P. Cornet

The reaction K+d → Kopp at 4.6 GeV/c

Abstract In an experiment with the CERN 2m deuterium bubble chamber the reaction K+d→Kopp (1) and the related reaction K+n→Kop (2) are studied at an incident momentum of 4.6 GeV/c. The cross section for the latter reaction is found to be slightly larger than the cross section for the reaction K − p → K o n at the same energy. The corresponding differential cross sections agree within the rather large uncertainties. The forward amplitude for reaction (2) is predominantly real. Moreover, the total and forward differential charge exchange cross section values are compatible with those predicted on the basis of an SU (3) sum rule. A comparison of the K±-charge exchange differential cross sections with the predictions of a Regge pole model is also presented.

Study of the pπ− system produced in the reaction K+n→K+π−p at 8.25 GeV/c and comparison with data at 4.6 and 12 GeV/c

Abstract The fragmentation of the neutron into pπ− induced by incident K+ of 8.25 GeV/c is studied using data from the CERN 2 m deuterium bubble chamber and compared with data at 4.6 and 12 GeV/c. The pπ− low-mass enhancement below 1.85 GeV is analyzed and the major part exhibits the properties expected for diffraction dissociation. The presence of resonances is discussed. The data are fairly well represented by a double Regge exchange model involving pion and pomeron exchanges. The violation of the s-channel and t-channel helicity conservation is observed and compared to the s-channel description of Humble.

Production of the Kππ system in K+n and K+p interactions at 4.6 GeV/c

Abstract In an experiment with the CERN 2 m deuterium bubble chamber, the ( K ππ) 0 + systems in the effective-mass range below 1.5 GeV are studied for the reactions (1) K+n → K+π+π−n (2) K+n → K+π−π0n (3) K+n → K0π+π−n (4) K+p → K+π+π−n at 4.6 GeV/c incident momentum. Gross-section values are presented and the general features of these reactions are described. In addition the (Kππ)+ production and decay properties are investigated for reactions (1) and (4), and the results compared with the corresponding results for charge-exchange production of the (Kππ)0 system for reactions (2) and (3).

K∗ production in K+n → KπN at 8.25 GeV/c

Abstract Reactions K+n → (Kπ)N have been studied using data from the CERN 2 m deuterium bubble chamber obtained with incident K+ of 8.25 GeV/c. There is an abundant production of K∗(892) and K∗(1420). The reaction and K∗ resonance production cross sections are presented. K∗ production and decay angular distributions are analyzed. Charge-exchange reactions are dominated by unnatural parity exchange and the non-charge-exchange reaction by natural parity exchange. The K∗0(892) data are in good agreement with the predictions of an OPE absorption model. A broad enhancement around 1850 MeV could be interpreted as a signal for the K∗0(1780).

The reaction K+d→K+π+π−d at 4.6 GeV/c

In an experiment with the CERN 2 metre bubble chamber, the reaction K+d→K+π+π−d has been studied at an incident K+ momentum of 4.6 GeV/c. The cross section is 250±30 μb. A strong K∗ (892) signal is seen and also a broad enhancement in the Q region (M(Kππ) < 1.5 GeV) with no evidence for narrow resonances in this mass interval. The production and decay properties of these objects are studied, and comparisons made with similar reactions on protons. The properties of the angular distributions of the Q decay are very similar to those found in the related reaction on a proton target. The spin-parity of the Q system is found to be predominantly 1+ although 2− cannot be excluded. The dπ mass distributions show an enhancement for mass values ∼2.2 GeV; however the marked asymmetry in the corresponding decay angular distribution argues against a resonance interpretation of this effect.

Backward production of K∗ (892) in the reactions K+N → KπN in hydrogen and deuterium for the incident momentum range 3–5 GeV/c

Abstract Data on backward production of K∗ (892) are presented for the reactions K+d→K+π−ppS(1), K+p→Koπ+p(2) and K+d→Koπ+npS(3) in the incident momentum range 3–5 GeV/c. For reaction (1) at 4.6 GeV/c backward production of K∗ (1420) is also observed. The cross sections for backward K∗ (892) production in reactions (1) and (2) are found to be the same within error, and to exhibit a if(plab−n) energy dependence with n = 3.2 ± 0.5. Production and decay distributions are investigated, and SU(3) comparisons made with other reactions involving backward meson production.

Simultaneous production of K∗o (892) and Δ++(1236) in the reaction K+p→K+π+π−p from 4.3 to 5.0 GeV/c

Abstract The reaction K + d → K ∗o (892) Δ ++ (1236) n s from a K+d experiment with the CERN 2 m bubble chamber at 4.6 GeV/c is compared with the reaction K + p → K ∗o (892)Δ ++ (1236) from a K+p experiment at the same energy. In addition, predictions of an absorption model, a Regge pole model and a quark model for the production and decay characteristics of the reaction K + p → K ∗o (892)Δ ++ (1236) are tested with the combined statistics of the K+d experiment and three K+p experiments between 4.3 and 5.0 GeV/c.

