Recent XYZ results from BESIII Jingzhi Zhang (IHEP) 2015.05.11 XYZ seminar

In 2013-2014, 4.6 fb-1 at 𝑺 >3.8 GeV collected At BESIII, intensive XYZ studies start from: In 2013-2014, 4.6 fb-1 at 𝑺 >3.8 GeV collected Fasten your seatbelt, let’s begin

Zc Zc±(3900) in e+e-p+p-J/y PRL 110,252001 Zc0(3900) in e+e-p0p0J/y paper in n preparation ZC±(4020) in e+e-p+p-hc PRL, 110, 252001 Zc0(4020) in e+e-p0p0hc PRL, 113,212002 Zc±(3885) in e+e-p(D*D)± PRL,112, 022001 single tag / double tag Zc±(4025) in e+e-p(D*D*)± PRL,112, 132001 Search for Zclight hadron prepare for publication

1. Observation of Zc±(3900) PRL 110 252001

CLEOc M = 388551 MeV  = 34124 MeV 81  20 events 6.1 M(π+π−J/ψ) = 4.17 M(π+π−J/ψ) = 4.26 (4.15 <M(π+π−J/ψ) < 4.45 ) CLEOc PLB 727, 366 (586 pb-1) PRL,111,252002 (967 fb-1) PRL,110,252001(525 pb-1) M = 388551 MeV  = 34124 MeV 81  20 events 6.1 M = 3894.56.64.5 MeV  = 632426 MeV 159  49 events >5.2 M = 3899.03.64.9 MeV  = 461020 MeV 307  48 events >8

2. Observation of Zc0(3900) in e+e- p0p0J/y Oberved Zc0(3900) signal. Simultaneous fit is performed to the π0J/ψ spectra at the ten energy points.

Simultaneous fit to the M(π0J/ψ) for 4230, 4260, 4360 MeV. Mass = 3894.8±2.3 MeV Width = 29.6±8.2 MeV Significance = 10.4 s Simultaneous fit to the M(π0J/ψ) for 4230, 4260, 4360 MeV. Signal: BW  3-Gaussian Bg: Argus function For detector resolution

e+e- p+p-hc Significant p+p-hc production reported by CLEO at 4170 MeV Correlated with Y(4260)? hc is spin singlet (s=0) state; J/y has spin=1 Explore p+p- transitions to hc as a function of E cm Search for p±hc states PRL,107,041803

3. Observation of Zc±(4020)p±hc in e+e- p+p-hc No sharp structure in p+p-hc cross section; correlation with Y(4260) is unclear Narrow p±hc structure observed M[Zc(4020)] =4023 ±3 MeV G[Zc(4020)] = 8±4 MeV No significant evidence for Zc(3900) p±hc at Ecm =4260 MeV s(e+e- p Zc(3900)  p+ p-hc) <10 pb s(e+e- p Zc(3900)  p+ p-J/y) = 13± 5 pb [ PRL, 110, 252001 ]

e+e- p0p0hc hcghc, hc-->hadrons [16 exclusive decay modes] pp, p+p-K+K-, p+p-pp, 2(K+K-), 2(p+p-), 3(p+p-), 2(p+p-)K+K-, KS0K+p-+c.c., KS0K+p-p+p-+c.c., K+K-p0, ppp0, K+K-h, p+p-h, p+p-p0p0, 2(p+p-)h, 2(p+p-p0), ~40% of hc decay _ _ _ Observe 219.6 p+p-hc The Ecms = 4.23, 4.26, 4.36 GeV (~2.5fb-1) PRL. 113, 212002

4. Observation of Zc0(4020)p0hc in e+e- p0p0hc The s(p0p0hc ) is consistent to be half of s(p+p-hc) within 2s s(p0p0hc )/s(p+p-hc) =0.63±0.9 Narrow p±hc structure observed M[Zc(4020)] =4023.3±2.2±3.8 MeV G[Zc(4020)] is fixed at 8 MeV No significant evidence for Zc(3900) p0hc Very likely the neutral isospin partner of the charged Zc(4020)

