M MacDermott

A study of inclusive Λ, > Σ0 and Σ(1385) production in K−p interactions at 8.25 GeV/c

Abstract Inclusive Λ production has been studied in K−p interactions at 8.25 GeV/c using about 69 000 events; the total cross section is found to be 3.35 ± 0.20 mb. A comparison has been made with Σ0 and Σ(1385) inclusive production. Their influence on the inclusive Λ production is discussed. The inclusive Λ cross section and polarization is interpreted in terms of the triple-Regge model. In the target fragmentation region an effective Regge trajectory is determined which lies closer to the K than to the K∗. In the beam fragmentation region the cross-section data indicate an effective Regge trajectory which corresponds to the nucleon, while the polarization data require additional Regge exchanges to be present.

Observation of a narrow hyperon state of mass 3.17 GeV

Abstract We present evidence for a narrow Y∗ with a mass of 3.17 GeV and a width ⩽ 20 MeV decaying to ΣKK + pions, ΛKK + pions and ΞK + pions. The data come from two high statistics K−p bubble chamber experiments with a sensitivity of ≈100 eV/μb at 8.25 GeV/c and ≈ 45 eV/μb at 6.5 GeV/c.

A study of the lifetime and spin of Ω− produced in K−p interactions at 8.25 GeV/c

Abstract Using the decay mode Ω − → Λ K − , we have obtained a measurement of the Ω − lifetime τ Ω = (0.80 ± 0.12 0.16 ) × 10 −10 s . The Ω − decay angular distribution is consistent with W( cos θ ∗ ) ∝ 1 + 3 cos 2 θ ∗ . The probability of consistency with a flat distribution is ∼ 1 300 indicating J ≠ 1 2 .

A study of the reactions K−p → Λπ0, Λη, Λη at 8.25 GeV/c incident K− momentum

Abstract Differential cross sections and polarizations are presented for the reactions K − p → Λπ 0 , Λη , Λη ′ at 8.25 GeV/ c incident K − momentum. The data, which come from a high statistics experiment in the CERN 2 m bubble chamber, are compared with previous experimental results on the same reactions and with current theoretical ideas.

Observation of a KK enhancement at 1.85 GeV in the reaction K−p → KKΛ at 8.25 GeV/c

Abstract In a high statistics ( ∼150 eV μb ) bubble chamber experiment on K − p interactions at 8.25 GeV c , the study of the reaction K − p → KK Λ provides evidence for an enhancement in the KK system with a mass of (1850 ± 10) MeV and a width of (80 −30 +40 ) MeV. Its possible identification with the missing isosinglet of the 3 − nonet is discussed. A K ∗ K decay mode is also observed.

Evidence for a Λp resonance with spin-parity 2−

A moments analysis of the Λp system produced forwards (t< 1 GeV2) by 8.25 GeV/c K− mesons in the reaction K−p → Λpp has been performed. Significant structure is observed in the double moments H(LMlm) describing the decay of the Λp system and the subsequent Λ decay for L ⩽ 4. This structure can be interpreted in terms of the production of a resonance of spin-parity JP = 2−, with a mass and width of 2235±50 MeV and ∼ 200 MeV, respectively. The production cross section for the Λp decay mode is ∼ 1.5 μb.

A study of inclusive Ξ−, Ξ(1530) and Ω− production in K−p interactions at 8.25 GeV/c

Inclusive Ξ− production is studied in K−p interactions at 8.25 GeV/c using about 8000 events. An analysis based on the triple-Regge model shows that the Λα − Λγ and Σβ − Σδ exchanges explain the forward Ξ− production. Ξ(1530) properties are also studied and are found to be similar to those of Ξ−s. Finally, a study of the production of Ω− based on 67 events shows that Ωs are also produced by hyperon exchange.

Off-shell KK and pp interactions in K−p → Λ + X at 8.25 GeV/c

Using the reaction K−p → Λ + X at 8.25 GeV/c we compare off-shell KK and pp interactions to on-shell pp interactions. The charged multiplicities are studied as functions of the off-shell c.m.s. energy √ s = Mx. Agreement is found between on- and off-shell pp reactions. It is shown that the charged multiplicities in KK interactions are lower than in pp. A KNO scaling is observed as a function of Mx2. The universal curve fitted by Slattery reproduces our data. Distinction has also been made between total inelastic and annihilation reactions.

Observation of a K∗ resonance at 2088 MeV

In a high statistics (180 events/μb) bubble chamber study of the reaction fxK−p→K0π−p at 8.25 GeVc, we observe a K0π− state at 2088±20 MeV with a width 170+100−50 MeV, produced with a cross section of 3.6±1.2μb. In addition we observe this state in the channels K∗(890)ππ, ϱKπ, ωKπ with a combined cross section of 7.1±2.6 μb, and possibly K∗(890)πππ.

A PARTIAL WAVE ANALYSIS OF THE K PI PI SYSTEM PRODUCED IN THE REACTION K- P ---> ANTI-K0 PI+ PI- N AT 8.25-GeV/c

CERN 2M HBC. PARTIAL WAVE ANALYSIS OF AK0 PI+ PI- SYSTEM USING A MODIFIED ILLINOIS PWA PROGRAM. IC FIT TO 2 PRONGS PLUS OBSERVED VEE0 DECAY. STRONG SIGNAL OBSERVED IN 1+S0(K*PI) WAVE AT THE Q2 MASS (APPROX 1.4 GEV). PROMINENT SIGNAL IN 2+D (K*PI AND RHOK) WAVE INTERPRETED AS K*(1430) PLUS EVIDENCE FOR 3-K*(1780). STRONG EVIDENCE IN 1-P0-(K*PI) WAVE AT AROUND 1.47 GEV WHICH DOES NOT SEEM TO BE DUE TO A RESONANCE.