Born cross section and the radiative corrections to its lowest order are considered in the frame work of QED with structureless nucleons including the emission of virtual and real photons. Result is generalized to take into account radiative corrections in higher orders of perturbation theory in the leading and next-to leading logarithmic approximation. Crossing processes are considered in the leading approximation.
The massive neutrino radiative decay $ν_i \rightarrow ν_j γ$ ($i \ne j$) is investigated within the Minimal Quark-Lepton Symmetry of the Pati-Salam type based on the $SU(4)_V \times SU(2)_L \times G_R$ group in an external constant crossed field ($\vec {\cal E} \perp \vec H$, ${\cal E}=H$). The matrix element $ΔM^{(X)}$ and the decay probability $W^{(X)}$ due to the leptoquark $X$ contribution are analysed. The effect of significant enhancement of the neutrino decay by the crossed field takes place. It is shown that the leptoquark contribution to the decay probability can dominate over the $W$…
We show that certain general properties of threshold and joint resummations in Drell-Yan cross sections hold as well for their crossed analogs in semi-inclusive deep-inelastic scattering and double-inclusive leptonic annihilation. We show that all plus-distribution corrections near threshold show the same structure, and are determined to all logarithmic order by two anomalous dimensions, one of which is a generalization of the D-term previously derived in Drell-Yan. We also discuss the possibility of universality in power corrections implied by the resummation.
Analytical calculations of radiative corrections in strong-field QED have hinted that in the presence of an intense plane wave the effective coupling of the theory in the high-energy sector may increase as the $(2/3)$-power of the energy scale. These findings have raised the question of their compatibility with the corresponding logarithmic increase of radiative corrections in QED in vacuum. However, all these analytical results in strong-field QED have been obtained within the limiting case of a background constant crossed field. Starting from the polarization operator and the mass operator i…
The initial-state radiative events in electron-positron annihilation into hadrons at DAFNE have been considered. The coresponding cross-section with the full first order radiative correction has been calculated. The analytical calculations take into account the realistic angular acceptance and energy cut of DAFNE photon detector.
The impact of final-state radiation (FSR) on the radiative return method for the extraction of the e+e- hadronic cross section is discussed in detail and experimental tests of the model dependence of FSR are proposed for the pi+pi- hadronic final state.
We employ the Polyakov world-line path-integral version of QCD to identify and resum at leading perturbative order enhanced radiative gluon contributions to the Drell-Yan type ($q\bar{q}$ pair annihilation) cross-sections. We emphasize that this is the first time that world-line techniques are applied to cross-section calculations.
The contribution of exclusive radiative tail to the cross section of semi-inclusive hadron leptoproduction has been calculated exactly for the first time. Although the experience of inclusive data analyses suggests us that the contribution of radiative tail from the elastic peak is of particular importance, similar effects in the semi-inclusive process were only recently estimated in the peaking approximation. The explicit expressions for the lepton part of the lowest order QED contribution of exclusive radiative tail to the five-fold differential cross section are obtained and discussed. Nume…
The cross sections for the processes $γν\to γγν$, $γγ\toγν\barν$ and $ν\barν\toγγγ$ are calculated for a range of center of mass energies from below $m_e$ to considerably above $m_e$, but much less than $m_W$. This enables us to treat the neutrino--electron coupling as a four--Fermi interaction and results in amplitudes which are electron box diagrams with three real photons and one virtual photon at their vertices. These calculations extend our previous low--energy effective interaction results to higher energies and enable us to determine where the effective theory is reliable.
Recently, Dicus and Repko computed nu gamma --> nu gamma gamma for energies below the threshold for e^{+}e^{-} pair production. They found across section on the order of 10^{-52} omega ^{gamma} with gamma =10, where omega is the CMS energy of one of the initial particles in MeV. Cross sections for the crossed processes are the same to factors of order one. This note investigates the extent to which these processes could, if their result extrapolates past 1 MeV: affect supernova dynamics; cut off the energy distribution of very high energy cosmic photons and neutrinos; and possibly give rise to…
We compute the order-$\as$ corrections to the total cross section and to jet rates for the process $\epem\to\epem +$ hadrons, where the hadrons are produced through crossed-channel quark exchange in the hard scattering of two off-shell photons originating from the incoming leptons. We use a next-to-leading order general-purpose partonic Monte Carlo event generator that allows the computation of a rate differential in the produced leptons and hadrons. We compare our results with the available experimental data for $\epem\to\epem +$ hadrons at LEP2.
