Search

At ICHEP 2024 CMS has published RUN2 results for X650->ZZ->4leptons and reached the conclusion that there is no evidence for a scalar resonance H650 decaying into ZZ, as was also concluded by ATLAS using an MVA analysis optimised for a scalar particle. Since this resonance is indicated into ZZ in a Cut Based Analysis and into three other modes: WW, H95H125 and A450Z, the present paper is an attempt to understand these apparent contradictions. Our conclusion, to be confirmed by ATLAS and CMS experiments, is that strict selections for the reaction H650->ZZ mode seem inadequate, cutting as much into the signal than into the background, therefore reducing its statistical significance. A possible interpretation of this behaviour is that these selections are inefficient for a tensor particle produced by VBF and decaying into ZZ with an angular distributions similar to the Drell Yan background. If true, our description of the various findings in term of the Georgi Machacek model needs to be deeply revised, which is attempted in the present note. A scenario with T650 as a tensor resonance is presented which naturally accommodates WW/ZZ and H95H125 decays, while we suggest that A450Z coud come from a scalar resonance degenerate in mass with T650., Comment: 11 pages, 8 figures, Presented at the 3rd ECFA workshop on e+e- Higgs/EW/Top Factories, Paris, 9-11 Oct. 24

A global interpretation of several significant indications of scalar resonances observed at LHC is achieved using the Georgi Machacek model. Among many other consequences, one predicts large cross sections for the processes ggFH(320)->h(125)h(125) and A(151)A(151) and ggF->A(420)->H(320)Z, where H(320) has been observed in A(420)->H(320)Z->bbbbl+l- and where A(151) is observed into two photons accompanied by a b jet, a lepton or missing transverse energy. We predict that ggF->H(320) has a cross section of about 2000 fb with a BR into h(125)(125) of 17% and into A(151)A(151) of 45%. Henceforth we predict that ggF->H(320)->hh will dominate over the SM process h*->hh, where h is the SM h(125) scalar. One expects that H(320)->A(151)A(151) can be observed into bbbb, becoming one of the most significant BSM phenomena identified so far. Arguments in favor of a SUSY version of GM are also provided., Comment: 19 pages, 14 figures Work for the 2024 International Workshop on Future Linear Colliders (LCWS2024)

Several indications for neutral scalars are observed at the LHC. One of them, a broad resonance peaked at about 650 GeV which we call H(650), was first observed by an outsider combining published histograms from ATLAS and CMS on ZZ -> 4 leptons searches, and this combination shows a local significance close to 4 s.d. Since then, CMS has reported two other indications at the same mass, with similar local significances: H->WW->2leptons+neutrinos and H(650)->bbh(125) where mbb~90 GeV and h(125)->gam gam. ATLAS has completed its analysis of ZZ->4 leptons from which we infer an indication for H(650) with 3.5 s.d. significance. Combining these three results, one gets a global statistical significance above 6 s.d. H(650) has a coupling to WW similar to h(125) and therefore we argue that a sum rule (SR) required by unitarity for W+W- scattering implies that there should be a compensating effect from a doubly charged scalar H++, with a large coupling to W+W+. We therefore predict that this mode should become visible through the vector boson fusion process W+W+->H++, naturally provided by LHC. A recent indication for H++(450)->W+W+ from ATLAS allows a model independent interpretation of this result through the SR constraint which gives BR(H++->W+W+)~10%, implying the occurrence of additional decay modes H+W+ and H+H+ from one or several light H+ with masses below mH++ - mW or MH++/2, that is mH+ < 370 GeV or 225 GeV. A similar analysis is performed for H+(375)->ZW, indicated by ATLAS and CMS. Both channels suggest a scalar field content similar to the Georgi Machacek model with triplets, at variance with the models usually considered. Implications on precision measurements are presented followed by a complete extraction of the GM parameters. An alternate interpretation of the 650 GeV resonance as a tensor is also briefly discussed. Implications for precision measurements are presented., Comment: 30 pages, 14 figures, Work for the 2023 ECFA Workshop on Higgs/EW/Top factories in Paestum (Salerno) / Italy from 11 - 13 October 2023

