Boson Mass Research Articles

Measurement of the effective weak mixing angle at the CEPC* *Supported by the "USTC Research Funds of the Double First-Class Initiative", the International Partnership Program of Chinese Academy of Sciences (113111KYSB20190030) and the Innovative Scientific Program of Institute of High Energy Physics

We present a study of the measurement of the effective weak mixing angle parameter () at the Circular Electron Positron Collider (CEPC). As a fundamental physics parameter, plays a key role not only in the global test of the standard model electroweak sector, but also in constraining the potential beyond standard model new physics at the high energy frontier. CEPC proposes a two year running period around the Z boson mass pole at high instataneous luminosity, providing a large data sample with candidates generated in total. It allows a high precision measurement of both in the lepton and quark final states, where the uncertainty can be one order of magnitude lower than any previous measurement at the LEP, SLC, Tevatron, and LHC. It will improve the overall precision of the experimental determination to be comparable to the preicision of the theoretical calculation with two-loop radiative corrections, and it will also provide direct comparisons between different final states. In this paper, we also study the measurement of in the high mass region. Taking data for one month, the precision of measured at 130 GeV from b quark final state is 0.00010, which will be an important experimental observation on the energy-running effect of .

CDF W mass anomaly revisited

The CDF, ATLAS, and LHCb have released the measurements on the W boson mass m_W at sqrt{S}=1.96, 7, 13 TeV, respectively. The measured values show the declining tendency, namely m_W decreases with the increment of the collider energy. If the declining tendency is confirmed, it might be the signal of metric field at high-energy colliders. In this paper, we propose a model to account for such tendency and explore the properties of the model.

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.

Gravitational echoes of lepton number symmetry breaking with light and ultralight Majorons

We formulate a version of the low-scale Majoron model equipped with an inverse seesaw mechanism featuring lepton-number preserving dimension-6 operators in the scalar potential. Contrary to its dimension-4 counterpart, we find that the model can simultaneously provide light and ultralight Majorons, neutrino masses and their mixing, while featuring strong first-order cosmological phase transitions associated to the spontaneous breaking of the lepton number and the electroweak symmetries in the early Universe. We show by a detailed numerical analysis under which circumstances the model can be probed via the primordial gravitational wave spectrum potentially observable at LISA and other planned facilities. We discuss which implications result for collider physics observables, such as scalar trilinear couplings, the scalar mixing angle and the mass of a new CP-even Higgs boson.

Towards gg → HH at next-to-next-to-leading order: Light-fermionic three-loop corrections

We consider light-fermion three-loop corrections to gg→HH using forward scattering kinematics in the limit of a vanishing Higgs boson mass, which covers a large part of the physical phase space. We compute the form factors and discuss the technical challenges. The approach outlined in this letter can be used to obtain the full virtual corrections to gg→HH at next-to-next-to-leading order.

Bounds on lepton non-unitarity and heavy neutrino mixing

We present an updated and improved global fit analysis of current flavour and electroweak precision observables to derive bounds on unitarity deviations of the leptonic mixing matrix and on the mixing of heavy neutrinos with the active flavours. This new analysis is motivated by new and updated experimental results on key observables such as Vud, the invisible decay width of the Z boson and the W boson mass. It also improves upon previous studies by considering the full correlations among the different observables and explicitly calibrating the test statistic, which may present significant deviations from a χ2 distribution. The results are provided for three different Type-I seesaw scenarios: the minimal scenario with only two additional right-handed neutrinos, the next to minimal one with three extra neutrinos, and the most general one with an arbitrary number of heavy neutrinos that we parametrise via a generic deviation from a unitary leptonic mixing matrix. Additionally, we also analyze the case of generic deviations from unitarity of the leptonic mixing matrix, not necessarily induced by the presence of additional neutrinos. This last case relaxes some correlations among the parameters and is able to provide a better fit to the data. Nevertheless, inducing only leptonic unitarity deviations avoiding both the correlations implied by the right-handed neutrino extension as well as more strongly constrained operators is challenging and would imply significantly more complex UV completions.

General formalism of the quantum equivalence principle

A consistent theory of quantum gravity will require a fully quantum formulation of the classical equivalence principle. Such a formulation has been recently proposed in terms of the equality of the rest, inertial and gravitational mass operators, and for non-relativistic particles in a weak gravitational field. In this work, we propose a generalization to a fully relativistic formalism of the quantum equivalence principle, valid for all background space-times, as well as for massive bosons and fermions. The principle is trivially satisfied for massless particles. We show that if the equivalence principle is broken at the quantum level, it implies the modification of the standard Lorentz transformations in flat space-time and a corresponding modification of the metric in curved space-time by the different mass ratios. In other words, the observed geometry would effectively depend on the properties of the test particle. Testable predictions of potential violations of the quantum equivalence principle are proposed.

