One-loop electroweak corrections to e+e- into three-jets
C. M. Carloni Calame, S. Moretti, F. Piccinini, D. A. Ross
备注：
contribution to the proceedings of the 8th International Symposium on Radiative Corrections (RADCOR 2007): Application of Quantum Field Theory to Phenomenology, Florence, Italy, 1-6 Oct 2007. v2: references updated
We describe the impact of the full one-loop Electro-Weak terms of O($α_sα^3_{EM}$) entering the electron-positron into three-jet cross-section. We include both factorisable and non-factorisable virtual corrections, photon bremsstrahlung but not the real emission of $W^\pm$ and $Z$ bosons. We show preliminary results and we discuss the impact of the Electro-Weak corrections on three-jet observables.
We present an implementation of the full electroweak $H+2~\text{jets}$ production process at hadron colliders in the framework of the $\tt{POWHEG~BOX}$, a public tool for the matching of fixed-order perturbative calculations with parton shower generators. Our implementation allows for the simultaneous description of vector-boson fusion and Higgsstrahlung contributions. NLO-QCD and electroweak corrections are taken into account and matched to QCD and QED showers, respectively. The size of the fixed-order QCD and electroweak corrections is found to be moderate, but dependent on the considered se…
We present results for the electroweak radiative corrections to the production of a leptonically decaying Z boson in association with two jets at the LHC. Tree-level and one-loop amplitudes have been obtained with the computer code Recola for the recursive generation of tree-level and one-loop amplitudes in the Standard Model. The one-loop integrals have been calculated with the tensor-integral library Collier. The electroweak corrections turn out to be small for inclusive cross sections but can become large in tails of distributions.
We calculate the next-to-leading order electroweak corrections to the production of a photon pair in association with zero, one and two jets at the LHC. We use GoSam and Sherpa to obtain the results in a fully automated way. For a typical set of fiducial cuts the electroweak corrections lead to a modification of the total cross section of up to 3 per cent, depending on the jet multiplicity. We find substantial contributions in differential distributions, leading to tens of per cent corrections for phase space regions within the reach of the LHC. Furthermore we investigate the importance of pho…
If studies of electroweak gauge boson final states at the Large Hadron Collider, for Standard Model physics and beyond, are sensitive to effects of the initial state's transverse momentum distribution, appropriate generalizations of QCD shower evolution are required. We propose a method to do this based on QCD transverse momentum dependent (TMD) factorization at high energy. The method incorporates experimental information from the high-precision deep inelastic scattering (DIS) measurements, and includes experimental and theoretical uncertainties on TMD parton density functions. We illustrate …
In the Standard Model the process $q\bar{q}\rightarrow q\bar{q}V$ (where $V=W^\pm,Z^0$ or $γ$) can occur via gluon exchange and also via $W^\pm$ or $Z^0$ exchange. The corresponding chromodynamic and electroweak amplitudes can interfere with one another. These interference cross sections are largest when the exchanged $W^\pm$ or $Z^0$ is on-shell when they are also odd under parity. Interference cross sections computed using helicity-amplitude techniques are presented for all interesting subprocesses as well as for the processes $q\bar{q}\rightarrow q\bar{q} l\bar{l}$ in which the lepton pair …
We describe the impact of the full one-loop electroweak terms of O(alpha_s alpha_EM^3) entering the electron-positron into three-jet cross-section from sqrt(s)=M_Z to TeV scale energies. We include both factorisable and non-factorisable virtual corrections and photon bremsstrahlung. Their importance for the measurement of alpha_S from jet rates and shape variables is explained qualitatively and illustrated quantitatively, also in presence of b-tagging.
We present the matching of the next-to-leading order QCD calculation for W+W+jj production via vector-boson fusion in hadronic collisions to parton-shower Monte-Carlo programs according to the POWHEG method. Our implementation complements existing code for QCD-induced W+W+jj production in the POWHEGBOX package, thereby providing a platform for the complete Standard Model production of W+W+jj events via QCD and electroweak interactions. The impact of parton-shower effects is discussed for various distributions and found to be small in most cases. However, few observables, that are relevant for …
A complete parton level analysis of lv + four jets production at the LHC is presented, including all processes at order O(alpha^6), O(alpha^4*alpha_s^2) and O(alpha^2*alpha_s^4). The infinite Higgs mass scenario, which is considered as a benchmark for strong scattering theories and is the limiting case for composite Higgs models, is confronted with the Standard Model light Higgs predictions in order to determine whether a composite Higgs signal can be detected as an excess of events in boson--boson scattering.