In view of the future Higgs factories, this work presents the status of scalar searches at the LHC with an emphasis on the H(650) resonance which has been observed in WW, ZZ and h(95)h(125) channels, with a cumulative evidence of about 7 s.d. global significance. Its interpretation in models, restricted to extension of the scalar sector by SU(2) singlets and doublets, is clearly excluded, while its interpretation in models with additional triplets requires an extension with respect to the conventional Georgi-Machacek model. A general picture of these searches is updated, showing that h(95) is also reaching a similar level of evidence while two other candidates, A(400) and h(151), although less prominent, are above the 4 s.d. global evidence., Comment: 14 pages, 9 figures, Work presented by F. Richard at the ECFA workshop on Higgs/EW/top factories in DESY, October 2022

After the long-standing mismatch between ALR and AFBb measurements for predicting the Higgs boson mass, the recent and very precise result on Mw confirms the existence of a crisis in the sector of electroweak measurements. In this note, it is shown that ALR and Mw can be simply reconciled by assuming a common value for the T parameter. Consequently, the AFBb deviation is amplified and reaches a 4 s.d. significance. Interpreting this as evidence for a non-universal behaviour of the b quark is proposed within an extra dimension model. Large deviations with respect to the SM are expected at future Z factories., Comment: 6 pages, 2 figures

The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community., Comment: 356 pages, Large pdf file (40 MB) submitted to Snowmass 2021; v2 references to Snowmass contributions added, additional authors; v3 references added, some updates, additional authors

Following an investigation of several indications for new physics from LHC data, a detailed exploration of the Georgi-Machacek (GM) model was elaborated in a previous publication. This framework is used here to interpret the findings of Crivellin et al., which were obtained by combining the 2 photon mass spectrum from ATLAS and CMS, adding extra conditions, the most efficient one being the presence of >90 GeV missing transverse energy. The claim is a ~5 s.d. excess at 151 GeV. The GM model naturally explains this as coming from the cascade A(400)->H(151)Z, where H(151) is an isosinglet predicted by GM and where the accompanying signal comes from the decay of a Z boson into neutrino pairs. Satisfying the constraints from LHC measurements of the ZWW channel, which can receive a large contribution from this cascade, suggests that H(151) could dominantly decay into two light CP-odd scalars, following an ATLAS indication for h(125) decaying into bbmumu. A spectacular occurrence of signals is predicted at an $e^+e^-$ collider operating up to 1 TeV, an energy sufficient to cover the whole scenario., Comment: 20 pages,7 figures, Ongoing work presented at the ILC Workshop on Potential Experiments (ILCX2021), october 2021

Following various LHC indications for new scalars, an interpretation of these is given in terms of the Georgi-Machacek (GM) model. On top of the confirmed SM Higgs boson, there are indications for a light Higgs at 96 GeV, for a CP-odd boson at 400 GeV, A(400), and for a heavy Higgs boson at 660 GeV. An extension of the GM is needed to interpret the fermion couplings of A(400). Potentially interesting deviations are also observed in the ttW cross-section measurement, which naturally fit into this picture. None of them crosses the fatidic five s.d. evidence but the addition of these effects, consistent with GM, suggest that there are good hopes for solid discoveries at HL-LHC, which should boost the motivation for future machines. The GM model also provides a useful framework to estimate the rates expected for various channels at an $e^+e^-$ collider, together with the range of energies needed. ILC performances are used for a quantitative estimate of these rates for the prominent channels., Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS2021), 15-18 March 2021 and at ILC Workshop on Potential Experiments (ILCX2021), 26-29 October 2021. 27 pages, 16 figures

This paper intends to collect the various evidences observed by ATLAS and CMS within searches for heavy scalars and pseudocalars. These searches in tt, hZ, tautau and 2jets+W, obtain individual excesses in five channels, each at a modest level of significance, ~3 standard deviations, but, put together, give a strong evidence for a pseudoscalar at ~400 GeV. Preliminary interpretations are given which suggest that additional observations should appear in the HL-LHC phase., Comment: 7 pages 1 figure

This paper intends to collect available data on searches for scalar resonances at LHC. It is suggested that, in the absence of SUSY, the most compelling picture is the composite framework, with the idea that the lightest particles are composite scalars of the pseudo-Nambu-Goldstone type, emerging from a broken symmetry at a higher scale, the h(125) boson being one of them. Searches in two-photons, Z-photon, ZZ into 4 leptons, top, h and W pairs are reviewed. A recent search based on lepton tagging from a spectator W/Z is also discussed. Aside from the already well-known scalar observed by CMS and LEP2 at 96 GeV, I discuss the evidence and the interpretation for a possible resonance observed in ZZ around 700 GeV by CMS and ATLAS and some evidence for a CP-odd scalar at ~400 GeV. Future searches at HL-LHC and at $e^+e^-$ colliders are briefly sketched., Comment: 22 pages, 21 figures

