Initial Beam Polarization Research Articles

Study of anomalous W-W+γ/Z\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$W^-W^+\\gamma /Z$$\\end{document} couplings using polarizations and spin correlations in e-e+→W-W+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$e^-e^+\\rightarrow W^-W^+$$\\end{document} with polarized beams

We investigate the anomalous W-W+γ/Z\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$W^-W^+\\gamma /Z$$\\end{document} couplings in e-e+→W-W+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$e^-e^+\\rightarrow W^-W^+$$\\end{document} followed by semileptonic decay using a complete set of polarization and spin correlation observables of W boson with the longitudinally polarized beam. We consider a complete set of dimension-six operators affecting W-W+γ/Z\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$W^-W^+\\gamma /Z$$\\end{document} vertex, which are SU(2)×U(1)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$SU(2)\ imes U(1)$$\\end{document} gauge invariant. Some of the polarization and spin correlation asymmetries average out if the daughter of W+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$W^+$$\\end{document} is not tagged and to overcome this we developed an artificial neural network and boosted decision trees to distinguish down-type jets from up-type jets. We obtain bounds on the anomalous couplings using MCMC analysis at s=250\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{s} = 250$$\\end{document} GeV with integrated luminosities of L∈{100fb-1,250fb-1,1000fb-1,3000fb-1}\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal {L}\\in \\{100~\ ext {fb}^{-1}, 250~\ ext {fb}^{-1}, 1000~\ ext {fb}^{-1}, 3000~\ ext {fb}^{-1}\\}$$\\end{document} and different sets of systematic errors. We find that using spin-related observables along with cross section in the presence of initial beam polarization significantly improves the bounds on anomalous couplings compared to previous studies.

The Influence of the Scalar and Vector Anomalous Couplings on the Z-production at ILC in the Randall - Sundrum Model

An attempt is made to present the effect of the scalar and vector anomalous couplings on scattering process with polarized initial beams in the Randall-Sundrum model. We have studied the contribution of radion, Higgs and gauge bosons on the Z-production cross-section at International Linear Colliders (ILC). The cross-section depends strongly on the polarization of initial beams, the center of mass energy and model interaction parameters. The obtained results indicate that with the vector anomalous couplings included Z boson and photon, the cross-sections for the Z production are much larger than that with the scalar couplings included radion and Higgs under the same conditions.

One-loop formulas for off-shell decay \(H^* \rightarrow W^+W^-\) in 't Hooft-Veltman gauge and its applications

We present analytic results for one-loop radiative corrections to off-shell decay \(H^* \rightarrow W^+W^-\) in 't Hooft-Veltman gauge within the Standard Model framework. In numerical results, we show off-shell decay rate and its corrections with varying off-shell Higgs mass. The results show that the corrections are of 10% contributions to the total decay rates. Furthermore, we study the impacts of one-loop radiative corrections to the off-shell decay \(H^* \rightarrow W^+W^-\) in Higgs processes at future colliders. The signal processes such as \(e^-e^+\rightarrow ZH^*\rightarrow Z(WW)\) with including the initial beam polarizations and \(e^-e^+\rightarrow \nu_e\bar{\nu}_e H^* \rightarrow \nu_e\bar{\nu}_e (WW)\) and \(e^-\gamma \rightarrow e^-H^* \rightarrow e^-WW\) are examined. We find that the effects are visible impacts and these should be taken into account at future colliders.

Study of the projected sensitivity on the anomalous quartic gauge couplings via Zγγ production at the CLIC

Gauge boson self-couplings are completely defined by the non-Abelian gauge symmetry of the Standard Model (SM). For this reason, a direct search for these couplings is extremely significant in understanding the gauge structure of the SM. The possible deviation from the SM predictions of gauge boson self-couplings would be a sign of the presence of new physics beyond the SM. In this work, we study the sensitivities on the anomalous couplings defined by dimension-8 operators related to the $ZZ\gamma\gamma$ and $Z\gamma\gamma\gamma$ quartic vertices through the process $e^+e^- \to Z\gamma\gamma$ with Z-boson decaying to charged leptons at the Compact Linear Collider (CLIC). We analyze the center-of-mass energy of 3 TeV, integrated luminosities of ${\cal L}=1, 4, 5$ $\rm ab^{-1}$, systematic uncertainties of $\delta_{sys}=0\%, 3\%, 5\%$, unpolarized and polarized electron beams and considering the Initial State Radiation and Beamstrahlung effects for extraction of expected sensitivity on the anomalous $f_ {T,j}/\Lambda^4$ couplings at $95\%$ confidence level, which are especially sensitive to the $Z\gamma\gamma$ channel. It is clear from the results that we expect better limits on the couplings if the systematic error is improved. The best limits obtained on the anomalous quartic couplings for the process $e^+e^- \to Z\gamma\gamma$ with $\sqrt{s}= 3$ TeV, ${\cal L}=5$ $\rm ab^{-1}$, and $\delta_{sys}=0\%$ can be approximately improved up to about 1.1 times better than the limits obtained with $\delta_{sys}=5\%$. Our sensitivities on the anomalous quartic couplings can set more stringent sensitivity by two orders of magnitude concerning the best sensitivity derived from the current experimental limits. Finally, with initial electron beam polarization, the sensitivity of the anomalous quartic couplings improves by almost a factor of 1.2.

