Yukawa Institute for Theoretical Physics
February 15th - March 21st 2015

Highlights on BESIII recent results
Marco Maggiora
BESIII Collaboration
Department of Physics and INFN – Turin, Italy

BESIII Collaboration
http://bes3.ihep.ac.cn

Pakistan (2)Univ. of Punjab
COMSAT CIIT

Korea (1)Seoul Nat. Univ.

US (6)
Univ. of Hawaii
Univ. of Washington
Carnegie Mellon Univ.
Univ. of Minnesota
Univ. of Rochester
Univ. of Indiana

Japan (1)Tokyo Univ.

China(30)Europe (13)Germany: Univ. of Bochum,
Univ. of Giessen, GSI
Univ. of Johannes Gutenberg
Helmholtz Ins. In Mainz
Russia: JINR Dubna; BINP Novosibirsk~350 members
53 institutions
11 countries
Feb 15 - Mar 21, 2015

Italy: Univ. of Torino，

Frascati Lab, Univ. of Ferrara
Netherland：KVI/Univ. of Groningen
Sweden: Uppsala Univ.
Turkey: Turkey Accelerator Center

HHIQCD2015

IHEP, CCAST, GUCAS, Shandong Univ.,
Univ. of Sci. and Tech. of China
Zhejiang Univ., Huangshan Coll.
Huazhong Normal Univ., Wuhan Univ.
Zhengzhou Univ., Henan Normal Univ.
Peking Univ., Tsinghua Univ. ,Zhongshan Univ.,Nankai Univ.
Shanxi Univ., Sichuan Univ., Univ. of South China
Hunan Univ., Liaoning Univ.
Nanjing Univ., Nanjing Normal Univ.
Guangxi Normal Univ., Guangxi Univ.
Suzhou Univ., Hangzhou Normal Univ.
Lanzhou Univ., Henan Sci. and Tech. Univ.
Hong Kong Univ., Hong Kong Chinese Univ.

2

BEPCII
RF

RF

Compton back-scatteringfor high precision beamenergy measurement

22

2.5m

mra

d

m
0.1c

8ns

BESIII is here

Feb 15 - Mar 21, 2015

IP HHIQCD2015

1.5cm

Beam energy:
1-2.3 GeV
Crossing angle:
22 mradDesign Luminosity:
1×1033 cm-2s-1
Optimum energy:
1.89 GeV
Energy spread:
5.16 ×10-4
No. of bunches:
93
Bunch length:
1.5 cmTotal current:
0.91 A
SR mode:0.25A @ 2.5 GeV
3BESIII Spectrometer

SC magnet, 1T
Magnet yoke
RPC

TOF, 90ps
Be beam pipe
MDC, 130 m
0.5% at 1 GeV/c

Total weight 730 ton,
~40,000 readout chnls,
Data rate: 5kHz, 50Mb/s

CsI(Tl) calorimeter, 2.5% @ 1 GeV
Feb 15 - Mar 21, 2015

HHIQCD2015

4

BESIII data set
2.9 fb-1 / 20 fb-1
0.6 B / 3 B (106 M)

1.3 B / 10 B (225 M)

Feb 15 - Mar 21, 2015

HHIQCD2015

5

BESIII data set
2.9 fb-1 / 20 fb-1

10  20 x

0.6 B / 3 B (106 M)

previous generation charm factories

1.2 B / 10 B (225 M)

Feb 15 - Mar 21, 2015

HHIQCD2015

6

BESIII production of Charmonium(like) states

From PDGBEPCII can reach here!
Feb 15 - Mar 21, 2015

HHIQCD2015

7

BESIII production of Charmonium(like) states
1.3 X 109

6 X 1083773
2.9 fb-1

4040
0.5 fb-1

4415
1 fb-14600
0.5 fb-1

From PDG

4230  4260
2.3 fb-1• 3554 MeV: 0.024 fb-1  mass
BEPCII can reach here!
-1• 4100  4400 MeV: 0.5 fb coarse scan
• 3850  4590 MeV: 0.5 fb-1 fine scan
Feb 15 - Mar 21, 2015

HHIQCD2015

4360
0.5 fb-1

8

J/ → γηη
PRL 48, 458 (1982)• first studied by
Crystal Ball (1982):
f0(1710)• Crystal Barrel (1995):
f0(1500) [pp→π0ηη]• E835 (2006):
f0(1500) [pp→π0ηη]f0(1710) [pp→π0ηη]• WA102, GAMS:
f0(1500) [ηη mode]

Feb 15 - Mar 21, 2015

PLB 353, 571 (1995)

HHIQCD2015

9

BESIII: PWA of J/ → γηη, η → γγ

PRD 87, 092009

 best solution:• f0(1500),f0(1710), f0(2100);f2(1525), f2(1810), f2(2340);
0++ phase space, ϕη no significant evidence of:• scalar:f0(1370), f0(1790), f0(2020),
f0(2200), f0(2330)• tensor:f2(2010), f2(2150), fJ(2220)
source of sys. unc.

 ϕη background:• interference of ϕ tail accounted for• source od systematic uncertainties
Feb 15 - Mar 21, 2015

HHIQCD2015

10

BESIII: PWA of J/ → γηη, η → γγ

PRD 87, 092009

no significant evidence of:• scalar: f0(1370), f0(1790), f0(2020), f0(2200), f0(2330)• tensor: f2(2010), f2(2150), fJ(2220)
Feb 15 - Mar 21, 2015

HHIQCD2015

11

J/ → γωϕ• doubly OZI suppressed

→γωϕ (DOZI) predicted  1/10
• BESII:[PRL 96, 162002]

→γϕϕ (OZI)
2
M = (1812+19
±18)
MeV/c
-26

 = (105±20±28) MeV/c2

0++ favoured over
0-+ and 2++
Feb 15 - Mar 21, 2015

HHIQCD2015

12

BESIII: PWA of J/ → γωϕ

PRD 87, 032008

 looking for best solution:• M,  and JPC of X(1810)• other know mesons [PDG]• different JPC of phase space• different combinations ofadditional mesons [PDG] best solution:X(1810), f0(2020),f2(1950),
η(2225), f0(2020), phase spaceand background systematic uncertainties:• f2(1920), f0(2020), η(2225):
standard deviation from PDG,
replacing by other of similar
mass but same JPC• model dependence
Feb 15 - Mar 21, 2015

HHIQCD2015

13

BESIII: J/ → γX(1810), X(1810) → ωϕ PRD 87, 032008
 X(1810) resonance parameters:2
M = 1795±7(stat)+13(sys)±19(mod)
MeV/c
-5
2
 = 9510(stat)+21(sys)75(mod)
MeV/c
-34

B(J/ → gX(1810)) x B(X(1810) → ωϕ) =(2.00±0.08(stat)+0.45(sys)±1.30(mod))×10-4-1.00

 confirmed @ BESIII: best solution:
JPC = 0++ X(1810) vs f0(1710):
unconclusive, further investigation is needed search for X(1810):• in other decay modes: K*K*, ωω, …
[J/→γη(1760), η(1760)→ ω ω observed by BESII: PRD 73, 112007]• in other production processes: J/→ϕωϕ, J/→ωϕω
Feb 15 - Mar 21, 2015

