Search for narrow high-mass resonances in radiative decays of the Z0

Abstract

We search for new resonances, Y, with mass, My, in the range from 30 to 89 GeV, produced via the reaction e+e-,Z°-,),Y, where Y subsequently decays into e + e-, IX +Ix-or hadrons. We use 5.5. pb-1 of data collected in the energy range 88.2 ~ x/~ ~< 94.2 GeV, near the Z ° peak. We obtain the following upper limits, at the 95% confidence level, on the product of the branching ratios: BR(Z°-,~/Y)XBR(Y-.e+e-)<2.8×10-4 for 30<Mv<89, BR(Z°~)'Y)XBR(Y-,Ix+~-)<2.3×10-4 for 30<My<89, BR(Z°~yY) ×BR(Y-,hadrons)<4.7× 10-4 for 30<My< 86. These limits are valid for resonances with widths smaller than our mass resolution.

New axion searches at flavor factories

“…The constants c i are anomaly coefficients which depend on the number of degrees of freedom chiral under the U (1) symmetry and carrying a non-zero charge under the SM gauge group. 2 1 As an example the LEP limit on BR(Z → γa) is 1.7 · 10 −5 from 36.9 pb −1 of data if a is a diphoton resonance [36] and 4.7 · 10 −4 from 5.5 pb −1 of data if a is a dijet resonance [37]. 2 If the SM fermions and the Higgs doublet are uncharged under the U (1) symmetry, the couplings of the pNGB to them arise only from loops of SM gauge bosons and can safely be neglected.…”

Dark forces coupled to nonconserved currents

“…If X escapes the detector or decays invisibly, then LEP searches [30,31] for single photons at half the Z energy constrain this branching ratio to be < ∼ 10 −6 . For visible decays, there are published branching ratio limits for X → jet + jet and X → l + l − of < ∼ 3×10 −3 [32] and 5 × 10 −4 [33] respectively, with some improvement in the high mass region [34]. While these limits (from LEP) are not particularly stringent, we expect that the LHC has the capacity to significantly improve them.…”

“…However, this weak-isospin breaking in the EFT means that π ± → e ± νX decays, as discussed in section III D, are energy-enhanced. In the model of [9], in which X has dimension-4 couplings to electrons, but not to pions or neutrinos, the induced [50,53,54], B → KX (blue) [45][46][47][48][49], Z → Xγ (red) [30][31][32][33][34], very displaced decays at the CHARM proton beam dump experiment [58], and monojets [98]. The enhanced K → πX decays result in larger X production than computed in naive analyses [59,60].…”

New Constraints on Light Vectors Coupled to Anomalous Currents

“…If X decays invisibly, then LEP searches for single photons at half the Z energy [32,33] limit this branching ratio to be < ∼ 10 −6 . The bounds for SM decays of X are less stringent [34][35][36], though the large number of Z bosons produced at hadron colliders should allow enhanced sensitivity to rare Z decays, as we discuss later.…”