R.K. Carnegie

Observation of new resonant structures in the natural spin-parity strange meson system

Abstract High statistics data for the reaction K−p→K−π+n have been obatined using the LASS spectrometer at SLAC. An energy independent partial wave analysis of these data yields unique K−π+ elastic scatering partila wave amplitudes in the Kπ invariant mass region from 0.7 GeV to 1.8 GeV, and two distinguishable sets of amplitudes between 1.8 GeV and 2.3 GeV. Besides the three “old” K∗ resonances [J P = 1 − K ∗ (892), 2 + K ∗ (1430), 3 − K ∗ (1780)] these partial waves display evidence for a K∗ resonance with JP=4+ near 2.07 GeV. The energy dependence of the S wave amplitude confirms the existence of a resonant 0+ state in the 1.4 GeV region [the k(1500)], and provides evidence for a new high-mass S wave resonance [′(1850)] near 1.85 GeV. Resonant behavior is also observed in the P wave amplitude around 1.7 GeV.

Partial wave analysis of the K°π+π− system produced in K−p interactions at 11 GeV/c☆

Abstract We have performed a partial wave analysis of the K °π + π − system produced in the reaction K − p → K °π + π − n at 11 GeV /c and detected in the LASS spectrometer at SLAC. Results from an analysis of ≈7600 events in the K °π + π − mass range from 1090 to 2290 MeV/c2 produced at low t(∥t′∥ The JP = 2+, 3− and 4+ amplitudes show the behavior expected of the leading K∗(1430), K∗(1780) and K∗(2060) respectively. The behavior of the JP = 1+ and 2− amplitudes can be associated with the Q2(1400) and the L(1770). The 1− amplitudes exhibit behavior which indicates the existence of two resonant states, one near 1400 MeV/c2 and the other near 1800 MeV/c2. A simple Breit-Wigner model is used to fit the leading partial wave amplitudes and to compute branching ratios for the K∗(1430) and the K∗(1780).

Observation of a spin-parity 4+ K∗(2090)

Abstract High statistics data for the reaction K − p → K − π + n at 11 GeV c have been obtained in the LASS spectrometer at SLAC. A spherical harmonic moment analysis of the Kπ angular distribution displays evidence for a new K ∗ state at 2086 MeV c 2 with the spin-parity assignment, J P = 4 + .

The OPAL vertex detector prototype

The prototype test results of a high resolution charged particle tracking detector are reported. The detector is designed to measure vertex topologies of particles produced in the e+e− collisions of the OPAL experiment at LEP. The OPAL vertex detector is a 1 m long, 0.46 m diameter cylindrical drift chamber consisting of an axial and stereo layer each of which is divided into 36 jet cells. A prototype chamber containing four axial and two stereo cells was studied using a pion test beam at CERN. The studies examined the prototype under a variety of operating conditions. An r−φ resolution of 60 μm was obtained when the chamber was operated with argon (50%)-ethane (50%) at 3.75 bar, and when CO2(80%)-isobutane (20%) at 2.5 bar was used a 25 μm resolution was achieved. A z measurement using end-to-end time difference has a resolution of 3.5 cm. The details of these prototype studies are discussed in this paper.

Observation of two non-leading strangeness-one vector mesons

Abstract We present evidence for the existence of two strange JP = 1− mesons; one at 1410 MeV/c2 coupling principally to K ∗ (892)π , and the other at 1790 MeV/c2 couplingto Kπ, K ∗ π and ϱK. The data derive from a partial wave analysis of the K 0 π + π − system produced in the reaction K − p → K 0 π + π − n at 11 GeV /c . The production mechanism and quark model assignment of each state are discussed. The state at 1410 MeV/c2 most naturally understood as the first radial excitation of the K∗(892), and the 1790 MeV/c2 object can be interpreted as the triplet D wave partner to the 3−K∗(1780).