We compute the next-to-leading order corrections of $O(α_s^2α^3)$ to the hadronic production of two oppositely charged leptons and two hard jets, $p p \to j j l^- l^+$, using Recola and Collier. We include electroweak and QCD corrections at the given order and all off-shell effects. We provide detailed predictions for the LHC operating at 13 TeV and obtain per-cent-level corrections for the total cross section. For differential distributions we find significant non-uniform distortions in high-energy tails at the level of several ten per cent due to electroweak Sudakov logarithms and deformatio…
We calculate the fiducial and differential $W^{\pm}/Z^0+jet(s)$ production cross-sections in the presence of electroweak (EW) corrections through virtual loop contributions to the matrix elements (MEs) of the processes and real partonic cascade emissions. The calculations are carried out for proton-proton collisions at $\sqrt{s} = 13$ TeV, using Herwig 7 general-purpose Monte-Carlo event generator with leading-order or next-to-leading-order MEs that are interfaced with different parton-shower configurations. The results are compared with precision experimental measurements from ATLAS collabora…
If inflaton couples very weakly to ordinary matter the reheating temperature of the universe can be lower than the electroweak scale. In this letter we show that the late reheating occurs in a highly non-uniform way, within narrow areas along the jets produced by ordinary particles originated from inflaton decays. Depending on inflaton mass and decay constant, the initial temperature inside the lumps of the overheated plasma may be large enough to trigger the unsuppressed sphaleron processes with baryon number non-conservation, allowing for efficient local electroweak baryogenesis.
For energies far above the electroweak scale, large electroweak radiative corrections occur that grow logarithmically with energy and can easily reach several tens of per cent in the TeV range. Recent work on these corrections is reviewed.
The production of both charged and neutral electroweak gauge bosons in association with $b$ jets has attracted a lot of experimental and theoretical attention in recent years because of its central role in the physics programs of both the Fermilab Tevatron and the CERN Large Hadron Collider. The improved level of accuracy achieved both in the theoretical predictions and experimental measurements of these processes can promote crucial developments in modeling $b$-quark jets and $b$-quark parton distribution functions, and can provide a more accurate description of some of the most important bac…
In this proceeding, we highlight the computation of leading fermionic three-loop corrections to electroweak precision observables (EWPOs) accomplished recently. We summarize the numerical analysis and provide an outlook.
The recent calculation of the next-to-leading order electroweak corrections to the decay of the Standard Model Higgs boson to two photons in the framework of the complex-mass scheme is briefly summarized.
At energies much larger than the mass of the weak gauge bosons, electroweak radiative corrections can lead to significant corrections. At 1 TeV the one loop corrections can be of ${\cal O} (20 %)$ due to large contributions of the Sudakov type. We summarize recent progress in the evaluation and resummation of the double and single logarithmic corrections to general scattering amplitudes for fermions, transversely as well as longitudinally polarized external lines.
Theoretical uncertainties affecting electroweak observables are reviewed and the relevance of two-loop electroweak radiative corrections for the precision tests of the Standard Model is discussed.
This note presents a study of matching and merging schemes and weak showering at the LHC as applied to the production of electroweak bosons in association with jets. These advanced theoretical tools are seen to provide a good description of event shapes in the central region when compared to measurements performed by the ATLAS and CMS collaborations at a centre-of-mass energy of 7 TeV. Matching and merging schemes also provide a superior description of forward $Z+$jets production. The study constitutes a test of matching and merging schemes in a novel region of phase space and can be considere…
The two-loop electroweak bosonic correction to the muon lifetime is computed using methods of asymptotic expansion. Combined with previous calculations this completes the full two-loop correction to $Δr$ in the Standard Model.