A large, world-wide community of physicists is working to realise an exceptional physics program of energy-frontier, electron-positron collisions with the International Linear Collider (ILC). This program will begin with a central focus on high-precision and model-independent measurements of the Higgs boson couplings. This method of searching for new physics beyond the Standard Model is orthogonal to and complements the LHC physics program. The ILC at 250 GeV will also search for direct new physics in exotic Higgs decays and in pair-production of weakly interacting particles. Polarised electron and positron beams add unique opportunities to the physics reach. The ILC can be upgraded to higher energy, enabling precision studies of the top quark and measurement of the top Yukawa coupling and the Higgs self-coupling. The key accelerator technology, superconducting radio-frequency cavities, has matured. Optimised collider and detector designs, and associated physics analyses, were presented in the ILC Technical Design Report, signed by 2400 scientists. There is a strong interest in Japan to host this international effort. A detailed review of the many aspects of the project is nearing a conclusion in Japan. Now the Japanese government is preparing for a decision on the next phase of international negotiations, that could lead to a project start within a few years. The potential timeline of the ILC project includes an initial phase of about 4 years to obtain international agreements, complete engineering design and prepare construction, and form the requisite international collaboration, followed by a construction phase of 9 years.

The International Linear Collider (ILC) being proposed in Japan is an electron-positron linear collider with an initial energy of 250 GeV. The ILC accelerator is based on the technology of superconducting radio-frequency cavities. This technology has reached a mature stage in the European XFEL project and is now widely used. The ILC will start by measuring the Higgs properties, providing high-precision and model-independent determinations of its parameters. The ILC at 250 GeV will also search for direct new physics in exotic Higgs decays and in pair-production of weakly interacting particles. The use of polarised electron and positron beams opens new capabilities and scenarios that add to the physics reach. The ILC can be upgraded to higher energy, enabling precision studies of the top quark and measurement of the top Yukawa coupling and the Higgs self-coupling. The international -- including European -- interest for the project is very strong. Europe has participated in the ILC project since its early conception and plays a major role in its present development covering most of its scientific and technological aspects: physics studies, accelerator and detectors. The potential for a wide participation of European groups and laboratories is thus high, including important opportunities for European industry. Following decades of technical development, R&D, and design optimisation, the project is ready for construction and the European particle physics community, technological centers and industry are prepared to participate in this challenging endeavour.

This note intends to give an estimate on the sensitivity of the channel ee to ee at the future ILC250. At variance with other two fermion processes, the so-called Bhabha process is influenced by t-channel Z/photon exchange. In spite of the complexity of the resulting angular distribution of this process, one observes a good sensitivity to Zprime exchange, similar to those observed in annihilation channels. This feature is illustrated within the gauge-Higgs unification model, GHU, which shows an impressive indirect sensitivity to the mass of Zprime particles, up to about 20 TeV for the leptonic channels. Beam longitudinal polarisation and high luminosity are the key ingredients for this result. Measuring the Zprime ee coupling with the Bhabha process allows to measure separately Zprimemumu and Zprimetautau coupling, which serves for a precise test of lepton universality. Zprimebb and Zprimett couplings show good sensitivities to GHU. LHC and HE-LHC sensitivities are also discussed., Comment: 14 pages, 9 figures, 3 tables

With the data collected by LHC at 13 TeV, the CMS collaboration has searched for low mass resonances decaying into two photons. This has resulted in the observation of 3 sd excess around 95 GeV, reminiscent of an indication obtained at LEP2 by combining the Higgs boson searches of the four LEP experiments. These observations, marginally significant, motivate the present study which shows how HL-LHC and ILC250 could search for a radion, the lightest new particle predicted within the Randall Sundrum (RS) model. ILC operating at a centre of mass energy of 250 GeV and with an integrated luminosity surpassing LEP2 by three orders of magnitude, could become the ideal machine to study a light radion and to observe, with very high accuracy, how it mixes with the Higgs boson and modifies the various couplings., Comment: 13 pages, 13 figures

This note is an attempt to interpret some excesses, not yet significant due to systematics, observed by ATLAS and CMS in various analyses related to the standard channels ttH, ttZ and ttW. It is argued, within a composite interpretation of top particles, that such excesses are not necessarily related to these channels themselves, although this is not excluded, but due to the underlying presence of either vector-like heavy quarks tprime,bprime or to final states as predicted in composite theories. The outcome of this discussion is that although it will not be easy to reach an exclusive interpretation, the data collected at 13 TeV may establish the origin of this effect as coming from the four top quark topology., Comment: 10 pages, 7 figures

