The FASER experiment at the LHC is designed to search for light, weakly-interacting particles produced in proton-proton collisions at the ATLAS interaction point that travel in the far-forward direction. The first results from a search for dark photons decaying to an electron-positron pair, using a dataset corresponding to an integrated luminosity of 27.0 fb$^{-1}$ collected at center-of-mass energy $\sqrt{s} = 13.6$ TeV in 2022 in LHC Run 3, are presented. No events are seen in an almost background-free analysis, yielding world-leading constraints on dark photons with couplings $\epsilon \sim 2 \times 10^{-5} - 1 \times 10^{-4}$ and masses $\sim$ 17 MeV - 70 MeV. The analysis is also used to probe the parameter space of a massive gauge boson from a U(1)$_{B-L}$ model, with couplings $g_{B-L} \sim 5 \times 10^{-6} - 2 \times 10^{-5}$ and masses $\sim$ 15 MeV - 40 MeV excluded for the first time.
We report a measurement of the forward-backward asymmetry, $A_{FB}$, in $b\bar{b}$ pairs produced in proton-antiproton collisions and identified by muons from semileptonic $b$-hadron decays. The event sample was collected at a center-of-mass energy of $\sqrt{s}=1.96$ TeV with the CDF II detector and corresponds to 6.9 fb$^{-1}$ of integrated luminosity. We obtain an integrated asymmetry of $A_{FB}(b\bar{b})=(1.2 \pm 0.7)$\% at the particle level for $b$-quark pairs with invariant mass, $m_{b\bar{b}}$, down to $40$ GeV/$c^2$ and measure the dependence of $A_{FB}(b\bar{b})$ on $m_{b\bar{b}}$. The results are compatible with expectations from the standard model.
At the Fermilab Tevatron proton-antiproton ($p\bar{p}$) collider, Drell-Yan lepton pairs are produced in the process $p \bar{p} \rightarrow e^+e^- + X$ through an intermediate $\gamma^*/Z$ boson. The forward-backward asymmetry in the polar-angle distribution of the $e^-$ as a function of the $e^+e^-$-pair mass is used to obtain $\sin^2\theta^{\rm lept}_{\rm eff}$, the effective leptonic determination of the electroweak-mixing parameter $\sin^2\theta_W$. The measurement sample, recorded by the Collider Detector at Fermilab (CDF), corresponds to 9.4~fb$^{-1}$ of integrated luminosity from $p\bar{p}$ collisions at a center-of-momentum energy of 1.96 TeV, and is the full CDF Run II data set. The value of $\sin^2\theta^{\rm lept}_{\rm eff}$ is found to be $0.23248 \pm 0.00053$. The combination with the previous CDF measurement based on $\mu^+\mu^-$ pairs yields $\sin^2\theta^{\rm lept}_{\rm eff} = 0.23221 \pm 0.00046$. This result, when interpreted within the specified context of the standard model assuming $\sin^2 \theta_W = 1 - M_W^2/M_Z^2$ and that the $W$- and $Z$-boson masses are on-shell, yields $\sin^2\theta_W = 0.22400 \pm 0.00045$, or equivalently a $W$-boson mass of $80.328 \pm 0.024 \;{\rm GeV}/c^2$.