One-loop formulas for H → Zν l ν l for l = e, µ, τ in 't Hooft-Veltman gauge* *This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under the grant number (103.01-2019.346)

In this paper, we present analytical results for one-loop contributions to the decay processes (for ). The calculations are performed within the Standard Model framework in the 't Hooft-Veltman gauge. One-loop form factors are then written in terms of scalar one-loop functions in the standard notations of . As a result, one-loop decay rates for the decay channels can be evaluated numerically by using the package. Furthermore, we analyze the signals of via the production processes , including the initial beam polarizations at future lepton colliders. The Standard Model backgrounds, such as the processes , are also examined in this study. Numerical results indicate that one-loop corrections make contributions of approximately 10% to the decay rates. These are sizeable contributions and should be taken into account at future colliders. We show that the signals are clearly visible at the center-of-mass energy GeV and are difficult to probe in higher-energy regions owing to the dominant backgrounds.

Beam polarization effects on Z -boson pair production at electron-positron colliders: A full one-loop analysis

We present high-precision predictions for Z boson-pair production via electron-positron collisions by taking into account a full set of one-loop order scattering amplitudes, i.e., electroweak (EW) corrections together with soft and hard QED radiation. We provide a detailed numerical evaluation, from full EW corrections to pure QED corrections, specifically focusing on the effect of initial beam polarization on the production rate. The left-right asymmetry and angular distributions are also presented. The radiative corrections are largely affected by initial beam polarizations. We get an improvement of around three times with completely polarized beams of ${e}_{L}^{\ensuremath{-}}$ and ${e}_{R}^{+}$. We find that the radiative corrections can sizably modify the production rate, typically yielding a total relative correction up to a few tens of a percent. This implies that the full EW corrections are required for ${e}^{\ensuremath{-}}{e}^{+}\ensuremath{\rightarrow}ZZ$ to match with percent-level accuracy.

E + e − γ production at photon-photon colliders at complete electroweak NLO accuracy * *Supported in part by the National Natural Science Foundation of China (11775211, 12061141005) and the CAS Center for Excellence in Particle Physics (CCEPP)

We present the NLO electroweak radiative corrections to the production in γγ collision, which is an ideal channel for calibrating the beam luminosity of a Photon Linear Collider. We analyze the dependence of the total cross section on the beam colliding energy, and then investigate the kinematic distributions of final particles at various initial photon beam polarizations at EW NLO accuracy. The numerical results indicate that the EW relative corrections to the total cross section are non-negligible and become increasingly significant as the increase of the beam colliding energy, even can exceed –10% in the γγ collision at . Such EW corrections are very important and should be taken into consideration in precision theoretical and experimental studies at high-energy γγ colliders.

One-loop electroweak radiative corrections to charged lepton pair production in photon-photon collisions

We provide high-precision predictions for muon-pair and tau-pair productions in a photon-photon collision by considering a complete set of one-loop-level scattering amplitudes, i.e., electroweak (EW) corrections together with soft and hard QED radiation. Accordingly, we present a detailed numerical discussion with particular emphasis on the pure QED corrections as well as genuinely weak corrections. The effects of angular and initial beam polarization distributions on production rates are also discussed. An improvement is observed by a factor of two with oppositely polarized photons. Our results indicate that the one-loop EW radiative corrections enhance the Born cross section and the total relative correction is typically about 10% for both production channels. It appears that the full EW corrections to $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}$ are required to match a percent level accuracy.

One-loop electroweak radiative corrections to lepton pair production in polarized electron-positron collisions

This paper presents the high-precision theoretical predictions for $e^+e^- \to l^-l^+$ scattering. Calculations are performed using the {\tt SANC} system. They take into account complete one-loop electroweak radiative corrections as well as longitudinal polarization of initial beams. Reaction observables are obtained using the helicity amplitude method with taking into account initial and final state fermion masses. Numerical results are given for the center-of-mass energy range $\sqrt{s}=250-1000$ GeV with various degrees of polarization.

