arXiv subjects
Publications and source records attributed to I. Hinchliffe.
This paper presents the method of combining parton shower formalism with perturbative calculations (matrix elements) in form of a Monte-Carlo algorithm for the process g g -> Z b anti-b,consistenlty including the heavy quark masses and overlap removal.
A standard file format is proposed to store process and event information, primarily output from parton-level event generators for further use by general-purpose ones. The information content is identical with what was already defined by the Les Houches Accord five years ago, but then in terms of Fortran commonblocks. This information is embedded in a minimal XML-style structure, for clarity and to simplify parsing.
High-precision analyses of supersymmetry parameters aim at reconstructing the fundamental supersymmetric theory and its breaking mechanism. A well defined theoretical framework is needed when higher-order corrections are included. We propose such a scheme, Supersymmetry Parameter Analysis SPA, based on a consistent set of conventions and input parameters. A repository for computer programs is provided which connect parameters in different schemes and relate the Lagrangian parameters to physical observables at LHC and high energy e+e- linear collider experiments, i.e., masses, mixings, decay widths and production cross sections for supersymmetric particles. In addition, programs for calculating high-precision low energy observables, the density of cold dark matter (CDM) in the universe as well as the cross sections for CDM search experiments are included. The SPA scheme still requires extended efforts on both the theoretical and experimental side before data can be evaluated in the future at the level of the desired precision. We take here an initial step of testing the SPA scheme by applying the techniques involved to a specific supersymmetry reference point.
We discuss possible searches for the new particles predicted by Little Higgs Models at the LHC. By using a simulation of the ATLAS detector, we demonstrate how the predicted quark, gauge bosons and additional Higgs bosons can be found and estimate the mass range over which their properties can be constrained.
We present a pedagogical review of particle physics models that are based on the noncommutativity of space-time, $[\hat{x}_μ,\hat{x}_ν]=i θ_{μν}$, with specific attention to the phenomenology these models predict in particle experiments either in existence or under development. We summarize results obtained for high energy scattering such as would occur for example in a future $e^+e^-$ linear collider with $\sqrt{s} = 500 GeV$, as well as low energy experiments such as those pertaining to elementary electric dipole moments and other $\cpviolng$ observables, and finally comment on the status of phenomenological work in cosmology and extra dimensions.
This Report documents the results obtained by the Working Group on Quantum ChromoDynamics and the Standard Model for the Workshop ``Physics at TeV Colliders'', Les Houches, France, 21 May - 1 June 2001. The account of uncertainties in Parton Distribution Functions is reviewed. Progresses in the description of multiparton final states at Next-to-Leading Order and the extension of calculations for precision QCD observables beyond this order are summarized. Various issues concerning the relevance of resummation for observables at TeV colliders is examined. Improvements to algorithms of jet reconstruction are discussed and predictions for diphoton and photon pi-zero production at the LHC are made for kinematic variables of interest regarding searches for a Higgs boson decaying into two photons. Finally, several improvements implemented in Monte-Carlo event generators are documented.
Report of the "Beyond the Standard Model" working group for the Workshop `Physics at TeV Colliders', Les Houches, France, 21 May - 1 June 2001. It consists of 18 separate parts: 1. Preface; 2. Theoretical Discussion; 3. Numerical Calculation of the mSUGRA and Higgs Spectrum; 4. Theoretical Uncertainties in Sparticle Mass Predictions; 5. High Mass Supersymmetry with High Energy Hadron Colliders; 6. SUSY with Heavy Scalars at LHC; 7. Inclusive Study of MSSM in CMS; 8. Establishing a No-Lose Theorem for NMSSM Higgs Boson Discovery at the LHC; 9. Effects of Supersymmetric Phases on Higgs Production in Association with Squark Pairs in the Minimal Supersymmetric Standard Model; 10. Study of the Lepton Flavour Violating Decays of Charged Fermions in SUSY GUTs; 11. Interactions of the Goldstino Supermultiplet with Standard Model Fields; 12. Attempts at Explaining the NuTeV Observation of Di-Muon Events; 13. Kaluza-Klein States of the Standard Model Gauge Bosons: Constraints From High Energy Experiments; 14. Kaluza-Klein Excitations of Gauge Bosons in the ATLAS Detector; 15. Search for the Randall Sundrum Radion Using the ATLAS Detector; 16. Radion Mixing Effects on the Properties of the Standard Model Higgs Boson; 17. Probing Universal Extra Dimensions at Present and Future Colliders; 18. Black Hole Production at Future Colliders.