Spin-parity analysis of the K+π− system produced in K+n → K+π−p at 4.6, 8.25 and 12 GeV/c

SummaryA spin-parity analysis of the K+π− system produced by charge exchange in the reaction K+n → K+π−p is performed with data at 4.6, 8.25 and 12 GeV/c forM(K+π−) < 1.6 GeV. The unnaturalparity exchange contribution dominates fort′ < 0.3 (GeV)2. Outside the K*(892) and K*(1420) regions there is little contribution from theJp = 1− andJp = 2+ states, respectively. TheS-waveJp= 0+ represents the major contribution forM(Kπ) < 1.6 GeV. It appears as a broad and smooth bump centred around 1250 MeV, but some structure may be present around 1350 MeV at 8.25 and 12 GeV/c. There is no evidence for a structure in thisS-wave under the K*(892).RiassuntoSi effettua un’analisi dello spin-parità del sistema K+π− prodotto dallo scambio di carica nella reazione K+n → K+π−p con dati a 4.6, 8.25 e 12 GeV/c perM(K+π−) < 1.6 GeV. Il contributo dello scambio a parità non naturale domina pert′ < 0.3 (GeV)2. Al di fuori delle regioni di K*(892) e K*(1420) c’è un piccolo contributo rispettivamente da parte degli statiJp = 1− eJp = 2+. L’ondaS conJp = 0+ rappresenta il contributo maggiore perM(Kπ)<1.6 GeV. Appare come una protuberanza ampia e liscia centrata attorno a 1250 MeV, ma qualche struttura può essere presente attorno a 1350 MeV a 8.25 e 12 GeV/c. Non è stata messa in evidenza alcuna struttura in questa ondaS al di sotto di K*(892).РеэюмеПроводится аналиэ спина и четности для K+π− системы, обраэованной в реэультате переэарядки в реакции K+n → K+π−p при 4.6, 8.25 и 12 ГзВ/с дляM(К+π−)< 1.6 ГзВ. Вклад обмена с неестественной четностью доминирует дляt′< 0.3 (ГзВ)2. Вне областей K*(892) и K*(1420) имеется небольщой вклад состоянийJP= 1− иJP= 2+.S волнаJP= 0+ представляет основной вклад дляM(Kπ)<1.6 ГзВ. По-видимому, наряду с щироким и плавным пиком, расположенным около 1250 МзВ, может иметь место некоторая структура около 1350 МзВ при импульсах 8.25 и 12 ГзВ/с. Не обнаружено подтверждений для структуры в зтойS-волне ниже K*(892).

Partial Wave Analysis of the K+ pi- System Produced in K+ n --> K+ pi- p at 4.6-GeV/c, 8.25-GeV/c and 12-GeV/c

SummaryA spin-parity analysis of the K+π− system produced by charge exchange in the reaction K+n → K+π−p is performed with data at 4.6, 8.25 and 12 GeV/c forM(K+π−) < 1.6 GeV. The unnaturalparity exchange contribution dominates fort′ < 0.3 (GeV)2. Outside the K*(892) and K*(1420) regions there is little contribution from theJp = 1− andJp = 2+ states, respectively. TheS-waveJp= 0+ represents the major contribution forM(Kπ) < 1.6 GeV. It appears as a broad and smooth bump centred around 1250 MeV, but some structure may be present around 1350 MeV at 8.25 and 12 GeV/c. There is no evidence for a structure in thisS-wave under the K*(892).RiassuntoSi effettua un’analisi dello spin-parità del sistema K+π− prodotto dallo scambio di carica nella reazione K+n → K+π−p con dati a 4.6, 8.25 e 12 GeV/c perM(K+π−) < 1.6 GeV. Il contributo dello scambio a parità non naturale domina pert′ < 0.3 (GeV)2. Al di fuori delle regioni di K*(892) e K*(1420) c’è un piccolo contributo rispettivamente da parte degli statiJp = 1− eJp = 2+. L’ondaS conJp = 0+ rappresenta il contributo maggiore perM(Kπ)<1.6 GeV. Appare come una protuberanza ampia e liscia centrata attorno a 1250 MeV, ma qualche struttura può essere presente attorno a 1350 MeV a 8.25 e 12 GeV/c. Non è stata messa in evidenza alcuna struttura in questa ondaS al di sotto di K*(892).РеэюмеПроводится аналиэ спина и четности для K+π− системы, обраэованной в реэультате переэарядки в реакции K+n → K+π−p при 4.6, 8.25 и 12 ГзВ/с дляM(К+π−)< 1.6 ГзВ. Вклад обмена с неестественной четностью доминирует дляt′< 0.3 (ГзВ)2. Вне областей K*(892) и K*(1420) имеется небольщой вклад состоянийJP= 1− иJP= 2+.S волнаJP= 0+ представляет основной вклад дляM(Kπ)<1.6 ГзВ. По-видимому, наряду с щироким и плавным пиком, расположенным около 1250 МзВ, может иметь место некоторая структура около 1350 МзВ при импульсах 8.25 и 12 ГзВ/с. Не обнаружено подтверждений для структуры в зтойS-волне ниже K*(892).

A measurement of K* (1420) decay branching ratios

The decay branching ratios of K∗0 (1420) into K+π−, K0π+π− and K∗+(892) π− are measured in the charge exchange reaction K+d → K∗0 (1420) ppS using data from a K+d bubble chamber experiment at 4.6 GeV/c incident momentum. For the branching ratio (K∗(1420) → K∗(892)π)/(K∗(1420) → Kπ) a value of (0.54 ± 0.16) is obtained. The results are compared with previous measurements.