Search

We report on the complete computation of the mixed QCD-electroweak corrections to the neutral-current Drell-Yan process. Our calculation holds in the entire range of dilepton invariant masses. We present phenomenological results for several kinematical distributions in the case of bare muons both in the resonant region and for high invariant masses. We also consider the forward-backward asymmetry, which is a key observable to measure the weak mixing angle. We finally extend our calculation to dressed leptons and compare our results in the massless limit to those available in the literature., Comment: 27 pages, 7 Figures, and 2 Tables

We present a generator for lepton nucleon collisions in the DIS regime, focusing in particular on processes with a massive lepton and/or a massive quark in the final state. We have built a full code matching NLO QCD corrections to parton shower Monte Carlo programs in the POWHEG-BOX framework. Our code can be used to compute NLO+PS accurate fully differential predictions for neutral current and charged current processes, including processes with an incoming tau neutrino, and/or including charm quarks in the final state. We also made comparisons with available data and predictions for the new neutrino experiments at CERN., Comment: 51 pages, 29 figures, 2 tables, LaTeX

We consider neutral- and charged-current Drell Yan lepton-pair production at hadron colliders, and include dominant classes of electroweak and mixed QCD-electroweak corrections to all orders in perturbation theory. The accurate description of these physical effects is vital for a precise determination of fundamental Standard Model parameters, such as the $W$-boson mass and the electroweak mixing angle, as well as for a solid assessment of the associated theoretical uncertainties. Our state-of-the-art resummation reaches next-to-leading-logarithmic accuracy in both the electroweak and the mixed QCD-electroweak perturbative expansions, including constant terms at first order beyond Born level in both couplings, i.e. at order $\alpha$ and $\alpha_s \alpha$. These effects are incorporated on top of QCD predictions at next-to-next-to-next-to-leading-logarithmic accuracy, which include constant terms at third order in the strong coupling. Our results retain, for the first time at this accuracy, full dependence on the kinematics of the final-state leptons, thereby enabling a realistic comparison with experimental analyses at the differential level in presence of fiducial cuts. We present a phenomenological analysis of the impact of electroweak corrections in relevant observables at the LHC. We find visible shape distortions in resummation-dominated kinematical regions with respect to pure-QCD predictions, highlighting the importance of a complete description, not limited to QCD, for precision Drell Yan physics., Comment: 23 pages, 13 figures

We consider subleading power corrections to event shape variables in $e^+e^-$ collisions at the first order in the QCD coupling $\alpha_s$. We start from the jettiness variable $\tau_2$ and the $y_{23}$ resolution variable for the $k_T$ jet clustering algorithm and we analytically compute the corresponding cumulative cross section. We investigate the origin of the different power suppressed contributions in the two-jet limit and trace it back to their different coverage of the phase space. We extend our analysis to the case of thrust and of the $C$-parameter, and we finally discuss a class of observables that depend on a continuous parameter giving different weight to central and forward emissions and we evaluate the corresponding subleading power corrections., Comment: 16 pages, 4 figures. Minor modifications and updated references. Version published in EPJC

Scenarios with new physics particles feebly interacting with the Standard Model sector provide compelling candidates for dark matter searches. Geared with a set of new experiments for the detection of neutrinos and long-lived particles the Large Hadron Collider (LHC) has joined the hunt for these elusive states. On the theoretical side, this emerging physics program requires reliable estimates of the associated particle fluxes, in particular those arising from heavy hadron decays. In this work, we provide state-of-the-art QCD predictions for heavy hadron production including radiative corrections at next-to-leading order and using parton distribution functions including small-$x$ resummation at next-to-leading logarithmic accuracy. We match our predictions to parton showers to provide a realistic description of hadronisation effects. We demonstrate the utility of our predictions by presenting the energy spectrum of neutrinos from charm hadron decays. Furthermore, we employ our predictions to estimate, for the first time, FASER's sensitivity to electrophilic ALPs, which are predominantly generated in beauty hadron decays., Comment: 12 pages, 8 figures. Version published in EPJC

We consider the class of inclusive hadron collider processes in which one or more energetic jets are produced, possibly accompanied by colourless particles. We provide a general formulation of a slicing scheme for this class of processes, by identifying the various contributions that need to be computed up to next-to-leading order (NLO) in QCD perturbation theory. We focus on two novel observables, the one-jet resolution variable $\Delta E_t$ and the $n$-jet resolution variable $k_{T}^{\mathrm{ness}}$, and explicitly compute all the ingredients needed to carry out NLO computations using these variables. We contrast the behaviour of these variables when the slicing parameter becomes small. In the case of $k_{T}^{\mathrm{ness}}$ we also present results for the hadroproduction of multiple jets., Comment: 47 pages, 3 figures. Minor modifications. Version published in JHEP