The hadronic invariant mass distribution for the process of electron-positron annihilation into a pair of charged pions accompanied by a photon radiated from the initial state has been studied for the region of DA$Φ$NE energies. The Born cross-section and the electromagnetic radiative corrections to it are calculated for realistic conditions of the KLOE detector. The dependence on the physical parameters which define the event selection is obtained.
We discuss an inclusive approach to the measurement of the e+e- --> pi+ pi- cross--section by the radiative return method without photon tagging. The essential part of this approach is the choice of rules for event selection which provide rejection of events with 3 (or more) pions and decrease the final--state radiation background. The radiative corrections to the initial--state radiation process are computed for DAPhNE conditions, using the quasi--real electron approximation for both, the cross--section and the underlying kinematics. The two cases of restricted and unrestricted pion phase spa…
We calculate the cross-sections for the radiative formation of bound states by dark matter whose interactions are described in the non-relativistic regime by a Yukawa potential. These cross-sections are important for cosmological and phenomenological studies of dark matter with long-range interactions, residing in a hidden sector, as well as for TeV-scale WIMP dark matter. We provide the leading-order contributions to the cross-sections for the dominant capture processes occurring via emission of a vector or a scalar boson. We offer a detailed inspection of their features, including their velo…
The electromagnetic radiative correction to the cross section of the vector meson electroproduction is calculated. Explicit covariant formulae for the observed cross section are obtained. The dependence of the radiative correction on the experimental resolution and on the inelasticity cut is discussed. FORTRAN code DIFFRAD based on both exact (ultrarelativistic) and approximate sets of the formulae for the radiative correction to the cross section is presented. The detailed numerical analysis for kinematical conditions of the recent experiments on the diffractive electroproduction of vector me…
DIS of unpolarized electron by tensor-polarized deuteron with tagged collinear photon, radiated from initial electron, was considered. The cross section is derived in the Born approximation. The model-independent QED corrections to the Born cross section are also calculated using approach based on the account of all essential Feynman diagrams.
The cross-section for W^+W^- \to W^+W^- with arbitrarily polarized W bosons is calculated within the Electroweak Standard Model including the complete virtual and soft-photonic O(alpha) corrections. We show the numerical importance of the radiative corrections for the dominating polarized cross-sections and for the unpolarized cross-section. The numerical accuracy of the equivalence theorem is investigated in O(alpha) by comparing the cross-section for purely longitudinal W bosons obtained from the equivalence theorem and from the direct calculation. We point out that the instability of the W …
We have studied the radiative corrections from the fourth generation leptons in the context of the see-saw mechanism. We have estimated numerically the differential cross section for the process (${\rm e}^{+}{\rm e}^{-}\! \rightarrow {\rm W}^{+}{\rm W}^{-}$) at one-loop level, and found in the cross section the threshold behaviors for Majorana neutrino productions.
Radiative corrections in leading logarithmic approximation are calculated for the differential cross section of $e^- μ^+$ radiative scattering. In particular the interference term due to photon emission from electron and muon blocks are calculated in helicity independent and dependent parts. The calculation is applied to the kinematical conditions of existing DVCS data in electron-proton collisions. Both helicity odd and helicity even differential cross sections are considered.
