While dual-phase xenon time projection chambers (TPCs) have driven the sensitivity towards weakly interacting massive particles (WIMPs) at the GeV/c^2 to TeV/c^2 mass scale, the scope for sub-GeV/c^2 dark matter particles is hindered by a limited nuclear recoil energy detection threshold. One approach to probe for lighter candidates is to consider cases where they have been boosted by collisions with cosmic rays in the Milky Way, such that the additional kinetic energy lifts their induced signatures above the nominal threshold. In this Letter, we report first results of a search for cosmic ray-boosted dark matter (CRDM) with a combined 4.2 tonne-year exposure from the LUX-ZEPLIN (LZ) experiment. We observe no excess above the expected backgrounds and establish world-leading constraints on the spin-independent CRDM-nucleon cross section as small as 3.9 * 10^{-33} cm^2 at 90% confidence level for sub-GeV/c^2 masses.
90% CL CRDM-nucleon cross sections
Measurements of $W^+W^-\rightarrow e^\pm νμ^\mp ν$ production cross-sections are presented, providing a test of the predictions of perturbative quantum chromodynamics and the electroweak theory. The measurements are based on data from $pp$ collisions at $\sqrt{s}=13$ TeV recorded by the ATLAS detector at the Large Hadron Collider in 2015-2018, corresponding to an integrated luminosity of 140 fb$^{-1}$. The number of events due to top-quark pair production, the largest background, is reduced by rejecting events containing jets with $b$-hadron decays. An improved methodology for estimating the remaining top-quark background enables a precise measurement of $W^+W^-$ cross-sections with no additional requirements on jets. The fiducial $W^+W^-$ cross-section is determined in a maximum-likelihood fit with an uncertainty of 3.1%. The measurement is extrapolated to the full phase space, resulting in a total $W^+W^-$ cross-section of $127\pm4$ pb. Differential cross-sections are measured as a function of twelve observables that comprehensively describe the kinematics of $W^+W^-$ events. The measurements are compared with state-of-the-art theory calculations and excellent agreement with predictions is observed. A charge asymmetry in the lepton rapidity is observed as a function of the dilepton invariant mass, in agreement with the Standard Model expectation. A CP-odd observable is measured to be consistent with no CP violation. Limits on Standard Model effective field theory Wilson coefficients in the Warsaw basis are obtained from the differential cross-sections.
Measured fiducial cross-section compared with theoretical predictions from MiNNLO+Pythia8, Geneva+Pythia8, Sherpa2.2.12, and MATRIX2.1. The predictions are based on the NNPDF3.0 (red squares) and NNPDF3.1 luxQED (blue dots) PDF sets. The nNNLO predictions include photon-induced contributions (always using NNPDF3.1 luxQED) and NLO QCD corrections to the gluon-gluon initial state. The $q\bar{q}\rightarrow WW$ predictions from MiNNLO, Geneva, and Sherpa2.2.12 are combined with a Sherpa2.2.2 prediction of gluon-induced production, scaled by an inclusive NLO K-factor of 1.7. Inner (outer) error bars on the theory predictions correspond to PDF (the combination of scale and PDF) uncertainties. The MATRIX nNNLO QCD $\otimes$ NLO EW prediction using NNPDF3.1 luxQED, the best available prediction of the integrated fiducial cross-section, is in good agreement with the measurement.
Fiducial differential cross-sections as a function of $p_{\mathrm{T}}^{\mathrm{lead.\,lep.}}$. The measured cross-section values are shown as points with error bars giving the statistical uncertainty and solid bands indicating the size of the total uncertainty. The right-hand-side axis indicates the integrated cross-section of the rightmost bin. The results are compared to fixed-order nNNLO QCD + NLO EW predictions of Matrix 2.1, with the NNLO + PS predictions from Powheg MiNNLO + Pythia8 and Geneva + Pythia8, as well as Sherpa2.2.12 NLO + PS predictions. The last three predictions are combined with Sherpa 2.2.2 for the $gg$ initial state and Sherpa 2.2.12 for electroweak $WWjj$ production. These contributions are modelled at LO but a NLO QCD $k$-factor of 1.7 is applied for gluon induced production. Theoretical predictions are indicated as markers with vertical lines denoting PDF, scale and parton shower uncertainties. Markers are staggered for better visibility.
Correlation matrix of the statistical uncertainties in the measured fiducial cross section for the observable $p_{\mathrm{T}}^{\mathrm{lead.\,lep.}}$.
We measure the spin-density matrix elements (SDMEs) for the photoproduction of $ϕ(1020)$ off of the proton in its decay to $K_S^0K_L^0$, using 105 pb$^{-1}$ of data collected with a linearly polarized photon beam using the GlueX experiment. The SDMEs are measured in nine bins of the squared four-momentum transfer $t$ in the range $-t=0.15-1.0$ GeV$^2$, providing the first measurement of their $t$-dependence for photon beam energies $E_γ= 8.2-8.8$ GeV. We confirm the dominance of Pomeron exchange in this region, and put constraints on the contribution of other Regge exchanges. We also find that helicity amplitudes where the helicity of the photon and the $ϕ(1020)$ differ by two units are negligible.