The production of a top-antitop quark pair in association with a $W$ boson ($t\bar tW$) is one of the heaviest signatures currently probed at the Large Hadron Collider (LHC). Since the first observation reported in 2015 the corresponding rates have been found to be consistently higher than the Standard Model predictions, which are based on next-to-leading order~(NLO) calculations in the QCD and electroweak (EW) interactions. We present the first next-to-next-to-leading order (NNLO) QCD computation of $t\bar tW$ production at hadron colliders. The calculation is exact, except for the finite part of the two-loop virtual corrections, which is estimated using two different approaches that lead to consistent results within their uncertainties. We combine the newly computed NNLO QCD corrections with the complete NLO QCD+EW results, thus obtaining the most advanced perturbative prediction available to date for the \ttW inclusive cross section. The tension with the latest ATLAS and CMS results remains at the $1\sigma-2\sigma$ level., Comment: 7 pages, 3 figures, 1 table. Minor changes, version published on PRL

We present the first calculation for the hadroproduction of a $W$ boson in association with a massive bottom ($b$) quark-antiquark pair at next-to-next-to-leading order (NNLO) in QCD perturbation theory. We exploit the hierarchy between the $b$ quark mass and the characteristic energy scale of the process to obtain a reliable analytic expression for the two-loop virtual amplitude with three massive legs, starting from the corresponding result available for massless bottom quarks. The use of massive $b$ quarks avoids the ambiguities associated with the correct flavour assignment in massless calculations, paving the way to a more realistic comparison with experimental data. We present phenomenological results considering proton-proton collisions at centre-of-mass energy $\sqrt{s}=13.6$ TeV for inclusive $Wb \bar b$ production and within a fiducial region relevant for the associated production of a $W$ boson and a Higgs boson decaying into a $b \bar b$ pair, for which $Wb \bar b$ production represents one of the most relevant backgrounds. We find that the NNLO corrections are substantial and that their inclusion is mandatory to obtain reliable predictions., Comment: 8 pages, 2 figures, 2 tables. Final version published in PRD

Recent progress in calculating lepton density functions inside the proton and simulating lepton showers laid the foundations for precision studies of resonant leptoquark production at hadron colliders. Direct quark-lepton fusion into a leptoquark is a novel production channel at the LHC that has the potential to probe a unique parameter space for large masses and couplings. In this work, we build the first Monte Carlo event generator for a full-fledged simulation of this process at NLO for production, followed by a subsequent decay using the POWHEG method and matching to the parton showers utilizing HERWIG. The code can handle all scalar leptoquark models with renormalisable quark-lepton interactions. We then comprehensively study the differential distributions, including higher-order effects, and asses the corresponding theoretical uncertainties. We also quantify the impact of the improved predictions on the projected (HL-)LHC sensitivities and initiate the first exploration of the potential at the FCC-hh. Our work paves the way toward performing LHC searches using this channel., Comment: 33 pages, 7 figures, 3 tables

We summarize the current status and near future prospects for next-to-next-to-leading order calculations matched to parton shower based on the MiNNLO$_{\rm PS}$ method. We give a theoretical overview, illustrate selected results for $ZZ\to 4\ell$ and top-pair production processes at the LHC, and provide an outlook of the future challenges., Comment: Contribution to Snowmass 2022

We consider the class of inclusive hadron collider processes in which several energetic jets are produced, possibly accompanied by colourless particles (such as Higgs boson(s), vector boson(s) with their leptonic decays, and so forth). We propose a new variable that smoothly captures the $N+1$ to $N$-jet transition. This variable, that we dub $k_T^{\rm ness}$, represents an effective transverse momentum controlling the singularities of the $N+1$-jet cross section when the additional jet is unresolved. The $k_T^{\rm ness}$ variable offers novel opportunities to perform higher-order calculations in Quantum Chromodynamics (QCD) by using non-local subtraction schemes. We study the singular behavior of the $N+1$-jet cross section as $k_T^{\rm ness}\to 0$ and, as a phenomenological application, we use the ensuing results to evaluate next-to-leading order corrections to $H$+jet and $Z$+2 jet production at the LHC. We show that $k_T^{\rm ness}$ performs extremely well as a resolution variable and appears to be very stable with respect to hadronization and multiple-parton interactions., Comment: 9 pages, 3 figures. Added appendix with details on jet and soft functions at NLO. Version published in Phys.Rev.D

