Heavy Vector Bosons Research Articles

Two-loop five-point two-mass planar integrals and double Lagrangian insertions in a Wilson loop

We consider the complete set of planar two-loop five-point Feynman integrals with two off-shell external legs. These integrals are relevant, for instance, for the calculation of the second-order QCD corrections to the production of two heavy vector bosons in association with a jet or a photon at a hadron collider. We construct pure bases for these integrals and reconstruct their analytic differential equations in canonical form through numerical sampling over finite fields. The newly identified symbol alphabet, one of the most complex to date, provides valuable data for bootstrap methods. We then apply our results to initiate the study of double Lagrangian insertions in a four-cusp Wilson loop in planar maximally supersymmetric Yang-Mills theory, computing it through two loops. We observe that it is finite, conformally invariant in four dimensions, and of uniform transcendentality. Furthermore, we provide numerical evidence for its positivity within the amplituhedron region through two loops.

First constraints on non-minimally coupled Natural and Coleman-Weinberg inflation and massive neutrino self-interactions with Planck+BICEP/Keck

In this work, for the first time in literature, we study the predictions of non-minimally coupled Natural and Coleman-Weinberg potentials in the ns -r plane, and an extended ΛCDM model where we include non-standard self-interactions among massive neutrinos, mediated by a heavy scalar or vector boson. Constraints were derived using the Planck 2018 + BICEP/Keck 2018 datasets along with other data. For the inflationary potentials, we consider two different formulations in gravity that are non-minimally coupled to the scalar field of the inflaton: Metric and Palatini. We only consider the self-interaction to be present among τ-neutrinos and only at moderate strengths. This is because strong interactions among τ-neutrinos, or any strength self-interaction among electron- and muon-neutrinos, as well as any strength flavor-universal interactions, are strongly disfavoured from particle physics experiments.In terms of cosmological data, we use the latest public CMB datasets from Planck 2018 and BICEP/Keck 2018 collaborations, along with other data from CMB lensing, BAO, RSD, and SNe Ia luminosity distance measurements. We find that there are some situations where predictions from the inflationary models are ruled out at more than 2σ by the minimal ΛCDM+r model, but they are allowed in the self-interacting neutrino scenario.

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.

Dissipation of axion energy via the Schwinger and Witten effects

In the presence of an anomalous CP phase in a U(1) gauge theory, a monopole becomes a dyon via the Witten effect. When the anomalous CP phase is promoted to a dynamical field, the axion, the electric charge of the dyon changes according to the coherent motion of the axion oscillation. Once the electric charge exceeds a certain threshold, the Schwinger pair production of charged particles becomes efficient near the surface of the dyon. These nonperturbative effects lead to the backreaction of the axion dynamics by causing the dissipation of the axion oscillation energy and the change of the effective potential due to the Witten effect. Taking these effects into account, we consider the dynamics of the whole system, including the axion, monopole, and charged heavy vector bosons, and discuss to what extent the axion abundance is modified. We also discuss the electric dipole radiation from a bound state of a monopole-antimonopole pair due to the axion coherent oscillations. 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

Probing new physics through entanglement in diboson production

Pair production of heavy vector bosons is a key process at colliders: it allows to test our understanding of the Standard Model and to explore the existence of new physics through precision measurements of production rates and differential distributions. New physics effects can be subtle and often require observables specifically designed for their detection. In this study, we focus on quantum information observables that characterise the spin states of the final diboson system. We analyse concurrence bounds, purity, and Bell inequalities for a bipartite qutrit system representing two massive gauge bosons. Our findings show that quantum spin observables can serve as complementary probes for heavy new physics as parametrised by higher dimensional operators in the Standard Model effective field theory. In particular, we find that these observables offer increased sensitivity to operators whose contributions do not interfere with the Standard Model amplitudes at the level of differential cross sections.

Impact of freeze-in on dark matter isocurvature

Dark matter freeze-in is a compelling cosmological production mechanism in which all or some of the observed abundance of dark matter is generated through feeble interactions it has with the Standard Model. In this work we present the first analysis of freeze-in dark matter fluctuations and consider two benchmark models: freeze-in through the direct decay of a heavy vector boson and freeze-in through pair annihilation of Standard Model particles in the thermal bath. We provide a theoretical framework for determining the impact of freeze-in on curvature and dark matter isocurvature perturbations. We determine freeze-in dark matter fluid properties from first principles, tracking its evolution from its relativistic production to its final cold state, and calculate the evolution of the dark matter isocurvature perturbation. We find that in the absence of initial isocurvature, the freeze-in production of dark matter does not source isocurvature. However, for an initial isocurvature perturbation seeded by inflation, the nonthermal freeze-in process may allow for a fraction of the isocurvature to persist, in contrast to the exponential suppression it receives in the case of thermal dark matter. In either case, the evolution of the curvature mode is unaffected by the freeze-in process. We show sensitivity projections of future cosmic microwave background experiments to the amplitude of uncorrelated, totally anticorrelated, and totally correlated dark matter isocurvature perturbations. From these projections, we infer the sensitivity to the abundance of freeze-in dark matter that sustains some fraction of the primordial isocurvature.

