Darkness visible : neutrinos and conservation laws

1. Darkness visible : neutrinos and conservation laws

2. Conservation Laws • Even if you don’t know the details of what is going on in a system you can make accurate statements about it Momentum: Sir Isaac Newton 1670 James Prescott Joule 1850 Energy 1807 Thomas Young – first modern use of Energy = mv2 1820 Carnot - Heat and Work are related Heat = Work 1850 Joule. Shows that electrical, thermal and mechanical energy are all interconvertible and measures the factors that relate them

3. Energy Conservation Ludwig Boltzmann Rudolf Clausius Lord Kelvin “if today a quite new natural phenomena were to be discovered one would be able to obtain at once from (the energy conservation principle) a law for this new effect, while otherwise there does not exist any axiom which could be extended with the same confidence to all processes in nature” Max Planck 1887 Josiah Willard Gibbs By the end of the nineteenth century the idea of the conservation of energy was well established.

4. The discovery of radioactivity (X-Rays) 1895 Friday November 8th Roentgen observes X-Rays “Der Roentgen ist wohl verruckt geworden” December 28th submitted paper on his observations including radiographs Cathode rays calls a fluorescence on the inside of the tube. Was trying to get the cathode rays outside the tube and instead observed the unknown rays outside the tube

5. The discovery of radioactivity (X-Rays) • December 28th submitted paper on his observations including radiographs • 1896 January 1st sent preprints to colleagues including Arthur Schuster in Manchester – “Now the fun can start” and it did. Papers, books, pamphlets and the first recorded medical use in February! • January 7th : Evening standard. • “Among the practical uses of the new discovery, it is stated that it will henceforth be possible for surgeons to determine by help of this new branch of photography the exact position of any bullet that may be imbedded in the human body, or, again, to render visible any fractures there may be in the bones prior to performing any operation on the respective part of the body.” • By the end of February X-Rays are being used for diagnosis in at least 7 different countries.

6. Portable X-Ray machine 1896 Hargrave Hartley accuses his wife Elizabeth Ann of adultery and shoots her four times in the head. She is too weak to be moved. Arthur Schuster (Manchester University) -sends assistants to take an X-Ray. 70 minute exposure

7. The discovery of radioactivity 1896 January 13thLe Matin publishes a story on X-Rays January 20th meeting at the Academie of Sciences on X-Rays. Poincare presents the results. Henri Becquerel asks where the X-Rays come from and is told by Poincare the fluorescence on the tube. Becquerel immediately interested. He starting working with his father on phosphorence as long ago as 1881 and had produced “very beautiful lamellas of potassium uranyl disulphate” Becquerel conceives the question are these rays associated with all sources of phosphorescence. Start to work studying phosphorescent salts which he has in his lab. Nothing interesting. The lemallas are out on loan and they don’t return until February 24th paper present to the academy on the blackening of photographic plates by phosphorescent uranium salts ….. February 26th and 27th – no sun in Paris ……….

8. Energy non conservation in radioactivity 1896 Radioactivity – where is the energy coming from? Phosphoresence energy comes from sunlight and decays away – not so radioactivity. 1898 Polonium – worse Marie Curie “Is energy conservation actually universal?” 1898 Crookes “Is the energy being concentrated from the surrounding air?” 1899 Curie suggests that radioactivity may be accompanied by a loss of mass from the substances

9. Energy non conservation in radioactivity 1900 Thompson believed the atoms were the energy source 1902 Lord Kelvin said that radioactivity – placed a question mark over the universal application of the conservation of Energy

10. Energy non conservation in radioactivity 1904 Einstein provides the theory which will allow a resolution of the problem 1911 Rutherford still refers to the energy issue 1920 Use of masses and Einstein’s theory to explain atomic stability and instability 1807 Conservation of Energy suggested 1887 Firmly established 1899 Universal applicability questioned 1910 Solution exists All through this period the puzzle of half-life was also confusing people

11. Energy non conservation in beta decay • Alpha particles are all have the same energy • 1906 Otto Hahn and Lisa Meitner start to investigate the energy spectra of beta rays • Disputes – the spectrum is mono-energetic, a series of lines,. continuous • How to measure the energy? • 1914 Chadwick establishes that it is continuous • using a magnetic spectrometer

12. Energy non conservation in beta decay Beta particles (electrons) have all possible energies from zero to a maximum which corresponds to Energy conservation Energy is being lost ? Is the energy being redistributed somehow? End-point

