Suggested plan of charmonia and QCD study scan at BESIII Hu Haiming October 12-16, 2011 Hangzhou.
-
Upload
christine-hodge -
Category
Documents
-
view
212 -
download
0
Transcript of Suggested plan of charmonia and QCD study scan at BESIII Hu Haiming October 12-16, 2011 Hangzhou.
Suggested plan of charmonia Suggested plan of charmonia and and
QCD study scan at BESIII 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
BESIII physics
Charm
Uncharm
tau
R&QCD
R(s) fine scan (uds+c)
QED & QCD (s), (g-2)multiplicity inclusive (correlation)exclusiveform factorsfragmentation functionsBose-Einstein correlation
Mass
Decay channels
Light hadron spectrumJ/ data
Light charmonium (2S) data
D physics (3770) data
Heavy charmonia
(4040)(4190)(4415)X, Y, Z ……
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.
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
Estimation of beam time
Formula used in beam time estimation
BEPCII luminosity:
Time estimation of data taking:
The related quantities are estimated as following
Formula used in beam time estimationHadronic 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
Measured values
Related errors (%)
BESII:
BESIII: ?2.53.0%
R Measurements at BESII
Form factors of e+ e p pProduction amplitude :
Differential cross section :
With large statistic data sample, GE and GM could be obtained by fitting angular
distribution.
Electronic & magnetic form factors:
pQCD predicts
,
Hadronic current has two independent form factors:
But, with BESII data, and assume |GM=GE = G|
BESII data for pp
23/4/21Wenbiao Yan USTC
16
FENICE data near threshold
16.011.066.0
)(
)(
nnee
ppee
QCD (quark model) prediction
4)(
)(2
2
d
u
Q
Q
nnee
ppee
?Puzzle
An intermediate coherent isovector state serving as an intermediary between e+e- and BB
*
QCD 10-24 sec
J. Ellis and M. Karliner hep-ph/010825922
01
01
1
1
)(
)(
i
i
i
i
e
e
AeA
AeA
nnee
ppeef
fBESIII could collect data around 2.02.8 GeV , BB pairs
,,,,,, 0000ee
QCD: (e+e (e+e (e+e if at any particular energy, an I = 1 or I =0 resonance dominates, the above ratio will not be maintained!
Ratio puzzle of e+ e baryon pairs
Measurement of s at BESIISolve equation
PDG2006
Obtain coupling constant at every energies ,and then evolve them to 5 GeV with
Weighted average
errors
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 precisionUncertainty 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
total widthnominal mass
21
Known charmonia
BES’s measurements of BW parametersJ/Phys. Lett. B355 (1995)Energy points : 23
Total luminosity : 82.28/nb
Maximum error : 11%
Processes analyzed:
Consider uncertainty of beam energy calibration, taking data at 23 energy points were reasonable.
Why so many energy points were scanned
?
BES’s measurements of BW parameters(2S)Phys. Lett. B550 (2002)
Energy points : 24Total luminosity : 1.149/pb
Maximum error : 10%
Events analyzed
Fit simultaneously
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 eventsno 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
30
Coupling channel model
Potential models predictionhep-ph/0505002
“Higher Charmonia”Nonrelativistic potential model
Relativizied potential model with QCDExperimental and theoretical spectrum of charmonium:
Solid line: experimentBroken line: model
Phys. ReV. D32, 189 (1985)
Potential model predictions
Phys. ReV. D32, 189 (1985)
Potential model predictions
Phys. ReV. D32, 189 (1985)
Potential model predictions
35
Phys. ReV. D32, 189 (1985)
Potential model predictions
36
Phys. ReV. D32, 189 (1985)
Potential model predictions
PHIPSI2009
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). BABAR-PUP-05/029
hep-ex/0506081
!
BESII missed 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?
Phi to Psi 2009 Galina Pakhlova
DD DD* D*D*
DDπ
DD*π
Λ+c Λ
c
Sum of all exclusive contributions
Only small room for unaccounted contributions• Charm strange final states
Limited inclusive data above 4.5 GeV• 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
?
BESII value 78.8±16.1
?
Comparison of theory and experiment
BESII value 80.4±24.7
?
