Journey through the Standard Model The discovery of charm and beauty Giorgio Bellettini Contribution to the Duke symposium honoring Al Goshaw May 7. 2019 10/14/2019 G. Bellettini, Duke Symposium 2019

Why high energy accelerators? Accelerators make hard collisions between matter particles possible, which produce unstable subatomic particles that can be observed and studied in particle detectors. The larger the energy of the interaction, the larger the mass of new particles that can be produced: E = mc2. Collisions can be generated in head-on collisions between two beams running oppositely in the same ring, or with a beam hitting an external target. 10/14/2019 G. Bellettini, Duke Symposium 2019

Available energy in particle collisions In ring colliders the entire energy of the beams is avalable in the lab for creating new particles: Energy = 2Ebeam In fixed target collisions only the center of mass energy is available; Energy = √(2 EbeamMtarget) 10/14/2019 G. Bellettini, Duke Symposium 2019

A proton beam crossing a ”bubble chamber” 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 Ring colliders 10/14/2019 G. Bellettini, Duke Symposium 2019

How can the produced particles be identified? 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 A particle zoo in the 70`s In the early 70`s the large number of unstable particles were interpreted in the quark model as pairs (mesons) or triplets (barions) built out of three fermions named up, down, strange “quarks”, with positive or negative charges 2/3 or 1/3 of the electron charge. Quarks u and d were buried as triplets in protons or neutrons, and pairs of u, d, s built mesons. 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 The -pair spectrum of J. H. Christenson et al. P.R.L 25, 1523 (1970), Phys Rev D8,2016 (1973) In 1973 Leon Lederman and collaborators observed in inelastic proton collisions of the 28 GeV BNL proton beam an anomaly in the muon pair mass spectrum. 10/14/2019 G. Bellettini, Duke Symposium 2019

J. H. Christenson et al. after background subtraction The anomaly looked more significant after subtracting the large background (mostly accidentals). 10/14/2019 G. Bellettini, Duke Symposium 2019

The electron pair BNL spectrometer S.C.C. Ting who collaborated in that experiment felt that that spectrum deserved a closer look, and lead the construction of an e+e‾ spectrometer of good mass resolution. 10/14/2019 G. Bellettini, Duke Symposium 2019

Another strategy: e+e- colliders Lepton pairs were being studied also at ring colliders. Since 1968 electron-positron collisions were studied up to 3 GeV c.m.s. energy with the ADONE collider at Frascati and with the 8 GeV SPEAR collider at SLAC. Also the DORIS collider at DESY could run up to 5 GeV, but it was primarily shooting for higher energies. 10/14/2019 G. Bellettini, Duke Symposium 2019

e+e- colliders: ADONE at Frascati The design energy of ADONE, a ring of ⁓ 10 m radius, was 3.0 GeV. The typical operation energy was 2.8 GeV. 10/14/2019 G. Bellettini, Duke Symposium 2019

The Baryon-Antibaryon ADONE detector Four not-magnetic detectors with spark chambers and plastic scintillators were installed on ADONE in 1970. 10/14/2019 G. Bellettini, Duke Symposium 2019

e+e- colliders: SPEAR at SLAC With a ring radius of ~ 40 m. SPEAR could run from ~2.5 to ~8.0 GeV. 10/14/2019 G. Bellettini, Duke Symposium 2019

The Mark1 SPEAR detector MARK1 was the only detector on SPEAR. It emploied spark chambers in the magnetic field of a solenoid coaxial with the beams. 10/14/2019 G. Bellettini, Duke Symposium 2019

e+e- into hadrons in the quark model R= (e+e– hadrons)/(e+e– +–) = 3Qq2 = 2 for u, d, s quarks of 3 colors . 10/14/2019 G. Bellettini, Duke Symposium 2019

e+ e- annihilation into hadrons in 1973 R >>2 above 3 GeV was a surprise At ADONE the e+e- annihilation cross section into hadrons was decreasing with increasing energy, while at SPESR above 3 GeV it was increasing and the points at 3.2 and 3.4 GeV looked too high. In October 1974 a more accurate scan of the cross section was started there. SPEAR Adone 10/14/2019 G. Bellettini, Duke Symposium 2019

Announcing a discovery On November 11th the leader of the BNL group, Sam Ting, went to SLAC to visit Burt Richter, the leader of the Mark 1 group. They agreed to announce jointly the discovery of the new particle which was named  at Mark1 and J at BNL. That was felt as a revolution by the HEP community. 10/14/2019 G. Bellettini, Duke Symposium 2019

