Round-table: Discussion on Future Machines

With the discovery of the Higgs Boson Self-consistent model (SM) accounting for all Particle Physics phenomena at presently accessible energy Self-consistent model (SM) accounting for all Particle Physics phenomena at presently accessible energy but does not explain major issues Mass of neutrino (in the most general way) Baryon Asymmetry of Universe Dark Matter, Dark Energy Unification of all interactions Unification of all interactions New Physics must exist … but at which energy scale? Precision Frontier: Ultra- precise measurements of the SM and rare process studies Precision Frontier: Ultra- precise measurements of the SM and rare process studies Energy Frontier: Direct Exploration of Higher Energy Scales Energy Frontier: Direct Exploration of Higher Energy Scales

Both frontiers require very large scale e + e - and h-h facilities  Large resources (human and technical) needed Large resources (human and technical) needed  Large costs (probably at the ten or tens G€) Large costs (probably at the ten or tens G€) At most 1 such large project in the world Its construction, operation, upgrades will span over the next years Vital to make the right choice (no second thought once started) Essential to include all reasonably obtainable information in the decision making process

 Results from operating facilities  Accelerator Design Studies  Physics and Detector Studies LHC TeV -Physics :mass hierarchy and maybe first CP results -Physics :mass hierarchy and maybe first CP results Flavor LHC and superKEKB FCC/CepC studies complementing ILC/CLIC studies Studies of Long Baseline  facilities 2018: Seems an appropriate time scale for updating the Strategy in Europe Concentrate most European efforts toward a single very large scale project ( for HE/precision frontier) Necessary for making an educated decision

Recommendation #2 High-priority large-scale scientific activities d) To stay at the forefront of particle physics, Europe needs to be in a position to propose an ambitious post-LHC accelerator project at CERN by the time of the next Strategy update, when physics results from the LHC running at 14 TeV will be available. CERN should undertake design studies for accelerator projects in a global context, with emphasis on proton-proton and electron-positron high-energy frontier machines.These design studies should be coupled to a vigorous accelerator R&D programme, including high-field magnets and high-gradient accelerating structures, in collaboration with national institutes, laboratories and universities worldwide. CERN should undertake design studies for accelerator projects in a global context, with emphasis on proton-proton and electron-positron high-energy frontier machines. These design studies should be coupled to a vigorous accelerator R&D programme, including high-field magnets and high-gradient accelerating structures, in collaboration with national institutes, laboratories and universities worldwide. Recommendation #1 c) The discovery of the Higgs boson is the start of a major programme of work to measure this particle’s properties with the highest possible precision for testing the validity of the Standard Model and to search for further new physics at the energy frontier. The LHC is in a unique position to pursue this programme. Europe’s top priority should be the exploitation of the full potential of the LHC, including the high-luminosity upgrade of the machine and detectors with a view to collecting ten times more data than in the initial design, by around 2030 Europe’s top priority should be the exploitation of the full potential of the LHC, including the high-luminosity upgrade of the machine and detectors with a view to collecting ten times more data than in the initial design, by around This upgrade programme will also provide further exciting opportunities for the study of flavour physics and the quark-gluon plasma.

Recommendation #4 High-priority large-scale scientific activities f) Rapid progress in neutrino oscillation physics, with significant European involvement, has established a strong scientific case for a long-baseline neutrino programme exploring CP violation and the mass hierarchy in the neutrino sector. CERN should develop a neutrino programme to pave the way for a substantial European role in future long-baseline experiments. Europe should explore the possibility of major participation in leading long-baseline neutrino projects in the US and Japan. Recommendation #3 e) There is a strong scientific case for an electron-positron collider, complementary to the LHC, that can study the properties of the Higgs boson and other particles with unprecedented precision and whose energy can be upgraded. The Technical Design Report of the International Linear Collider (ILC) has been completed, with large European participation. The initiative from the Japanese particle physics community to host the ILC in Japan is most welcome, and European groups are eager to participate. Europe looks forward to a proposal from Japan to discuss a possible participation.

 In the meantime, vital to strengthen R&D both for conceptual Designs and technical prototyping  FCC (Europe) and CepC (China) Designs FCC (Europe) and CepC (China) Designs FCC (Europe) and CepC (China) Designs  Main R&D areas Main R&D areas Main R&D areas  Magnet R&D: Nb 3 Sn and HTS Magnet R&D: Nb 3 Sn and HTS Magnet R&D: Nb 3 Sn and HTS  High Gradient in CW and pulsed modes High Gradient in CW and pulsed modes High Gradient in CW and pulsed modes  SC: > 40 MV/m (pulsed), >20 MV/m (CW) SC: > 40 MV/m (pulsed), >20 MV/m (CW) SC: > 40 MV/m (pulsed), >20 MV/m (CW)  NC: >100 MV/m (12GHz), >10 GV/m (PWFA) NC: >100 MV/m (12GHz), >10 GV/m (PWFA) NC: >100 MV/m (12GHz), >10 GV/m (PWFA) ESGARD is overseeing a set of project to be submitted to the EC  FCC  First e - PWF accelerator (1-5 GeV) for pilot applications  -SB using ESS infrastructure  Resonant L-PWF acceleration scheme  High brightness (B > A /m 2 ) electron beam with Beam Driven PWFA DS R&D

Future large scale accelerators for Particle Physics (1/3) p-p collider FFC- hh (VHE-LHC) in km tunnel LEP/LHC Muti-TeV e + e - Linear Colliders (CLIC) pp Colliders (HE-LHC, VHE-LHC,…) Muon Colliders ( -Fact. as possible 1 st step HE-Frontier Colliders Plasma Colliders …for HE-physics and -Frontier exploration up to 3 TeV up to 100 TeV up to 10 TeV > 5 TeV

FCC-ee (TLEP) in km tunnel LEP/LHC Linear e + e - Colliders (ILC, CLIC)  Colliders ( SAPPHIRE, SILC, CLICHE, HFiTT ) Muon Colliders ( -Fact. as possible 1 st step Circular e + e - Colliders (TLEP, super TRISTAN, CEPC…) ~14kH/year ~400kH/year (4 det.) ~10kH/year ~10kH/year (2det.) …from electroweak high precision tests to Higgs studies <1 TeV ~160 GeV ~126 GeV up to 400 GeV SM/Higgs Factories laser~5J, ~100kHz  + +  - - H Future large scale accelerators for Particle Physics (2/3)

superB e + e - Factory … and Flavor physics … L= L= cm -2 s -1 >10 10 B/year SuperKEKB Multi- MW SC cavities 5-10 GeV  Goal: >10 21  y stored Fast accumulator target/horn station ν Flavor Factories ESS based 5MW p-beam super Beams (T2HK, LBNE, LNBO…) 1.6x10 16 pot/s Future large scale accelerators for Particle Physics (1/3)