Vector Boson Research Articles

DUNE potential as a new physics probe

Neutrino experiments, in the next years, aim to determine with precision all the six parameters of the three-neutrino standard paradigm. The complete success of the experimental program is, nevertheless, attached to the non-existence (or at least smallness) of Non-Standard Interactions (NSI). In this work, anticipating the data taken from long-baseline neutrino experiments, we map all the weakly coupled theories that could induce sizable NSI, with the potential to be determined in these experiments, in particular DUNE. Once present constraints from other experiments are taken into account, in particular charged-lepton flavor violation, we find that only models containing leptoquarks (scalar or vector) and/or neutral isosinglet vector bosons are viable. We provide the explicit matching formulas connecting weakly coupled models and NSI, both in propagation and production. Departing from the weakly coupled completion with masses at TeV scale, we also provide a global fit on all NSI for DUNE, finding that NSI smaller than 10−2 cannot be probed even in the best-case scenario.

Gravity: Where Quantum Physics and Classical Physics finally merge

In this 3rd paper of a triptych on quantum theory regarding gravity, quantum, and classical physics are merged seamlessly-however with conclusions deviating from classical physics regarding singularities, space-curvature, and graviton. Mathematically, singularities (Schwarzschild, Droste) vanish by proper definition of the gravity source and field descriptions acquiring full validity at the Planck scale. Space(-time) curvature is shown to be geodesic-trajectory curvature by (energy) objects in the field of (a) gravity source(s). The gravity field is found to be a scalar field in which the trajectories are defined only by the principle of least action (LaGrange, Feynman) by compensation of accelerations due to different physical causal sources of acceleration. The graviton is argued to be a massive Higgs-type scalar boson with ubiquitous presence since the creation of quantum and clustered mass in the universe: the influence of a settled gravity field on mass (in) entering this field, therefore, is instantaneous, i.e., unlike a vector boson description. Gravity waves, occurring in mergers/transitions of mass, are defined by changes in time of the gravity field (at max. c m/s) in space and only become observable when substantial mass/energy is involved due to the weakness and spatial decay of gravity fields. All mathematics (e.g. integral transformations, vector space, etc) and related operators in the paper are part of the Abelian group for validity at the Planck scale. Results thus constitute the description of gravity on all scales.‎‎

Curvature-bias corrections using a pseudomass method

Momentum measurements for very high momentum charged particles, such as muons from electroweak vector boson decays, are particularly susceptible to charge-dependent curvature biases that arise from misalignments of tracking detectors. Low momentum charged particles used in alignment procedures have limited sensitivity to coherent displacements of such detectors, and therefore are unable to fully constrain these misalignments to the precision necessary for studies of electroweak physics. Additional approaches are therefore required to understand and correct for these effects. In this paper the curvature biases present at the LHCb detector are studied using the pseudomass method in proton-proton collision data recorded at centre of mass energy √(s)=13 TeV during 2016, 2017 and 2018. The biases are determined using Z→μ + μ - decays in intervals defined by the data-taking period, magnet polarity and muon direction. Correcting for these biases, which are typically at the 10-4 GeV-1 level, improves the Z→μ + μ - mass resolution by roughly 18% and eliminates several pathological trends in the kinematic-dependence of the mean dimuon invariant mass.

Probing left-handed heavy neutral leptons in the Vector Scotogenic Model

In this work, we consider an extension to the Standard Model composed by a Massive Vector Doublet under SU(2)L and a Left-handed Heavy Neutral Lepton. We study the production of these exotic leptons with the Same Flavor Opposite Sign standard lepton pair, and jets, considering Drell-Yan and Vector Boson Fusion as independent cases. We find that for the latter, the dilepton angular distribution is different enough from the background to use it as a smoking-gun for our model. Based on this fact, we establish limits on the parameter space considering previous experimental searches in this final state.

Proposal for an Electromagnetic Mass Formula for the X17 Particle

Recent observations of anomalous angular correlations of electron–positron pairs in several nuclear reactions have indicated the existence of a hypothetical neutral boson of rest mass ~17 MeV/c2, called the X17 particle. Similarly, one has interpreted an independent set of experiments on photon pair spectra around the invariant mass ~38 MeV/c2, by assuming the existence of the so-called E38 particle. In the present paper, we derive analytical mass formulas for the X17 particle and the E38 particle, on the basis of quantum electrodynamics. We shall use the exact solutions of the Dirac equation of the joint system of a charged particle and plane waves of the quantized electromagnetic radiation. When these solutions are applied to a proton, they lead to dressed radiation quanta with a rest mass of 17.0087 MeV/c2, which may be identified with the X17 vector bosons. A similar consideration, applied to the udd quarks of the neutron, yields dressed quanta, whose mass equals 37.9938 MeV/c2, corresponding to the E38 particle. These formulas, besides the Sommerfeld fine structure constant and the masses of the nucleons, do not contain any adjustable parameters. The present analysis also delivers the value 0.846299 fm for the proton radius.

