The progress and prospect on charm mixing

Transcription

1 BINP The progress and prospect on charm mixing Vitaly Vorobyev Budker Institute of Nuclear Physics and Novosibirsk State University On behalf of Belle & Belle II Collaborations 2 nd international workshop on High Intensity Electron-Positron Accelerator 19 th March 2018, UCAS, Beijing

2 The charm mixing parameters Mass eigenstates หD 1,2 ൿ = pȁd 0 ± qȁഥd 0, p 2 + q 2 = 1 The charm mixing parameters x m 2 m 1 Γ, y Γ 2 Γ 1 2Γ The observable parameter λ f q p Charm forms the only neutral meson system with the heavy up quark, Γ Γ 1 + Γ 2 2 ҧ A f A f, A f f H D 0, ҧ A f f H ഥD 0 CP violation Direct: f H D 0 CP f H ഥD 0 In mixing: q/p 1 In interference between mixing and decay: Im λ f 0 Long distances (dominant) Short distances The Standard Model expectation x y sin 2 θ C SU 3 f breaking 2 Clear signals of new dynamics: y x 1% CP violation >

3 Experimental status arxiv: x = 0.32 ± 0.14 % y = % q/p = arg q/p = No CPV The first evidence by Belle and BaBar Phys. Rev. Lett. 98, (2007) Phys. Rev. Lett. 98, (2007) Charm mixing is well established No CP violation observed in charm yet No mixing 3

4 Experimental landscape D ഥD threshold pp collisions Asymmetric e + Υ 4S 4

5 Charm mixing observables and facilities Classes of observables (I. Bigi) Wrong-sign D 0 decays Semileptonic Hadronic (D 0 K + π time ind.) Non-exponential D 0 decay rate evolutions (D 0 K + π time dep.) Different D 0 lifetimes in different channels (D 0 h + h ) D 0 and ഥD 0 produced in e + e D 0 ഥD 0 decaying into two seemingly identical final states LHCb B factory c-τ factory Charm production Coherence Non-coherent Coherent CMS boost γβ D 1 γβ D 1 γβ D 1 5

6 Charm decay rates Time-dependent Incoherent D ± Dπ ±, B DX, e + e ccҧ D ഥDX, pp ccx ҧ Boost LHCb: γβ D 1 f H D 0 t 2 = e Γt A f 2 1 y Reλf + x Imλ f Γt + O x 2, y 2 f H D 0 2 A f 2 1 y Reλf x Imλ f + O x 2, y 2 B factory: γβ D 1 c-τ factory: γβ D 1 Time-integrated Coherent (at rest) e + e D 0 ഥD 0, C+: D 0 ഥD 0 γ, C : D 0 ഥD 0 π 0 ij H D 0 ഥD 0 i H D 0 j H ഥD 0 + C i H ഥD 0 j H D 0 ij H D 0 ഥD 0 2 A 2 2 i A 2 j ζc C x Im ξ C ζ C y Re ξ C ζ C + O x 2, y 2 ξ C p q 1 + Cλ iλ j, ζ C p q (λ j + Cλ i ) 6

7 The progress Selected experimental results 7

8 D 0 Kπ time-dependent WS Γ D 0 t f WS = e t τ A f 2 RD + R D y t τ R M t τ 2 x x cos δ Kπ + y sin δ Kπ R + D Br D0 K + π y Br D y cos δ Kπ x sin δ 0 K π + Kπ R M x 2 + y 2 /2 A D R D + R D R + D + R D BaBar [1]: 384 fb 1, D + D 0 π + y = 9.7 ± 4.4 ± R D = 3.03 ± Belle [2]: 976 fb 1, D + D 0 π + y = 4.6 ± R D = 3.53 ± LHCb [3]: 5 fb 1, D + D 0 π + y = 5.28 ± 0.45 ± x 2 = ± ± R D = ± ± A D = 0.1 ± < p/q < 68.3% CL [3] x 2 [10 3 ] [3] [1] Phys. Rev. Lett. 98, (2007) (BaBar) [2] Phys. Rev. Lett. 112, (2014) (Belle) [3] Phys. Rev. D97, (R) (2018) (LHCb) 8

