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J. List

Publications and source records attributed to J. List.

36 records · Page 2Linked to original sources
arXiv2016

LHCSki 2016 - A First Discussion of 13 TeV Results

These are the proceedings of the LHCSki 2016 workshop "A First Discussion of 13 TeV Results" that has been held at the Obergurgl Universitätszentrum, Tirol, Austria, April 10 - 15, 2016. In this workshop the consequences of the most recent results from the LHC have been discussed, with a focus also on the interplay with dark matter physics, flavor physics, and precision measurements. Contributions from the workshop speakers have been compiled into this document.

hep-ph↗
arXiv2016

Top physics at high-energy lepton colliders

A summary is presented of the workshop "top physics at linear colliders" that was held at IFIC Valencia from the 30th of June to the 3rd July 2015. We present an up-to-date status report of studies into the potential for top quark physics of lepton colliders with an energy reach that exceeds the top quark pair production threshold, with a focus on the linear collider projects ILC and CLIC. This summary shows that such projects can offer very competitive determinations of top quark properties (mass, width) and its interactions with other Standard Model particles, in particular electroweak gauge bosons and the Higgs boson. In both areas the prospects exceed the LHC potential significantly - often by an order of magnitude.

hep-ex↗
arXiv2015

500 GeV ILC Operating Scenarios

The ILC Technical Design Report documents the design of a 500 GeV linear collider, but does not specify the center-of-mass energy steps of operation for the collider. The ILC Parameters Joint Working Group has studied possible running scenarios, including a realistic estimate of the real time accumulation of integrated luminosity based on ramp-up and upgrade processes, and considered the evolution of the physics outcomes. These physics goals include Higgs precision measurements, top quark measurements and searches for new physics. We present an "optimized" operating scenario and the anticipated evolution of the precision of the ILC measurements.

hep-ex↗
arXiv2015

Non-Simplified SUSY: Stau-Coannihilation at LHC and ILC

If new phenomena beyond the Standard Model will be discovered at the LHC, the properties of the new particles could be determined with data from the High-Luminosity LHC and from a future linear collider like the ILC. We discuss the possible interplay between measurements at the two accelerators in a concrete example, namely a full SUSY model which features a small stau_1-LSP mass difference. Various channels have been studied using the Snowmass 2013 combined LHC detector implementation in the Delphes simulation package, as well as simulations of the ILD detector concept from the Technical Design Report. We investigate both the LHC and ILC capabilities for discovery, separation and identification of various parts of the spectrum. While some parts would be discovered at the LHC, there is substantial room for further discoveries at the ILC. We finally highlight examples where the precise knowledge about the lower part of the mass spectrum which could be acquired at the ILC would enable a more in-depth analysis of the LHC data with respect to the heavier states.

hep-ph↗
arXiv2015

Physics at the e+ e- Linear Collider

A comprehensive review of physics at an e+e- Linear Collider in the energy range of sqrt{s}=92 GeV--3 TeV is presented in view of recent and expected LHC results, experiments from low energy as well as astroparticle physics.The report focuses in particular on Higgs boson, Top quark and electroweak precision physics, but also discusses several models of beyond the Standard Model physics such as Supersymmetry, little Higgs models and extra gauge bosons. The connection to cosmology has been analyzed as well.

hep-ph↗
arXiv2015

ILC Operating Scenarios

The ILC Technical Design Report documents the design for the construction of a linear collider which can be operated at energies up to 500 GeV. This report summarizes the outcome of a study of possible running scenarios, including a realistic estimate of the real time accumulation of integrated luminosity based on ramp-up and upgrade processes. The evolution of the physics outcomes is emphasized, including running initially at 500 GeV, then at 350 GeV and 250 GeV. The running scenarios have been chosen to optimize the Higgs precision measurements and top physics while searching for evidence for signals beyond the standard model, including dark matter. In addition to the certain precision physics on the Higgs and top that is the main focus of this study, there are scientific motivations that indicate the possibility for discoveries of new particles in the upcoming operations of the LHC or the early operation of the ILC. Follow-up studies of such discoveries could alter the plan for the centre-of-mass collision energy of the ILC and expand the scientific impact of the ILC physics program. It is envisioned that a decision on a possible energy upgrade would be taken near the end of the twenty year period considered in this report.

