Science Café April 18, Charm in China. Frederick A. Harris University of Hawaii

Transcription

1 Science Café April 18, 2017 Charm in China Frederick A. Harris University of Hawaii 1

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4 OUTLINE Introduction to quarks and particles with charm Original era of discovery BEPC/BES beginnings and the US-SLAC connection BEPCII/BESIII New era of discovery: mysterious XYZ states BESIII does XYZ Where are we? Big science in China now Summary IHEP 4

5 Charm in China This kind of charm? No! Sorry 5

6 Introduction to Quarks and Particles with Charm Lijiang, China 6

7 What are we made of? Sugar and spice and all things nice Snips and snails and puppy-dog tails? A less poetic picture: H 2 O molecule Oxygen atom proton 7

8 Standard Model Standard Model particles are made of quarks, leptons, the force carriers and Higgs. Visible matter. p = uud n = udd π + = ud + Higgs particle Quarks have fractional charge, mass, spin, and color. The u-quark is the lightest, and the t-quark is the heaviest at about 180 times that of the proton. 8

9 Introduction to Charmonium J PC Charmonium is one of the simplest bound states of strong force. Classify using J PC. Quarks have spin. Can add or cancel (S). Can have angular momentum (L). Total angular momentum (J = L + S) P -Parity, C -Charge parity. Potential models can predict masses of undiscovered states. 9

10 What else can we do with charmed quarks? Open Charm Charmed mesons: c u c d c s D o D + D + s Plus anti-particles and many excited versions. Charmed baryons: d c u Plus anti-particles and many excited versions. Λ + c 10

11 Charmonium - original era of discovery West Lake, Hangzhou. China 11

12 Original Era of Discovery The charm quark was predicted by Glashow, Iliopolis, and Maiani in 1970 in order to explain why there were no flavor changing neutral currents (K 0 L μ + μ - ). Known as the GIM mechanism. On Nov. 11, 1974, Burt Richter (SLAC) announced the discovery of the ψ and Sam Ting (Brookhaven) announced the discovery of the J. J/ψ Discovery The November Revolution Sam Ting with few hundred J/ψ s 12

13 The November Revolution: J/ψ Discovery The J/ψ with a mass of GeV was soon interpreted as being made up of a c and a c quark. They received the Nobel Prize in 1976 for their discovery. The discovery led physicists to finally take quarks seriously. Phys. Rev. Lett. 33, 1406 (1974). 13

14 Original Era of Discovery Discovery at SLAC of the Ψ (2S) Phys. Rev. Lett. 33, 1453 (1974). 14

15 Original Era of Discovery Discovery at SLAC of the biggest Ψ (2S) decay mode. Phys. Rev. Lett.34, 1181 (1975). 15

16 Original Era of Discovery And many more states discovered: γ Phys. Rev. Lett. 45, 1150 (1980) 16

17 BEPC/BES beginnings and the US-SLAC connection 17 Beijing, China

18 BEPC/BES beginnings and the US-SLAC connection After long turbulent period, end of Ching dynasty, founding of Republic of China (1912) warlords, nationalists, communists ( ) Japanese invasion of Manchuria and WWII ( ) Founding of People s Republic of China, Mao Zedong (1949) China begins to open up: Nixon visit (1972) Richard Nixon meets Mao Zedong, Feb (from White House Photo Office ( ) via Wikipedia) The Chairman Dances by John Adams 18

19 BEPC/BES beginnings and the US-SLAC connection Also scientifically - not self reliance and hard struggle. Chinese physicists visit US to consult on future major facility (1972). Return to China with idea of GeV proton accelerator. Pief Panofsky invited to visit China, suggests e + e - collider better choice (1976). Cultural revolution ( ) ends; Deng Xiaoping takes over. Zhang Wenyu visits SLAC in 1972 (from Panofsky on Physics, Politics, and Peace) 19

20 BEPC/BES beginnings and the US-SLAC connection Carter and Deng sign a United States China agreement on Cooperation in Science and Technology (1979) Joint Committee on Cooperation in High Energy Physics established (1979). From Across the Ocean, Institute of High Energy Physics, Chinese Academy of Science First US/PRC Joint Committee meeting, June 1979 T.D. Lee and Pief Panofsky were founding members and attended over 25 years. 20

21 BEPC/BES beginnings and the US-SLAC connection Wen Jiabao US/PRC Joint Committee meeting 25 th Anniversary June

22 BEPC/BES beginnings and the US-SLAC connection Chinese government agrees to sponsor construction of Beijing Electron Positron Collider (BEPC/BES). 30 engineers and physicists come to SLAC in 1982 to make preliminary design. From Jean Deken, SLAC Archives and History Office 22

