arXiv subjects
Publications and source records attributed to Fernand M. Renard.
We propose further tests of the occurence of scale dependent heavy particle masses (Z,W,t) and of strong final state interactions by comparing Z longitudinal polarization rates in different kinematical distributions of the $e^+e^-\to Zt\bar t$ and in $e^+e^-\to ZW^+W^-$ processes.
We show that the $ZWW$ production process may give complementary informations about scale dependent heavy particle masses and possible final state interactions as compared to previously studied top quark production processes. We illustrate the $p_Z$ distribution of the rate of longitudinal $Z_L$ component showing its sensitivity to these effects which may arise from heavy particle substructure or a dark matter (DM) environment.
We assume that the mass of the heavy standard particles ($Z,W,t,...$) arises from a special coupling with dark matter and that this implies a corresponding peculiar connection of these particles to the dark sector. We give examples of possible tests of this assumption in $e^+e^-\to Z+X,~ W^+W^-+X, ~t\bar t+X$ and we mention other possible studies.
Similarly to the previously studied case of inclusive $t\bar t$ production we consider the inclusive $t\bar b$ production in $e^+e^-$, gluon~gluon and photon~photon collisions. We show how it is sensitive to new physics, connected to the charged Goldstone sector and possibly generated by Higgs and/or top quark compositeness.
We look for possible (partial) compositeness properties of the bottom quark according to the Composite Standard Model (CSM) concept in the same way this was previously done for Higgs boson and top quark. After looking at the direct form factor effects appearing in $e^+e^-\to b\bar b$ we analyze the more complex features of the $e^+e^-, gg, γγ\to b\bar b H, b\bar b Z, t\bar b W^-$ processes. We emphasize typical differences appearing between CSM concerving and CSM violating cases. We also mention the possible appearence of an effective bottom mass.
We extend our previous analysis of $t\bar t H, t\bar t Z, t\bar b W$ production in $e^+e^-$ collisions within the CSM (Composite Standard Model) concept of Higgs boson and top quark compositeness to the case of gluon-gluon and photon-photon collisions. We show that remarkable differences may indeed appear between the effects generated by CSM conserving and by CSM violating sets of form factors.
We study the modifications of the amplitudes and cross sections of several processes, especially $e^+e^- \to t\bar t H, t\bar t Z, t\bar b W$, generated by Higgs boson and top quark compositeness, in particular within the CSM concept. We illustrate the observable differences that may appear between various, CSM conserving or CSM violating, compositeness possibilities.
We study the modifications of the $γγ\to ZH$ amplitudes and cross sections generated by Higgs and top quark compositeness in particular within the CSM concept. We insist on the particular interest of polarized photon-photon collisions which should allow to identify the origin of the large observable differences between various, CSM conserving or CSM violating, compositeness possibilities.
We study more deeply the sensitivity of the $ZH$ production process in gluon-gluon collisions to the details of a possible Higgs and top quark compositeness. We establish a relation between Higgs and top quark form factors which would keep the basic cancellation appearing in SM and satisfy the concept of CSM. We give illustrations showing the spectacular consequences of various choices preserving or violating this CSM constraint.
In the spirit of the Composite Standard Model (CSM) we look at the effect of $H$, $Z_L$ compositeness on $ZH$ production in gluon-gluon and photon-photon collisions. Because they would perturb the basic cancellations occuring in SM amplitudes, such compositeness effects would lead to spectacular modifications of the energy dependence of the amplitudes and cross sections. We illustrate this fact by introducing $H$, $Z_L$ test form factors and computing the corresponding differential cross section and the fraction of longitudinal $Z_L$ production.
We assume that the Higgs doublet has a composite structure, respecting the main standard model properties, and therefore called Composite Standard Model (CSM), but leading (through Goldstone equivalence) to $Z_L$ and $W_L$ form factors. We illustrate how such a form factor affecting the $ZZ_LH$ coupling will be directly observable in $e^+e^-\to ZH$. We then show the spectacular consequences which would appear in the inclusive processes $e^+e^-\to Z_L+anything $. Such a form factor could also affect the $γW^+_LW^-_L$ and $Z W^+_LW^-_L$ vertices and we show what effects this would generate in $e^+e^-\to W^+W^-$ (especially in $e^+e^-_R\to W^+_LW^-_L$) and in $e^+e^-\to W_L+anything $. We finally mention the $γγ\to W^+W^-$ process and several other processes in hadronic collisions which could be similarly affected.
We consider the inclusive top quark distributions in $e^+e^-\to t_{L,R}+\rm{anything}$. We analyze the modifications of the basic SM contributions which would result from $t_{R}$ compositeness for example from the presence of form factors in the $t_{R}$ couplings and of an effective top mass $m_t(s)$. We also look at parton like contributions representing additional new particle production related to $t_{R}$ constituents. One observes a large sensitivity of the $t_{R}$ inclusive distribution to these various effects with specific shapes differing from those of the $t_{L}$ distribution and we show that these effects may even be also observable in the unpolarized top case.
We consider various processes of single top production at LHC in the theoretical framework of the MSSM and examine the role of the supersymmetric electroweak one-loop corrections in a special moderately light SUSY scenario, in an initial parton-pair c.m. high energy range where a logarithmic asymptotic expansion of Sudakov type can be used. We show that the electroweak virtual effects are systematically large, definitely beyond the relative ten percent size, particularly for a final $tH^-$ pair where a special enhancement is present. We show then in a qualitative way the kind of precision tests of the model that would be obtainable from accurate measurements of the energy distributions of the various cross sections and of the top polarization asymmetries.
We compare the logarithmic Sudakov expansions of the process e+e- --> W+W- in the one-loop approximation and in the resummed version, to subleading order accuracy, in the SM case and in a light SUSY scenario for the MSSM. We show that the two expansions are essentially identical below 1 TeV, but differ drastically at higher (2,3 TeV) center of mass energies. Starting from these conclusions, we argue that a complete one-loop calculation in the energy region below 1 TeV does not seem to need extra two-loop corrections, in spite of the relatively large size of the one-loop effects.
We consider the high energy behaviour of the amplitudes for pair production of charged leptons, quarks, Higgs bosons, sleptons, squarks and charginos at lepton colliders. We give the general expressions of the leading quadratic and subleading linear logarithms that appear at the one loop level, and derive the corresponding resummed expansions to \underline{subleading} logarithmic order accuracy. Under the assumption of a relatively light SUSY scenario and choosing the MSSM as a specific model, we compare the predictions of the one-loop and of the resummed expansions at variable energy. We show that the two predictions are very close in the one TeV regime, but drastically differ in the few ($2,3$) TeV range.
We discuss New Physics effects in fermion pair production at LC in the framework of the ``Z-peak subtracted approach'', a theoretical scheme that exploits the experimental measurements at LEP1 and SLC as input parameters. In particular, we discuss the role of the longitudinal polarization asymmetry $A_{LR,μ}$ which turns out to be a very sensitive probe to New Physics of universal type. The extension of the method to non universal effects is discussed and an application is given in two examples: general contact interactions and low energy gravity models with graviton exchange.