Mitglied der HelmholtzGemeinschaft Meson loop singularity exotic states

Mitglied der Helmholtz-Gemeinschaft Meson loop singularity, exotic states’ productions and decays near threshold Qian Wang In collaboration with Christoph Hanhart and Qiang Zhao Institut für Kernphysik Jülich Center for Hadron Physics, Forschungszentrum Jülich Email: q. wang@fz-juelich. de The 6 th International Workshop on Charm Physics, 31 Aug— 4 Sept 2013, Manchester, England.

Outline ØMotivations ØHadronic Molecules vs Tetraquark ØThe meson loop singularity ØSummary

Motivations Quark model Which combinations are favored? Conventional hadron Baryon Meson Molecule Tetraquark QCD allows baryons with Nquark>3 and mesons with Nquark>2 I should be at your position ! Hybrid Hadro-quarkonium 2021/12/18 And so on…… 3 see talks by Braaten, Fernandez and Thomas

N. Brambilla et al. Eur. Phys. J. C 71, 1534(2011) Exotic Candidates X(3872) No matter what their natures are, they cannot be described without considering threshold effects. G(3900) Y(4260) Zb(10610), Zb(10650) Zc(3900), Zc(4025) Z(4430) 2021/12/18 4

Zb(10610) and Zb(10650) are most likely to be molecular states. • Molecule: Zb BB* and Zb’ B*B* ✔ Tetraquark: Zb B*B* and Zb’ BB* ✗ • BB* and B*B* are their dominant decay modes. • There may be the corresponding molecular states in charmonium sector. Belle, 1209. 6450(2012), M. Cleven et al. Eur. Phys. J. A 47, 120 (2011), M. Cleven et al. Phys. Rev. , D 87, 074006(2013), A. Ali et al. Phys. Rev. , D 85, 054011(2012), Wei Wang’s talk at QWG 2013, Li and Voloshin, PRD 077502(2012) 2021/12/18 5

Obervation of Zc(3900) BESIII, PRL 110, 252001(2013) hep-ex/1304. 3036 CLEO-c Belle, PRL 110, 252002(2013) See talks by Yuan and Liu

Y(4260) D 1 D molecular state and Zc(3900) DD* molecular state 2021/12/18 BESIII, PRL 110, 252001(2013), Wang et al, hep-ph/1303. 6355, Wang et al. , PLB 725, 106(2013) 7

The meson loop singularity D 1 D cut Diagram (a) and Diagram (b) D 1 D* cut Diagram (c) and Diagram (d) Since the mass difference between D and D* is about 140 Me. V, there is no overlap between these two singularity regions.

D*D* cusp DD* cusp To illustrate the cusp and singularity effect, we give the J/Ψπ invariant mass distribution in the e+e- to J/Ψππ process at c. m. energy 4. 43 Ge. V. Here the line shape of Zc before and after considering the width of the intermediate mesons are listed to illustrate the effect of the widths. Wang et al. , PLB 725, 106(2013)

Summary Ø Y(4260) looks more likely to be D 1 D molecular state and Zc(3900) is dominant by the DD* molecular component. Ø The main decay mode of Y(4260) should be D*Dπ due to its D 1 D molecular nature. Ø The observation of Zc at the c. m. energy 4. 17 Ge. V further favors Zc’s existence as a genuine state. Ø Further experimental measurements of Zc and Zc’ decays will help us to confirm their natures.

THANK YOU FOR YOUR ATTENTION

Discussion about Zc and Zc’ 2021/12/18 12

The mass position Zb and Zb’ are close to the corresponding thresholds, but the case is different in charmonium sector. Why? v Heavy quark symmetry is broken largely in charmonium sector. v The line shape of Zc is much dependent on the incoming energy. v There may be additional component in Zc’s wave function other than DD* molecule. Belle, 1209. 6450(2012); BESIII, PRL 110, 252001(2013), 1308. 2760; Belle, PRL 110, 252002(2013); CLEOc, hep-ex/1304. 3036. 2021/12/18 13

The total width Heavy quark symmetry How to understand their widths? v Heavy quark symmetry is broken largely in charmonium sector. v The line shape of Zc is much dependent on the incoming energy. v There may be additional component in Zc’s wave function other than DD* molecule. Belle, 1209. 6450(2012); BESIII, PRL 110, 252001(2013), 1308. 2760; 2021/12/18 Belle, PRL 110, 252002(2013); CLEOc, hep-ex/1304. 3036. 14

The decay pattern of Zb and Zb’ indicate they look like to be molecular states. How about Zc and Zc’? To be answered by BESIII and Belle! Belle, 1209. 6450(2012); BESIII, PRL 110, 252001(2013), 1308. 2760; Belle, PRL 110, 252002(2013); CLEOc, hep-ex/1304. 3036. 2021/12/18 15

Yuan’s talk 2021/12/18 16

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BESIII, 1308. 2760 2021/12/18 18

Some comments on Phys. Rev. D 88, 034012(2013) 2021/12/18 19

• The decomposition of Y(4260) • HQSS breaking from vector meson’s di-electron decay width. Badalian et al. , Phys. Atom. Nucl. 72, 638 (2009) • J/ψππ is expected to have the largest cross section in hardro-charmonium scenario. 2021/12/18 20

• The decay of Y(4260) in D 1 D’s molecular scenario. 2021/12/18 21

Back Up 2021/12/18 22

The above discussion can be simply extended to bottomonium sector. The left hand side figure is B 1 B singularity region and the right hand side is B 1 B* singularity region. Since the mass difference between B* and B is about 1/3 of that in the charmed sector, there is an overlap between these two singularity regions.

Neither B*B nor B*B* singularity behavior can be found at the Upsilon(5 S) mass energy. Both of them can be found in the Upsilon(6 S) mass energy. Ø The newly observed Zb(10610) and Zb(10650) are indeed needed to explain the Upsilon(n. S)π invariant mass distribution at the Upsilon(5 S) center energy. Ø The measurements of Zb(10610) and Zb(10650) at Upsilon(6 S) are necessary to confirm this threshold.

Systematic study of singularity and its applications After considering the widths of the intermediate D 1 and D*, the singularity region become smaller.

Systematic study of singularity and its applications Since 4. 16 closes D*D* threshold, even D*D* cut can not give the singularity behavior at DD* threshold. That means Zc does indeed exist.