Master integrals for electroweak corrections to gg→γγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$gg\\rightarrow \\gamma \\gamma $$\\end{document}: light quark contributions

We present a calculation of the master integrals (MI’s) required for the calculation of the Electroweak corrections to gg→γγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$gg\\rightarrow \\gamma \\gamma $$\\end{document} production in which the process contains a light quark loop. The integrals can be broken down into five categories based on the flow of the heavy vector bosons throughout the loop. Three of the families are planar, and two are non-planar. We determine a canonical basis for each family which allows an efficient solution of the resulting differential equations via iterated integrals. We calculate the families in relevant physical kinematics and obtain an efficient numerical evaluation based on an implementation of Chen-iterated integrals.

Search for new physics in the τ lepton plus missing transverse momentum final state 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 search for physics beyond the standard model (SM) in the final state with a hadronically decaying tau lepton and a neutrino is presented. This analysis is based on data recorded by the CMS experiment from proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC, corresponding to a total integrated luminosity of 138 fb−1. The transverse mass spectrum is analyzed for the presence of new physics. No significant deviation from the SM prediction is observed. Limits are set on the production cross section of a W′ boson decaying into a tau lepton and a neutrino. Lower limits are set on the mass of the sequential SM-like heavy charged vector boson and the mass of a quantum black hole. Upper limits are placed on the couplings of a new boson to the SM fermions. Constraints are put on a nonuniversal gauge interaction model and an effective field theory model. For the first time, upper limits on the cross section of t-channel leptoquark (LQ) exchange are presented. These limits are translated into exclusion limits on the LQ mass and on its coupling in the t-channel. The sensitivity of this analysis extends into the parameter space of LQ models that attempt to explain the anomalies observed in B meson decays. The limits presented for the various interpretations are the most stringent to date. Additionally, a model-independent limit is provided.

Dark photon dark matter from cosmic strings and gravitational wave background

Dark photon dark matter may be produced by the cosmic strings in association with the dark U(1) gauge symmetry breaking. We perform three-dimensional lattice simulations of the Abelian-Higgs model and follow the evolution of cosmic strings. In particular, we simulate the case of (very) light vector boson and find that such vector bosons are efficiently produced by the collapse of small loops while the production is inefficient in the case of heavy vector boson. We calculate the spectrum of the gravitational wave background produced by the cosmic string loops for the light vector boson case and find characteristic features in the spectrum, which can serve as a probe of the dark photon dark matter scenario. In particular, we find that the current ground-based detectors may be sensitive to such gravitational wave signals and also on-going/future pulsar timing observations give stringent constraint on the dark photon dark matter scenario.

The 2HDM doppelganger

We discuss the structure of a model with an extended gauge symmetry group SU(2)times SU(2)times U(1) with a correspondingly rich Electroweak Symmetry Breaking structure. In spite of the additional scalar degrees of freedom in the model, the presence of the extra gauge group SU(2) and its associated heavy vector bosons ensures that the scalar spectrum of the model after symmetry breaking is identical to that of the Two Higgs Doublet Models. We construct the model and discuss its implications, specifically the phenomenology associated with this class of models in contrast to the 2HDM.

Top quark phenomena in association with new vector bosons

In this work, we study collider phenomenology of pair produced new heavy vector bosons further decaying into top quark pair and quartic top, top pair plus bottom pair production in proton-proton collisions at CERN LHC with 13 TeV center of mass energy in the presence of new color octet vector boson. The complete simulation chain analysis from parton to the detector level is done for the pair production, As for the four quark production through pair of the new heavy vector particles is doneat the matrix level. In doing so we have preparatory work . The extension of SM is implemented by Mathematica—FeynRule package. Calculations are done by MadGraph5 /+ Phythia6, Delphes / simulation program and results are analysed in ROOT CERN. In conclusion, we compared Standard model extension results with the SM.