We have performed the most comprehensive resonance-model fit of $\pi^-\pi^-\pi^+$ states using the results of our previously published partial-wave analysis (PWA) of a large data set of diffractive-dissociation events from the reaction $\pi^- + p \to \pi^-\pi^-\pi^+ + p_\text{recoil}$ with a 190 GeV/$c$ pion beam. The PWA results, which were obtained in 100 bins of three-pion mass, $0.5 < m_{3\pi} < 2.5$ GeV/$c^2$, and simultaneously in 11 bins of the reduced four-momentum transfer squared, $0.1 < t' < 1.0$ $($GeV$/c)^2$, are subjected to a resonance-model fit using Breit-Wigner amplitudes to simultaneously describe a subset of 14 selected waves using 11 isovector light-meson states with $J^{PC} = 0^{-+}$, $1^{++}$, $2^{++}$, $2^{-+}$, $4^{++}$, and spin-exotic $1^{-+}$ quantum numbers. The model contains the well-known resonances $\pi(1800)$, $a_1(1260)$, $a_2(1320)$, $\pi_2(1670)$, $\pi_2(1880)$, and $a_4(2040)$. In addition, it includes the disputed $\pi_1(1600)$, the excited states $a_1(1640)$, $a_2(1700)$, and $\pi_2(2005)$, as well as the resonancelike $a_1(1420)$. We measure the resonance parameters mass and width of these objects by combining the information from the PWA results obtained in the 11 $t'$ bins. We extract the relative branching fractions of the $\rho(770) \pi$ and $f_2(1270) \pi$ decays of $a_2(1320)$ and $a_4(2040)$, where the former one is measured for the first time. In a novel approach, we extract the $t'$ dependence of the intensity of the resonances and of their phases. The $t'$ dependence of the intensities of most resonances differs distinctly from the $t'$ dependence of the nonresonant components. For the first time, we determine the $t'$ dependence of the phases of the production amplitudes and confirm that the production mechanism of the Pomeron exchange is common to all resonances.
A semi-inclusive measurement of charged hadron multiplicities in deep inelastic muon scattering off an isoscalar target was performed using data collected by the COMPASS Collaboration at CERN. The following kinematic domain is covered by the data: photon virtuality $Q^{2}>1$ (GeV/$c$)$^2$, invariant mass of the hadronic system $W > 5$ GeV/$c^2$, Bjorken scaling variable in the range $0.003 < x < 0.4$, fraction of the virtual photon energy carried by the hadron in the range $0.2 < z < 0.8$, square of the hadron transverse momentum with respect to the virtual photon direction in the range 0.02 (GeV/$c)^2 < P_{\rm{hT}}^{2} < 3$ (GeV/$c$)$^2$. The multiplicities are presented as a function of $P_{\rm{hT}}^{2}$ in three-dimensional bins of $x$, $Q^2$, $z$ and compared to previous semi-inclusive measurements. We explore the small-$P_{\rm{hT}}^{2}$ region, i.e. $P_{\rm{hT}}^{2} < 1$ (GeV/$c$)$^2$, where hadron transverse momenta are expected to arise from non-perturbative effects, and also the domain of larger $P_{\rm{hT}}^{2}$, where contributions from higher-order perturbative QCD are expected to dominate. The multiplicities are fitted using a single-exponential function at small $P_{\rm{hT}}^{2}$ to study the dependence of the average transverse momentum $\langle P_{\rm{hT}}^{2}\rangle$ on $x$, $Q^2$ and $z$. The power-law behaviour of the multiplicities at large $P_{\rm{hT}}^{2}$ is investigated using various functional forms. The fits describe the data reasonably well over the full measured range.
Exclusive production of $\rho^0$ mesons was studied at the COMPASS experiment by scattering 160 GeV/$c$ muons off transversely polarised protons. Five single-spin and three double-spin azimuthal asymmetries were measured as a function of $Q^2$, $x_{Bj}$, or $p_{T}^{2}$. The $\sin \phi_S$ asymmetry is found to be $-0.019 \pm 0.008(stat.) \pm 0.003(syst.)$. All other asymmetries are also found to be of small magnitude and consistent with zero within experimental uncertainties. Very recent calculations using a GPD-based model agree well with the present results. The data is interpreted as evidence for the existence of chiral-odd, transverse generalized parton distributions.
