多夸克态前沿简介 邹冰松 中国科学院理论物理研究所

Transcription

1 多夸克态前沿简介 邹冰松 中国科学院理论物理研究所

2

3

4 内容提要 一. 强子物理研究的意义二. 多夸克态研究的意义三. 多夸克态寻找的艰难历程四. Pc- 五夸克态五. 展望

5 一. 强子物理研究的意义 1) 强子结构 -- 物质微观结构研究的最前沿 引力相互作用宇宙 天体结构 > 10-2 m 电磁相互作用分子 原子结构 > m 强相互作用原子核 强子结构 ~10-14 m 弱相互作用夸克 轻子跃迁 < m 强子是目前人类观测到具有内部结构的最小单元 2) 强子物理是原子核物理 基本粒子物理 宇宙天体演化物理的重要组成部分 核子占宇宙中的可见物质的 99% 以上

6 核子质量起源 : ~ 1% 来自 Higgs 机制 ~ 99% 来自强相互作用 C.D. Roberts, Prog. Part. Nucl. Phys. 61 (2008) 50-65

7 二. 多夸克态研究的意义 强子结构 : 夸克和胶子是如何构成强子的? Unquenched dynamics: gluons `qq crucial for quark confinement & hadron structure d - - u d u

8 重子是如何构成的? A. 3 夸克态 B. 夸克 - 胶子混杂态 C. 偶夸克 - 夸克态 D-E. 多夸克态 预言的核子激发态 N* 数目 :D-E > B > A > C 实验已观测到的 N* 数目 <A, 失踪? 人类对重子谱的了解还非常贫乏缺乏行之有效的理论计算

9 探索强子内部结构的基本途径 1) 高能轻子 - 质子散射 质子内部夸克 - 胶子分布函数 p e 问题 : 光子 胶子与海夸克的相互转化, 原有的 再生的? 2) 强子 轻子 光子束流打靶 强子谱 强子衰变 原子谱 玻尔原子的量子理论 核谱壳模型 & 集体运动模型 强子谱?

10 质子结构 : 质子自旋 危机 `d `u ~ 0.12 `s(x) s(x) 等问题的两种不同的唯象解释 : 介子云图像 : Thomas, Speth, Weise, Oset, Brodsky, Ma, p > ~ uud > + e 1 n ( udd ) p + (`du ) > + e 2 D ++ ( uuu ) p - (`ud ) > + e L (uds) K + (`su ) > 夸克对图像 : Riska, Zou, Zhu, p > ~ uud > + e 1 [ud][ud]`d > + e [ud][us]`s > + u `d d d u d u u d `d

11 重子激发态的呼吸 - 振荡模式 u d S u `s u d S u `s u ud u ud 多夸克态和 gluons `qq 机制的研究 对了解强子结构至关重要!

12 三. 多夸克态寻找的艰难历程 1) 首个强子分子态 deuteron as pn-bound state 1932 年发现 2) 第 2 个强子分子态 L(1405) as`kn-bound state predicted by Dalitz&Tuan, PRL2(1959)425, 1961 年发现 1964 年夸克模型诞生 L(1405) as uds-state 2010 年 PDG: The clean Λc spectrum has in fact been taken to settle the decades-long discussion about the nature of the Λ(1405) true 3q state or mere`kn threshold effect? unambiguously in favor of the first interpretation.

13 3) 1/2 - baryon SU(3) nonet as 5-quark states? Mass pattern : quenched or unquenched? uds (L=1) 1/2 - ~ L*(1670) ~ [us][ds]`s uud (L=1) 1/2 - ~ N*(1535) ~ [ud][us]`s uds (L=1) 1/2 - uus (L=1) 1/2 - ~ L*(1405) ~ [ud][su]`u ~ S*(1390) ~ [us][ud]`d Zou et al, NPA835 (2010) 199 ; CLAS, PRC87(2013) Strange decays of N*(1535) and L*(1670) : N*(1535) large couplings g N*Nh, g N*KL, g N*Nh,g N*Nf L*(1670) large coupling g L*Lh

