Exotic hadrons from BESIII Changzheng Yuan IHEP, Beijing (for the - PowerPoint PPT Presentation

Exotic hadrons from BESIII Changzheng Yuan IHEP, Beijing (for the BESIII Collaboration) Novosibirsk, May 21, 2018

Outline • The BESIII experiment • charmoniumlike states – The Y states — J PC =1 -- – The Z c states — I=1 & decays into  cc • Summary 2

Where is the BESIII experiment We are here! IHEP, Beijing 3

12km west from the Forbidden City Forbidden city Temple of Heaven 4

Bei eiji jing ng Ele lectr tron on Pos ositro itron n Col olli lide der (BEPC) EPC) • Founded: 1984 Ecm = 2-4.6 GeV • 1989-2005 (BEPC): L peak =1.0x10 31 /cm 2 s LINAC • 2008-now (BEPCII): L peak =1.0x10 33 /cm 2 s (Apr. 5, 2016) BEPCII (Beijing electron- positron collider) BESIII detector 5

BESIII Detector SC magnet, et, 1T 1T Magnet yoke RPC TOF, 80ps Be beam pipe MDC, 120  m Total weight 730 ton, 0.5% at 1 GeV/c ~40,000 readout chnls, Data rate: 5kHz, 50Mb/s CsI(Tl) calorimeter, 2.5% @ 1 GeV Has been in full operation since 2008, 6 all subdetectors are in very good status!

BESIII Collaboration 14 countries 64 institutions ~500 members 7

Can cover 0-4.6 GeV from direct annihilation or ISR 4190, 4200, 4210, 4220, 4236, 4245, 4270, 4280: 4230+4260 3.9 fb -1 J/  1.9 fb -1 5x10 9 8

Charmonium spectroscopy 4.8 Mass (GeV) S and D-wave spin-triplets have the same quantum number as the photon! 3 3 D (4.52) 1 4.4 3 3 1 2 D (4.22) 2 D (4.21) 2 D (4.21) 3 2 D (4.19) 3 2 2 1 3 3 3 3 3 S (4.10) 1 1 F (4.10) 1 F (4.09) 1 F (4.09) 1 F (4.09) 3 1 1 2 3 4 3 S (4.06) 0 3 2 P (3.98) 4 1 3 2 P (3.96) 2 P (3.95) 2 1 3 2 P (3.92) 1 0 3 3 1 1 D (3.85) 1 D (3.84) 1 D (3.84) 3 3 1 D (3.82) 2 2 D D 1 3 2 S (3.68) 1 1 2 S (3.62) 0 3.6 3 n (2S+1) L J 1 P (3.55) 1 3 2 1 P (3.52) 1 P (3.51) 1 1 3 1 P (3.44) 0 n radial quantum number S total spin of c & cbar 3.2 3 1 S (3.10) L orbital angular momentum 1 1 1 S (2.97) L = 0, 1, 2 ... correspond to S, P, D, … 0 J = S + L 2.8 P = ( – 1) L+1 parity -- -- -- -+ +- ++ ++ ++ -+ +- ++ ++ 0 1 1 0 1 2 2 2 3 3 3 4 9 C = ( – 1) L+S charge conj. Godfrey & Isgur, PRD32, 189 (1985)

Charmonium(like) spectroscopy 4.8 Mass (GeV) charged  Charmonium-like (XYZ) particles Y(4660) Z c (3900)  New type of hadron (multi- quark …)? 3 3 D (4.52) 1  (4415) Z c (4020)  Too many vector states! Exotics? 4.4 Z c (4430) Y(4360) 3 3 1 Y(4260) 2 D (4.22) 2 D (4.21) 2 D (4.21) 3 2 D (4.19) 3 2 2 1  (4160) 3 3 3 S (4.10) 3 1 1 F (4.10) 3 1 F (4.09) 1 F (4.09) 1 F (4.09) 3 1 1 2017 Belle 2 3 4 3 S (4.06)  (4040) 0 c c2 (2P) 3 2 P (3.98) 4 1 c c0 (2P) 3 2 P (3.96) 2 2015 BESIII 2 P (3.95) 3 1 2 P (3.92) 1 0  (1 3 D 2 ) 3 1 3 1 D (3.85) X(3872) 1 D (3.84) 1 D (3.84) 3 3 1  (3770) D (3.82) 2 2 1 D D h c (2S)  (2S) 3 2 S (3.68) 1 2005 1 2 S (3.62) 0 c c1 (1P) c c2 (1P) 3.6 3 1 P (3.55) 1 h c (1P) 3 2 1 P (3.52) 1 P (3.51) 1 1 c c0 (1P) 3 1 P (3.44) 0 1974 3.2 unpredicted, discovered J/  3 1 S (3.10) 1 h c (1S) 1 predicted, discovered 1 S (2.97) 0 2.8 -- -- -- -+ +- ++ ++ ++ -+ +- ++ ++ 0 1 1 0 1 2 2 2 3 3 3 4 10 Godfrey & Isgur, PRD32, 189 (1985)

