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Measurement of CP violation with the LHC b experiment at CERN

Measurement of CP violation with the LHC b experiment at CERN. Annabelle Chuinard McGill University WIPC 2013. WIPC 2013. The LHC experiment. b. b. Physics goals. Key facts. 760 people, 14 countries 4500 t. apparatu s , 100 m underground single arm forward (≠ ATLAS).

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Measurement of CP violation with the LHC b experiment at CERN

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  1. Measurement of CP violation with the LHCb experiment at CERN Annabelle Chuinard McGill University WIPC 2013 WIPC 2013

  2. The LHC experiment b b Physics goals Key facts • 760 people, 14 countries • 4500 t. apparatus, 100 m underground • single arm forward (≠ ATLAS) • b-physics: study of particlescontaining a (anti-)beauty quark! • Branching fraction of B mesondecay  Feynman diagram • CP asymmetry  CKM matrixterms • Physics beyond the SM WIPC 2013

  3. The LHCb detector Magnets Electronic CALorimeter Hadronic CALorimeter Trackers Muons detector (MWPC) -271.3°C RICH 2 -5 to 5°C RICH 1 VErtex LOcator Proton beam -25°C pp collision WIPC 2013

  4. My job: measure CP asymmetry for Tree Radiative B decay : A1 Amplitudes Penguin (loop) A2 There are 2 main Feynman contributions to thisdecay. WIPC 2013

  5. CKM terms and couplings Cabbibo-Kobayashi-Maskawa CKM) matrixdescribesquark mixingin weak interactions. WIPC 2013

  6. Asymmetry Conjugateprocess (CP) WIPC 2013

  7. Charge asymmetry Asymmetry due to production rate of B+ et B- Detection asymmetry between K+ et K- (found compatible with0) Measured value fromexperimental rates Corrections

  8. How to determineraw asymmetry? Distribution of the invariant mass η’K+ Blue line:Multiparameter fit to maximize theextendedlikelihoodfunction Distribution of the invariant mass η’K-

  9. Detection asymmetry Detection efficiencyis a function of thecross-section of withmatter. Athighenergy, K+ and K- indistinguishable = same cross section Test sample: (no production asymmetry) Mapρand use MINUIT tool to minimize χ2 Use this as a boundary condition to fitρ as of function of pK+.

  10. Detection asymmetry computation Integrate over the distribution to have number of events Distribution of the number of events as a function of Distribution of as a function of the momentum Distribution of the number of events as a function of

  11. SUMMARY Calculatedusing rates from mass distributions Calculatedusing new methodbased on kaons cross-sections Compatible with PDG world average : Improvements: Increaseluminosity = more statistics

  12. Appendix1: 2D Likelihood fit Unbinnedlimit (either 0 or 1event per bin) Poisson’sdistr. mB and mη’ are uncorrelated

  13. Appendix 2: Detectionasymmetry – Mappingprocess

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