14 4) 0 ++ meson SU(3) octet as 4-quark states? `qq 3 S 1 nonet `qq 3 P 0 or `q 2 q 2 nonet? f(1020) `ss K(892) `sd a 0 (980) `uu -`dd, [`u`s] [us]-[`d`s] [ds] f 0 (980) `ss, [`u`s] [us] + [`d`s] [ds] k(800) `sd, [`s`u] [ud ] w(782) `uu +`dd r(770) `uu -`dd f 0 (600) `uu +`dd, [`u`d] [ud] D* s0 (2317) ~`sc (L=1) + [`q`s] [q c] + DK + D* s1 (2460) ~`sc (L=1) + D*K + X(3872) ~`cc (L=1) + [`q`c] [q c] + D*D +

15 5) 奇特的 q + `suudd- 五夸克态 Strange pentaquark q + predicted by D.Diakonov et al., Z.Phys.A359 (1997) uuddd 2 3 uudss 2 3 uusdd 1 3 uusss

16 First evidence from LEPS g n K + K - n M = MeV G < 25 MeV Gaussian significance 4.6s q + No L(1520) peak in events without a proton. T. Nakano et al., Phys.Rev.Lett. 91 (2003) citations

17

18 q + : PDG2004 established particle

19

20 M. Karliner and H. Lipkin, Phys. Lett. B 597 (2004) 309 Why the q + is seen in some experiments and not in others - a possible explanation 另一种可能的解释 : 某些实验结果不可靠 需要高统计量重复性实验检验!

21 No q resonance in high statistics data from g11@clas Phys. Rev. Lett. 96 (2006)

22 e - Be electroproduction at Babar Preliminary 233 fb -1 e e - data HERMES (e + d K S0 p + X) ZEUS (e - p e - K S0 p + X) M= MeV ~5s S * (1480) M= MeV ~5s Possible acceptance loss in low mass region: (PID requires p(p) >4.1 GeV/c; p(k S0 )>3 GeV/c) Fit uses S * (1480) [PDG 1star] Tetiana Berger-Hryn ova

23 Time dependent experimental status of Q + γ + d (n ) reactions γ + p p K 0 s γ + p n K + K - p + K + (N) p K 0 s lepton + D, A p K 0 s p + A pk s0 + X p + p pk s0 + S + Other Q + Upper Limits LEPS-C CLAS-d1 LEPS-d LEPS-d2 CLAS-d2 SAPHIR CLAS g11 CLAS-p BELLE DIANA ZEUS nbc BaBar Hermes DIANA SVD2 JINR SPHINX HyperCP SVD2 ALEPH, Z COSY-TOF HERA-B BES J,Y CDF FOCUS WA BES penta-quark paper: The first negative result with 175 citations : Positive result : Negative result

24 Jaffe & Wilczek, PRL91(2003) citations The story of the pentaquark shows how poorly we understand QCD. F. Wilczek the pentaquark story will probably have come to an end for physicists but will live on as a casehistory for historian and philosophers of science. F. Close

25 Words of wisdom T.Barnes (HADRON05) Jorge Agustín Nicolás Ruiz de Santayana ( ) AB, PhD Harvard (1886,1889). Prof. of Philosophy, Harvard (to 1912). "Those who cannot remember the past are condemned to repeat it." Life of Reason, Reason in Common Sense (1905) "Scepticism is the chastity of the intellect, and it is shameful to surrender it too soon or to the first comer." Scepticism and Animal Faith (1923)

26 6) XYZ states with hidden charm and beauty For a comprehensive review, cf.: H.X.Chen, W.Chen, X.Liu, S.L.Zhu, Phys.Rept. 639 (2016) 1-121

27

28 a Y(4260) D.Y.Chen, X.Liu, PRD84(2011) Q.Wang,C.Hanhart,Q.Zhao PRL111(2013)132003