9 Measurements with quantum correlations The method exploits the difference between correlated (double tagged) and uncorrelated (single tagged) decay rates CLEO-c [1]: 0.82 fb ψ(3770), fit of 261 yields y = 4.2 ± 2.0 ± 1.0 % R D = ± ± % cos δ Kπ = ± 0.22 ± 0.07 sin δ Kπ = 0.01 ± 0.41 ± 0.04 BESIII: 2.92 fb ψ(3770) y and R D are taken as an external input cos δ Kπ = 1.02 ± 0.11 ± 0.06 ± 0.01 Time-integrated C = 1 correlations Γ i, j i D 2 j D 1 i D 1 j D O x 2, y 2 [1] [1] Phys. Rev. D86, (2012) (CLEO-c) [2] Phys. Lett. B 734, 277 (2014) (BESIII) 9

10 Time-dependent D 0 h + h y CP η CP Γ D 0 f + Γ ഥD 0 f 2Γ D 0 K π + 1 y cos φ 1 2 A mx sin φ y CP τ D0 K π + τ D 0 K K + 1 LHCb [1]*: 29 pb 1, D + D 0 π + y CP = 0.55 ± 0.63 ± 0.41 % BaBar [2]: 468 fb 1, D 0 K π ±, K K +, π π + y CP = 0.72 ± 0.18 ± 0.12 % Belle [3]: 540 fb 1, D 0 K π ±, K K +, π π + y CP = 1.31 ± 0.32 ± 0.25 % [1] [2] [1] JHEP 04, 129 (2012) (LHCb) [2] Phys. Rev. D87, (2013) (BaBar) [3] Phys. Rev. Lett. 98, (2007) (Belle) *There are many other LHCb publications on CP violation in the D 0 h + h modes 10

11 D 0 f CP with quantum correlations y CP 1 4 B D CP l B D CP+ l B D CP+ l B D CP l, B D CP l = N CP±;l N CP± ε CP± ε CP±;l BESIII [1]: 2.92 fb GeV y CP = 2.0 ± 1.3 ± 0.7 % Single tag: D f CP Quantum correlated D ഥD f CP + Klμ Systematic uncertainty has statistical origin [1] Phys. Lett. B744, 339 (2015) 11

12 D 0 K S 0 π + π Dalitz plot analysis Time-dependent Dalitz plot analysis P D t, m + 2, m 2 Γe Γt A D 2 Γt Re A D A ഥD y + ix Sensitivity to the charm mixing parameters due to the strong phase variation over the Dalitz plot A m + 2, m 2 from a D 0 K S 0 π + π decay model BaBar [1]: fb 1, D + D 0 π + x = 0.16 ± 0.23 ± 0.12 ± 0.08 % y = 0.57 ± 0.20 ± 0.13 ± 0.07 % Belle [2]: 921 fb 1, D + D 0 π + x = 0.56 ± 0.19 ± 0.08 ± 0.08 % y = 0.30 ± 0.15 ± 0.05 ± 0.07 % q/p = 0.90 ± 0.16 ± 0.05 ± 0.06 arg q/p = 6 ± 11 ± 3 ± 4 The most precise single measurement of the charm mixing parameters [1] [2] [1] Phys. Rev. Lett. 105, (2010) (BaBar) [2] Phys. Rev. D89, (2014) (Belle) 12

13 Model-independent Dalitz plot analysis A way to eliminate (difficult to control) model dependency of a multibody decay analysis Binned time-dependent Dalitz plot analysis [1,2] P D t, i e Γt K i Γt K i K i C i y + S i x P ഥD t, i e Γt K i Γt K i K i C i y S i x C i and S i are measured in coherent D 0 ഥD 0 pair decays [3] [3] CLEO-c [3] LHCb [4]: 1.0 fb 7 TeV, D + D 0 π + x = 0.86 ± 0.53 ± 0.17 % y = ± 0.46 ± 0.13 % [1] Phys. Rev. D68, (2003) [2] Phys. Rev. D82, (2010) (Bondar et al.) [3] Phys. Rev. D82, (2010) (CLEO-c) [4] JHEP 04, 033 (2016) (LHCb) The first model-independent measurement of the charm mixing parameters Z i = Di A D A ഥD dm dm Di A 2 D dm 2 + dm 2 Di A ഥD 2 dm 2 + dm2 C i = Re Z i, S i = Im Z i 13

