Abstract

A search for the D0→π+π−μ+μ− decay, where the muon pair does not originate from a resonance, is performed using proton–proton collision data corresponding to an integrated luminosity of 1.0fb−1 recorded by the LHCb experiment at a centre-of-mass energy of 7 TeV. No signal is observed and an upper limit on the relative branching fraction with respect to the resonant decay mode D0→π+π−ϕ(→μ+μ−), under the assumption of a phase-space model, is found to beB(D0→π+π−μ+μ−)/B(D0→π+π−ϕ(→μ+μ−))<0.96 at 90% confidence level. The upper limit on the absolute branching fraction is evaluated to be B(D0→π+π−μ+μ−)<5.5×10−7 at 90% confidence level. This is the most stringent to date.

Highlights

  • The upper limit on the absolute branching fraction is evaluated to be Flavour-changing neutral current (FCNC) processes are rare within the Standard Model (SM) as they cannot occur at tree level and are suppressed by the Glashow–Iliopoulos–Maiani (GIM)

  • This suppression allows for subleading processes with potential for physics beyond the SM, such as FCNC decays of D mesons, and the coupling of up-type quarks in electroweak processes illustrated in Fig. 1, to be probed more precisely

  • A search for the D0 → π +π −μ+μ− decay is conducted usionfg1.p0pfbc−o1llisaiton√sd=ata7, corresponding to an TeV recorded by the integrated luminosity LHCb experiment

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Summary

Introduction

Flavour-changing neutral current (FCNC) processes are rare within the Standard Model (SM) as they cannot occur at tree level and are suppressed by the Glashow–Iliopoulos–Maiani (GIM). In contrast to the B meson system, where the high mass of the top quark in the loop weakens the suppression, the GIM cancellation is almost exact [1] in D meson decays, leading to expected branching fractions for c → uμ+μ− processes in the range (1 − 3) × 10−9 [2,3,4]. This suppression allows for subleading processes with potential for physics beyond the SM, such as FCNC decays of D mesons, and the coupling of up-type quarks in electroweak processes illustrated, to be probed more precisely. D0 → π +π −φ(→ μ+μ−) decays, isolated in an appropriate dimuon range centred around the φ pole

The LHCb detector and trigger
Candidate selection
Mass fit
Branching fraction determination
Systematic uncertainties
Results
Conclusions
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