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Rare Charm Processes and Supersymmetry. Kwong Lau University of Houston PRC-US Workshop Beijing, June 11-18, 2006. Outline of talk. Why are rare charm processes important in searching for new physics outside the Standard Model? Why rare charm processes are sensitive to supersymmetry?
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Rare Charm Processes and Supersymmetry Kwong Lau University of Houston PRC-US Workshop Beijing, June 11-18, 2006
Outline of talk • Why are rare charm processes important in searching for new physics outside the Standard Model? • Why rare charm processes are sensitive to supersymmetry? • Two benchmark charm rare processes: FCNC decay D0 -> m+m- and D0 mixing • Prospects at BES III • Summary
General Comments • Rare charm processes proceed in the Standard Model via box diagrams in the short distance limit • The GIM mechanism suppresses FCNC in the Standard model • The GIM mechanism is broken by non-degenerate quark masses • The FCNC box amplitude in the charm sector is undetectably small because of the smallness and/or degeneracy of the quark masses in the down-type quarks (d, s, and b) • Supersymmetric quarks (squarks) and wino can contribute to the box amplitude, and dominate if the squarks masses are not degenerate • Squark masses are a priori not degenerate unless there is additional symmetry • Fractional squark mass differences at O(10-3-10-4) will enhance the box amplitudes to a detectable level. • For example, the CCNC decay D mm branching ratio can be enhanced to 10-10 level • The purpose of this talk is to explore the relationship between the two main CCNC processes (rare decay and mixing) in the context of a generic supersymmetric model
The effective CCNC amplitude m c m Reference: Inami and Lim, NPB 207, 533 (1982).
CCNC predictions The two rare processes share common parameters through the C and E functions. One can do a parametric study by evaluating both process numerically as a function of model parameters (assumed free).
D -> mm decay rate in supersymmetric models Supersymmetric particles with natural mass differences (O(10-3)) can boost the rare D -> mm decay rate by 6-7 orders of magnitude
D0 mixing rate in supersymmetric models Supersymmetric particles with natural mass differences (O(10-3)) can boost the D mixing rate by 6-7 orders of magnitude
FCNC decay searches in E771 High rate hadroproduction of D0’s at hadron colliders and precision vertex measurement of D0 decays are both necessary, a challenging task.
Prospects at BESIII • BESIII expects to produce a few x 107 D0’s per year • It is unlikely that BESIII can improve the D0->mm limit • BESIII can reconstruct a large sample of low-multiplicity D0 decays, e.g., D0 -> Kp decays to search for mixing • The fact that D0’s are produced at threshold at BESIII is a challenge
D0 mixing vs D -> mm decay rate in supersymmetric models The next generation charm experiment at BES III can search D0 CCNC decay rates of order 10-10, probing squark mass up to TeV scale