14 D 0 K S 0 π + π with quantum correlations Coherent C = ±1 and non-coherent decays e + e ψ 4040 D ഥD Coherent C = 1: D 0 ഥD 0 D 0 ഥD 0 π 0 M ij = K i K j + K i K j 2 K i K j K i K j C i C j + S i S j Coherent C = +1: D 0 ഥD 0 D 0 ഥD 0 γ M + ij = K i K j + K i K j 2 K i K j K i K j C i C j + S i S j +2K j K i K i yc i xs i + 2K j K i K i yc i + xs i +2K i K j K j yc j xs j + 2K i K j K j yc j + xs j Incoherent D D + D D 0 π + K i = K i + K i K i yc i + xs i [1] Phys. Rev. D82, (2010) [2] Phys. Rev. D80, (2009) (CLEO-c) Measurement of the charm mixing and the phase parameters in a single experiment CLEO-c [2] 14

15 The prospects Estimates and expectations 15

16 Future landscape Super c-τ factory L = cm 2 s 1 Detector upgrade Trigger improvements Operation at higher luminosity (tens of pp interactions per event) Increased hermeticity and K S 0 efficiency Improved IP and D vertex resolution, K/π separation and π 0 reconstruction Added PID and μ ID in end caps w.r.t. Belle HIEPA BINP Super c-τ factory 16

17 Timescale 17

18 Charm production σ pp D 0 13 TeV 2 mb σ e + e cc Υ 4S 1.3 nb σ e + e cc ψ nb Parameter Decay time Incoherent decays Coherent decays Belle+BaBar (1.5 ab 1 ) Belle II (50 ab 1 ) LHCb (5 fb 1 ) LHCb (50 fb 1 ) Super c-τ (10 ab 1 ) N D 0 K π + untagged, [1] 100 N D + D 0 π +, D 0 K π +, [2] 140 [2] 100 [1] 7000 [1] 20* N D + K π + π +, [3] [1] [1] 200 N D s + φπ +, [1] 1000 [1] 40 * Expected yield of ψ 3770 D 0 ഥD 0 K π + K + π is shown for a Super c-τ factory [1] LHCb Collaboration, Eur. Phys. J. C73, 2373 (2013) «Implications of LHCb measurements and future prospects» [2] Physics at Super B Factory, arxiv: [hep-ex] [3] Phys. Rev. Lett. 102, (2009) 18

19 Future precision An order of magnitude precision improvement can be achieved in the next decade The numbers shown are very approximate. Analysis of systematic uncertainties is needed [1] Physics at Super B Factory, arxiv: [hep-ex], talk by M. KEK FF 2014 [2] Implications of LHCb measurements and future prospects, Eur. Phys. J. C73, 2373 (2013) [3] A. Bondar et al., Phys. Rev. D82, (2010) Parameter Belle II 50 ab 1 LHCb 50 fb 1 WS semileptonic Super 10 ab 1 R M O O ? D Kπ WS decays y, y, cos δ Kπ R D, A D, ?? D h + h (CP eigenstates) y CP, A Γ, O 0.1? D 0 K S 0 π + π Dalitz plot analysis x, O 1 [3] y, O 1 [3] q/p O 0.01 [3] arg q/p 4 3 O 1 [3] 19

20 Global fit for Belle 50 ab 1 Alan Schwartz, IX th CKM UT Workshop (Dec. 1, 2016) No mixing No CPV Current fit Year

21 Global fit for LHCb Upgr. Phase 300 fb 1 CERN-LHCC (Feb. 8, 2017) Year

22 Conclusions 1. Precise measurement of the charm mixing is a fundamental test of the SM 2. The existing measurements are consistent with the SM expectations 3. LHCb and Belle II are going to measure the charm mixing parameters at the precision level of O 10 4 access CP violation in charm at the SM values (A Γ 10 5 ) 4. A Super c-τ factory with L = cm 2 s 1 is competitive for the charm mixing measurement 5. Measurements with quantum correlations will play an important role for the future charm mixing measurements 22