Comparison of theory and experiment
VEPP-4’s measurements of MJ/ and M(2S)
hep-ex/0306050Energy points : 7
Total luminosity : 40+10/nb
J/ (2S)
Scan : 3+1 runs (E~0.6 0.45MeV) Scan : 3 run (E~0.9 MeV)
Total luminosity : 76/nb
Highlight
1. Precise energy calibration2. Precise energy spread calculation3. …
44
BEPCII energy measurement system
Two runs (2S) fitting
Off-line data fitting:M =Mfit –MPDG =0.02 ± 0.05 MeV=M/2=0.010.03 MeVPDG2010:3686.09 ± 0.04 MeV
Stability of the EMS
Accuracy of the beam energy measurement:
/ ~ 2×10-5 (36 keV).
Event selection in Ntot of J/ with BESIII Events types analyzed
Event selection in Ntot of (2S) at BESIII Events types analyzed Error analysis
9points7points
J/
(2S)
25hr12/pb
33hr16/pb
39hr18/pb
48hr22/pb
53hr25/pb
60hr28/pb
64hr30/pb
68hr32/pb
76hr36/pb
14hr13/pb
20hr18/pb
23hr22/pb
28hr26/pb
30hr28/pb
34hr32/pb
39hr37/pb
43hr42/pb
47hr44/pb
Estimation of beam time11points 13points
17points 19points 21points 23points15points
7points 9points 11points 13points
15points 17points 19points 21points23points
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 BWJ/ J/ (2S)
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 ?
Fitting without experimental data Cook a meal without rice
Present test fitting
Fiting methodPrinciple of least square with MINUIT
Pseudo experimental cross section:
Cross section to be fitted:
Free parameters
Fixed parameters
Chebychev polynomial
Covariancematrix
Correlation error matrix
High energy physics and nuclear physics 14, 585(1990)
Gaussian, but >1.5%
(typical value, assumption)Correlation coefficient:
Fitting methodEnergy spread distribution with Gaussian form
Important for reliable fittingBreit-Wigner cross section
Radiant factor
Theoretical total resonant cross section
Effective total resonant cross section
(Can be calculated analytically)
(calculated by Gaussian numerical integration)
ASSUME Cross section error: 3% Beam unstability: b=0.1MeV
/ = 610-6 e/ = 210-
3 / = 210-4
Test fitting for J/
8 points
ASSUME Cross section error: 3% Beam unstability: b=0.1MeV
/ = 710-10 e/ = 210-3 / = 410-4
Test fitting for S
10 points
Heavy charmonia scan at BESII
Suggested energy points for fine scan
55
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.
Estimation of beam time for J/ scan
Estimation of beam time for J/ scan
Strong and ElectromagneticStrong and Electromagnetic
Relative Phase viaRelative Phase via
J/J/ψψ Resonance Scan Resonance ScanMarco Destefanis Università degli Studi di Torino
Beijing (China)September 13, 2011
for the BESIII Collaboration
Energy Points ChoiceEnergy Points Choice
3000
3030
3083
3090
3093
Can combine with J/ scan
Only for phase measurement
Apply for beam time: 5day?
Estimation of beam time for (2S) scan
Estimation of beam time for (2S) scan
62
continue
Estimation of beam time for higher scan
63
continue
Estimation of beam time for higher scan
64
continue
Estimation of beam time for higher scan
For R fine scan, total integrated luminosity is 195 pb, the total beam time is about 2620 hours ~ 109 days
continue
Estimation of beam time for higher scan
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 ?
Improvement of ISR calculations
Improved ISR formulaTwo 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
Plus signfunction
In any scale
Improved ISR formulaFractional longitudinal momentum
Define new variable x
if
or
where
In physics, correct ISR integral should be
analyticalnumerical
(charmonium production)
(lightest decay final state )
Note: in former works
Must be different
cc-pair production permit region
cc-pair production forbidden region
Improvement of LUARLWUp 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。
Compare true data with MC simulated distributions
Triggertrg
Raw data
GeneratorLUARLW
BESIII simulation
Eventselection
Nobs data
Ngen data (unknown)
Ngen MC
NobsMC
BES IIIraw dateTune
parameters
If :1. LUARLW “correct” particles, ratio, momentum …
2. BES simulations reliable time 、 space, decay…
had Nobs
dataNgendata
= NobsMC
NgenMC
then : all distributions of data and MC simulations agree well good MC parameters set
LUARLW tuning
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
……
Other problems
Conclusion
Not yet,
but we are making arduous efforts…