Transverse-momentum cuts on undistinguished particles in two-body final states induce an enhanced sensitivity to low momentum scales. This undesirable feature, which ultimately leads to an instability of the fixed-order series, poses additional challenges to non-local subtraction schemes. In this letter, we address this issue for general colour-singlet processes within the $q_T$-subtraction formalism, focussing on neutral-current Drell-Yan production. We present a simple procedure to reduce the dependence on the slicing parameter from linear to quadratic, by accounting for the linear power corrections through an appropriate recoil prescription. We observe a dramatical improvement of the numerical convergence and a reduction of the systematic uncertainties. We also discuss how a linear dependence in $q_T$ can be avoided for Drell-Yan production by using staggered cuts, which, to the best of our understanding, could be used in experimental analyses. We show that our approach can be successfully applied also to on-shell $ZZ$ production. We finally study diphoton production and verify that our approach is insufficient to capture the linear power corrections introduced by the isolation procedure. The recoil prescription is available in version 2.1 of MATRIX., Comment: 11 pages, 9 figures. Added comparison with local subtraction at NNLO. Version published in Phys.Lett.B

We discuss recent theoretical results for the complete mixed QCD-EW corrections to lepton-pair production via the Drell-Yan mechanism, a cornerstone process for the precision physics programme at the LHC. We present results for fiducial cross sections and differential distributions to both the neutral current- and charged current- process. We show that the mixed corrections are relatively large and of similar size to the NNLO QCD ones at central scales. In particular, for the neutral current case, we report the first result at this order that is valid in the entire range of dilepton invariant masses., Comment: 6 pages, 2 figures, 1 table; contribution to the proceedings of the EPS-HEP 2021 conference. arXiv admin note: text overlap with arXiv:2110.15464

We discuss about a recent computation of the mixed QCD--EW corrections to the hadroproduction of a massive charged lepton plus the corresponding neutrino through the Drell--Yan mechanism. The calculation, based on an extension of the $q_T$ subtraction formalism for heavy-quark production in next-to-next-to leading order QCD, includes for the first time all the real and virtual contributions due to initial- and final-state radiation, except for the finite part of the two-loop virtual correction, which is approximated in the pole approximation. We report results for the fiducial cross section and the transverse momentum spectrum of the charged lepton., Comment: 8 pages, 1 table, 2 figures; contribution to Radcor-LoopFest 2021

We consider the associated production of a vector or Higgs boson with a jet in hadronic collisions. When the transverse momentum $q_T$ of the boson-jet system is much smaller than its invariant mass $Q$, the QCD perturbative expansion is affected by large logarithmic terms that must be resummed to all orders. We discuss the all-order resummation structure of the logarithmically enhanced contributions up to next-to-leading logarithmic accuracy. Resummation is performed at the differential level with respect to the kinematical variables of the boson-jet system. Soft-parton radiation produces azimuthal correlations that are fully accounted for in our framework. We present explicit analytical results for the resummation coefficients up to next-to-leading order and next-to-leading logarithmic accuracy, that include the exact dependence on the jet radius., Comment: 18 pages, 1 appendix

We study a few basic photon- and lepton-initiated processes at the LHC which can be computed using the recently developed photon and lepton parton densities. First, we consider the production of a massive scalar particle initiated by lepton-antilepton annihilation and photon-photon fusion as representative examples of searches of exotic particles. Then we study lepton-lepton scattering, since this Standard-Model process may be observable at the LHC. We examine these processes at leading and next-to-leading order and, using the POWHEG method, we match our calculations to parton shower programs that implement the required lepton or photon initial-states. We assess the typical size of cross-sections and their uncertainties and discuss the preferred choices for the factorization scale. These processes can also be computed starting directly from the lepto-production hadronic tensor, leading to a result where some collinear-enhanced QED corrections are missing, but all strong corrections are included. Thus, we are in the unique position to perform a comparison of results obtained via the factorization approach to a calculation that does not have strong corrections. This is particularly relevant in the case of lepton-scattering, that is more abundant at lower energies where it is affected by larger strong corrections. We thus compute this process also with the hadronic-tensor method, and compare the results with those obtained with POWHEG. Finally, for some lepton-lepton scattering processes, we compare the size of the signal to the main quark-induced background, which is double Drell-Yan production, and outline a preliminary search strategy to enhance the signal to background ratio., Comment: 35 pages, 28 figures

