Search for ZZ and Zγ* production in pp̄ collisions at s=1.96TeV and limits on anomalous ZZZ and ZZγ* couplings
Physical Review Letters 100:13 (2008)
Abstract:
We present a study of μμμμ, eeee, and μμee events using 1fb-1 of data collected with the D0 detector at the Fermilab Tevatron pp̄ Collider at s=1.96TeV. Requiring the lepton pair masses to be greater than 30 GeV, we observe one event, consistent with the expected background of 0.13±0.03 events and with the predicted standard model ZZ and Zγ* production of 1.71±0.15 events. We set an upper limit on the ZZ and Zγ* cross section of 4.4 pb at the 95% C.L. We also derive limits on anomalous neutral trilinear ZZZ and ZZγ* gauge couplings. The one-parameter 95% C.L. coupling limits with a form-factor scale Λ=1.2TeV are -0.28Measurement of the shape of the boson-transverse momentum distribution in pp --> Z/gamma* --> e+e- + X events produced at square root s = 1.96 TeV.
Phys Rev Lett 100:10 (2008) 102002
Abstract:
We present a measurement of the shape of the Z/gamma* boson transverse momentum (q(T)) distribution in pp --> Z/gamma* --> e(+)e(-) + X events at a center-of-mass energy of 1.96 TeV using 0.98 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron collider. The data are found to be consistent with the resummation prediction at low q(T), but above the perturbative QCD calculation in the region of q(T)>30 GeV/c. Using events with q(T)<30 GeV/c, we extract the value of g(2), one of the nonperturbative parameters for the resummation calculation. Data at large boson rapidity y are compared with the prediction of resummation and with alternative models that employ a resummed form factor with modifications in the small Bjorken x region of the proton wave function.Search for flavor-changing-neutral-current D meson decays
Physical Review Letters 100:10 (2008)
Abstract:
We study the flavor-changing-neutral-current process c→uμ+μ- using 1.3fb-1 of pp̄ collisions at s=1.96TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We see clear indications of the charged-current mediated Ds+ and D+→ π+→μ+μ-π+ final states with significance greater than 4 standard deviations above background for the D+ state. We search for the continuum neutral-current decay of D+→π+μ+μ- in the dimuon invariant mass spectrum away from the resonance. We see no evidence of signal above background and set a limit of B(D+→π+μ+μ-)<3.9×10-6 at the 90% C.L. This limit places the most stringent constraint on new phenomena in the c→uμ+μ- transition. © 2008 The American Physical Society.Search for flavor-changing-neutral-current d meson decays.
Phys Rev Lett 100:10 (2008) 101801
Abstract:
We study the flavor-changing-neutral-current process c-->u micro(+) micro(-) using 1.3 fb(-1) of pp[over ] collisions at square root s = 1.96 TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We see clear indications of the charged-current mediated D(s)(+) and D(+)-->phipi(+) --> micro(+)micro(-)pi(+) final states with significance greater than 4 standard deviations above background for the D(+) state. We search for the continuum neutral-current decay of D(+)-->pi(+) micro(+) micro(-) in the dimuon invariant mass spectrum away from the phi resonance. We see no evidence of signal above background and set a limit of B(D(+) --> pi(+) micro(+) micro(-))<3.9 x 10(-6) at the 90% C.L. This limit places the most stringent constraint on new phenomena in the c--> u micro(+) micro(-) transition.Measurement of the shape of the boson-transverse momentum distribution in pp̄→Z/γ*→e+e-+X events produced at s=1.96TeV
Physical Review Letters 100:10 (2008)