The Y states measurements of more final states for the Y and  states 11

Belle: PRL99,142002, 670/fb The Y states BaBar: PRD89, 111103, 520/fb PRL110,252002 967/fb PRL101,172001 695/fb PRD86,051102 454/fb M(  c - ) +  c May y BESIII help? p? 12

e + e -   +  - J/ J/  at 4.26 GeV 882 882  33 33 595 595  28 28 J/    +  - J/   e + e - • Select 4 charged tracks and reconstruct J/  with lepton pair. • Very clean sample, very high efficiency (~45%). •  (e + e -   +  - J/  )= (62.9  1.9  3.7) pb 13 PRL110, 252001 (2013)

e + e -   +  - J/  cross section PRL118, 092001 (2017) data data 0.8 fb − 1 8.2 fb −1 103 points 19 points  Most precise cross section measurment to date from BESIII  Fit I =|BW 1 +BW 2 *e i f2 +BW 3 *e i f3 | 2 or Fit II =|exp+BW 2 *e i f2 +BW 3 *e i f3 | 2 (other fits ruled out) M = 4222.0 ± 3.1 ± 1.4 MeV (lower) G = 44.1 ± 4.3 ± 2.0 MeV (narrower) PDG 14

e + e -   +  - J/  cross section PRL118, 092001 (2017) data data 0.8 fb − 1 8.2 fb −1 103 points 19 points  Most precise cross section measurment to date from BESIII  Fit I =|BW 1 +BW 2 *e i f2 +BW 3 *e i f3 | 2 or Fit II =|exp+BW 2 *e i f2 +BW 3 *e i f3 | 2 (other fits ruled out)  M = 4222.0 ± 3.1 ± 1.4 MeV (lower)  G = 44.1 ± 4.3 ± 2.0 MeV (narrower)  A 2nd resonance Y 2 with M=4320.0 ± 10.4 ± 7.0 MeV/c 2 G =101.4 +25.3 -19.7 ± 10.2 MeV  Observed for the first time, significance > 7.6  15

e + e -   +  - h c (1P) (1P) • h c gh c , h c  hadrons [16 exclusive decay modes] • pp,  +  - K + K - ,  +  - pp, 2(K + K - ), 2(  +  - ), 3(  +  - ) • 2(  +  - )K + K - , K S 0 K +  - +c.c., K S 0 K +  -  +  - +c.c., K + K -  0 • pp  0 , K + K - h ,  +  - h ,  +  -  0  0 , 2(  +  - ) h , 2(  +  -  0 ) 3.2 50 E cm =4.415 GeV 160 E cm =4.415 GeV 140 40 3.1 ) 2 Events / ( 0.002 GeV/c 120 ) 2 (GeV/c 30 100 3.0 80 20 c h M 60 2.9 40 10 20 2.8 0 0 3.48 3.50 3.52 3.54 3.56 3.58 3.60 3.48 3.50 3.52 3.54 3.56 3.58 3.60 2 M (GeV/c ) 2 M (GeV/c ) h g h g c c Method same as in PRL111, 242001 (2013) 16

e + e -   +  - h c cross section PRL118, 092002 (2017) ~6 fb −1  First precise cross section measurement from threshold to 4.6 GeV  Fit with |BW 1 +BW 2 *e i f2 | 2 , two resonant structures are evident 17

e + e -   +  - h c cross section PRL118, 092002 (2017) ~6 fb −1 -4.5 ± 0.9 MeV/c 2 , G 1 = 66.0 +12.3  M 1 =4218.4 +5.5 -8.3 ± 0.4 MeV  Y(4220) -6.8 ± 1.0 MeV/c 2 , G 2 =139.5 +16.2  M 2 =4391.5 +6.3 -20.6 ± 0.6 MeV  Y(4390) 18