We consider $ZZ$ production in hadronic collisions and present state-of-the-art predictions in QCD perturbation theory matched to parton showers. Next-to-next-to-leading order corrections to the quark-initiated channel are combined with parton showers using the MiNNLO$_{\text{PS}}$ method, while next-to-leading order corrections to the loop-induced gluon fusion channel are matched using the POWHEG method. Their combination, dubbed nNNLO+PS, constitutes the best theoretical description of $ZZ$ events to date. Spin correlations, interferences and off-shell effects are included by calculating the full process $pp \to \ell^+\ell^-\ell^{(\prime)+}\ell^{(\prime)-}$. We show the crucial impact of higher-order corrections for both quark- and gluon-initiated processes as well as the relevance of the parton shower in certain kinematical regimes. Our predictions are in very good agreement with recent LHC data., Comment: 32 pages, 7 figures, 2 tables

We report on the first complete computation of the mixed QCD$-$electroweak (EW) corrections to the neutral-current Drell$-$Yan process. Superseding previously applied approximations, our calculation provides the first result at this order that is valid in the entire range of dilepton invariant masses. The two-loop virtual contribution is computed by using semi-analytical techniques, overcoming the technical problems in the evaluation of the relevant master integrals. The cancellation of soft and collinear singularities is achieved by a formulation of the $q_T$ subtraction formalism valid in presence of charged massive particles in the final state. We present numerical results for the fiducial cross section and selected kinematical distributions. At large values of the lepton $p_T$ the mixed QCD$-$EW corrections are negative and increase in size, to about $-15\%$ with respect to the next-to-leading-order QCD result at $p_T=500\,$GeV. Up to dilepton invariant masses of 1 TeV the computed corrections amount to about $-1.5\%$ with respect to the next-to-leading-order QCD result., Comment: 8 pages, 2 figures and 1 table

Next generation neutrino oscillation experiments like DUNE and T2HK are multi-purpose observatories, with a rich physics program beyond oscillation measurements. A special role is played by their near detector facilities, which are particularly well-suited to search for weakly coupled dark sector particles produced in the primary target. In this paper, we demonstrate this by estimating the sensitivity of the DUNE near detectors to the scattering of sub-GeV DM particles and to the decay of sub-GeV sterile neutrinos ("heavy neutral leptons"). We discuss in particular the importance of the DUNE-PRISM design, which allows some of the near detectors to be moved away from the beam axis. At such off-axis locations, the signal-to-background ratio improves for many new physics searches. We find that this leads to a dramatic boost in the sensitivity to boosted DM particles interacting mainly with hadrons, while for boosted DM interacting with leptons, data taken on-axis leads to marginally stronger exclusion limits. Searches for heavy neutral leptons perform equally well in both configurations., Comment: 28 pages, 13 figures, 1 table; v2: minor clarifications, added references, slight improvement of projected HNL limits, updated comparison with external HNL limits to include recent literature

As is the case for all light coloured Standard Model particles, also photons and charged leptons appear as constituents in ultrarelativistic hadron beams, and admit a parton density function (PDF). It has been shown recently that the photon PDF can be given in terms of the structure functions and form factors for electron-proton scattering. The same holds for lepton PDFs. In the present work we set up a calculation of the lepton PDFs at next-to-leading order, using the same data input needed in the photon case. A precise knowledge of the lepton densities allows us to study lepton-initiated processes even at a hadron collider, with all possible combinations of same-charge, opposite-charge, same-flavour, different-flavour leptons and leptons-quarks, most of which cannot be realized in any other foreseeable experiment. The lepton densities in the proton are extremely small, so that their contribution to Standard Model processes is generally shadowed by processes initiated by coloured partons. We will show, however, that there are cases where these processes can be relevant, giving rise to rare Standard Model signatures and to new production channels, that can enlarge the discovery potential of New Physics at the LHC and future high energy colliders with hadrons in the initial state., Comment: 43 pages, 14 figures. In V2 we have included a class of subleading O(alpha^2) contributions to the lepton PDFs and motivated this choice. Data in the LHAPDF files have been updated accordingly (see info file). V2 is identical to the published version

