Presentation is loading. Please wait.

Presentation is loading. Please wait.

1 发现 Z c (3900) -- BESIII实验粲偶素研究 -- Yuan Changzheng ( 苑 长 征 ) IHEP, Beijing 2013年4月18日.

Similar presentations


Presentation on theme: "1 发现 Z c (3900) -- BESIII实验粲偶素研究 -- Yuan Changzheng ( 苑 长 征 ) IHEP, Beijing 2013年4月18日."— Presentation transcript:

1 1 发现 Z c (3900) -- BESIII实验粲偶素研究 -- Yuan Changzheng ( 苑 长 征 ) IHEP, Beijing 2013年4月18日

2 2 子不语怪力乱神 Confucius did not talk about exotics, strong force, chaos, and mystery. 《论语 · 述而》

3 3 Outline Introduction [ 北京谱仪 / 粲偶素 ] Charmonium spectroscopy Charmoniumlike states What do we do at BESIII Summary

4 4 The Beijing Electron Positron Collider My office LINAC BEPC (Beijing electron- positron collider) BES detector Main entrance to IHEP Satellite view of IHEP, Beijing Founded: 1984, Ecm=2-5 GeV (BEPC): L peak =1.0x10 31 /cm 2 s 2008-now (BEPCII): L peak =6.5x10 32 /cm 2 s

5 5 BEPC II: BEPC II: Large crossing angle, double-ring RF IP Beam energy: GeV Luminosity: 1×10 33 cm -2 s -1 Optimum energy: 1.89 GeV Energy spread: 5.16 ×10 -4 No. of bunches: 93 Bunch length: 1.5 cm Total current: 0.91 A SR mode: 2.5 GeV Compton back-scattering for high precision beam energy measurement BESIII is here

6 6 BESIII Detector Be beam pipe SC magnet, 1T Magnet yoke MDC, 130  m 0.5% at 1 GeV/c CsI(Tl) calorimeter, 1 GeV TOF, 90ps RPC Total weight 730 ton, ~40,000 readout chnls, Data rate: 5kHz, 50Mb/s

7 7 BESIII Physics Programs B (looks like DD for D or charm physics) E (looks like cc for charmonium physics) S (for light hadron Spectroscopy) T (for tau physics, looks like a Roman number “III”) BESTBEST This is not a BESIII logo!

8 8 基本粒子(费米子)

9 9 Onia FORCES System Ground triplet state 1 3 S 1 (v/c) 2 Number of states below dissociation energy bindingdecay Name  (MeV) Mass (GeV)n3S1n3S1 all POSITRONIUM EM eeee Ortho- 5x10  ~ QUARKONIUM STRONGSTRONG STRONGSTRONG EMEM  uu,  dd  ~  ss  41.0 ~0.8 “1”“1”“2”“2” EMEM  cc J/  ~  bb  ~ weak  tt (3000.0)(350.) < Quarkonium is the bound state of quark and anti-quark by the gluon. Charmonium is charm anti-charm bound state!

10 10 Discovery of the J/ψ PRL33, 1404 (1974)PRL33, 1406 (1974)PRL33, 1408 (1974) BNL SLAC ADONE confirmed! “November Revolution of Particle Physics!” Charm quark was proposed in 1964, first application in 1970! Design: Max. Ecm~3 GeV!

11 11 Discovery of the  (2S) PRL33, 1453 (1974) SLAC Predictions of the charmonium spectroscopy Argument and Potential model PRL34, 365 (1975)PRL34, 369 (1975) From then on, there is a new field in HEP: Charmonium Physics.

12 12 粲偶素命名规则 n (2S+1) L J n radial quantum number S total spin of c & cbar L orbital angular momentum L = 0, 1, 2... correspond to S, P, D, … J = S + L P = (–1) L+1 parity C = (–1) L+S charge conj. Godfrey & Isgur, PRD32, 189 (1985) States below charm threshold are all observed now, still many missing states above charm threshold.