Spin-density matrix elements of $\phi(1020)$ mesons produced by a linearly polarized photon beam in the helicity system. For each bin of $-t$, the limits of the bin range are given, along with the average $-\bar t$ and root-mean-square deviation $-t_\text{RMS}$ of all events that fall within the bin.
A measurement of the WZ$γ$ triboson production cross section is presented. The analysis is based on a data sample of proton-proton collisions at a center-of-mass energy of $\sqrt{s}$ = 13 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb$^{-1}$. The analysis focuses on the final state with three charged leptons, $\ell^\pmν\ell^+\ell^-$, where $\ell$ = e or $μ$, accompanied by an additional photon. The observed (expected) significance of the WZ$γ$ signal is 5.4 (3.8) standard deviations. The cross section is measured in a fiducial region, where events with an $\ell$ originating from a tau lepton decay are excluded, to be 5.48 $\pm$ 1.11 fb, which is compatible with the prediction of 3.69 $\pm$ 0.24 fb at next-to-leading order in quantum chromodynamics. Exclusion limits are set on anomalous quartic gauge couplings and on the production cross sections of massive axion-like particles.
The distributions of the variables used in the simultaneous fit for the nonprompt $l$ CR. The black points with error bars represent the data and their statistical uncertainties, whereas the shaded band represents the predicted uncertainties. The bottom panel in each figure shows the ratio of the number of events observed in data to that of the total SM prediction. The last bin of each plot has been extended to include the overflow contribution.
The distributions of the variables used in the simultaneous fit for the nonprompt $\gamma$ CR. The black points with error bars represent the data and their statistical uncertainties, whereas the shaded band represents the predicted uncertainties. The bottom panel in each figure shows the ratio of the number of events observed in data to that of the total SM prediction. The last bin of each plot has been extended to include the overflow contribution.
The distributions of the variables used in the simultaneous fit for the ZZ CR. The black points with error bars represent the data and their statistical uncertainties, whereas the shaded band represents the predicted uncertainties. The bottom panel in each figure shows the ratio of the number of events observed in data to that of the total SM prediction. The last bin of each plot has been extended to include the overflow contribution.
We measure for the first time the differential photoproduction cross section $d\sigma/dt$ of the $a_2(1320)$ meson at an average photon beam energy of 8.5~GeV, using data with an integrated luminosity of 104~pb$^{-1}$ collected by the GlueX experiment. We fully reconstruct the $\gamma p \to \eta\pi^0 p$ reaction and perform a partial-wave analysis in the $a_2(1320)$ mass region with amplitudes that incorporate the linear polarization of the beam. This allows us to separate for the first time the contributions of natural- and unnatural-parity exchanges. These measurements provide novel information about the photoproduction mechanism, which is critical for the search for spin-exotic states.
$a_2(1320)$ parity asymmetry, $P_{\sigma}$, in bins of four-momentum transfer. The first uncertainty is statistical, the second systematic.
$a_2(1320)$ differential cross section split into different reflectivity components, $\frac{d\sigma^+}{dt}$ and $\frac{d\sigma^-}{dt}$, in bins of four-momentum transfer. The first uncertainty is statistical, the second systematic.
$a_2(1320)$ differential cross section in the m=-1 projection split into different reflectivity components, $\frac{d\sigma^+_{-1}}{dt}$ and $\frac{d\sigma^-_{-1}}{dt}$, in bins of four-momentum transfer. The first uncertainty is statistical, the second systematic.
A search is conducted for a new scalar boson $S$, with a mass distinct from that of the Higgs boson, decaying into four leptons ($\ell =$$e$, $\mu$) via an intermediate state containing two on-shell, promptly decaying new spin-1 bosons $Z_\text{d}$: $S \rightarrow Z_\text{d}Z_\text{d} \rightarrow 4\ell$, where the $Z_\text{d}$ boson has a mass between 15 and 300 GeV, and the $S$ boson has a mass between either 30 and 115 GeV or 130 and 800 GeV. The search uses proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider with an integrated luminosity of 139 fb$^{-1}$ at a centre-of-mass energy of $\sqrt{s}=13$ TeV. No significant excess above the Standard Model background expectation is observed. Upper limits at 95% confidence level are set on the production cross-section times branching ratio, $\sigma(gg \to S) \times \mathcal{B}(S\rightarrow Z_\text{d}Z_\text{d} \rightarrow 4\ell)$, as a function of the mass of both particles, $m_S$ and $m_{Z\text{d}}$.
