons at 63-{GeV}

Abstract Nearly 200 000 examples of the diffractive process K − p → K − π − π + p at 63 GeV have been obtained using a two magnet spectrometer equipped with Cerenkov counters for secondary particle identification. In addition some 2000 examples of the process K − p → ω K − p have been obtained. The K ππ data have been subjected to partial-wave analysis. The dominant J P = 1 + system couples to K ∗ π , in both S and D waves, ϱ K, κπ and e K. The data confirm the existence of two J P = 1 + Q mesons and their masses, widths and branching ratios are given. The ifωK data show that the couplings of the Q mesons to ω K are approximately equal to the couplings to ϱ 0 K. The two 1 + nonets expected in the quark model are discussed in the light of this and other recent experiments. There is strong evidence for a broad J P = 0 − resonance at about 1.46 GeV. At higher masses, structure in the J P = 2 − partial waves establishes the existence of at least one J P = 2 − L meson.

Diffractive production of 3π states at 63 and 94 GeV

Diffractive production of the 3π system has been studied at 63 and 94 GeV using a two magnet spectrometer with high, uniform acceptance. The total number of events used in the analysis is ∼600 000. The A2 meson is shown to be diffractively produced. The existence of a resonant component in both the 1+ and 2− enhancements is established and resonance parameters for the corresponding A1 and A3 mesons are given. There are several indications in the data of states which would correspond to radial excitations in the quark model.

A model-independent partial-wave analysis of the π+π− system produced at low four-momentum transfer in the reaction π−p ↑ → π+π−n at 17.2 GeV/c

Abstract The π + π − partial waves are studied up to the F-wave in the mass region from 580 to 1780 MeV/ c 2 at low four-momentum transfer. The study is based on a previous hydrogen target experiment and a more recent polarized target experiment. Using the results of both experiments for 0.01 ⩽ | t | ⩽ 0.20 GeV 2 / c 2 , a partial-wave analysis is performed in each mass bin ( Δm = 40 MeV/ c 2 ) independently. For the first time a model-independent analysis has been possible, which enables us to check the assumptions made in previous studies. In general we find a unique solution determining the exact intensity of each partial wave. The uniqueness of our solution is related to the Barrelet zeros being real in the mass region where their imaginary part were supposed to produce ambiguities. We observe a non-π exchange contribution even in the helicity m = 0 amplitudes.

Isospin-two ππ phase shifts from an experiment π+p→π+n at 12.5 GeV/c

The I = 2 s‐ and d‐wave ππ phase shifts δs2 and δd2 have been determined in the ππ mass region from 500–1500 MeV, using a sample of 17,500 events π+p ⇒ π+π+ from a spark chamber experiment. For this purpose the moments of the ππ angular distribution in the s‐channel helicity frame have veen written as bilinear expressions of OPE amplitudes modified by absorption and have been fitted to the measured values of the moments in four mass bins of width 0.25 GeV/c2. The value of δs2 in the ρ‐mass region (δs2 ≃ −15.5°) corresponds to an elastic cross‐section of ≃ 7.5mb.The values of δd2 are about a factor of 10 smaller than the corresponding values of δs2 for the whole mass region considered.

Measurement of the mass and width of the charmed meson D∗+ (2010)

Abstract Using a high-resolution silicon vertex detector we have observed a very clean signal of 127 D∗+. After a careful study of the experimental resolution of our apparatus we have measured m( D ∗++ )−m( D 0 ) = 145.39±0.06±0.03 MeV . We have also obtained a 90% CL upper limit to γ(D∗+) of 131 keV.

Inclusive φ-meson production in 93 and 63 GeV hadron interactions

Abstract The inclusive reactions h+p→φ+X, (h=π±,,K±,p±), are studied for 0⪅xF⪅0.3 and p⊥ ⩽ 1 GeV at 93 and and 63 GeV incident momentum. Differential cross sections dσ/dp⊥2 anddσ/dxF are presented and are compared with predictions of the naive parton model.