Suggested plan of charmonia
and
QCD study scan at BESIII
Hu Haiming
October 12-16, 2011
Hangzhou
Outline
☞ Physical Goals
☞ Suggested plan of data taking
☞ Estimations of beam time
☞ Tuning of generator LUARLW
☞ Improvement of ISR calculations
☞ ……
Projects of BESIII physics
Light hadron spectrumJ/ data
Charm
  
Light charmonium (2S) data
D physics  (3770) data
Heavy charmonia
BESIII
physics
tau

Uncharm

Mass
(4040)
(4190)
(4415)
X, Y, Z
 ……




Decay channels
R(s) fine scan (uds+c)
QED & QCD (s), (g-2)
multiplicity
inclusive (correlation)
R&QCD
exclusive
form factors
fragmentation functions
Bose-Einstein correlation

Projects of BESIII physics
☞ Continuous states
R value: 2.0  4.6 GeV
meson and baryon form factors: 2.0  3.0 GeV
fragmentation functions: 2.0  3.0 GeV
……
☞ family
parameters and decay ratio for
J/, (2S), (3773), (4040), (4150), (4415),
and new states X,Y,Z : 3.08  4.5 GeV
☞ Hadronic MC generators LUARLW
tuning parameters, signals, backgrounds, efficiencies
Goal of accuracy with BESIII
Academic significance: clear
!
Precision/error:
unknown ?
Discussion & efforts …
Data taking strategy
Phase I
Machine study (a few days)
To optimize the plan for R scan, it is important to perform a machine
study at energies of 4.2, 3.5, 2.5, 2.3 GeV before R scan, so that one
knows the beam energy and the corresponding luminosities and time
needed for the machine tuning.
It could be arranged in the year 2012 and 2013? Using the data from
the machine study, and the data collected at J/ , (2S), (3770) and
(4010) et.al, one can perform prestudy (data analysis and generator
pretuning) and establish the entire analysis chain.
Data taking strategy
Phase II
Fine R scan between 3.85  4.4 GeV (90 days?)
R scan from slightly above the open charm to the highest energy
BEPCII can reaches (4.5 GeV ?). The total energy points to be
scanned are about 80, and collect 10000 hadronic events at each
energy point.
A detailed scan with smaller steps in the energy region where X, Y, Z
states were reported, and the suspected structures from the previous R
measurements.
Smaller steps (2 -5 MeV) are chosen for R scan around the peak
positions of the resonances of (4040), (4160) and (4415), as well
as the location where R values are suspiciously higher or lower than
their surrounds, such as 3.9-4.0 GeV, around 4.06, 4.26 GeV.
Data taking strategy
Phase III
R scan from 3.6  2 GeV (100 days)
Collect large hadronic event samples from 3.6 GeV down to 2
GeV, with 15 energy points, each has 10000 hadronic events.
Single beam and separated beam data at a few energy points
covering the energy region to be scanned for R values are also
needed for the estimation of the beam associated background.
For the measurement of R value, proton form factor, the strong
running couple constant, as well as tests the QCD by measuring
the important inclusive and interested exclusive distributions.
Estimation of beam time
Based on the following estimations or assumptions
 luminosity of BEPCII changes with beam energy
 ratio of normal running time of BEPCII and BESIII
 energy spread of BEPCII
 data taking efficiency
 hadronic event selection efficiency
 hadronic cross section & ISR factor
 required statistics
 number of scanned energy points
 beam time
Formula used in beam time estimation
Time estimation of data taking:
The related quantities are estimated as following
BEPCII luminosity:
Formula used in beam time estimation
Hadronic acceptance/efficiency:
Efficiency of data taking:
Effective cross section with energy spread:
Factor of ISR correction:
Requested e+ e  pp data samples
R measurement at BESII Phys.Lett.B677,(2009)239
BESII:
Measured values
Related errors (%)
BESIII:
2.53.0%
?
R Measurements at BESII
Form factors of e+ e  p p
Production amplitude：
Hadronic current has two independent form factors:
Electronic & magnetic form factors:
，
Differential cross section :
With large statistic data sample, GE and GM could be obtained by fitting angular
distribution.
But, with BESII data, and assume |GM=GE＝G|
pQCD predicts
BESII data for pp
Ratio puzzle of e+ e  baryon pairs
FENICE data near threshold
?
 (e  e   p p )
 0.16