13. Energy non conservation 1910 Einstein – already trying to kill quantum mechanics “I have high hopes of solving the radiation problem and that without light quanta …… One must renounce the energy principle in its present form“ 1911 Solvay – Einstein rejected this as an option

14. Energy non conservation 1916 Nernst suggests that in quantum systems energy is only conserved statistically 1919 C.G. Darwin – suggests that we can avoid the complications of quantum theory if we reject exact conservation 1924 Bohr, Kramers and Slater – energy conservation and causality only valid statistically in quantum transitions 1925 Compton and Simon show Energy Conservation in Compton in individual events when an electron scatters off a photon

15. Energy non conservation in beta decay 1927 Ellis and Wooster do a measure the total heat output from a radioactive source and show the average energy per decay is the average electron energy. 1929 Bohr is convinced that the solution lies outside classical physics. Meitner and Hahn replicate Ellis and Wooster. Meitner and Hahn replicate Ellis and Wooster. Pauli to Bohr “… almost convinced the spectrum cannot be explained by secondary processes” G.P. Thompson – “we cannot know the electrons speed” ... J.J Thompson’s son Klein – using Dirac’s equation shows a slow electron can pass through a steep barrier with energy > twice the electron rest and emerge with negative energy. No one is happy with a breakdown in the energy law. But no-one can shake of the feeling that this might be the solution

16. Pauli in turmoil 1930 Pauli – his mother dies; he is drinking heavily; in Jungian analysis 26 November his divorce is finalised. His world is falling about and he thinks the unthinkable – he writes a famous letter to group of physicists about to meet to discuss the problems of radioactivity and beta decay LiebeRadioaktive Damen un Herren, Wie der UberbringerdieserZeilen, den ichholdvolletansuhorenbitte. Ihnen das naherenauseinandersetsenwird, bin ichangesicht der “falschen” Statistik der N und Li=6 Kerne, sowie des kontinuierlichen beta-Spektrum auf oinenverswiefeltenAuswegverfallen

17. Pauli’s “Neutrino” Dear Radioactive Ladies and Gentlemen: Zurich, December 4, 1930 I beg you to receive graciously the bearer of this letter who will report to you in detail how I have hit on a desperate way to escape from the problems of the "wrong" statistics of the N and Li6 nuclei and of the continuous beta spectrum in order to save the "even-odd” rule of statistics and the law of conservation of energy. Namely the possibility that electrically neutral particles, which I would like to call neutrons might exist inside nuclei; these would have spin 1/2, would obey the exclusion principle, and would in addition differ from photons through the fact that they would not travel at the speed of light. The mass of the neutron ought to be about the same order of magnitude as the electron mass, and in any case could not be greater than 0.01 proton masses. The continuous beta spectrum would then become understandable by assuming that in beta decay a neutron is always emitted along with the electron, in such a way that the sum of the energies of the neutron and electron is a constant. Now, the question is, what forces act on the neutron? The most likely model for the neutron seems to me, on wave mechanical grounds, to be the assumption that the motionless neutron is a magnetic dipole with a certain magnetic moment µ (the bearer of this letter can supply details). The experiments demand that the ionizing power of such a neutron cannot exceed that of a gamma ray, and therefore µ probably cannot be greater than e (10-13cm). [e is the charge of the electron]. At the moment I do not dare to publish anything about this idea, so I first turn trustingly to you, dear radioactive friends, with the question: how could such a neutron be experimentally identified if it possessed about the same penetrating power as a gamma ray or perhaps 10 times greater penetrating power? I admit that my way out may look rather improbable at first since if the neutron existed it would have been seen long ago. But nothing ventured, nothing gained. The gravity of the situation with the continuous beta spectrum was illuminated by a remark by my distinguished predecessor in office, Mr. DeBye, who recently said to me in Brussels, "Oh, that’s a problem like the new taxes; one had best not think about it at all." So one ought to discuss seriously any way that may lead to salvation. Well, dear radioactive friends, weigh it and pass sentence! Unfortunately, I cannot appear personally in Tubingen, for I cannot get away from Zurich on account of a ball, which is held here on the night of December 6-7 With best regards to you and to Mr. Baek, Your most obedient servant, W. Pauli

18. *The neutrino triumphant 1932 Chadwick discovers the neutron. Anderson discovers the positron. First particle accelerator built. 1933 Solvay congress. The neutron has been renamed neutrino by Fermi, the neutron had entered the nuclear pantheon. The modern idea of nuclear structure has been established. 1933 Two months later Fermi publishes his theory of beta decay.

