多夸克态前沿简介 - ustc,...

多夸克态前沿简介

邹冰松

中国科学院理论物理研究所

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

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 > 10-10 m

• 强相互作用 原子核、强子结构 10-16 ~10-14 m

• 弱相互作用 夸克、轻子跃迁 < 10-21 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

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

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

u u-dd-

二. 多夸克态研究的意义

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”？

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

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

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

e

p

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 ?

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 > + e1 | n ( udd ) p+ (`du ) >+ e2 | D++ ( uuu ) p- (`ud ) > + e’ | L (uds) K+ (`su ) > …

夸克对图像 : Riska, Zou, Zhu, …

| p > ~ | uud > + e1 | [ud][ud]`d > + e’ | [ud][us]`s > + …

du

d u

`du

ud

d

`d

质子结构：

ud

u

u

du

`sS

ud

u

u

du

`sS

重子激发态的呼吸-振荡模式

多夸克态和 gluons `qq 机制的研究

对了解强子结构至关重要！

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.”

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- ~ L*(1405) ~ [ud][su]`u

uus (L=1) 1/2- ~ S*(1390) ~ [us][ud]`d

Zou et al, NPA835 (2010) 199 ; CLAS, PRC87(2013)035206

• Strange decays of N*(1535) and L*(1670) :

N*(1535) large couplings gN*Nh , gN*KL ， gN*Nh’，gN*Nf

L*(1670) large coupling gL*Lh

4) 0++ meson SU(3) octet as 4-quark states ?

w(782) `uu +`dd

r(770) `uu -`dd

K(892) `sd

f(1020) `ss

`qq 3S1 nonet `qq 3P0 or `q2q2 nonet ?

f0(980) `ss , [ u s] [us] + [ d s] [ds]

k(800) `sd , [ s u] [ud ]

f0(600) `uu +`dd , [ u d] [ud]

a0(980) `uu -`dd , [ u s] [us] -[ d s] [ds]

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 + …

5) 奇特的 q+ “`suudd-五夸克态”

Strange pentaquark

q+ predicted by

D.Diakonov et al.,Z.Phys.A359 (1997)305

suudsduudd3

2

3

1

suussduusd3

1

3

2

First evidence from LEPS

g nK+K-n

No L(1520) peak in events

without a proton.

M = 1540 10 MeV

G < 25 MeV

Gaussian significance 4.6s

T. Nakano et al.,

Phys.Rev.Lett. 91 (2003) 012002

1061 citations

q+

q+ : PDG2004 established particle

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！

No q resonance in high statistics data from g11@CLAS

Phys. Rev. Lett. 96 (2006) 042001

e-Be electroproduction at Babar

HERMES (e+dKS0p + X)

M=15283 MeV

~5s

ZEUS (e-pe-KS0p + X)

M=15223 MeV

~5s

S*(1480)

Fit uses S*(1480) [PDG 1star]Possible acceptance loss in low mass region:

(PID requires p(p) >4.1 GeV/c; p(KS0)>3 GeV/c)

Preliminary

233 fb-1 e e- data

Tetiana Berger-Hryn’ova

Time dependent experimental status of Q+

: Positive result

: Negative result

lepton + D, A → p Ks0

K + (N) → p Ks0

γ + p → n K+ K- p+

γ + p → p Ks0

γ + d (n ) reactions

p + A → pKs0 + X

Other Q+ Upper Limits

p + p → pKs0 + S+

BaBar

CLAS-d2

BELLE

ALEPH, ZSVD2

LEPS-d2LEPS-C CLAS-d1

DIANA

SAPHIR

SVD2

COSY-TOF

Hermes

JINR

CLAS-p

LEPS-d

nBCZEUS

BES J,Y

CLAS g11

SPHINX HyperCP

HERA-B

FOCUS WA89CDF

2002 2003 2004 2005 2006

DIANA

BES penta-quark paper:

• The first negative result with 175 citations

Jaffe & Wilczek, PRL91(2003)232003 791 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 case-

history for historian and philosophers of science.’