HHIQCD2015

14

J/ → γpp: enhancement at thresholdnormal meson? pp bound state? multiquark? glueball? FSI effect?
BESIII: CPC 34 , 421 (2010)

BESII: PRL 91, 022001 (2003)+52
M = (1860+3-10 -25 ) MeV/c
 < 38 MeV/c2 (90% C.L.)
compatible with S-wave BW+72
M = (1861+6-13 -26 ) MeV/c
 < 30 MeV/c2 (90% C.L.)
compatible with S-wave BW

Spin-parity analysis essential to determine nature and role in spectrum
Feb 15 - Mar 21, 2015

HHIQCD2015

15

BESIII: PWA of J/ → γpp, Mpp<2.2 GeV PRL 108, 112003
 PWA of J/ → γpp :• never performed before
 best solution:
X(pp) [>>30σ], f2(1910)
and f0(2100) fixed @PDG,
0++ phase space andS-wave (I=0) FSI
 systematic uncertainties:• f2(2150), f2(1950), and otherresonances from PDF, 0-+ PS• FSI model dependence
JPC= 0-+ , >6.8σ better than other JPC assignments
+19

+18

M = 1832 -5 (stat) -17 (sys)±19(mod) MeV/c2
2 or <76 MeV/c2 (90% C.L.) = 1339(stat)+10(sys)4(mod)
MeV/c
-13
+1.5
-5
B(J/→gX(pp)) x B(X(pp)→pp) = 9.0+0.4(stat)(sys)±2.3(mod))×10
-1.1
-5.0

Feb 15 - Mar 21, 2015

HHIQCD2015

16

BESIII: J/ → γX(1835), X(1835) → π+π-’ PRL 106, 072002
X(1835):2
M = (1836.5  3.0+5.6-2.1 ) MeV/c2
Γ = (190  9 +38-36 ) MeV/c>20
X(2120):2
M = (2122.4  6.7+4.7-2.7 ) MeV/c2
Γ = (83  16 +31-11 ) MeV/c>7.2
X(2370):• PWA is needed
+3.2
2
M
=
(2376.3

8.7
to determine spin and parity-4.3 ) MeV/c• consistent with JP = 02
Γ = (83  17 +44-6 ) MeV/c>6.4
Feb 15 - Mar 21, 2015

HHIQCD2015

17

BESIII: J/ → γX(1840), X(1840) → 3(π+π-) PRD 88, 091502

phase space2
M = (1842.2  4.2+7.1-2.6 ) MeV/cΓ = (83  14  11 ) MeV/c2>7.6

• PWA is needed to determine spin and parity• no ’ detectedFeb 15 - Mar 21, 2015

HHIQCD2015

18

BESIII: J/ → X(1870), X(1870) → a(980)πPRL 107, 182001

J/ → π+π-X(1870):2
M = (1877.3  6.3+3.4-7.4 ) MeV/c2
Γ = (57  12 +19-4 ) MeV/c-4
B = (1.50  0.26 +0.72-0.36 )  10

(1405):+2.8
M = (1399.8  2.2 -0.1 ) MeV/c22
Γ = (52.8 7.6 +0.1
-7.6 ) MeV/c-4
B = (1.89  0.21 +0.21-0.23 )  10

• PWA is needed
to determine spin and parity

f1(1285):2
M = (1285.1  1.0+1.6-0.3 ) MeV/c2
Γ = (22.0  3.1 +2.0
-1.5 ) MeV/c-4
B = (1.25  0.10 +0.19
)

10
-0.20

Feb 15 - Mar 21, 2015

HHIQCD2015

19

BESIII: a partial summary

𝒑𝒑 threshold

X(1840): J/ → γ3(π+π-) [PRD88, 091502]
X(1870): J/ → π+π- [PRL107, 182001]
X(1835): J/ → γ(π+π-) [PRL106, 072002]
X(1840): J/ → γ(p𝐩) [PRL108, 112003]
X(1840): J/ → γ() [PRD87, 032008]
Feb 15 - Mar 21, 2015

HHIQCD2015

20

BESIII: a partial summary• J/ radiative decays• not found in ’radiative decays• non a pure FSI• PWA is needed
𝒑𝒑 threshold

X(1840): J/ → γ3(π+π-) [PRD88, 091502]
X(18??):+
X(1870): J/ → π π [PRL107, 182001]• near (p𝒑) threshold+X(1835): J/ → γ(π π ) [PRL106, 072002]• is a single particle?!?
X(1840): J/ → γ(p𝐩) [PRL108, 112003]
X(1840): J/ → γ() [PRD87, 032008]
Feb 15 - Mar 21, 2015

HHIQCD2015

21

BESIII: PWA of (2S) → γpp, Mpp<2.2 GeV

PRL 108, 112003

pp mass-spectrum at threshold clearly differs from that in J/ decays

M, , and JPC fixed to those obtained for J/ decays

B((2S)→gX(pp)) x B(X(pp)→pp) =-64.57±0.36(stat)+1.23(sys)±1.28(mod))×10
-4.07

R =

B((2S) → γX(pp))
+0.71
+0.67
= 5.08 -0.45(stat) -3.58(sys)±0.12(mod))%<12%!
B(J/ → γX(pp))

Feb 15 - Mar 21, 2015

HHIQCD2015

22

PWA of (2S)→ppπ0 and (2S) →ppηCLEOc: 24.5 M (2S) [PRD 82, 092002]
(2S)→ppπ0

(2S) →ppηFeb 15 - Mar 21, 2015

1.
2.
3.
4.

R1(2100)
N(1440)N(2300)R2(2100)

1.
2.

N(1535)R(2100)HHIQCD2015

23

BESIII: PWA of (2S) → ppη

PRD 88, 032010

 low background:• sidebands and continuum

 best solution:
N(1535) combined with aninterfering phase space
 pp enhancement:<3σ N(1535):
2• M=(1524±5+10
)
MeV/c
-4
2
• = (130+27+10)
MeV/c-24 -10
 suppressed (<12%):Qppη =
Feb 15 - Mar 21, 2015

B((2S) → ppη)
B(J/ → ppη)

= (3.2±0.46)%

HHIQCD2015

24

BESIII: PWA of (2S)→ppπ0

PRL 110, 022001

 2-body decay:• (2S)→Xπ0, X→pp• (2S)→pN*, N*→pπ0+c.c.
 isospin conservation:
Δ suppressed best solution:
N(1440), N(1520), N(2090), N(1535),
N(1650), N(1720),
N(2300) [1/2+], N(2570) [5/2-]
 no significant evidence:• N(1885), N(2065)• pp enhancement
 systematic uncertainties:• additional possible resonances
Feb 15 - Mar 21, 2015