23 BEPC/BES beginnings and the US-SLAC connection Construction begins (1984). Cooperation with SLAC continues. First collisions, Oct. 16, 1988 Inaugural celebration, Oct. 24, Deng at ground breaking (Oct. 7, 1984) TD Lee and Deng on tour of collider, Oct. 24,

24 BEPC/BES beginnings and the US-SLAC connection 10 M J/Ψ events accumulated (May 1991). American scientists join in 1991 to measure τmass: (Boston University, Caltech, UC Irvine, Colorado State, MIT, SLAC, SSC, University of Texas at Dallas, and University of Washington). BESI detector τthreshold scan Nov. 91 Jan. 92 e e τ + τ 24

25 BEPC/BES beginnings and the US-SLAC connection Why so interesting? Mass ofτlepton Universality: G τ eυυ = G μ eυυ B τ e l l G G = G τ eυυ μ eυυ 2 l eυυ 192π 2 = 3 Before BES: m m m μ τ 5 l G coupling constant τ - lifetime B - branching fraction m - mass 5 l = e, μ, orτ B B e τ e μ τ τ μ τ /c 2 25

26 BEPC/BES beginnings and the US-SLAC connection /c 2 /c 2 26

27 BEPC/BES beginnings and the US-SLAC connection Mass ofτlepton Peeking ahead to BESIII Analysis done primarily by our University of Hawaii BESIII group. UH joined BES in 1994! /c 2 27

28 BEPCII/BESIII Beijing 28

29 Beijing Electron Positron Collider (BEPCII) Design luminosity: 1 x cm -2 s -1 29

30 BEPCII: a high luminosity double ring collider Beam energy: GeV Luminosity: cm -2 s -1 No. of bunches: 93 Total current: 0.91 A Circumference: 237 m 22 mrad crossing angle SC RF Use many bunches and SC mini-beta. Beam magnets 30

31 BESIII Detector Magnet Yoke Time of Flight Be beam pipe 1 T SC magnet Muon Counter 1 m Drift Chamber CsI(Tl) calorimeter Int. J. Mod. Phys. A24, 377 (2009) 31 NIM A614, 345 (2010)

32 Physics of tau charm region An important measurement at an e + e - collider is the cross section for e + e - hadrons, σ(e + e - hadrons), as a function of the energy. + σ ( e e hadrons) Often this is given as a ratio: R = + + σ ( e e μ μ ) BES E (GeV) 32

33 Physics of tau charm region Charmonium: cc BEPCII can study the lighter quarks (u, d, c, and s) and the leptons. τ charm factory Nobel prize threshold for τ pairs open charm XYZ states Λ c Λ c E (GeV) Very rich and interesting energy region. 33

34 BESIII Data Sets J/ψ ψ 1.3x x fb fb fb fb -1 ψ(3770) 2.9 fb fb points R Scan fb fb -1 E (GeV) World largest/unique samples from e + e - collision : J/ψ, ψ(2s), ψ(3770), Y(4260) 34

35 US (6) Univ. of Hawaii Univ. of Washington Carnegie Mellon Univ. Univ. of Minnesota Univ. of Rochester Univ. of Indiana The BESIII Collaboration Europe (13) Germany: Univ. of Bochum, Univ. of Giessen, GSI Univ. of Johannes Gutenberg Helmholtz Ins. In Mainz Russia: JINR Dubna; BINP Novosibirsk Italy: Univ. of Torino,Frascati Lab, Ferrara Univ. Netherland:KVI/Univ. of Groningen Sweden: Uppsala Univ. Turkey: Turkey Accelerator Center Pakistan (2) Univ. of Punjab COMSAT CIIT ~430 members 54 institutions from 10 countries more than 30 publications per year Very successful international collaboration China(29) Korea (1) Seoul Nat. Univ. Japan (1) Tokyo Univ. IHEP, CCAST, GUCAS, Shandong Univ., Univ. of Sci. and Tech. of China Zhejiang Univ., Huangshan Coll. Huazhong Normal Univ., Wuhan Univ. Zhengzhou Univ., Henan Normal Univ. Peking Univ., Tsinghua Univ., Zhongshan Univ.,Nankai Univ., Beihang Univ. Shanxi Univ., Sichuan Univ., Univ. of South China Hunan Univ., Liaoning Univ. Nanjing Univ., Nanjing Normal Univ. Guangxi Normal Univ., Guangxi Univ. Suzhou Univ., Hangzhou Normal Univ. Lanzhou Univ., Henan Sci. and Tech. Univ

36 The New Era of Discovery XYZ States and Y(4260) Jiuzhaigou 4/20/2017 ICHEP

37 XYZ States Many charmonium states predicted by potential models and LQCD. Many have been found. XYZ states not predicted by potential models. What are they? 37