In the analysis of the total cross section for the gamma* gamma* -> hadrons process, we include the four parton final states, which are part of the O(alpha_s^2) corrections. The four-parton final states contain the diagrams with gluon exchange in the crossed channel, which constitute the leading order of the BFKL resummation. We show that the diagrams with gluon exchange in the crossed channel play an important role in the large Y region, however their contribution to the cross section must be evaluated exactly. In fact, the high-energy limit, which constitutes the kinematic framework of the B…
We calculate the radiative corrections to the annihilation of the Dark Matter particles into leptons. Lepton masses are taken into account. As the Dark Matter particles are considered both Dirac and Majorana fermions. We sum up all the leading logarithms contributions where it is possible. We show that in the Dirac fermion case the resulting cross-section is consistent with the renormalization group prediction: the cross-section have the Drell-Yan form. Whereas, in the Majorana fermions case we have two essentially different limits of the resulting cross-section and quantitively the answer str…
The lowest order radiative correction to the differential cross-section of process of muon pair production with emission of hard photon at high energy electron-positron annihilation are calculated. Taking into account the emission of additional soft and hard photon the cross-section can be put in the form of Drell-Yan process in leading logarithmical approximation. Applying the crossing transformation we obtain the cross section of radiative electron-muon high-energy scattering process. Virtual and soft photon emission contributions of non-leading form are tabulated for several typical kinemat…
We study radiative corrections to chargino production at linear colliders with polarised electron beams. We calculate the one-loop corrected cross-sections for polarised electon beams due to three families of quarks and squarks, working in the $\bar{MS}$ scheme, extending our previous calculation of the unpolarised cross-section with one-loop corrections due to the third family of quarks and squarks. In some cases we find rather large corrections to the tree-level cross-sections. For example for the case of right-handed polarised electrons and large $\tan β$ the corrections can be of order 30%…
Electron-positron annihilation into hadrons plus an energetic photon from initial state radiation allows the hadronic cross-section to be measured over a wide range of energies. The full next-to-leading order QED corrections for the cross-section for e^+ e^- annihilation into a real tagged photon and a virtual photon converting into hadrons are calculated where the tagged photon is radiated off the initial electron or positron. This includes virtual and soft photon corrections to the process e^+ e^- \to γ+γ^* and the emission of two real hard photons: e^+ e^- \to γ+ γ+ γ^*. A Monte Carlo gener…
Cross sections of the e+e- annihilation into one photon plus two vector mesons, such as J/psi rho, J/psi phi, and rho phi at the center of mass energy \sqrt{s}=10.58GeV are calculated. These shed light on the measurement of the e+e- annihilation cross section via radiative return in B-factories. At another center of mass energy \sqrt{s}=3.097GeV, namely the J/psi resonance peak, the processes e+e- --> gamma VV and e+e- --> gamma gamma V (with V being rho, omega, or phi) are calculated with similar method. These calculations give estimation of the background levels in the study of radiative or …
In this paper we study the possibility of generalizing the classical photoabsorption ($γa \to b c$) sum rules, to processes $b c \to γa$ and crossed helicity amplitudes. In the first case, using detailed balance, the sum rule is written as $\int_{ν_{th}}^\infty {\frac{dν}ν} KΔσ_{Born} (ν)=0$ where $K$ is a kinematical constant which depends only on the mass of the particles and the center of mass energy. For other crossed helicity amplitudes, we show that there is a range of values of $s$ and $t$ for which the differential cross section for the process $γb \to a c$ or $a c \to γb$ in which the…
The complete tree level cross section for $e^+e^- \to e^- \barν_e u \bar{d} γ$ is computed and discussed in comparison with the cross sections for $e^+e^- \to e^- \barν_e u \bar{d} $ and $e^+e^- \to \bar{u} d u \bar{d}$. Event generators based on the GRACE package for the non-radiative and radiative case are presented. Special interest is brought to the effect of the non-resonant diagrams overlooked so far in other studies. Their contribution to the total cross section is presented for the LEP II energy range and for future linear colliders ($\sqrt s$ =500 GeV). Effects, at the W pair threshol…
The measurement of the hadronic cross-section in $e^+ e^-$ annihilation at high luminosity factories using the radiative return method is motivated and discussed. A Monte Carlo generator which simulates the radiative process $e^+ e^- \to γ+hadrons$ at the next-to-leading order accuracy is presented. The analysis is then extended to the description of events with hard photons radiated at very small angle.
I present higher-order radiative corrections from collinear and soft gluon emission for the associated production of a charged Higgs boson with a $W$ boson. The calculation uses expressions from resummation at next-to-leading-logarithm accuracy. From the resummed cross section I derive analytical formulas at approximate NNLO and N$^3$LO. Total cross sections are presented for the process $b{\bar b} \rightarrow H^- W^+$ at various LHC energies. The transverse-momentum and rapidity distributions of the charged Higgs boson are also calculated.