HHIQCD2015

25

BESIII: PWA of (2S)→ppπ0

PRL 110, 022001

 2-body decay:• (2S)→Xπ0, X→pp• (2S)→pN*, N*→pπ0+c.c.
 isospin conservation:
Δ suppressed best solution:
N(1440), N(1520), N(2090), N(1535),
N(1650), N(1720),
N(2300) [1/2+], N(2570) [5/2-]
 no significant evidence:• N(1885), N(2065)• pp enhancement
 systematic uncertainties:• additional possible resonances
Feb 15 - Mar 21, 2015

HHIQCD2015

26

BESIII: PWA of (2S)→ppπ0

PRL 110, 022001

 branching fraction:
B((2S) → ppπ0) = (1.65±0.03±0.15)×10-4
 PWA:• two new resonances• N(1885) and N(2065), <5σ• pp resonance <4σ•

1/2+

5/2Feb 15 - Mar 21, 2015

HHIQCD2015

27

(2S) → γηc(1S), γηc(2S)ηc mass:
charmonium
ground state

hadrons

M1 transition:
first observation of
ψ’ → γη’c
hadrons
Feb 15 - Mar 21, 2015

HHIQCD201528

ηc(1S)The S-wave spin-singlet charmonium ground state, found in 1980

M &  measurements:••

J/ radiative transitions: M ~ 2978.0 MeV/c2,
 ~ 10 MeV/c2
gg processes / BKc: M = (2983.1±1.0) MeV/c2,  = (31.3±1.9) MeV/c2_

gg, pp, B decay
Mass(1S, 2S)gc

Width

C.L.=0.0014
Feb 15 - Mar 21, 2015

HHIQCD2015

C.L.<0.0001
29

BESIII: (2S) → γηc(1S)

PRL 108, 222002 (2012)

KsKp

K+K-p0

p+p-

KsK3p

2K2pp06p

Significant interference between c and non-resonant→ simultaneous fit to 6 modes, Mass = 2984.3±0.6±0.6 MeV/c2
 = 32.0±1.2±1.0 MeV/c2
Feb 15 - Mar 21, 2015

HHIQCD201530

ηc(1S): BESIII vs literature
Mass

PRL 108, 222002 (2012)
BESI
II(earlier result -- ~117 MeV)

Hyperfine splitting (BESIII alone)M(1S) = 112.5±0.8 MeV/c2

Closer to prediction
then earlier result
Feb 15 - Mar 21, 2015

Lattice 2012, arVix:1211.2253

HHIQCD201531ηc(2S)
Observed in different production mechanisms
1.
2.
3.

Belle: PRL 89 102001 (2002)
B → Kc’
CLEOc: PRL 92 142001 (2004)
gg → c’ → KKp
Belle: NPPS.184 220 (2008); PRL 98 082001(2007)
PRL 92 142002 (2004); PR D72 031101(2005)
double charmonium production BaBar:
BaBar: PR D84 012004 (2011)

M1 transition  → γηc
1. CLEO found no signal in 25M ’.
B(’ → gc’) < 7.6×10-4

PRD 81 052002 (2010)

2. BESIII: first observation of c’ → KKp ;find evidence in c’ → KsK3p
Experimental challenge : search for photons of 50 MeV

Feb 15 - Mar 21, 2015

HHIQCD2015

32

BESIII: (2S) → γηc(2S), ηc(2S) → KKπ

PRL 109, 042003

M = 3637.6±2.9±1.6 MeV/c2
 = 16.96.44.8 MeV/c2
B(  → gc → gKKp)=(1.30±0.20±0.30) ×10-5
Significance >10 
B(c → gKKp)=(1.9±0.4±1.1)%

BABAR: PRD78, 012006 (2008)

B(' → gc) = (6.8±1.1±4.5) ×10-4
FIRST OBSERVATION!
Potential model:(0.1-6.2)10-4 PRL89, 162002(2002)
CLEOc:< 7.610-4
PRD81, 052002 (2010)
Feb 15 - Mar 21, 2015

HHIQCD2015

33

BESIII: (2S) → γηc(2S), ηc(2S) → KsK3π

PRD 87, 052005

Significance
4.2 

M = 3646.9±1.6±3.6 MeV/c2
 = 9.24.82.9 MeV/c2
B(' → gc → gKsK3p) = (7.03±2.10±0.70)×10-6
Feb 15 - Mar 21, 2015

HHIQCD201534

ηc(2S): BESIII vs literature

Feb 15 - Mar 21, 2015

HHIQCD2015

PRL 109, 042003
PRD 87, 052005

35

hc(1P)• Spin singlet P wave (S=0, L=1)
• Potential model: if non-vanishing P-wave spin-spin interaction,Mhf(1P)=M(hc) - <M(1 3PJ)>  0,
<M(1 3PJ)> = [M(cc0)+3M(cc1)+5M(cc2)]/9• Theoretical predictions:– B(  p0hc) = (0.4-1.3)10-3,– B(hc  gc) = 38%

B(hc  gc) = 41% (NRQCD)
B(hc  gc) = 88% (PQCD)
Y. P. Kuang, PR D65, 094024 (2002)
Godfrey and Rosner, PR D66, 014012 (2002)• First reported by E760 in decay pp → hc → J/p0 , not confirmed
Evidence found by E835 in pp → hc → gc
PR D72 032001 (2005)• Observed by CLEO in  → p0hc, hc → gc• Recent results from BESIII
Feb 15 - Mar 21, 2015

HHIQCD2015

PRL 95 102003 (2005)

36

BESIII: (2S) → π0hc(1P), hc(1P) → γηc(1S)

PRL 104, 132002“inclusive”
only detect the p0(compute M(hc) from kinematic)

Rate ∝ B(→p0hc)“E1 tagged”
detect the p0 & g
Rate∝B(→p0hc) ×B(hc→gc)“exclusive”

hadrons
Feb 15 - Mar 21, 2015

detect the p0, g & c→Xi decay prod.
Rate ∝
B(→p0hc) ×B(hc→gc) ×B(c →Xi )HHIQCD2015

37

BESIII: (2S) → π0hc(1P), hc(1P) → γηc(1S)

PRL 104, 132002

M = 3525.40±0.13±0.18 MeV/c2
 = 0.73±0.45±0.28 MeV/c2<1.44 MeV @90%
CLEOc:

PRL 101 182003 (2008)

M = 3525.28±0.19±0.12 MeV/c2
 : fixed at 0.9 MeV
Hyperfine mass splittingMhf(11P)= M(hc ) - <m(13PJ )>BESIII: 0.10±0.13±0.18 MeV/c2
CLEOc: 0.02±0.19±0.13 MeV/c2

By combining inclusive results with E1-photon tagged results
B(' → p0 hc ) = (8.4±1.3±1.0) ×10-4
B(hc → g c) = (54.3±6.7±5.2)%
Feb 15 - Mar 21, 2015

HHIQCD2015

Agrees with prediction from
Kuang, Godfrey, Dude et al.
38

BESIII: 16 hc(1P) decay modes (40% ηc(1S) decays)

PRD 86, 092009

Summed distribution
832±35 evts.

