1 A. Bettini LSC, Padova University and INFN Subnuclear Physics in the 1970s 23-Feb-16 IFIC Valencia. 4-8 November 2013 Lecture 6 The 2 nd and 3 rd families Three neutrinos Tau November revolution Hidden beauty Reaching the top 2 A. Bettini LSC, Padova University and INFN Neutrino flavours 23-Feb-16 Neutrinos cannot be directly detected The charged lepton produced by the neutrino interaction in the detector identifies the neutrino flavour 3 A. Bettini LSC, Padova University and INFN Neutrino flavour CHANGES 23-Feb-16 In the last 15 years we learnt that neutrino change flavour, provided time (flight distance) is given them to do so Oscillations and flavour conversion in matter, prove that neutrinos, contrary to the Standard model have non-zero mass flavour states are superposition (mixing) of mass eigenstates 4 A. Bettini LSC, Padova University and INFN Electron and pion showers 23-Feb-16 electron pion Main difference in the nose Hadrons are produced much more frequently than leptons. Need discrimination power Detector should look at and enhance the difference 5 A. Bettini LSC, Padova University and INFN Signature of 23-Feb-16 muon = long, non interacting track The worlds first muon neutrino observation in a 12-foot hydrogen bubble chamber at Argonne. 6 A. Bettini LSC, Padova University and INFN Tau 23-Feb-16 HL/ lifetime is short, 0.29 ps O(100 m) length Nagoya Emulsion Cloud Chamber 7 A. Bettini LSC, Padova University and INFN The 2 nd and 3 rd lepton family 23-Feb J. Street and E. Stevenson; C. Anderson and S. Neddermeyer: discover the penetrating component of cosmic rays (the ) M. Conversi, E. Pancini, O. Piccioni: discover in cosmic rays the leptonic character of the (I. I. Rabi will later ask: Who ordered that?) F. Reines and C. Cowan. Discovery of the (electron-)anti neutrino with a reactor M. Schwartz, L. Lederman, J. Steinberger et al. discover the muon-neutrino at BNL AGS proton accelerator A. Zichichi proposal at CERN PS of the PAPLEP (Proton-AntiProton into LEpton Pairs) initiating the search for the 3 rd sequential lepton family, a replica of the first two the Heavy Lepton and its neutrino Searching for acoplanar lepton pairs of opposite charges 8 A. Bettini LSC, Padova University and INFN PAPLEP. The two-arm electron & muon spectrometer 23-Feb-16 Experimental challenges Large solid angle Discriminate (rare) electrons from the (dominant) hadrons Early shower development [CERN Nuclear Physics Division, June 27, 1963] Discriminate (rare) muon from (dominant) hadrons Fe hadron absorber Punch through [ Nuovo Cimento 35 (1965) 759] Massam, T. A new electron detector with high rejection power against pions. Nuovo Cimento 39 (1965) 464. See also CERN Nuclear Physics Division, June 27, 1963 9 A. Bettini LSC, Padova University and INFN PAPLEP. The two-arm electron & muon spectrometer 23-Feb-16 Pb camera bea m Lepton-Antilepton Pairs = e + e , + , e 1963 10 A. Bettini LSC, Padova University and INFN PAPLEP. The two-arm electron & muon spectrometer 23-Feb-16 11 A. Bettini LSC, Padova University and INFN Preshower 23-Feb-16 Accurately sample the nose of the shower Control early development with Z and thicknesses of detector elements Combine visual and non-visual approaches (each 10 2 rejection) Tracking with thin plate (Al) spark chambers Energy sampling with Pb-scintillator sandwiches e/ separation 4 x 10 4 CERN Nuclear Physics Division, June 27, 1963 Nuov Cim 29 (1965) 464 Heavy lepton not found Final paper N. Cim. 40 (1965) 690 reported the discovery of the time- like nucleon form factor 12 A. Bettini LSC, Padova University and INFN The search at ADONE 23-Feb Zichichi proposes the search for the HL at the ADONE e + e collider at Frascati [M. Bernardini et al. INFN/AE-67/3, 20 March 1967] Electron and positrons, differently from protons and antiprotons are pointlike. May give a better chance 13 A. Bettini LSC, Padova University and INFN The limit 23-Feb-16 The maximum ADONE energy was however s=3 GeV, below the threshold for production s=3.554 GeV A lower limit for the HL mass was obtained [V. Alles Borelli et al. Lett. Nuov. Cim. 4 (1970) 1156] Simplfied from Nuovo Cimento 17A (1973) 383 HL is here 14 A. Bettini LSC, Padova