The -charm Physics @ BESIII
SHEN Xiaoyan
Institute of High Energy Physics, CAS
International Review Meeting
Oct. 21, 2013, IHEP, Beijing
Outline
• Introduction
• Highlights from -charm physics
• Management structure of BESIII
• Future prospects
• Summary
2
Standard Model (EW+QCD)

Many precision tests on SM, especially EW theory,
mainly in 4 exps. at LEP in CERN

Higgs discovered at LHC in CERN

Great success of EW theory !

QCD has been tested extensively at the high
momentum transfer by lots of high precision
experiments (> 10 GeV).

At low energy, QCD is difficult to be tested due to its
non-perturbative nature.
Fundamental questions need to be answered
• How does QCD work at low energy?
 Do the new forms of hadrons predicted by QCD exist ?
 How to calibrate QCD at low energy ?
• Does the physics beyond Standard Model exist?
 How to test EW theory precisely in -charm region?
 Where is the new physics in -charm sector ?
What can we do at BEPC2/BESIII ?
Beijing Electron Positron Collider (BEPC)
beam energy: 1.0 – 2.3 GeV
LINAC
2004: started BEPCII upgrade,
BESIII construction
2008: test run
2009 - now: BESIII physics run
BESIII detector
BEPCII/BESIII – unique facility at -charm
energy region in the word now.
5
Features of the BEPC Energy Region





Rich of resonances: charmonia and charmed mesons
Threshold characteristics (pairs of , D, Ds, …)
Energy location of the glueballs, hybrids and multi-quark states
Energy location of the XYZ’s
Transition between smooth and resonances, perturbative and
non-perturbative QCD
PDG
The Y’s are
here ….
6
6
Fundamental questions need to be answered
• How does QCD work at low energy?
 Do the new forms of hadrons predicted by QCD exist ?
 How to calibrate QCD at low energy ?
Search for the new hadrons and systematic study
of the spectroscopy – a way of understanding the
internal structure of hadrons.
• Does the physics beyond Standard Model exist?
 How to test EW theory precisely in -charm region?
 Where is the new physics in -charm sector ?
New forms of hadrons
 Conventional hadrons consist of 2 or 3 quarks：
Naive Quark Model：
 QCD predicts the new forms of hadrons:
• Multi-quark states ：Number of quarks >＝ 4
g
• Hybrids ： qqg，qqqg …
• Glueballs ： gg， ggg …
g
g
g
None of the new forms of hadrons is settled !
Precision measurement of CKM elements
-- Test EW theory
CKM matrix elements are fundamental SM parameters that describe
the mixing of quark fields due to weak interaction.
5% precision
10% precision
 VudVusVub
 d '



 s '    Vcd VcsVcb
V V V
 b' 


 td ts tb
Three generations of quark?
Expected precision < 2% at BESIII
9
 d

 s
 b






CKM matrix
BESIII + B factories +
LQCD
Unitary matrix?
BESIII + B factories +
LHCb + LQCD
Precision measurement of CKM matrix elements
-- a precise test of SM model
New physics beyond SM?
Physics Topics at BESIII
 Hadron spectroscopy
 search for the new forms of hadrons
 meson spectroscopy
 baryon spectroscopy
Int. J. Mod. Phys. A, Vol. 24 (2009)
 Study of the production and decay mechanisms of
charmonium states: J/, (2S), C(1S), C{0,1,2} ,
C(2S), hC(1P1), (3770), etc.
Calibrate QCD
 Precise measurement of R values,  mass, ...
 Precise measurement of CKM matrix
 Search for DD mixing, CP violation, etc.
10
BESIII Detector
CsI(Tl) EMC
MDC
R inner: 63mm ;
R outer: 810mm
Length: 2582 mm
Layers: 43
Crystals: 28 cm(15 X0)
Barrel: |cos|<0.83
Endcap:
0.85 < |cos| < 0.93
RPC MUC
TOF
BTOF: two layers
ETOF: 48 crys. for each
BMUC: 9 layers – 72 modules
EMUC: 8 layers – 64 modules
11
BESIII Detector Performance
MDC
Exps.
MDC
Spatial
dE/dx
Energy
resolution resolution resolution
CLEOc
110 m
5%
2.2-2.4 %
Babar
125 m
7%
2.67 %
Belle
130 m
5.6%
2.2 %
115 m
<5%
(Bhabha)
2.2%
BESIII
(2013)
TOF
EMC
Exps.
Time
resolution
CDFII
100 ps
Belle
90 ps
BESIII
(2013)
68 ps (BTOF)
98 ps (ETOF)
MUC: Efficiency ~ 96%
BG level: < 0.04 Hz/cm2(B-MUC), < 0.1 Hz/cm2(E-MUC)
Data/Monte-Carlo Consistency
• For tracking efficiency, data/MC difference < 1%
• For particle identification efficiency, data/MC difference < 2%
BESIII Physics Results
• Hadron spectroscopy
– Search for non-qq, non-qqq states
– Meson & baryon spectroscopy
• Charmonium physics
pb
– Transitions and decays
• Charm physics
– Decay constant fD
– CKM matrix elements: Vcd, Vcs
• Precision measurement of R, 
• Search for new physics
5000
0
-1
ψ(3770)
2900
BESIII Physics Results (since 2009)
• Papers published：
– 53 papers published (PRL 12, PRD 37，PLB 1, CPC 3)
2010: 4 (PRL 2, PRD 1, CPC 1)
2011: 11 (PRL 3, PRD 8)
2012: 17 (PRL 5, PRD 10, PLB 1, CPC 1)
2013: 21 (PRL 2, PRD 18, CPC 1)
-- Submitted 6 (PRL 5, CPC 1)