19. Schrodinger, Erwin; Joliot-Curie, Irene; Bohr, Niels Henrik David; Ioffe, Abram Fedorovich; Curie, Marie; Langevin, Paul; Richardson, Owen Willams; Rutherford, Ernest; Broglie, Maurice de; Broglie, Louis de; Meitner, Lise; Chadwick, James, Sir; Perrin, Francis Henri Jean Siegfried; Joliot-Curie, Frederic; Heisenberg, Werner; Kramers, Hendrik Anthony; Fermi, Enrico; Walton, Ernest Thomas Sinton; Dirac, Paul Adrien Maurice; Debye, Peter Josef William; Mott, Nevill Francis, Sir; Cabrera, Blas Juan Jose; Gamow, George; Bothe, Walther Wilhelm Georg; Blackett, Patrick Maynard Stuart; Bauer, Edmond H.; Pauli, Wolfgang; Herzen, E.; Cockcroft, John Douglas, Sir; Peierls, Rudolf Ernst, Sir; Piccard, Auguste; Lawrence, Ernest Orlando; Rosenfeld, Leon;

20. Conservation laws: what you can do with nothing This marks the last time (to date) that the conservation laws of energy and momentum were seriously considered to be problematic. Energy conservation  the universe has no preferred time. Momentum conservation  the universe has no place Angular momentum conservation  the universe has no preferred direction Something going out Something must be coming in 1972 Neutral currents

21. The W is discovered before the Z Carlo Rubbia Detector Simon Van der Meer Accelerator

22. The W is discovered before the Z p p Collisions between protons and anti-protons q q W Mass 80*proton Charge +1 or -1 W produced at 10 times the rate of Z’s But how to detect them? Z Mass 90*proton Charge 0

23. The W is discovered before the Z  e+ W 10 times as many W’s as Z’s But how do you detect them. Z e+ e-

24. Finding the Z Find electron-positron pairs e+e- Or positive muon/negative muon pairs White tracks straight, not bending in the magnetic field so high momentum. White rectangles, lots of energy in the electron detectors

25. How to spot the Z Collide beams of particles and anti-particles. E1, p1, E2. p2 q q Total energy is E = (E1 + E2) total momentum p = (p1 + p2) Look for a positron and an electron. From their momentum (and knowing their mass) if they came from the decay of a single particle we can calculate its mass. So we can reject electrons or pairs of electrons which are nothing to so with the Z and if there is anything left we have discovered the Z

26. Z Here we see a beautiful peak on top of a smooth background. Not UA1, but D0 a similar experiment

27. How to spot the W Collide beams of particles and anti-particles. E1, p1, E2. p2 q q Total energy is E = (E1 + E2) total momentum p = (p1 + p2) Look for a positron or an electron. But there is nothing else – we have no way of telling if the electron came from a W or some other particle

28. How to spot the W Lots of momentum not visible this way.. Particle with lots of momentum. Add up all the momenta of all the particles visible in the event. Momentum = 0, before the collision. Must be zero after. Calculate the momentum needed to make it zero – “the missing momentum” The missing momentum is the momentum of the neutrino. Calculate the mass of a particle needed to produce an electron of the measured momentum and a neutrino with the missing momentum. We should see a W mass

29. Finding the W Red arrow – the high energy electron. Nothing high energy in the opposite direction

30. *Weighing the neutrino At the end point all the energy is given to the electron. But there must be neutrino (another conservation law). If the neutrino mass is zero – it may have as close to zero energy as you want If it has a mass the electron can never take all the energy. Katrin experiment

31. Weighing the Neutrino The Katrin experiment in Germany Being moved from construction site to experimental area. ”Katrin Journey” The Katrin spectrometer

32. Weighing the Neutrino It was built Deggendorf 400km from where the experiment is running in Karlsruhe It travelled 9000 km Route of the spectrometer Neutrino mass m < 2 eV Electron = 511,000 eV

33. LEP - CERN Collided electrons and positrons to produce Z particles. OPAL, ALEPH, DELPHI and L3

34. How to spot the Z at LEP Z Production e e Decay Z

35. Lots of momentum not visible this way.. Lots of momentum not visible this way.. photon In some events a photon is radiated along the beam direction. Z e e This is the sort of area where a photon might be seen. A photon and nothing else, means a lot of energy has disappeared.

