Null tests from angular distributions in D →P_{1}P_{2}l^{+}l^{}, l =e , μ decays on and off peak
Abstract
We systematically analyze the full angular distribution in D →P_{1}P_{2}l^{+}l^{} decays, where P_{1 ,2}=π , K , l =e , μ . We identify several null tests of the standard model (SM). Notably, the angular coefficients I_{5 ,6 ,7}, driven by the leptons' axialvector coupling C_{10}^{(')} , vanish by means of a superior GlashowIliopoulosMaiani (GIM) cancellation and are protected by parity invariance below the weak scale. C P odd observables related to the angular coefficients I_{5 ,6 ,8 ,9} allow us to measure C P asymmetries without D tagging. The corresponding observables A_{5 ,6 ,8 ,9} constitute null tests of the SM. Lepton universality in Δ c =Δ u =1 transitions can be tested by comparing D →P_{1}P_{2}μ^{+}μ^{} to D →P_{1}P_{2}e^{+}e^{} decays. Data for P_{1}P_{2}=π^{+}π^{} and K^{+}K^{} on muon modes are available from LHCb and on electron modes from BESIII. Corresponding ratios of dimuon to dielectron branching fractions are at least about an order of magnitude away from probing the SM. In the future electron and muon measurements should be made available for the same cuts as corresponding ratios R_{P}^{1P2 D} provide null tests of e μ universality. We work out beyondSM signals modelindependently and in SM extensions with leptoquarks.
 Publication:

Physical Review D
 Pub Date:
 August 2018
 DOI:
 10.1103/PhysRevD.98.035041
 arXiv:
 arXiv:1805.08516
 Bibcode:
 2018PhRvD..98c5041D
 Keywords:

 High Energy Physics  Phenomenology;
 High Energy Physics  Experiment
 EPrint:
 18 pages plus references and appendix, 7 figures