Samuel C.C. Ting

An antimatter spectrometer in space

Abstract We discuss a simple magnetic spectrometer to be installed on a satellite or space station. The purpose of this spectrometer is to search for primordial antimatter to the level of antimatter/matter ≈10 −9 , improving the existing limits obtained with balloon flights by a factor of 10 4 to 10 5 . The design of the spectrometer is based on an iron-free, NdFeB permanent magnet, scintillation counters, drift tubes, and silicon or time projection chambers. Different design options are discussed. Typically, the spectrometer has a weight of about 2 tons and an acceptance of about 1.0 m 2 sr. The availability of the new NdFeB material makes it possible for the first time to put a magnet into space economically and reliably.

Experimental Study of Inclusive Muon Spectra at PETRA

The results of a high-statistics study of inclusive muon spectra at PETRA are reported. Improved mass limits have been obtained for heavy quarks, heavy leptons, and charged Higgs particles. It is shown that the fragmentation properties of b quarks and c quarks are different, with the mean fragmentation variables = 0.75 +- 0.03 +- 0.06, = 0.46 +- 0.02 +- 0.05 and the average semileptonic branching ratio for the B and C hadrons BR(B) = (10.5 +- 1.5 +- 1.3)%, BR(C) = (11.5 +- 1.0 +- 1.7)%.

Tests of quantum chromodynamics and a direct measurement of the strong coupling constant αs at √s=30 GeV

Abstract We report the measurement of the reaction e+ + e− → hadronic jets at a center-of-mass energy √s=30 GeV using the MARK-J detector at PETRA. By measuring the energy and angular distribution of both neutrals and charged particles we were able to isolate unambiguously the three-jet events in a kinematic region where the backgrounds from q q and phase space contributions and other processes are small. Various comparisons of the data with quantum chromodynamics were made. The relative yield of three-jet events and the shape distribution of the events enable us to determine αs = 0.23 ± 0.02 (statistical error) with a systematic error of ± 0.04.

PHOTOPRODUCTION OF NEUTRAL RHO MESONS.

We present results of measurements on photoproduction of ϱo mesons. Analysis of 105 measured π-pairs on protons in the energy region 2.6 − 6.8 GeV using various assumptions of rho production. indicates that dσ/dt(t = 0) decreases with increasing energy similar to πN scattering. Analysis of 106 measured π-pairs from 13 complex nuclei in a four-dimensional data matrix dσ/dΩdm(A.m.p.t⊥) with dimensions 13.20.6 and 20. yields precise information on nuclear density distributions determined by ϱ-production. We obtain for the Woods-Saxon radii R(A) = (1.12 ± 0.02) A13 fm. and using the vector-dominance model, σϱN = 26.7 ± 2.0 mb and γϱ2/4π = 0.57 ± 0.10.

The performance of a uranium gas sampling calorimeter

Abstract The performance of a uranium gas sampling hadron calorimeter is described. It has been observed that the hydrogen content of the gas mixture plays an important role in defining the behaviour of this type of calorimeter. The low-energy neutrons emerging from a hadron cascade are detected much more efficiently in a hydrogenous gas; thus leakage or containment of these neutrons becomes an important feature of the calorimeter setup.

Search for Charged Higgs, Scalar Taus, and a Test of Technicolor Models

Abstract We have used our measurements of final states from e+e− containing an isolated muon and a hadronic or electron shower to search for new spin 0 charged particles. We exclude (95% CL) a supersymmetric partner of the τ with a mass less than 14 GeV/c2. We obtain upper limits on the branching ratio to τvτ for charged Higgs particles or technipions with masses up to 14 GeV/c2. This disagrees with some technicolor model predictions.

Precision muon detectors in the Tev region

Abstract We present a design study, based on our experience in the construction of the L3 detector at LEP, of a large solid angle muon detector for a high luminosity (> 10 33 cm −2 /sec) pp collider. It is shown that a resolution of ΔM / M ∼ 1% can be reached for a one TeV particle T→ μ + μ − . Hadron jets can also be measured.

A time expansion chamber as a vertex detector for the experiment mark j at desy

Abstract The design and results from a beam test for a small vertex detector, now installed in the DESY MARK J experiment, are presented. The concept of this drift chamber is based on the time expansion principle with readout planes inclined to solve the left-right ambiguity. A spatial resolution of 35 μm, varying weakly as a function of drift length and azimuthal angle, has been achieved.

UNIQUE SOLUTION FOR THE WEAK NEUTRAL CURRENT COUPLING-CONSTANTS IN PURELY LEPTONIC INTERACTIONS

Abstract By combining results from the MARK-J at PETRA on Bhabha scattering, μ + μ - and τ + τ - production with recent world data from neutrino-electron scattering experiments, we determine unique values for the leptonic weak neutral current coupling constants g V and g A in the framework of electroweak models containing a single Z 0 . In contrast to previous analyses, we only use data from purely leptonic interactions, and therefore avoid the inherent uncertainties resulting from the use of hadronic targets. From the MARK-J data alone in the context of the standard SU(2) ⊗ U (1) model of Glashow, Weinberg and Salam, we find sin 2 θ W =0.24±0.11.

The superconducting magnet of AMS-02

Abstract The Alpha Magnetic Spectrometer (AMS) is a particle physics detector designed to search for anti-matter, dark matter and the origin of cosmic rays in space. The detector will be installed on the International Space Station (ISS). The planned duration of the experiment is 3 years. The magnetic dipole field is achieved by an arrangement of 14 superconducting coils. The magnet system consists of a pair of large Helmholtz coils together with two series of six racetrack coils, circumferentially distributed between them. This arrangement was mainly chosen to minimize the stray field outside of the magnet. It generates a magnetic field of 0.87 T in the center of the magnet with a bending power of 0.78 Tm2. All superconducting coils are indirectly cooled by pressurized superfluid helium at 1.8 K. This cooling loop is thermally connected with a 2500 l vessel for superfluid helium which serves as a cold reservoir. In order to ensure the 3 year endurance without refilling, the magnet design was optimized with respect to very low heat losses. This paper describes the main features of the AMS superconducting magnet and the principle concept of the cryogenic system.