Charm mixing from BABAR.pdfVIP

Chinese Physics C (HEP NP) Vol. 32, No. 6, Jun., 2008 Charm mixing from BABAR * N. Neri1) (for the BABAR Collaboration) (BABAR Collaboration, Universita? di Pisa and INFN, L. Bruno Pontecorvo 3, 56127 Pisa, Italy) Abstract We present recent results from BABAR experiment for D0-D0 mixing measurements. Mixing parameters can be measured in different ways using different D0 decay modes, here we discuss the most sensitive analyses such as D0 → K+π? where we had the first evidence of charm mixing, the measurement of the ratio of lifetimes of the decays D0 →K+K? and D0 → π+π? relative to D0 →K?π+, the time dependent Dalitz plot analysis of D0 →K+π?π0. New limits on CP -violating time-integrated asymmetries in D0 →K+K? and D0 → π+π? are also discussed. The analyses presented are based on 384 fb?1 data collected with the BABAR detector at the PEP-II asymmetric B Factory. Key words charm mixing, flavor oscillations, D0 mesons, BABAR PACS 12.15.Ff, 13.25.Ft, 11.30.Er 1 Introduction D0-D0 oscillations can be explained by the fact that the Hamiltonian which determines the time- evolution of the neutral D meson system is not di- agonal in the flavor defined base. The simplified time evolution is determined by a 2×2 effective hamiltonian matrix H = M ? i 2 Γ by solving the the Schro?dinger equation: i ? ? t ( D0(t) D0(t) ) = ( M ? i 2 Γ )( D0(t) D0(t) ) , (1) where D0 and D0 are the neutral D mesons of op- posite flavor content and M and Γ are the Hermetian matrices which represent the dispersive (mass) and absorbitive (widths) parts of the contribution to the flavor mixing. The eigenstates of the effective Hamil- tonian, |D1,2〉, are therefore a linear combination of |D0〉 and |D0〉: |D1,2〉= p|D 0〉±q |D0〉, with |p|2 + |q |2 = 1 . (2) p, q are related to the eigenvalues of the effective hamiltonian. The time evolution is well defined: |D1,2(t)〉 = e1,2(t)|D1,2〉, (3) e1,2(t) = exp [ ?i(m1,2? iΓ1,2 2 )t ] , (4) where m1,2 and Γ1,2 are the masses and the widths of the hamiltonian eigens