38 XYZ States (EPJ C71, 1534 (2011)) First XYZ 38

39 XYZ States (EPJ C71, 1534 (2011)) Most discoveries by B factory experiments. Produced indirectly by ISR production or B decay. Many states not confirmed. Still a puzzle after 10 years. Much theoretical interest. 39

40 Important Processes e + e - annihilation (BESIII) e + c B decay (B factories) ISR (B factories and BESIII) e + e - radiate one or more photons. Measure σ over range of energies. B b q e - e - e + c W c c c s q K (*) e - c High luminosities at B factories allow use of ISR and 2 photon processes

41 Y(4260) BaBar, PRL 95, (2005) BaBar, PRD 86, (2012) Belle, PRL 99, (2007) Belle 41

42 BESIII does XYZ Three Gorges Yangtze River 42

43 U. of Indiana group convinced BESIII to take data on the Y(4260). On Dec. 14, 2012, BESIII began running with a CM energy of 4.26 GeV. Produce Y(4260) directly! Y(4260) BESIII Select e + e - π + π - J/Ψ, J/Ψ l + l - events events found. Cross section consistent with production of Y(4260). 43

44 Z c (3900) Plot M(π + J/Ψ) and M(π - J/Ψ) for each event. Find new particle with charge and a mass of 3900 MeV/c 2, the Z c (3900). e + e - π Z c (3900) π - (π + J/Ψ) +c.c. BESIII N(Z c (3900)) = 307 ± 48 M(Zc(3900)) = ( ± 3.6 ± 4.9) MeV/c 2 Suggestive of a state with more than just a c and c quark. (π + = ud, J/ψ = cc) Phys. Rev. Lett. 110, (2013) with more than 460 citations Was on top of Physics Highlights of

45 Z c (4020) BESIII has other Z c candidates and other decay modes BESIII e + + e - π + π - h c, h c γη c See narrow structure in π ± h c mass: e + e - π Z c (4020) π - (π + h c ) +c.c. M(Z c (4020)) = ± 0.8 ± 2.7 MeV/c 2 4/20/

46 Where are we? Yangtze River 4/20/

47 Theory: Theorists have been very busy, and many explanations have been offered for the X(3872), Y(4260), and now the Z c states: tetraquarks, molecular states (DD* bound state), hadrocharmonium, hybrid charmonium, etc. Molecules and other 4-quark states popular. u c c d Hadrocharmonium 47

48 Theory: Meson loops Initial Single Pion Emission Model (ISPE) 4/20/

49 Where are we? Do we understand XYZ s now? No agreed upon theory. There may be no universal explanation for XYZs. XYZ s are still a big puzzle. Experimentally most particles are mesons (q and anti-q) or baryons (3 quarks). Theoretically other combinations possible. But until now, no unambiguous candidates. Z c - good candidates for 4-quark states. Recently LHCB, found candidate for state with 5 quarks (pentaquark). There is still much to understand. 4/20/

50 Big Science in China at Present West Lake, Hangzhou. China 50

51 Big Science Projects China has come a long way since BESI. BEPCII and BESIII Shanghai Synchrotron Radiation Facility Experimental Advanced Superconducting Tokamak Daya Bay Reactor Neutrino Experiment Five Hundred Meter Spherical Telescope Square Kilometer Radio Telescope Array Large Hadron Collider Panda Experiment Chinese Space Station Mars project.. Beijing Shanghai Hefei Hong Kong Guizhou South Africa/ Australia Switzerland Germany 4/20/

52 Big Science Projects Being proposed: Circular Electron Positron Collider (CEPC) 32 mile circumference 120 GeV beam energy Data taking Study Higgs particle Super Proton Proton Collider (SPPC) 32 mile circumference 50 TeV beam energy Follows CEPC Search for new particles beyond standard model At present, China spends more on science than Europe. Organization for Economic Co-operation and Development (OECD) predicts that Chinese spending on science will overtake the US in /20/

53 Summary US-SLAC helped with the birth of modern science in China BEPCII/BESIII very successful: BESIII has many beautiful data sets at many energy points between 2 and 4.6 GeV. They allow a wide variety of physics topics to be pursued. BESIII has jumped head first into XYZ physics China has become a world leader in science 53

54 谢谢 谢谢 54

55 Backup Slides

56 Belle ( ) Experiments BESII ( ) e + e - CLEOc ( ) ( ) 4/20/

57 Experiments BESIII ( ) e + e - Belle II (2016? - ) Others: D0 CDF SND CMD3 LHCb ATLAS CMS Panda 57