(MeV/c2)

BESIII Exclusive

BESIII Inclusive

CLEO

M

3525.31±0.11±0.143525.40±0.13±0.183525.21±0.27±0.14



0.70±0.28±0.22

0.73±0.45±0.28--

Mhf(1P)-0.010.11 0.15

0.10±0.13±0.18

0.08 0.18 0.12

BESIII: PRL 104 132002 (2010)
CLEOc: PRL 101 182003 (2008)
Feb 15 - Mar 21, 2015

HHIQCD2015

39

BESIII: ηc parameters from (2S) → π0hc(1P), hc(1P) → γηc(1S)

PRD 86, 092009

Sum of 16 of
C decay modes

Backgroundsubtracted

c lineshape in hc → gc is not as distorted as in  → gc decays: non-resonant interfering background is smaller than  → ghc
 this channel best suited to determine c resonance parameters
PRL 108, 222002

 → π0hc, hc → γηc → γηc

M = 2984.49±1.16±0.52 MeV/c2
 = 36.4±3.2±1.7 MeV

M = 2984.3±0.6±0.6 MeV/c2
 = 32.0±1.2±1.0 MeV

Consistent results, but still dominant statistical errors: more statistics is needed!
Feb 15 - Mar 21, 2015

HHIQCD2015

40

BELLE: X(3823)• using 772 · 106 BB̅
• B → K gcc1

M = (3823.1±1.8±0.7) MeV/c2
3.8
Mass and width compatible with a ψ2(13D2) state
Feb 15 - Mar 21, 2015

HHIQCD2015

41

BESIII: e+e- → π+π-X(3823) → π+π-γ cc1

BESIII preliminary

Simultaneous fit to two data set:
• Data-1
 4.36 GeV/c2• Data-2:[4.23,4.26] GeV/c2

M = (3821.7±1.3±0.7) MeV/c2
6.7
Feb 15 - Mar 21, 2015

HHIQCD2015

42

BESIII: e+e- → π+π-X(3823) → π+π-γ cc1

Feb 15 - Mar 21, 2015

HHIQCD2015

BESIII preliminary43

Higher Charmonium states: a new family member?

Feb 15 - Mar 21, 2015

HHIQCD2015

44

BESIII: e+e- → γX(3872) → γπ+π-J/

PRL 112, 092001

Clear ISR ’ signal for data validation
X(3872) signal at around 4.230-4.260 GeV

Feb 15 - Mar 21, 2015

Ecm=4.010 GeV

Ecm=4.230 GeV

Ecm=4.260 GeV

Ecm=4.360 GeV

HHIQCD2015

45

BESIII: e+e- → γX(3872) → γπ+π-J/

PRL 112, 092001

ISR ’ signal is used for rate, mass, and mass resolution calibration.
μψ(3686) = - (0.340.04) MeV/c2; M= (1.140.07) MeV
N(X(3872)) = 20.1±4.5
M = (3871.9±0.7±0.2) MeV/c2
 = <2.4 MeV/c2 with 90% CL[PDG: 3871.68±0.17 MeV]
Could be a Y(4260) → γX(3872)!
σ(Y(4260) → γX(3872))

R = σ(Y(4260) → π+π-J/ψ)Feb 15 - Mar 21, 2015

HHIQCD2015

 11%
46

BESIII: e+e- → γϕJ/ψ (J/ψ → μ+μ-, e+e-)

PRD 91, 032002

 3 ϕ decay modes considered: ϕ → K+K-, ϕ → KSKL , ϕ → π+π-π0 2 J/ψ decay modes considered: J/ψ → μ+μ-, J/ψ → e+eEcm=4230, 4260, 4360 MeV
Preliminary

No evidence of Y(4140)
UP @ 90% C.L. forσB(e+e- → γY(4140) · B(Y(4140) → γϕJ/ψ)Ecm (MeV)

L (pb-1)

σB · B

4.23

1094< 0.354.26

827< 0.284.36

545< 0.33

Including systematic uncertainties

Assuming: B(X(3872) → π+π- J/ψ) = 5% [2] σB(e+e- → γX(3872) · B(X(3872) → π+π- J/ψ) [1]:
 Ecm=4230 MeV: 0.27  0.09 (stat.)  0.02 (syst.) pb  B(Y(4140) → ϕ J/ψ) = 30% [3] Ecm=4260 MeV: 0.33  0.12 (stat.)  0.02 (syst.) pb

σ( e+e-→ γY(4140) )R = σ( e+e- → γX(3872) ) ≤ 0.1 @ 4230/4260 MeV
Feb 15 - Mar 21, 2015

HHIQCD2015[1] PRL 112, 092001[2] arXiv:0910.3138[3] PR D80, 054019

47

Exotic at BESIII• all states below DD thresholdhave been observed and describedby charm anti-charm potentialmodel• only a few of the predicted states
above threshold have been found• many new states have been observed:• some unexpected• many with properties notconsistent with charmonium
decays to X,Y or Z states
Feb 15 - Mar 21, 2015

HHIQCD2015

48

BESIII: e+e- → π+π-J/ events
TypicalJ/ →+-Feb 15 - Mar 21, 2015

HHIQCD2015

49

BESIII: e+e- → π+π-J/ events
TypicalJ/ →+-

TypicalJ/ →e+e-• 4 charged tracks, J/ reconstruct via lepton pairs• very clean sample, very high efficiency, kinematic fit used
• only use MDC & EMC information, MC simulation reliable
Feb 15 - Mar 21, 2015

HHIQCD2015

50

BESIII: e+e- → π+π-J/ – J/ signals @ 4.260 GeV
PRL 110, 252001

882±33J/ →+-595±28J/ →e+e-• Dominant background e+e- → p+p-p+p• J/ signal: [3.08,3.12] GeV• J/ sideband: [3.0,3.06] GeV or [3.14,3.20] GeV
Feb 15 - Mar 21, 2015

HHIQCD2015

51

e+e- → π+π-J/ – cross sections @ 4.260 GeV

PRL 110, 252001

BaBar: PRD86, 051102 (2012)

Belle: PRL110, 252002

BESIII: B(e+e- p+p-J/) = (62.91.93.7) pb• agreement with BaBar & Belle• best precision!
Feb 15 - Mar 21, 2015

HHIQCD2015

BESIII cross sections:• more energy points• more data!

