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Measurement of CP asymmetry in D 0K K + and D 0π π + decays

A preprint version of the article is available at arXiv.


Time-integrated CP asymmetries in D 0 decays to the final states K K + and π π + are measured using proton-proton collisions corresponding to 3fb−1 of integrated luminosity collected at centre-of-mass energies of 7 TeV and 8 TeV. The D 0 mesons are produced in semileptonic b-hadron decays, where the charge of the accompanying muon is used to determine the initial flavour of the charm meson. The difference in CP asymmetries between the two final states is measured to be

$$ \varDelta {A}_{\mathrm{CP}}={A}_{\mathrm{CP}}\left({K}^{-}{K}^{+}\right)-{A}_{\mathrm{CP}}\left({\pi}^{-}{\pi}^{+}\right)=\left(+0.14 \pm 0.16\ \left(\mathrm{stat}\right)\pm 0.08\left(\mathrm{syst}\right)\right)\%. $$

A measurement of A CP (K K +) is obtained assuming negligible CP violation in charm mixing and in Cabibbo-favoured D decays. It is found to be

$$ {A}_{\mathrm{CP}}\left({K}^{-}{K}^{+}\right)=\left(-0.06\pm 0.15\left(\mathrm{stat}\right)\pm 0.10\left(\mathrm{syst}\right)\right)\%, $$

where the correlation coefficient between ΔA CP and A CP (K K +) is ρ = 0.28. By combining these results, the CP asymmetry in the D 0π π + channel is A CP (π π +) = (−0.20 ± 0.19 (stat) ± 0.10 (syst))%.


  1. [1]

    M. Bobrowski, A. Lenz, J. Riedl and J. Rohrwild, How large can the SM contribution to CP-violation in \( {D}^0-{\overline{D}}^0 \) mixing be?, JHEP 03 (2010) 009 [arXiv:1002.4794] [INSPIRE].

    ADS  Article  Google Scholar 

  2. [2]

    Y. Grossman, A.L. Kagan and Y. Nir, New physics and CP-violation in singly Cabibbo suppressed D decays, Phys. Rev. D 75 (2007) 036008 [hep-ph/0609178] [INSPIRE].

    ADS  Google Scholar 

  3. [3]

    T. Feldmann, S. Nandi and A. Soni, Repercussions of flavour symmetry breaking on CP-violation in D-meson decays, JHEP 06 (2012) 007 [arXiv:1202.3795] [INSPIRE].

    ADS  Article  Google Scholar 

  4. [4]

    J. Brod, A.L. Kagan and J. Zupan, Size of direct CP-violation in singly Cabibbo-suppressed D decays, Phys. Rev. D 86 (2012) 014023 [arXiv:1111.5000] [INSPIRE].

    ADS  Google Scholar 

  5. [5]

    B. Bhattacharya, M. Gronau and J.L. Rosner, CP asymmetries in singly-Cabibbo-suppressed D decays to two pseudoscalar mesons, Phys. Rev. D 85 (2012) 054014 [arXiv:1201.2351] [INSPIRE].

    ADS  Google Scholar 

  6. [6]

    LHCb collaboration, Implications of LHCb measurements and future prospects, Eur. Phys. J. C 73 (2013) 2373 [arXiv:1208.3355] [INSPIRE].

    Google Scholar 

  7. [7]

    S. Bianco, F.L. Fabbri, D. Benson and I. Bigi, A Cicerone for the physics of charm, Riv. Nuovo Cim. 26N7 (2003) 1 [hep-ex/0309021] [INSPIRE].

    Google Scholar 

  8. [8]

    Heavy Flavor Averaging Group collaboration, Y. Amhis et al., Averages of B-hadron, C-hadron and τ -lepton properties as of early 2012, arXiv:1207.1158 [INSPIRE].

  9. [9]

    LHCb collaboration, Evidence for CP-violation in time-integrated D 0h h + decay rates, Phys. Rev. Lett. 108 (2012) 111602 [arXiv:1112.0938] [INSPIRE].

    Article  Google Scholar 

  10. [10]

    LHCb Collaboration, A search for time-integrated CP-violation in D 0K K + and D 0π π + decays, LHCb-CONF-2013-003 (2013).

  11. [11]

    LHCb collaboration, Search for direct CP violation in D 0h h + modes using semileptonic B decays, Phys. Lett. B 723 (2013) 33 [arXiv:1303.2614] [INSPIRE].

    Google Scholar 

  12. [12]

    BaBar collaboration, B. Aubert et al., Search for CP-violation in the decays D 0K K + and D 0π π +, Phys. Rev. Lett. 100 (2008) 061803 [arXiv:0709.2715] [INSPIRE].

