qiang zhao institute of high energy physics, cas

QCD exotics and production of threshold states

QCD exotics and production of threshold states

Institute of High Energy Physics, CASInstitute of High Energy Physics, CAS

Sixth Asia-Pacific Conference on Few-Body Problems in PhysicsAPFB 2014, April 7-11, 2014, Hahndorf, Australia

Qiang ZhaoInstitute of High Energy Physics, CAS

and Theoretical Physics Center for Science Facilities (TPCSF), CAS

[email protected]

Outline

1. Exotic feature of the spectra -- What drives the “exotic” feature?

2. Open threshold phenomena -- Production mechanism for threshold states

3. Some remarks

Charged charmonium spectrum -- A completely new scenario of strong QCD!

States close to open thresholds-- The role played by open D meson channels?

Close to DD* threshold

c

L

S=0,1

c

J=L+S

Charged heavy quarkonium states observed in exp.

Panel discussion in Charm 2013, Aug. 31-Sept. 4, 2013, Manchester

QWG, 1010.5827[hep-ph]

X(3900) X(3900)

Close to DD* threshold Close to DD* threshold

X(3872) X(3872)

Y(4260) Y(4260)

Y(4360) Y(4360)

1, (cc)/(bb) …*e+

e

• Direct production of vector charmonium (JPC=1) states. • Dynamics for vector charmonium interactions with final states.• What’s the role played by the S-wave thresholds?• Signals for vector exotics, e.g. Y(4260)? Or exotics produced in

vector charmonium decays, e.g. X(3872) and Zc(3900)?• ……

Belle, BaBar, and BESIII

i) Vector charmonium production in ee annihilations

c

c

q

q

Charmed meson pair production, i.e. D(0)D(0), D*(1)D*(1), D*D +DD*…

Belle PRD77, 011103(2008).

(377

0), 1

D

(40

40),

3S

(41

60)

(44

15)

X(39

00) ?

• What is X(3900)? (see Wang et al., PRD84, 014007 (2011))

• X(3900) has not been inlcuded in PDG2010 and PDG2012. • Not in charmonium spectrum • Why Y(4260) is not seen in open charm decays?• … …

e+e- DD

• Cross section lineshape in e+e- annihilations into DD pair

Y(4260)

(e+e- hadrons)

Y(4260)

Y(4260)

Observation of Y(4260) in J/ spectrum

PRD77, 011105 (2008) Belle

• Opportunities for a better understanding the nature of Y(4260) Theoretical prescriptions:

Hybrid Tetraquark Glueball Hadronic molecules Interference effects

Calculations done by various approaches:

Quark model Hadron interaction with effective potentials QCD sum rules Lattice QCD

See 1010.5827[hep-ph] for a recent review.

Cited 485 times!

Hybrid state, F.E.Close and P.R.Page, PLB28(2005)215; S.L.Zhu, PLB625(2005)212; E. Kou and O. Pene, PLB631(2005)164

Radial excitation of a diquark-antidiquark state analogous to X(3872), L.Maiani, F.Piccinini, A.D. Polosa and V. Riquer, PRD71(2005)014028

D1 D molecular state, G.J.Ding, PRD79(2009)014001; F. Close and C. Downum, PRL102(2009)242003; A.A.Filin, A. Romanov, C. Hanhart, Yu.S. Kalashnikova, U.G. Meissner and A.V. Nefediev, PRL105(2010)019101

Strongly couple to Χc0ω, M. Shi, D. L. Yao and H.Q. Zheng, hep-ph/1301.4004

Hadro-quarkonium, M. Voloshin

Inference effects, X. Liu et al

……

BESIII, PRL110, 252001 (2013) [arXiv:1303.5949 [hep-ex]]

• The mass of the charged charmonium-like structure Zc(3900) is about 3.899 GeV, close to DD* threshold! • It could be an opportunity for understanding the mysterious Y(4260).

e+

e

J/ Zc

Y(4260)

Belle, PRL110, 252002 (2013) [arXiv:1304.0121v1 [hep-ex]]

Xiao et al., arXiv:1304.3036v1 [hep-ex]

BESIII Collaboration, arXiv:1308.2760 [hep-ex]

Zc(3900)?

m(Zc(4020)) =

(Zc(4020)) =

Zc(4020)

Both Zc(4025) and Zc(4020) are close to the D*D* threshold. Are they the same state?


