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…