Results of a search for new physics in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an integrated luminosity of 139 fb$^{-1}$ at a center-of-mass energy of 13 TeV collected in the period 2015-2018 with the ATLAS detector at the Large Hadron Collider. Compared to previous publications, in addition to an increase of almost a factor of four in the data size, the analysis implements a number of improvements in the signal selection and the background determination leading to enhanced sensitivity. Events are required to have at least one jet with transverse momentum above 150 GeV and no reconstructed leptons ($e$, $\mu$ or $\tau$) or photons. Several signal regions are considered with increasing requirements on the missing transverse momentum starting at 200 GeV. Overall agreement is observed between the number of events in data and the Standard Model predictions. Model-independent $95%$ confidence-level limits on visible cross sections for new processes are obtained in the range between 736 fb and 0.3 fb. Results are also translated into improved exclusion limits in models with pair-produced weakly interacting dark-matter candidates, large extra spatial dimensions, supersymmetric particles in several compressed scenarios, axion-like particles, and new scalar particles in dark-energy-inspired models. In addition, the data are translated into bounds on the invisible branching ratio of the Higgs boson.
This is the HEPData space for the ATLAS monojet full Run 2 analysis. The full resolution figures can be found at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2018-06/ The full statistical likelihood is provided for this analysis. It can be downloaded by clicking on the purple 'Resources' button above and selecting the 'Common Resources' category. <br/><br/> <b>Post-fit $p_{\mathrm{T}}^{\mathrm{recoil}}$ distribution:</b> <ul> <li><a href="102093?version=3&table=HistogramCR1mu0b">CR1mu0b</a> <li><a href="102093?version=3&table=HistogramCR1e0b">CR1e0b</a> <li><a href="102093?version=3&table=HistogramCR1L1b">CR1L1b</a> <li><a href="102093?version=3&table=HistogramCR2mu">CR2mu</a> <li><a href="102093?version=3&table=HistogramCR2e">CR2e</a> <li><a href="102093?version=3&table=HistogramSR">SR</a> </ul> <b>Exclusion contours:</b> <ul> <li>Dark Matter axial-vector mediator: <ul> <li><a href="102093?version=3&table=ContourobsDMA">observed</a> <li><a href="102093?version=3&table=Contourobs_p1DMA">+1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=Contourobs_m1DMA">-1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=ContourexpDMA">expected</a> <li><a href="102093?version=3&table=Contourexp_p1DMA">+1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourexp_m1DMA">-1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourexp_p2DMA">+2 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourexp_m2DMA">-2 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourobs_xsecDMA">observed upper limits on the cross-sections</a> </ul> <li>Dark Matter pseudo-scalar mediator: <ul> <li><a href="102093?version=3&table=ContourobsDMP">observed</a> <li><a href="102093?version=3&table=Contourobs_p1DMP">+1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=Contourobs_m1DMP">-1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=ContourexpDMP">expected</a> <li><a href="102093?version=3&table=Contourexp_p1DMP">+1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourexp_m1DMP">-1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourexp_p2DMP">+2 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourexp_m2DMP">-2 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourobs_xsecDMP">observed upper limits on the cross-sections</a> </ul> <li>Dark Matter vector mediator: <ul> <li><a href="102093?version=3&table=ContourobsDMV">observed</a> <li><a href="102093?version=3&table=Contourobs_p1DMV">+1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=Contourobs_m1DMV">-1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=ContourexpDMV">expected</a> <li><a