52

BESIII: e+e- → π+π-hc(1P) events

Feb 15 - Mar 21, 2015

HHIQCD2015

53

BESIII: e+e- → π+π-hc(1P) @ 4.260 GeV

PRL 111, 242001

 hc → gc, c → hadrons [16 exclusive decay modes]• pp, p+p-K+K-, p+p-pp, 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• ppp0, K+K-, p+p-, p+p-p0p0, 2(p+p-), 2(p+p-p0)

c candidate
hc candidate
Feb 15 - Mar 21, 2015

HHIQCD2015

54

BESIII: e+e- → π+π-hc(1P)

PRL 111, 242001•

(e+e- p+p-hc) ~ (e+e- p+p-J/) but line shape different•

Local maximum ~ 4.23 GeV

Feb 15 - Mar 21, 2015

HHIQCD2015

55

e+e- → π+π-hc(1P) vs e+e- → p+p- J/

PRL 111, 242001

Open circles: Belle e+e- p+p-J/
Solid dots: BESIII e+e- p+p-hc

More data at higher energies needed to complete line shape measurement
Feb 15 - Mar 21, 2015

HHIQCD2015

56

BESIII: e+e- → π+π-J/ @ 4.260 GeV

PRL 110, 252001

Phase space reflection
on Zc(3900)

Modelling p+p- with know structure:• f0(500)• f0(980)• non-resonant
Fits quite well p+p- projection
Feb 15 - Mar 21, 2015

HHIQCD2015

57

BESIII: e+e- → π+π-J/ @ 4.260 GeV

PRL 110, 252001

Phase space reflection
on Zc(3900)

Modelling p+p- with know structure:• f0(500)• f0(980)• non-resonant
Fits quite well p+p- projection
Feb 15 - Mar 21, 2015

HHIQCD2015

58

BESIII: e+e- → π+π-J/ @ 4.260 GeV

PRL 110, 252001

Phase space reflection
on Zc(3900)

Feb 15 - Mar 21, 2015

HHIQCD2015

59

BESIII: e+e- → π Zc(3900) → π+π-J/ @ 4.260 GeV

PRL 110, 252001

•
•
•
•

couples tocc
has electric charge
at least 4-quarks
what is its nature?

S-wave Breit-Wigner with efficiency correction
M = (3899.0±3.6±4.9) MeV/c2
Significance = (46±10±20) MeV/c2>8
R = (21.5±3.3±7.5)%
Feb 15 - Mar 21, 2015

HHIQCD2015

60

e+e- → π Zc(3900) → π+π-J/ @ 4.260 GeV

PRL 110, 252001

PRL 110, 252002 (2013)

PRL 110, 252001 (2013)

Belle

M = (3899.0±3.6±4.9) MeV/c2
 = (46±10±20) MeV/c2
307±48 events>8
Feb 15 - Mar 21, 2015

M = (3894.5±6.6±4.5) MeV/c2
 = (63±24±26) MeV/c2
159±49 events>5.2

HHIQCD2015

61

e+e- → π Zc(3900) → π+π-J/ @ 4.260 GeV

PRL 110, 252001

K. Seth & co. @ 4.170 GeV
hep-ex:1304.3036

Belle
M = (3885±5±1) MeV/c2
 = (34±12±4) MeV/c2
81±20 events
6.1
Feb 15 - Mar 21, 2015

PRL 110, 252002

HHIQCD2015

62

e+e- → π Zc(3900) → π+π-J/ @ 4.260 GeV

PRL 110, 252001

One of APS
2013 highlights

Feb 15 - Mar 21, 2015

HHIQCD2015

63

e+e- → π0 Zc(3900)0 → π0π0J/ @ 4.230-4.260 GeV

Preliminary

CLEOc: PLB 727, 366
3.5σ

BESIII PRELIMINARY!
 2.8fb-1 data at 10 energy points from 42304420 MeV
 Zc(3900)0 is observed clearly at:
Ecm=4230, 4260, 4360MeV

M = (3894.8±2.3±2.7) MeV/c2
 = (29.6±8.2±8.2) MeV/c2>10
An isospin triplet for Zc(3900) has been established
Preliminary

Feb 15 - Mar 21, 2015

Preliminary

HHIQCD2015

Preliminary64e+e- → π∓ Zc(3900) → π+π-ω @ 4.230-4.260 GeV
1 fb-1 @ Ecm=4230 MeV

Preliminary

0.8 fb-1 @ Ecm=4260 MeV

Preliminary

Preliminary

No evidence of a Zc(3900) signal
 σ(e+e- → π∓ Zc(3900) , Zc(3900) → πω) < 0.27 pb @ 4.23 GeV 90%

 σ(e+e- → π∓ Zc(3900) , Zc(3900) → πω) < 0.18 pb @ 4.26 GeV 90%
Feb 15 - Mar 21, 2015

HHIQCD2015

65

e+e- → π Zc(4020) → π+π-hc(1P) – all energies

PRL 111, 242001• all collected energies[3.900  4.420 GeV]
• hc → gc, c → hadrons[16 exclusive decay modes]
Feb 15 - Mar 21, 2015

HHIQCD2015

66

e+e- → π Zc(4020) → π+π-hc(1P) – 4.23/4.26/4.36 GeV

PRL 111, 242001

Simultaneous fit to 4.26/4.36 GeV data and 16 c decay modes.
4.23+4.26+4.36 GeV
4.23+4.26 GeV

σ(e+e-→πZc(4020)→π+π-hc)
M = (4022.9±0.8±2.7) MeV/c2
σ(4.23 GeV) = (8.7±1.9±2.8±1.4) pb
 = (7.9±2.7±2.6) MeV/c2
σ(4.26 GeV) = (7.4±1.7±2.1±1.2) pb>8.9
σ(4.36 GeV) = (10.3±2.3±3.1±1.6) pb
4.26 GeV:σ(e+e-→πZ (3900) + π- →π+π-h ) = < 11 pb (90% C.L.) B((hc→γηc)cFeb 15 - Mar 21, 2015c

HHIQCD2015

67

e+e- → π Zc(4020)0 → π0π0hc(1P) – 4.23/4.26/4.36 GeV

PRL 113, 212002

BESIII PRELIMINARY!
 2.8fb-1 data at 10 energy points from 42304420 MeV
 Zc(4020)0 is observed clearly at: Ecm=4230, 4260, 4360MeV
(e+e-→p+p- hc)
(e+e-→p0p0 hc)

hc

M Z (4020) = (4023.9±2.2±3.8) MeV/c20c

M Z (4020) = (4022.9±0.8±2.7) MeV/c2cΓ Z (4020) fixed @ ΓZ (4020)
c

0

c



An isospin triplet forZc(4020)
has also been observed>5
Feb 15 - Mar 21, 2015

HHIQCD2015

68

e+e- → π Zc(4020)0 → π0π0hc(1P) – 4.23/4.26/4.36 GeV

PRL 113, 212002

BESIII PRELIMINARY!
 2.8fb-1 data at 10 energy points from 42304420 MeV
 Zc(4020)0 is observed clearly at: Ecm=4230, 4260, 4360MeV
(e+e-→p+p- hc)
Preliminary(e+e-→p0p0 hc)

hc

M Z (4020) = (4023.6±2.2±3.8) MeV/c20c

An isospin triplet forZc(4020)
has also been observed

M Z (4020) = (4022.9±0.8±2.7) MeV/c2cΓ Z (4020) fixed @ ΓZ (4020)
c

0

>5
Feb 15 - Mar 21, 2015c(e+e-→p+p- hc)  2 (e+e-→p0p0 hc)
isospin conservation
HHIQCD2015

