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Introduction to High Energy Physics Final Project - Fall 2007

Introduction to High Energy Physics Final Project - Fall 2007. Introduction to Direct CP Violation in ultra-rare Kaon decays Grelli Alessandro Purdue University. Purdue University – West Lafayette IN 12/03/2007. Summary. Summary:. Introduction to C, P and CP. 2) CP violation:

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Introduction to High Energy Physics Final Project - Fall 2007

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  1. Introduction to High Energy Physics Final Project - Fall 2007 Introduction to Direct CP Violation in ultra-rare Kaon decays Grelli Alessandro Purdue University Purdue University – West Lafayette IN 12/03/2007 Alessandro Grelli

  2. Summary Summary: • Introduction to C, P and CP. 2) CP violation: - Kaon system. - Violation in the mixing and direct • Ultra-rare kaon decays. 4) K+L→π+νν. 5) K0L→π0νν - experiments: KTeV and KOPIO 6) Conclusion Alessandro Grelli

  3. P e C symmetries P and C symmetries: P: Physical laws are invariant under coordinates inversion. Lee e Yung [2] (1956) Hypotesis of C violation in weak interaction Wu et al.[3] (1957) Experimental proof. C: Physical invariance over C simmetry: it’s only matter of convention the definition of particle and anti-particle. C violation: Neutrino elicity. If you apply C to neutrino you will have the anti-neutrino with wrong elicity In 1957 first proposal of CP conservation (Landau). In 1964 Christenson, Cronin, Fitch e Turlay[4]prove that CP is not true simmetry of nature using the decay K0→+- (CP Violation). Alessandro Grelli

  4. CP Violation. K0 system as example 1/2 • Il K0 ~ (sd) e K0 ~ (ds) are eigenstates produced by strong interaction with strangeness S = +1 ed S = -1. • The Weak interaction doesn’t preserve S so : As CP eighenstates : CP(K1)=+1 and CP(K2) =-1. if CP is a true simmetryK1 can only decay in states with CP = +1 and K2 only in CP = -1 states. Alessandro Grelli

  5. CP Violation. K0 system as example 2/2 According to Gell-Mann and Pais[1] prevision the mean lifetime of this states is really different: Perfect sistem to study CP violation. We can produce beams of pure K2 and check if happens CP =+1 state decays. (CP violation found in 1964) Indirect violation Experimentally the “indirect” CP violation effect is : Alessandro Grelli

  6. Direct CP vilation • In the 70s was born the hypotesis that CP violation can be explained in SM with the CKM matrix (Cabibbo-Kobajashy -Maskawa). • This hypotesis introduce the possibility of a DIRECT CP violation (i.e a violation the decay amplitude). Usually this kind of Violation is considered with a parameter ε’. A value of ε’/ε different from 0 should be a demostration of Direct CP Violation. Na48 @ CERN results: Re(ε’/ε) =(15.3±2.6)x10-4 KTev @ Fermilab results: Re(ε’/ε) =(20.7±2.8)x10-4 Really little effect but ≠ 0 Alessandro Grelli

  7. Ultra-rare kaon decays K+L→π+νν (BR~10-10) and K0L→ π0νν(BR~10-11) are FCNC processes (Flavor Changing Neutral Current) forbidden at tree level in SM and so they can happen only at second order (1 loop in Feynman dyagram see next slide). K0L→ π0ννdominated by Direct CP Violation ( indirect violation suppressed by a factor ε2 = 106 ). Direct evidence of K+L→π+νν: From BNL experiments: 3 events Proposal for experiment at CERN. No direct evidence for K0L→π0νν:Upper limit from KTev (Fermilab) Several experiments and proposals in the world . Alessandro Grelli

  8. K+L→π+νν, K0L→π0νν: Feynman dyagramns Z-Penguin and W box Dyagramns: s→dνν Alessandro Grelli

  9. K+L→π+νν, K0L→π0νν Hadronic element can be obtained from Kl3 decays. Very low theoretical uncertains. For K0l→π0vv theoretical errors smaller than the charge twin (the loop over c quark in the matrix element is neglegible ~0.1%, only errors from Top physics) and effect of indirect violation less than 1%. Open a window on DIRECT CP violation!!!! Theoretical errors 2-3% BR(K0l→π0vv) is related directly to the parameter that take into account The CP violation in Standard Model. Alessandro Grelli