Theoretical concepts and measurement prospects for BSM trilinear couplings: a case study for scalar top quarks

After the possible discovery of new heavy particles at the LHC, it will be crucial to determine the properties and the underlying physics of the new states. In this work, we focus on scalar trilinear couplings, employing as an example the case of the trilinear coupling of scalar partners of the top quark to the Higgs boson. We discuss possible strategies for experimentally determining the scalar top (stop) trilinear coupling parameter, which controls the stop–stop–Higgs interaction, and we demonstrate the impact of different renormalisation prescriptions for this parameter. We find that the best prospects for determining the stop trilinear coupling arise from its quantum effects entering the model prediction for the mass of the SM-like Higgs boson in comparison to the measured value. We point out that the prediction for the Higgs-boson mass has a high sensitivity to the stop trilinear coupling even for heavy masses of the non-standard particles. Regarding the renormalisation of the stop trilinear coupling we identify a renormalisation scheme that is preferred in view of the present level of accuracy and we clarify the source of potentially large logarithms that cannot be resummed with standard renormalisation group methods.

Search for long-lived particles using out-of-time trackless jets in proton-proton collisions at sqrt{s} = 13 TeV

A search for long-lived particles decaying in the outer regions of the CMS silicon tracker or in the calorimeters is presented. The search is based on a data sample of proton-proton collisions at sqrt{s} = 13 TeV recorded with the CMS detector at the LHC in 2016–2018, corresponding to an integrated luminosity of 138 fb−1. A novel technique, using nearly trackless and out-of-time jet information combined in a deep neural network discriminator, is employed to identify decays of long-lived particles. The results are interpreted in a simplified model of chargino-neutralino production, where the neutralino is the next-to-lightest supersymmetric particle, is long-lived, and decays to a gravitino and either a Higgs or Z boson. This search is most sensitive to neutralino proper decay lengths of approximately 0.5 m, for which masses up to 1.18 TeV are excluded at 95% confidence level. The current search is the best result to date in the mass range from the kinematic limit imposed by the Higgs boson mass up to 1.8 TeV.

A search for heavy Higgs bosons decaying into vector bosons in same-sign two-lepton final states in pp collisions at sqrt{s} = 13 TeV with the ATLAS detector

A search for heavy Higgs bosons produced in association with a vector boson and decaying into a pair of vector bosons is performed in final states with two leptons (electrons or muons) of the same electric charge, missing transverse momentum and jets. A data sample of proton–proton collisions at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015 and 2018 is used. The data correspond to a total integrated luminosity of 139 fb−1. The observed data are in agreement with Standard Model background expectations. The results are interpreted using higher-dimensional operators in an effective field theory. Upper limits on the production cross-section are calculated at 95% confidence level as a function of the heavy Higgs boson’s mass and coupling strengths to vector bosons. Limits are set in the Higgs boson mass range from 300 to 1500 GeV, and depend on the assumed couplings. The highest excluded mass for a heavy Higgs boson with the coupling combinations explored is 900 GeV. Limits on coupling strengths are also provided.

Search for the exotic decay of the Higgs boson into two light pseudoscalars with four photons in the final state in proton-proton collisions at sqrt{s} = 13 TeV

A search for the exotic decay of the Higgs boson to a pair of light pseudoscalars, each of which subsequently decays into a pair of photons, is presented. The search uses data from proton-proton collisions at sqrt{s} = 13 TeV recorded with the CMS detector at the LHC that corresponds to an integrated luminosity of 132 fb−1. The analysis probes pseudoscalar bosons with masses in the range 15–62 GeV, coming from the Higgs boson decay, which leads to four well-isolated photons in the final state. No significant deviation from the background-only hypothesis is observed. Upper limits are set on the product of the Higgs boson production cross section and branching fraction into four photons. The observed (expected) limits range from 0.80 (1.00) fb for a pseudoscalar boson mass of 15 GeV to 0.26 (0.24) fb for a mass of 62 GeV at 95% confidence level.