Processes commonly studied at the Large Hadron Collider (LHC) are induced by quarks and gluons inside the protons of the LHC beams. In this letter we demonstrate that, since protons also contain leptons, it is possible to target lepton-induced processes at the LHC as well. In particular, by picking a lepton from one beam and a quark from the other beam, we present for the first time a comprehensive analysis of resonant single leptoquark (LQ) production at a hadron collider. In the case of minimal scalar LQs, we derive novel bounds that arise from the LHC Run II considering all possible flavour combinations of an electron or a muon and an up ($u$), a down ($d$), a strange or a charm quark. For the flavour combinations with a $u$ or a $d$ quark, the obtained limits represent the most stringent constraints to date on LQs of this type. The prospects of our method at future LHC runs are also explored. Given the discovery reach of the proposed LQ signature, we argue that dedicated resonance searches in final states featuring a single light lepton and a single light-flavour jet should be added to the exotics search canon of both the ATLAS and the CMS collaboration., Comment: 7 pages, 4 figures, v2: extended version of the manuscript that has been accepted for publication by PRL

We survey the sensitivity of past and present neutrino experiments to MeV-GeV scale dark matter, and find that these experiments possess novel sensitivity that has not yet fully explored. NO$\nu$A and BEBC are found to rule out the scalar thermal target for dark matter masses between 10 MeV to 100 MeV with existing data, while CHARM-II and MINER$\nu$A place somewhat weaker limits. These limits can be dramatically improved by off-axis searches using the NuMI beamline and the MicroBooNE, MiniBooNE or ICARUS detectors, and can even begin to probe the Majorana thermal target. We conclude that past and present neutrino facilities can search for light dark matter concurrently with their neutrino program and reach a competitive sensitivity to proposed future experiments., Comment: 16 pages, 2 figures. v2 Added additional references and a few additional comments

The $q_T$ subtraction formalism represents a well established and successful technique to deal with the computation of QCD radiative corrections up to NNLO (and beyond) for a large class of processes relevant at the LHC. We have explored the possibility to apply $q_T$ subtraction to the computation of EW corrections with the (final) aim to develop a subtraction formalism suitable for the computation of mixed QCD-EW corrections. We present numerical results for the complete NLO EW corrections to the Drell-Yan production of a massive lepton pair. Furthermore, we have investigated the structure of the power suppressed contributions at small-$q_T$ in this process and we present new analytical results on the effects of the soft radiation emitted off a charged massive final state., Comment: 11 pages, 3 figures, to appear in the proceedings of the 14th International Symposium on Radiative Corrections (RADCOR2019)

Building upon the formulation of transverse-momentum resummation for heavy-quark hadroproduction, we present the first application of the $q_T$ subtraction formalism to the computation of electroweak corrections to massive lepton pairs through the Drell-Yan mechanism. We then study the power suppressed contributions to the $q_T$ subtraction formula in the parameter $r_{cut}$, defined as the minimum transverse momentum of the lepton pair normalised to its invariant mass. We analytically compute the leading power correction from initial and final-state radiation to the inclusive cross section. In the case of initial-state radiation the power correction is quadratic in $r_{cut}$ and our analytic result is consistent with results previously obtained in the literature. Final-state radiation produces linear contributions in $r_{cut}$ that may challenge the efficiency of the $q_T$ subtraction procedure. We explicitly compute the linear power correction in the case of the inclusive cross section and we discuss the extension of our calculation to differential distributions., Comment: LaTeX, 22 pages, 4 figures

A wealth of new physics models which are motivated by questions such as the nature of dark matter, the origin of the neutrino masses and the baryon asymmetry in the universe, predict the existence of hidden sectors featuring new particles. Among the possibilities are heavy neutral leptons, vectors and scalars, that feebly interact with the Standard Model (SM) sector and are typically light and long lived. Such new states could be produced in high-intensity facilities, the so-called beam dump experiments, either directly in the hard interaction or as a decay product of heavier mesons. They could then decay back to the SM or to hidden sector particles, giving rise to peculiar decay or interaction signatures in a far-placed detector. Simulating such kind of events presents a challenge, as not only short-distance new physics (hard production, hadron decays, and interaction with the detector) and usual SM phenomena need to be described but also the travel has to be accounted for as determined by the geometry of the detector. In this work, we describe a new plugin to the {\sc MadGraph5\_aMC@NLO} platform, which allows the complete simulation of new physics processes relevant for beam dump experiments, including the various mechanisms for the production of hidden particles, namely their decays or scattering off SM particles, as well as their far detection, keeping into account spatial correlations and the geometry of the experiment., Comment: LaTeX, 42 pages, 14 figures