Bruno Pontecorvo: From slow neutrons to oscillating neutrinos

W. Pauli, “On the earlier and more recent history of the neutrino,” in Neutrino Physics, edited by K. Winter (Cambridge U.P., Cambridge, 1991), pp. 1–25; quote on pp. 4–5.

For an English translation of the whole letter, see

L.

Brown

, “,” (), – ().

F.

 

Rasetti

, “,”  , – ();

F.

Rasetti

, , – ().

Quoted in

J.

 

Chadwick

, “,”  , – ().

For a detailed discussion about the difficulties of the electron–proton model of the nucleus, see R. H. Stuewer, “The nuclear electron hypothesis,” in Otto Hahn and the Rise of Nuclear Physics, edited by W. R. Shea (Reidel, Dordrecht, 1983), pp. 19–67.

The “neutrino,” a funny and grammatically incorrect contraction of “little neutron” (in Italian neutronino), entered the international vocabulary through Fermi, who used it sometime between the conference in Paris in July 1932 and the Solvay Conference in October 1933, where Pauli used it. The word arose in a humorous conversation at the Istituto di via Panisperna. Fermi, Amaldi, and a few others were present and Fermi was explaining Pauli’s hypothesis about his “light neutron.” To distinguish this particle from the Chadwick neutron, Amaldi jokingly used this funny name. Quoted by Ugo Amaldi in the preface to 20th Century Physics: Essays and Recollections. A Selection of Historical Writings by Edoardo Amaldi, edited by G. Battimelli and G. Paoloni (World Scientific, Singapore, 1998).

W. Pauli, “Structure et Propriétès des Noyaux Atomiques,” Rapp. Septième Conseil Phys. Solvay, Brussels 1933 (Gauthier-Villars, Paris, 1934), p. 324. An English translation of the comments can be found in Ref. 2, p. 27.

His first article appeared in December 1933 with the title “Tentativo di una teoria dell’emissione dei raggi β” (Tentative theory of beta rays),

E.

 

Fermi

,  (), – (), but Fermi intended to announce the results of his theory in a letter to Nature.

The submission was rejected with a note explaining that it was “too remote from physical reality to be of interest to the readers.” (F. Rasetti, introductory note to Fermi paper Nos. 76, $80a,$ $80b,$ $80c,$ in E. Fermi, Note e Memorie (Academia Nazionale dei Lincei, University of Chicago Press, Roma, 1962), Vol. I, p. 540).

He then sent a longer paper, “Tentativo di una teoria dei raggi β,” to Nuovo Cimento and its German translation to Zeitschrift für Physik (“Versuch einer Theorie der β-Strahlen. I.”);

E.

 

Fermi

,  , – () and

E.

Fermi

, , – ().

B. Pontecorvo, “The infancy and youth of neutrino physics: some recollections,” in Colloque International sur l’Histoire de la Physique des Particules, Journal de Physique, Suppl. (Paris) 43(2), 221–236 (1982).

G. C.

Wick

, “,” , – ().

H.

 

Bethe

and

R.

 

Peierls

, “”  , – ();

H.

Bethe

and

R.

Peierls

, , – ().

In 1935 Nahmias was able to place an upper limit at one primary encounter of neutrinos with matter in $3×106 km$ of path in air. See

M. E.

Nahmias

, “,” , – ().

J.

 

Chadwick

and

D. E.

 

Lea

, “,”  , – ().

In his Bakerian lecture of 1920 Rutherford already had speculated about a neutral (composite) particle, which later he named the neutron. He and his co-workers had searched for it during a twelve-year period, and it is well known that Chadwick’s actual discovery took only “a few days of strenuous work.” See A. Pais, Inward Bound (Oxford U.P., Oxford, 1986), quote on p. 397.

B. Pontecorvo, “The discovery of slow neutrons: Some recollections,” lecture delivered at the Jubilee session of the IV International School in Neutron Physics in Dubna, on 8 July, 1982, in B. Pontecorvo, Selected Scientific Works. Recollection on B. Pontecorvo, edited by S. M. Bilenky, T. D. Blokhintseva, I. G. Pokrovskaya, and M. G. Sapozhnikov (Società Italiana di Fisica, Editrice Compositori, Bologna, 1997), pp. 388–391, quote on p. 388.

E.

 

Fermi

,

E.

 

Amaldi

,

B.

 

Pontecorvo

,

F.

 

Rasetti

, and

E.

 

Segrè

,  (), – ().

The second article, with the same title, was by

E.

Fermi

,

B.

Pontecorvo

, and

F.

Rasetti

, “Influence of hydrogenous substances on the radioactivity produced by neutrons. II,” (), – ().

B.

Pontecorvo

, “,” (), ().

B.

Pontecorvo

, “,” , – (). Between 1941 and 1943 Pontecorvo filed four patent applications for geophysical prospecting instrumentation.