    ADS  Article  Google Scholar 

  13. [13]

    CDF collaboration, T. Aaltonen et al., Measurement of CP-violating asymmetries in D 0π + π and D 0K + K decays at CDF, Phys. Rev. D 85 (2012) 012009 [arXiv:1111.5023] [INSPIRE].

    ADS  Google Scholar 

  14. [14]

    CDF collaboration, T. Aaltonen et al., Measurement of the difference of CP-violating asymmetries in D 0K + K and D 0π + π decays at CDF, Phys. Rev. Lett. 109 (2012) 111801 [arXiv:1207.2158] [INSPIRE].

    ADS  Article  Google Scholar 

  15. [15]

    Belle collaboration, M. Staric et al., Measurement of CP asymmetry in Cabibbo suppressed D 0 decays, Phys. Lett. B 670 (2008) 190 [arXiv:0807.0148] [INSPIRE].

    ADS  Article  Google Scholar 

  16. [16]

    Belle collaboration, B.R. Ko, Direct CP-violation in charm at Belle, PoS(ICHEP2012)353 [arXiv:1212.1975] [INSPIRE].

  17. [17]

    LHCb collaboration, The LHCb detector at the LHC, 2008 JINST 3 S08005 [INSPIRE].

  18. [18]

    M. Adinolfi et al., Performance of the LHCb RICH detector at the LHC, Eur. Phys. J. C 73 (2013) 2431 [arXiv:1211.6759] [INSPIRE].

    ADS  Article  Google Scholar 

  19. [19]

    R. Aaij et al., The LHCb trigger and its performance in 2011, 2013 JINST 8 P04022 [arXiv:1211.3055] [INSPIRE].

  20. [20]

    W.D. Hulsbergen, Decay chain fitting with a Kalman filter, Nucl. Instrum. Meth. A 552 (2005) 566 [physics/0503191] [INSPIRE].

    ADS  Article  Google Scholar 

  21. [21]

    Particle Data Group collaboration, J. Beringer et al., Review of particle physics, Phys. Rev. D 86 (2012) 010001 [INSPIRE].

    ADS  Google Scholar 

  22. [22]

    LHCb collaboration, Precision measurement of D meson mass differences, JHEP 06 (2013) 065 [arXiv:1304.6865] [INSPIRE].

    Google Scholar 

  23. [23]

    A. Pais and O. Piccioni, Note on the decay and absorption of the θ 0, Phys. Rev. 100 (1955) 1487 [INSPIRE].

    ADS  Article  Google Scholar 

  24. [24]

    W. Fetscher, P. Kokkas, P. Pavlopoulos, T. Schietinger and T. Ruf, Regeneration of arbitrary coherent neutral kaon states: a new method for measuring the \( {K}^0{\overline{K}}^0 \) forward scattering amplitude, Z. Phys. C 72 (1996) 543 [INSPIRE].

    ADS  Google Scholar 

  25. [25]

    A. Gsponer, J. Hoffnagle, W.R. Molzon, J. Roehrig, V.L. Telegdi et al., Precise coherent K S regeneration amplitudes for C, Al, Cu, SN and Pb nuclei from 20 GeV/c to 140 GeV/c and their interpretation, Phys. Rev. Lett. 42 (1979) 13 [INSPIRE].

    ADS  Article  Google Scholar 

  26. [26]

    R.A. Briere and B. Winstein, Determining the phase of a strong scattering amplitude from its momentum dependence to better than 1-degree: the example of kaon regeneration, Phys. Rev. Lett. 75 (1995) 402 [Erratum ibid. 75 (1995) 2070] [INSPIRE].

  27. [27]

    M.L. Good, Relation between scattering and absorption in the Pais-Piccioni phenomenon, Phys. Rev. 106 (1957) 591 [INSPIRE].

    ADS  Article  Google Scholar 

  28. [28]

    LHCb collaboration, Measurement of the D ± production asymmetry in 7 TeV pp collisions, Phys. Lett. B 718 (2013) 902 [arXiv:1210.4112] [INSPIRE].

    ADS  Google Scholar 

  29. [29]

    LHCb collaboration, Measurement of \( {D}^0-{\overline{D}}^0 \) mixing parameters and search for CP-violation using D 0K + π decays, Phys. Rev. Lett. 111 (2013) 251801 [arXiv:1309.6534] [INSPIRE].

    Article  Google Scholar 

  30. [30]

    M. Pivk and F.R. Le Diberder, SPlot: a statistical tool to unfold data distributions, Nucl. Instrum. Meth. A 555 (2005) 356 [physics/0402083] [INSPIRE].

    ADS  Article  Google Scholar 

  31. [31]

    N. Johnson, Systems of frequency curves generated by methods of translation, Biometrika 36 (1949) 149.

    Article  MATH  MathSciNet  Google Scholar 

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