Search for dark photons from Higgs boson decays via ZH production with a photon plus missing transverse momentum signature from pp collisions at sqrt{s} = 13 TeV with the ATLAS detector

This paper describes a search for dark photons (γd) in proton-proton collisions at sqrt{s} = 13 TeV at the Large Hadron Collider (LHC). The dark photons are searched for in the decay of Higgs bosons (H → γγd) produced through the ZH production mode. The transverse mass of the system, made of the photon and the missing transverse momentum from the non-interacting γd, presents a distinctive signature as it peaks near the Higgs boson mass. The results presented use the total Run-2 integrated luminosity of 139 fb−1 recorded by the ATLAS detector at the LHC. The dominant reducible background processes are estimated using data-driven techniques. A Boosted Decision Tree technique is adopted to enhance the sensitivity of the search. As no excess is observed with respect to the Standard Model prediction, an observed (expected) upper limit on the branching ratio BR(H → γγd) of 2.28% ( {2.82}_{-0.84}^{+1.33}% ) is set at 95% CL for massless γd. For massive dark photons up to 40 GeV, the observed (expected) upper limits on BR(H → γγd) at 95% confidence level is found within the [2.19,2.52]% ([2.71,3.11]%) range.

Search for dark matter produced in association with a dark Higgs boson decaying into W+W− in the one-lepton final state at sqrt{s} = 13 TeV using 139 fb−1 of pp collisions recorded with the ATLAS detector

Several extensions of the Standard Model predict the production of dark matter particles at the LHC. A search for dark matter particles produced in association with a dark Higgs boson decaying into W+W− in the {ell}^{pm}nu q{overline{q}}^{prime }, final states with ℓ = e, μ is presented. This analysis uses 139 fb−1 of pp collisions recorded by the ATLAS detector at a centre-of-mass energy of 13 TeV. The W± → qoverline{q^{prime }} decays are reconstructed from pairs of calorimeter-measured jets or from track-assisted reclustered jets, a technique aimed at resolving the dense topology from a pair of boosted quarks using jets in the calorimeter and tracking information. The observed data are found to agree with Standard Model predictions. Scenarios with dark Higgs boson masses ranging between 140 and 390 GeV are excluded.

W boson mass and grand unification via the type-II seesaw-like mechanism

We propose an SU(5) GUT model extended with two additional pairs of 10 representation vector-like fermions. The CDF collaboration W boson mass anomaly is explained by using the VEV of a real SU(2)L triplet scalar coming from the 24 representation Higgs. The vector-like fermions are decomposed partly into vector-like quark doublets. Those vector-like quark doublets acquire mass from two sources; through the Yukawa interaction with the real SU(2)L triplet via a type-II seesaw-like mechanism. And, they acquire mass from the 24 representation Higgs. We assume that the mass for the vector-like quark doublets is expressed in terms of the real triplets mass. By combining the constraints on the vector-like quark masses with those on the heavy Higgs boson masses, we can obtain the narrow allowed mass ranges for the vector-like quark doublet and the real triplet. Therefore, our model can be tested in searches for these particles in the near future. In addition, the two additional pairs of vector-like fermions allow the SM gauge couplings to unify successfully at MGUT≈5.1×1015 GeV. Our model is also testable by the future Hyper-Kamiokande experiment via the proton decay lifetime τp(p→π0e+)<1.0×1035 years.

Custodial symmetry violation in scalar extensions of the standard model* *X.W. is supported by the Fundamental Research Funds for the Central Universities of China (GK202003018). J.-H.Y. is supported by the National Science Foundation of China (12022514, 11875003, and 12047503), the National Key Research and Development Program of China (2020YFC2201501, 2021YFA0718304), the CAS Project for Young Scientists in Basic Research (YSBR-006),

The new measurement of the W boson mass from the CDF collaboration shows a significant tension with the standard model prediction, which evidences violation of custodial symmetry in the scalar sector. We study the scalar extensions of the standard model, which can be categorized into two classes, the scalar sector with custodial symmetry (Georgi-Machacek model and its generalizations) and the scalar sector without custodial symmetry, and explore how these extensions fit to electroweak precision data and the new CDF . The favored oblique parameters originate from either the large mass splitting in the multiplet via the loop contribution or the large vacuum expectation value, which breaks custodial symmetry at the tree level. In particular, we find that GeV new particles are allowed in the scalar extension scenarios.