We determine the O(α_s) radiative corrections to polarized top quark pair production in e+ e- -annihilations with a specified gluon energy cut. We write down fully analytical results for the unpolarized and polarized O(α_s) cross sections e+ e- -> tbar t (G) and e+ e- -> tbar t(pol.) (G) including their polar orientation dependence relative to the beam direction. In the soft gluon limit we recover the usual factorizing form known from the soft gluon approximation. In the limit when the gluon energy cut takes its maximum value we recover the totally inclusive unpolarized and polarized cross sec…
QED radiative corrections to the cross-section of muon-antimuon annihilation into Higgs boson and photon are calculated within the 1-loop approximation. We write down the expression for cross-section in the form of Drell-Yan process, taking into account higher order leading logs. The non-singlet structure functions of fermions are shown to obey here evolution equations of twist-3 operators. Numerical estimation shows an importance of the correction in the region close to the threshold of Higgs production.
An approach to calculate radiative corrections to unpolarized cross section of semi-inclusive electroproduction is developed. An explicit formulae for the lowest order QED radiative correction are presented. Detailed numerical analysis is performed for the kinematics of experiments at the fixed targets.
The structure function approach and the parton picture, developed for the theoretical description of the deep inelastic electron-proton scattering, also proved to be very effective for calculation of radiative corrections in Quantum Electrodynamics. We use them to calculate radiative corrections to the cross section of electron-proton scattering due to electron-photon interaction, in the experimental setup with the recoil proton detection, proposed by A.A. Vorobev to measure the proton radius. In the one-loop approximation, explicit expressions for these corrections are obtained for arbitrary …
The production cross sections of $e^+e^- $ to a heavy quarkonium with $C$-parity even $S-$wave and $P-$wave associated with a photon are analyzed in the framework of non-relativistic Quantum Chromodynamics(NRQCD) factorization formalism. The short-distance coefficients are determined up to the next-to-leading order(NLO) QCD radiative corrections for $S-$ and $P-$wave and NLO relativistic corrections for $S-$wave in analytical forms. Applying the results to estimate the cross sections we find that both the radiative and relativistic corrections are considerable.
The largest radiative corrections to the cross section of electron-proton scattering at high energies are associated with emission of photons, real and virtual, by electron. They contain large logarithms coming from soft and collinear photons. Cancellation of the contributions of the soft photons to virtual and real corrections is well known. Less known is the fact that the contributions of the photons collinear to scattered electrons are also cancelled for the most of experiments. On the contrary, contributions of the photons collinear to initial electrons as a rule are not cancelled. It is s…
Electron--positron annihilation into hadrons plus an energetic photon from initial-state radiation allows the hadronic cross-section to be measured over a wide range of energies at high luminosity meson factories. Weighted integrals over this cross-section are a decisive input for electroweak precision tests. A Monte Carlo event generator called PHOKHARA has been developed, which simulates $e^+ e^- \to$ hadrons + photon(s) at the NLO accuracy. The latest tests and upgrades are presented in this paper.
Radiative effects in the electroproduction of photons in polarized ep-scattering are calculated in the leading log approximation and analyzed numerically for kinematical conditions of current measurement at Jefferson Lab. Radiative corrections to the cross sections, their azimuthal distributions and Fourier coefficients are in particular focus. Kinematical regions where the radiative corrections are considerable are identified.
The cross section for $e^-e^- \to e^-e^-$ with arbitrary electron polarizations is calculated within the Electroweak Standard Model for energies large compared to the electron mass, including the complete virtual and soft-photonic $O(α)$ radiative corrections. The relevant analytical results are listed, and a numerical evaluation is presented for the unpolarized and polarized cross sections as well as for polarization asymmetries. The relative weak corrections are typically of the order of 10%. At low energies, the bulk of the corrections is due to the running of the electromagnetic coupling c…
QED radiative corrections to the cross section of diffractive electro- and photoproduction of vector mesons is calculated at HERA energies. Both semi-analytical and Monte Carlo approaches are discussed and compared.