Search for non-resonant Higgs boson pair production in the 2b+2ℓ+ETmiss\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ 2b+2\\ell +{E}_{\ extrm{T}}^{\ extrm{miss}} $$\\end{document} final state in pp collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV with the ATLAS detector

A search for non-resonant Higgs boson pair (HH) production is presented, in which one of the Higgs bosons decays to a b-quark pair (bb¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ b\\overline{b} $$\\end{document}) and the other decays to WW*, ZZ*, or τ+τ−, with in each case a final state with ℓ+ℓ−+ neutrinos (ℓ = e, μ). The analysis targets separately the gluon-gluon fusion and vector boson fusion production modes. Data recorded by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb−1, are used in this analysis. Events are selected to have exactly two b-tagged jets and two leptons with opposite electric charge and missing transverse momentum in the final state. These events are classified using multivariate analysis algorithms to separate the HH events from other Standard Model processes. No evidence of the signal is found. The observed (expected) upper limit on the cross-section for non-resonant Higgs boson pair production is determined to be 9.7 (16.2) times the Standard Model prediction at 95% confidence level. The Higgs boson self-interaction coupling parameter κλ and the quadrilinear coupling parameter κ2V are each separately constrained by this analysis to be within the ranges [−6.2, 13.3] and [−0.17, 2.4], respectively, at 95% confidence level, when all other parameters are fixed.

Vector bosons in the rotating frame of negative curvature wormholes

In this study, we investigate the relativistic dynamics of vector bosons within the context of rotating frames of negative curvature wormholes. We seek exact solutions for the fully-covariant vector boson equation, derived as an excited state of zitterbewegung. This equation encompasses a symmetric rank-two spinor, enabling the derivation of a non-perturbative second-order wave equation for the system under consideration. Our findings present exact results in two distinct scenarios. Notably, we demonstrate the adaptability of our results to massless vector bosons without compromising generality. The evolution of this system is shown to correlate with the angular frequency of the uniformly rotating reference frame and the curvature radius of the wormholes. Moreover, our results highlight that the interplay between the spin of the vector boson and the angular frequency of the rotating frame can give rise to real oscillation modes, particularly evident in excited states for massless vector bosons. Intriguingly, we note that the energy spectra obtained remain the same whether the wormhole is of hyperbolic or elliptic nature.

Next-to-leading-logarithmic PanScales showers for deep inelastic scattering and vector boson fusion

We introduce the first family of parton showers that achieve next-to-leading logarithmic (NLL) accuracy for processes involving a t-channel exchange of a colour-singlet, and embed them in the PanScales framework. These showers are applicable to processes such as deep inelastic scattering (DIS), vector boson fusion (VBF), and vector boson scattering (VBS). We extensively test and verify the NLL accuracy of the new showers at both fixed order and all orders across a wide range of observables. We also introduce a generalisation of the Cambridge-Aachen jet algorithm and formulate new DIS observables that exhibit a simple resummation structure. The NLL showers are compared to a standard transverse-momentum ordered dipole shower, serving as a proxy for the current state-of-the-art leading-logarithmic showers available in public codes. Depending on the observable, we find discrepancies at NLL of the order of 15%. We also present some exploratory phenomenological results for Higgs production in VBF. This work enables, for the first time, to resum simultaneously global and non-global observables for the VBF process at NLL accuracy.

Search for Higgs Boson Production via Vector Boson Fusion Process with Subsequent $$H \to b\bar {b}$$ Decay with CMS Experiment at LHC

Search for Higgs Boson Production via Vector Boson Fusion Process with Subsequent $$H \to b\bar {b}$$ Decay with CMS Experiment at LHC

Alternative 3-3-1 models with exotic electric charges

We report the most general classification of 3-3-1 models with β=3 . We found several solutions where anomaly cancellation occurs among fermions of different families. These solutions are particularly interesting as they generate non-universal heavy neutral vector bosons. Non-universality in the standard model fermion charges under an additional gauge group generates charged lepton flavor violation and flavor changing neutral currents; we discuss under what conditions the new models can evade constraints coming from these processes. In addition, we also report the Large Hadron Collider~(LHC) constraints.