Average dilepton mass distribution $\left\langle m_{\ell\ell}\right\rangle = \frac{1}{2}\left(m_{ab} + m_{cd}\right)$ in Signal Region 1.
Average dilepton mass distribution $\left\langle m_{\ell\ell}\right\rangle = \frac{1}{2}\left(m_{ab} + m_{cd}\right)$ in Signal Region 2.
Total invariant mass distribution $m_{4\ell}$ in Signal Region 1.
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
The multiplicities of positive and negative pions, kaons and unidentified hadrons produced in deep-inelastic scattering are measured in bins of the Bjorken scaling variable $x$, the relative virtual-photon energy $y$ and the fraction of the virtual-photon energy transferred to the final-state hadron $z$. Data were obtained by the COMPASS Collaboration using a 160 GeV muon beam of both electric charges and a liquid hydrogen target. These measurements cover the kinematic domain with photon virtuality $Q^2 > 1$ (GeV/$c)^2$, $0.004 < x < 0.4$, $0.1 < y < 0.7$ and $0.2 < z < 0.85$, in accordance with the kinematic domain used in earlier published COMPASS multiplicity measurements with an isoscalar target. The calculation of radiative corrections was improved by using the Monte Carlo generator DJANGOH, which results in up to 12% larger corrections in the low-$x$ region.
h+/h- multiplicities in (x, y, z) bins with corrections, applied corrections for VM and RC are provided in the table
pi+/pi- multiplicities in (x, y, z) bins with corrections, applied corrections for VM and RC are provided in the table
K+/K- multiplicities in (x, y, z) bins with corrections, applied corrections for VM and RC are provided in the table
The spin-exotic hybrid meson $\pi_{1}(1600)$ is predicted to have a large decay rate to the $\omega\pi\pi$ final state. Using 76.6~pb$^{-1}$ of data collected with the GlueX detector, we measure the cross sections for the reactions $\gamma p \to \omega \pi^+ \pi^- p$, $\gamma p \to \omega \pi^0 \pi^0 p$, and $\gamma p\to\omega\pi^-\pi^0\Delta^{++}$ in the range $E_\gamma =$ 8-10 GeV. Using isospin conservation, we set the first upper limits on the photoproduction cross sections of the $\pi^{0}_{1}(1600)$ and $\pi^{-}_{1}(1600)$. We combine these limits with lattice calculations of decay widths and find that photoproduction of $\eta'\pi$ is the most sensitive two-body system to search for the $\pi_1(1600)$.
Measured $\sigma(\gamma p\to\omega\pi^+\pi^-p)$ values for $8<E_\gamma<10$ GeV and $0.1<-t<0.5$ (GeV$^2$). There are normalization uncertainties that are 100% correlated between the three cross section measurements. These include 5% for the luminosity, 13.5% for the tracking efficiency, and 8.1% for the photon efficiency.
Measured $\sigma(\gamma p\to\omega\pi^0\pi^0p)$ values for $8<E_\gamma<10$ GeV and $0.1<-t<0.5$ (GeV$^2$). There are normalization uncertainties that are 100% correlated between the three cross section measurements. These include 5% for the luminosity, 9.1% for the tracking efficiency, and 24.3% for the photon efficiency.
Measured $\sigma(\gamma p\to\omega\pi^-\pi^0\Delta^{++})$ values for $8<E_\gamma<10$ GeV and $0.1<-t<0.5$ (GeV$^2$). There are normalization uncertainties that are 100% correlated between the three cross section measurements. These include 5% for the luminosity, 16% for the tracking efficiency, and 16.3% for the photon efficiency.
We measure the spin-density matrix elements (SDMEs) of the $\Delta^{++}(1232)$ in the photoproduction reaction $\gamma p \to \pi^-\Delta^{++}(1232)$ with the GlueX experiment in Hall D at Jefferson Lab. The measurement uses a linearly--polarized photon beam with energies from $8.2$ to $8.8$~GeV and the statistical precision of the SDMEs exceeds the previous measurement by three orders of magnitude for the momentum transfer squared region below $1.4$ GeV$^2$. The data are sensitive to the previously undetermined relative sign between couplings in existing Regge-exchange models. Linear combinations of the extracted SDMEs allow for a decomposition into natural and unnatural--exchange amplitudes. We find that the unnatural exchange plays an important role in the low momentum transfer region.
Spin-density matrix elements for the photoproduction of $\Delta(1232)^{++}$ in the Gottfried-Jackson system. The first uncertainty is statistical, the second systematic. The systematic uncertainties for the polarized SDMEs $\rho^1_{ij}$ and $\rho^2_{ij}$ contain an overall relative normalization uncertainty of 2.1% which is fully correlated for all values of $-t$.
Spin-density matrix elements for the photoproduction of $\Delta(1232)^{++}$ in the Gottfried-Jackson system. The first uncertainty is statistical, the second systematic.
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