𝑓 + 𝑓 − → 𝜌 + 𝐸 0 𝐸 ∗− +c.c. • Reconstruct D 0 → K − π + • Select the combination closest to D 0 mass (m( D 0 )) • Find an additional π + ; • 1.9 < M(D ∗− ) (RM D 0 π + + M D 0 − m D 0 ) < 2.1 GeV/ c 2 • select the candidate closest to D ∗− mass • An un-binned maximum likelihood fit • Signal shape: MC convolved with a Gaussian; • The isospin partner background (dotted line) is parameterized with MC; • A linear function for other bkg 19

Fit to the dressed Xsection of 𝑓 + 𝑓 − → 𝜌 + 𝐸 0 𝐸 ∗− +c.c. 𝑂 𝑝𝑐𝑡 𝜏 𝑒𝑠𝑓𝑡𝑡 = ℒ 1 + 𝜀 𝑠 𝐶 𝐸 0 → 𝐿 − 𝜌 + 𝜁 Fit with a constant (pink dashed triple-dot line) and two constant width relativistic 20 BW functions (green dashed double-dot line and aqua dashed line).

Resonant parameters The error are statistical only.  Statistical significance is greater than 10  .  Consistent with those of Y(4220) and Y(4390) in 𝑓 + 𝑓 − → 𝜌 + 𝜌 − ℎ 𝑑 . 21

Imp mprov oveme ement nt of of e + e -   +  -  ’ PRD 96, 032004 (2017) 22

Signals at Ecm=4.416 GeV PRD 96, 032004 (2017) Mode I Mode II • Number of signals are extracted from π + π - J/ ψ invariant mass (mode I) and π + π - recoiled mass spectrum (mode II). • Signals are described with MC simulated shape convolved with a Gaussian function. 23

The Ys in e + e -   +  -  ’ arXiv:1703.08787, PRD 96, 032004 (2017) The Y(4220) is necessary (significance = 5.8  ) Fix parameters of the Y(4660) to Belle results 24

Y(4260)  Y(4220): what is it? Y(4220) appeared in 𝜕𝜓 𝑑0 , 𝜌 + 𝜌 − 𝐾/𝑞𝑡𝑗 , 𝜌 + 𝜌 −  ′ , 𝜌 + 𝜌 − ℎ 𝑑 , 𝐸 0 𝐸 ∗− 𝜌 + 25 Mass~4220 MeV, Width~ 60 MeV!

A coupled channel analysis By Jielei Zhang, Limin, Yuan, and Rumin Wang, arXiv:1805.03565 26

Leptonic width of Y(4220) For an isospin-zero charmoniumlike state, we expect Taking Solutions with the smallest 𝐶 × Γ 𝑓 + 𝑓 − , Γ 𝑓 + 𝑓 − > 36.4 ± 2.0 𝑡𝑢𝑏𝑢 ± 4.2 𝑡𝑧𝑡 eV More modes being measured:  charm rmed ed meson n pairs rs, , light ht hadron ons+ s+ h c 27 J. Zhang et al., arXiv:1805.03565

What is Y(4220)? • Hybrid? – Mass agrees with LQCD – Couples to e + e - weaker than conventional charmonium – Couples to spin-singlet strongly •  D 1 D molecule? – S-wave open threshold [BESIII will release  (e + e -   D 1 D) soon ] •  (4S) state? – Screened potential reduces 4S mass •  D s *D s * molecule? • c c0 molecule?  more data and more theoretical efforts 28

The Z c states 29

e + e -   +  - J/ J/  at at E cm cm =4 =4.26 26 GeV GeV 5 pb -1 data PRL110, 252001 (2013) 525 a at 4 4.260 60 GeV GeV 1595 events ts in J/  signal al region, n, purity~9 ty~90% 30