Giacomo Morpurgo

The electric neutrality of matter: A summary

Abstract We summarize the results of our experiments on the electric neutrality of matter. The number of isolated quarks in steel is less than one in 3.7 mg, corresponding to less than one in 2.2 × 1021 nucleons. The upper limit to the electron proton charge difference is (0.8 ± 0.8) 10−21 e. The procedure to establish this upper limit is discussed in some detail. The above results are compared with those from other experiments.

SEARCHES OF FRACTIONALLY CHARGED PARTICLES IN MATTER WITH THE MAGNETIC LEVITATION TECHNIQUE

Abstract A survey is given of the experiments performed with the magnetic levitation electrometer to search for stable fractional charges in matter. After a general introduction, illustrating the principle of the method, an analysis is presented of the electric forces acting on the levitating object (who se knowledge is essential to determine the residual charge). This is followed by a short account of the historical evolution of the subject, after which we proceed to a detailed description of the ferromagnetic levitation electrometer used in our laboratory and of the results obtained. The main differences with the Stanford diamagnetic (superconducting) instrument are also illustrated. The final section contains a concise summary of the other experiments of search of quarks in matter, in particular of the Millikan automated ones.

General QCD parametrization of the charge radii of p , n and Δ+

Abstract Using the general parametrization method we discuss the relation: r 2 ( p )− r 2 ( n )= r 2 ( Δ + ) between the charge radii of p , n and Δ + derived in a recent quark model calculation of Buchmann, Hernandez and Faessler [Phys. Rev. C 55 (1997) 448]. We show that the above relationship is obtained by the general parametrization if one excludes three index and closed loop terms, which are indeed absent in the model quoted above; this checks the correctness of the calculation of Buchmann et al. on this point. However in QCD, where three index terms exist, arising e.g. from two gluon exchanges between three different quark lines, the above relationship is modified; an estimate indicates that this modification should be between 10% and 20%.

Diamagnetism of powder and bulk superconducting YBCO measured with a new magnetic levitometer

Abstract Measurements of the diamagnetic properties of bulk and powder superconducting YBCO performed with a new magnetic levitometer are reported; the instrument can operate at values of the magnetic field and gradient variable with continuity, up to high magnetic gradients (30 kG/cm) and can visualize individually each object while levitating, down to a size of 4 μm. The observations on bulk material do establish how the magnetization and susceptibility of pieces of YBCO with a size of the order of 1 mm decrease on increasing the magnetic field. As to the powder the magnetization and susceptibility are generally smaller than the corresponding quantities for the bulk. The powder grains are seen levitating with a very wide spectrum of values of their susceptibility. For any choice of the magnetic field, from 650 G to 12 kG some grain levitates; on reaching the highest field and gradient all the powder has been levitated, except for very few grains, a countable number of them. It can be shown that a 5 μm grain seen levitating at the highest value of the magnetic gradient is so full of fluxoids that the addition of only four of them would cancel entirely its diamagnetism.

New Results in the Search of Quarks in Matter by the Magnetic Levitation Electrometer

Abstract The results of many runs performed levitating in succession several spheres without opening the levitation chamber show the existence of an additional (magneto-electric) force acting on the sphere. Ignoring this force in the analysis of the data produces “spurious” fractional charges.

Confirmation of the electric neutrality of matter at the milligram level

Abstract The procedure to identify, measure and subtract the magneto-electric force acting on levitating spheres is described. All the 25 steel spheres (with a total mass of 1.75 mg) examined after the elimination of the effects of such a force produce the result: Nquarks/Nnucleons ⩽ 10−21.

Baryon octet magnetic moments to all orders in flavor breaking: An application to the problem of the strangeness in the nucleon

Using the general QCD parametrization (GP) we display the magnetic moments of the octet baryons including all flavor breaking terms to any order. The hierarchy of the GP parameters allows to estimate a parameter

On the miracle of the Coleman–Glashow and other baryon mass formulas

g_{0}

SCALING OF THE NUCLEON E.M. ELASTIC FORM FACTORS: A GENERAL DERIVATION

related to the quark loops contribution of the proton magnetic moment; its order of magnitude is predicted to be inside a comparatively small interval including the value given recently by Leinweber et al. by a lattice QCD calculation

The General QCD parametrization and the hierarchy of its parameters: Why some simple models of hadrons work so well

Abstract Due to a new measurement of the Ξ0 mass, the Coleman–Glashow formula for the baryon octet e.m. masses (derived using unbroken flavor SU3) is satisfied to an extraordinary level of precision. The same unexpected precision exists for the Gell Mann–Okubo formula and for its octet-decuplet extension (G. Morpurgo, Phys. Rev. Lett. 68 (1992) 139). We show that the old question “why do they work so well?” is now answered by the general parametrization method.