We have calculated the $O(α_{ew} M_t^2/M_W^2)$ supersymmetric electroweak corrections to single top quark production via $q\bar q' \to t\bar b$ at the Fermilab Tevatron in the minimal supersymmetric model. The supersymmetric electroweak corrections to the cross section are a few percent for $tan β> 1$, and can exceed 10% for $tanβ<1$. The combined effects of SUSY electroweak corrections and the Yukawa corrections can exceed 10% for favorable parameter values, which might be observable at a high-luminosity Tevatron.
In the QCD context, the non-singlet structure functions of u and d -quarks are identical, save the initial quark densities. Electroweak radiative corrections, being flavor-dependent, bring further difference between the non-singlets. This difference is calculated in the double-logarithmic approximation and the impact of the electroweak corrections on the non-singlet intercepts is estimated numerically.
We have studied the effect of one-loop logarithmic electroweak radiative corrections on WZ and $Wγ$ production processes at the LHC. We present analytical results for the leading-logarithmic electroweak corrections to the corresponding partonic processes du -> WZ, Wgamma. Using the leading-pole approximation we implement these corrections into Monte Carlo programs for $pp\to lν_l l'\bar l', lν_lγ$. We find that electroweak corrections lower the predictions by 5-20% in the physically interesting region of large transverse momentum and small rapidity separation of the gauge bosons.
The $αm_t^2/m_W^2$ order supersymmetric electroweak corrections arising from loops of chargino, neutralino, and squark to top quark pair production by $gg$ fusion at LHC are calculated in the minimal supersymmetric model. We found that the corrections amount about a few percent.
We present a calculation of the complete electroweak O(alpha) corrections to pp/ppbar -> W+/- -> l+/- nu (l=e, mu) in the Standard Model of electroweak interactions, focusing on those corrections which do not contribute in the pole approximation. We study in detail the effect of these corrections on the transverse mass distribution, the W-width measurement, and the transverse mass ratio and cross section ratio of W and Z bosons.
We present an analysis of two-loop mixed QCD and electroweak corrections to the decay of the Z boson into light quarks. We find that the naive factorization of QCD and electroweak corrections does not describe correctly the two-loop effects. The nonfactorizable corrections shift the width of the Z boson by approximately -0.55(3) MeV and increase the central value of the strong coupling constant determined at LEP by 0.001.
The analysis of the newest data on the leptonic $Z$-decays and $m_W$ appears to reveal the first manifestations of electroweak radiative corrections. In fact, these data differ, at the level of $2σ$, from their electroweak Born values, while they agree, to within $1σ$, with the theoretical values which take the electroweak radiative corrections into account. Previous data were within $1σ$ in agreement with both sets of values.
This paper studies models with extended electroweak gauge sectors of the form SU(2) x SU(2) x U(1) x [SU(2) or U(1)]. We establish the general behavior of corrections to precision electroweak observables in this class of theories and connect our results to previous work on specific models whose electroweak sectors are special cases of our extended group.
We reemphasize the importance of discriminating fermion-loop and bosonic electroweak corrections in the analysis of electroweak precision data. Most recent data are indeed precise enough to require corrections beyond (trivial) fermion loops. An analysis of these data in terms of the observables $Δx \equiv ε_{N1} - ε_{N2}$, $Δy \equiv - ε_{N2}$ and $ε\equiv - ε_{N3}$ identifies the required additional corrections as vertex corrections at the $W^\pm f\bar f^\prime$ and $Z^0 f\bar f$ vertices. Standard-model values for these corrections are consistent with the experimental data.
We consider some of the recent proposals in which weak-scale dark matter is accompanied by a GeV scale dark sector that could produce spectacular lepton-rich events at the LHC. Since much of the collider phenomenology is only weakly model dependent it is possible to arrive at generic predictions for the discovery potential of future experimental searches. We concentrate on the production of dark states through $Z^0$ bosons and electroweak-inos at the Tevatron or LHC, which are the cleanest channels for probing the dark sector. We properly take into account the effects of dark radiation and dar…
We present strong indirect evidence for the contribution of bosonic electroweak corrections in the Standard Model. Although important conceptually, these corrections give subleading contributions in current high energy experiments, and it was previously thought that they are difficult to detect. We also discuss the separate contribution of the Higgs boson.