href="102093?version=3&table=Contourexp_p1DMV">+1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourexp_m1DMV">-1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourexp_p2DMV">+2 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourexp_m2DMV">-2 $\sigma$ expected</a> </ul> <li>Dark Matter spin-dependent WIMP-nucleon scattering cross-section: <a href="102093?version=3&table=ContourSDneutron">observed</a> <li>Dark Matter spin-independent WIMP-nucleon scattering cross-section: <a href="102093?version=3&table=ContourSInucleon">observed</a> <li>Dark Matter WIMP annihilation rate: <a href="102093?version=3&table=ContourID">observed</a> <li>SUSY stop pair production: <ul> <li><a href="102093?version=3&table=Contourg_obsTT_directCC">observed</a> <li><a href="102093?version=3&table=Contourg_obs_p1TT_directCC">+1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=Contourg_obs_m1TT_directCC">-1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=Contourg_expTT_directCC">expected</a> <li><a href="102093?version=3&table=Contourg_exp_p1TT_directCC">+1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourg_exp_m1TT_directCC">-1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourg_exp_p2TT_directCC">+2 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourg_exp_m2TT_directCC">-2 $\sigma$ expected</a> </ul> <li>SUSY stop pair production (4-body decay): <ul> <li><a href="102093?version=3&table=Contourg_obsTT_bffN">observed</a> <li><a href="102093?version=3&table=Contourg_obs_p1TT_bffN">+1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=Contourg_obs_m1TT_bffN">-1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=Contourg_expTT_bffN">expected</a> <li><a href="102093?version=3&table=Contourg_exp_p1TT_bffN">+1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourg_exp_m1TT_bffN">-1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourg_exp_p2TT_bffN">+2 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourg_exp_m2TT_bffN">-2 $\sigma$ expected</a> </ul> <li>SUSY sbottom pair production: <ul> <li><a href="102093?version=3&table=Contourg_obsBB">observed</a> <li><a href="102093?version=3&table=Contourg_obs_p1BB">+1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=Contourg_obs_m1BB">-1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=Contourg_expBB">expected</a> <li><a href="102093?version=3&table=Contourg_exp_p1BB">+1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourg_exp_m1BB">-1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourg_exp_p2BB">+2 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourg_exp_m2BB">-2 $\sigma$ expected</a> </ul> <li>SUSY squark pair production: <ul> <li><a href="102093?version=3&table=Contourg_obsSS">observed</a> <li><a href="102093?version=3&table=Contourg_obs_p1SS">+1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=Contourg_obs_m1SS">-1 $\sigma_{\mathrm{theory}}^{\mathrm{PDF+scale}}$ observed</a> <li><a href="102093?version=3&table=Contourg_expSS">expected</a> <li><a href="102093?version=3&table=Contourg_exp_p1SS">+1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourg_exp_m1SS">-1 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourg_exp_p2SS">+2 $\sigma$ expected</a> <li><a href="102093?version=3&table=Contourg_exp_m2SS">-2 $\sigma$ expected</a> </ul> <li>Dark energy: <a href="102093?version=3&table=ContourDE">observed and expected</a> <li>ADD: <a href="102093?version=3&table=ContourADD">observed and expected</a> <li>Axion-like particles: <a href="102093?version=3&table=ContourALPs">observed and expected</a> </ul> <b>Impact of systematic uncertainties:</b> <a href="102093?version=3&table=Tablesystimpacts">Table</a><br/><br/> <b>Yields of exclusive regions:</b> <a href="102093?version=3&table=TableyieldsEM0">EM0</a> <a href="102093?version=3&table=TableyieldsEM1">EM1</a> <a href="102093?version=3&table=TableyieldsEM2">EM2</a> <a href="102093?version=3&table=TableyieldsEM3">EM3</a> <a href="102093?version=3&table=TableyieldsEM4">EM4</a> <a href="102093?version=3&table=TableyieldsEM5">EM5</a> <a href="102093?version=3&table=TableyieldsEM6">EM6</a> <a href="102093?version=3&table=TableyieldsEM7">EM7</a> <a