Search for heavy particles in the b -tagged dijet mass distribution with additional b -tagged jets in proton-proton collisions at s=13 TeV with the ATLAS experiment

A search optimized for new heavy particles decaying to two b-quarks and produced in association with additional b-quarks is reported. The sensitivity is improved by b-tagging at least one lower-pT jet in addition to the two highest-pT jets. The data used in this search correspond to an integrated luminosity of 103 fb−1 collected with a dedicated trijet trigger during the 2017 and 2018 s=13 TeV proton-proton collision runs with the ATLAS detector at the LHC. The search looks for resonant peaks in the b-tagged dijet invariant mass spectrum over a smoothly falling background. The background is estimated with an innovative data-driven method based on orthonormal functions. The observed b-tagged dijet invariant mass spectrum is compatible with the background-only hypothesis. Upper limits at 95% confidence level on a heavy vector-boson production cross section times branching ratio to a pair of b-quarks are derived.Received 23 August 2021Accepted 11 November 2021DOI:https://doi.org/10.1103/PhysRevD.105.012001Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.© 2022 CERN, for the ATLAS CollaborationPhysics Subject Headings (PhySH)Research AreasExtensions of Higgs sectorExtensions of gauge sectorParticles & Fields

Search for dark matter produced in association with a Standard Model Higgs boson decaying into b-quarks using the full Run 2 dataset from the ATLAS detector

The production of dark matter in association with Higgs bosons is predicted in several extensions of the Standard Model. An exploration of such scenarios is presented, considering final states with missing transverse momentum and b-tagged jets consistent with a Higgs boson. The analysis uses proton-proton collision data at a centre-of-mass energy of 13 TeV recorded by the ATLAS experiment at the LHC during Run 2, amounting to an integrated luminosity of 139 fb−1. The analysis, when compared with previous searches, benefits from a larger dataset, but also has further improvements providing sensitivity to a wider spectrum of signal scenarios. These improvements include both an optimised event selection and advances in the object identification, such as the use of the likelihood-based significance of the missing transverse momentum and variable-radius track-jets. No significant deviation from Standard Model expectations is observed. Limits are set, at 95% confidence level, in two benchmark models with two Higgs doublets extended by either a heavy vector boson Z′ or a pseudoscalar singlet a and which both provide a dark matter candidate χ. In the case of the two-Higgs-doublet model with an additional vector boson Z′, the observed limits extend up to a Z′ mass of 3 TeV for a mass of 100 GeV for the dark matter candidate. The two-Higgs-doublet model with a dark matter particle mass of 10 GeV and an additional pseudoscalar a is excluded for masses of the a up to 520 GeV and 240 GeV for tan β = 1 and tan β = 10 respectively. Limits on the visible cross-sections are set and range from to 0.05 fb to 3.26 fb, depending on the missing transverse momentum and b-quark jet multiplicity requirements.

Search for a heavy vector resonance decaying to a {mathrm{Z}}_{mathrm{}}^{mathrm{}} \xa0boson and a Higgs boson in proton-proton collisions at sqrt{s} = 13,text {Te}text {V}

A search is presented for a heavy vector resonance decaying into a {mathrm{Z}}_{mathrm{}}^{mathrm{}} boson and the standard model Higgs boson, where the {mathrm{Z}}_{mathrm{}}^{mathrm{}} boson is identified through its leptonic decays to electrons, muons, or neutrinos, and the Higgs boson is identified through its hadronic decays. The search is performed in a Lorentz-boosted regime and is based on data collected from 2016 to 2018 at the CERN LHC, corresponding to an integrated luminosity of 137,text {fb}^{-1}. Upper limits are derived on the production of a narrow heavy resonance {mathrm{{{mathrm{Z}}_{mathrm{}}^{mathrm{}}}}}_{mathrm{}}^{mathrm{prime }}, and a mass below 3.5 and 3.7,text {Te}text {V} is excluded at 95% confidence level in models where the heavy vector boson couples predominantly to fermions and to bosons, respectively. These are the most stringent limits placed on the Heavy Vector Triplet {mathrm{{{mathrm{Z}}_{mathrm{}}^{mathrm{}}}}}_{mathrm{}}^{mathrm{prime }} model to date. If the heavy vector boson couples exclusively to standard model bosons, upper limits on the product of the cross section and branching fraction are set between 23 and 0.3,text {fb} for a {mathrm{{{mathrm{Z}}_{mathrm{}}^{mathrm{}}}}}_{mathrm{}}^{mathrm{prime }} mass between 0.8 and 4.6,text {Te}text {V}, respectively. This is the first limit set on a heavy vector boson coupling exclusively to standard model bosons in its production and decay.