The coplete analysis of the model-independent leading radiative corrections to cross-section and polarization observables in semi-inclusive deep-inelastic electron-nucleus scattering with detection of a proton and scattered electron in coincidence has been performed. The basis of the calculations consists of the Drell-Yan like representation in electrodynamics for both spin-independent and spin-dependent parts of the cross-section in terms of the electron structure functions. The applications to the polarization transfer effect from longitudinally polarized electron beam to detected proton as …
The O(α) electroweak radiative corrections to the process pp, ppbar\to W \to\ell^\pmν(\ell=e,μ) are calculated. The O(α) corrections can be decomposed into separately gauge invariant contributions to the W boson production and decay processes. Factorizing the collinear singularity associated with initial state photon radiation into the parton distribution functions, we find that initial state corrections have a significantly smaller effect than final state radiative corrections. We study in detail the effect of electroweak radiative corrections on a number of interesting observables: the W tra…
We calculate the O(alpha) electroweak corrections to charged- and neutral-current deep-inelastic neutrino scattering off an isoscalar target. The full one-loop-corrected cross sections, including hard photonic corrections, are evaluated and compared to an earlier result which was used in the NuTeV analysis. In particular, we compare results that differ in input-parameter scheme, treatment of real photon radiation and factorization scheme. The associated shifts in the theoretical prediction for the ratio of neutral- and charged-current cross sections can be larger than the experimental accuracy…
We consider the scenario in the radiative seesaw model where the dark matter particle is the lightest $Z_2$-odd fermion. We identify the regions of the parameter space of the model compatible with neutrino oscillation data, with the upper limits from rare charged lepton decays and with the observed dark matter abundance via thermal freeze-out, and we compute the dark matter scattering cross section with nuclei via the one-loop exchange of a photon, a $Z^0$-boson or a Higgs boson. We find that the predicted spin-independent cross section lies below the current LUX limit, although, for some choi…
A cubic kilometer scale experiment has been proposed to detect cosmic neutrinos of energy from tens of GeV up to the highest energies observed for cosmic rays, around 10**20 eV, or possibly even beyond. Detection efficiencies depend crucially on the neutrino-nucleon cross section at these energies at which radiative corrections beyond the lowest order approximation could become non-negligible. The differential cross sections can be modified by more than 50% in some regions of phase space. Estimates of corrections to the quantities most relevant for neutrino detection at these energies give, ho…
A massive real scalar dark matter particle $S$ can couple to Standard Model leptons or quarks through a vector-like fermionic mediator $ψ$, a scenario known as the Vector-like portal. Due to helicity suppression of the annihilation cross section into a pair of SM fermions, it has been shown in previous works that radiative corrections, either at one-loop or through radiation of gauge bosons, may play a significant role both in determining the relic abundance and for indirect detection. All previous works considered the limit of massless final state quarks or leptons. In this work, we focus on …
We have calculated part of O($α_{S}$) QCD radiative correction to the total cross-section of top's threshold production in $ e^{+}e^{-} \to t\bar t \to W^{-} b W^{+} \bar b$ reaction. We found out a curious fact: there is no O($α_{S}$) correction to the total cross-section, originated from $b \bar b , t \bar b ,\bar t b $ gluon exchange and corresponding gluon emission. Thus, all O($α_{S}$) corrections which are non-zero, can be classified as: 1) corrections to $t \bar t$ nonrelativistic potential 2) corrections to the top's width 3) hard gluon correction to $γt \bar t$-vertex. These correctio…
The rate of associative production of Higgs and $Z$--bosons by charged leptons in the field of a plane electromagnetic wave of arbitrary intensity and in the constant crossed field is obtained. The cross section is examined as a function of particle energies and external field intensities for various values of the Higgs boson mass. It is shown, that the photoproduction cross section increases logarithmically at super high energies up to the values, that essentially exceed the cross section of the reaction $e^+e^-\to ZH,$ which, at present, is considered as the most probable channel of Higgs bo…
We briefly describe the RacoonWW approach to calculate radiative corrections to e+ e- -> W W -> 4 fermions and present numerical results for the total W-pair production cross section at LEP2.