For thorough discussions of Pontecorvo’s scientific work and personal recollections, see S. M. Bilenky, “B. M. Pontecorvo and the neutrino,” in B. Pontecorvo, Selected Scientific Works, Ref. 13, pp. XIII–XVIII; G. Fidecaro, “Bruno Pontecorvo: From Rome to Dubna,” Ref. 13, pp. 472–486; S. T. Petcov, “On B. Pontecorvo contributions to weak interaction and neutrino physics,” in Proceedings of the Sixth International Workshop on Neutrino Telescopes, Istituto Veneto di Scienze, Lettere ed Arti, Venice, 22–24 February, 1994, edited by M. Baldo Ceolin, pp. 17–26.

B. Pontecorvo, Report P.D.-141, Chalk River Laboratory, 21 May, 1945.

See G. Fidecaro, “Bruno Pontecorvo: From Rome to Dubna,” Ref. 17, p. 478.

B. Pontecorvo, “Inverse β process,” in B. Pontecorvo, Selected Scientific Works, Ref. 13, pp. 21–29. It was published as Report P.D.-205 of the National Research Council of Canada Division of Atomic Energy, Chalk River, Ontario, 20 November 1946. It was declassified and issued by the Atomic Energy Commission in 1949.

By that time the transformation of a free neutron into a proton had not yet been detected, although plans for its detection, as well as for the study of the angular distribution of the proton and electron emitted, had been made in several laboratories, including Chalk River, where Pontecorvo was working.

O.

Hahn

and

L.

Meitner

, “,” , – (). They introduced the recoil method of radioactive analysis and found that a negatively charged plate placed near a plate coated with radioactive elements became radioactive by collecting the recoil atoms whose recoil energy could be analyzed by a retarding field.

W. Pauli, Rapp. Septième Conseil Phys. Solvay, Brussels 1933 (Gauthier-Villars, Paris, 1934), p. 324.

A. I.

Leipunski

, “,” , – ().

The experiments initiated in 1936 by Leipunski, Ref. 24, with the residual-nuclei distribution following the $β+$-decay of $C611$⁠, continued with the more satisfactory 1938 experiments by Crane and Halpern. See

H. R.

Crane

and

J.

Halpern

, “,” , – (), who measured the recoil of $Ar1838$ in $Cl1738 β−$-decay.

J. S.

 

Allen

, “,”  , – ().

The electron capture transition $p+e−→n+neutrino,$ mostly involves K-electrons, which have a high probability of being captured inside the nucleus due to their small binding energy, even in heavy nuclei. This process is another inverse β reaction that was suggested in 1934, first by G. C. Wick, Ref. 9, and independently by Bethe and Peierls, Ref. 10, pp. 689–690, and observed by Alvarez in 1938. See

L. W.

Alvarez

, “,” , – ().

J. C. Jacobsen and O. Kofoed-Hansen, “Recoil of the nucleus in β-decay,” Det. Kgl. Danske Vidensk. Selskab, Mat.-Fys. Med. 23, paper No. 12 (1945).

Their experiment is thoroughly discussed in

H. R.

Crane

, “,” , – (), quote on pp. 285–288.

H. R. Crane and J. Halpern, Ref. 25, and “Recoil of nucleus in β-decay,” Phys. Rev. 56, 232–237 (1939).

Their experiment, as well as Allen’s, was considered a “More satisfying direct observation of the neutrino” by Konopinsky in his review “Beta-decay,” Rev. Mod. Phys. 15, 209–245 (1943).

C. W.

Sherwin

, “” , – (). Sherwin tested the single neutrino hypothesis, and examined the nuclear recoil spectrum from a β-emitting nucleus in order to define the direction and energy of the electron and the direction of the recoil.

Their experimental setup used the K-capture reaction in $A37.$ The recoil of the Auger electrons can be neglected, so the momentum of the neutrinos manifests itself only in the recoil of the Cl atoms. See

G. W.

Rodeback

and

J. S.

Allen

, “” , – ().

R.

Davis

, Jr., “,” , – ().

Reines and Cowan later considered the possibility that the neutrino emitted from fission could not survive “the 11 meter journey from the reactor” to the detector. F. Reines, “Neutrinos to 1960-Personal recollections,” in Colloque International sur l’Histoire de la Physique des Particules, Ref. 8, pp. 237–255, quote on p. 252.

B.

Pontecorvo

, “,” , – () (emphasis in original).

S. M.

Dancoff

, “,”  , – ().

G.

Gamow

and

E.

Teller

, “,” , – ().

F.

Reines

, “,” , – (), quote on p. 11.

The technique of scintillation counting received great impetus from the development of the photo-multiplier tube and the crucial observation that liquids could be made to scintillate with high efficiency when the scintillating compound was at low concentration. See

M.

 

Ageno

,

M.

 

Chiozzotto

, and

R.

 

Querzoli

, “,”  , – ();

G. T.

 

Reynolds

,

F. B.

 

Harrison

, and

G.

 

Salvini

, “,”  , ();

H.

 

Kallmann

, “,”  , – ();

M.

Ageno

,

M.

Chiozotto

, and

R.

Querzoli

, “,” , ().

F. Reines, “The neutrino from poltergeist to particle,” Nobel Lecture, 8 December 1995. Available at 〈http://www.nobel.se/physics/laureates/1995/reines-lecture.pdf〉.

M.