Muon Discrepancy Within D‐brane String Compactifications

AbstractVery recently, the Muon g − 2 experiment at Fermilab has confirmed the E821 Brookhaven result, which hinted at a deviation of the muon anomalous magnetic moment from the Standard Model (SM) expectation. The combined results from Brookhaven and Fermilab show a difference with the SM prediction δaμ = (251 ± 59) × 10−11 at a significance of 4.2σ, strongly indicating the presence of new physics. Motivated by this new result we reexamine the contributions to δaμ from both: (i) the ubiquitous U(1) gauge bosons of D‐brane string theory constructions and (ii) the Regge excitations of the string. We show that, for a string scale , the contribution from anomalous U(1) gauge bosons which couple to hadrons could help to reduce (though not fully eliminate) the discrepancy reported by the Muon g − 2 Collaboration. Consistency with null results from LHC searches of new heavy vector bosons imparts the dominant constraint. We demonstrate that the contribution from Regge excitations is strongly suppressed as it was previously conjectured. We also comment on contributions from Kaluza‐Klein (KK) modes, which could help resolve the δaμ discrepancy. In particular, we argue that for 4‐stack intersecting D‐brane models, the KK excitations of the U(1) boson living on the lepton brane would not couple to hadrons and therefore can evade the LHC bounds while fully bridging the δaμ gap observed at Brookhaven and Fermilab.

Light quark Yukawas in triboson final states

Triple heavy vector boson production, pp → VVV (V = W, Z), has recently been observed for the first time. We propose that precision measurements of this process provide an excellent probe of the first generation light quark Yukawa couplings. Modified quark interactions with the off-shell Higgs in this process lead to a rapid growth of the partonic cross sections with energy, which manifests in an enhanced pT distribution of the final state leptons and quarks. We quantify this effect and estimate the present and future 2σ sensitivity to the up, down, and strange Yukawas. In particular, we find that HL-LHC can reach mathcal{O}(400) sensitivity to the down Yukawa relative to the Standard Model value, improving the current sensitivity in this process by a factor of 10, and which can be further improved to mathcal{O}(30) at FCC-hh. This is competitive with and complementary to constraints from global fits and other on-shell probes of the first generation Yukawas. The triboson sensitivity at HL-LHC corresponds to probing dimension-6 SMEFT operators suppressed by an mathcal{O}(1) TeV scale, similarly to other LHC Higgs probes.

Novel B -decay signatures of light scalars at high energy facilities

We study the phenomenology of light scalars of masses $m_1$ and $m_2$ coupling to heavy flavour-violating vector bosons of mass $m_V$. For $m_{1,2}\lesssim $ few GeV, this scenario triggers the rare $B$ meson decays $B_s^0\to 3\mu^+ 3\mu^-$, $B^0\to 3\mu^+ 3\mu^-$, $B^+\to K^+ 3\mu^+ 3\mu^-$ and $B_s^0\to K^{0*} 3\mu^+ 3\mu^-$; the last two being the most important ones for $m_1\sim m_2$. None of these signals has been studied experimentally; therefore we propose analyses to test these channels at the LHCb. We demonstrate that the reach of this facility extends to branching ratios as small as $6.0\times 10^{-9}$, $1.6\times 10^{-9}$, $5.9\times 10^{-9}$ and $1.8\times 10^{-8}$ for the aforementioned channels, respectively. For $m_{1,2}\gg \mathcal{O}(1)$ GeV, we show that slightly modified versions of current multilepton and multitau searches at the LHC can probe wide regions of the parameter space of this scenario. Altogether, the potential of the searches we propose outperform other constraints such as those from meson mixing.

Combination of CMS searches for heavy resonances decaying to pairs of bosons or leptons

A statistical combination of searches for heavy resonances decaying to pairs of bosons or leptons is presented. The data correspond to an integrated luminosity of 35.9 fb−1 collected during 2016 by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. The data are found to be consistent with expectations from the standard model background. Exclusion limits are set in the context of models of spin-1 heavy vector triplets and of spin-2 bulk gravitons. For mass-degenerate W′ and Z′ resonances that predominantly couple to the standard model gauge bosons, the mass exclusion at 95% confidence level of heavy vector bosons is extended to 4.5 TeV as compared to 3.8 TeV determined from the best individual channel. This excluded mass increases to 5.0 TeV if the resonances couple predominantly to fermions.

Searching new physics in rare B-meson decays into multiple muons

New heavy vector bosons and light scalars are predicted in a plethora of models of new physics. In particular, in new strongly interacting sectors they play the role of the rho and pi mesons in QCD. We show that some of their interactions, for example those required for the explanation of the B anomalies and the g-2 of the muon, can be only probed in B meson decays. We highlight new golden channels not yet studied experimentally, including B^+ rightarrow K^+(D^+)mu ^+mu ^-mu ^+mu ^- and B^0rightarrow K^{*0}mu ^+mu ^-mu ^+mu ^-. Relying on generator level simulations for data taking with the LHCb detector, we determine the reach of this facility to the aforementioned processes. We show that branching ratios as small as 9times 10^{-12} (3.2times 10^{-10}) and 2.7times 10^{-11} can be tested at the 95% CL respectively.