13 The P-wave spin-triplet  cJ 13 CBAL : PRD34, 711 (1986)

14 14 Most states from e + e - experiments + MK3, DM2, … old generation BESIII CLEOc

15 15 Charmonia study in e + e - annihilation Disadvantages: 1.Only J PC =1 -- can be formed directly 2.Resolution sometimes is not good Advantages: 1.Background small 2.Production rate high 3.All kinds of final states 4.Inclusive/exclusive BESIII A typical event in BES detector ψ(2S)  J/ψπ + π - J/ψ  e + e - J/ψ Sample in Million 58 ψ(2S) Sample in Million Hundreds of papers, hundreds of channels, thousands of measurements listed by the Particle Data Group in Earlier exp. not listed !

16 16 Initial States Radiation (ISR) The Y states should also appear in this plot (between 4.0 and 4.7 GeV!) From PDG } J PC = 1 --  ’,  ’’, Y…

17 17 Charmonia study in B decays Advantages: Free gift from B-factories Cabibbo favored B decays XYZ-particles

18 18 Potential models Cornell potential : V(r) = -4  S /3r + kr (库仑势 + 线性势) 解薛定谔方程  能级, 波函数 This is not QCD! But the model works well! Why?

19 19 Charmonium spectroscopy n (2S+1) L J n radial quantum number S total spin of c & cbar L orbital angular momentum L = 0, 1, 2... correspond to S, P, D, … J = S + L P = (–1) L+1 parity C = (–1) L+S charge conj. Godfrey & Isgur, PRD32, 189 (1985) States below charm threshold are all observed now, still many missing states above charm threshold. No much progress in last century!

20 20 Then we found lots of XYZ states X(3872) XYZ(3940) X(3915) X(4160) Y(4008) Y(4140) Y(4260) Y(4360) X(4350) Y(4660) X(3915) X(4160) Y(4008) Y(4140) Y(4260) Y(4360) X(4350) Y(4660) Z(4430) Z(4250) Z(4050) What are they ? Charmonium? Hybrid? Tetraquark? Molecule? … Not all XYZ states are charmonia! ? 特点:衰变产物中有粲偶素, 但很难轻易解释为粲偶素, 也叫类粲偶素( charmoniumlike )。

21 21 X(3872)      J/  PRD84, (2011) 711 fb -1 PRD 77, (2008) 413 fb -1 latest results B ±  XK ± B 0  XK 0 N s =93±  N s =9±5 2.3   M=M X(3872) -M D0D*0 = ± 0.32 MeV B ±  XK ± B 0  XK 0

22 22 What is X(3872)? Mass: Very close to  D 0 D *0 threshold Width: Very narrow, < 1.2 MeV J PC =1 ++ (is it  c1 (2P)? Small E1 transition to J/  ) Production –in  pp/pp collison – similar to charmonia –In B decays – KX similar to cc, K*X smaller than cc Decay BR: open charm ~ 50%, charmonium~O(%) Nature (very likely exotic) –Loosely  D 0 D *0 bound state (like deuteron?)? –Mixture of excited  c1 and  D 0 D *0 bound state? –Many other possibilities (if it is not  ’ c1, where is  ’ c1 ?)

23 23 The Y states Belle: PRL99, , 670/fb /fb PRD86, /fb BaBar: PRL101, /fb M(  c +  c - ) Above  DD threshold, decay to open charm? Y(4008) Y(4260) Y(4360) Y(4660) Y(4630)

24 24 High mass charmonia What is the nature of the newly observed states? Charmonium? Hybrid? Hadro-charmonium? Tetraquark? Molecular? … Can BES3 answer?

25 25 What do we do at BESIII Below open-charm: Spin-singlet states: 1.  c – high precision resonance parameters 2.h c – resonance parameters/production rate 3.  c (2S) – missing radiative transition in  (2S) Above open-charm 1.Better resonance parameters 2.New charmonium-(like) states [XYZ particles] Charmonium decays [pQCD rule, …] Other new phenomena (chance for discovery?)

