The azimuthal correlation angle, Δϕ , between the scattered lepton and the leading jet in deep inelastic e^±p scattering at HERA has been studied using data collected with the ZEUS detector at a centre-of-mass energy of √(s) = 318 GeV , corresponding to an integrated luminosity of 326 pb^-1 . A measurement of jet cross sections in the laboratory frame was made in a fiducial region corresponding to photon virtuality 10 GeV^2< Q^2 < 350 GeV^2 , inelasticity 0.04< y < 0.7 , outgoing lepton energy E_e > 10 GeV , lepton polar angle 140^∘< θ _e < 180^∘ , jet transverse momentum 2.5 GeV< p_T,jet < 30 GeV , and jet pseudorapidity -1.5< η _jet < 1.8 . Jets were reconstructed using the k_T algorithm with the radius parameter R = 1 . The leading jet in an event is defined as the jet that carries the highest p_T,jet . Differential cross sections, dσ /dΔϕ , were measured as a function of the azimuthal correlation angle in various ranges of leading-jet transverse momentum, photon virtuality and jet multiplicity. Perturbative calculations at 𝒪(α _s^2) accuracy successfully describe the data within the fiducial region, although a lower level of agreement is observed near Δϕ→π for events with high jet multiplicity, due to limitations of the perturbative approach in describing soft phenomena in QCD. The data are equally well described by Monte Carlo predictions that supplement leading-order matrix elements with parton showering.

AbstractA new measurement of inclusive-jet cross sections in the Breit frame in neutral current deep inelastic scattering using the ZEUS detector at the HERA collider is presented. The data were taken in the years 2004–2007 at a centre-of-mass energy of $$318\,\,\textrm{GeV}$$ 318 GeV and correspond to an integrated luminosity of $$347\,\,\textrm{pb}^{-1}$$ 347 pb - 1 . The jets were reconstructed using the $$k_t$$ k t -algorithm in the Breit reference frame. They have been measured as a function of the squared momentum transfer, $$Q^2$$ Q 2 , and the transverse momentum of the jets in the Breit frame, $$p_{\perp ,\text {Breit}}$$ p ⊥ , Breit . The measured jet cross sections are compared to previous measurements and to perturbative QCD predictions. The measurement has been used in a next-to-next-to-leading-order QCD analysis to perform a simultaneous determination of parton distribution functions of the proton and the strong coupling, resulting in a value of $$\alpha _s(M_Z^2) = 0.1142 \pm 0.0017 \text {~(experimental/fit)}$$ α s ( M Z 2 ) = 0.1142 ± 0.0017 (experimental/fit) $${}_{-0.0007}^{+0.0006} \text {~(model/parameterisation)}$$ - 0.0007 + 0.0006 (model/parameterisation) $${}_{-0.0004}^{+0.0006} \text {~(scale)}$$ - 0.0004 + 0.0006 (scale) , whose accuracy is improved compared to similar measurements. In addition, the running of the strong coupling is demonstrated using data obtained at different scales.

An overview is presented of the ALFA forward detector system in the ATLAS detector at the LHC, CERN. Details of the construction are given, with summaries of the resulting analysis.

Lorentz and CPT symmetry in the quark sector of the Standard Model are studied in the context of an effective field theory using ZEUS $e^{\pm} p$ data. Symmetry-violating effects can lead to time-dependent oscillations of otherwise time-independent observables, including scattering cross sections. An analysis using five years of inclusive neutral-current deep inelastic scattering events corresponding to an integrated HERA luminosity of $372\; \text{pb}^{-1}$ at $\sqrt{s} = 318$ Gev has been performed. No evidence for oscillations in sidereal time has been observed within statistical and systematic uncertainties. Constraints, most for the first time, are placed on 42 coefficients parameterising dominant CPT-even dimension-four and CPT-odd dimension-five spin-independent modifications to the propagation and interaction of light quarks.