69

BESIII: e+e-→ pZc(3885) → p- (DD*)++c.c. @ 4.260 GeV

PRL 112, 022001

525 pb-1 data @ 4260 MeV: single tag analysis

M = (3883.9±1.5±4.2) MeV/c2
P = 1+
pZ(3885)
ang.
dist.
favoursJc
 = (24.8±3.3±11.0) MeV/c2
disfavours 1- e 0 >18σ(e+e-→ p- Zc(3885)+ × Zc(3885)+ → (DD*)+ +c.c.) = (83.5±6.6±22.0) pb
Γ(Zc(3885) → D*D*)R=
Γ(Zc(3900) → p J/ψ)Feb 15 - Mar 21, 2015

HHIQCD2015= (6.2±1.1±2.7)
70BESIII: e+e-→ pZc(3885) → p- (DD*)++c.c. @ 4.260 GeV

PRL 112, 022001

525 pb-1 data @ 4260 MeV: single tag analysis

Feb 15 - Mar 21, 2015

HHIQCD2015

71

BESIII: e+e-→ pZc(3885) → p- (DD*)++c.c. @ 4.260 GeVBESIII preliminary

525 pb-1 data @ 4260 MeV: double tag analysis

Feb 15 - Mar 21, 2015

HHIQCD2015

72

BESIII: e+e-→ pZc(3885) → p- (DD*)++c.c. @ 4.260 GeVBESIII preliminary

525 pb-1 data @ 4260 MeV: double tag analysis

e+e-→ p+ D0 D*-

e+e-→ p+ D- D*0Preliminary

Preliminary

Preliminary

Preliminary

M = (3884.3±1.2±1.5) MeV/c2
 = (23.8±2.1±2.5) MeV/c2>10
Feb 15 - Mar 21, 2015

Compatible with but
significantly more precise
than single-tag analysis

HHIQCD2015

73

BESIII: Zc(3885)+ quantum numbers?

BESIII preliminary

525 pb-1 data @ 4260 MeV: double tag analysiscos π : angle between bachelor pion and beam axis in CMS

0+ excluded by parity conservation
0- π and Zc(3885) in P-wave, with Jz = 1 → dN/dcosπ  1 – cos2π
1- π and Zc(3885) in P-wave→ dN/dcosπ  1 + cos2π
1+ π and Zc(3885) in S or D wave;
assuming D wave small near threshold → flat distribution in cosπe+e-→ p+ D0 D*-

DD̅* structure:
data clearly favour JP = 1+
Confirms JP for Zc(3885)
from single tag analysis
Feb 15 - Mar 21, 2015

HHIQCD2015

74

BESIII: e+e-→ pZc(4025) → p- (D*D*)++c.c. @ 4.260 GeV

PRL 112, 132001

M = (4026.3±2.6±3.7) MeV/c2
 = (24.8±5.7±7.7) MeV/c2
σ(e+e-→ p- (D*D*)++c.c.) = (137±9±15) pb>10σ(e+e-→ p-Zc+→ p- (D*D*)++c.c.)R== (65±9±6)%σ(e+e-→ p- (D*D*)++c.c.)Feb 15 - Mar 21, 2015

HHIQCD2015

75

BESIII: e+e-→ pZc(4025) → p- (D*D*)++c.c. @ 4.260 GeV

PRL 112, 132001

Zc(3900)+?

Zc(3900)0?

Zc(4020)+?

Zc(4020)0?

Which is the nature of these states? Isospin triplets?
Different decay channels of the same observed states? Other decay modes?
Feb 15 - Mar 21, 2015

HHIQCD2015

76

BESIII: Zc states

State

Mass(MeV)

Width(MeV)

Decay
mode

Process

Zc(3900)±

3899.0±3.6 ±4.9

46±10 ±20p±J/ψe+e-→p+p-J/ψ

Zc(3900)0

3894.8±2.3±2.7

29.6±8.2±8.2

p0J/ψ

e+e-→p0p0J/ψZc(3885)±3883.9±1.5±4.2[single D tag]
3884.3±1.2±1.5[double D tag]24.8±3.3±11.0[single D tag]23.8±2.1±2.6[double D tag]

D0D*D-D*0

e+e-→p+D0D*e+e-→p+D-D*0

Zc(4020)±4022.9±0.8 ±2.7

7.9±2.7 ±2.6

p±hc

e+e-→p+p-hc

Zc(4020)04023.9±2.2 ±3.8

fixed

p0hc

e+e-→p0p0hc

Zc(4025)±4026.32.63.7

24.85.67.7

Feb 15 - Mar 21, 2015

HHIQCD2015

D*0D*- e+e-→p+(D*D*)-77

BESIII: Zc states

Thresholds:
 DD*: 3875 MeV
 D*D*: 4014 MeV

Zc states @ BESIII:
 at least 4 quarks: charged
 near threshold isospin I=1
 are they one or two states
Feb 15 - Mar 21, 2015

HHIQCD2015

78

BESIII: e+e- → cc0 (cc0 → π+π-, K+K-)

arXiv:1410.6538

1 fb-1 @ Ecm=4230 MeV

0.8 fb-1 @ Ecm=4260 MeV
 (e+e- → cc0 ) =• (55.4±6.0±5.9) pb @ 4.23 GeV• (23.7±5.3±3.5) pb @ 4.26 GeV
A fine structure at 4230MeV?
 The mass of Y(4260) is very close to ccJ mass threshold Observation of cc0 at 4230, 4260 MeV data
Assuming
cc0 from a resonance: No evidence of cc0 at 4360 MeV
 No evidence of cc1/cc2 at 4230/4260/4360 MeV
M = (4230±8±6) MeV/c2
 Line shape seems inconsistent with Y(4260)
 = (38±12±2) MeV/c2
 BW fitting: a narrow structure around 4230MeV. > 9Feb 15 - Mar 21, 2015

HHIQCD2015

79BESIII: e+e- → γccJ (ccJ → γJ/ψ, J/ψ → μ+μ-)

arXiv:1411.6336

 Statistically incompatible with background (radiative μμ) Limited statistics
Ecm=4009 MeV

Ecm=4230 MeV

 Simultaneous fit @ 4 Ecm assumingY(4260) lineshape for σ(e+e- → γccJ)χc0
0σ
Ecm=4260 MeV

Feb 15 - Mar 21, 2015

Ecm=4360 MeV

HHIQCD2015

χc1
2.4 σ

χc2
4.0 σ

80

BESIII: e+e- → γccJ (ccJ → γJ/ψ, J/ψ → μ+μ-)

arXiv:1411.6336

 σB(e+e- → γccJ) Born measured cross section

σB(e+e- → γcc1)

σB(e+e- → γcc0)

σB(e+e- → γcc2)