26 26 Combined inclusive and E1-photon-tagged spectrum ( First measurements ) B(  ’    h c ) = [ 8.4±1.3(stat.) ±1.0(syst.)]× B(h c   c ) = [54.3±6.7(stat.) ±5.2(syst.)] % BESIII: PRL 104, (2010) Mass:  0.13  0.18 MeV Width: 0.73  0.45  0.28 MeV (< % C.L.) CLEOc: PRL101, (2008) Mass:  0.19  0.12 MeV Width: fixed to 0.9 MeV  M hf = -M( 1 P 1 ) Agrees with zero within ~0.5 MeV Information on spin-spin interaction. Agree with predictions of Kuang, Godfrey, Dudek, et al. BESIII:  (2S)   0 h c transition

27 27 Dominant errors in mass and width measurements are from photon energy calibration, resolution calibration, and kinematic fit. Can be improved with more data! 16 modes, 832 events Mass:  0.11  0.15 MeV Width: 0.70  0.28  0.25 MeV CLEOc: PRL101, (2008) Mass:  0.19  0.12 MeV Width: fixed to 0.9 MeV BESIII h c via  (2S)   0 h c   0  c transition PRD86 , (2012)

28 28  c resonant parameters from  '  c KsK  K+KK+K  KsK3  2K2    Simultaneous fit with modified Breit-Wigner (hindered M1) by considering possible interference between  c and non-  c decays arXiv: , PRL108, (2012)

29 29 Mass and width of  c Mass = ±0.6 ± 0.6 MeV/c 2 [LQCD found a higher mass!] Width = 32.0±1.2 ± 1.0 MeV  = 2.40±0.07 ± 0.08 rad or 4.19±0.03 ± 0.09 rad (two solutions of the interference) World average in PDG2012 uses earlier measurements. arXiv: , PRL108, (2012)

30 30  c properties from h c   c M(  c ) [MeV]  (  c ) [MeV]N(  c ) ±1.16± ±3.2± E1 transition! E  suppression less severe than in M1 transition! Irreducible non-  c background is smaller than in  ’ decays! PRD86 , (2012)

31 31 First observation of    c Simultaneous fit with:  c ’ signal: modified BW (M1) (Resolution extrapolated from  cJ )  cJ signal: MC shape smeared with Gaussian BGs from e + e -  KK  (ISR),  '  KK  (FSR),  '   0 KK  : are measured from data Statistical significance > 10  arXiv: , PRL109, (2012)

32 32 First observation of    c Br(  '  c )=(6.8±1.1±4.5) ×10 -4 CLEO-c: <7.6  (PRD81,052002(2010)) Potential model: ( )  (PRL89,162002(2002)) M(  c ) = ±2.9±1.6 MeV/c 2  (  c ) = 16.9  6.4  4.8 MeV Br(  '  c  KK  )=(1.30±0.20±0.30) ×10 -5 Br(  c  KK  )=(1.9±0.4±1.1)% from BaBar 18 年的努力! arXiv: , PRL109, (2012)

33 XYZ 粒子研究前景 CLEOc 已停止运行,合作组已不复存在,没有足够的 数据进行相关研究; BaBar 和 Belle 已停止运行,利用全部数据更新进行中, 精度没有显著改善; PANDA(Germany)/SuperC(Italy)/Tau-C- factory(Russia) 遥遥无期, 5(10?) 年内不可能开始运行; LHC 实验( ATLAS, CMS, LHCb )背景复杂,仅能对 非常少的过程进行测量。 BESIII 是近 5 年唯一可以系统研究  cc +XYZ 的实验! BelleII 2016 年采集数据,在 2018 年前不会有足够数据, 但 2018 开始将再次主导该领域(  cc +  bb + XYZ! )。 33

34 34 BESIII: 粲偶素、类粲偶素的产生  /Y 粒子可以直接产生(出现在上图中) 电荷共轭宇称为正的粒子可以通过辐射跃迁产生 From PDG BEPCII can reach here!

35 35 通过R值扫描研究矢量态 目标:确定  激发态和 Y 态的共振参数和衰变特性 方法:精确测量不同能量点各主要过程截面 利用耦合道信息拟合数据

36 36 通过矢量态辐射跃迁研究C=+的态  (nS/nD)   +XYZ [X(3872), XYZ(3940) 等 ] – 跃迁几率没有理论预期 寻找  cJ (2P) 、  cJ (3P) 、  c (3S) 、  c (4S) 、 … –B(  (3S)   ’ cJ )=(7, 3, 1)x10 -4 for J=2,1,0 [ E. Eichten et al., Rev. Mod. Phys. 80, 1161 (2008) ] 完善粲偶素能谱 确认奇特态粒子 MC study