hep-ex↗
arXiv2014

Higgs Working Group Report of the Snowmass 2013 Community Planning Study

This report summarizes the work of the Energy Frontier Higgs Boson working group of the 2013 Community Summer Study (Snowmass). We identify the key elements of a precision Higgs physics program and document the physics potential of future experimental facilities as elucidated during the Snowmass study. We study Higgs couplings to gauge boson and fermion pairs, double Higgs production for the Higgs self-coupling, its quantum numbers and $CP$-mixing in Higgs couplings, the Higgs mass and total width, and prospects for direct searches for additional Higgs bosons in extensions of the Standard Model. Our report includes projections of measurement capabilities from detailed studies of the Compact Linear Collider (CLIC), a Gamma-Gamma Collider, the International Linear Collider (ILC), the Large Hadron Collider High-Luminosity Upgrade (HL-LHC), Very Large Hadron Colliders up to 100 TeV (VLHC), a Muon Collider, and a Triple-Large Electron Positron Collider (TLEP).

hep-ex↗
arXiv2013

Non-Simplified SUSY: stau-Coannihilation at LHC and ILC

Simplified models have become a widely used and important tool to cover the more diverse phenomenology beyond constrained SUSY models. However, they come with a substantial number of caveats themselves, and great care needs to be taken when drawing conclusions from limits based on the simplified approach. To illustrate this issue with a concrete example, we examine the applicability of simplified model results to a series of full SUSY model points which all feature a small stau-LSP mass difference, and are compatible with electroweak and flavor precision observables as well as current LHC results. Various channels have been studied using the Snowmass Combined LHC detector implementation in the Delphes simulation package, as well as the Letter of Intent or Technical Design Report simulations of the ILD detector concept at the ILC. We investigated both the LHC and ILC capabilities for discovery, separation and identification of all parts of the spectrum. While parts of the spectrum would be discovered at the LHC, there is substantial room for further discoveries and property determination at the ILC.

hep-ph↗
arXiv2011

Time evolution of ground motion-dependent depolarisation at linear colliders

Future linear colliders plan to collide polarised beams and the planned physics reach requires knowledge of the state of polarisation as precisely as possible. The polarised beams can undergo depolarisation due to various mechanisms. In order to quantify the uncertainty due to depolarisation, spin tracking simulations in the International Linear Collider (ILC) Beam Delivery System (BDS) and at the Interaction Point (IP) have been performed. Spin tracking in the BDS was achieved using the BMAD subroutine library, and the CAIN program was used to do spin tracking through the beam-beam collision. Assuming initially aligned beamline elements in the BDS, a ground motion model was applied to obtain realistic random misalignments over various time scales. Depolarisation at the level of 0.1% occurs within a day of ground motion at a noisy site. Depolarisation at the IP also exceeds 0.1% for the nominal parameter sets for both the ILC and for the Compact Linear Collider (CLIC). Theoretical work is underway to include radiative corrections in the depolarisation processes and simulation of the depolarisation through the entire collider is envisaged.

physics.acc-ph↗
arXiv2009

Polarimeters and Energy Spectrometers for the ILC Beam Delivery System

Any future high energy e+e- linear collider aims at precision measurements of Standard Model quantities as well as of new, not yet discovered phenomena. In order to pursue this physics programme, excellent detectors at the interaction region have to be complemented by beam diagnostics of unprecedented precision. This article gives an overview of current plans and issues for polarimeters and energy spectrometers at the International Linear Collider, which have been designed to fulfill the precision goals at a large range of beam energies from 45.6 GeV at the Z pole up to 250 GeV or, as an upgrade, up to 500 GeV.

physics.ins-det↗
arXiv2009

Beam Polarization at the ILC: the Physics Impact and the Accelerator Solutions

In this contribution accelerator solutions for polarized beams and their impact on physics measurements are discussed. Focus are physics requirements for precision polarimetry near the interaction point and their realization with polarized sources. Based on the ILC baseline programme as described in the Reference Design Report (RDR), recent developments are discussed and evaluated taking into account physics runs at beam energies between 100 GeV and 250 GeV, as well as calibration runs on the Z-pole and options as the 1TeV upgrade and GigaZ.