University and INFN MARK SPEAR e + e s=6 GeV 23-Feb-16 MARK I 1974 The general purpose detector The search for the 3 rd lepton looking for e pairs was repeated by Perl et al. Poor lepton identification Electron = 4 x min. ionisation in Pb- scintillator detectors 18% of hadrons in the electron sample Muon= penetration of 20 cm of Fe (1.7l) 20% of hadrons in the muon sample Analysis had to rely statistically on acoplanarity selection M. L. Perl et al. Phys. Rev. Lett. 35 (1975) Evidence for anomalous lepton production in e + e annihilation We have found 64 events of the form for which we have no conventional explanation 15 A. Bettini LSC, Padova University and INFN MARK I improve and e discrimination 23-Feb February 2016A. Bettini. Padova University and INFN; LSC 15 Summer Add thick absorbers to filter muons added in the upper part Add Pb glass wall (A. Galtieri) M. L. Perl et al. Phys. Lett. 63B (1976) 466. Properties of anomalous e events produced in e + e annihilation We present the properties of 105 events of the form The simplest hypothesis compatible with all data is that these events come from the production of a pair of heavy leptons, the mass of the lepton being in the range 1.6 to 2.0 GeV 1976? HL is called from , the third (P. Rapidis) PLUTO and DESY confirm the observation 16 A. Bettini LSC, Padova University and INFN Fermilab Feb-16 17 A. Bettini LSC, Padova University and INFN Discovery of 23-Feb-16 www-donut.fnal.gov/web pages/ K. Niwa et al. DONUT-E872 at Fermilab 18 A. Bettini LSC, Padova University and INFN GIM 23-Feb-16 Existence and properties of charmed hadrons was predicted on theoretical grounds GIM mechanism: Glashow, Iliopoulos and Maiani introduced a new quark flavour, charm, to explain the suppression of weak neutral current processes between quarks of different flavour, which otherwise should have been orders of magnitude larger than observed t Hooft showed that EW theory can be renormalised (infinite terms can be subtracted in a coherent manner) if the sum of the electric charged of the fermions is zero With 4 leptons (e , e ), ( , ) and 3 quark (d,u) and s, each with 3 colours (1973) Need another quark, in three colours, with charge 2/3, similar to u Charmed particles should have been masses 2 GeV produced in pair short lifetimes 0.1 ps and should decay more often in strange final states than not But in 1974, charm, strongly wanted by theorists, had not been found. Or at least so it was thought in the West 19 A. Bettini LSC, Padova University and INFN Cabibbo mixing Analysing the decay rates of the strange hyperons and mesons shows that the decays with S = 1 are suppressed by an order of magnitude to those with S=0 In addition the decay rate of the n is suppressed a bit with respect to the Cabibbo showed that universality is recovered assuming that the quarks that couple to the W are not in the basis d and s, but in one rotated by an angle C W couples to d = d cos C + s sin C cos C = sin C = S=0 S|=1 C = 12.8 20 A. Bettini LSC, Padova University and INFN Strangness changing neutral currents Immediate consequence of the Cabibbo theory is the existence of the neutral current should have similar rates. But strangness changing neutral currents are strongly suppressed Consequently the two decays 21 A. Bettini LSC, Padova University and INFN GIM mechanism d = d cos C + s sin C is a member of the doublet In 1970 Glashow, Iliopoulos and Maiani (GIM) suggested the existance of a new flavour called charm that makes a doublet with s (the state ortogonal to d) GIM shown that to be true at all orders 2 nd is Now there are two terms Summing The strangeness changing neutral currents are cancelled, at the 1 st order. 