Winter Institute: Selected Topics on the Phenomenology of Present and Future Colliders

Wednesday 1 Feb 2017, 11:00 → 16:30 Europe/Rome

High Energy Building, Seminar Room (Laboratori Nazionali di Frascati)

Gennaro Corcella (LNF)

Aim of the workshop:

This meeting aims at gathering theorists and experimentalists working in the Rome area in the field of collider physics. In an informal environment, we shall discuss several issues, which are relevant at present (SPS and LHC) and future accelerators. In particular, we shall debate the hunting for new physics with the NA62 detector, the coupling of the Higgs boson to gluons and top quarks, top-Higgs associated production and discuss the physics of future facilities, such as ILC and FCC, in both hadron-hadron and electron-positron modes.

1 Resolving Effective Couplings of the Higgs to Gluons and Tops

Inclusive Higgs measurements at the LHC have limited resolution on the gluon fusion loops, being unable to distinguish the long-distance contributions mediated by the top quark from possible short-distance new physics effects. Using an Effective Field Theory (EFT) approach we compare several proposed methods to lift this degeneracy, including tth and boosted, off-shell and double Higgs production, and perform detailed projections to the High-Luminosity LHC and a future hadron collider. We also point out the sensitivity of the off-shell channel to modifications of the top-Z couplings. By means of a general analysis we show that the reach is comparable to that of tree-level processes such as ttZ production. We also assess the regime of validity of the EFT, performing an explicit comparison for a simple extension of the Standard Model containing one vector-like quark.

Speaker: Ayan Paul (ROMA1)

Slides Ayan.pdf

2 Searching for New Physics with the NA62 experiment

K+ ->pi+ nu nu is one of the theoretically cleanest meson decays with which to look for indirect effects of new physics, as a complement to searches at the LHC. The NA62 experiment at the CERN SPS is designed to measure the branching ratio of this decay with 10% precision. NA62 took data in pilot runs in 2014 and 2015 and in a physics run in 2016. The experiment is also collecting data to search for exotic processes, like lepton flavour and number violation and decays of hidden-sector particles. An overview of the experiment, a first look at the data collected for the K+ ->pi +nu nu measurement, and prospects for search for exotic processes will be presented.

Speaker: Dr Silvia Martellotti (INFN Laboratori Nazionali di Frascati)

Slides WinterInstitute_NA62.pdf

13:00 Lunch break

3 Highlights on Higgs and top associated production at the LHC

Higgs and top associated production is the last of the main Higgs production channels which has still to be measured at the LHC. It is a channel of particular relevance because it gives an unique access to a model-independent measurement of the top quark Yukawa. In my talk I will review recent progresses in the theoretical predictions for the signal and for the background processes, and comment upon phenomenological applications that a measurement of ttH will make possible. Besides the dominant production mode in association with a top pair, I will also discuss recent progresses for the production of a Higgs boson and a single top, showing its relevance for the determination of the sign of the Yukawa coupling.

Speaker: Marco Zaro (LPTHE-UPMC)

4 High Energy Physics after LHC

As particle physics becomes more and more an international business, many laboratories ( or 'to be laboratories') conceive plans for future facilities at their locations. I would like to present a few basic facts on the several proposals (CEPC, CLIC, FCC, ILC, etc.) and discuss with the audience some possible outcomes for the HEP community if one (or more than one) of these projects will be realized. These considerations will be a base to start a discussion to start an informal discussion on the future facility (or facilities) that our field needs to continue to thrive.

Speaker: Dr Roberto Franceschini (CERN)