Radiative corrections to ${\rm e}^{+}{\rm e}^{-}\! \rightarrow {\rm W}^{+}{\rm W}^{-}$ from Majorana neutrinos are studied in the context of the see-saw mechanism. Focusing on the effects of the fourth generation neutrinos, we calculate W-pair form factors, the differential cross sections and the forward-backward asymmetries for the polarized electrons at one-loop level. The behaviour of the form factors at the threshold of Majorana particle pair productions is found to differ from that of Dirac particle pair productions. In the cross section for unpolarized electrons, the radiative correction…
A statistical analysis of the elastic unpolarized electron proton scattering data shows that, at large momentum transfer, the size and the $ε$ dependence of the radiative corrections, as traditionally calculated and applied, may induce large correlations of the parameters of the Rosenbluth fit, which prevent a correct extraction of the electric proton form factor. Using the electron QED structure (radiation) function approach the cross section of elastic electron-proton scattering in leading and next-to leading approximations is calculated and expressed as a correction to the Born cross sectio…
This document reviews the general approach to correcting the process e+e-->X->ffbar for radiative effects, where X represents an exchanged gauge boson arising from some new physics. The validity of current methods is discussed in the context of the differential cross section. To this end the universality of the dominant QED radiative corrections to such a process is discussed and an attempt is made to quantify it. The paper aims to justify, as much as possible, the general approach taken by e+e- collider experiments to the issue of how to treat the dominant radiative corrections in fitting mod…
Electroweak corrections to longitudinal gauge and Higgs boson scattering amplitudes are calculated. Due to Sudakov double logarithms, the effect is a suppression of amplitude that grows rapidly with increasing center of mass energy leading to significant reduction of cross sections compared to tree level results. For example, the suppression factor for the cross section of $W^+_{\text{L}}W^-_{\text{L}}$ scattering due to these corrections varies from 0.3 at the center of mass energy of $100\text{TeV}$ to a factor of $10^{-12}$ at the center of mass energy of $10^{13}\text{TeV}$. The modificati…
The cross-section for ZZ->ZZ with arbitrarily polarized Z bosons is calculated within the electroweak Standard Model including the complete O(alpha) corrections. We show the numerical importance of the radiative corrections and elaborate its characteristic features. The treatment of the Higgs-boson resonance is discussed in different schemes including the S-matrix-motivated pole scheme and the background-field method. The numerical accuracy of the equivalence theorem is investigated by comparing the cross-sections for purely longitudinal Z bosons obtained from the equivalence theorem and from …
We investigate the effects of photon radiation on deep-inelastic $\reγ$ scattering. Depending on the set of variables chosen, we find appreciable effects in the kinematic region accessible at LEP2. Convenient analytic results for $O(α)$ corrected differential cross sections are presented.
The complete electroweak O(alpha) radiative corrections to the Higgs-boson production processes e+ e- -> nu_l anti-nu_l H (l=e,mu,tau) are calculated in the electroweak Standard Model. For e+ e- -> nu_e anti-nu_e H, where ZH production and W-boson fusion contribute, both production channels are added coherently. The calculation of the corrections is described in some detail including, in particular, the treatment of the Z-boson resonance in the ZH-production channel. The discussion of numerical results focusses on the total cross section as well as on angular and energy distributions of the Hi…
We discuss the radiative corrections to charged and neutral current deep-inelastic neutrino--nucleon scattering in the minimal supersymmetric standard model (MSSM). In particular, deviations from the Standard Model prediction for the ratios of neutral- to charged-current cross sections, $R^ν$ and $R^{\barν}$, are studied, and results of a scan over the MSSM parameter space are presented.
1-loop diagrammatic calculations of cross sections and decay widths of neutral Higgs bosons in the minimal supersymmetric standard model are reviewed and compared with compact expressions in the effective potential approximation.
The cross-section for $γγ\to W^+ W^-$ with arbitrary polarized photons and W bosons is calculated within the electroweak Standard Model including the complete virtual and soft-photonic ${\cal O}(α)$ corrections. We present a detailed numerical discussion of the complete radiative corrections and an analytical investigation of the leading corrections. It turns out that in the on-shell renormalization scheme for fixed $M_W$ no leading corrections associated with the running of $α$ or heavy top-quark and Higgs-boson masses occur. The corrections are typically of the order of 10\%. They reach, how…