International conference talks
About 50 talks at the international conferences every
year. Among them, about half are the invited talks.
15
Highlights from -charm Physics
Charmonium spectroscopy
• Below open charm threshold
All charmonium states observed.
No surprising found.
• Above open charm threshold:
 many expected states not
observed
 many unexpected discovered
Z(4430)
Z(4250)
Z(4050)
Z(3900)
X(3872)
XYZ(3940
)
X(3915)
X(4160)
Y(4008)
Y(4140)
Y(4260)
Y(4360)
X(4350)
Y(4660)
Data taking at 4260 and 4360 MeV
for XYZ study
BESIII: Observation of the Zc(3900)
— a charged charmonium-like structure
BESIII: PRL110, 252001 (2013)
BESIII
Significance
>8
What is Zc(3900)?
• Couples to cc
• Has electric charge
• At least 4-quarks
Many theoretical interpretations:
Submitted the paper on March 24,
2013. Already got 81 citations !
•
•
•
•
•
DD* molecule?
Tetraquark state?
Cusp?
Threshold effect?
…
Impacts of the Zc(3900)
PRL110, 252001 (2013)
PRL referee says: ”Since a charged
charmonium-like state cannot be
conventional ccbar meson, the Z(3900)
may be the first indisputable example
of a multi-quark meson.
81 citations
Any more decay modes for Zc(3900) ?
Observation of Zc(3900) in DD*0
Zc(3900)
(Zc(3900)  DD*0)
6

(Zc(3900)   J/)
JP favors 1+
Very important in understanding Zc(3900) !
arXiv: 1310.1163, submitted to PRL
Does the charged Zc(3900)’s partner exist ?
Observation of Zc(4020)
BESIII
What is Zc(4020)?
• Couples to cc
• Has electric charge
• At least 4-quarks
arXiv: 1309.1896, submitted to PRL
22
BESIII confirmed X(1835) and observed X(2120) & X(2370)
BESIII: Phys. Rev. Lett. 108 (2011)112003
• LQCD predicts the lowest
lying 0-+ glueball at around
2.4 GeV/c2.
• What is the nature of
X(2120)/X(2370) ?
• Glueballs can be largely
produced in J/ radiative
-+ glueball ?

