Presentation is loading. Please wait.

Presentation is loading. Please wait.

发现 Zc(3900) -- BESIII实验粲偶素研究 -- Yuan Changzheng (苑 长 征) IHEP, Beijing

Similar presentations

Presentation on theme: "发现 Zc(3900) -- BESIII实验粲偶素研究 -- Yuan Changzheng (苑 长 征) IHEP, Beijing"— Presentation transcript:

1 发现 Zc(3900) -- BESIII实验粲偶素研究 -- Yuan Changzheng (苑 长 征) IHEP, Beijing

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

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

4 The Beijing Electron Positron Collider
Satellite view of IHEP, Beijing LINAC My office BEPC (Beijing electron-positron collider) Founded: 1984, Ecm=2-5 GeV (BEPC): Lpeak=1.0x1031 /cm2s 2008-now (BEPCII): Lpeak=6.5x1032/cm2s BES detector Main entrance to IHEP

5 BEPC II: Large crossing angle, double-ring
Beam energy: 1-2.3 GeV Luminosity: 1×1033 cm-2s-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 RF RF Compton back-scattering for high precision beam energy measurement BESIII is here IP

6 CsI(Tl) calorimeter, 2.5% @ 1 GeV
BESIII Detector SC magnet, 1T Magnet yoke RPC TOF, 90ps Be beam pipe MDC, 130 m 0.5% at 1 GeV/c Total weight 730 ton, ~40,000 readout chnls, Data rate: 5kHz, 50Mb/s CsI(Tl) calorimeter, 1 GeV

7 BESIII Physics Programs
This is not a BESIII logo! BEST 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”)

8 基本粒子(费米子) 第一代、第二代、第三代

9 Onia cc J/y 0.09 3.1 Quarkonium is the bound state of quark and
FORCES System Ground triplet state 13S1 (v/c)2 Number of states below dissociation energy binding decay Name G (MeV) Mass (GeV) n3S1 all POSITRONIUM EM e+e- Ortho- 5x10-15 0.001 ~0.0 2 8 QUARKONIUM S T R O N G uu,dd r 150 0.8 ~1.0 ss f 4 1.0 ~0.8 “1” “2” E M cc J/y 0.09 3.1 ~0.25 bb 0.05 9.5 ~0.08 3 30 weak tt (3000.0) (350.) <0.01 Quarkonium is the bound state of quark and anti-quark by the gluon. Charmonium is charm anti-charm bound state!

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

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

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

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

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

15 Charmonia study in e+e -annihilation
Advantages: Background small Production rate high All kinds of final states Inclusive/exclusive BESIII A typical event in BES detector ψ(2S)J/ψπ+π- J/ψ e+e- J/ψ Sample in Million 225+ 1000 106+ 350! Disadvantages: Only JPC=1-- can be formed directly Resolution sometimes is not good ψ(2S) Sample in Million 58 25 14 Earlier exp. not listed Hundreds of papers, hundreds of channels, thousands of measurements listed by the Particle Data Group in 2012.

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

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

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

20 Then we found lots of XYZ states
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)。 What are they ? Charmonium? Hybrid? Tetraquark? Molecule? Z(4430) Z(4250) Z(4050) ? X(3872) XYZ(3940) X(3915) X(4160) Y(4008) Y(4140) Y(4260) Y(4360) X(4350) Y(4660) Not all XYZ states are charmonia!

21 X(3872)p+p- J/y B±XK± B±XK± B0XK0 B0XK0
latest results PRD84, (2011) 711 fb-1 PRD 77, (2008) 413 fb-1 B±XK± Ns=93±17 8.6 B±XK± B0XK0 B0XK0 Ns=9±5 2.3 M=MX(3872)-MD0D*0 = ± 0.32 MeV

22 What is X(3872)? Mass: Very close toD0D*0 threshold
Width: Very narrow, < 1.2 MeV JPC=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D0D*0 bound state (like deuteron?)? Mixture of excited c1 andD0D*0 bound state? Many other possibilities (if it is not ’c1, where is ’c1?)

23 Above DD threshold, decay to open charm?
The Y states Belle: PRL99, , 670/fb BaBar: 967/fb Y(4008) Y(4260) Y(4360) Y(4660) Y(4630) PRD86, 454/fb PRL101, 695/fb Above DD threshold, decay to open charm? M(c+c-)

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

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

26 BESIII: (2S)0hc transition
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 Mhf= <M(3PJ)>-M(1P1) Agrees with zero within ~0.5 MeV Information on spin-spin interaction. Combined inclusive and E1-photon-tagged spectrum (First measurements) B(y’p0hc) = [ 8.4±1.3(stat.) ±1.0(syst.)]×10-4 B(hcghc) = [54.3±6.7(stat.) ±5.2(syst.)] % Agree with predictions of Kuang, Godfrey, Dudek, et al.

27 hc via (2S)0hc0c transition
PRD86, (2012) BESIII 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 Dominant errors in mass and width measurements are from photon energy calibration, resolution calibration, and kinematic fit. Can be improved with more data!

28 hc resonant parameters from 'c
arXiv: , PRL108, (2012) KsKp K+K-p0 p+p-h KsK3p 2K2pp0 6p Simultaneous fit with modified Breit-Wigner (hindered M1) by considering possible interference between c and non-c decays

29 Mass = 2984.3±0.6±0.6 MeV/c2 [LQCD found a higher mass!]
Mass and width of c arXiv: , PRL108, (2012) Mass = ±0.6±0.6 MeV/c2 [LQCD found a higher mass!] Width = 32.0±1.2±1.0 MeV f = 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.

