K+−pInteraction From 140 to 642 MeV/c

Abstract

200 400 600 800 EFFECTIVE MASS (MeV) 1000FIGo 2. Histogram of the effective mass distribution of the two pions from the reaction p+p-*p+p + ir + + TT~0 The solid curve is the phase-space distribution normalized to the same total area. same spin and parity, and if the £ resonance does not exist, electromagnetic mixing could lead to an order of magnitude higher rate for (a) and (b) than for the usual oo -ir + + -n" + TT° (C). On the other hand, Gell-Mann et_aL 8 calculate the decay mode ratio a/c to be only ~5%.To search for the mode co ^7r + + 7r", we have plotted in Fig. 2 the effective mass m * of the 7r + 77" combination from 683 events of the type £+£-•/>+/> +7T++ 77~. The co decay should appear as a peak at -770 MeV, within the broad band (700-800 MeV) of the p° decay. Neither the twoir decay of the u> nor any sign of the expected p°-*7T + + 77~ is observed. The absence of the p° can possibly be explained by the fact that it has a cross section comparable to the co, and this small number of events, spread over the broad effective-mass range of the p°, would not be observed. Considering the strength of the §, § up isobar, and the possibility of final state interactions, it is not surprising that multiple-pion resonances appear to have small cross sections when there are two nucleons present.A detailed investigation of the energy dependence of the K + -proton scattering cross section at low momenta has been carried out. In the region from 140 to 642 MeV/c, the nuclear cross section varies little with energy. The cross sections are distinctlv lower than values quoted earlier. 1 The momentum dependence of the phase shifts below 300 MeV/ c can only be interpreted as s-wave scattering and does not admit isotropic £-wave solutions such as were obtained as possible ambiguities at 810 MeV/ c. 2 The isotropy in the differential cross sections and the constructive interference with Coulomb scattering at each of the momenta show that the repulsive s-wave character of the K + -p T = l state persists throughout this region.An s-wave effective-range fit to the experimental 135

Composite-fermion edge states, fractional charge, and current noise

“…19,20 The singular gauge transformation 2,21,22 that transforms electrons into composite fermions by attaching to them tubes of fictitious magnetic flux preserves charge, and therefore the charge of a composite fermion is equal to that of an electron. However, it was pointed out by Goldhaber and Jain 23 that the local charge associated with the composite fermion is dressed by the presence of the other composite fermions in the system and thus becomes fractional, the fractions being in agreement with the fractional quasiparticle charges predicted earlier by Laughlin and others. 1,24,25 For example, for the fractional filling ν = 1/3 of the lowest Landau level the dressed quasiparticle charge −e * equals −e/3.…”

“…In Section III I discuss electric current fluctuations in the fractional quantum Hall regime within the framework of the edge state model, 4,5 and show that to understand these fluctuations one must consider the interactions between the composite fermions, the important interactions being those mediated by the fictitious electric field 28,29,30,23 associated with composite fermion currents. These interactions renormalize the current fluctuations and their effects must be calculated self-consistently.…”

K20pInteractions at Low Momentum

“…Our determination of R shows that the only acceptable solution is the one consistent with the Dalitz-Tuan interpretation of the F o *(1405) as afflV virtual bound-state resonance. 6 Thus, while the negative-strangeness amplitudes in the K 2°p interactions are purely in the isospin T-1 state, our results coupled with those from K + p, K + d, 7 andK"7> experiments determine the spin and parity of the T= 0 resonance F o *(1405) to be i"". Furthermore, we find a considerable amount of P-wave amplitude to be present in the reactionK 2°+ p-~ A 0 +TT + , in which a strong forward-backward asymmetry is observed in the production distributions.…”

Hairs on the Unicorn: Fine Structure of Monopoles and Other Solitons

“…Recently it has been argued that the quasiparticles of the fractional quantum Hall effect (FQHE) should be treated as electrons dressed by the FQHE medium, so that their fractional charge is fractional in exactly the same sense as for an electron inside an insulator [18]. There still is something special about these quasiparticles, which can be described in two alternate ways: 1) The Aharonov-Bohm or Lorentz-force charge is renormalized by the same factor as the local or Gauss-law charge [13].…”

“…In ordinary insulators, only the latter charge is renormalized. 2) The electromagnetic field strength is renormalized by the same factor as the Gauss-law charge [18]. This renormalization would be undefinable in ordinary three-dimensional systems, but here refers to the ratio of the effective field acting on excitations moving in the FQHE layer to the field as measured in standard ways just outside the layer.…”