physics.acc-ph↗
arXiv2009

WIMP Searches at the ILC using a model-independent Approach

In this note the ILC's capabilities for detecting WIMPs and measuring their properties are studied. The expected signal cross section is derived in a model-independent way from the observed relic density of Dark Matter. Signal events are detected by means of initial state radiation (ISR). The study is performed with a full simulation of the ILD detector. The results show that WIMPs are observable at the ILC if their coupling to electrons is not too small (O(0.1)). Their masses can be measured with a precision of 1 to 2 GeV. The accessible phase space can be increased significantly using polarised beams, especially if the positrons are polarised as well.

hep-ex↗
arXiv2008

Precision Polarimetry at the International Linear Collider

The International Linear Collider (ILC) will collide polarised electrons and positrons at beam energies of 45.6 GeV to 250 GeV and optionally up to 500 GeV. To fully exploit the physics potential of this machine, not only the luminosity and beam energy have to be known precisely, but also the polarisation of the particles has to be measured with an unprecedented precision of dP/P ~ 0.25% for both beams. An overall concept of high precision polarisation measurements at high beam energies will be presented. The focus will be on the polarimeters (up- and downstream of the e+e- interaction point) embedded in the ILC beam delivery system. Some challenges concerning the design of the Compton spectrometers and the appropriate Cherenkov detectors for each polarimeter are discussed. Detailed studies of photodetectors and their readout electronics are presented focusing specifically on the linearity of the device, since this is expected to be the limiting factor on the precision of the polarisation measurement at the ILC.

physics.ins-det↗
arXiv2008

Executive Summary of the Workshop on Polarisation and Beam Energy Measurements at the ILC

This note summarizes the results of the "Workshop on Polarisation and Beam Energy Measurements at the ILC", held at DESY (Zeuthen) April 9-11 2008. The topics for the workshop included (i) physics requirements, (ii) polarised sources and low energy polarimetry, (iii) BDS polarimeters, (iv) BDS energy spectrometers, and (v) physics-based measurements of beam polarisation and beam energy from collider data. Discussions focused on the current ILC baseline programme as described in the Reference Design Report (RDR), which includes physics runs at beam energies between 100 and 250 GeV, as well as calibration runs on the Z-pole. Electron polarisation of P_e- >~ 80% and positron polarisation of P_e+ >~ 30% are part of the baseline configuration of the machine. Energy and polarisation measurements for ILC options beyond the baseline, including Z-pole running and the 1 TeV energy upgrade, were also discussed.

physics.acc-ph↗
arXiv2007

Simulation Studies and Detector Scenarios for an ILC Polarimeter

High energy longitudinal electron polarimetry will be based on Compton scattering for the International Linear Collider. An unobtrusive measurement has to include a magnet chicane setup serving as a spectrometer. Current proposals make use of Cerenkov detectors for electron detection. A fast simulation has been developed to study the basic properties of scenarios for the polarimeter setup.

physics.ins-det↗
arXiv2007

Model-independent WIMP Searches at the ILC

We investigate the possibility to detect WIMPs at the ILC in a model-independent way using events with single photons. The study is done with a full detector simulation of the LDC detector and MarlinReco. It turns out that WIMPs are observable this way at the ILC if their coupling to electrons is not too small. Beam polarisation can increase the accessible phase space significantly.

hep-ex↗
arXiv2006

Physics at the International Linear Collider

The International Linear Collider (ILC) is the next large project in accelerator based particle physics. It is complementary to the LHC in many aspects. Measurements from both machines together will finally shed light onto the known deficiencies of the Standard Model of particle physics and allow to unveil a possible underlying more fundamental theory. Here, the possibilities of the ILC will be discussed with special emphasis on the Higgs sector and on topics with a strong connection to cosmological questions like extra dimensions or dark matter candidates.

hep-ex↗