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

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

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

The Higgs Sector of the Next-to-Minimal Supersymmetric Standard Model

The Higgs boson spectrum of the Next-to-Minimal Supersymmetric Standard Model is examined. The model includes a singlet Higgs field S in addition to the two Higgs doublets of the minimal extension. `Natural' values of the parameters of the model are motivated by their renormalization group running and the vacuum stability. The qualitative features of the Higgs boson masses are dependent on how strongly the Peccei-Quinn U(1) symmetry of the model is broken, measured by the self-coupling of the singlet field in the superpotential. We explore the Higgs boson masses and their couplings to gauge bosons for various representative scenarios.Comment: 32 pages with 12 figures; references and parameters updated; a few minor comments adde

Identifying the Higgs Spin and Parity in Decays to Z Pairs

Higgs decays to Z boson pairs may be exploited to determine spin and parity of the Higgs boson, a method complementary to spin-parity measurements in Higgs-strahlung. For a Higgs mass above the on-shell ZZ decay threshold, a model-independent analysis can be performed, but only by making use of additional angular correlation effects in gluon-gluon fusion at the LHC and gamma-gamma fusion at linear colliders. In the intermediate mass range, in which the Higgs boson decays into pairs of real and virtual Z bosons, threshold effects and angular correlations, parallel to Higgs-strahlung, may be adopted to determine spin and parity, though high event rates will be required for the analysis in practice.Comment: 14 pages, 2 postscript figure

Gold-plated processes at photon colliders

We review the most important topics and objectives of the physics program of the gamma-gamma, gamma-electron collider (photon collider) option for an e+e- linear collider.Comment: 36 pages, Latex, 11 figures(ps,eps), Talk at Intern. Workshop on High Energy Photon Colliders; June 14-17, 2000, DESY, Hamburg, Germany; to be published in Nucl. Instr. and Methods

Higgs signals and hard photons at the Next Linear Collider: the ZZZZ-fusion channel in the Standard Model

In this paper, we extend the analyses carried out in a previous article for $WW$-fusion to the case of Higgs production via $ZZ$-fusion within the Standard Model at the Next Linear Collider, in presence of electromagnetic radiation due real photon emission. Calculations are carried out at tree-level and rates of the leading order (LO) processes e^+e^-\rightarrow e^+e^- H \ar e^+e^- b\bar b and e^+e^-\rightarrow e^+e^- H \ar e^+e^- WW \ar e^+e^- \mathrm{jjjj} are compared to those of the next-to-leading order (NLO) reactions e^+e^-\rightarrow e^+e^- H (\gamma)\ar e^+e^- b\bar b \gamma and e^+e^-\rightarrow e^+e^- H (\gamma)\ar e^+e^- WW (\gamma) \ar e^+e^- \mathrm{jjjj}\gamma, in the case of energetic and isolated photons.Comment: 12 pages, LaTeX, 5 PostScript figures embedded using epsfig and bitmapped at 100dpi, complete paper including high definition figures available at ftp://axpa.hep.phy.cam.ac.uk/stefano/cavendish_9611.ps or at http://www.hep.phy.cam.ac.uk/theory/papers

e+e−→H+H−e^+e^-\to H^+H^- signals at LEP2 energies in the Minimal Supersymmetric Standard Model

In this paper we compare $H^+H^-$ and $W^+W^-$ into four-fermion production at centre-of-mass energies typical of LEP2 and somewhat larger. The theoretical framework considered is the Minimal Supersymmetric Standard Model. The interest in exploiting the $e^+e^-$ CERN collider at values of $\sqrt s$ greater than 192 GeV could come from the discovery of Supersymmetric signals during runs at lower energy. If these indicate that a charged Higgs boson exists in the mass range \MH\approx95-105 GeV, then a few years of running at $\sqrt s=205-215$ GeV and nominal luminosity could make the detection of such scalars feasible, in the purely leptonic channel $\tau\nu_\tau\tau\nu_\tau$ and, for small \tb's, also in the semi-hadronic(leptonic) one ${jj}\tau\nu_\tau$. Charged Higgs bosons of the above nature cannot be produced by the beam energies approved at present for LEP2. However, if runs beyond the so-called `192 GeV cryogenic limit' will be approved by the CERN Council, our selection procedure will enable us to establish the presence, or otherwise, of charged Higgs bosons in the mentioned mass rangeComment: 30 pages, latex, epsfig, 12 postscript figures, complete paper available at ftp://axpa.hep.phy.cam.ac.uk/stefano/cavendish_9615 and at http://www.hep.phy.cam.ac.uk/theory/papers