P.L. Frabetti

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.

Analysis of three D → Kππ Dalitz plots

Abstract Analysis of three D → Kππ Dalitz plots is presented using data collected by the Fermilab high energy photoproduction experiment E687. Our data are fit to a model consisting of a sum of Breit-Wigner amplitudes for the intermediate two-body resonant decay modes and a constant term for the nonresonant contribution. We extract branching fractions and relative phases and compare them to the results obtained in other experiments. Although this model qualitatively reproduces many features of our data, statistically significant discrepancies are observed in some of our fits.

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

Abstract Fermilab high-energy photoproduction experiment E687 provides a high statistics sample of the decay mode D + → K ∗0 μ + ν (charge conjugates are implied). Our analysis yields a branching ratio of Γ (D + → K ∗0 μ + ν) Γ (D + → K − π + π + ) = 0.56±0.04±0.06 . The ratios of the form factors governing the decay are measured to be R ν = 1.74 ±0.27±0.28 and R 2 = 0.78±0.18±0.10, implying a polarization of Γ l Γ t = 1.20±0.13 ±0.13 for the electron decay. Finally, we report new limits on the decay modes D + → K − π + μ + ν (nonresonent) and D + → K ∗0 π 0 μ + ν .

First evidence of

Abstract We report evidence of a narrow resonance at a mass of 2705.9 ± 3.3 ± 2.0 MeV/c2 in the final state Ω−π+ and the charge conjugate. The mass and width support the interpretation of a weakly decaying doubly strange charmed baryon, the Ω c 0 . Limits on the relative branching ratios for Ω c 0 →Ω − K − π + π + and Ω c 0 →Ω − π − π + π + are also presented.

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

Abstract Amplitude analyses of the D + and D s + → K + K − π + Dalitz plots are presented using data collected by the Fermilab high energy photoproduction experiment E687. Our data are fit to a model consisting of a sum of Breit-Wigner amplitudes for the intermediate two-body resonant decay modes. We extract decay fractions and relative phases. These results are used to infer new branching ratios for D + → K + K − π + inclusive as well as the Φπ + and K ∗ (892) 0 K + channels.

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

Abstract Fermilab high-energy photoproduction experiment E687 provides a high statistics sample of the decay mode D + → K ∗0 μ + ν (charge conjugates are implied). Our analysis yields a branching ratio of Γ (D + → K ∗0 μ + ν) Γ (D + → K − π + π + ) = 0.56±0.04±0.06 . The ratios of the form factors governing the decay are measured to be R ν = 1.74 ±0.27±0.28 and R 2 = 0.78±0.18±0.10, implying a polarization of Γ l Γ t = 1.20±0.13 ±0.13 for the electron decay. Finally, we report new limits on the decay modes D + → K − π + μ + ν (nonresonent) and D + → K ∗0 π 0 μ + ν .

A measurement of elastic J/ψ photoproduction cross section at Fermilab E687☆

Abstract Measurements of elastic photoproduction cross sections for the J / ψ meson from 100 GeV to 375 GeV are presented. The results indicate that the cross section increases slowly in this range. The shape of the energy dependence agrees well with the photon-gluon fusion model prediction.

First evidence of Ωc0→Ω−π+

Abstract We report evidence of a narrow resonance at a mass of 2705.9 ± 3.3 ± 2.0 MeV/c2 in the final state Ω−π+ and the charge conjugate. The mass and width support the interpretation of a weakly decaying doubly strange charmed baryon, the Ω c 0 . Limits on the relative branching ratios for Ω c 0 →Ω − K − π + π + and Ω c 0 →Ω − π − π + π + are also presented.

First measurement of the lifetime of the omega(c)0.

Abstract We present the first measurement of the lifetime of the Ω c 0 baryon. The data were collected in the Fermilab high energy photoproduction experiment E687. The measured lifetime is τ = 86−20+27(stat.) ± 28(syst.) fr. Thus the Ω c 0 has one of the shorter lifetimes among the weakly decaying singly charmed baryons.

Measurement of the lifetime of the Xi c0.

A measurement of the lifetime of the charmed strange baryon [Xi][sub [ital c]][sup 0] is presented. The data were accumulated by the Fermilab high energy photoproduction experiment E687. The measurement has been made using 42[plus minus]10 [Xi][sub [ital c]][sup 0][r arrow][Xi][sup [minus]][pi][sup +] decays. The lifetime of the [Xi][sub [ital c]][sup 0] is measured to be 0.101[sub [minus]0.017][sup +0.025][plus minus]0.005 ps and its mass is measured to be 2462.1[plus minus]3.1[plus minus]1.4 MeV/[ital c][sup 2].