SMEFT at NNLO+PS: Vh production

In the context of the Standard Model effective field theory (SMEFT) the next-to-next-to-leading (NNLO) QCD corrections to the Higgsstrahlungs (Vh) processes in hadronic collisions are calculated and matched to a parton shower (PS). NNLO+PS precision is achieved for the complete sets of SMEFT operators that describe the interactions between the Higgs and two vector bosons and the couplings of the Higgs, a W or a Z boson, and light fermions. A POWHEG-BOX implementation of the computed NNLO SMEFT corrections is provided that allows for a realistic exclusive description of Vh production at the level of hadronic events. This feature makes it an essential tool for future Higgs characterisation studies by the ATLAS and CMS collaborations. Utilising our new Monte Carlo code the numerical impact of NNLO+PS corrections on the kinematic distributions in pp → Zh → ℓ+ℓ−h production is explored, employing well-motivated SMEFT benchmark scenarios.

Measurement of the Higgs boson production via vector boson fusion and its decay into bottom quarks in proton-proton collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV

A measurement of the Higgs boson (H) production via vector boson fusion (VBF) and its decay into a bottom quark-antiquark pair (bb¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \ extrm{b}\\overline{\ extrm{b}} $$\\end{document}) is presented using proton-proton collision data recorded by the CMS experiment at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV and corresponding to an integrated luminosity of 90.8 fb−1. Treating the gluon-gluon fusion process as a background and constraining its rate to the value expected in the standard model (SM) within uncertainties, the signal strength of the VBF process, defined as the ratio of the observed signal rate to that predicted by the SM, is measured to be μHbb¯qqh=1.01−0.46+0.55\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\mu}_{\ extrm{Hb}\\overline{\ extrm{b}}}^{\ extrm{qqh}}={1.01}_{-0.46}^{+0.55} $$\\end{document}. The VBF signal is observed with a significance of 2.4 standard deviations relative to the background prediction, while the expected significance is 2.7 standard deviations. Considering inclusive Higgs boson production and decay into bottom quarks, the signal strength is measured to be μHbb¯incl.=0.99−0.41+0.48\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\mu}_{\ extrm{Hb}\\overline{\ extrm{b}}}^{\ extrm{incl}.}={0.99}_{-0.41}^{+0.48} $$\\end{document}, corresponding to an observed (expected) significance of 2.6 (2.9) standard deviations.

Winos from natural SUSY at the high luminosity LHC

In natural supersymmetric models defined by no worse than a part in thirty electroweak fine-tuning, winos and binos are generically expected to be much heavier than Higgsinos. Moreover, the splitting between the Higgsinos is expected to be small, so that the visible decay products of the heavier Higgsinos are soft, rendering the Higgsinos quasi-invisible at the LHC. Within the natural supersymmetry (SUSY) framework, heavy electroweak gauginos decay to W, Z or h bosons plus Higgsinos in the ratio ∼2∶1∶1, respectively. This is in sharp contrast to models with a binolike lightest superpartner and very heavy Higgsinos, where the charged (neutral) wino essentially always decays to a W (h) boson and an invisible bino. Wino pair production at the LHC, in natural SUSY, thus leads to VV, Vh and hh+ET final states (V=W, Z) where, for TeV scale winos, the vector bosons and h daughters are considerably boosted. We identify eight different channels arising from the leptonic and hadronic decays of the vector bosons and the decay h→bb¯, each of which offers an avenue for wino discovery at the high luminosity LHC (HL-LHC). By combining the signal in all eight channels we find, assuming s=14 TeV and an integrated luminosity of 3000 fb−1, that the discovery reach for winos extends to m(wino)∼1.1 TeV, while the 95% CL exclusion range extends to a wino mass of almost 1.4 TeV. We also identify “Higgsino specific channels” which could serve to provide 3σ evidence that winos lighter than 1.2 TeV decay to light Higgsinos rather than to a binolike lightest supersymmetric particle, should a wino signal appear at the HL-LHC. Published by the American Physical Society 2024

Higgs associated production with a vector decaying to two fermions in the geoSMEFT

We present the inclusive calculations of a Higgs boson produced in association with massive vector bosons in the Standard Model Effective Field Theory (SMEFT) to order 1/\Lambda^41/Λ4 for the 13 TeV LHC. The calculations include the decay of the vector boson into massless constituents and are done using the geometric formulation of the SMEFT supplemented by the relevant dimension eight operators not included in the geoSMEFT. We include some discussion of distributions to motivate how detailed collider and experimental searches for SMEFT signals could be improved.

