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Register a new userCEEX EW Corrections for f bar{f}rightarrow fbar{f} at LHC, Muon Colliders and FCC-ee as Realized in KK MC 4.22
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B.F.L. Ward Baylor University
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With an eye toward the precision physics of the LHC, FCC-ee and possible high energy muon colliders, we present the extension of the CEEX (coherent exclusive exponentiation) realization of the YFS approach to resummation in our KK MC to include the processes fbar{f}rightarrow fbar{f}, f=mu,tau, q, u_ell, f=e, mu,tau, q, u_ell, q=u,d,s,c,b,t, ell =e,mu,tau with f e f. After giving a brief summary of the CEEX theory with reference to the older EEX (exclusive exponentiation) theory, we illustrate theoretical results relevant to the LHC, FCC-ee, and possible muon collider physics programs.
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We present the upgrade of the coherent exclusive (CEEX) exponentiation realization of the Yennie-Frautschi-Suura (YFS) theory used in our Monte Carlo ({cal KK} MC) to the processes fbar{f}rightarrow fbar{f}, f=mu,tau,q, u_ell, f=e,mu,tau,q, u_ell, q=u,d,s,c,b,t, ell=e,mu,tau with f e f, with an eye toward the precision physics of the LHC and possible high energy muon colliders. We give a brief summary of the CEEX theory in comparison to the older (EEX) exclusive exponentiation theory and illustrate theoretical results relevant to the LHC and possible muon collider physics programs.
The past ten years of physics with e+e- colliding experiments at LEP and SLAC have shown the success of these experiments on not only impressively proving the theoretical predictions of the Standard Model (SM), but also to help provide stringent bounds on physics beyond the SM. With this experience in mind, there appear two equally fascinating opportunities for studying fermion-pair production processes at a future Linear Collider (LC). On the one hand, performing high precision measurements to the SM, for example, when running with high luminosity at the Z boson resonance, could be a quick and feasible enterprise in order to pin down the symmetry breaking mechanism of the electroweak sector through indirectly determining the masses of a light SM or MSSM Higgs boson or supersymmetric particles via virtual corrections. On the other hand, looking for such particles in direct production or other `New Physics effects at energies between, for example, roughly 500 and 800 GeV will naturally be the main motivation to pursue the challenging endeavor of building and utilizing such a unique facility. These two scenarios for the LC shall be sketched here, with particular emphasis on the semi-analytical program ZFITTER for fermion-pair production in comparison with numerical programs like TOPAZ0, KK2f, and others.
${cal KK}$MC-hh is a precision event-generator for Z production and decay in hadronic collisions, which applies amplitude-level resummation to both initial and final state photon radiation, including perturbative residuals exact through ${cal O}(alpha^2L)$, together with exact ${cal O}(alpha)$ EW matrix element corrections. We present some comparisons to other programs and results showing the effect of multi-photon radiation for cuts motivated by a recent ATLAS W mass analysis. We also show preliminary untuned comparisons of the electroweak corrections of ${cal KK}$MC-hh to those of HORACE, which includes exact ${cal O}(alpha)$ corrections with resummed final-state photon radiation.
With an eye toward the precision physics of the LHC, such as the recent measurement of $M_W$ by the ATLAS Collaboration, we present here systematic studies relevant to the assessment of the expected size of multiple photon radiative effects in heavy gauge boson production with decay to charged lepton pairs. We use the new version 4.22 of ${cal KK}$MC-hh so that we have CEEX EW exact ${cal O}(alpha^2 L)$ corrections in a hadronic MC and control over the corresponding EW initial-final interference (IFI) effects as well. In this way, we illustrate the interplay between cuts of the type used in the measurement of $M_W$ at the LHC and the sizes of the expected responses of the attendant higher order corrections. We find that there are per cent to per mille level effects in the initial-state radiation, fractional per mille level effects in the IFI and per mille level effects in the over-all ${cal O}(alpha^2 L)$ corrections that any treatment of EW corrections at the per mille level should consider. Our results have direct applicability to current LHC experimental data analyses.
High precision experimental measurements of the properties of the Higgs boson at $sim$ 125 GeV as well as electroweak precision observables such as the W -boson mass or the effective weak leptonic mixing angle are expected at future $e^+e^-$ colliders such as the FCC-ee. This high anticipated precision has to be matched with theory predictions for the measured quantities at the same level of accuracy. We briefly summarize the status of these predictions within the Standard Model (SM) and of the tools that are used for their determination. We outline how the theory predictions will have to be improved in order to reach the required accuracy, and also comment on the simulation frameworks for the Higgs and EW precision program.
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