We report results of a search for nuclear recoils induced by weakly interacting massive particle (WIMP) dark matter using the LUX-ZEPLIN (LZ) two-phase xenon time projection chamber. This analysis uses a total exposure of $4.2\pm0.1$ tonne-years from 280 live days of LZ operation, of which $3.3\pm0.1$ tonne-years and 220 live days are new. A technique to actively tag background electronic recoils from $^{214}$Pb $β$ decays is featured for the first time. Enhanced electron-ion recombination is observed in two-neutrino double electron capture decays of $^{124}$Xe, representing a noteworthy new background. After removal of artificial signal-like events injected into the data set to mitigate analyzer bias, we find no evidence for an excess over expected backgrounds. World-leading constraints are placed on spin-independent (SI) and spin-dependent WIMP-nucleon cross sections for masses $\geq$9 GeV/$c^2$. The strongest SI exclusion set is $2.2\times10^{-48}$ cm$^{2}$ at the 90% confidence level and the best SI median sensitivity achieved is $5.1\times10^{-48}$ cm$^{2}$, both for a mass of 40 GeV/$c^2$.
90% CL WIMP SI cross sections, including sensitivities
90% CL WIMP SI cross sections, including sensitivities
90% CL WIMP SDn cross sections, including sensitivities and nuclear structure uncertainties
We present searches for light dark matter (DM) with masses 3-9 GeV/$c^2$ in the presence of coherent elastic neutrino-nucleus scattering (CE$ν$NS) from $^{8}$B solar neutrinos with the LUX-ZEPLIN experiment. This analysis uses a 5.7 tonne-year exposure with data collected between March 2023 and April 2025. In an energy range spanning 1-6 keV, we report no significant excess of events attributable to dark matter nuclear recoils, but we observe a significant signal from $^{8}$B CE$ν$NS interactions that is consistent with expectation. We set world-leading limits on spin-independent and spin-dependent-neutron DM-nucleon interactions for masses down to 5 GeV/$c^2$. In the no-dark-matter scenario, we observe a signal consistent with $^{8}$B CE$ν$NS events, corresponding to a $4.5σ$ statistical significance. This is the most significant evidence of $^{8}$B CE$ν$NS interactions and is enabled by robust background modeling and mitigation techniques. This demonstrates LZ's ability to detect rare signals at keV-scale energies.
90% CL WIMP SI cross sections, including sensitivities
90% CL WIMP SDn cross sections, including sensitivities and nuclear structure uncertainties
90% CL WIMP SDp cross sections, including sensitivities and nuclear structure uncertainties
A search for exotic Higgs boson decays H $\to$$\mathcal{AA}$, with $\mathcal{A}$$\to$$γγ$ is presented, using events with a semi-merged topology. One of the hypothetical particles, $\mathcal{A}$, is assumed to decay promptly into a semi-merged diphoton system reconstructed as a single photon-like object, while the other $\mathcal{A}$ decays into two resolved photons. The search is performed using proton-proton collision data collected by the CMS experiment at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. The data agree with the standard model background expectation. Upper limits are set on the product of the Higgs boson production cross section and the branching fraction, $σ$(pp $\to$ H)$\mathcal{B}$(H $\to$$\mathcal{AA}$$\to$ 4$γ$), which range from 0.264 to 0.005 pb at 95% confidence level, for $\mathcal{A}$ masses in the range 1 $\lt$ $m_\mathcal{A}$ $\lt$ 15 GeV. These limits are the most stringent to date in the 1$-$5 GeV $m_\mathcal{A}$ range.
The 2D $m_A$ spectra in the final signal region. The unrolled 2D $m_A$ distribution made by scanning along bins of increasing $m_{A2}$ at fixed $m_{A1}$ before incrementing in $m_{A1}$. Only the bins in the $m_{A}$-SR region are included, with the x-axis corresponding to the unrolled bin index of the selected bins, listed sequentially. The data distributions (black points) are plotted against the total predicted background distributions (blue curves) after fitting to the data. The statistical plus systematic uncertainties in the background distribution are plotted as the blue band. The corresponding distributions of simulated $\mathrm{H} \to \mathcal{A} \mathcal{A} \to 4 \gamma$ events for $m_A = $3 (purple curve), 10 (gray curve), and 15 GeV (orange curve) are also overlaid on top. They are each normalized to the value of the expected upper limit to the signal cross section times 50. The lower panels of each plot show the ratio of the observed data over the predicted background as the black points, with the error bars representing the statistical uncertainties in the former. The ratio of the statistical plus systematic uncertainties in the background over the background prediction is shown as the blue band.
1D projections on the $m_{A1}$ axis of the 2D $m_A$ distribution in the final signal region. The data distributions (black points) are plotted against the total predicted background distributions (blue curves) after fitting to the data. The statistical plus systematic uncertainties in the background distribution are plotted as the blue band. The corresponding distributions of simulated $\mathrm{H} \to \mathcal{A} \mathcal{A} \to 4 \gamma$ events for $m_A = $3 (purple curve), 10 (gray curve), and 15 GeV (orange curve) are also overlaid on top. They are each normalized to the value of the expected upper limit to the signal cross section times 50. The lower panels of each plot show the ratio of the observed data over the predicted background as the black points, with the error bars representing the statistical uncertainties in the former. The ratio of the statistical plus systematic uncertainties in the background over the background prediction is shown as the blue band.
1D projections on the $m_{A2}$ axis of the 2D $m_A$ distribution in the final signal region. The data distributions (black points) are plotted against the total predicted background distributions (blue curves) after fitting to the data. The statistical plus systematic uncertainties in the background distribution are plotted as the blue band. The corresponding distributions of simulated $\mathrm{H} \to \mathcal{A} \mathcal{A} \to 4 \gamma$ events for $m_A = $3 (purple curve), 10 (gray curve), and 15 GeV (orange curve) are also overlaid on top. They are each normalized to the value of the expected upper limit to the signal cross section times 50. The lower panels of each plot show the ratio of the observed data over the predicted background as the black points, with the error bars representing the statistical uncertainties in the former. The ratio of the statistical plus systematic uncertainties in the background over the background prediction is shown as the blue band.
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