The radion scalar field might be the lightest new particle predicted by extra-dimensional extensions of the Standard Model. It could thus lead to the first signatures of new physics at the LHC collider. We perform a complete study of the radion production in association with the Z gauge boson in the custodially protected warped model with a brane-localised Higgs boson addressing the gauge hierarchy problem. Radion-Higgs mixing effects are present. Such a radion production receives possibly resonant contributions from the Kaluza-Klein excitations of the Z boson as well as the extra neutral gauge boson (Z'). All the exchange and mixing effects induced by those heavy bosons are taken into account in the radion coupling and rate calculations. The investigation of the considered radion production at LHC allows to be sensitive to some parts of the parameter space but only the ILC program at high luminosity would cover most of the theoretically allowed parameter space via the studied reaction. Complementary tests of the same theoretical parameters can be realised through the high accuracy measurements of the Higgs couplings at ILC. The generic sensitivity limits on the rates discussed for the LHC and ILC potential reach can be applied to the searches for other (light) exotic scalar bosons., Comment: 28 pages, 10 figures

If the gamma-gamma resonance at 750 GeV suggested by 2015 LHC data turns out to be a real effect, what are the implications for the physics case and upgrade path of the International Linear Collider? Whether or not the resonance is confirmed, this question provides an interesting case study testing the robustness of the ILC physics case. In this note, we address this question with two points: (1) Almost all models proposed for the new 750 GeV particle require additional new particles with electroweak couplings. The key elements of the 500 GeV ILC physics program---precision measurements of the Higgs boson, the top quark, and 4-fermion interactions---will powerfully discriminate among these models. This information will be important in conjunction with new LHC data, or alone, if the new particles accompanying the 750 GeV resonance are beyond the mass reach of the LHC. (2) Over a longer term, the energy upgrade of the ILC to 1 TeV already discussed in the ILC TDR will enable experiments in gamma-gamma and e+e- collisions to directly produce and study the 750 GeV particle from these unique initial states., Comment: 39 pages, 5 figures, 5 tables; v2: some references added

We propose an interpretation of the diboson excess recently observed by the ATLAS and CMS collaborations in terms of Kaluza-Klein excitations of electroweak gauge bosons stemming from a realization of a warped extra-dimensional model that is protected by a custodial symmetry. Besides accounting for the LHC diboson data, this scenario also leads to an explanation of the anomalies that have been observed in the measurements of the forward-backward asymmetries for bottom quarks at LEP and top quarks at the Tevatron., Comment: 10 pages, 2 figures

We propose to generalize the extensions of the Standard Model where the $Z$ boson serves as a mediator between the Standard Model sector and the dark sector $\chi$. We show that, like in the Higgs portal case, the combined constraints from the recent direct searches restrict severely the nature of the coupling of the dark matter to the $Z$ boson and set a limit $m_\chi \gtrsim 200$ GeV (except in a very narrow region around the $Z-$pole region). Using complementarity between spin dependent, spin independent and FERMI limits, we predict the nature of this coupling, more specifically the axial/vectorial ratio that respects a thermal dark matter coupled through a $Z$-portal while not being excluded by the current observations. We also show that the next generation of experiments of the type LZ or XENON1T will test Z-portal scenario for dark matter mass up to 2 TeV. The condition of a thermal dark matter naturally predicts the spin--dependent scattering cross section on the neutron to be $\sigma^{SD}_{\chi n} \simeq 10^{-40} \mrm{cm^2}$, which then becomes a clear prediction of the model and a signature testable in the near future experiments., Comment: 19 pages, 7 figures

Dark Matter (DM) detection prospects at future e+e- colliders are reviewed under the assumption that DM particles are fermions of the Majorana or Dirac type. Although the discussion is quite general, one will keep in mind the recently proposed candidate based on an excess of energetic photons observed in the center of our Galaxy with the Fermi-LAT satellite. If one assume that DM couples to a Zprime, using radiative return events e+e-->XX+photon, one could observe a spectacular signal at a TeV e+e- collider. This result relies on the ability of using highly polarized beams to eliminate a large part of the W exchange background. Prospects of discovery at LHC using mono-jets are also discussed and appear promising. In the second part, one assumes that DM particles annihilate through Higgs particles, either the SM boson h or MSSM type bosons called H, A. A promising scenario emerges, where one has e+e-->HA, with H decaying into hh, while A decays invisibly in most of the cases., Comment: 17 pages, 5 figures

Various BSM models predict large deviations of the top electroweak couplings. Many examples will be given emphasizing the need for precise and model independent measurements of these couplings. Here I address the question of compatibility between theoretical predictions and the LEP/SLC/Tevatron constraints which, through loop effects, allow setting very significant constraints on these predictions. A Randall Sundrum inspired prediction will be discussed in more details. Finally the prospects offered by LHC and ILC measurements for top EW couplings are briefly reviewed.

