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Register a new userComplete electroweak O(alpha) corrections to charged-current e+e- --> 4fermion processes
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The complete electroweak O(alpha) corrections are calculated for the charged-current four-fermion production processes e+e- --> nu_tau tau+ mu- anti-nu_mu, u anti-d mu- anti-nu_mu, and u anti-d s anti-c. The calculation is performed using complex gauge-boson masses, supplemented by complex couplings to restore gauge invariance. The evaluation of the occurring one-loop tensor integrals, which include 5- and 6-point functions, requires new techniques. Explicit numerical results are presented for total cross sections in the energy range from the W-pair-production threshold region up to a scattering energy of 2TeV. A comparison with the predictions based on the double-pole approximation (DPA) provided by the generator RacoonWW reveals corrections beyond DPA of < 0.5% in the energy range 170-300GeV, in agreement with previous estimates for the intrinsic DPA uncertainty. The difference to the DPA increases to 1-2% for sqrt{s} = 1-2TeV. At threshold, where the DPA becomes unreliable, the full O(alpha) calculation corrects an improved Born approximation (IBA) by about 1.6%, also consistent with an error estimate of the IBA.
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By using the GRACE-Loop system, we calculate the full $mathcal{O}(alpha)$ electroweak radiative corrections to the process $e^+e^- rightarrow e^+e^- gamma$, which is important for future investigations at the International Linear Collider (ILC). With the GRACE-Loop system, the calculations are checked numerically by three consistency tests: ultraviolet finiteness, infrared finiteness, and gauge-parameter independence. The results show good numerical stability when quadruple precision is used. In the phenomenological results, we find that the electroweak corrections to the total cross section range from $sim -4%$ to $sim -21%$ when $sqrt{s}$ varies from $250$ GeV to $1$ TeV. The corrections also significantly affect the differential cross sections, which are a function of the invariant masses and angles and the final-particle energies. Such corrections will play an important role for the high-precision program at the ILC.
The calculation of the full electroweak O(alpha) corrections to the charged-current four-fermion production processes e+e- --> nu_tau tau+ mu- anti-nu_mu, u anti-d mu- anti-nu_mu, and u anti-d s anti-c is briefly reviewed. The calculation is performed using the complex-mass scheme for the gauge-boson resonances. The evaluation of the occurring one-loop tensor integrals, which include 5- and 6-point functions, requires new techniques. The effects of the complete O(alpha) corrections to the total cross section and to the production-angle distribution are discussed and compared to predictions based on the double-pole approximation, revealing that the latter approximation is not sufficient to fully exploit the potential of a future linear collider in an analysis of W-boson pairs at high energies.
We present the full $mathcal{O}(alpha)$ electroweak radiative corrections to the process $e^+e^- rightarrow t bar{t} gamma$ at the International Linear Collider (ILC). The computation is performed with the help of the GRACE-Loop system. We present the total cross-section and the top quark forward-backward asymmetry ($A_{FB}$) as a function of the center-of-mass energy and compare them with the process $e^+e^- rightarrow t bar{t}$. We find that the value of $A_{FB}$ in $t bar{t} gamma$ production is larger than $A_{FB}$ in $tbar{t}$ production. It is an important result for the measurement of the top quark forward-backward asymmetry at the ILC. Applying a structure function method, we also subtract the QED correction to gain the genuine weak correction in both the $alpha$ scheme and the $G_{mu}$ scheme ($delta_{W}^{G_{mu}}$). We obtain numerical values for $delta_{W}^{G_{mu}}$ which are changing from 2% to -24% when we vary the center-of-mass energy from 360 GeV to 1 TeV.
We present the full O(alpha) corrections to single Higgs production in e+e- collision. The computation is performed with the help of GRACE-LOOP where a generalized non-linear gauge fixing condition is implemented. The numerical results are checked by testing their UV and IR finiteness as well as their independence on all five non-linear gauge parameters. We find that for a 500 GeV collider and a light Higgs boson of mass 150GeV, the total correction is small when the results are expressed in terms of alpha rather than G_mu. For a higher Higgs boson mass of 350GeV, the correction is of order -10%.
The paper describes high-precision theoretical predictions obtained for the cross sections of the process $e^+e^- to ZH$ for future electron-positron colliders. The calculations performed using the SANC platform taking into account the full contribution of one-loop electroweak radiative corrections, as well as longitudinal polarization of the initial beams. Numerical results are given for the energy range $E_{cm}=250$ GeV - $1000$ GeV with various polarization degrees.
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