0
.
66
0.11
 
 (e e  n n)
Puzzle
 QCD (quark model) prediction
 (e  e  p p)
Qu2
 2  4
 
Qd
 (e e  nn)
 An intermediate coherent isovector state serving as an intermediary between e+e- and BB
i
2
i
 (e e  p p) A1  e A0
1 e 
f 


i
 
1  ei 
 (e e  nn) A1  e A0
 
2
J. Ellis and M. Karliner hep-ph/0108259
QCD 10-24 sec
r*, *
BESIII could collect data around 2.02.8 GeV , BB pairs
f
e  e       ,   , 0 0 , ,     , 0 0 ,   
2017/7/28
Wenbiao Yan USTC
QCD: (e+e   ) : (e+e   ): (e+e  0 0)  4:1:0
if at any particular energy, an I = 1 or I =0 resonance dominates, the above
ratio will not be maintained!
16
Measurement of s at BESII
Solve equation
Obtain coupling constant at every energies，
and then evolve them to 5 GeV with
Weighted average
errors
PDG2006
17
Error of s vs R precision
The error of s larger than that of R 15 times。So, s can be determined directly
based on R, and independent of any model, but not an “economical”way. 18
Error of s vs R precision
Uncertainty rage of R within 1
Uncertainty rage of s within 1
Charmonia
The main properties in production and decay are described as the Breit-Wigner,
and characterized by resonant parameters
electronic width
hadronic width
phase angle
nominal mass
total width
Known charmonia
21
BES’s measurements of BW parameters
J/
Phys. Lett. B355 (1995)
Energy points : 23
Total luminosity : 82.28/nb
Why so many
energy points
were scanned
?
Consider uncertainty of
beam energy calibration,
taking data at 23 energy
points were reasonable.
Processes analyzed:
Maximum error : 11%
BES’s measurements of BW parameters
(2S)
Events analyzed
Phys. Lett. B550 (2002)
Energy points : 24
Total luminosity : 1.149/pb
Fit simultaneously
Maximum error : 10%
Consider uncertainty of
beam energy calibration,
taking data at 24 energy
points were reasonable.
BESII’s measurements to BW parameters
(3770) (4040) (4160) (4415)
Phys. Rev. Lett. 97,121801 (2006)
Phys. Lett. B652, 238(2007)
Phys. Lett. B660, 315(2008)
Energy points : 78
Data analysis:
inclusive hadronic events
no lepton pairs
BESII measurements quoted in PDG10
25
BESII measurements quoted in PDG10
26
PHIPSI2009
(4160) or (4190)？
在BES扫描数据拟合中发现，无论采用什
么形式的连续本底以及强衰变宽度的能量
相关性，只要考虑了相因子，过去所称的
(4160)的质量都约为4190MeV；当丢掉
相因子时，其质量拟合值都约为4160MeV。
两者相差约30MeV，远大于7MeV的拟合
误差。这表明质量的移动是相因子效应。
在BES实验之前，已有不同的理论模型独
立地预言了此共振态的质量约为4195MeV。
Decay channels of higher charmonia
Coupling channel model
30
Potential models prediction
Nonrelativistic potential model
Relativizied potential model with QCD
hep-ph/0505002
“Higher Charmonia”
Experimental and theoretical spectrum of charmonium:
Solid line: experiment
Broken line: model
Potential model predictions
Phys. ReV. D32, 189 (1985)
Potential model predictions
Phys. ReV. D32, 189 (1985)
Potential model predictions
Phys. ReV. D32, 189 (1985)
Potential model predictions
Phys. ReV. D32, 189 (1985)
35
Potential model predictions
Phys. ReV. D32, 189 (1985)
36
PHIPSI2009
BESII missed Y(4260)
BESII曾以ΔEcm= 5 ~ 10
MeV 的 能 量 步 长 扫 描
了重粲共振态的结构,
但统计量较低,步长较
大, 不能确认观察到的
Ecm = 4.270 GeV处的突
起是有物理意义的峰
还是统计涨落.
BABAR研究了初态辐射事例 e+e- 
γ+ -, 并在有效能量处4.26 GeV观
察到衰变末态+-的不变质量谱,
因此发现了新粒子态 Y(4260).
理论对新共振态没有预言，是否还有可能存
在还未发现的其它新结构和新粒子态？
!
BABAR-PUP-05/029
hep-ex/0506081
DD
DDπ
DD*
D*D*
Sum of all exclusive contributions
DD*π
