This report reviews the experimental investigation of high energy e + e − interactions by the MARK J collaboration at PETRA, the electron-positron colliding beam accelerator at DESY in Hamburg, Germany. The physics objectives include studies of several purely electromagnetic processes and hadronic final states, which further our knowledge of the nature of the fundamental constituents and of their strong, electromagnetic and weak interactions. Before discussing the physics results, the main features and the principal components of the MARK J detector are discussed in terms of design, function, and performance. Several aspects of the on-line data collection and the off-line analysis are also outlined. Results are presented on tests of quantum electrodynamics using e + e − → e + e − , μ + μ − and τ + τ − , on the measurement of R , the ratio of the hadronic to the point-like muon pair cross section, on the search for new quark flavors, on the discovery of three jet events arising from the radiation of hard noncollinear gluons as predicted by quantum chromodynamics, and on the determination of the strong coupling constant α s .
SUMMARY OF RESULTS FOR R FROM TOTAL OF 2595 HADRON EVENTS. INCLUDES RED = 1046, 1079, 1072 AND 1114.
MEAN THRUST AND THRUST DISTRIBUTION (1/N)*DN/DTHRUST AT 13, 17, 22 AND 30 GEV. SOMEWHAT DETECTOR DEPENDENT. INCLUDES RED = 1079 AND 1072. SEE ALSO RED = 1114. ALSO JET ANALYSIS USING FOX-WOLFRAM MOMENTS.
OBLATENESS DISTRIBUTION AT 17 AND 27.4 TO 31.6 GEV. SEE RED = 1146.
We have identified 262 doubly tagged two-photon events. A subset of the data shows an enhancement of 21 events in the inclusive two-photon mass squared distribution between 0.8 and 2.2 GeV 2 . If these events result from spin 2 resonance production then Γ γγ = 9.5 ± 3.9 ± 2.4 keV (statistical and systematic). From another subset of 58 events in which the final state could be classified we determine the two-photon hadron to muon cross section ratio R γγ = 1.1 ± 0.3 ± 0.3.
ELECTRON BEAM ENERGIES OF 3.0 AND 3.6 GEV.
αα elastic scattering was measured at 4.32 GeV/ c and 5.07 GeV/ c incident momenta. The four-momentum transfer range, extending from −0.05 to −0.77 (GeV/ c ) 2 , covers the first and second minimum regions. The results are compared with calculations based on Glauber theory.
ERRORS SHOWN INCLUDE STATISTICAL ERRORS, QUASIELASTIC CONTRIBUTION SUBTRACTION ERROR, AND AN ASSYMETRIC ERROR RESULTING FROM THE UNCERTAINTIES AS TO THE ORIGIN OF THE WIDENING OF THE ELASTIC PEAK.
ERRORS SHOWN INCLUDE STATISTICAL ERRORS, QUASIELASTIC CONTRIBUTION SUBTRACTION ERROR, AND AN ASSYMETRIC ERROR RESULTING FROM THE UNCERTAINTIES AS TO THE ORIGIN OF THE WIDENING OF THE ELASTIC PEAK.
None
No description provided.
DOMINANT NATURAL PARITY EXCHANGE.
EVIDENCE FOR FORWARD DIP FOR -TP < 0.1 GEV**2.
None
No description provided.
No description provided.
No description provided.
Lambda production is studied in K − p interactions at 32 GeV/ c . The total Λ cross section is 2.31±0.03 mb . Using the measured Λγ combinations we find that (31±4)% of all Λ's are produced via the Σ 0 → Λγ decay. About 60% of the Λ's are associated with either a N N or K K pair; about 40% of the Λ's are produced through the hypercharge annihiltion reaction K − p→ Λ + π 'a. The two-peak structure of the invariant x distribution can be related to fragmentation processes. The Λ is found to be unpolarized in the target fragmentation region, whereas a transverse polarization is observed for forward produced Λ's. As a function of p ⊥, a polarization effect is measured at medium p ⊥.
No description provided.
No description provided.
No description provided.
We give cross sections for annihilation and non-annihilation reactions in p p interactions at 8.8 GeV. The non-annihilation data are compared with pp data from the same experiment. We compare data on resonance production and on the impact parameter structure of the final states in p p annihilation and non-annihilation and pp interactions. We investigate the charge structure of the 2 π + 2 π − π 0 final state, and find it consistent with a simple quark model.
NORMALIZED TO A TOTAL AP P CROSS SECTION OF 55.9 MB. ANNIHILATION CROSS SECTIONS.
NORMALIZED TO A TOTAL AP P CROSS SECTION OF 55.9 MB. NON-ANNIHILATION CROSS SECTIONS.
NORMALIZED TO A TOTAL P P CROSS SECTION OF 40.0 MB.
We present a study of the reactions p p → p p π 0 , p p → p n π + , and p p → n p π − at 8.8 GeV/ c . Cross sections for the reactions are given, and the main features of the data are shown. The data are compared with the predictions of the Deck model, and evidence is presented for the presence of baryon exchange in the Deck amplitude.
No description provided.
In a high statistics (90 events/μb) bubble chamber experiment, the reactions π − p→K s 0 K ± π ∓ n have been studied at 3.95 GeV/ c . A significant enhancement is observed in the ( K K π) system which we attribute to the production of the E(1420) meson. For its mass, M , and width, Λ, we find M =1426±6 MeV and Γ =40±15 MeV. The E(1420) quantum numbers are determined to be I G J P =0 + 1 + with a branching ratio E → K ∗ K + c.c E →[δπ+( K ∗ K + c.c. )]=0.86±0.12 , where δ→ K K . The cross section for the reaction π − p→En, with E→K 0 K ± π ± , is 8.2±1.0 μ b. Forward and backward productions are observed in the approximate ratio 2:1. The SU(3) assignment of the E(1420) meson is discussed.
BACKGROUND SUBTRACTED.
No description provided.
No description provided.
An analysis is presented of the reaction K − p → K 0 π − p at 4.2 GeV /c incident momentum, using analytical techniques in fully dimensional phase space. This methods allows to isolate the contributions of the 0 + , 1 − and 2 + (K π ) partial waves in various helecity Separating well-understood contributions from the rest, the method is particularly useful for the detection of small effects (≈1% of the total final-state cross section) not visible in the mass distributions: (i) small cross-section contributions of 3 − (K π partial waves, K ∗ (1780), are unambiguously isolated; (ii) 3.5σ evidence is given for Σ(1480) in the (p K 0 ) system; (iii) effects due to a second K π P-wave or the possible presence of a doubly peripheral mechanism are discussed. The method furthermore allows simultaneous treatment of the (K π ) partial waves, p π ) partial waves and their interferences and of a Σ(1765) signal (with spin 5 2 ). While interferences within the (K π ) and within the (p π ) systems are strongly determining the corresponding distributions, no interference between these systems is needed.
CHANNELS CONTRIBUTING TO K- P --> AK0 PI- P. M/ETA IS ABSOLUTE VALUE OF Z-COMPONENT OF SPIN/EXCHANGE NATURALITY.
Forum