F. Close

Words of wisdom T.Barnes (HADRON05)

Jorge Agustín Nicolás Ruiz de Santayana (1853-1952)

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)

For a comprehensive review, cf.:

H.X.Chen, W.Chen, X.Liu, S.L.Zhu, Phys.Rept. 639 (2016) 1-121

6) XYZ states with hidden charm and beauty

D.Y.Chen, X.Liu,

PRD84(2011)034032

Q.Wang,C.Hanhart,Q.Zhao

PRL111(2013)132003

a

Y(4260)

LHCb penta-quark states

LHCb, Phys.Rev.Lett. 115 (2015) 072001 :

Observation of two N* from

Pc(4450)Pc

(4380)

四. Pc-五夸克态

1. Predictions prior to LHCb observation

a) X.Y.Wang, X.R.Chen, “The production of hidden charm baryon N*4261)

from p-p hc n reaction”, EPL109 (2015) 41001.

b) E.J.Garzon, J.J.Xie, “Effects of a N`cc resonance with hidden charm in

the π-p D-Σc reaction near threshold”, PRC 92 (2015) 035201

c) X.Y.Wang, X.R.Chen, “Production of the superheavy baryon L*(4209)

in kaon-induced reaction”, EPJA51 (2015) 85

Proposals for looking for N`cc & L`cc with p-, K beams at JPARC

[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*Sc (3/2- ) N* state -- 4360 ~ 4460 MeV

Hidden charm N* above 4 GeV decaying to pJ/y

are supported by other approaches

`DSc state in a chiral quark model ~ 4.3 GeVW.L.Wang, F.Huang, Z.Y.Zhang, B.S.Zou, PRC84(2011)015203

`DSc state in EBAC-DCC model ~ 4.3 GeV

J.J.Wu, T.S.H.Lee, B.S.Zou, PRC85(2012)044002

LHCb pentaquark states vs Predictions

Consistence : mass of Pc (3/2-), pJ/y decay mode

Problems:

1) Pc(4380) -- larger decay width than prediction

2) mass deference of Pc (5/2) & Pc (3/2-) too small

3) Where are lower Pc (1/2-) states ?

`DSc* ,`D*Sc ,`D*Sc * bound states

[1] R.Chen, X.Liu, X.Q.Li, S.L.Zhu, PRL115 (2015) 132002;

Pc(4380) -- `D*Sc 3/2- ; Pc

(4450) -- `D*Sc* 5/2-

[2] H.X.Chen, W.Chen, X.Liu, T.G.Steele, S.L.Zhu, PRL115 (2015)172001

Pc(4380) -- `D*Sc 3/2- ; Pc

(4450) -- `DSc*-`D*Lc 5/2

[3] J.He, PLB 753 (2016)547 ; PRD95 (2017)074004

Pc(4380) -- `DSc*/`D*Sc 3/2- ; Pc

(4450) -- `D*Sc 5/2

[4] Y.Yamaguchi, E. Santopinto, arXiv:1606.08330;

Pc(4380) --`D(*)Sc

(*) -`D(*)Lc 3/2 ; Pc(4450) -- `D(*)Sc

(*) -`D(*)Lc 5/2-

Disentangling`DSc* /`D*Sc nature of Pc states from their decays

Y.H.Lin, C.W.Shen, F.K.Guo, B.S.Zou, ArXiv: 1703.01045

It is very important to study Pc `D*L &`DL !

LHCb pentaquark states vs Post-explanations

Consistent for Pc(4380) to be a`DSc* (3/2-) molecule with

a large decay width to`D*Lc

Consistent for Pc(4450) to be a`D*Sc (5/2) molecule

Problems:

1) Where are lower Pc (1/2-) states ?

2) Where are predicted L`cc states ?

Many more pentaquarks are expected !

五. 展望

1) Zb/c & Pc 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

arXiv:1703.04639

Wc states

`pp@PANDA – a better place for more Wc states ?

3) 理论和实验密切配合非常重要

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 EIC@HIAF & 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！