Full \(\mathcal{O}(\alpha)\) Electroweak Radiative Corrections to \(e^-e^+ \rightarrow W^-W^+\) with Initial Beam Polarization Effects

We calculate full \(\mathcal{O}(\alpha)\) electroweak radiative corrections and \(\mathcal{O}(\alpha^3)\) initial state radiation (ISR) corrections to \(e^-e^+ \rightarrow W^-W^+\) with initial beam polarization effects. In phenomenological results, we study the impact of electroweak and ISR corrections on cross-sections as well as their relevant distributions. We find that the corrections are order of 10% contributions. They are sizable contributions and should be taken into account at future lepton colliders.

One-loop electroweak radiative corrections to polarized e+e−→ZH

In this paper we give high-precision theoretical predictions for cross sections of the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}ZH$ for future electron-positron colliders. The calculations are performed using the sanc system. They include complete one-loop electroweak radiative corrections, as well as the longitudinal polarization of initial beams. Numerical results are given for the center-of-mass energy range $\sqrt{s}=250--1000\text{ }\text{ }\mathrm{GeV}$ with various polarization degrees.

Full . Full O(α) electroweak radiative corrections to e^+ e^-→ZH with beam polarizations at the ILCO(α) electroweak radiative corrections to e^+ e^-→ZH with beam polarizations at the ILC

We present full electroweak radiative corrections to with the initial beam polarizations at the International Linear Collider (ILC). The calculation is checked numerically by using three consistency tests that are ultraviolet finiteness, infrared finiteness, and gauge parameter independence. In phenomenological results, we study the impact of the electroweak corrections to total cross section as well as its distributions. In addition, we discuss the possibility of searching for an additional Higgs in arbitrary beyond the Standard Model (BSM) through ZH production at the ILC.

Final taus and initial state polarization signatures from effective interactions of Majorana neutrinos at future e^{+}e^{-} colliders

We study the possibility of future e^{+}e^{-} colliders to disentangle different new physics contributions to the production of heavy sterile Majorana neutrinos in the lepton number violating channel e^{+}e^{-}rightarrow l^{+} l^{+}+ 4 {text {jets}}, with l=e, mu , tau . This is done investigating the final anti-tau polarization trails and initial beam polarization dependence of the signal on effective operators with distinct Dirac–Lorentz structure contributing to the Majorana neutrino production and decay, which parameterize new physics from a higher energy scale. We find that both analyses could well disentangle possible vectorial and scalar operators contributions.

Exploring the top-Higgs FCNC couplings at polarized linear colliders with top spin observables

We study the nature of flavor changing neutral couplings of the top quark with the Higgs boson and the up/charm quark in the toverline{t} production at linear colliders. There are previous bounds on such tqH couplings at both, linear and hadronic colliders, with the assumption that the top couples equally to the left and the right handed fermions. In this paper we examine chirality of the tqH coupling and construct different observables which will be sensitive to it. The kinematics of the emitted q from t → qH in toverline{t} production is discussed and it was found that the polar angle distribution of q is sensitive to the chiral nature of tqH couplings. The observables in the context of top-antitop spin correlations, which are sensitive to new physics in the top decay are considered using different spin-quantization bases. It was found that in particular the off-diagonal basis can be useful to distinguish among the chiral tqH couplings. The sensitivity of the unpolarized ILC in probing the couplings at the 3σ level at sqrt{s}=500 GeV and ℒ = 500 fb−1 is also studied, resulting in predicted BR(t → qH) < 1.19 × 10−3. This limit is further improved to BR(t → qH) < 8.84 × 10−4 with the inclusion of initial beam polarization of left handed electrons and right handed positrons.

Muon polarization in the MEG experiment: predictions and measurements

The MEG experiment makes use of one of the world's most intense low energy muon beams, in order to search for the lepton flavour violating process $\mu^{+} \rightarrow {\rm e}^{+} \gamma$. We determined the residual beam polarization at the thin stopping target, by measuring the asymmetry of the angular distribution of Michel decay positrons as a function of energy. The initial muon beam polarization at the production is predicted to be $P_{\mu} = -1$ by the Standard Model (SM) with massless neutrinos. We estimated our residual muon polarization to be $P_{\mu} = -0.85 \pm 0.03 ~ {\rm (stat)} ~ { }^{+ 0.04}_{-0.05} ~ {\rm (syst)}$ at the stopping target, which is consistent with the SM predictions when the depolarizing effects occurring during the muon production, propagation and moderation in the target are taken into account. The knowledge of beam polarization is of fundamental importance in order to model the background of our ${\megsign}$ search induced by the muon radiative decay: $\mu^{+} \rightarrow {\rm e}^{+} \bar{\nu}_{\mu} \nu_{\rm e} \gamma$.