We discuss the full electroweak one-loop corrections to the decay of the pseudoscalar Higgs boson A^0 into two sfermions within the Minimal Supersymmetric Standard Model. In particular, we consider the sfermions of the third generation, stops, sbottoms, and staus, including the left-right mixing. The electroweak corrections can go up to ~15% and can therefore not be neglected.
Reaching the desired precision level for W and Z processes at the LHC will require a mixture of higher-order QCD and electroweak corrections. HERWIRI2 is a step in implementing QED x QCD exponentiation in a hadronic event generator. This program implements leading electroweak corrections and coherent exclusive exponentiation in a HERWIG environment. We discuss the status of the program, recent tests, and future developments.
The processes of the single W-production in hadron-hadron collisions are suggested for investigation of the nucleon spin. An approach is proposed for the determination of quark spin densities at low x. The lowest order electroweak radiative corrections to the observable quantities are calculated. The numerical calculations of the cross sections and the single spin asymmetries taking into consideration the electroweak corrections at RHIC energies have been made.
We present the full O(alpha) electroweak radiative corrections to 9 Higgs boson production with the beam polarization at the International Linear Collider(ILC). The computation is performed with the help of GRACE-Loop. We compared the full O(alpha) electroweak radiative corrections with the factorized initial state radiation(ISR) effects to estimate the pure weak corrections. This reveals the pure weak corrections are not negligible and should be taken into account for the precision measurements of the Higgs boson property at the ILC experiments.
The Born approximation, based on $\barα\equivα(m_Z)$ instead of $α$, reproduces all electroweak precision measurements within their $(1σ)$ accuracy. The low upper limits for the genuinely electroweak corrections constitute one of the major achievements of LEP. The astonishing smallness of these corrections results from the cancellation of a large positive contribution from the heavy top quark and large negative contributions from all other virtual particles. It is precisely the non-observation of electroweak radiative corrections that places stringent upper and lower limits on the top mass.
We calculate the leading-logarithmic and next-to-leading-logarithmic electroweak corrections to the charm-top-quark contribution to the effective $|ΔS| = 2$ Lagrangian, relevant for the parameter $ε_K$. We find that these corrections lead to a $-0.5\%$ shift in the corresponding Wilson coefficient. Moreover, our calculation removes an implicit ambiguity in the standard-model prediction of $ε_K$, by fixing the renormalization scheme of the electroweak input parameters.
Electroweak one-loop radiative corrections to the process e^+ e^- -> t tbar are revisited. Two groups from Karlsruhe and Bielefeld/Zeuthen performed independent calculations of both (virtual and soft) QED contributions and weak virtual corrections. For the angular distribution an agreement of at least eight digits for the weak corrections and of at least seven digits for additional photonic corrections is established.
We consider the effect of next-to-leading order (NLO) electroweak corrections to Standard Model 2-to-2 processes, taking into account the potentially large double logarithms originating from both real and virtual corrections. A study of the leading Sudakov logarithms is presented and Bloch-Nordsieck (BN) violations are discussed for processes at the CERN Large Hadron Collider. In particular, we focus on the processes Z/photon+jet and also the ratio of Z to photon production. This ratio is known to be insensitive to NLO QCD corrections but this is not expected to be the case for the electroweak…
We compute the two-loop electroweak corrections due to the top quark to the gluon fusion production cross section of an intermediate-mass Higgs boson. This result, together with the previously known contribution due to the light fermions, allows a complete determination of the two-loop electroweak corrections to this production cross section. For Higgs mass values above 120 GeV the top corrections have opposite sign of the light fermions contribution, however they are always smaller in size reaching at most 15% of the latter. The total electroweak corrections to the gluon fusion production cro…
In processes at the energy much higher than electroweak scale, weak boson mass act as the infrared cutoff in weak boson loops and resulting Sudakov log corrections can be as large as 10%. Since electroweak theory is off-diagonally broken gauge theory, its IR structure is quite different from that of QCD. We briefly review recent developments on electroweak Sudakov and discuss on the exponentiation of Sudakov double logs and explicit 2 loop calculations in Feynman gauge.
