B. Hoeneisen. Universidad San Francisco de Quito Representing the DØ Collaboration Flavor Physics and CP violation (2013)

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1 Status report on the like-sign dimuon charge asymmetry in p p collisions and Measurement of the direct CP asymmetry in B J/ψK and B J/ψπ decays B. Hoeneisen Universidad San Francisco de Quito Representing the DØ Collaboration Flavor Physics and CP violation (2013)

2 η = 0 η = 1 [m] Muon Scintillators 5 Muon Chambers η = 2 0 Shielding η = 3 Calorimeter Toroid The DØ detector. 1

3 Status report on the like-sign dimuon charge asymmetry in p p collisions 2

4 1. Motivation: (in 1992!) CP violation in mixing of B 0 and B 0 s Example: p p b bx B B 0 X B B 0 X µ µ X, p p bbx B + B 0 X B + B 0 X µ + µ + X. A N(µ+ µ + ) N(µ µ ) N(µ + µ + ) + N(µ µ ) ; a n(µ+ ) n(µ ) n(µ + ) + n(µ ) A CP A A bkg ; a CP = a a bkg. Model independent asymmetries: A CP and a CP are normalized to all muons, while the normalizations of A S and a S exclude muons from kaon and pion decay. 3

5 2. History Residual asymmetry A CP = A A bkg measured with different integrated luminosities Ldt. Ldt asymmetry ACP * (DO), Phys.Rev. D 1.0 fb 1 ( )% 1.7σ 74, (2006) 6.1 fb 1 ( )% 3.2σ 82, (2010) 9.0 fb 1 ( )% 3.9σ 84, (2011) 10.5 fb 1??σ (2013) * Discrepancy with A mix CP (SM) only 4

6 Asymmetry a - a bkg DØ, 9.0 fb -1 - Asymmetry a bkg - Asymmetry a (a) p T (µ) [GeV] DØ, 9.0 fb -1 (b) p T (µ) [GeV] The closure test with inclusive muons. 5

7 3. CPV in interference of B 0 Example: p p b bx B B 0 X B D + D X; B µ X; D µ X, p p bbx B + B 0 X B + D + D X; B + µ + X; D + µ + X. D + D is CP-even. dγ( B 0 D + D ) dt dγ(b 0 D + D ) dt exp( Γ d t)[1 + S sin( m d t)], exp( Γ d t)[1 S sin( m d t)]. 6

8 For this decay B 0 (B 0 ) D + D : A int S = S x d 1 + x 2. d This asymmetry is numerically LARGE because S = sin(2β) = and x d m d /Γ d = CPV in interference does not contribute to a CP. 7

9 Comparison between experiment (2011) and the standard model for B 0 and B 0 s: a S = ( )%, a mix S (SM) = ( )%, (SM) = ( )%. a int S A S = ( )%, A mix S (SM) = ( )%, (SM) = ( )%. A int S What is the cause of this discrepancy? 8

10 Recent experiments: (after (Heavy Flavor Averaging Group), arxiv: (2012)) a d sl = V.M. Abazov et al. (DØ Collaboration), Phys. Rev. D 86, (2012). a s sl = V.M. Abazov et al. (DØ Collaboration), Phys. Rev. Lett. 110, (2013). a s sl = LHCb Collaboration, Conference report LHCb- CONF (2012) a d sl = BaBar at Beauty conference (2013), not included in next slide 9

11 4. Experimental constraints Contributions to A S allowed by experiments: (compare with A S = ( )%) Process Allowed A S Mixing of B 0 ( )% Mixing of Bs 0 ( )% * Interference of B 0 ( )% (SM) Interference of Bs 0 ( )% (SM) CPV in b c c q decays ( )% a (b) in b µx decays ( )% a (c) in c µx decays ( )% G. Borissov and B. Hoeneisen, Phys. Rev. D 87, (2013) *From Bs 0 J/ψφ, assuming that new physics CPV is not cancelled by penguin contributions, a s sl = ( )%, and this entry becomes negligible. 10

12 5. Interpretation A S A int S = A int S + Amix S +?, = A int S (SM) Γ d Γ d, A mix S = C b A b sl, A b sl = C d a d sl + C sa s sl, a q sl = Γ q m q tan(φ 12 q ), The measurements as a function of impact parameter constrain a d sl, a s sl and Γ d (and?). 11

13 6. Questions (instead of Conclusions!) Γ d /Γ d (SM) is estimated to be ( )%. Is it possible that Γ d /Γ d 1% or 2% due to low energy, non-perturbative contributions? Is it possible that we are still missing other significant standard model contributions to A CP? Are we seeing hints of new physics? Confirmation by other experiments are necessary. 12

14 Measurement of the direct CP asymmetry in B J/ψK and B J/ψπ decays. 13

15 Data: 10.4fb 1 of p p collisions at s = 1.96 TeV. Decay: p p b bx B + X J/ψK + X; J/ψ µ + µ. B + J/ψK + has tree and penguin diagrams with the same weak phase. Hence A J/ψK < 0.3% in the standard model. Good to search for new physics CP violation. The hadron is assigned the kaon mass. Signal selection: Cut based + multivariate (likelihood ratio method). 14

16 Unbinned maximum likelihood fit with L = (1 q h A J/ψK raw )G K (m)+ (1 q h A J/ψπ raw )G π (m) + (1 q h A T )T(m) + (1 q h A E )E(m). G K (m): double gaussians with widths and normalizations free, and widths linearly dependent on kaon energy. G π (m) is an image of G K (m) shifted by m π m K. T(m): threshold function for partially reconstructed B X J/ψh + X. E(m): exponential function for combinatorial background. A J/ψK raw = [ (stat) (syst)]%, A J/ψπ raw = [ (stat) 1.82 (syst)]%. 15

17 2 )/12 MeV/c N(J/ψ h D fb Total B J/ψ K B J/ψ π B X J/ψ h X Combinatorial M (J/ψ h ) [GeV/c 2 ] Projection of fit onto the sum distribution. χ 2 /DOF = 76/47. 16

18 2 )/12 MeV/c + ) - N(J/ψ h D fb Total B B J/ψ K J/ψ π - N(J/ψ h B X M (J/ψ h J/ψ h X Combinatorial ) [GeV/c 2 ] Projection of fit onto the difference distribution. χ 2 /DOF = 59/61. 17

19 (%) a K D0 Run II, 10.4 fb < η(k) < < η(k) < 1.2 η(k) < p(k) (GeV/c) Kaon correction, A K = [ (stat)], is measured with data reconstructing K 0 K + π decays (with same track requirements). 18

20 Conclusions Final results: A J/ψK = [ (stat) 0.08 (syst)]%, A J/ψπ = [ (stat) 1.8 (syst)]%. There is agreement with the standard model arxiv: ; Submitted to Phys. Rev. Lett. 19

21 World Average = ( )% Uncertainty scaled by 1.8 Confidence Level χ 2 D Belle Belle 2008 BaBar Cleo J/ψK A (%) 6.8 World average of A J/ψK using the PDG procedure. 20

22 World Average = ( )% χ 2 D LHCb BaBar Belle J/ψπ A (%) World average of A J/ψπ using the PDG procedure. 21