5. Observation of Zc± (3885)  (DD*) ± via e+e-  p±(DD*)∓ Single-tag technique Tag p-D+ Tag p+D0 1- 1+ 0- Using 525 pb-1 taken at Ecms = 4.26 GeV M[Zc(3885)] = 3884 ±4 MeV; G[Zc(3885)] =25±11MeV The p angular distribution establishes JP= 1+ If Zc(3885) is Zc(3900) , _ (𝑍𝑐(3900)→𝐷𝐷∗) (𝑍𝑐 3900 → 𝐽/ ) = 6.2 ± 2.9

Double-tag Simultaneous Fit 𝑒 + 𝑒 − →𝜋 + 𝐷 0 𝐷 ∗− 𝑒 + 𝑒 − →𝜋 + 𝐷 − 𝐷 ∗0 1090 pb-1@4.23GeV Signal: mass dependent width Breit-Wigner (BW) Background: Shape from PHSP MC 1090 pb-1@4.23GeV BW i m D D ∗ ∝ m D D ∗ Γ i m Z c 2 − m D D ∗ 2 −i 1 2 m Z c ( Γ 1 + Γ 2 ) , Where Γ i = Γ Z c q i ∗ q i 0 2l+1 ( m Z c m D D ∗ ) ( f l ( q i ∗ ) f l ( q i 0 ) ) 2 , the subscript i denotes the 𝑒 + 𝑒 − →𝜋 + 𝐷 0 𝐷 ∗− (i =1) and 𝑒 + 𝑒 − →𝜋 + 𝐷 − 𝐷 ∗0 (i = 2) processes. BESIII preliminary 827 pb-1@4.26GeV 827 pb-1@4.26GeV

Angular Distribution BESIII preliminary BESIII preliminary 𝑒 + 𝑒 − →𝜋 + 𝐷 0 𝐷 ∗− 𝑒 + 𝑒 − →𝜋 + 𝐷 − 𝐷 ∗0 BESIII preliminary BESIII preliminary Dots with error bars: Combined data at 𝒔 =4.23GeV and at 𝒔 =4.26GeV; Solid Lines: Fits to the data using 𝐽 𝑃 = 1 + ; Dashed curves: Fits to the data using 𝐽 𝑃 = 0 − ; Dotted curves: Fits to the data using 𝐽 𝑃 = 1 − ; The data agrees well with 𝑱 𝑷 = 𝟏 + and disagrees with 𝑱 𝑷 = 𝟎 − / 𝟏 − .

BESIII previous observation Double D tags BESIII previous observation 𝑀 pole (MeV/ 𝑐 2 ) 3884.3±1.2 𝑠𝑡𝑎𝑡. ±1.5 𝑠𝑦𝑠𝑡. 3883.9±1.5 𝑠𝑡𝑎𝑡. ±4.2 𝑠𝑦𝑠𝑡. Γ pole (MeV) 23.8±2.1 𝑠𝑡𝑎𝑡. ±2.6 𝑠𝑦𝑠𝑡. 24.8±3.3 𝑠𝑡𝑎𝑡. ±11.0 𝑠𝑦𝑠𝑡. 𝜎(𝑒 + 𝑒 − → 𝜋 ± 𝑍 𝑐 (3885) ∓ ) ×𝐵 𝑍 𝑐 (3885) ∓ → (𝐷 𝐷 ∗ ) ∓ 𝑍 𝑐 (3885) ∓ → (𝐷 𝐷 ∗ ) ∓ (pb) 88.0±6.1(𝑠𝑡𝑎𝑡.)±7.9(𝑠𝑦𝑠𝑡.)@4.26GeV 106.8±7.1(𝑠𝑡𝑎𝑡.)±9.5(𝑠𝑦𝑠𝑡.) @4.23GeV 83.5±6.6(𝑠𝑡𝑎𝑡.)±22.0(𝑠𝑦𝑠𝑡.)@4.26GeV PRL 112, 022001 (2014) The Results are consistent with but more precise than BESIII previous observation.