The test of the electroweak corrections has played a major role in providing evidence for the gauge and the Higgs sectors of the Standard Model. At the same time the consideration of the electroweak corrections has given significant indirect information on the masses of the top and the Higgs boson before their discoveries and important orientation/constraints on the searches for new physics, still highly valuable in the present situation.The progression of these contributions is reviewed.
The phenomenological evidence for electroweak corrections in the Standard Model, both at very low energies and the $Z^0$ scale, is discussed. In particular, we review a simple but sharp argument for the presence of Electroweak Bosonic Corrections.
We present some results of a new calculation of the O(alpha) electroweak radiative corrections to W boson production at hadron colliders with special emphasis on the transverse mass distribution.
A precise theoretical description of W- and Z-boson production in the resonance region is essential for the correct interpretation of high-precision measurements of the W-boson mass and the effective weak mixing angle. Currently, the largest unknown fixed-order contribution is given by the mixed QCD-electroweak corrections of $\mathcal{O}(α_sα)$. We argue, using the framework of the pole expansion for the NNLO QCD-electroweak corrections established in a previous paper, that the numerically dominant corrections arise from the combination of large QCD corrections to the production with the larg…
It has recently been established that hadronisation corrections to QCD jets vary as $1/R$, at small $R$, for jets of radius $R$. Here we demonstrate, using jets in the $k_t$ algorithm, that the magnitude of these $1/R$ corrections are unambiguously linked to the magnitude of $1/Q$ corrections to commonly studied event shapes in $e^{+}e^{-}$ annihilation.
We calculate the leading electroweak corrections to the light neutral Higgs boson production via $q\bar q'\to WH$ at the Fermilab Tevatron in both the standard model and the minimal supersymmetric model, which arise from the top-quark and Higgs boson loop diagrams. We found that the leading electroweak corrections can exceed the QCD corrections for favorable values of the parameters in the MSSM, but such corrections are only about $-1% \sim -2%$ in the SM, which are much smaller than the QCD corrections. For the mass region of $90 < m_{h_0} < 120$ GeV, the leading electroweak corrections can r…
Future lepton colliders will provide a powerful tool for making precision experiments at energies that will range typically between 500 GeV and 2 TeV. At such high energies, one loop electroweak corrections are bigger than one could naively expect a priori. Thus, the calculation of higher order electroweak effects (and possibly their resummation) might be needed.
We compute the two-loop electroweak correction to the production of the Higgs boson in gluon fusion to higher orders in the dimensional-regularization parameter $ε= (d-4)/2$. We employ the method of differential equations to compute the relevant integrals and express them in terms of Goncharov polylogarithms. Our result provides one of the necessary inputs for the computation of mixed three-loop QCD-electroweak corrections to $gg \to H$.
Next-to-leading order electroweak and QCD radiative corrections to the Drell-Yan process with high dimuon masses for experiments CMS LHC at CERN have been studied in fully differential form. The FORTRAN code READY for numerical analysis of Drell-Yan observables has been presented. The radiative corrections are found to become significant for CMS LHC experiment setup.
I present applications of a master formula for next-to-next-to-leading order soft and virtual QCD corrections to various electroweak, Higgs, and supersymmetric processes. They include Drell-Yan and charged Higgs production, single-top production in flavor-changing neutral-current processes, and squark and gluino production.
We compute the dominant logarithmically enhanced two-loop electroweak corrections to the electron-positron scattering differential cross section in the high energy limit for large scattering angles. Depending on the scattering angle and energy the two-loop corrections may exceed one percent and are important for the high-precision luminosity spectrum determination at a future linear collider.
General formulas as well as leading asymptotics for corrections to Z- and W-boson parameters are derived. Experimental data fits in Standard Model and its extensions are discussed and results are presented.
The aim of this article is to review the very important role played by radiative corrections in precision electroweak physics, in the framework of both the Fermi Theory of Weak Interactions and the Standard Theory of Particle Physics. Important theoretical developments, closely connected with the study and applications of the radiative corrections, are also reviewed. The role of radiative corrections in the analysis of some important signals of new physics is also discussed.