37 37 寻找矢量态强子跃迁中的共振结构 目标:寻找 Z c 态,寻找 h c (2P) 态 方法:分析 Y(4260)   J/  、  h c (1P) 中的中间态 分析 Y(4360)   ’ 、  h c (2P) 中的中间态

38 38 Check Dalitz Plots & mass projections (M(  J/  )  [4.2, 4.4] GeV) Peaks at 12 & 15 GeV 2 ? Chen Dian-Yong & Liu Xiang PRD84, (2011) Y4260

39 Observation of the Z c (3900) — a charged charmoniumlike structure — BESIII: 3 月 24 日 Belle : 3 月 30 日 CLEOc : 4 月 10 日 Z c established !

40 40 Hadrons : normal & exotic Hadrons are composed from 2 (meson) quarks or 3 (baryon) quarks Quark model QCD doesnot forbid hadrons with N quarks  2, 3 –glueball: N quarks = 0 (gg, ggg, …) –hybrid: N quarks = 2 (or more) + excited gluon –multiquark state: N quarks > 3 –molecule: bound state of more than 2 hadrons

41 41 A bit history on exotics hunting “The absence of exotics is one of the most obvious features of QCD” – R. L. Jaffe, 2005 Deuteron  H state,  -  - bound state, … No solid signature of glueballs Pentaquark state appeared and disappeared (“The story of pentaquark shows how poorly we understand QCD” – F. Wilczek, 2005) There are lots of new states from low to high mass in various experiments! Are they normal or exotic?

42 42 Why hard to identify exotic state? Which dwarf was named “Happy”? I donot know … No solid signature!

43 43 Why hard to identify exotic state? Which beauty is “Snow White”? Yes, I know! “Hair black as ebony [乌木, 黑檀]”. Very clear signature!

44 44 How to identify an exotic meson? Find a clear signature for exotic state! Decays to charmonium thus has a  cc pair! With electric charge thus has two more light quarks!  N quark  4 ! Do searches in π  J/ψ, π  ψ(2S), π   cJ, …

45 45 What do we do at BESIII  (e + e -   +  - J/  ) reaches maximum at ~4.26 GeV We proposed a 45 days’ data taking for 500 pb -1 data at peak ~1500 reconstructed events are expected [3xB-factories] We may search for such state if it decays into π  J/ψ !

46 46 Data taking at BESIII Highest energy BEPCII ever reach, L peak ~ 5.3x10 32 /cm 2 /s ! BEMS measures Ecm at 1 MeV level ! Low background, low noise, all sub-detectors excellent ! Accumulated 525 pb -1 in 30 days! 40 times of CLEO-c data!

47 47 Data quality is excellent Data calibration, reconstruction, MC simulation were finished shortly after the data taking … Production version was ready earlier March …  M D = 0.5  0.2 MeV  M D = 6.0  0.1 MeV  M  ’ = 0.2  0.1 MeV  M  ’ = 2.0  0.1 MeV D0KD0K ISR  ’

48 48 Select e + e -   +  - J/  events Select 4 charged tracks and reconstruct J/  with lepton pair. Very clean sample, very high efficiency. Use kinematic fit. Only use MDC & EMC information, MC simulation reliable. Typical J/   e + e - Typical J/    +  -

49 49 The J/  signals Dominant background e + e -  +  -  +  - J/  signal: [3.08,3.12] GeV J/  sideband: [3.0,3.06] GeV or [3.14,3.20] GeV, 3xsignal At least 4 independent analyses, all get similar results ! BESIII: arXiv:  33 J/    +   28 J/   e + e -

50 50 Cross section of e + e -   +  - J/  Belle: BaBar: PRD86, (2012) BESIII:  (e + e -   +  - J/  ) = (62.9  1.9  3.7) pb Agree with BaBar & Belle! Best precision! BESIII: arXiv:

51 Dalitz plots & 1D projections 51 BESIII: arXiv:

52 Is it a real signal? 52  Is it due to  +  - S-wave states, like , f 0 (980), …? N  Is it due to  +  - D-wave states, like f 2 (1270), …? N  Are there two states, one at 3.4, the other 3.9 GeV? N  Exist in both e + e - &  +  - samples? Y  Exist in both  +  - low mass and high mass samples? Y  Background fluctuation? N