Λ+c Λc
Phi to Psi 2009
Only small room for unaccounted contributions
• Charm strange final states
Limited inclusive
data above 4.5 GeV
Galina Pakhlova
• Charm baryons final states
Comparison of theory and experiment
T.Barnes’s paper
Phys. Rev. D72, (2005)504026,
hep-ph/0505002v3
Theory：non-relativistic potential model、Godfrey-Isgur model
BESII value 25.6±6.3
？
BESII value 88.9±12.4
Comparison of theory and experiment
？
BESII value
78.8±16.1
Comparison of theory and experiment
？
BESII value 80.4±24.7
VEPP-4’s measurements of MJ/ and M(2S)
J/
hep-ex/0306050
Energy points : 7
Scan : 3+1 runs (E~0.6 0.45MeV)
Total luminosity : 40+10/nb
1. Precise energy calibration
2. Precise energy spread calculation
3. …
Highlight
(2S)
Scan : 3 run (E~0.9 MeV)
Total luminosity : 76/nb
BEPCII energy measurement system
Off-line data fitting:
M =Mfit –MPDG =0.02 ± 0.05 MeV
=M/2=0.010.03 MeV
PDG2010:
3686.09 ± 0.04 MeV
Accuracy of the beam
energy measurement:
/ ~ 2×10-5 (36 keV).
Stability of the EMS
Two runs (2S) fitting
44
Event selection in Ntot of J/ with BESIII
Events types analyzed
Event selection in Ntot of (2S) at BESIII
Events types analyzed
Error analysis
Estimation of beam time
7points
25hr
12/pb
9points
17points
60hr
28/pb
19points
64hr
30/pb
21points
7points
14hr
13/pb
9points
20hr
18/pb
11points
17points
34hr
32/pb
19points
J/
15points
53hr
25/pb
(2S)
15points
30hr
28/pb
33hr
16/pb
39hr
37/pb
11points
21points
39hr
18/pb
68hr
32/pb
13points
48hr
22/pb
23points
76hr
36/pb
23hr
22/pb
13points
43hr
42/pb
23points
28hr
26/pb
47hr
44/pb
 Assume 50,000 inclusive hadronic events are obtained at each energy point.
 If the statistics are optimized and systematic error dominant is considered,
the beam time will be lesser than above values.
Differentiation of BW
J/
J/
(2S)
Present test fitting
Fitting without experimental data  Cook a meal without rice
Tricks:
 Pseudo data: given by Breit-Wigner cross section with PDG parameters,
and consider energy spread, ISR correction and assumed background
as polynomial of level 1, set the error to be 3 % or 2%, and reasonable
beam unstability/fluctuation (b~0.1MeV).
 Theoretical cross section: calculated by iterative Breit-Wigner form
with free parameters, consider energy spread, ISR correction, assumed
background as Chebychev polynomial of level 2.
 Fitting tool: MINUIT.
 Aim: ① to learn how many scanned points are economic or efficient;
② what accuracy level could achieved with BESIII; ③ else more ?
Fiting method
Principle of least square with MINUIT
Cross section to be fitted:
High energy physics and nuclear physics 14, 585(1990)
Free parameters
Pseudo experimental cross section:
Chebychev polynomial
Gaussian, but >1.5%
Fixed parameters
Covariance
matrix
Correlation coefficient:
Correlation error matrix
(typical value, assumption)
Fitting method
Energy spread distribution with Gaussian form
Important for reliable fitting
Breit-Wigner cross section
Radiant factor
Theoretical total resonant cross section
(Can be calculated analytically)
Effective total resonant cross section
(calculated by Gaussian numerical integration)
Test fitting for J/
ASSUME
Cross section error: 3%
Beam unstability: b=0.1MeV
8 points
/ = 610-6
e/ = 210-3
/ = 210-4
Test fitting for S)
ASSUME