σUP compatible
with NRQCD thoreticalpredictions [1][1] arXiv:1310.8597

Feb 15 - Mar 21, 2015

HHIQCD2015

81

BESIII: e+e- → ηJ/ψpreliminary

1 fb-1 @ Ecm=4230 MeV

0.8 fb-1 @ Ecm=4260 MeV

Preliminary
Preliminary

Preliminary

Feb 15 - Mar 21, 2015

HHIQCD2015

Preliminary82

BESIII: e+e- → ηJ/ψpreliminary

Preliminary

 good agreement with previous results and more precise
 cross sections peaks at  4.2 GeV higher energy points’ analysis on goingFeb 15 - Mar 21, 2015

HHIQCD2015

83

BESIII: e+e- → η’J/ψ
1 fb-1 @ Ecm=4230 MeV

0.8 fb-1 @ Ecm=4260 MeV

Preliminary

Preliminary

Feb 15 - Mar 21, 2015preliminary

HHIQCD2015

Preliminary

Preliminary

84

BESIII: e+e- → η’J/ψ

preliminary

Preliminary

 first observation
 too low statistics to infer line shape but  (e+e- → η’J/ψ) =• (3.1±0.6±0.3) pb @ 4.23 GeV• (3.9±0.8±0.4) pb @ 4.26 GeV
Feb 15 - Mar 21, 2015

HHIQCD2015

85

BESIII Inner Tracker upgrade

The BESIII CGEM-IT

BESIIICGEM

Feb 15 - Mar 21, 2015

HHIQCD2015

86

GEM: principle of operation
The GEM (Gas Electron Multiplier) [F.Sauli, NIM A386
(1997) 531] is a thin (50 μm) metal coated by a kapton foil
perforated by a high density of holes (70 μm diameter,
pitch of 140 μm)→ standard photo-lithographic technology.
By applying 400-500 V between the two copper sides, anelectric field as high as ~100 kV/cm is produced into theholes which act as multiplication channels for electrons
produced in the gas by a ionizing particle.
Gains up to 1000 can be easily reached with a single GEM
foil. Higher gains (and/or safer working conditions) areusually obtained by cascading two or three GEM foils.

A Triple-GEM detector is built byinserting three GEM foils between twoplanar electrodes, which act as thecathode and the anode.
Feb 15 - Mar 21, 2015

HHIQCD2015

87

GEM detector features•

flexible geometry → arbitrary shape: rectangular, cylindrical …

•

ultra-light structure → very low material budget: <0.5% X0/chamber•

gas multiplication separated from readout stage → arbitrary readout
pattern: pad, strips (XY, UV), mixed …

•

high rate capability: >50 MHz/cm2•

high safe gains: > 104•

high reliability: low discharge, Pd < 10-12 per incoming particle•

rad hard: up to 2.2 C/cm2 integrated over the whole active area without
permanent damages (corresponding to 10 years of operation at LHCb1)•

high spatial resolution: down to 60µm•

good time resolution: down to 3 ns (with CF4)

Feb 15 - Mar 21, 2015

HHIQCD2015

88

KLOE2 CGEM-IT• 4 CGEM layers at 13/15.5/18/20.5 cm from IP
A cylindricalinside outer Drift Chamber
triple GEM• 700 mm active length• XV strips-pads readout(25°  30° stero angle)• 2% X0 total radiation length
in the active region including
Carbon Filter shield
The KLOE-2 Collaboration built the only
existing CGEM based detector currently
currently under commissioning.
Due to the operational delays of DAϕNE, thecollider histing the KLOE-2 spectrometer,
the investigation of its performance is still
under progress.
Feb 15 - Mar 21, 2015

HHIQCD2015

89

BESIII innovations w.r.t. KLOE-2
The innovative aspects are mainly related, but not limited, to thefollowing three items:• the material used to give the mechanical rigidity to thedetector structure(Rohacell instead of Honeycomb)• the anode design• the different readout mode, analogue instead of digital

Feb 15 - Mar 21, 2015

HHIQCD2015

90

BESIII: a Rohacell based cathode (and anode)Read-out

cathode structure layout
Anode

2 mm
2 mm
2 mm
3 mm

GEM 3
GEM 2
GEM 1
Cathode12.5 m Kapton
12.5 m Kapton
1 mm Rohacell 31

Rohacell is a very light material (density of 32 kg/m3)that will be replace the honeycomb in the cathode andanode construction with substantial reduction of the
thickness of the detector.
BESIIIKLOE-2# of X0 for 1 layer

0.33

0.49

# of X0 for 3 layers

0.99

1.47

This technique has been successfully tested by INFN
Feb 15 - Mar 21, 2015

HHIQCD2015

91

BESIII: anode design
A jagged-strip layout has been
designed to minimize the strip
capacitance:

jaggedsimpleFeb 15 - Mar 21, 2015~30% inter-strip capacitance reduction
comparedto thestandard
strip
configuration

In addition:
the ground will be
kept at 2 – 4 mmfrom the strip
plane support
structure made of
Rohacell

HHIQCD2015

92

BESIII: anode validation and test
BESIII anode design validation in progress:• Validations with Garfield
simulations (in progress)

GEM electron
amplification
simulated by
Garfield• Prototype beam test

Feb 15 - Mar 21, 2015

HHIQCD2015

93

The BESIII CGEM-IT• The mechanical design account for: the mechanics of the interaction region;
the location of the frontend boards; the placement of the high voltage
distribution cards at the edges of detector.
• The radial dimension are limited internally by the beam pipe and externallyby the Drift Chamber and on the sides by the beam pipe supporting flanges.

Feb 15 - Mar 21, 2015

HHIQCD2015

94

The BESIII CGEM-IT• Along the z direction theavailable space for thefronted electronics andthe utilities is limited bya set of flanges that
holds the beam pipe.

CGEM layer 3

CGEM layer 1
cooling system
Beam pipe• In order to free as muchspace as possible themechanical length of thethree layers will beslightly incremental withthe radius.
• A compact mechanical interface, called “service flange” has been designed inorder to host all the utilities and to smooth the cable routing.
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The BESIII CGEM-IT: some detector details
Section of CGEM layer 2
readout plane
GEM3
GEM2
GEM1
cathodeLayer 2 is the first being
built; construction is inprogress.
The frontend electronics
cards will be located in
the dead space available
between the layers
outside the active area.
The outermost layer
frontend cards will belocated on a service
flange.
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The BESIII CGEM-IT: a view of the detector

Complete 3D modelof CGEM-IT layer 2.

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BESIII CGEM-IT Front End Electronics
 Goals:• spatial resolution  100 μm• time resolution  1 ns
• short dead time < 1 μs
A new ASIC to perform Analogue Readout is needed!
 Design of CGEM-IT ASIC (UMC 0.11 μm):
• inheriting from existing design (IBM 0.13 μm)• BackEnd design shared by several projects• BackEnd porting to UMC 0.11 μm in progress• different input stage (suited for CGEM) to increase signal sensitivity
and SNR FrontEnd Simulations in progress:• input stage optimized to handle capacitance in the range 20  150 pF• circuit tested with a delta-pulse and GEM-like signal
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Summary huge statistics:• J/, (2S), (1D)• XYZ studies• R scans near future:• collect data at higher energies to complete scans• higher luminosity expected from BEPCII• analyse the full data samples• many PWA to be completed
 stay tuned:• many new exciting results on their way Room for upgrades and R&D:
• BESIII CGEM-IT• ASIC R&D to perform CGEM-IT Analogue Readout
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Question time

ありがとうございます!

