The instanton vacuum picture is used to study hadronic matrix elements of the twist-3 (dimension-4, spin-1) QCD operators measuring the quark spin density and spin-orbit correlations. The QCD ...operators are converted to effective operators in the low-energy effective theory emerging after chiral symmetry breaking, in a systematic approach based on the diluteness of the instanton medium and the 1/Nc expansion. The instanton fields induce spin-flavor-dependent "potential" terms in the effective operators, complementing the "kinetic" terms from the quark field momenta. As a result, the effective operators obey the same equation-of-motion relations as the original QCD operators. The spin-orbit correlations are qualitatively different from naive quark model expectations.
The inclusive top-quark-pair production cross section σ$t\overline{t}$ and its ratio to the Z-boson production cross section have been measured in proton–proton collisions at $\sqrt{s}$ = 13.6 TeV, ...using 29 fb—1 of data collected in 2022 with the ATLAS experiment at the Large Hadron Collider. Using events with an opposite-charge electron-muon pair and b-tagged jets, and assuming Standard Model decays, the top-quark-pair production cross section is measured to be σ$t\overline{t}$ = 850± 3(stat.) ± 18(syst.) ± 20(lumi.) pb. The ratio of the $t\overline{t}$ and the Z-boson production cross sections is also measured, where the Z-boson contribution is determined for inclusive e+e— and μ+μ— events in a fiducial phase space. The relative uncertainty on the ratio is reduced compared to the $t\overline{t}$ cross section, thanks to the cancellation of several systematic uncertainties. The result for the ratio, R$t\overline{t}/Z$ = 1.145 ± 0.003(stat.) ± 0.021(syst.)±0.002(lumi.) is consistent with the Standard Model prediction using the PDF4LHC21 PDF set.
In this Letter, the first measurement of the inelastic cross section for antitriton–nucleus interactions is reported, covering the momentum range of 0.8 ≤ p < 2.4 GeV/c. The measurement is carried ...out using data recorded with the ALICE detector in pp and Pb–Pb collisions at a centre-of-mass energy per nucleon of 13 TeV and 5.02 TeV, respectively. The detector material serves as an absorber for antitriton nuclei. The raw yield of (anti)triton nuclei measured with the ALICE apparatus is compared to the results from detailed ALICE simulations based on the GEANT4 toolkit for the propagation of (anti)particles through matter, allowing one to quantify the inelastic interaction probability in the detector material. This analysis complements the measurement of the inelastic cross section of antinuclei up to A = 3 carried out by the ALICE Collaboration, and demonstrates the feasibility of the study of the isospin dependence of inelastic interaction cross section with the analysis techniques presented in this Letter.
A search for new charged massive gauge bosons, called W1 , is performed with the ATLAS detector at the LHC, in proton–proton collisions at a centre-of-mass energy of √s=8 TeV, using a dataset ...corresponding to an integrated luminosity of 20.3 fb-1. This analysis searches for W1 bosons in the W1 →t¯b decay channel in final states with electrons or muons, using a multivariate method based on boosted decision trees. The search covers masses between 0.5 and 3.0 TeV, for right-handed or left-handed W1 bosons. No significant deviation from the Standard Model expectation is observed and limits are set on the W1 →t¯b cross-section times branching ratio and on the W1 -boson effective couplings as a function of the W -boson mass using the CLs procedure. For a left-handed (right-handed) W1 boson, masses below 1.70 (1.92) TeV are excluded at 95% confidence level.
Semi-visible jets, with a significant contribution to the event's missing transverse momentum, can arise in strongly interacting dark sectors. This results in an event topology where one of the jets ...can be aligned with the direction of the missing transverse momentum. The first search for semi-visible jets produced via a t-channel mediator exchange is presented. The analysis uses proton-proton collisions with an integrated luminosity of 139 fb—1 and a centre-of-mass energy of 13 TeV, collected with the ATLAS detector during the Run 2 of the LHC. No excess over Standard Model predictions is observed. Assuming a coupling strength of unity between the mediator, a Standard Model quark and a dark quark, mediator masses up to 2.7 TeV are excluded at the 95% confidence level. Upper limits on the coupling strength are also derived.
