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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
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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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