  10. Experimental challenges • B.R. from Standard Model:( 2.8 ± 1.7 ) x 10-11 • Experimental Signature: Only 2 photons. Without particular technique we don’t know decay vertex and K energy. 3. Background: From K decays. • 34% of KL decays has 1 or more p0 . • K0Lπ0 π0( B.R. = 9.3 x 10-4) • K0Lπ+π - π0( B.R. = 1.25 x 10-1) • Miss identification. • K0Le+π–( B.R. = 3.9 x 10-1) • K0Le+π– ( B.R. = 3.6 x 10-3) Neutrons in the beam halo . Hyperons decays (Лπ0 n). Alessandro Grelli

  11. KTev Fermilab (USA) Odoscopio: Drift Chambers + Magnet. Electromagnetic Calorimeter (CsI). Veto (high prestations). Upper limit < 5.9 x 10-7. 800 Gev protons, KL average momentum ~ 70Gev/c . Revelation channel KL0νν →e+e-γ (Dalitz decay). Alessandro Grelli

  12. KOPIO Proposal BNL (USA) Proposal for KOPIO experiment at BNL (Long Island NY). Similar experiments at KeK and J-Park in Japan. Background Rejection factor from veto ~ 109additional rejection from kinematical constrints 102!!. Example: 0 0 odd 0 0 even Alessandro Grelli

  13. Conclusions A precise measure of ultra-rare kaon decays BR can permit a determination of the value of direct CP violation with an error similar (order of magnitude) to the error that we have from B meson sistem. This is crucial to have a model indipendent determination of direct CP violation and consequently is a test of CP Standard Model sector. Some non Standard Models have different predictions for the branching ration of k0l . Due to the very low BR (~10-9, 10-11) the experimental detection is very challenging and is at the limits of the actual tecnology. Alessandro Grelli

  14. Bibliography [1] M. Gell-Mann and A. Pais, Phys. Rev. 97, 1387 (1955). [2] T.D. Lee and C.N. Yang, Phys. Rev. 104, 254 (1956). [3] C.S. Wu et al., Phys. Rev. 105, 1413 (1957) [4] J.H. Christenson, J.W. Cronin, V.L. Fitch, and R. Turlay, Phys. Rev. Lett. 13. 138 (1964). [5] Gilmann-Wise, Phys.Rev.D21:3150, 1980. [6] KOPIO Collaboration, KOPIO Conceptual Design Report (2005). [7] Greenlee, Phys.Rev.D42:3724, 1990. [8] Littenberg, Phys.Rev.D39:3322,1989. [9] K.Sakashita, PhD Thesis, Osaka University (2006). [10] G.C. Branco et al., CP Violation, Clarendon Press, Oxford (1999). [11] Kazunori Hanagaki, PhD Thesis, Osaka University. (1998). [12] T.Inagaki et al. KEK proposal, “Measurement of the KL→ 0νν decay”(1996). Alessandro Grelli

  15. ........ Backup slides .... Alessandro Grelli

  16. SM Electroweak sector. (..hint..) CKM Matrix – Standard Model Operatore di corrente debole attraverso cui vengono descritte le transizioni tra quarks di diverso sapore: Weak current operator describing quarks flavor transitions can be Written as in the following: 1 The W boson cupling is obtained with the lagrangian: The Vij matrix in 1 is the CKM matrix: Alessandro Grelli

  17. SM Electroweak sector. (..hint..) ...Sorry for the Italian language Wolfenstein paramerization of CKM matrix. All the CP violation effects are Taken into account in η parameter (the complex phase): This is a Unitary 3x3 matrix: Imposing the unitarity condition you can paint the unitarity triangle. The BR of KOPIO decay can mesure the height of the tringle. Alessandro Grelli

  18. Unitarity triangle Unitarity Triangle Alessandro Grelli

  19. Past, Present and Future experiments KOPIO Alessandro Grelli

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