36. 1990 OPAL publishes a paper counting the number of decays of Z to two neutrinos

37. LHC Been taking data for nearly 10 years. When I first gave this talk I said Sometime in the next few years the headline ”Supersymmetry is discovered at the LHC” Will hit the evening news

38. LHC and supersymmetry I explained Supersymmetric particle A decays to a shower of conventional particles (measurable) and the lightest super symmetric particle. The Lightest supersymmetric particle is even less reactive than the neutrino so it disappears carrying energy and momentum. The detector which completely surrounds the interaction point picks up all the normal particle energy and so we can measure the missing energy and momentum.

39. LHC and supersymmetry And concluded We will calculate the mass with the conventional particles and the missing momentum from the supersymmetric particle and a peak will emerge. Neutrinos form a background to this process, which will make the detection a delicate process. We have seen nothing –

40. LHC and supersymmetry Not for want of trying. In 2017 CMS published 178 papers and contributions to conferences, listing some of the ways we had looked and failed to find supersymmetry. Atlas will have produced a similar number of publications. This can be added to the 40 publications in which OPAL failed to find any sign of supersymmetry Where is supersymmetry? Atlas: Conference report 13 March. Last Pub Feb 9th CMS: Paper submitted 16 March. Last Pub Feb 12th, Jan 30th

41. Double beta decay Some nuclei beta decay to nuclei which themselves undergo beta decay. Such a process is called double beta decay. A  B + e-+  B  C + e-+  A  C + 2e-+ 2 MA > MB + me MB > MC + me Two beta decays

42. Double beta decay A  B + e-+  B  C + e-+  MA < MB + me MA > MC + 2me It can only occur if both decays happen simultaneously. Very unlikely – watch an atom for 100,000,000 times the lifetime of the universe until it decays. Or watch a ton of the material for a couple of seconds. Add up the energies of the two electrons and there will be some missing. Double beta decays

43. Neutrino induced Electron emission B  C + e-+  Feymann tells us we can move a particle across such an equation as long we replace it with its anti-particle  + B C + e- This doesn’t help unless a neutrino is its own anti-particle. Ettore Majorana suggest that particles exist which are their own anti-particle. Majorana particles. (Majoranons) He disappeared in mysterious circumstances in 1938 at the age of 32.

44. Are neutrinos Majoranons No Majorana particles are known, but the neutrino could be one. The results would be a double beta decay in which there were no neutrinos produced A  B + e-+   + B C + e- A  C + 2e- No neutrinos produced means all the energy will be shared between visible particles No missing Energy

45. Experiment NEMO Neutrino Ettore Majorana Observatory. Underground laboratory in France.

46. 90 years of neutrino physics • Pauli has trouble convincing people that in an event known to be beta decay, conserves energy due to an undetected particle • 202.. Physicists of the NEMO collaboration may say that the neutrino is a Majoranons if they see double beta decay with out missing energy. • An absence of an absence means something ….

47. Prologue 19th century Paris

48. The discovery of radioactivity • Antoine Cesar Becquerel – chair of physics created for him at the Museum of Natural History, Paris. • Main field thermoelectoricphenomena – also worked on luminescence. • Inventor of the differential galvonometer 1839 Paper on luminescence – A.C.B. Jean Baptiste Biot, and Alexandre Edmond Becquerel (19) third son of Antoine. A.E. Becquerel works on phosphorescent solids, including Uranium salts. Noted uranous salts are not phosphoresent. Uranyl are.

49. The discovery of radioactivity 1878 A.C.B. dies and A.E.B. inherits the professorship. Antoine Henri Becquerel, (AEBs second son) helps father. 1881 Antoine Henri Becquerel, (AEBs second son) helps father by preparing “very beautiful lamellas of potassium uranyl disulphate” to help his father’s study on phosphorescent. 1889 Henri elected to the Academie 1891 Henri inherits chair on the death of his father. 1896 Discovery of radioactivity Phosphoroscope

50. The discovery of radioactivity : postscript 1904 Jean Becquerel (AHB only son) starts publishing with his father 1908 Henri dies. Jean Becquerel inherits the chair! 1948 Jean retires – and the chair passes out of the family.