6. Observation of Zc±(4020) ( 𝐷 ∗ 𝐷 ∗ )± in e+e-→p±( 𝐷 ∗ 𝐷 ∗ )∓ at 𝑠 =4.26GeV Deviation from phase spde decay Could de described by a charged state decaying to 𝐷 ∗ 𝐷 ∗ M[Zc(4025)] =4026 ±3 MeV G[Zc(4025)] = 25±6 MeV Compare to p±hc structure M[Zc(4020)] =4023 ±3 MeV G[Zc(4020)] = 8±4 MeV0 If Zc(4025) ± is the Zc(4020), PRL,112,132001 (𝑍𝑐(4020)→ 𝐷 ∗ 𝐷 ∗ ) (𝑍𝑐 4020 →ℎ𝑐) = 12±5

Y(4360) p Y(4260) Zc±/0(4020) y(3S) p±/0 Zc±/0(3900) D*D* p±/0 DD*

7. No Zcwπ signals found in e+e- wπ π [BESIII Preliminary] [BESIII Preliminary] Fitting with acceptance weighted S-wave BW folded with Gaussian + ARGUS BGNo interference is considered 1094 pb-1 @4230 827 pb-1 @4260 The non-observation of Zc ω π (a typical decay mode of a 1+ resonance) may indicate that the annihilation of ccbar in Zc is suppressed.

u c c d Charged Zc+ charmonium-like state is smoking guns for exotic state with at least four quarks. Many proposals Hadronic molecules, arXiv:1303.6608, 1304.2882, 1304.1850 Tetraquark states arXiv:1110.1333, 1303.6857 arXiv:1304.0345, 1304.1301 Meson loop (arXiv:1303.6355) ISPE model (arXiv:1303.6842 ) Smoking guns for 4-quark states

X Y(4260) gX(3872) RPL,112,092001 X(3823) (𝝍( 𝟏 𝟑 𝑫 𝟐 )) arXiv:1503.08203 Some slides from Li Ke

e+e- gX(3872) Search for gX(3872) with X(3872) ppJ/y at Ecm=4.23, 4.26 and 4.36 GeV Left: summed over all data X(3872) significance = 6.3 s Production in Y(4260) decay suggestive, but not conclusive If from Y(4260) 𝐵(𝑌 4260 → g𝑋 3872 ) 𝐵(𝑌 4260 →p+−J/)  0.1 [BESIII RPL112,092001]

𝒆 + 𝒆 − → 𝝅 + 𝝅 − 𝑿, 𝑿→𝜸 𝝌 𝒄𝑱 , 𝝌 𝒄𝑱 →𝜸𝑱/𝝍 𝒆 + 𝒆 − → 𝝅 + 𝝅 − 𝑿, 𝑿→𝜸 𝝌 𝒄𝑱 , 𝝌 𝒄𝑱 →𝜸𝑱/𝝍 4.230 GeV 4.260 GeV 4.360 GeV 4.420 GeV 4.600 GeV Sum up arXiv:1503.08203

Simultaneous fit of 𝛾 𝜒 𝑐1 (left) and 𝛾 𝜒 𝑐2 (right) events 𝑀 𝑋 3823 = 3821.7±1.3(𝑠𝑡𝑎𝑡)±0.7(𝑠𝑦𝑠𝑡) MeV/ 𝑐 2 Γ 𝑋 3823 <16 MeV at 90% C.L. consist with Belle D-wave is expected. Limited statistics limited informations

X-section 𝝈 𝒆 + 𝒆 − → 𝝅 + 𝝅 − 𝑿 𝟑𝟖𝟐𝟑 ⋅𝓑(𝑿 𝟑𝟖𝟐𝟑 →𝜸 𝝌 𝒄𝟏 ) 𝜎 𝑒 + 𝑒 − → 𝜋 + 𝜋 − 𝑋 3823 ⋅ℬ(𝑋 3823 →𝛾 𝜒 𝑐1 ) 𝜎 𝑒 + 𝑒 − → 𝜋 + 𝜋 − 𝜓 ′ ⋅ℬ( 𝜓 ′ →𝛾 𝜒 𝑐1 ) = 0.20 −0.10 +0.13 (4.36 GeV) = 0.39 −0.17 +0.21 (4.42 GeV) ℬ 𝑋 3823 →𝛾 𝜒 𝑐2 ℬ(𝑋 3823 →𝛾 𝜒 𝑐1 ) <0.42 at 90% C.L. ≈0.24 (PRD 55,4001)