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Spare slides

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How to produce Charmonium states
J/ψ, ψ(2S)

1. e+e- annihilation (including
ISR/double charmonium)ψ 1--ψ, χcJ, ηc

2. pp annihilation

ηc , ηc(2S)0-+, 0++, 2++

3. Two-photon process

4. B decaysccc=+ψ, χcJ, ηc
B

1- - 1++ or 0-+

5. Charmonium transition
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BESIII data set

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4260

4420

4390

4310

4220
4245

4190

4090

3900

3810

4210

4010

4230

3.3 fb-1 for XYZ studies

103

BESIII: PWA of J/ → γηη, η → γγ

PRD 87, 092009

 J/→ϕη, ϕ→γη:• select events outside ϕ window background:• low and mostly non-η background,• estimanted by η sidebands (blue shadow) background subtraction:• ln Lsignal = ln Ldata – ln Lsideband
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BESIII: PWA of J/ → γωϕϕϕω

Feb 15 - Mar 21, 2015

PRD 87, 032008

ω solid:• background estimated from sidebands
 dashed:• inclusive J/ MC samples
 background subtraction:• ln Lsignal = ln Ldata – ln Lsideband
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BESIII: PWA of (2S) → ppη

PRD 88, 032010

(2S) → J/ X , J/ → pp subtracted
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BESIII: PWA of (2S)→ppπ0

PRL 110, 022001

shaded:background:• continuum• non-π0background(2S) → J/ X , J/ → pp subtracted
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BESIII: PWA of J/ → γpp, Mpp<2.2 GeV PRL 108, 112003

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BESIII: ηc parameters from (2S) → π0hc(1P), hc(1P) → γηc(1S)

PRD 86, 092009

Symmetric lineshapein gg production

Asymmetric lineshapein  decay

The C lineshape is not
distorted in the hc→gC
BESIII
backgroundsubtracted• CLEO-c observe a distortion of clineshape in charmonium radiative decay
PRL102, 011801 (2009)• The lineshape of c from BELLE issymmetric• The abnormal line shape is also observedin BESIII exclusive channels in →gcbut not in →p0hc, hc→gc

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Hadronic exotic states• Experiments :- Hadrons are composed of 2 (meson) or 3 (baryon) quarks- Described very well in quark model (QM)

• QCD suggests:- Confinement : stable hadrons need to be colorless- Gluon-gluon interactions : hadron with gluons(hybrids and glueballs) could exist- Allow hadrons with Nquarks2, 3 (multi-quarks)

Can we find evidence for these interesting exotic hadrons?
A long history of searching for the exotic hadron,no solid conclusion was reached in past a few decades,
some hints on charmomium-like and bottomnium-like particles, recently.

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Exotic Meson (Charmonium-Like)
Molecular states:•••

Loosely bound states of a pair of mesons,bound by the long-range color-singlet pion exchange,
weakly bound, mesons tend to decay as if they were free.

Tetraquarks:••••

bound states of four quarks,
bound by colored-force between quarks,
decay through rearrangement,
many states with the same multiplet, some are with nonzero charge, or strangenessHybrids:••

Feb 15 - Mar 21, 2015

bound states with a pair of quarks and one excited gluon
Lattice and model predictions for lowest lying charmonium
hybrid m4200 MeV

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BESIII: e+e- → π+π-X(3823) → π+π-γ cc1

BESIII preliminary• Reconstructing cc1,2 → gJ/ψ → gl+l• Consider recoiling mass against the π+π- system: M(π+π-)
in 5 large data set: total luminosity  4.1 fb-1

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Zc states
The most promising way to searching for the exotic hadrons Decay into a charmonium or D(*)D(*) pair- thus contains hidden-cc pair - Have electric charge,- thus has two more light quarks

At least 4 quarks, not a conventional meson
 Observed in final states :-- p±J/, p±(2S), p±hc, p±ccJ, (D(*)D(*) ) ,…

 Experimental search:- BESIII/CLEO-c : e+e-p± +Exotics, ….
- Belle/BaBar: e+e-(gISR)p+Exotics, ….

- Belle/BaBar/LHCb: BK+Exotics, …

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BESIII: e+e- → π+π-J/
•
•
•
•
•
•

PRL 110, 252001

Is it a real signal?
Is it due to p+p- S-wave states, like , f0(980), …?
Is it due to p+p- D-wave states, like f2(1270), …?
Are there two states, one at 3.4, the other 3.9 GeV?
Exist in both e+e- & +- samples?
Exist in both p+p- low mass and high mass samples?
Background fluctuation?

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N
N
N
Y
Y
N

114

BESIII: e+e-→ pZc(4025) → p- (D*D*)++c.c. @ 4.260 GeV

hep-ex:1308.2760• 827 pb-1 data at ECM=4.260 GeV• Tag a D+ and a bachelor p-, reconstruct one p0 to suppress the
background.

Topology of the decays of the signal process:• thick line circled: D+ and π- detected in the final states• dashed line circled: at least of π10 or π20 tagged
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BESIII: e+e-→ pZc(4025) → p- (D*D*)++c.c. @ 4.260 GeV

hep-ex:1308.2760

removedRemoveDD, DD*,
D*D*,
DsDs, …

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BESIII: Zc(4020)=Zc(4025)?

PRL 111, 242001
hep-ex:1308.2760

M(4020) = (4021.81.02.5) MeV
M(4025) = (4026.32.63.7) MeV
(4020) = (5.73.41.1) MeV
(4025) = (24.85.77.7) MeV
Close to D*D* threshold (4017 MeV)
Mass consistent with each otherbut.. width ~2 difference
Interference with other amplitudes
may change the results
Coupling toD*D* is much larger
than to phc if they are the same stateWill fit with Flatte formulaFeb 15 - Mar 21, 2015

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What is the X(3872)?
 Mass: Very close toD0D*0 threshold Width: Very narrow, < 1.2 MeV
 JPC=1++[LHCb]
 Production

Belle, 2003
140/fb• inpp/pp collision – rate similar to charmonia• In B decays – KX similar tocc, K*X smaller thancc• Y(4260)→g+X(3872) [BESIII, preliminary] Decay BR: open charm ~ 50%, charmonium~O(%)
 Nature (very likely exotic)• LooselyD0D*0 bound state (like deuteron?)?
• Mixture of excited cc1 andD0D*0 bound state?
• Many other possibilities (if it is not cc1, where is cc1?)

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The ISR TechniqueFeb 15 - Mar 21, 2015

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ISR at BESIII

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ISR: Physics motivations

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Initial State Radiation

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ISR: BESIII vs BABAR

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ISR angular distribution and zero-degree tagging

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BESIII Zero Degree Detector

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