22 A. Bettini LSC, Padova University and INFN The Japanese perspective 23-Feb-16 The true ones 1956 Sakata model. Fundamental particles are p, n and Parity violation. VA structure 1959 Gamba, Marshak and Okubo baryon-lepton fundamental symmetry (, e, ) - (p, n, ) 1960 Maki et al. Nagoya model. Ur matter B + and 1962 Second neutrino, lepton-baryon symmetry lost Try to recover: Katayama et al. and Maki et al. advanced two hypothesis 1. are not the "true" neutrinos, but linear mixtures, of them 2. only 2, for not explained reasons, couples to the B + Maki et al. mentioned also the possibility of transmutation between neutrino flavours Katayama et al. advanced the hypothesis that a 4 th Sakaton might exist 1962 Lipkin et al. notice that the observation of at rest falsifies Sakata model N.B. If it were true neutrino and quark (Cabibbo) mixing angles would have to be equal 23 A. Bettini LSC, Padova University and INFN Discovery of charm 23-Feb-16 The emulsion technique, abandoned in the West had made much progress in Japan Niu and collaborators developed in Nagoya theemulsion chamber, made of two main parts 1.several emulsion layers perpendicular to tracks 2. sandwitch of emulsions and Pb sheets (t=1 mm) identification of e, measure enrgy Measure of momenta in the TeV region via multiple scattering High altitudes exposures with balloons Develop automatic scanning and measurement devices Observation of one event produced by a TeV- energy primary Associated production of two particles decaying in several 10 14 s weak decay Tracks OB, BB and are coplanar. Particle h decaying at B is in a hadronic shower is a hadron; mass m x = GeV depending on the nature of BB) With this mass cannot be strange Final confirmation that it has the characteristics of charm. Research was intensified. By 1975 a dozen of events were found But in the West the discovery was ignored 24 A. Bettini LSC, Padova University and INFN Discovery of the J 23-Feb Sam Ting and coll. protonsincrotron AGS at BNL: spctrometer to search for heavy photons, particles with J P = 1, narrow, decaying in e + e through the reaction p+N e + e + X (X = anything) Two arm spectrometer. Each at the production angle i accepting momentum p i (i=1,2). Mass of the pair to decouple the and p magnet deflect in the vertical plane range of search in m variable, by varying acceptance in p 1 and p 2 e + e are produced in EM processes. ee / >10 8 Threshold Cherenkov sees only e, not , K. knok-on electron produced in the first one are bent out by B and do not reach the second calorimeters give shower profile must cope with high flux protons/s 25 A. Bettini LSC, Padova University and INFN Discovery of the J 23-Feb-16 The resonance peak at m(e + e )=3100 MeV is extremely narrow, narrower than the experimental resolution < 5 MeV Cannot be understood if only u, d and s exist The decay in e + e , through a photon J PC = 1 26 A. Bettini LSC, Padova University and INFN Discovery of and 23-Feb-16 Richter and collaborators observed the resonance at SPEAR contemporarily and independently, and called it 27 A. Bettini LSC, Padova University and INFN 23-Feb-16 The systematic search for more narrow resonances followed 10 days after the second (and last) was found at M=3686 MeV, the 28 A. Bettini LSC, Padova University and INFN Open charm 23-Feb-16 The Mark I detector started the search of the charmed pseudoscalar mesons at s=4.02 GeV in 1976, after having improved its K to discrimination ability, in the channels The mesons appear as resonances in the final state. Neutral D were observed decaying in the final states Mass =1865 MeV, width < experimental resolution The charged D-mesons were observed in the channels No resonance in the channels Mass =1869 MeV 29 A. Bettini LSC, Padova University and INFN Hidden and open charm 23-Feb-16 (3100) and (3686) are very narrow. Why? Masses >> many more open decay channels width should be large (3100) and (3686) contain a charm antcharm pair In spectroscopic notation are 1 3 S 1 and 2 3 S 1 They would like to decay in charmed mesons, but this is not energetically possible. 