Y Cross section of 𝒆 + 𝒆 − →𝝅𝝅𝑱/𝝍 ( 𝒉 𝒄 ) e+e-  wcc0 PRL,114,092003 e+e-  h J/y arXiv:1503.06644 e+e-  h’J/y preliminary Search for Y(4140)f J/y via e+e-  g f J/y, f  K+K- /KSKL/p+p-p0 PRD 92,032002 e+e-  g ccJ at 𝒔 > 4GeV CPC, 39(4) (2015) 041001 Search for the isospin violating decay Y(4260)J/yηp0 arXiv: 1505.00539 Borrowed slides from Li Ke

1. Study the x-section of e+e-ppJ/y, pphc , DDp , DS(*)DS(*) The analyses are in progress.

2. Study of 𝝎 𝝌 𝒄𝟎 from 4.21 to 4.42 GeV 𝜔→ 𝜋 + 𝜋 − 𝜋 0 𝜔→ 𝜋 + 𝜋 − 𝜋 0 𝜒 𝑐0 → 𝐾 + 𝐾 − / 𝜋 + 𝜋 − 4.26 GeV 4.26 GeV

Simultaneous unbinned LH fit to 𝜋 + 𝜋 − / 𝐾 + 𝐾 − 4.23 GeV 4.26 GeV

Fit to 𝝈( 𝒆 + 𝒆 − →𝝎 𝝌 𝒄𝟎 ) Phase-space modified Breit-Wigner with significance >9𝜎 Γ 𝑒𝑒 ℬ 𝜔 𝜒 𝑐0 = 2.7±0.5 eV 𝑀 𝑌 = 4230±8 MeV/ 𝑐 2 Γ 𝑡 =(38±12) MeV Not consistent with Y(4260)𝜋𝜋𝐽/𝜓

3. Cross section of 𝐞 + 𝒆 − →𝜼𝑱/𝝍 4.23 GeV 𝜂→𝛾𝛾 𝐽/𝜓→ 𝜇 + 𝜇 − / 𝑒 + 𝑒 − 4.26 GeV

𝒆 + 𝒆 − →𝜼𝑱/𝝍 𝒆 + 𝒆 − →𝝅 𝟎 𝑱/𝝍 No signal No signal

Born cross section of 𝒆 + 𝒆 − →𝜼𝑱/𝝍 ?

4. Cross section of 𝐞 + 𝒆 − →𝜼′𝑱/𝝍 Preliminary 4.23GeV 4.26GeV Simultaneous fit to 𝜂 ′ →𝛾 𝜋 + 𝜋 − /𝜂 𝜋 + 𝜋 − , 𝐽/𝜓→ 𝜇 + 𝜇 − / 𝑒 + 𝑒 −

The cross-section

5. Search for Y(4140)f J/y f  K+K- PRD 92,032002 e+e-  g f J/y; J/y e+e-/m+m- f  K+K- Partial reconstruction, only require one K f  KSKL Partial reconstruction, only require KS; the KL not reconstructed. fp+p-p0 Full reconstruction.

           

Combine 6 modes ( 3 f modes  2 J/y modes)     eff. curve       Sum of all data sets  