53 The Z c (3900) signal 53  S-wave Breit-Wigner with efficiency correction  Mass = (3899.0±3.6±4.9) MeV  Width = (46±10±20) MeV  Fraction = (21.5±3.3±7.5)% Couples tocc Has electric charge At least 4-quarks What is its nature? BESIII: arXiv: Significance >8 

54 Observed in two experiments! 54 BESIII: Belle with ISR: M =  6.6  4.5 MeV  = 63  24  26 MeV 159  49 events >5.2  M =  3.6  4.9 MeV  = 46  10  20 MeV 307  48 events >8 

55 Confirmed! 55 BESIII: CLEO at 4.17 GeV: M = 3885  5  1 MeV  = 34  12  4 MeV 81  20 events 6.1  M =  3.6  4.9 MeV  = 46  10  20 MeV 307  48 events >8 

56 11 citations since results released 1. arXiv: Title: Observation of the Charged Hadron Zc(3900) at sqrt(s)=4170 MeV Authors: T. Xiao, S. Dobbs, A. Tomaradze, Kamal K. Seth 2. arXiv: Title: Electromagnetic Structure of the Z_c(3900) Authors: E. Wilbring, H.-W. Hammer, U.-G. Meißner 3. arXiv: Title: Could Z_{c}(3900) be a I^{G}J^{P}=1^{+}1^{+} D^{*}\bar{D} molecular state? Authors: Chun-Yu Cui, Yong-Lu Liu, Wen-Bo Chen, Ming-Qiu Huang 4. arXiv: Title: Interpreting Z(3900) Authors: Namit Mahajan 5. arXiv: Title: The doubly heavies: (Qbar Q qbar q), (Q Q qbar qbar) tetraquarks and (Q Q q) baryons Authors: Marek Karliner, Shmuel Nussinov 6. arXiv: Title: Z_c(3900) - what is inside? Authors: M.B. Voloshin 7. arXiv: Title: Study of e+ e- to π+ π- J/ψ and Observation of a Charged Charmonium-like State at Belle Authors: Belle Collaboration 8. arXiv: Title:A J^PG=1++ Charged Resonance in the Y(4260) to pi+pi- J/psi Decay? Authors: R. Faccini, L. Maiani, F. Piccinini, A. Pilloni, A.D. Polosa, V. Riquer 9. arXiv: Title: Predictions of charged charmonium-like structures with hidden-charm and open-strange channel Authors: Dian-Yong Chen, Xiang Liu, Takayuki Matsuki 10. arXiv: Title: Consequences of Heavy Quark Symmetries for Hadronic Molecules Authors: Feng-Kun Guo, Carlos Hidalgo-Duque, Juan Nieves, Manuel Pavon Valderrama 11. arXiv: Title: Decoding the riddle of Y(4260) and Z_c(3900) Authors: Qian Wang, Christoph Hanhart, Qiang Zhao 56

57 What next? We are accumulating 3x more data Precise resonant parameters Spin-parity [PWA on going] More decay modes Production mechanisms, production rate Test various theoretical models Neutral partner of Z c Other Z c states? Z c ’ states? … 57 XYZ group expanding rapidly since Jan., but more are welcome B424 (40.96 m 2 )  B410 (95.04 m 2 ) Everyone is working excitedly and passionately!

58 58 Summary and Outlook Charmonium physics is a gold mine: – Large data samples collected in e  e   annihilation at BES-III – more than 1 Billion B pairs at Belle and BaBar Similar progress in theory (NRQCD, Lattice QCD) Longer range outlook: –Charmonium results from BES-III/BEPC-II [Zc and more …] –Belle II (start from 2016) will continue to produce charmonium results from even more B-meson decays, ISR study, double charmonium production, two-photon processes –Charmonium physics from hadronic machines? (LHCb, CMS, Atlas, … ) –Charmonium at dedicated  pp machine PANDA/GSI: (>2018- ) Wish charmonium physics a bright future! Welcome to join us (IHEP or BES group in your University)!