In this note, I examine the possible consequences for high energy colliders of a Z-prime interpretation of the LHCb anomaly observed in the K*mu+mu- final state. Two examples are elaborated in the framework of the so-called 331 model. In the first one it is shown that LEP2 provides the tightest lower mass limit for the Z-prime boson, above 8 TeV, while in the second one the lower mass limit is set by ATLAS/CMS to about 3 TeV. It is then shown that precision measurements at ILC 500 GeV can fully explore the underlying structure of the model by measuring the fermion final states separately: leptons, charm, beauty and top final states. Z-prime-Z mixing can also be substantial, thus leading to possible effects almost observable at LEP1 and which can be precisely measured at GigaZ. Discovery prospects for heavy bosons and heavy fermions at LHC are also discussed .

The cross section for production at the 7 TeV LHC has been measured. For the first time it therefore becomes possible to measure Z couplings to top quarks. Interpreting the notorious LEP1 anomaly on Z couplings to b quarks in terms of an extra-dimension model, one expects an excess, as large as a factor 2, on the rate which may already become significant with the LHC at 8 TeV data. Other schemes are reviewed which also predict deviations of couplings. The size of the effect and a dramatic increase of the top quarks with the right chirality should confirm our interpretation of the underlying mechanism. Complementary signals observable at LHC are also briefly reviewed., Comment: 7 pages, 2 figures

From the warped extra-dimensional model interpretation of the two forward-backward asymmetries observed on heavy quarks at LEP1, AFBb, and at Tevatron, AFBt, one predicts that LHC could observe, with the luminosity collected in 2011-2012, significant excesses in the diboson production for large invariant masses of the Z+W system, mZW, and, the W+W system, mWW., Comment: 15 pages, 8 figures

A study of top quark production at the future International Linear Collider, ILC, with a centre-of-mass energy of 500 GeV is presented. The emphasis is put on determining the sensitivity to physics beyond the Standard Model. The analysis has been carried out with a full simulation of the ILD detector. Both, the forward-backward asymmetry and the left-right asymmetry can be determined to a precision of about 1% to 1.5%. The analysis points out an ambiguity which arises in case of the production of top-quarks with left-handed helicity.

The CDF and D0 experiments have reported on the measurement of the forward-backward asymmetry of top quark pair production at the Tevatron and the result is that it is more than 2 standard deviations above the predicted value in the Standard Model. This has to be added to the longstanding anomaly in the forward-backward asymmetry for bottom quark production at LEP which is 3 standard deviations different from the Standard Model value. The discrepancy in the bottom asymmetry can be accounted for by the contributions of Kaluza-Klein excitations of electroweak gauge bosons at LEP in warped extra dimensional models in which the fermions are localized differently along the extra dimension so that the gauge interactions of heavy third generation fermions are naturally different from that of light fermions. In this paper, we show that it is more difficult to elaborate a model generating a significant top asymmetry in a similar way -- through exchanges of Kaluza-Klein gluons at the Tevatron -- due to the indirect constraints originating from precision electroweak data., Comment: 4 pages, 1 figure, published version

Objective: Mapping of transrectal ultrasonographic (TRUS) prostate biopsies is of fundamental importance for either diagnostic purposes or the management and treatment of prostate cancer, but the localization of the cores seems inaccurate. Our objective was to evaluate the capacities of an operator to plan transrectal prostate biopsies under 2-dimensional TRUS guidance using a registration algorithm to represent the localization of biopsies in a reference 3-dimensional ultrasonographic volume. Methods: Thirty-two patients underwent a series of 12 prostate biopsies under local anesthesia performed by 1 operator using a TRUS probe combined with specific third-party software to verify that the biopsies were indeed conducted within the planned targets. RESULTS: The operator reached 71% of the planned targets with substantial variability that depended on their localization (100% success rate for targets in the middle and right parasagittal parts versus 53% for targets in the left lateral base). Feedback from this system after each series of biopsies enabled the operator to significantly improve his dexterity over the course of time (first 16 patients: median score, 7 of 10 and cumulated median biopsy length in targets of 90 mm; last 16 patients, median score, 9 of 10 and a cumulated median length of 121 mm; P = .046). Conclusions: In addition to being a useful tool to improve the distribution of prostate biopsies, the potential of this system is above all the preparation of a detailed "map" of each patient showing biopsy zones without substantial changes in routine clinical practices.