W boson mass in singlet-triplet scotogenic dark matter model

The recent high precision measurement of [Formula: see text] boson mass by CDF-II collaboration points to the contribution(s) of new physics beyond the Standard Model (SM). One of the minimalistic ways to account for the anomalous [Formula: see text] boson mass is by introducing a hyperchargeless real [Formula: see text] triplet scalar whose vacuum expectation value (VEV) explicitly contributes to the [Formula: see text] boson mass at the tree level while the [Formula: see text] boson mass remains the same. Such a triplet can be naturally embedded in a singlet-triplet scotogenic model for one-loop neutrino mass generated by dark sector particles running in the loop. We discuss the detailed phenomenology of the model, obtaining the parameter space consistent with the CDF-II [Formula: see text] boson mass measurements. The dark matter as well as the constraints comings from [Formula: see text], [Formula: see text], [Formula: see text] parameters are also analyzed.

Non-factorizable virtual corrections to Higgs boson production in weak boson fusion beyond the eikonal approximation

Non-factorizable virtual corrections to Higgs boson production in weak boson fusion at next-to-next-to-leading order in QCD were estimated in the eikonal approximation [1]. This approximation corresponds to the expansion of relevant amplitudes around the forward limit. In this paper we compute the leading power correction to the eikonal limit and show that it is proportional to first power of the Higgs boson transverse momentum or the Higgs boson mass over partonic center-of-mass energy. Moreover, this correction can be significantly enhanced by the rapidity of the Higgs boson. For realistic weak boson fusion cuts, the next-to-eikonal correction reduces the estimate of non-factorizable contributions to fiducial cross section by (20) percent.

The SU(2)$_{D}$ lepton portals for muon g - 2, W boson mass and dark matter

We propose a novel model which extends the Standard Model (SM) by introducing a SU(2)_DSU(2)D gauge symmetry. In this model, a dark SU(2)_DSU(2)D Higgs doublet and a Higgs bi-doublet can contribute to the muon g-2 anomaly and the WW boson mass, remaining in tune with the recent experimental results. At the same time, the isospin charged gauge boson of SU(2)_DSU(2)D becomes a plausible candidate for Dark Matter(DM). We find that the resulting parameter space can fit the muon g-2, the W boson mass and the DM constraints simultaneously.

Anomalous conductivities in the holographic Stückelberg model

We have studied a massive U(1) gauge holographic model with pure gauge and mixed gauge-gravitational Chern-Simons terms. The full backreaction of the gauge field on the metric tensor has been considered in order to explore the vortical and energy transport sector. The background solution has been computed numerically. On this background, we have considered the fluctuation of the fields and evaluated the different correlators. We have found that all the correlators depend on the mass of the gauge field. Correlators such as the current-current one, 〈JxJx〉, which were completely absent in the massless case, in the presence of a finite gauge boson mass start picking up some finite value even at zero chemical potential. Similarly, the energy-current correlator, 〈T0xJx〉, which was also absent in the massless theory, has now a non-vanishing value but for finite values of the chemical potential. Our findings for the chiral vortical conductivity, σV, and the chiral magnetic/vortical conductivity of energy current, {sigma}_B^{varepsilon }={sigma}_V^{varepsilon } , are completely new results. In addition to this, we have found that these anomalous transport coefficients depend linearly both on the pure Chern-Simon coupling, κ, and on the mixed gauge-gravity Chern-Simon coupling, λ. One of the results that we would like to highlight is that it’s not just κ that contributes to the σB but there is an additional contribution from λ as well unlike the previous studies.

CDF-II W-boson mass anomaly in the canonical Scotogenic neutrino–dark matter model

The CDF-II collaboration’s recent high-precision measurement of [Formula: see text]-boson mass indicates new physics contribution(s) beyond the Standard Model. We investigate the possibility of the well-known canonical Scotogenic model to explain the CDF-II measurement. The Scotogenic model is a popular scenario beyond the Standard Model that induces neutrino masses at the one-loop level and includes a viable dark matter candidate, either scalar or fermionic. For both scalar and fermionic dark matter possibilities, we simultaneously examine the constraints coming from (a) neutrino mass, oscillation, neutrinoless double beta decay and lepton flavor violation experiments, (b) from LEP and LHC, (c) from dark matter relic density and direct detection experiments, (d) from the oblique [Formula: see text] parameter values consistent with CDF-II [Formula: see text]-boson measurement. We demonstrate that the new CDF-II measurement rules out the feasible parameter space of the scalar dark matter in the high mass regions ([Formula: see text]), while still allowing the intermediate mass regions [Formula: see text]. We also showed that the fermionic dark matter candidate in the canonical Scotogenic model, in the range [Formula: see text], can simultaneously explain all the aforementioned issues. Furthermore, we investigated how the recent findings from ATLAS 2023 impact this study.