A bstract A search for the exclusive decays of the Higgs and Z bosons to a ϕ or ρ meson and a photon is performed with a pp collision data sample corresponding to an integrated luminosity of up to 35 . 6 fb −1 collected at $$ \sqrt{s}=13 $$ s = 13 TeV with the ATLAS detector at the CERN Large Hadron Collider. These decays have been suggested as a probe of the Higgs boson couplings to light quarks. No significant excess of events is observed above the background, as expected from the Standard Model. Upper limits at 95% confidence level were obtained on the branching fractions of the Higgs boson decays to ϕ γ and ρ γ of 4 . 8 × 10 −4 and 8 . 8 × 10 −4 , respectively. The corresponding 95% confidence level upper limits for the Z boson decays are 0 . 9 × 10 −6 and 25 × 10 −6 for ϕ γ and ρ γ, respectively.

A search for leptoquarks decaying into the bτ final state is performed using Run 2 proton-proton collision data from the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1 at √(s) = 13 TeV recorded by the ATLAS detector. The benchmark models considered in this search are vector leptoquarks with electric charge of 2/3e and scalar leptoquarks with an electric charge of 4/3e. No significant excess above the Standard Model prediction is observed, and 95

The total and differential Higgs boson production cross-sections are measured through a combined statistical analysis of the H → ZZ* → 4ℓ and H → γγ decay channels. The results are based on a dataset of 139 fb−1 of proton–proton collisions at a centre-of-mass energy of 13 TeV, recorded by the ATLAS detector at the Large Hadron Collider. The measured total Higgs boson production cross-section is 55.5_-3.8^+4.0 pb, consistent with the Standard Model prediction of 55.6 ± 2.5 pb. All results from the two decay channels are compatible with each other, and their combination agrees with the Standard Model predictions. A combined statistical interpretation of the measured fiducial cross-sections as a function of the Higgs boson transverse momentum is performed in order to probe the Yukawa couplings to the bottom and charm quarks. A similar interpretation is performed by including also the constraints from the measurements of Higgs boson production in association with a W or Z boson in the H → bb and cc decay channels.

AbstractThis article presents the results of two studies of Higgs boson properties using the $$WW^*(\rightarrow e\nu \mu \nu )jj$$ W W ∗ ( → e ν μ ν ) j j final state, based on a dataset corresponding to $${36.1}{{\mathrm{fb}}^{-1}}$$ 36.1 fb - 1 of $$\sqrt{s}=13$$ s = 13 TeV proton–proton collisions recorded by the ATLAS experiment at the Large Hadron Collider. The first study targets Higgs boson production via gluon–gluon fusion and constrains the CP properties of the effective Higgs–gluon interaction. Using angular distributions and the overall rate, a value of $$\tan (\alpha ) = 0.0 \pm 0.4 (\mathrm {stat.}) \pm 0.3 (\mathrm {syst.})$$ tan ( α ) = 0.0 ± 0.4 ( stat . ) ± 0.3 ( syst . ) is obtained for the tangent of the mixing angle for CP-even and CP-odd contributions. The second study exploits the vector-boson fusion production mechanism to probe the Higgs boson couplings to longitudinally and transversely polarised W and Z bosons in both the production and the decay of the Higgs boson; these couplings have not been directly constrained previously. The polarisation-dependent coupling-strength scale factors are defined as the ratios of the measured polarisation-dependent coupling strengths to those predicted by the Standard Model, and are determined using rate and kinematic information to be $$a_\mathrm {L}=0.91^{+0.10}_{-0.18}$$ a L = 0 . 91 - 0.18 + 0.10 (stat.)$$^{+0.09}_{-0.17}$$ - 0.17 + 0.09 (syst.) and $$a_{\mathrm {T}}=1.2 \pm 0.4 $$ a T = 1.2 ± 0.4 (stat.)$$ ^{+0.2}_{-0.3} $$ - 0.3 + 0.2 (syst.). These coupling strengths are translated into pseudo-observables, resulting in $$\kappa _{VV}= 0.91^{+0.10}_{-0.18}$$ κ VV = 0 . 91 - 0.18 + 0.10 (stat.)$$^{+0.09}_{-0.17}$$ - 0.17 + 0.09 (syst.) and $$\epsilon _{VV} =0.13^{+0.28}_{-0.20}$$ ϵ VV = 0 . 13 - 0.20 + 0.28 (stat.)$$^{+0.08}_{-0.10}$$ - 0.10 + 0.08 (syst.). All results are consistent with the Standard Model predictions.