Precision measurements of SM Higgs recoil mass and cross-section are performed with the Higgs-Strahlung process ee -> Zh, with Z -> mumu and Z -> ee at 230 GeV and 250 GeV center of mass energies, presuming Mh=120GeV, assuming the integrated luminosity is 500 1/fb, based on full simulations of several detector models for the ILC. Results are given and compared in this article, of the two center of mass energies, and of several detector models. According to the studies, the Higgs mass can be determined with a statistical error of 39 MeV and 3.6% statistical error for the cross-section., Comment: LCWS08 Proceeding

A fourth generation could provide, within SUSY, a solution to baryogenesis at the EW scale. It is allowed by precision measurements. Available data from Tevatron already restrict the allowed domain of parameters for the new quarks and the Higgs boson. There are some indications from b->s transitions which could be interpreted within an extension of the CKM matrix to 4x4, in particular CPV in the Bs time-dependence for the J/Psi-Phi mode observed at Tevatron. If confirmed with more data the 4MSSM interpretation predicts a very interesting scenario for LHC and a TeV LC., Comment: Linear Collider ECFA Warsaw June 2008

Assuming that first significant results from LHC become available, this presentation assumes 4 different scenarios and discuss the implications for ILC

Background and Purpose: Percutaneous renal access in the context of percutaneous nephrolithotomy (PCNL) is a difficult technique, requiring rapid and precise access to a particular calix. We present a computerized system designed to improve percutaneous renal access by projecting the ultrasound puncture tract onto fluoroscopic images. Materials and Methods: The system consists of a computer and a localizer allowing spatial localization of the position of the various instruments. Without any human intervention, the ultrasound nephrostomy tract is superimposed in real time onto fluoroscopic images acquired in various views. Results: We tested our approach by laboratory experiments on a phantom. Also, after approval by our institution's Ethics Committee, we validated this technique in the operating room during PCNL in one patient. Conclusion: Our system is reliable, and the absence of image-processing procedures makes it robust. We have initiated a prospective study to validate this technique both for PCNL specialists and as a learning tool.

This document is meant to provide semi-quantitative arguments to evaluate the luminosity needed at ILC to achieve a precise measurement of the Higgs mass, width and invisible decays. It is shown that for mH=120 GeV, one can save an order of magnitude on the luminosity needed to achieve a given precision on the Higgs mass, as compared to what can be obtained at \sqrt s=350 GeV, by running near threshold. Since the recoil mass resolution near threshold is independent of the Higgs mass, one can also access the Higgs width for masses above 170 GeV. This strategy of running just above threshold is also optimal to measure or set upper limits on the Higgs invisible branching ratio. Two MSSM scenarios are presented to illustrate the potential interest of an optimized recoil mass resolution. A simplified description of the various experimental mechanisms affecting this type of measurement is presented: detector resolution for leptons and jets, luminosity and beamstrahlung energy dependence, initial and final radiation of the involved leptons., Comment: Work presented at the International Collider Physics and Detector, ECFA Workshop, Valencia, Spain, November 7-10, 2006

It is notorious that, contrary to all other precision electroweak data, the forward-backward asymmetry for b quarks $A_{FB}^b$ measured in Z decays at LEP1 is nearly three standard deviations away from the predicted value in the Standard Model; significant deviations also occur in measurements of the asymmetry off the Z pole. We show that these discrepancies can be resolved in a variant of the Randall-Sundrum extra-dimensional model in which the gauge structure is extended to $SU(2)_L \times SU(2)_R \times U(1)_X$ to allow for relatively light Kaluza-Klein excitations of the gauge bosons. In this scenario, the fermions are localized differently along the extra dimension, in order to generate the fermion mass hierarchies, so that the electroweak interactions for the heavy third generation fermions are naturally different from the light fermion ones. We show that the mixing between the Z boson with the Kaluza-Klein excitations allows to explain the $A_{FB}^b$ anomaly without affecting (and even improving) the agreement of the other precision observables, including the $Z \to bb$ partial decay width, with experimental data. Some implications of this scenario for the ILC are summarized., Comment: 23 pages, 5 figures