The Production of Ξbb at the Photon Collider

The inclusive production of the doubly heavy baryon Ξbb is investigated with a polarized and unpolarized photon collider. The bb pair in both a color triplet and sextet has been considered to transform into Ξbb. The results indicate that the contribution from the color sextet is about 8% for Ξbb production. For the international linear collider collision energy ranging from 91 GeV to 1000 GeV, the total cross section of Ξbb shows a downtrend, i.e., the production of Ξbb has the maximal rate at √S = 91 GeV. Our results indicate that the initial beam polarization may be an important asset for the production of Ξbb. At some collision point, the production rate of Ξbb can be increased by about 17% with an appropriate choice of the initial beam polarization.

Connection between beam polarization and systematical errors in storage ring electric-dipole-moment experiments

Analysis of spin dynamics in storage ring electric-dipole-moment (EDM) experiments ascertains that the use of initial vertical beam polarization allows the cancellation of spin-dependent systematical errors imitating the EDM effect. While the use of this polarization meets certain difficulties, it should be considered as an alternative or supplementary possibility of fulfilling the EDM experiment.

IsolatingCP-violatingγZZcoupling ine+e−→γZwith transverse beam polarizations

We revisit the process $e^+e^- \to \gamma Z$ at the ILC with transverse beam polarization in the presence of anomalous CP-violating $\gamma Z Z$ coupling $\lambda_1$ and $\gamma \gamma Z$ coupling $\lambda_2$. We point out that if the final-state spins are resolved, then it becomes possible to fingerprint the anomalous coupling {\rm Re}$\lambda_1$.90% confidence level limit on {\rm Re}$\lambda_1$ achievable at ILC with center-of-mass energy of 500 GeV or 800 GeV with realistic initial beam polarization and integrated luminosity is of the order of few times of $10^{-2}$ when the helicity of $Z$ is used and $10^{-3}$ when the helicity of $\gamma$ is used. The resulting corrections at quadratic order to the cross section and its influence on these limits are also evaluated and are shown to be small. The benefits of such polarization programmes at the ILC are compared and contrasted for the process at hand. We also discuss possible methods by which one can isolate events with a definite helicity for one of the final-state particles.

Anomalous triple gauge boson couplings in [formula omitted] for noncommutative standard model

We investigate e+e−→γγ process within the Seiberg–Witten expanded noncommutative standard model (NCSM) scenario in the presence of anomalous triple gauge boson couplings. This study is done with and without initial beam polarization and we restrict ourselves to leading order effects of noncommutativity i.e. O(Θ). The noncommutative (NC) corrections are sensitive to the electric component (Θ→E) of NC parameter. We include the effects of Earthʼs rotation in our analysis. This study is done by investigating the effects of noncommutativity on different time averaged cross section observables. We have also defined forward backward asymmetries which will be exclusively sensitive to anomalous couplings. We have looked into the sensitivity of these couplings at future experiments at the International Linear Collider (ILC). This analysis is done under realistic ILC conditions with the center of mass energy (c.m.) s=800 GeV and integrated luminosity L=500 fb−1. The scale of noncommutativity is assumed to be Λ=1 TeV. The limits on anomalous couplings of the order 10−1 from forward backward asymmetries while much stringent limits of the order 10−2 from total cross section are obtained if no signal beyond SM is seen.

Role of polarization in probing anomalous gauge interactions of the Higgs boson

We explore the use of polarized e(+)/e(-) beams and/or the information on final state decay lepton polarizations in probing the interaction of the Higgs boson with a pair of vector bosons. A model independent analysis of the process e(+)e(-) -> f (f) over barH, where f is any light fermion, is carried out through the construction of observables having identical properties under the discrete symmetry transformations as different individual anomalous interactions. This allows us to probe an individual anomalous term independent of the others. We find that initial state beam polarization can significantly improve the sensitivity to CP-odd couplings of the Z boson with the Higgs boson (ZZH). Moreover, an ability to isolate events with a particular tau helicity, with even 40% efficiency, can improve sensitivities to certain ZZH couplings by as much as a factor of 3. In addition, the contamination from the ZZH vertex contributions present in the measurement of the trilinear Higgs-W (WWH) couplings can be reduced to a great extent by employing polarized beams. The effects of initial state radiation and beamstrahlung, which can be relevant for higher values of the beam energy are also included in the analysis.