μ子寿命测量_学习资料_new_evidence_for_the_existence_of_a_particle_of_mass_intermediate_between_the_proton_and_electron

NOVEMBER 1 1937 PHYSICAL REVIEW VOLUME 52 LETTERS TO THE EDITOR addressing the to this department, Closing dates for this department are, for the first issue of the month, the eighteenth of the preceding month, for the second issue, the third of the month. Because of Che late closing dates for the section no proof can be shown to authors. The Board of Editors does not hold itself responsible for the opinions expressed by the correspondents. Communications should not in general exceed 600 words in length. New Evidence for the Existence of a Particle of Mass between those of the proton and electron. If this is true, Intermediate Between the Proton and Electron it should be possible to distinguish clearly such a particle Anderson and Neddermyer' have shown that, for energies from an electron or proton by observing its track density up to 300 and 400 Mev, the cosmic-ray shower particles and magnetic deflection near the end of its range, although losses in lead pl res corre it is to be expected that the fraction of the predicted by theory for electrons. Recent studies of range? which the distinction can be made is very small, To and energy lossa indicate that the singly occurring cosmic- examine this possibility experimentally we have used the apparatus of Fig. 1. The three-counter are more penetrating than showe telescope consisting of tubes 1, 2, and 3 and a lead filter L for removing shower particles, selects penetrating ra ing magnetic deflection, Thus the natural assumptions directed toward the cloud chamber Cwhich is in a magnetic heir energy losses is sa field of 3500 and the singly occurring particles are electrons. The near the end of its range as it enters the chamber that here is no chance of emergence below. In order to reduce of the specific ionization that the penetrating rays are not the number of photographs of high energy particles, the protons. The suggestion has been made that they are tube group 4 was used as a cut-off counter with a circuit particles of electronic charge, and of mass intermediate so arranged that the chamber would be set off only in of the cloud chamber valve was delayed about one sec.to facilitate determination of the drop count along a track. Because of geometrical imperfections of the arrangement 20 ○3 C FIG. 1. Geometrical arrangement of apparatus FIG. 2. Track A

LETTERS TO THE EDITOR expansion for only a of the discharges of the telescope. At the present time 1000 photos have been taken (equiva lent to 4000 if the cut-off counter had not been used Two tracks of interest, in that they have ionization densities definitely greater than usual, have been obtained one A(see Fig. 2)is believed due to a proton and the other B (see Fig. 3)to a particle of mass approximately 130 times the rest mass of an electron. Track A which terminated in the lead strip at the center of the chamber exhibited an ionization density 2, 4 times as great as the usual thin tracks and an Hp value approximately 2X10 gauss cm in a direction to indicate a positive particle Track B which passed out of the lighted region above the lead plate had an ionization density about six times as normal thin tracks (the to permit an accurate ion count) and an Hp value of that i gauss cm. If it is assumed, as seems reasonable, 96×104 above, the sign is negative. If it is taken that the ionization density varies inversely as the velocity squared, the rest mass of the particle in question is found to be approximately 130 times the rest mass of the electron. Because of uncertainty in the ion ount this determination has a proba FIG, 3, Track B 25 percent. In any case it does not seem possible to explain this track as due to a proton traveling up, for the observed Hp value would indicate a proton of 4.4x105 electron one cm in the chamber The track is clearly visible for The only possible objection to the conclusions reached above is that the bending of track A is largely due to istortion but this is ver unlikely, for the deflection is quite uniform and has a maximum value greater than ter times any distortions usually encountered in the thin tracks of high C, STREEt E. C. STeVeNSON 可吧能 Variation of Initial Permeability with Direction in Single on Magnetic measurements at flux densities ranging from single crystals of 3.85 perce iron, in the crystallographic direction [100], [110] and [111]. Up to this ti reported on the magnetic properties of single crystals at ch low flux densi hat single crysta Large crystals were produced in an atmosphere of pure IG.4. Photograph of the track, of a penetrating particle of high were cut in the form of hollow parallelograms. Each

FIG. 2. Track

FIG. 3. Track B