Roy Weinstein

Design, construction, prototype tests and performance of a vertex chamber for the MAC detector☆

Abstract The design considerations, construction techniques, prototype tests and performance characteristics of a pressurized drift chamber used in the MAC detector at PEP are described. The chamber consists of 324 aluminized mylar tubes of 6.9 mm diameter with wall thickness of 100 μm. With appropriate shielding it operates successfully at 4.6 cm from the beam line. It was simple to construct and was configured to permit any malfunctioning tubes to be remotely disconnected without affecting operation. The chamber operated without problems for two years in the PEP environment with a gas mixture of 49.5% argon, 49.5% CO 2 , 1% CH 4 , at 4 atm absolute pressure. The mean spatial resolution averaged over all tubes was 45 μm. The time to distance relation for this gas mixture, along with the geometric positioning of individual wires relative to the central tracking chamber, was obtained with data from Bhabha scattering events. We also describe resolution studies performed with a prototype chamber in a SLAC test beam. A wide range of gases, gas pressures, and electronic parameters were explored. These studies proved that resolutions in the 10–50 μm range were possible. Our experience demonstrates that chambers of this type provide high precision tracking and are particularly suited for operation in regions with difficult physical access and/or high ambient radiation levels.

Additional evidence for B0B̄0 mixing

Abstract The rate of like-charge dimuons has been measured with the MAC detector in hardonic events produced in e + e − annihilation at √ s =29 GeV. If the observed excess is attributed to B 0 B 0 mixing, the corresponding value of the mixing parameter χ = Γ (B→ μ − X)/ Γ (B→ μ ± X) is χ =0.21 +0.29 −0.15 and χ >0.02 at 90% CL.

Measurements of tau decays to three pions

Abstract We reports the result of a study of a tau decays with three pions in the final state (τ±→π±π+π−υτ and τ ±→π±π0π0υτ) from data accumulated with the MAC detector operating at the PEP storage ring. The branching fractions for these modes are measured to be 0.070±0.003±0.007 and, with assumptions discussed in the text, 0.087±0.004±0.011, respectively. Assuming that these final states result from the decay of the a1 meson, we measure the resonant parameters of the a1 with the three charged pion sample to be ma1=1166±18±11 MeV and γa1=405±75±25 MeV, and with the one charged plus two neutral pions sample to be ma1=1164±41±23 MeV and γa1=419±108±57 MeV.

A measurement of the e+e−→bb forward-backward charge asymmetry at √s=29 GeV☆

Abstract High p ⊥ inclusive muon events produced in e + e − annihilations at √ s =29 GeV have been analyzed to obtain a measurement of the b b forward-backward charge asymmetry. The result A b =0.034±0.070±0.035 differs from the theoretical expectation (−0.16) unless substantial B 0  B 0 mixing is assumed.

Hodoscope instrumentation for photoproduction of wide angle MU meson pairs: Part 1. Detectors and hodoscope electronics

Abstract A 192 counter hodoscope was used in an experiment on photoproduction of mu meson pairs utilizing a 5.2 GeV breamsstrahlung beam at the Cambridge Electron Accelerator. The hodoscope detectors are described. The logic and circuitry up to and including intermediate storage of hodoscope detector information on flip-flops is discussed. Reliability data, production techniques and costs are reported.

ϱ, ω photoproduction phase: A possible breakdown in vector dominance

Abstract Using vector meson dominance with real (γ, V) coupling constants we calculate the relative (ϱ, ω) photoproduction phase in nuclei as a function of assumed nucleon phases. Recent measurements of this phase are too large to be accommodated by these assumptions.

Industiral internship option in a Ph.D. program

A Ph.D. option with a one‐year Industrial Internship is being introduced to the Physics graduate program at Northeastern University. Except for the period of internship, the program requires that all usual course work and thesis research be done at the University. Selection criteria, which the students and the companies involved must meet, are reviewed. Although the program is new in the physics Department, the Northeastern University Chemistry Department has, for four years, run a program differing from this one only in details. Anecdotal evidence is presented from the Chemistry program.

Dimuon production by protons in Tungsten

The mass spectrum of dimuons produced by 400 GeV/c protons in Tungsten has been measured for masses greater than 7 GeV. A clear resonant signal of 2700 upsilons has been seen. The dependence of dimuon production on xF and pT has been determined for dimuon masses in the range 7.0 to 8.25 GeV as well as for masses in the upsilon region 8.25 to 9.75 GeV.

Measurements of Missing Mass (MM) Spectra from π−p ⇒ (MM)−p at 8, 11, 13.5, and 16 GeV

Measurements of missing mass (MM) spectra from π − p ⇒ ( MM ) − p at 8, 11, 13.5, and 16 GeV are reported. The MM mass range examined is 0 ≤ M 2 ≤ 7.3 GeV 2 with t (the proton four momentum transfer squared) in the interval 0.2 ≤ ∣ t ∣ ≤ 0.3 GeV 2 . Narrow resonances (R1, R2, R3, S, T, and U) with cross sections and widths reported by the CERN missing mass group are ruled out by the data. The cross sections d 2 σ/ dtdM 2 show evidence for triple factorizability of the form d 2 σ dtdM 2 ≃ D ( P B ) A ( M 2 ) G ( P ⊥ 2 ) where P B is the incident beam momentum,and P ⊥ 2 is the perpendicular component of the detected protons momentum with respect to the beam direction.

Missing-mass search for negative-charge bosons with masses between 2 and 12. 5 GeV

A missing-mass search has been made for negatively charged boson resonances B/sup -/ produced in the reaction ..pi../sup -/p ..-->.. B/sup -/p at beam momenta of 40, 100, 200, and 240 GeV. Approximately 600 000 events were included in the final mass spectra. In the mass region 2 < or = M/sub B/ < or = 12.5 GeV no statistically significant enhancements were observed. The 5-standard-deviation upper limit on the production of narrow resonances is of the order of 10 ..mu..b for 2 < or = M/sub B/ < or = 10.5 GeV.