N. M. Cason

Description and performance of the Fermilab E687 spectrometer

Abstract The magnetic spectrometer and charged particle tracking system used in Fermilab experiment 687 to study the photoproduction and decay of charm particles are described in detail. The photons are produced by a wideband electron beam which can operate at energies up to 600 GeV/ c . The spectrometer consists of a high resolution silicon microstrip detector, a large aperture dipole magnet, proportional chambers, a second large aperture dipole, and more proportional chambers. Three multi-cell threshold Cherenkov counters provide charged particle identification. The tracking system is capable of resolving the secondary decay vertices of charm and beauty mesons and baryons from the primary interaction vertex. It also determines the invariant mass of the multibody final states of particles containing heavy quarks with excellent resolution. The particle identification system allows one to identify kaons and protons present in these final states clearly. This collection of detectors produces very clean signals for charm particles and permits one to make many cross checks of the apparatus. The performance is illustrated for a variety of charm signals. Of particular interest is a description of the tracking through the silicon microstrip detector and its use in isolating downstream decay vertices. Two complementary approaches to the reconstruction of secondary decay vertices are presented and insight is gained by comparing their strengths and weaknesses.

Evidence for exotic meson production in the reaction pi- p ---> eta pi- p at 18-GeV/c

The {eta}{pi}{sup {minus}} system has been studied in the reaction {pi}{sup {minus}}p{r_arrow}{eta}{pi}{sup {minus}}p at 18 GeV/c. A large asymmetry in the angular distribution is observed indicating interference between L-even and L-odd partial waves. The a{sub 2}(1320) is observed in the J{sup PC}=2{sup ++} wave, as is a broad enhancement between 1.2 and 1.6 GeV/c{sup 2} in the 1{sup {minus}+} wave. The observed phase difference between these waves shows that there is phase motion in addition to that due to a{sub 2}(1320) decay. The data can be fitted by interference between the a{sub 2}(1320) and an exotic 1{sup {minus}+} resonance with M=(1370{plus_minus}16{sup +50}{sub {minus}30}) MeV/c{sup 2} and {Gamma}=(385{plus_minus}40 {sup +65}{sub {minus}105}) MeV/c{sup 2} . {copyright} {ital 1997} {ital The American Physical Society}The

Evidence for exotic J(PC) = 1-+ meson production in the reaction pi- p ---> eta pi- p at 18-GeV/c

\eta \pi^{-}

Exotic meson decay to ωπ0π

system has been studied in the reaction

Analysis of three D → Kππ Dalitz plots

\pi^{-} p \to \eta \pi^{-} p

Partial wave analysis of the pi(0) pi(0) system produced in pi(-)p charge exchange collisions

at 18 GeV/c. A large asymmetry in the angular distribution is observed indicating interference between L-even and L-odd partial waves. The

Analysis of the decay mode D+ → K∗0μ+ν

a_{2}(1320)

First evidence of

is observed in the

Analysis of the D+, Ds + → K+K-π+ Dalitz plots

J^{PC}

Analysis of the decay mode D+ ---> anti-K*0 mu+ neutrino

=