decays at BaBar and Belle Alessandro Pilloni Sapienza Universit di - - PowerPoint PPT Presentation
Recent results on violation of discrete symmetries in charm decays at BaBar and Belle Alessandro Pilloni Sapienza Universit di Roma INFN sez. Roma 1 on behalf of the BaBar Collaboration CHARM 2015 Detroit May 21 st , 2015
“Sapienza” Università di Roma – INFN sez. Roma 1 CHARM 2015 Detroit – May 21st, 2015
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PRD 87, 052010 (2013) 𝑀 = 476 fb−1
0𝐿+, 𝐸𝑡 + → 𝐿𝑇 0𝐿+, 𝐸𝑡 + → 𝐿𝑇 0𝜌+ PRD 87, 052012 (2013) 𝑀 = 469 fb−1
0𝜌+𝜌− PRD 89, 091103 (2014) 𝑀 = 921 fb−1
(the use of charge conjugate reactions is implied thourough)
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In the SM, CPV in processes involving charm hadrons is expected to be small, at the level of 10−3 or less Any CPV signal is likely due to New Physics, although sizeable long-distance effects might affect some SM predictions GIM and CKM suppression 𝐵𝐷𝑄 ∝ log 𝑛𝑐 𝑛𝑑 × 𝜇5 = 𝑃(10−3)
No top enhancement!
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∫ 𝑀 𝑒𝑢 ∼ 517 fb−1 close to the Υ 4𝑇 , Υ(2𝑇), Υ(3𝑇) peaks, 670 × 106 𝑑 𝑑 pairs The Babar detector was located at the interaction point of PEP II at SLAC Asymmetric 𝑓+𝑓− collider, mostly at 𝑡 ∼ 10.58 GeV
Drift Chamber: 40 layers Silicon Vertex Tracker (SVT): 5 double layers Cherenkov detector (DIRC): 144 fused silica bars; 11000 PMT
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Singly Cabibbo-suppressed decays, uniquely sensitive to new physics Probe gluonic penguin and chromomagnetic dipole operators 3-body decay allows the search for CP asymmetries in the Dalitz plot
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BaBar coll. PRD 87, 052010 (2013) 𝑀 = 476 fb−1
removed
𝐷𝑁 help in
discriminating signal from background
228k 𝐸+ signal yield, 92% purity Search for CPV with:
1. 𝐵𝐷𝑄 integrated over the Dalitz plot 2. 𝐵𝐷𝑄 in 4 Dalitz plot regions 3. Comparison of binned 𝐸± Dalitz plot 4. Comparison of Legendre polynomial moment distributions for 𝐿+𝐿− and 𝐿−𝜌+ systems 5. Comparison of parametrized fits to Dalitz plot (model-dependent)
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Asymmetry integrated
𝑩𝑫𝑸 = 𝟏. 𝟒𝟖 ± 𝟏. 𝟒𝟏 ± 𝟏. 𝟐𝟔 %
(A) (B) (D) (C)
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Normalized residual analysis Δ =
𝑜 𝐸+ −𝑆𝑜 𝐸− 𝜏2 𝐸+ +𝑆2𝜏2 𝐸− ,
𝑆 = 𝑂(𝐸+)/𝜗+ 𝑂(𝐸−)/𝜗− = 1.020 ± 0.006
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Two body mass distributions 𝑛(𝐿+𝐿−) and 𝑛(𝐿−𝜌+) weighted by (2𝑚 + 1)/4𝜌 𝑄𝑚(cos 𝜄𝐼) 𝑌𝑗
𝑚 = 𝑋
𝑗 𝑚 𝐸+ −𝑆𝑋 𝑗 𝑚 𝐸−
𝜏𝑗
𝑚 2 𝐸+ +𝑆2𝜏𝑗 𝑚 2 𝐸− , with 𝑋
𝑗 𝑚 the weighted 𝑗th mass bin, and 0 ≤ 𝑚 ≤ 7
consistent with no CPV at 11% and 13% level Method introduced by Babar coll. PRD 76, 011102 (2007) Legendre polynomial moment analysis:
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Fit to Dalitz plot using isobar model Firstly to combined 𝐸± datasets (no CPV)
Resonances modeled with RBW 𝑔
0(980) with an effective BW
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Allow CPV in resonances with at least 1% fit fraction
𝑠
𝐷𝑄 = 𝑁𝑠 2− 𝑁𝑠 2 𝑁𝑠 2+ 𝑁𝑠 2, Δ𝜚𝐷𝑄 = 𝜚𝑠 − 𝜚𝑠
𝑦𝑠 = 𝑁𝑠 cos 𝜚𝑠, 𝑧𝑠 = 𝑁𝑠 sin 𝜚𝑠
+ → 𝐿 𝑇 0𝐿+, 𝐸𝑇 + → 𝐿 𝑇 0𝜌+