59 Thanks a lot! 59

60 Thanks a lot! 60

61 61

62 62

63 63

64 64 Belle observed Z(4430) ± →ψ(2S)π ±  Found in ψ(2S)π + from B→ψ(2S)π + K. Z parameters from fit to M(ψ(2S)π + )  Confirmed through Dalitz-plot analysis of B→ψ(2S)π + K  B→ψ(2S)π + K amplitude: coherent sum of Breit-Wigner contributions  Models: all known K*→Kπ + resonances only all known K*→Kπ + and Z + →ψ(2S)π +  favored by data  [cu][cd] tetraquark? neutral partner in ψ’π 0 expected  D*D 1 (2420) molecule? should decay to D*D*π PRL100, (2008) PRD80, (2009) Significance: 6.4σ Significance: 6.4σ M 2 (ψ(2S)π + ) M 2 (Kπ + ) K*(890) K 2 *(1430) Z + (4430) M 2 (ψ(2S)π + ) after K* veto 657M BB – ̶̶̶̶̶̶ – ̶̶̶̶̶̶ fit for model with K*’s only – ̶̶̶̶̶̶ – ̶̶̶̶̶̶ fit for model with K*’s and Z

65 65 BaBar doesn’t see a significant Z(4430) + “For the fit … equivalent to the Belle analysis…we obtain mass & width values that are consistent with theirs,… but only ~1.9  from zero; fixing mass and width increases this to only ~3.1 .” Belle PRL: (4.1 ± 1.0 ± 1.4)x10 -5 PRD79, (2009)

66 66 Belle observed Two Z ± →χ c1 π ±  Dalitz-plot analysis of B 0 →χ c1 π + K - χ c1 →J/ψγ with 657M BB  Dalitz plot models: known K*→Kπ only K*’s + one Z →χ c1 π ± K*’s + two Z ± states  favored by data M(χ c1 π + ) for 1

67 67 BaBar doesn’t see significant Z ± →χ c1 π ± “We find that it is possible to obtain a good description of our data without the need for additional resonances in the  c1  system.” PRD85, (2012) Belle: ( )x10 -5 Belle: ( )x10 -5

68 M(  J/  )  [4.2, 4.4] GeV via ISR 550/fb at GeV Peaks at 12 & 15 GeV 2 ? Shown at QWG’2011

69 69 密康公母论小丑备物终必亡 恭王游于泾上,密康公从,有三女奔之。 其母曰: “ 必致之于王。夫兽三为群,人三为 众,女三为粲。王田不取群,公行下众,王 御不参一族。夫粲,美之物也。众以美物归 女,而何德以堪之?王犹不堪,况尔小丑乎? 小丑备物,终必亡。 ” 康公不献。一年,王灭 密。 《国语 · 周语上》

70 70 NameJ PC Γ(MeV) Decay modesExperimentsinterpretation X(3872)1 ++ /2 -+ <1.2  J/ ,  J/ , DD*, … Belle/CDF/D0/BaBar/ LHCb  DD* molecule? X(3940)0 ?+ ~37DD* (not DD, ωJ/ ψ ) Belle η c ’’ (?) Y(3940)? ?+ ~30 ω J/ψ (not DD *) Belle/BaBar Y(4140)? ?+ ~11  J/ψ CDF(not Belle/LHCb) ccss? X(4160)0 ?+ ~140D*D* (not DD, DD*) Belle η c ’’ (?) Y(4008)1 -- ~220  J/  Belle (not Babar)  (4040)? Y(4260)1 -- ~80  J/  BaBar/CLEO/Belle ccg hybrid? X(4350)? ?+ ~13 ,  J/ψ Belle ccss? Y(4360)1 -- ~75  (2S) BaBar/Belle Y(4660)1 -- ~50  (2S), Λ c Λ c (?) Belle/BaBar Z ± (4430)? ?? ~100ψ(2S)π ± Belle (not Babar) 4-quark? Z ± (4050)?????? ~80χc1π±χc1π± Belle (not Babar) 4-quark? Z ± (4250)?????? ~180χc1π±χc1π± Belle (not Babar) 4-quark? XYZ states charged Z neutral X and Y


Download ppt "1 发现 Z c (3900) -- BESIII实验粲偶素研究 -- Yuan Changzheng ( 苑 长 征 ) IHEP, Beijing 2013年4月18日."

Similar presentations


Ads by Google