Y(4260)

JP = 1

JP = 0

JP = 1


Direct determination of the spin-parity!

Zc(3900)?

BESIII, PRL110, 252001 (2013) [arXiv:1303.5949 [hep-ex]]

Theoretical interpretations:•Hadro-quarkonium (M. Voloshin et al.)•Tetraquark (L. Maiani et al.)•Born-Oppenheimer tetraquark (E. Braaten)•Hadron loops (X. Liu et al.)•Hadronic molecule produced in a singularity condition (Q. Wang, C. Hanhart, Q.Z.)•… …

• Would Zc(3900) and Zc’(4020/4025) be an analogue of the Zb and Zb’ in the charm sector?

• How those states are formed? Are there always “thresholds” correlated?

• What is the dominant decay channel of Zc and Zc’ ?• What can we learn about the production mechanism for Zc and Zc’

from the lineshape measurement of J/psi pipi and hcpipi ?• How to distinguish various proposed scenarios?• … …

V(r) = /r r

Coulomb

Linear conf.

• The effect of vacuum polarization due to dynamical quark pair creation may be manifested by the strong coupling to open thresholds and compensated by that of the hadron loops, i.e. coupled-channel effects.

E. Eichten et al., PRD17(1987)3090B.-Q. Li and K.-T. Chao, Phys. Rev. D79, 094004 (2009); T. Barnes and E. Swanson, Phys.Rev. C77 (2008) 055206

qq creation

• Color screening effects? String breaking effects?

Breakdown of potential quark model

• The constituent mesons are in a relative S wave as a prerequisite. • Similar to the nuclear force, the long range interaction may play a

crucial role. • Different from the nuclear force, the nuclear repulsive core is not

obvious. The role of the annihilation potential is not clear. • The open threshold has strong impact on the spectrum.

-- How to stabilize the hadronic molecular states made of mesons?

-- How to recognize the molecular scenario in the spectroscopy?

-- Do we have a coherent picture for understanding those XYZ states in heavy quarkonium spectrum?

In case that hadronic molecules can be formed by mesons, the following points should be recognized:

Q. Wang et al, PRD2012

Y.J. Zhang et al, PRL(2009);

X. Liu, B. Zhang, X.Q. Li, PLB(2009)

Q. Wang et al. PRD(2012), PLB(2012)

The mass shift in charmonia and charmed mesons, E.Eichten et al., PRD17(1987)3090

X.-G. Wu and Q. Zhao, PRD85, 034040 (2012)

G. Li and Q. Zhao, PRD(2011)074005

F.K. Guo and Ulf-G Meissner, PRL108(2012)112002

X.-H. Liu et al, PRD81, 014017(2010);

X. Liu et al, PRD81, 074006(2010)

• In case that the open threshold coupled channels play a role, typical ways to include such an effect are via hadron loops in hadronic transitions

“ puzzle”

Hadronic molecule – an analogue to Deuteron

Heavy-light quark-antiquark pairs form heavy mesons, and the meson-antimeson pair moves at distances longer than the typical size of the meson. The mesons are interacting through exchange of light quarks and gluons, similar to nuclear force.

uu

dd u

dd

dd u

Proton

Neutron

Deuteron: p-n molecule

Can we learn something from nuclear interaction?

Weinberg (1963); Morgan et al. (1992); Baru, Hanhart et al. (2003); G.-Y. Chen, W.-S. Huo, Q. Zhao (2013) ...

Probability to find the hadronic molecule component in the physical state A

Weinberg’s Compositeness Theorem

The effective coupling geff encodes the structure information and can be extracted model-independently from experiment.

Y(4260) could be a hadronic molecule made of DD1(2420)

Q. Wang, C. Hanhart, QZ, PRL111, 132003 (2013); PLB(2013)

Y(4260) DD*

W= 4020 MeV

DD1(2420)

W= 4289 MeV

D (cq), JP=0;

D*(cq), JP=1;

D1 (cq), JP=1.

D1(2420)

D(1868)

Y(4260), 1 Y(4260) D1

D D0

D*

“threshold state”

• The signature of Y(4260) could be revealed by the associated Zc(3900) near the DD* threshold via “triangle singularity”!