2 m D = 3730 MeV; 2 m D = 3738 MeV cfr (3770) on are wide 30 A. Bettini LSC, Padova University and INFN The two arms muon spectrometer 23-Feb-16 When the new proton accelerator became operational at Fermilab, in 1972, the Columbia- Fermilab-Stony Brook submitted a proposal to search for new heavy vector bosons with a single arm lepton spectrometer, using a combination of magnetic measurement and lead-glass photon detectors to identify electrons with a pion contamination of < Such rejection is needed when only one particle is involved. Lederman in the Nobel lecture says: The single-lepton effects turned out to be relatively unfruitful, and the originally proposed pair experiment got underway in In a series of runs the number of events with pair masses above 4 GeV gradually increased and eventually grew to a few hundred... The group was learning how to do those difficult experiments. In early 1977, the key to a vastly improved dilepton experiment was finally discovered. The senior Ph. D.s on the collaboration, Steve Herb, Walter Innes, Charles Brown, and John Yoh, constituted a rare combination of experience, energy, and insight. A new rearrangement of target, shielding, and detector elements concentrated on muon pairs but with hadronic absorption being carried out in beryllium, actually 30 feet of beryllium. The decreased multiple scattering of the surviving muons reduced the mass resolution to 2%, a respectable improvement over the % of the 1968 BNL experiment. The filtering of all hadrons permitted over 1000 times as many protons to hit the target as compared to open geometry. Recall that this kind of observation can call on as many protons as the detector can stand,... Muon-ness was certified before and after bending in iron toroids to redetermine the muon momentum and discourage punchthroughs When the new proton accelerator became operational at Fermilab, in 1972, the Columbia- Fermilab-Stony Brook submitted a proposal to search for new heavy vector bosons with a single arm lepton spectrometer, using a combination of magnetic measurement and lead-glass photon detectors to identify electrons with a pion contamination of < Such rejection is needed when only one particle is involved. Lederman in the Nobel lecture says: The single-lepton effects turned out to be relatively unfruitful, and the originally proposed pair experiment got underway in In a series of runs the number of events with pair masses above 4 GeV gradually increased and eventually grew to a few hundred... The group was learning how to do those difficult experiments. In early 1977, the key to a vastly improved dilepton experiment was finally discovered. The senior Ph. D.s on the collaboration, Steve Herb, Walter Innes, Charles Brown, and John Yoh, constituted a rare combination of experience, energy, and insight. A new rearrangement of target, shielding, and detector elements concentrated on muon pairs but with hadronic absorption being carried out in beryllium, actually 30 feet of beryllium. The decreased multiple scattering of the surviving muons reduced the mass resolution to 2%, a respectable improvement over the % of the 1968 BNL experiment. The filtering of all hadrons permitted over 1000 times as many protons to hit the target as compared to open geometry. Recall that this kind of observation can call on as many protons as the detector can stand,... Muon-ness was certified before and after bending in iron toroids to redetermine the muon momentum and discourage punchthroughs 31 A. Bettini LSC, Padova University and INFN The two arms muon spectrometer 23-Feb-16 Fermilab 1977 32 A. Bettini LSC, Padova University and INFN The Ys and the 5 th quark 23-Feb-16 By September, with 30,000 events, the enhancement was resolved into three clearly separated peaks, the third peak being a well-defined shoulder. See These states were called , , Simplest assumption J PC =1 In a month of data taking in the spring of 1977, some 7000 pairs were recorded with masses greater than 4 GeV and a curious, asymmetric, and wide bump appeared to interrupt the Drell-Yan continuum near 9.5 GeV 33 A. Bettini LSC, Padova University and INFN The s and the 5 th quark 23-Feb-16 The are beauty-antibeauty bound states observed at the e + e colliders at DESY (Hamburg) and afterward at Cornell J PC =1 , I=0. They are 3 S 1 with principal quantum number n=1, 2, 3 Cannot decay, for energy conservation, in states with explicit beuaty, hence they are narrow 34 A. Bettini LSC, Padova University and INFN Top 23-Feb-16 Searched at hadrons colliders for more than a decennim =173 GeV Difficult due to its very large mass m t =173 GeV Need CoM energy > 400 GeV In a collision pp at s = 2 TeV a top antitop pair is produced every In a collision pp at s = 2 TeV a top antitop pair is produced every collisions Lifetime