C.Y. Chien

Kπ scattering phase shifts determined from the reactions K+p→K+π−Δ++ and K+p→KoπoΔ++

Abstract We studied the Kπ scattering from threshold to mKπ = 1200 MeV using the Chew-Low extrapolation method in the reactions K + p → K o ← π o − Δ ++ . In addition to an analysis using only the data at 5.43 GeV/c incident momentum, we also present the results using the world data compiled from experiments with momenta from 3.0 to 12.7 GeV/c. The extrapolated cross section for the elastic K+π−→K+π− scattering exceeds the p-wave isospin - 1 2 unitary limit in the K∗ (890) region. The phase shift δ11 (notation δ l 2I ) shows the expected Breit-Wigner behavior which suggests that δ 1 3 ⋍0 in the mass region studied. Solutions for the s-wave phase shifts δo1 and δo3 are obtained from the extrapolated differential cross sections. We obtain a unique set of solutions for δo1 and δo3 by requiring the calculated cross sections to agree with those extrapolated from K+π− elastic scattering and with those for K−π− scattering obtained in other experiments. We find δo1 increasing slowly from 0° at threshold and approaching 80° at m Kπ ⋍1150 MeV with no evidence of passing through 90° in the mass range studied. The phase shift δo3 decreases slowly from 0° at threshold to ⋍ − 30° at m Kπ ⋍ 1200 MeV .

Inclusive production of neutral strange particles by 147 GeV/cπ+/K+/p interactions in hydrogen

Results are presented from a study of inclusive neutral strange particle production by a 147 GeV/c tagged π+/K+/p beam in the Fermilab 30-inch hydrogen bubble chamber. The experiment made use of the proportional hybrid spectrometer system. Results are based on 995 KS0, 485 Λ, and 83 Λ found in a sample of 132 000 pictures. Cross sections are given for inclusive production of these particles by each of the three beam particles, and comparisons are made with measurements at other energies. Topological cross sections are also calculated, and KNO multiplicity scaling is investigated. Distributions are presented of invariant cross sections as functions of the Feynman scaling variable x and c.m. rapidity y. The transverse momentum-squared distributions with their fitted slopes are also given. Comparisons are made of the production characteristics for the three beam types.

Cross sections and charged multiplicity distributions for π−p and K−p interactions at 147 GeV/c

Abstract The results presented in this paper were obtained from a 105 000 frame exposure of the FNAL Hybrid Proportional Wire Chamber-30 inch Bubble Chamber System, in a tagged beam of 147 GeV/ c negative particles. Elastic, total and topological cross sections were obtained for both π − p and K − p interactions. Comparisons with other data, taken with various beam particles over large momentum intervals, show good agreement with KNO scaling, and similarity in the scaling behavior of σ n for the different beam particles.

Topological and leading particle cross sections for 147 GeV/c π− -p interactions☆

Abstract Results are reported based on a study of π − p interactions at 147 GeV/ c in the FERMILAB 30-inch Proportional Wire Hybrid Bubble Chamber System. We have measured the topological cross sections and separated two-prong elastic and inelastic channels. In addition, we have extracted leading particle cross sections using the increased momentum resolution of the downstream proportional wire chambers. We have compared our results with experiments and predictions of a simple fragmentation hyphothesis.

Direct electron pair production in π−p interactions at 16 GeV/c and a model for direct lepton and photon production at low pT☆

Abstract The production of prompt electron-positron pairs in 16 GeV/c π−p collisions has been measured using the LASS spectrometer at SLAC. An excess of events is observed above the estimated contributions of direct and Dalitz decay of known resonances in the kinematic range defined by 0.1⩽x⩽0.45, 0⩽pT⩽0.8 GeV/c and 0.2⩽M(e+e−)⩽0.7 GeV/c2. The excess signal decreases slowly with increasing M, but exhibits very steep x and pT2 dependence. The contribution of this signal to the e+e− and γ/π ratios is discussed. Detailed comparisons are made between e+e− distributions and the corresponding low-mass μ+μ− distributions, and a simple production mechanism is proposed which describes the 16 GeV/c data well. The implications for direct photon production are presented, and it is shown that the model provides simultaneously a good description of the experimental data on the (e/π) and (μ/π) ratios for pT

Spatial Resolution of the PEP-4 Time Projection Chamber

The spatial resolution and response of the segmented cathode pads of the PEP-4 TPC have been measured with data taken at 8.5 atmospheres of 80% Argon-20% Methane gas with a 4kG magnetic field. The dependence of the spatial resolution and pad response on drift distance and track-anode crossing angle is presented.

Calibration of the L3 Bgo Electromagnetic Calorimeter With a Radiofrequency Quadrupole Accelerator

Abstract A new calibration technique based on radiative capture of protons from an RFQ accelerator in a lithium target, which makes use of the resultant high intensity flux of 17.6 MeV photons, has been developed and tested. The technique is capable of calibrating the thousands of BGO crystals in the L3 electromagnetic calorimeter at once, with an absolute accuracy of better than 1% in 1–2 h. Systematic errors in the calibration, which have been studied earlier through Monte Carlo simulations, have been experimentally proven to be small and calculable, and are expected to be much less than 1%. When installed in the L3 experiment at LEP, this system will help ensure that the high resolution of the L3 electromagnetic calorimeter is maintained during running.

Inclusive and semi-inclusive ϱ0 production in π−p interactions at 147 GeV/c

Abstract We present data on inclusive and semi-inclusive ϱ 0 production in 147 GeV/ c π − p interactions. We find a total cross section of 7.3 ± 1.3 mb. Most of this cross section is found in the lower topology events (⩽ 10 prongs), and in the central and forward rapidity regions. The P T 2 dependence of ϱ 0 production, 〈: n > ϱ 0 per event, and the ϱ 0 / π + ratios are also discussed.

Measurement of Ionization Loss in the Relativistic Rise Region with the Time Projection Chamber

We present here some results obtained with the LBL Time Projection Chamber (TPC) regarding the particle identification by the measurement of the ionization losses in the relativistic rise region. This includes the method of calibration using 55Fe sources, the measurement of the resolution using cosmic rays, which shows an equivalent K-¿ separation of 4.8 standard deviations at 3.5 GeV/c, and the preliminary results obtained with multihadronic events from e+e- annihilations.

The effective-energy dependence of the charged particle's multiplicity in p/π+/K+ interactions on protons at 147 GeV/c

Abstract The energy dependence of the average of the charged multiplicity and its dispersion in π + /K + /p interaction on protons at 147 GeV/ c is found to be the same as in e + e − annihilations if an “effective energy” variable is used instead of the total energy. The effective energy S eff is defined as the invariant mass of all secondaries left after the two leading particles have been removed. Fitting the expression aS eff b to the average charge multiplicity 〈 n ch 〉, we find the power b to be in good agreement with the value of 0.25 predicted by Fermis statistical model and by Landaus hydrodynamical model.