href="102093?version=3&table=TableyieldsEM8">EM8</a> <a href="102093?version=3&table=TableyieldsEM9">EM9</a> <a href="102093?version=3&table=TableyieldsEM10">EM10</a> <a href="102093?version=3&table=TableyieldsEM11">EM11</a> <a href="102093?version=3&table=TableyieldsEM12">EM12</a><br/><br/> <b>Yields of inclusive regions:</b> <a href="102093?version=3&table=TableyieldsIM0">IM0</a> <a href="102093?version=3&table=TableyieldsIM1">IM1</a> <a href="102093?version=3&table=TableyieldsIM2">IM2</a> <a href="102093?version=3&table=TableyieldsIM3">IM3</a> <a href="102093?version=3&table=TableyieldsIM4">IM4</a> <a href="102093?version=3&table=TableyieldsIM5">IM5</a> <a href="102093?version=3&table=TableyieldsIM6">IM6</a> <a href="102093?version=3&table=TableyieldsIM7">IM7</a> <a href="102093?version=3&table=TableyieldsIM8">IM8</a> <a href="102093?version=3&table=TableyieldsIM9">IM9</a> <a href="102093?version=3&table=TableyieldsIM10">IM10</a> <a href="102093?version=3&table=TableyieldsIM11">IM11</a> <a href="102093?version=3&table=TableyieldsIM12">IM12</a><br/><br/> <b>Cutflows:</b><br/><br/> Signals filtered with a truth $E_\mathrm{T}^\mathrm{miss}$ cut at: <a href="102093?version=3&table=Tablecutflows150GeV">150 GeV</a> <a href="102093?version=3&table=Tablecutflows350GeV">350 GeV</a><br/><br/>
The results of a study of the annihilation reactions n p → θπ + and n p → ωπ + are reported; the data were collected by the OBELIX apparatus, with antineutrons annihilating in flight (momenta from ∼ 50 MeV/ c to 405 MeV/ c ). Annihilation frequencies and annihilation cross sections have been deduced, for both channels, as a function of antineutron momentum. From the cross section ratio, a substantial deviation from OZI rule expectations is observed. An s s quark content in the nucleon offers a fairly plausible explanation for such an effect.
Based on a data sample of 10 billion $J/\psi$ events collected with the BESIII detector, improved measurements of the Dalitz decays $\eta/\eta'\rightarrow\gamma e^+e^-$ are performed, where the $\eta$ and $\eta'$ are produced through the radiative decays $J/\psi\rightarrow\gamma \eta/\eta'$. The branching fractions of $\eta\rightarrow\gamma e^+e^-$ and $\eta'\rightarrow\gamma e^+e^-$ are measured to be $(7.07 \pm 0.05 \pm 0.23)\times10^{-3}$ and $(4.83\pm0.07\pm0.14)\times10^{-4}$, respectively. Within the single pole model, the parameter of electromagnetic transition form factor for $\eta\rightarrow\gamma e^+e^-$ is determined to be $\Lambda_{\eta}=(0.749 \pm 0.027 \pm 0.007)~ {\rm GeV}/c^{2}$. Within the multi-pole model, we extract the electromagnetic transition form factors for $\eta'\rightarrow\gamma e^+e^-$ to be $\Lambda_{\eta'} = (0.802 \pm 0.007\pm 0.008)~ {\rm GeV}/c^{2}$ and $\gamma_{\eta'} = (0.113\pm0.010\pm0.002)~ {\rm GeV}/c^{2}$. The results are consistent with both theoretical predictions and previous measurements. The characteristic sizes of the interaction regions for the $\eta$ and $\eta'$ are calculated to be $(0.645 \pm 0.023 \pm 0.007 )~ {\rm fm}$ and $(0.596 \pm 0.005 \pm 0.006)~ {\rm fm}$, respectively. In addition, we search for the dark photon in $\eta/\eta^\prime\rightarrow\gamma e^{+}e^{-}$, and the upper limits of the branching fractions as a function of the dark photon are given at 90% confidence level.
The process e+e- --> pi+ pi- pi0 gamma has been studied at a center-of-mass energy near the Y(4S) resonance using a 89.3 fb-1 data sample collected with the BaBar detector at the PEP-II collider. From the measured 3pi mass spectrum we have obtained the products of branching fractions for the omega and phi mesons, B(omega --> e+e-)B(omega --> 3pi)=(6.70 +/- 0.06 +/- 0.27)10-5 and B(phi --> e+e-)B(phi --> 3pi)=(4.30 +/- 0.08 +/- 0.21)10-5, and evaluated the e+e- --> pi+ pi- pi0 cross section for the e+e- center-of-mass energy range 1.05 to 3.00 GeV. About 900 e+e- --> J/psi gamma --> pi+ pi- pi0 gamma events have been selected and the branching fraction B(J/psi --> pi+ pi- pi0)=(2.18 +/- 0.19)% has been measured.
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