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Patrick Janot

Publications and source records attributed to Patrick Janot.

28 records · Page 2Linked to original sources
arXiv2019

Machine detector interface for the $e^+e^-$ future circular collider

The international Future Circular Collider (FCC) study aims at a design of $pp$, $e^+e^-$, $ep$ colliders to be built in a new 100 km tunnel in the Geneva region. The $e^+e^-$ collider (FCC-ee) has a centre of mass energy range between 90 (Z-pole) and 375 GeV (tt_bar). To reach such unprecedented energies and luminosities, the design of the interaction region is crucial. The crab-waist collision scheme has been chosen for the design and it will be compatible with all beam energies. In this paper we will describe the machine detector interface layout including the solenoid compensation scheme. We will describe how this layout fulfills all the requirements set by the parameters table and by the physical constraints. We will summarize the studies of the impact of the synchrotron radiation, the analysis of trapped modes and of the backgrounds induced by single beam and luminosity effects giving an estimate of the losses in the interaction region and in the detector.

physics.acc-ph↗
arXiv2019

Future strategies for the discovery and the precise measurement of the Higgs self coupling

The European Strategy for Particle Physics (ESSP) submitted in 2013 a deliberation document to the CERN council explaining that a lepton collider with "energies of 500\,GeV or higher could explore the Higgs properties further, for example the [Yukawa] coupling to the top quark, the [trilinear] self-coupling and the total width.". In view of the forthcoming ESPP update in 2020, variations on this qualitative theme have been applied, inaccurately, to the case of the ILC, to argue that an upgrade to 500\,GeV would allow the measurement of the Higgs potential and would increase the potential for new particle searches. As a consequence, the strategic question was raised again whether the FCC-ee design study ought to consider a 500 GeV energy upgrade. In this note, we revisit the ESSP 2013 statement quantitatively and find [...] that 500 GeV is not a particularly useful energy for the lepton colliders under consideration, especially for the FCC-ee. A 5 sigma demonstration of the existence of the Higgs self-coupling is within reach at the energies foreseen for the FCC-ee, with a moderate change of configuration, which certainly deserves consideration.

hep-ph↗
arXiv2019

Theory Requirements and Possibilities for the FCC-ee and other Future High Energy and Precision Frontier Lepton Colliders

The future lepton colliders proposed for the High Energy and Precision Frontier set stringent demands on theory. The most ambitious, broad-reaching and demanding project is the FCC-ee. We consider here the present status and requirements on precision calculations, possible ways forward and novel methods, to match the experimental accuracies expected at the FCC-ee. We conclude that the challenge can be tackled by a distributed collaborative effort in academic institutions around the world, provided sufficient support, which is estimated to about 500 man-years over the next 20 years.

hep-ph↗
arXiv2017

Direct measurement of alpha_QED(mZ) at the FCC-ee

When the measurements from the FCC-ee become available, an improved determination of the standard-model "input" parameters will be needed to fully exploit the new precision data towards either constraining or fitting the parameters of beyond-the-standard-model theories. Among these input parameters is the electromagnetic coupling constant estimated at the Z mass scale, alpha_QED(mZ). The measurement of the muon forward-backward asymmetry at the FCC-ee, just below and just above the Z pole, can be used to make a direct determination of alpha_QED(mZ) with an accuracy deemed adequate for an optimal use of the FCC-ee precision data.

hep-ph↗
arXiv2015

Precision measurements of the top quark couplings at the FCC

The design study of the Future Circular Colliders (FCC) in a 100-km ring in the Geneva area has started at CERN at the beginning of 2014, as an option for post-LHC particle accelerators. The study has an emphasis on proton-proton and electron-positron high-energy frontier machines. In the current plans, the first step of the FCC physics programme would exploit a high-luminosity e+e- collider called FCC-ee, with centre-of-mass energies ranging from below the Z pole to the t-tbar threshold and beyond, followed by 100\,TeV proton-proton collisions as ultimate goal. When combined, these two steps offer a large palette of complementary measurements and sensitivity for new physics. In particular, the association of the FCC-ee and the FCC-hh allows measurements of the top-quark electroweak and Yukawa couplings to be performed with unrivaled precision.

hep-ex↗
arXiv2015

Top-quark electroweak couplings at the FCC-ee

An optimal-observable analysis of the lepton angular and energy distributions from top-quark pair production with semi-leptonic decays in e+e- collisions is used to predict the potential sensitivity of the FCC-ee to the couplings of the top quark to the photon and the Z.

hep-ph↗
arXiv2012

Prospective Studies for LEP3 with the CMS Detector

On July 4, 2012, the discovery of a new boson, with mass around 125 GeV/c2 and with properties compatible with those of a standard-model Higgs boson, was announced at CERN. In this context, a high-luminosity electron-positron collider ring, operating in the LHC tunnel at a centre-of-mass energy of 240 GeV and called LEP3, becomes an attractive opportunity both from financial and scientific point of views. The performance and the suitability of the CMS detector are evaluated, with emphasis on an accurate measurement of the Higgs boson properties. The precision expected for the Higgs boson couplings is found to be significantly better than that predicted by Linear Collider studies.

hep-ex↗
arXiv2004

Closing the light sbottom mass window from a compilation of e+e- -> hadron data

The e+e- -> hadron cross section data from PEP, PETRA, TRISTAN, SLC and LEP, at centre-of-mass energies between 20 to 209 GeV, are analysed to search for the production of a pair of light sbottoms decaying hadronically via R-parity-violating couplings. This analysis allows the 95%C.L. exclusion of such a particle if its mass is below 7.5 GeV/c2. The light sbottom mass window is closed.

hep-ph↗
arXiv2003

The Light Gluino Mass Window Revisited

The precise measurements of the ``electroweak observables'' performed at LEP and SLC are well consistent with the standard model predictions. Deviations from the standard model arising from vacuum polarization diagrams (also called ``weak loop corrections'') have been constrained in a model-independent manner with the epsilon formalism. Within the same formalism, additional deviations from new physics production processes can also be constrained, still in a model-independent way. For instance, a 95% C.L. limit of Delta Gamma_had} < 3.9 MeV is set on the partial width of any purely hadronic exotic contribution to Z decays. When applied to the e+e- -> q qbar gluino gluino process, it allows an absolute lower limit to be set on the gluino mass, m_gluino > 6.3 GeV/c2 at 95% C.L., which definitely closes the so-called light gluino mass window.

hep-ph↗