The J particle Phys. Rev. Lett. 33, 1404 (1974) The J discovery mass spectrum shown in public at BNL on November 11, 1974. J. J. Aubert, U. Becker, P. J. Biggs, J. Burger, M. Chen, G. Everhart, P. Goldhagen, J. Leong, T. McCorriston, T. G. Rhoades, M. Rohde, Samuel C. C. Ting, Sau Lan Wu, and Y. Y. Lee 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 Samuel C. C. Ting The leader of the BNL group was Samuel C. C. Ting, Noble prize for Physics in 1976 for the J discovery. 10/14/2019 G. Bellettini, Duke Symposium 2019

The  particle Phys. Rev. Lett. 33, 1406 (1974) 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 Burton Richter The SPEAR collaboration was headed by Burton Richter, Nobel Prize for Physics in 1976 for the ψ discovery. 10/14/2019 G. Bellettini, Duke Symposium 2019

The revolution at Frascati The rumor was around since a while. Unfortunately the rumor did not reach Frascati early enough. A peak in the  pair mass spectrum was evident in Ting`s data since summer 1974 but it was carefully kept secret in the hope to understand first what the new particle was. In the week of October 13th a number of BNL physicists were informed about it but were not allowed to see the data. Melvin Schwartz, a distinguished Stanford physicist, heard the rumor and on October 22nd went to BNL to interrogate the group. He was unable to get a confirmation. 10/14/2019 G. Bellettini, Duke Symposium 2019

A telephone call to G.B. by night on November 11th, 1974 From an excited Sau Lan Wu calling GB from BNL: “We have found a new particle!” “What is so special about it?” “It is very heavy and very narrow! It decays into e+e– ” “How heavy?” “About 3.1 GeV.” In the conversation it was soon understood that the Adone energy could possibly be stretched to reach 3.1 GeV. 10/14/2019 G. Bellettini, Duke Symposium 2019

Knowing the precise mass value was important The mass measurement of BNL was not precise enough to allow Adone to find promptly the new particle by concentrating on a small mass range. Mario Greco, a Frascati theorist, was at SLAC. He managed to know the Mark1 mass which was precise to a few MeV and called me. A scan in steps of 1 MeV started at Adone already on November 12th . 10/14/2019 G. Bellettini, Duke Symposium 2019

The Frascati result C.Bacci et al., Phys.Rev.Lett. 33, 1408 (1974) The discovery was easily confirmed in a few days. This plot is from the  group.The other Frascati groups reported a similar evidence. 10/14/2019 G. Bellettini, Duke Symposium 2019

Frascati: 7 days for getting a PRL paper Info received by G.B. from S. L. Wu: night of November 11th Resonance found at ADONE: November 13th Data collected, paper written: November 13th to 17th Paper “phoned” by G.B. to S. L. Wu: night of November 17th Paper received by P.R.L: November 18th. The confirmation paper by Frascati appeared third after the BNL and SLAC papers, in the same PRL issue of December the 2nd. 10/14/2019 G. Bellettini, Duke Symposium 2019

Could the Italians do better? (translated from Italian): Giorgio Salvini, in “Maestri ed Allievi della Fisica Italiana del Novecento”, by Luisa Bonolis, Ed. La Goliardica Pavese SRL, 2008, page 127 “…there was an understandable bitterness…However I do not feel like associating this bitterness to a sense of guilt…nobody, I say nobody could suspect that a few steps beyond the 3 GeV limit there was an Eldorado waiting...” 10/14/2019 G. Bellettini, Duke Symposium 2019

Could I do better? (translated from Italian): Giorgiob, in “Storie di Uomini e Quarks”, by Carlo Bemporad and Luisa Bonolis, Ed. La Societa` Italiana di Fisica, 2010, page 25: “…Frascati did have a machine that could reach the J/ψ…we kept increasing the statistics at 2.8 GeV…the search for narrow resonances was made only after this earthquake…I was the Director and thus I was not innocent…you cannot imagine how many times I ate my fingers!” 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 Discovery of the ψ' Soon a very narrow ' with mass about 3.7 GeV was discovered by Mark1 in an energy scan. It was the first of several excited states of the . E = 3.7 GeV ψ' 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 The ψ' line 10/14/2019 G. Bellettini, Duke Symposium 2019