Conversi

,

E.

Pancini

, and

O.

Piccioni

, “,” , – ().

M. Pinault interviewed Pontecorvo on 9 December 1991. For the page of the original document reproducing the quoted sentence of the interview with manuscript corrections by Pontecorvo, see J. Laberrigue-Frolow, “Bruno Pontecorvo and Paris,” in B. Pontecorvo, Selected Scientific Works, Ref. 13, pp. 461–471, quote on p. 469. Pontecorvo’s date is incorrect; actually his very first proposal was in 1945.

They developed a complete technique for precise measurements of energy:

G.

 

Hanna

,

D.

 

Kirkwood

, and

B.

 

Pontecorvo

, “,”  , – ();

G.

Hanna

,

D.

Kirkwood

, and

B.

Pontecorvo

, “,” , – ().

D. C.

Curran

,

J.

Angus

, and

A. L.

Cockcroft

, “,” , – ().

H. A.

Bethe

, “,” , – (). In this paper, neutrinos were not included explicitly in the nuclear reactions.

Quoted in G. Fidecaro, “Bruno Pontecorvo: from Rome to Dubna,” Ref. 17, p. 479.

E.

 

Majorana

, “,”  , – ();

English translation by

L.

Maiani

, “,” , – ().

G.

Racah

, “,” , – ().

C. D.

Ellis

, “,” , – (), p. 447.

Counters with low effective background found their natural application in the measurement of low-energy β-spectra of gaseous materials, as for instance, tritium.

B.

 

Pontecorvo

,

G. C.

 

Hanna

, and

D.

 

Kirkwood

, “,”  , ();

G. C.

Hanna

and

B.

Pontecorvo

, “” , – ().

B. Pontecorvo, “Una nota autobiografica,” in B. Pontecorvo, Selected Scientific Works Ref. 13, pp. 424–430. Only in 1978 Pontecorvo was allowed to travel abroad, to Italy, to take part in the celebrations in honor of Edoardo Amaldi on the occasion of his 70th birthday. In 1991/1992, when he was writing his biography he confided to his friend Gershtein: “Nearly all my life I considered communism a science, but I now see it is not a science, but a religion. I thought Sakharov a very good, but naive person, and now I see it was I who was naive.” Recollections about Pontecorvo’s life in USSR can be found in S. S. Gershtein, “Interesting recollections and reflections about Bruno Pontecorvo,” in B. Pontecorvo, Selected Scientific Works, Ref. 13, pp. 440–454, quote on p. 445.

S.

Turchetti

, “,”  (), – ().

L. Alvarez, Report UCRL-328, 18 April 1949, University of California, Berkeley.

R. Davis, Jr., “A half-century with solar neutrinos,” Nobel Lecture, 8 December 2002. Available at 〈http://www.nobel.se/physics/laureates/2002/davis-lecture.pdf〉, quote on p. 59.

R.

Davis

, Jr., “,” , – ().

R.

Davis

, Jr., “,” , – ().

R.

Davis

, Jr., “,” , ().

R. Davis, Jr., “An attempt to observe the capture of reactor neutrinos in chlorine-37,” in Radioisotopes in Scientific Research, Proceedings of the First UNESCO International Conference, Paris 1957 (Pergamon, London, 1958), Vol. 1, p. 728.

R.

Davis

, Jr. and

Don S.

Harmer

, “,” , ().

R.

Davis

, Jr., “,” , – ().

J. N.

Bahcall

, “,” , – ().

R.

Davis

, Jr.,

D. S.

Harmer

, and

K. C.

Hoffman

, “,” , – ().

B. Pontecorvo, “Mesonium and antimesonium,” Ref. 13, pp. 144–147, quote on p. 146.

B. Pontecorvo, “Inverse β-processes and non-conservation of lepton charge,” Ref. 13, pp. 152–154, quote on p. 153.

Reference 63, p. 154.

B. Pontecorvo, “Neutrino experiments and the question of leptonic-charge conservation,” Ref. 13, pp. 249–258, quote on p. 256.

Reference 65, quote on p. 253. For a detailed discussion on these items see

S. M.

 

Bilenky

and

B.

 

Pontecorvo

, “,”  , – ();

W. M.

 

Alberico

and

A. M.

 

Bilenky

, “,” hep-ph/03066239.

See also S. Bilenky, “Neutrinos,” Encyclopedia of Physical Science and Technology, 3rd ed. (Elsevier, Amsterdam, 2004), Vol. 10, p. 395.

They derived explicit formulas describing oscillations $νe−νμ$ assuming that $νe$ and $νμ$ are a superposition of two Majorana neutrinos.

V.

Gribov

and

B.

Pontecorvo

, “,” (), – ().

See 〈http://www.nobelprize.org/physics/laureates/2002/index.html〉.

Y.

 

Fukuda

et al. (Super-Kamiokande Collaboration), “,”  , – ();

Q. R.

 

Ahmad

et al. (SNO Collaboration), “,”  , - ();

K.

 

Eguchi

et al. (KamLAND Collaboration), “,”  , ();

M. H.

Ahn

et al. (K2K Collaboration), “,” , - ().