0
decays.
 excited /’ state ?
• First observed the
resonant structures in the • Is X(1835) the same state
2.4 GeV/c2 region in J/
as pp enhancement?
radiative decays.
Measurement of fD from D+  
The BESIII Collaboration
US (5)
Univ. of Hawaii
Carnegie Mellon Univ.
Univ. of Minnesota
Univ. of Rochester
Univ. of Indiana
Europe (13)
Germany: Univ. of Bochum,
Univ. of Giessen, GSI
Univ. of Johannes Gutenberg
Helmholtz Ins. In Mainz
Russia: JINR Dubna; BINP Novosibirsk
Italy: Univ. of Torino，Frascati Lab, Ferrara Univ.
Netherland：KVI/Univ. of Groningen
Sweden: Uppsala Univ.
Turkey: Turkey Accelerator Center
Pakistan (2)
China(29)
Korea (1)
Seoul Nat. Univ.
Japan (1)
Tokyo Univ.
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., Beihang 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.
Univ. of Punjab
COMSAT CIIT
~400 members
52 institutions from 11 countries
~180 members from IHEP
25
BESIII Management Structure
IB(~51)
EB(~9)
Spokespersons (3, 3 years term)
Run
coordinator
Membership
committee
Software and
Computing
coordinator
Publication
committee
Speakers
bureau
Physics
coordinators
Convener-1
Convener-2
………
Shift
committee
Similar to other International Collaborations
Rules and policies
•
•
•
•
BESIII Collaboration Governance Rules
BESIII membership rules
Publication Policy
Responsibilities of the Speakers Bureau
……..
Data Taking
•
Data taking proposals presented and discussed at CM,
decision made by EB and collaboration
•
Adjust the data taking plans accordingly taking into
account the importance of the physics, the competitions
from other exps.
•
Run coordinator, weekly run coordinators, chief shifters,
shifters, on-call people, …. to ensure the high quality data.
IHEP Contribution
• The design, construction & operation of BESIII
MDC &
EMC &
ETOF &
BTOF
electronics electronics
electronics
IHEP
IHEP
IHEP
USTC
MUC
MUC
electronics
Trigger
& DAQ
IHEP
USTC
IHEP
• BESIII software
MDC
EMC
TOF
MUC
Physics tools
IHEP+SDU
IHEP
IHEP
PKU+IHEP
IHEP+USTC
• BESIII papers
Total
IHEP
IHEP supervisors
+ univ. students
59
30.5
13.5
Universities
15
IHEP Manpower
• Currently, 57 faculties (16 profs. ) and 42 Students
& post-docs for the maintenance, operation, upgrade
of BESIII, and for the software and physics analysis.
Leading scientists
•
•
•
•
•
•
•
•
WANG Yifang (Spokesperson from 2005 to Nov. 2011)
SHEN Xiaoyan (Spokesperson from Dec. 2011)
LOU Xinchou (EB member, IHEP IB)
ZHU Kejun, HE Kanglin (Run coordinators)
YUAN Changzheng (Physics coordinator)
LI Weidong (Software coordinator, EB member)
LI Haibo, JIN Shan (Were physics coordinators)
DONG Liaoyuan, ZHANG JIngzhi, FANG Shuangshi,
MO Xiaohu, LIU Huaimin, …… (conveners)
Prospects of BESIII
BESIII data taking status & plan
J/
’
”
(4040)/
(4170)/
(4260) ….
R scan
Previous
data
BESII: 58M
BESIII present
& near future
1.2 B 20* BESII
10 B
CLEO: 28 M
0.5 B
3B
CLEO: 0.8/fb
20* CLEOc
Goal
2.9/fb 3.5*CLEOc
10/fb
CLEO: 0.6/fb 2011: 0.5/fb @ (4040) 5-10 /fb
@ (4160) 2013：2/fb@4260,
0.5/fb@4360
BESII
Prospects of BESIII
• In 2013-2014 physics run, R scan above 3.8 GeV.
The goal: reach the precision of ~2% for R values.
• More results on XYZ particles will come
 understand the nature of XYZ
• Search for glueballs, hybrids,…
with huge J/ data.
• Precision measurement of CKM
elements
•  mass
Expected to have an error of
0.1MeV.
fD
Summary
• Observed Zc(3900), Zc(4020) at BESIII, opened a new
window  big impact. More results on XYZ particles
will come  understand the nature of XYZ
• Produced many important results on charmonium
physics, hadron spectroscopy, ….
• BESIII will run another 7-10 years
Upgrade of BESIII on going
– MRPC for ETOF
– New inner drift chamber
– CGEM for drift chamber
• More data will come, more physics output
• Keep the leading role in -charm physics in these years.
34
Backup slides
Standard Model (SM)

Matters are made of leptons and quarks:
e  


   
 e  

t

s b
c
Interactions are mediated by:
photons — electromagnetic
W± and Z — weak
gluons
— strong

u

d
Electroweak
theory (EW)
QCD
Origin of masses
Higgs (Discovered at LHC in 2012)
36
Pure leptonic decays
• All quantities are well measured except fD.
• Use world average |Vcd| to extract fD
• Compare fD with LQCD for the validation of LQCD
37
Preliminary study of D+   at BESIII
• 9 singly D- tag modes
(
)
NDtag- = 1.566 ± 0.002 ´ 106 in 2.9 fb-1
The error is still statistical dominated.
Comparison of fD with theories
fD (MeV)
Zc(4020)’s other decay mode ?
Observation of Zc(4025) in D*D*0
arXiv: 1308.2760, submitted to PRL
Standard Model and BES Physics
• Three generations of quarks and leptons
BES -charm Physics
• Interactions
– Electromagnetic interaction
– Weak interaction
– Strong interaction
｝
EW theory
QCD theory
Scalar glueball production in
J/ radiative decays from LQCD
Y.B. Yang, et al, Phys. Rev. Lett. 111, 091601 (2013)
• The widths of J/ radiatively decay to glueballs are
calculated directly in lattice QCD .
(J /   G 0 )  0.35(8)keV ,

 3.8(9)  103
tot
• This result can be compared to the production
rates of scalar mesons f0(1710), f0(1500)
J /   f0(1500)    (1.01  0.32  10 4
J /   f0(1710)  (1.5  0.3)  10  3
Support f0(1710) to be dominantly a scalar glueball.
Tensor glueball production
in J/ radiative decays from LQCD
L. Gui, et al, Phys. Rev. Lett. 110 (2013) 021601
• The tensor glueball production rate in J/ radiative
decay
 ( J /  G
2

) /  to t  1 .1 ( 2 )  1 0
2
• With the largest J/psi events sample,
the LQCD results can provide useful
information for BESIII to identify
the tensor glueballs.
Paper submission procedures
• Talk at the group meeting, get approval by the group
and group convener, get the analysis memo ready.
• Talk at the phys. & software meeting, get approval
• Physics coordinators assign 3 internal referees to
review the analysis, memo  draft be approved
• Collaboration wide review
• Spokespersons’ approval
The time from the submission to the journal to
finally being accepted for publication is short.