29 LHCb penta-quark states LHCb, Phys.Rev.Lett. 115 (2015) : Observation of two N* from P c (4380) P c (4450)

30 四. P c - 五夸克态 1. Predictions prior to LHCb observation

31

32

33

34

35 Proposals for looking for N`cc & L`cc with p -, K beams at JPARC a) X.Y.Wang, X.R.Chen, The production of hidden charm baryon N*4261) from p - p h c n reaction, EPL109 (2015) b) E.J.Garzon, J.J.Xie, Effects of a N`cc resonance with hidden charm in the π - p D - Σ c reaction near threshold, PRC 92 (2015) c) X.Y.Wang, X.R.Chen, Production of the superheavy baryon L*(4209) in kaon-induced reaction, EPJA51 (2015) 85

36 [2] Z.C.Yang, Z.F.Sun, J.He, X.Liu, S.L.Zhu, The possible hidden-charm molecular baryons composed of anti-charmed meson and charmed baryon,'' Chin. Phys. C36 (2012) 6 Schoedinger Equation method with p, h, r, w, s exchanges: `D*S c (3/2 - ) N* state ~ 4460 MeV

37

38 Hidden charm N* above 4 GeV decaying to pj/y are supported by other approaches `DS c state in a chiral quark model ~ 4.3 GeV W.L.Wang, F.Huang, Z.Y.Zhang, B.S.Zou, PRC84(2011) `DS c state in EBAC-DCC model ~ 4.3 GeV J.J.Wu, T.S.H.Lee, B.S.Zou, PRC85(2012)044002

39

40 LHCb pentaquark states vs Predictions Consistence : mass of P c (3/2 - ), pj/y decay mode Problems: 1) P c (4380) -- larger decay width than prediction 2) mass deference of P c (5/2 ) & P c (3/2 - ) too small 3) Where are lower P c (1/2 - ) states?

41

42 `DS c *,`D*S c,`d*s c * bound states [1] R.Chen, X.Liu, X.Q.Li, S.L.Zhu, PRL115 (2015) ; P c (4380) -- `D*S c 3/2 - ; P c (4450) -- `D*S c * 5/2 - [2] H.X.Chen, W.Chen, X.Liu, T.G.Steele, S.L.Zhu, PRL115 (2015) P c (4380) -- `D*S c 3/2 - ; P c (4450) -- `DS c *-`D*L c 5/2 [3] J.He, PLB 753 (2016)547 ; PRD95 (2017) P c (4380) -- `DS c */`D*S c 3/2 - ; P c (4450) -- `D*S c 5/2 [4] Y.Yamaguchi, E. Santopinto, arxiv: ; P c (4380) --`D (*) S (*) c -`D (*) L c 3/2 ; P c (4450) -- `D (*) S (*) c -`D (*) L c 5/2 -

43 Disentangling`DS c * /`D*S c nature of P c states from their decays Y.H.Lin, C.W.Shen, F.K.Guo, B.S.Zou, ArXiv:

44 It is very important to study P c `D*L &`DL!

45 LHCb pentaquark states vs Post-explanations Consistent for P c (4380) to be a`ds c * (3/2 - ) molecule with a large decay width to`d*l c Consistent for P c (4450) to be a`d*s c (5/2 ) molecule Problems: 1) Where are lower P c (1/2 - ) states? 2) Where are predicted L`cc states? Many more pentaquarks are expected!

46 五. 展望 1) Z b/c & P c 的发现打开了研究多夸克态的窗口, 需要进一步系统的研究 BEPCII/ 超级 t-c BelleII p10/k10@jparc ep@jlab LHCb PANDA 等大有可为 2) 强子谱突破 & 发展战略 `ccuud &`ccuds sss -`qqsss light baryons ssc -`qqssc `cc`ud &`cs`ud `cc -`qq`cc light mesons

47 arxiv: W c states `pp@panda a better place for more W c states?

48 3) 理论和实验密切配合非常重要

49 结束语 我们对强子谱和强子结构的了解还很贫乏 国际上多个大型实验装置在开展这方面的研究 我国 BEPCII 及可能的 & super-tc 有独到之处, 为我国强子物理发展提供了良好的机遇 我们期待着从量变积累到质变的时刻 谢谢大家!