We study the incoherent multiple scattering effects on heavy meson production in the backward rapidity region of p+A collisions within the generalized high-twist factorization formalism. We calculate ...explicitly the double scattering contributions to the heavy meson differential cross sections by taking into account both initial-state and final-state interactions, and find that these corrections are positive. We further evaluate the nuclear modification factor for muons that come form the semi-leptonic decays of heavy flavor mesons. Phenomenological applications in d+Au collisions at a center-of-mass energy s=200 GeV at RHIC and in p+Pb collisions at s=5.02 TeV at the LHC are presented. We find that incoherent multiple scattering can describe rather well the observed nuclear enhancement in the intermediate pT region for such reactions.
A search for exotic decays of the Higgs boson (H) with a mass of 125 GeV to a pair of light pseudoscalars a1 is performed in final states where one pseudoscalar decays to two b quarks and the other ...to a pair of muons or τ leptons. A data sample of proton–proton collisions at $\sqrt{s} = 13 TeV corresponding to an integrated luminosity of 138 fb-1 recorded with the CMS detector is analyzed. No statistically significant excess is observed over the standard model backgrounds. Upper limits are set at 95% confidence level (CL) on the Higgs boson branching fraction to μμ b b and to ττ b b via a pair of a1s. The limits depend on the pseudoscalar mass ma1 and are observed to be in the range (0.17–3.3) x 10-4 and (1.7–7.7) x 10-2 in the μμ b b and ττ b b final states, respectively. In the framework of models with two Higgs doublets and a complex scalar singlet (2HDM+S), the results of the two final states are combined to determine upper limits on the branching fraction $\mathcal{B}$(H→a1a1→ ℓℓ b b) at 95% CL, with ℓ being a muon or a τ lepton. For different types of 2HDM+S, upper bounds on the branching fraction are extracted from the combination of the two channels. In most of the Type II 2HDM+S parameter space, $\mathcal{B}$(H→a1a1) values above 0.23 are excluded at 95% CL for ma1 values between 15 and 60 GeV.
The spectroscopic quadrupole moment of the first 2+ state of 12C has been measured employing the Coulomb-excitation re-orientation technique. Our result of Qs(21+)=+9.3−3.8+3.5efm2 suggests a larger ...oblate deformation than previously reported. Combining this with the consistently re-analyzed adopted value, we present the most precise value to date of Qs(21+)=+9.5(18)efm2, which is consistent with a geometrical rotor description. This simple outcome is compared to state-of-the-art shell-model, mean-field, ab initio calculations, cluster-based and geometrical-like theories, which show varying degrees of emergent quadrupole collectivity.
Abstract JSNS $$^2$$ 2 (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron Source) is an experiment that searches for sterile neutrinos via the observation of $$\bar{\nu }_{\mu } ...\rightarrow \bar{\nu }_{e}$$ ν ¯ μ → ν ¯ e appearance oscillations using muon decay-at-rest neutrinos. The JSNS $$^2$$ 2 experiment performed data taking from 2021. In this manuscript, a study of the accidental background is presented. The rate of the accidental background is ( $$9.29\pm 0.39) \times 10^{-8}$$ 9.29 ± 0.39 ) × 10 - 8 /spill with 0.75 MW beam power and comparable to the expected number of signal events.
A search for a new massive charged gauge boson, $W'$, is performed with the ATLAS detector at the LHC. The dataset used in this analysis was collected from proton–proton collisions at a ...centre-of-mass energy of $\sqrt{s}$ = 13 TeV, and corresponds to an integrated luminosity of 139 fb-1. The reconstructed tb invariant mass is used to search for a $W'$ boson decaying into a top quark and a bottom quark. The result is interpreted in terms of a $W'$ boson with purely right-handed or left-handed chirality in a mass range of 0.5–6 TeV. Different values for the coupling of the $W'$ boson to the top and bottom quarks are considered, taking into account interference with single-top-quark production in the $s$-channel. No significant deviation from the background prediction is observed. The results are expressed as upper limits on the $W'$ → $tb$ production cross-section times branching ratio as a function of the $W'$-boson mass and in the plane of the coupling vs the $W'$-boson mass.
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