New physics implications of vector boson fusion searches exemplified through the Georgi-Machacek model

New physics implications of vector boson fusion searches exemplified through the Georgi-Machacek model

Taking aim at the wino-Higgsino plane with the LHC

In this work we explore multiple search strategies for Higgsinos and mixed Higgsino-wino states in the minimal supersymmetric Standard Model (MSSM) and project the results onto the (μ,M2) plane. Assuming associated production of Higgsino-like pairs with a W/Z boson, we develop a search in a channel characterized by a hadronically tagged vector boson accompanied by missing energy. We use as our template an ATLAS search for dark matter produced in association with a hadronically decaying vector boson, but upgrade the search by implementing a joint-likelihood analysis, binning the missing transverse energy distribution, which greatly improves the search sensitivity. For Higgsino-like states (more than 96% admixture) we find sensitivity to masses up to 550 GeV. For well-mixed Higgsino-wino states (70–30% Higgsino) we still find sensitivities above 300 GeV. Using this newly proposed search, we draw a phenomenological map of the wino-Higgsino parameter space, recasting several complementary searches for disappearing tracks, soft leptons, trileptons, and hadronic diboson events in order to predict LHC coverage of the (μ,M2) mass plane at integrated luminosities of up to 3 ab−1. Altogether, the full run of the HL-LHC can exclude much of the “natural” (μ,M2<500 GeV) wino-Higgsino parameter space. Published by the American Physical Society 2024

Quantum corrections and the minimal Yukawa sector of SU(5)

It is well known that the SU(5) grand unified theory, with the standard model quarks and leptons unified in 5¯ and 10 and the electroweak Higgs doublet residing in five-dimensional representations, leads to the relation Yd=YeT between the Yukawa couplings of the down-type quarks and the charged leptons. We show that this degeneracy can be lifted in a phenomenologically viable way when quantum corrections to the tree-level matching conditions are taken into account in the presence of one or more copies of gauge singlet fermions. The one-loop threshold corrections arising from heavy leptoquark scalar and vector bosons, already present in the minimal model, and heavy singlet fermions can lead to realistic Yukawa couplings, provided their masses differ by at least 2 orders of magnitude. The latter can also lead to a realistic light neutrino mass spectrum through the type I seesaw mechanism if the color partner of the Higgs stays close to the Planck scale. Most importantly, our findings demonstrate the viability of the simplest Yukawa sector when quantum corrections are considered and sizable threshold effects are present. Published by the American Physical Society 2024

Measuring lepton number violation in heavy neutral lepton decays at the future muon collider

The future muon collider has the potential to discover feebly interacting particles in a wide range of masses above the electroweak scale. It is particularly suitable to search for heavy neutral leptons (HNLs), as their production cross section σ∼mW−2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sigma \\sim {m}_W^{-2} $$\\end{document} is not suppressed by the new physics scale. We demonstrate that with the capacity to observe up to 105 events in the previously unexplored TeV mass range, the muon collider provides the means to measure the fraction of lepton number violating (LNV) processes with precision at the level of a percent. This capability enables elucidating the nature of HNLs, allowing us to differentiate between Majorana, Dirac, and non-minimal scenarios featuring multiple degenerate HNLs. We link the observed fraction of LNV processes to the parameters of the model with three degenerate HNLs, which could be responsible for generating baryon asymmetry in the Universe. Additionally, we present a simple estimate for the number of signal events, as well as analyze the feasibility of vector boson fusion processes in searches for HNLs.

Precise predictions for boosted Higgs production

Inclusive Higgs boson production at large transverse momentum is induced by different production channels. We focus on the leading production mechanism through gluon fusion, and perform a consistent combination of the state of the art calculations obtained in the infinite-top-mass effective theory at next-to-next-to-leading order (NNLO) and in the full Standard Model (SM) at next-to-leading order (NLO). We thus present approximate QCD predictions for this process at NNLO, and a study of the corresponding perturbative uncertainties. This calculation is then compared with those obtained with commonly used event generators, and we observe that the description of the considered kinematic regime provided by these tools is in good agreement with state of the art calculations. Finally, we present accurate predictions for other production channels such as vector boson fusion, and associated production with a gauge boson, and with a t\bar{t}tt‾ pair. We find that, at large transverse momentum, the contribution of other production modes is substantial, and therefore must be included for a precise theory prediction of this observable.

Differential cross-section measurements of the production of four charged leptons in association with two jets using the ATLAS detector

Differential cross-sections are measured for the production of four charged leptons in association with two jets. These measurements are sensitive to final states in which the jets are produced via the strong interaction as well as to the purely-electroweak vector boson scattering process. The analysis is performed using proton-proton collision data collected by ATLAS at sqrt{s} = 13 TeV and with an integrated luminosity of 140 fb−1. The data are corrected for the effects of detector inefficiency and resolution and are compared to state-of-the-art Monte Carlo event generator predictions. The differential cross-sections are used to search for anomalous weak-boson self-interactions that are induced by dimension-six and dimension-eight operators in Standard Model effective field theory.