No Y(4140) signal found @ BESIII Set upper limit at the 90% CL. for 𝜎 𝐵 ×ℬ= 𝜎 𝐵 𝑒 + 𝑒 − →𝛾𝑌 4140 ×ℬ(𝑌 4140 →𝜙𝐽/𝜓) 𝑠 (GeV/ 𝑐 2 ) Luminosity (pb-1) (1+𝛿) 𝜎 𝐵 ×ℬ 4.23 1094 0.840 <0.35 4.26 827 0.847 <0.28 4.36 545 0.944 <0.33 Systematic error included Compared with the 𝐗(𝟑𝟖𝟕𝟐) product ion 𝜎 𝐵 𝑒 + 𝑒 − →𝛾𝑋 3872 ×ℬ(𝑋 3872 → 𝜋 + 𝜋 − 𝐽/𝜓) Take ℬ 𝑋 3872 → 𝜋 + 𝜋 − 𝐽/𝜓 = 5%. arXiv: 0910.3138 And ℬ(𝑌 4140 →𝜙𝐽/𝜓) = 30%, molecular calculation, PRD 80, 054019. 𝜎 𝐵 ( 𝑒 + 𝑒 − →𝛾𝑌 4140 𝜎 𝑒 + 𝑒 − →𝛾𝑋 3872 ≤0.1 at 𝑠 =4.23 and 4.26 GeV.

6. Evidence for e+e−gccJ fit to M(gJ/y) Signal: a double-Gaussian with shape parameters determined from MC at 4260 MeV Background: radiative dimu MC shape Data: limited statistics is not consistent with being background 4009 4230 4260 4360

e+e−gccJ the statistical significance is 1.2σ, 3.0σ, 3.4σ for A simultaneous fit to M(gJ/y) at 4 CME points with assuming the production s(e+e− gccJ ) at different 𝑠 follows the lineshape of Y(4260) Fit to M(gJ/y) for summing the events in the 4 CME points cc2 cc1 cc0 cc2 cc1 the statistical significance is 1.2σ, 3.0σ, 3.4σ for cc0, cc1, cc2 respectively. the stat. significance is 0, 2.4, 4.0 s for cc0, cc1, cc2 , respectively

The measured Born corss-section s(e+e− gccJ ) ∎ ∎ ∎ s s s ∎ ∎ ∎ ∎ ∎ ∎ ∎ ∎ ∎ ∎ ∎ ∎ 𝑠 𝑠 𝑠 The upper limits on the cross section of e+e-  gccJ are compatible with the theoretical predication. Ref: arXiv:1310.8597

8. Search for Y(4260)J/yηp0 yields no signal Scatter Plot of M(gg) and M(l+l-) (combination closest to p0 and η) arXiv: 1505.00539

unanswered questions FROM Changzheng pi+pi-J/psi, there is dip at 4.17 GeV and a sharp increase at 4.23 GeV, we can know better where is the turning point; omega chi_c0, we are lack of data points close to threshold for claiming a narrow structure; KKJ/psi, seems there is a narrow structure at around 4.23 GeV; pi+pi-hc, there is a narrow structure at around 4.23 GeV; eta J/psi, line shape different from pi+pi-J/psi, peak at 4.23 GeV, but no data point on the left side; Zc(3900) production vs. Ecm, is the line shape of pi Zc the same as pi pi J/psi? eta hc, is there a structure at ~4.23 GeV? eta'J/psi close to threshold Are gamma chi_cJ signals from psi(4160) or Y(4260) or something else? Is gamma X(3872) from Y(4260) Search for F-wave states via psi(4160) decays? Gamma chi_c(2P), gamma XYZ(3940), X(3915) from psi(4160)? …. FROM Changzheng

Benefits from the 4.6 fb-1 data The data have attracted many colleagues from every physics group within BESIII (charmonium, light hadron, charm, QCD); Yielded very interesting results; Bring (experimentalist + theorist) together to have disccussions What’s the next? We deadly need more data at 𝒔 > 4 GeV high statistical scan: ~10 MeV Step ~500 pb-1/each

Summary Have listed the recent results on XYZ studies; some (not released) still in working progress. A few observations (7 PRL + x PRD + x talks….); seems lots more unanswered questions. A high statistical scan is desirable.

Y(4360) p Y(4260) g Zc±(4020) y(3S) p Zc±(3900) 3872 g D*D* DD*

The Zc states presented in last workshop Zc(3900) M(+J/) Zc(4020) M(+hc) PRL,111,252002 PRL, 110, 252001 Zc(3885) M(DD*) Zc(4025) M(D*D*) PRL,112,022001 PRL,112,132001