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𝐸𝑇
+ → 𝐿𝑇 0𝜌+
𝐸𝑡
+ → 𝐿𝑇 0𝐿+
𝐸+ → 𝐿𝑇
0𝐿+
159k events 288k events 14k events BaBar coll. PRD 87, 052012 𝑀 = 469 fb−1
In the SM 𝐵𝐷𝑄 expected to be dominated by CPV in 𝐿0 − 𝐿0 mixing
0 flight length > 3 × significance
Multivariate analysis to further improve S/B
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A large sample of 𝜌 and 𝐿 tracks from 𝐶 𝐶 events to estimate detector-induced asymmetries Correction factors have been measured and applied to the signal
ratio error 𝜌 𝐿
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𝐸𝑇
+ → 𝐿𝑇 0𝜌+
𝐸𝑡
+ → 𝐿𝑇 0𝐿+
𝐸+ → 𝐿𝑇
0𝐿+
𝐵𝐷𝑄 = 0.13 ± 0.36 % 𝐵𝐷𝑄 = −0.05 ± 0.23 % 𝐵𝐷𝑄 = 0.6 ± 2.0 %
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𝐿0 produced, − sign 𝐿0 produced, + sign
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∫ 𝑀 𝑒𝑢 ∼ 977 fb−1 close to the Υ(1𝑇 − 5𝑇) peaks, 1.3 × 109 𝑑 𝑑 pairs The Belle detector was located at the interaction point at KEKB in Japan
𝑇 0𝜌+𝜌−
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𝑒Γ𝐸0 𝑓−Γ𝑢 𝑒𝑢 ∝ 𝐵𝑔
2 + 𝑟
𝑞
2
𝐵𝑔
2
cosh Γ𝑧𝑢 + 𝐵𝑔
2 − 𝑟
𝑞
2
𝐵𝑔
2
cos Γ𝑦𝑢 +2𝑆𝑓 𝑟 𝑞 𝐵𝑔𝐵𝑔
∗
sinh Γ𝑧𝑢 − 2𝐽𝑛 𝑟 𝑞 𝐵𝑔𝐵𝑔
∗
sin Γ𝑦𝑢 𝑒Γ𝐸0 𝑓−Γ𝑢 𝑒𝑢 ∝ 𝐵𝑔
2 + 𝑞
𝑟
2
𝐵𝑔
2
cosh Γ𝑧𝑢 + 𝐵𝑔
2 − 𝑞
𝑟
2
𝐵𝑔
2
cos Γ𝑦𝑢 +2𝑆𝑓 𝑞 𝑟 𝐵𝑔𝐵𝑔
∗
sinh Γ𝑧𝑢 − 2𝐽𝑛 𝑞 𝑟 𝐵𝑔𝐵𝑔
∗
sin Γ𝑦𝑢 Mass eigenstates 𝐸1,2 = 𝑞 𝐸0 ± 𝑟 𝐸0
Mixing parameters 𝑦 = Δ𝑛
Γ , 𝑧 = ΔΓ 2Γ
Mixing CPV 𝑟
𝑞 ≠ 1
Interference CPV arg 𝑟
𝑞 ≠ 0
𝑓− 𝑓+ 𝐸∗ 𝐸0 𝜌 𝜌𝑡 𝜌 𝜌 𝜌 𝑚𝑒𝑓𝑑 𝐿𝑇
beamspot
fit 𝐸0 vtx fit 𝐿𝑇
0 vtx
𝑇 0𝜌+𝜌−
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Total amplitude parametrized as a sum of quasi two-body resonant amplitudes (isobar model)
𝐵𝑔 =
𝑠
𝑏𝑠 𝑓𝑗𝜚𝑠𝐵𝑠(𝑛−
2, 𝑛+ 2) ,
𝐵𝑔 =
𝑠
𝑏𝑠 𝑓𝑗𝜚𝑠𝐵𝑠(𝑛−
2, 𝑛+ 2) ,
𝑛±
2 = 𝑛2(𝐿𝑇 0𝜌±)
A time-dependent Dalitz plot analysis is needed to extract mixing and CPV parameters
+
𝑚𝑒𝑓𝑑 𝑑 𝛾𝛿 ⋅ 𝑞𝐸0 𝑞𝐸0 , 𝛾𝛿 = 𝑞𝐸0 𝑛𝐸0
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Belle coll. PRD 89, 091103(R) (2014) 𝑅 signal region 𝑁 signal region
𝑞𝐸 > 3.1 GeV @Υ(5𝑇),
poorly determined 𝑢
𝑅 = 𝑁𝐸∗ − 𝑁𝐸 − 𝑁𝜌
2D fit to 𝑁𝐸 and 𝑅, Yield 1.2M, purity 96% Signal region in 𝑁𝐸 − 𝑁𝐸
𝑄𝐸𝐻 < 15 MeV
and 𝑅 ∈ 5.75, 5.95 MeV
𝑀 = 977 fb−1
𝑇 0𝜌+𝜌−
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RBW K matrix LASS
𝒏−
𝟑 (GeV𝟑/𝒅𝟓)
𝒏𝝆𝝆
𝟑
(GeV𝟑/𝒅𝟓) 𝒏−
𝟑 (GeV𝟑/𝒅𝟓)
𝒏+
𝟑 (GeV𝟑/𝒅𝟓)
𝒏+
𝟑 (GeV𝟑/𝒅𝟓)
𝑇 0𝜌+𝜌−: results
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(𝑏𝑠, 𝜚𝑠) consistent with (𝑏
𝑠, 𝜚 𝑠): no CPV in decay, set 𝐵 𝑔 = 𝐵𝑔 in the fit
1𝜏, no CPV 2𝜏, no CPV 2𝜏, CPV Fit projection
Mixing significance at 2.5𝜏 No evidence for CPV 𝜐 = 410.3 ± 0.6 fs, to compare with 𝜐 = 410.1 ± 1.5 fs (PDG 2014)
Third error on DP model
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Thank you!
Charm CPV is a powerful tool to search BSM physics! An overview of recent BaBar and Belle results has been presented:
using different approaches
+ → 𝐿𝑇 0𝐿+ and 𝐸𝑡 + → 𝐿𝑇 0𝜌+
decays at BaBar
0𝜌+𝜌− at Belle
No evidence of CPV found so far
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PRD 87, 052010 (2013) PRD 87, 052012 (2013) JHEP 1302, 098 (2013) PRL 104, 181602 (2010) (contribution of CP asymmetry of 𝐿𝑇
0 subtracted)
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