Study of hc wpp and hc fKK

12017/6/13 Coll. Meeting in Summer of 2017

Xiaoshen Kang, Li Gong, Wenjing Zhu,Guofa Xu, Chunxu Yu

NKU && IHEP

Outline

• Motivation

• Study of J/y ghc; hc wpp

• Study of J/y ghc; hc fKK

• Summary

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Motivation

• hcfK+K- is reported by Belle Collaboration[1]. But the uncertainty is large.

• hc4p[2,3] and 6p[2,4] are also reported by BES3(BES2) .

• In this work we will search hcwpp decays together with hcfKK.

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[1] PRL 91 241802.[2] PR D86 092009.[3] EPJ C53 1.[4] PL B633 19.

Study of J/y ghc; hc wpp

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Data set

5

• BOSS version: 6.6.4

• Real dataJ/ y (09+12) 225 + 1087 Million

• Inclusive (09+12) 1225 Million

• Exclusive MCJ/y ghc ; hc wp+p- ; w p+p-p0

2017/6/13 Coll. Meeting in Summer of 2017

Event selection• Charged Tracks

𝑉𝑧 ≤ 10.0𝑐𝑚, 𝑉𝑟 ≤ 1.0𝑐𝑚 𝑐𝑜𝑠𝜃 ≤ 0.93 𝑁𝑐ℎ𝑟𝑔 = 4, 𝑄𝑡𝑜𝑡 = 0 𝑃𝐼𝐷: 𝑃𝑟𝑜𝑏 𝜋 > 𝑃𝑟𝑜𝑏 𝐾 ,𝑁𝜋 = 4

• Good Photons

0.86 < 𝑐𝑜𝑠𝜃 < 0.92 𝐸𝛾 ≥ 50𝑀𝑒𝑉 𝑐𝑜𝑠𝜃 < 0.8 𝐸𝛾 ≥ 25𝑀𝑒𝑉 𝐸𝑀𝐶 𝑇𝐷𝐶 0 ≤ 𝑡 ≤ 14 𝐴𝑛𝑔 𝛾, 𝑐ℎ𝑟𝑔 ≥ 10° 𝑁𝛾 ≥ 3

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• Minimize c2 to select the 3p combination

• c = 𝑀2 3p −𝑚2(w)

c25C40

7

Criteria Optimization

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Plots for data

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Dalitz plots

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3p from w

Background analysis

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Background with w, plots in M(3p)

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Background with w, Plots in M(wpp)

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Main channels with w

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Background without w, plots in M(3p)

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No peaking background in M(3p)!

Data driven

• Data driven : Bin By Bin fit method

– Fit w in M(3p) for each bin in M(5p )

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•Binned N(g5p)= (Nsig+ NBG_w+ NBG_non-w)•Fit fin M(3p)for each M(g5p)bin, (Nw)i•(Nw)i= (Nsig+ NBG_w)i•None w-background can be subtracted.•10 MeV/bin.

Result of data driven

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Without w in the final states With w in the final states

Fit formula

• PDF=Pdf(signal)+Pdf(background)

Pdf(signal) = MC_shape

Pdf(background) = Polynominal_bkg + peak_bkg

Polynominal_bkg 2nd Chebychev

Peak_bkgMC_shape (FSR + (1-a1)*wpp)

• Binned ML fit is performed

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Fit

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N(hC)=634.3±179.8

Signal

Peak BG

PolynominalBG

Br(hcwpp) = (2.4±0.7) × 10-4

Significance(hcwpp)= 3.5 s

Efficiency = 13.19%

Upper limit

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Systematic uncertainty

Source %

Number of J/y 0.6

Tracking 4×1.0

PID 4×2.0

Photon reconstruction 3×1.0

Intermediate decay 23.5

5C 2.0

Total 25.4

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Systematic uncertainty

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Background shape: 2nd -> 3rd Polynominal

Data driven: 60 bins -> 61 bins

Data driven: 60 bins -> 59 bins

Fit region : 2.45~3.05 -> 2.44~3.04 GeV/c2 Fit region : 2.45~3.05 -> 2.46~3.06 GeV/c2

Conclusion

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𝐿 𝑁′ = 0

𝐿(𝑁)

1

2𝜋𝜎𝑠𝑦𝑠𝑒− 𝑁′−𝑁 2

2𝜎2𝑠𝑦𝑠 𝑑𝑁

𝐵 h𝑐 → wpp =𝑁𝑢𝑝

𝑁𝐽/y × 𝐵(𝐽/y → gh𝑐) × 𝐵(w → ppp) × 𝐵(p0 → gg) ×

B(hcwpp) < 3.6×10-4 • The upper limit of B(hcwpp) is measured in this work.