Charmonium states in ψ' decays Besides the fundamental ψ states of spin 1, charmonium states of different internal spin and orbital momentum were found studying radiative decays of members of the ψ family. 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 R = σhad /σμμ above the ψ' In addition to more ψ`s, several broad resonance above the ' were interpreted as unstable states of a “naked” charm quark of charge (+2/3)e combined with light u, d, s quarks. ψ''' '' 10/14/2019 G. Bellettini, Duke Symposium 2019

SPEAR picture of R without the `s The SPEAR scan could not be extended beyond 8 GeV 10/14/2019 G. Bellettini, Duke Symposium 2019

R between 3 and 5 GeV 40 years later 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 From 1 to 2 quark doublets Because of the discovery of the charmonium family and of the naked charm of charge 2/3e, the quark model was extended to include a doublet of charm-strange quarks with charges +2/3e, -1/3e, in addition to the up-down doublet. Would that be the end? 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 Fermilab in summer 1977 Fermilab offered an external proton beam of over 300 GeV where the BNL study of the muon pair mass spectrum could be extended well above 3 GeV. 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 The R288 spectrometers The Leon Lederman group proposed E288, an accurate measurement of muon pairs with two magnetic spectrometers. 10/14/2019 G. Bellettini, Duke Symposium 2019

The μ-pair spectrum above the ψ`s On June 30, 1977 a clear peak around 9.5 GeV was announced, with indications of more structures at higher mass. The analogy with the ψ was clear. The newly discovered Y particle was the bound state of a heavier ”beauty” quark-antiquark pair. 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 The b-bbar Υ family Other states of a positronium-like Υ family were soon found at e+e- colliders. With time, many “naked beauty” hadrons were also found in e+e events above the Υ mass. The study of the interactions of the b-quark is a wide field of continued great interest for particle physics. 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 Leon Max Lederman In 1988, after the discovery of the Y, Leon Lederman received the Nobel Prize for having discovered the muon- neutrino in 1962. 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 Conclusions The study of the “naked beauty” resonances proved that the b-quark has charge -1/3e, as for the lower term of a quark doublet. Did a third doublet exist? The hunt for the upper term of a third doublet, the “top” quark, started immediately, The construction of the Standard Model was advancing full steam. Let`s now hear about the rest! 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 SPARES 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 Bhabha scattering e+e–e+e– BCF e+e–e+e–  In the ADONE energy range Bhabha scattering depended on energy as expected in QED. e+e–e+e–  10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 e+e–+– / e+e–e+e– +–/e+e– BCF e+e–+– BCF Also e+e–+– depended on energy as expected in QED. 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 The Frascati paper Amazing spelling mistakes in the author list of the Frascati ψ paper. 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 MY OWN STORY My years at Frascati as the lab Director were years of great social turbulence. Pure research was under serious political attack. In 1976 an INFN lab charged for basic research was split from the existing CNEN lab. Out of the 820 employees of the original LNF, only 82 moved to INFN. The concern and confusion created by those attacks, ending with that traumatic split into two labs, contributed to reduce our attention to the anomalies of the hadronic cross sections. 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 Radiative ψ decays Some charmonium states found in radiative ψ decays. 10/14/2019 G. Bellettini, Duke Symposium 2019

Quantum numbers of the low-lying  states 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 γ spectrum at the ` Many charmonium states that cannot be produced directly in e+e‾ annihilation were easily discovered in ψ’ decays. 10/14/2019 G. Bellettini, Duke Symposium 2019

The computed charmonium states The masses of the charmonium states could be computed well in a non-relativistic theory, as appropriate for heavy quarks of about 1.4 GeV mass. 10/14/2019 G. Bellettini, Duke Symposium 2019

The  particle Phys. Rev. Lett. 33, 1406 (1974) e+ e- Multihadrons (fit assuming zero width) e+ e- e+ e- hadron pairs e+ e- SLAC-LBL J.E. Augustin et al,, Phys. Rev. Lett. 33, 1406, 1974 10/14/2019 G. Bellettini, Duke Symposium 2019

G. Bellettini, Duke Symposium 2019 The charmonium family Many more ψ states were found that were interpreted as quark-antiquark bound states, arranged in a positronium-like spectrum with different spin and orbital momentum. The chosen name “charm” was as given earlier to a proposed fourth quark by Bjorken and Glashow. 10/14/2019 G. Bellettini, Duke Symposium 2019

The hydrogen atom of QCD 10/14/2019 G. Bellettini, Duke Symposium 2019