[J.-J. Wu, X.-H. Liu, B.-S. Zou, and Q. Zhao, PRL108, 081003 (2012)]

J/ D*

D

M(Zc) M(D) + M(D*) = 3.876 GeV

Zc(3900), I,JP= 1, 1

A systematic study of the singularity regions in e+e- J/psi pipi, hc pipi and DD*pi is necessary.

• Y(4260)D1D coupling:

• Zc(3900)DD* coupling:

• D1D*pi coupling:

Lagrangians in the NREFT


• The implementation of Weinberg theorem is possible• S-wave dominates in the production of Zc(3900) • S-wave dominates in DD* scattering to J/psi pi• The Zc(3900) decays into hc pi is not necessarily suppressed by the NREFT power counting

Non-local pion radiation via triangle singularity kinematics:

J/ (hc)

D* D

D1

J/ Zc

J/

D* D

D1

Singularity kinematics in ee J/

Wang, Hanhart and Zhao, PLB2013; arXiv: 1305.1997[hep-ph]

(D1(2420) = 27 MeV

(D*0) = 190 keV

BESIII, 1303.5949[hep-ex]

“prediction” from a molecular Y(4260) in J/ decay


Prediction for Y(4260) hc with final state interactions

Q. Wang, C. Hanhart, and Q. Zhao, PRL111, 132003 (2013).

Singularity kinematics in Y(4170) J/psi

CLEO results

Q. Wang, C. Hanhart, and Q. Zhao, PLB725, 106 (2013).

Further test of the Y(4260) and Zc(3900) properties in the cross section line shape measurement

BESIII Belle

M. Cleven, Q. Wang, C. Hanhart, U.-G. Meissner, and Q. Zhao, 1310.2190.

D1D D1D

• Y(4260) couplings to D1D, D1D* and D2D* :

Lagrangians including combinations of spin doublets (D,D*) and (D1, D2) in the NREFT

• D1D*pi, D2Dpi and D2D*pi couplings:

Prediction for the anomalous cross section line shape

Data from Belle D1D D1D* D2D*

Invariant mass spectra for D, D*, and DD*

Signature for D1(2420) via the tree diagram.

The Zc(3900) could have a pole below the DD* threshold.

M. Cleven, Q. Wang, C. Hanhart, U.-G. Meissner, and Q. Zhao, 1310.2190.

Parameters fitted by the cross section lineshapes in J/psi pipi and hcpipi channel

• The puzzling Y(4260) may have a prominent D1D molecular component. • Given the existence of a pole structure for Zc(3900), its production will be driven by the low-momentum DD* scattering via “triangle singularity”. •The threshold phenomena explains the significant heavy quark spin symmetry breaking. • Experimental observations of those “threshold states” , e.g. Z(4430), Zb’s, and Zc’s, have significantly enriched the hadron spectroscopy which are beyond the simple qq picture. The study of the production mechanisms for those states will provide novel insights into the underlying dynamics. • … …

3. Some remarks

-- We are far from knowing the detailed properties of the strong QCD in hadron structure and hadron interactions. The observation of those “threshold states” expose another face of the strong QCD apart from the nuclear interaction.

3. Some remarks

-- We are far from knowing the detailed properties of the strong QCD in hadron structure and hadron interactions. The observation of those “threshold states” expose another face of the strong QCD apart from the nuclear interaction.

Seventh Asia-Pacific Conference on Few-Body Problems in Physics, APFB 2017, China

Date? Venue? …

Please come and enjoy!

Thanks for your attention!

new CDF meas.

new Belle meas.

MD0 + MD*0

3871.8±0.4 MeV

<MX>= 3871.46 ± 0.19 MeV

m = 0.35 ± 0.41 MeV

Observation of X(3872)

• The mass of X(3872) does not fit in (cc) 1++ state of quark model • Small mass difference to DD* threshold• Large isospin-violating decay modes • JPC = 1 is confirmed by LHCb

c c

c c

u

u u

u D0

D*0 D0

D*0

0

X(3872) as an analogue to the deuteron

• X(3872): D0D*0 with Isospin =0.• How about D0D*0 with Isospin =1? If YES, we will

have three states:

D0D*0 +c.c. : [cu uc]DD*0 +c.c. : [cd uc]DD*0 +c.c. : [cu dc]

Charged charmonium states!

qiang zhao institute of high energy physics, cas

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