Cross section error: 3%
Beam unstability: b=0.1MeV
10 points
/ = 710-10
e/ = 210-3
/ = 410-4
Heavy charmonia scan at BESII
Suggested energy points for fine scan
R
 special fine scan with energy step：1~2MeV；
 to find new states or structures，to determine theirs parameters.
such as, leptonic width of Y(4260) et.al.
55
Estimation of beam time for J/ scan
Estimation of beam time for J/ scan
Strong and Electromagnetic
Relative Phase via
J/ψ Resonance Scan
Marco Destefanis
Università degli Studi di Torino
for the BESIII Collaboration
Beijing (China)
September 13, 2011
Energy Points Choice
3000
Only for phase measurement
3030
3083
3090
Can combine with J/ scan
3093
Apply for beam time: 5day?
Estimation of beam time for (2S) scan
Estimation of beam time for (2S) scan
Estimation of beam time for higher  scan
62
Estimation of beam time for higher  scan
63
Estimation of beam time for higher  scan
64
Estimation of beam time for higher  scan
For R fine scan, total integrated luminosity is 195 pb1,
the total beam time is about 2620 hours ~ 109 days
Improvement of ISR calculations
 Consider effect of transverse momentum of emitting photons
 Determine correct integral intervals of x and kt
 Calculate ISR integral analytically
 Interference between resonant and continuous final states
 Else more ?
Improved ISR formula
Two photons emission approximation
Effective c.o.m. energy for hadronic events (neglecting photon backward emitting, et.al.)
Observed experimental resonant cross section
Where, normalized transverse momentum distribution
In any scale
Plus sign
function
Improved ISR formula
Fractional longitudinal momentum
cc-pair production
forbidden region
Define new variable x
cc-pair production
permit region
if
(lightest decay final state )
or
(charmonium production)
where
In physics, correct ISR integral should be
numerical
Note: in former works
analytical
Must be different
Improvement of LUARLW
Up to now，LUARLU can simulate ISR inclusive
and parts of exclusive continuous chanels and JPC
= 1  resonances from hadronic threshold to 5 GeV.
Any new and possible production or decay channel can be added into LUARLW，
and used in the analysis of signal and background for different purposes。
LUARLW tuning
Compare true data with MC simulated distributions
If：
1. LUARLW “correct”
particles, ratio, momentum …
2. BES simulations reliable
time、space, decay…
Ngen data (unknown)
Trigger
trg
Generator
then：all distributions of data
and MC simulations agree well
 good MC parameters set
LUARLW
Ngen MC
Raw data
BESIII
simulation
Tune
parameters
Event
selection
Nobs data
NobsMC
BES III
raw date
had  NobsdataNgendata
= NobsMC NgenMC
Other problems
 Use energy measurement system in J/ and (2S) scan
- to calibrate beam energy independently instead of by observing peak
 Require reliable values of energy spread with independent way
 Gaussian integral  resonant widths
 no treat as a free parameter in fitting
 Determine covariance matrix in data analysis
- chi^2 in fitting convergence requirement  values of parameter and error
 Interference between exclusive resonant and continues states
 Improvement of data analysis
 Improvement and tuning of MC generators LUARLW
 ……
Conclusion
Not yet,
but we are making arduous efforts…