SUSY parameter determination

The impact of the LHC, SLHC and the ILC on the precision of the determination of supersymmetric parameters is investigated. In particular, in the point SPS1a the measurements performed at the ILC will improve by an order of magnitude the precision obtained by the LHC alone. The SLHC with respect to the LHC has the potential to reduce the errors by a factor two.Comment: Invited talk at 2005 International Linear Collider Physics and Detector Workshop and Second ILC Accelerator Workshop, Snowmass, CO(Snowmass05) 3 pages, LaTe

ATLAS electromagnetic barrel calorimeter performance in recent testbeams

During the combined testbeam in summer 2004 a slice of the ATLAS barrel detector—including all detector sub systems from the inner tracker, the calorimetry to the muon system—was exposed to particle beams (electrons, pions, photons, muons) with different energies (1–350 GeV). The aim was to study the combined performance of the different detector sub systems in ATLAS-like conditions. We will present studies with different amounts of material in front of the calorimeter, representing various regions in the ATLAS detector, performance results from the electromagnetic calorimetry, including uniformity, resolution, and linearity as well as a discussion of the calibration scheme. The performance in the combined ATLAS-like set-up will be compared to the one obtained in stand-alone testbeams

Photon Production at the LHC

We review the last results on photon production at LHC by the ATLAS and CMS experiments obtained in proton-proton collisions with a center of mass energy of 7 TeV. We discuss the impact of prompt photon and photon-jet differential cross-sections, on the parton distribution function of the proton. Di-photon differential cross-sections are also presented as a function of the di-photon invariant mass, transverse momentum, azimuthal separation, and cos theta*

SFitter: Reconstructing the MSSM Lagrangian from LHC data

Once supersymmetry is found at the LHC, the question arises what are the fundamental parameters of the Lagrangian. The answer to this question should thereby not be biased by assumptions on high-scale models. SFitter is a tool designed for this task. Taking LHC (and possibly ILC) data as input it scans the TeV-scale MSSM parameter space using its new weighted Markov chain technique. Using this scan it determines a list of best-fitting parameter points. Additionally a log-likelihood map is calculated, which can be reduced to lower-dimensional Frequentist's profile likelihoods or Bayesian probability maps.Comment: Submitted for the SUSY07 proceedings, 4 pages, LaTeX, 4 eps figure

Double Higgs production at TeV Colliders in the Minimal Supersymmetric Standard Model

The reconstruction of the Higgs potential in the Minimal Supersymmetric Standard Model (MSSM) requires the measurement of the trilinear Higgs self-couplings. The `double Higgs production' subgroup has been investigating the possibility of detecting signatures of processes carrying a dependence on these vertices at the Large Hadron Collider (LHC) and future Linear Colliders (LCs). As reference reactions, we have chosen $gg\to hh$ and $e^+e^-\to h h Z$, respectively, where $h$ is the lightest of the MSSM Higgs bosons. In both cases, the $Hhh$ interaction is involved. For $m_H>2m_h$, the two reactions are resonant in the $H\to hh$ mode, providing cross sections which are detectable at both accelerators and strongly sensitive to the strength of the trilinear coupling involved. We explore this mass regime of the MSSM in the $h\to b\bar b$ decay channel, also accounting for irreducible background effects.Comment: LaTeX, 23 pages, 13 PostScript figures (contribution to the Summary Report of the Higgs WG, Workshop `Physics at TeV Colliders', Les Houches, France, 8-18 June 1999): some modifications to the bibliograph

Reconstruction of fundamental SUSY parameters at LHC and at a future linear collider

Presentation par R. LafayeUnveiling the mechanism leading to the breaking of supersymmetry is among the outstanding questions for future colliders. To achieve this goal, models will need to be scrutinized and their parameters assessed. Global fitting tools, like Fittino and SFitter, have been developed and set a robust framework for such analyses. Using the SPS1a snowmass point as an example for the SUSY and Higgs particles that could be observed at the LHC and at a future TeV Linear Collider, we have studied the determination and its precision of MSUGRA parameters from the measurements expected in this point. While the LHC will provide the first measurement of the parameters, the Linear Collider will increase their precision by an order of magnitude. However, when moving to the unconstrained weak-scale MSSM, measurements from the LHC, such as the gluino and squarks masses and couplings, and from the LC, such as charginos and high precision slepton mass measurements, are necessary to reconstruct the Lagrangian with the best available precision. Using a set of hypothetical measurements at LHC and at a future LC, we will show how these colliders probe different sectors of the MSSM Lagrangian and how this complementarity increases our handle on the determination of the weak-scale parameters of the Lagrangian. In fact, the combination of the measurements of the LHC and the LC is essential to probe the complete MSSM weak-scale lagrangian

Higgs look-alikes at the LHC

The discovery of a Higgs particle is possible in a variety of search channels at the LHC. However the true identity of any putative Higgs boson will at first remain ambiguous, until one has experimentally excluded other possible assignments of quantum numbers and couplings. We quantify to what degree one can discriminate a Standard Model Higgs boson from "look-alikes" at, or close to, the moment of discovery at the LHC. We focus on the fully-reconstructible "golden" decay mode to a pair of Z bosons and a four-lepton final state, simulating sPlot-weighted samples of signal and background events. Considering both on-shell and off-shell Z's, we show how to utilize the full decay information from the events, including the distributions and correlations of the five relevant angular variables. We demonstrate how the finite phase space acceptance of any LHC detector sculpts the decay distributions, a feature neglected in previous studies. We use likelihood ratios to discriminate a Standard Model Higgs from look-alikes with other spins or nonstandard parity, CP, or form factors. For a benchmark resonance mass of 200 GeV/c^2, we achieve a median expected discrimination significance of 3 sigma with as few as 19 events, and even better discrimination for the off-shell decays of a 145 GeV/c^2 resonance.Comment: 39 pages, 55 figures, typos fixed, figures added, and minor clarification

Higgs Physics at the Large Hadron Collider

In this talk I will begin by summarising the importance of the Higgs physics studies at the LHC. I will then give a short description of the pre-LHC constraints on the Higgs mass and the theoretical predictions for the LHC along with a discussion of the current experimental results, ending with prospects in the near future at the LHC. In addition to the material covered in the presented talk, I have included in the writeup, a critical appraisal of the theoretical uncertainties in the Higgs cross-sections at the Tevatron as well as a discussion of the recent experimental results from the LHC which have become available since the time of the workshop.Comment: LateX, 12 figures, 15 pages, Presented at the XIth Workshop on High Energy Physics Phenomenology, 2010, Ahmedabad, Indi