30 c properties from hcc
PRD86, (2012) M(c) [MeV] (c) [MeV] N(c) ±1.16±0.52 36.4±3.2±1.7 1035 E1 transition! E suppression less severe than in M1 transition! Irreducible non-c background is smaller than in ’ decays!

31 First observation of c
arXiv: , PRL109, (2012) Statistical significance > 10s 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), '  0KK: are measured from data

32 First observation of c
18年的努力! arXiv: , PRL109, (2012) M(hc) = ±2.9±1.6 MeV/c2 G(hc) = 16.96.44.8 MeV Br(y'ghcgKKp)=(1.30±0.20±0.30) ×10-5 Br(hcKKp)=(1.9±0.4±1.1)% from BaBar Br(y' ghc)=(6.8±1.1±4.5) ×10-4 CLEO-c: <7.6 (PRD81,052002(2010)) Potential model: ( ) (PRL89,162002(2002))

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! )。

34 电荷共轭宇称为正的粒子可以通过辐射跃迁产生
BESIII: 粲偶素、类粲偶素的产生 From PDG BEPCII can reach here! /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

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 通过矢量态辐射跃迁研究C=+的态 完善粲偶素能谱 确认奇特态粒子 MC study
(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 寻找矢量态强子跃迁中的共振结构 目标:寻找Zc态,寻找hc(2P)态 方法:分析Y(4260)J/、hc(1P)中的中间态

38 Check Dalitz Plots & mass projections (M(J/)[4.2, 4.4] GeV)
Y4260 Peaks at 12 & 15 GeV2? Chen Dian-Yong & Liu Xiang PRD84, (2011) Y4260

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

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

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

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 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!  Nquark  4 ! Do searches in πJ/ψ, πψ(2S), πcJ, …

45 What do we do at BESIII We may search for such state if it decays into πJ/ψ ! (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]

46 Data taking at BESIII Accumulated 525 pb-1 in 30 days!
40 times of CLEO-c data! Highest energy BEPCII ever reach, Lpeak ~ 5.3x1032/cm2/s ! BEMS measures Ecm at 1 MeV level ! Low background, low noise, all sub-detectors excellent !

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

48 Select e+e- +-J/ events
Typical J/ +- Typical J/ e+e- 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.

49 The J/ signals 88233 59528 J/ +- J/ e+e-
BESIII: arXiv: 88233 J/ +- 59528 J/ e+e- 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 !

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
BESIII: arXiv:

52 Is it a real signal? Is it due to +- S-wave states, like , f0(980), …? N Is it due to +- D-wave states, like f2(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 Zc(3900) signal Significance >8 Couples tocc
BESIII: arXiv: Significance >8 Couples tocc Has electric charge At least 4-quarks What is its nature? 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)%

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

55 Confirmed! CLEO at 4.17 GeV: 1304.3036 BESIII: 1303.5949
M = 3.64.9 MeV  = 461020 MeV 307  48 events >8 M = 388551 MeV  = 34124 MeV 81  20 events 6.1

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

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 Zc Other Zc states? Zc’ states? XYZ group expanding rapidly since Jan., but more are welcome B424 (40.96 m2) B410 (95.04 m2) Everyone is working excitedly and passionately!

58 Welcome to join us (IHEP or BES group in your University)!
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!

60 Thanks a lot!




64 Belle observed Z(4430)±→ψ(2S)π±
PRL100, (2008) 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’π0 expected D*D1(2420) molecule? should decay to D*D*π M2(ψ(2S)π+) M2(Kπ+) K*(890) K2*(1430) Z+(4430) M2(ψ(2S)π+) after K* veto 657M BB Significance: 6.4σ –̶̶̶̶̶̶ –̶̶̶̶̶̶ fit for model with K*’s only –̶̶̶̶̶̶ –̶̶̶̶̶̶ fit for model with K*’s and Z PRD80, (2009)

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

66 Belle observed Two Z±→χc1π±
Dalitz-plot analysis of B0→χc1π+K- χc1 →J/ψγ with 657M BB Dalitz plot models: known K*→Kπ only K*’s + one Z →χc1π± K*’s + two Z± states  favored by data PRD 78, (2008) Significance: 5.7 –̶̶̶̶̶̶ –̶̶̶̶̶̶ fit for model with K*’s –̶̶̶̶̶̶ –̶̶̶̶̶̶ fit for double Z model –̶̶̶̶̶̶ –̶̶̶̶̶̶ Z1 contribution –̶̶̶̶̶̶ –̶̶̶̶̶̶ Z2 contribution M(χc1π+) for 1<M2(K-π+)<1.75GeV2

67 BaBar doesn’t see significant Z±→χc1π±
PRD85, (2012) Belle: ( )x10-5 Belle: ( )x10-5 “We find that it is possible to obtain a good description of our data without the need for additional resonances in the c1 system.”

68 M(J/)[4.2, 4.4] GeV via ISR
550/fb at GeV Peaks at 12 & 15 GeV2? Shown at QWG’2011

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

Download ppt "发现 Zc(3900) -- BESIII实验粲偶素研究 -- Yuan Changzheng (苑 长 征) IHEP, Beijing"

Similar presentations

Ads by Google