• The significance is 3.5s

Study of J/y ghc; hc fKK

232017/6/13 Coll. Meeting in Summer of 2017

Data set

24

• BOSS version: 6.6.4

• Real dataJ/ y (09+12) 225 + 1087 Million

• Inclusive (09+12) 1225 Million

• Exclusive MCJ/y ghc ; hc fK+K- ; f K+K-

2017/6/13 Coll. Meeting in Summer of 2017

Event selection• Charged Tracks

𝑉𝑧 ≤ 10.0𝑐𝑚, 𝑉𝑟 ≤ 1.0𝑐𝑚 𝑐𝑜𝑠𝜃 ≤ 0.93 𝑁𝑐ℎ𝑟𝑔 = 2, 𝑄𝑡𝑜𝑡 = 0 𝑃𝐼𝐷: 𝑃𝑟𝑜𝑏 𝐾 > 𝑃𝑟𝑜𝑏 𝜋 ,𝑁𝜋 = 4

• Good Photons

0.86 < 𝑐𝑜𝑠𝜃 < 0.92 𝐸𝛾 ≥ 50𝑀𝑒𝑉 𝑐𝑜𝑠𝜃 < 0.8 𝐸𝛾 ≥ 25𝑀𝑒𝑉 𝐸𝑀𝐶 𝑇𝐷𝐶 0 ≤ 𝑡 ≤ 14 𝐴𝑛𝑔 𝛾, 𝑐ℎ𝑟𝑔 ≥ 10° 𝑁𝛾 ≥ 1

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• Minimize c2 to select the 2K combination

• c = 𝑀2 2K −𝑚2(f)

hc f K+ K-

M(KK)f

M(KK)other

Criteria Optimization

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c24C45

mass window :10 MeV/c2

• c24C45

• mass window : 10 MeV/c2

• Invariant mass of other K+K-

> 1.1 GeV/c2

M(KK) > 1.1 GeV/c2

Plots for data

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Background study

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Plot of main channels

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The fit of f

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Signal(f) : relativistic Breit-WignerGaus(m,s)Background : 𝑚 − 2𝑚𝐾

𝑎 exp(−𝑏𝑚 −

Dots with error bars are the bin by bin fit results and the red ones are the sidebands contribution. They are coincident with each other

Data and sidebands

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Fit model • Signal: (rBW×FM1×Damping factor)Gaus(m,s)

– rBW relativistic Breit-Wigner

– FM1 E3(g)

– Damping factor 𝐸20

𝐸𝛾𝐸0+ 𝐸

𝛾−𝐸

02

– Gaus(m,s) Gaussian function with free parameters

• Background : Polynominal BG + peak BG

– Polynominal BG : 3rd Chebychev

– Peak BG : MC shape (FSR + (1-a1)*fKK)

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Fit result

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Signal

Peak BG

PolynominalBG Sidebands

N(hcfKK) : 2739.6 ± 79.8Efficiency : 12.0%

B(hcfKK) =Nobs/(NJ/y*B(J/yghc)*B(fKK)*)=(2.10±0.06)×10-3

PDG:B(hcfKK)=(2.9±1.1)×10-3

Systematic uncertainty Source %

Number of J/y 0.6

Tracking 4×1.0

PID 4×2.0

Photon reconstruction 1×1.0

Intermediate decay 23.6

4C 1.0

f Reconstruction 0.3

M(KK)other 5.9

Fit region 1.3

Background 6.3

Total 26.8

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Systematic uncertainty

• Fit region: fit in regions [2.560~3.065] and [2.565~3.070] instead of [2.565~3.065], the different of number of signal events is consider to be systematic uncertainty (1.3%)

• Change the M(KK)other cut by ± 2 MeV/c2, the different of number of signal events is consider to be systematic uncertainty (5.9%)

• Background shape, replace the background with 2nd

Chebychev, and the systematic uncertainty is 6.3%

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Systematic uncertainty Fit region Nubmer of events Sys. Uncertainty (%)

Normal 2793.6±79.8

[2.560~3.065] 2828.8±187.5 1.3

[2.565~3.070] 2794.9±73.4 0.05

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M(KK)other Nubmer of events Sys. Uncertainty (%)

+2 MeV/c2 2678.2±138.6 4.1

-2 MeV/c2 2810.1±161.5 5.9

Background Nubmer of events Sys. Uncertainty (%)

2nd 2617.9±70.1 6.3

Smear MC

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To study the difference of M(KK)f between data and MC, we enlarge the resolution of charged track by smearing it with a Gaussian. Different between the efficiencise is consider to be systematic uncertainty.(0.3%)

Conclusion

• B(hcfKK) is measured in this work.B(hcfKK) = (2.10±0.06±0.56)×10-3

• Our result is consistent with PDG’s value[1].• Both the Statistical Error and Systematic Uncertainty are

better than Belle’s result.

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[1]Belle Phys. Rev. Lett. 91 241802

Summary

• Upper limit of B(hcwpp) is provide.

• B(hcfKK) is measured in this work. Both the Statistical Error and Systematic Uncertainty are better than Belle’s result.

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Backup

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