The impact on the physics capabilities of the ATLAS detector of possible LHC upgrades is discussed. As a benchmark, an increase in the luminosity by a factor of ten is considered. For comparison, a doubling of the LHC energy is also explored. Both upgrades significantly enhance the physics capabilities of ATLAS. As measured in terms of the mass reach for new particles, the energy upgrade is more powerful. However, in cases where the effect of an upgrade is to increase the precision of measurements as a result of the larger data samples, the luminosity upgrade can be at least as powerful. The pile-up of minimum bias events at higher luminosity could limit the physics performance of ATLAS in areas where tagging of forward jets is needed.
The ``Snowmass Points and Slopes'' (SPS) are a set of benchmark points and parameter lines in the MSSM parameter space corresponding to different scenarios in the search for Supersymmetry at present and future experiments. This set of benchmarks was agreed upon at the 2001 ``Snowmass Workshop on the Future of Particle Physics'' as a consensus based on different existing proposals.
Scenarios are developed for runs at a Linear Collider, in the case that there is a rich program of new physics.
This note summarizes many detailed physics studies done by the ATLAS and CMS Collaborations for the LHC, concentrating on processes involving the production of high mass states. These studies show that the LHC should be able to elucidate the mechanism of electroweak symmetry breaking and to study a variety of other topics related to physics at the TeV scale. In particular, a Higgs boson with couplings given by the Standard Model is observable in several channels over the full range of allowed masses. Its mass and some of its couplings will be determined. If supersymmetry is relevant to electroweak interactions, it will be discovered and the properties of many supersymmetric particles elucidated. Other new physics, such as the existence of massive gauge bosons and extra dimensions can be searched for extending existing limits by an order of magnitude or more.
This brief Letter demonstrates that effects from a $\nc$ space-time geometry will measurably affect the value of $(g-2)_μ$ inferred from the decay of the muon to an electron plus two neutrinos. If the scale of noncommutivity is ${\cal O}(TeV)$, the alteration of the $V-A$ structure of the lepton-lepton-W vertex is sufficient to shift the inferred value of $(g-2)_μ$ to one part in $10^8$. This may account for the recently reported $2.6 σ$ discrepancy between the BNL measurement $a_{expt} = 11659202(14)(6) \times 10^{-10}$ and the Standard Model prediction $a_{SM} = 11659159.6(6.7) \times 10^{-10}$.
Generic Fortran common blocks are presented for use by High Energy Physics event generators for the transfer of event configurations from parton level generators to showering and hadronization event generators.
If the geometry of space-time is $\nc$, i.e. $[x_μ,x_ν]=i θ_{μν}$, then $\nc$ $\cpviolng$ effects may be manifest at low energies. For a $\nc$ scale $Λ\equiv θ^{-1/2} \leq 2 TeV$, $\cpviol$ from $\ncg$ is comparable to that from the Standard Model (SM) alone: the $\nc$ contributions to $ε$ and $ε'/ε$ in the $K$-system, may actually dominate over the Standard Model contributions. Present data permit $\ncg$ to be the only source of $\cpviol$. Furthermore the most recent findings for g-2 of the muon are consistent with predictions from $\ncg$. If the geometry of space-time is $\nc$, $i.e.$ $[x_μ,x_ν]=i θ_{μν}$, then $\nc$ $\cpviolng$ effects may be manifest at low energies. For a $\nc$ scale $Λ\equiv θ^{-1/2} \leq 2 TeV$, $\cpviol$ from $\ncg$ is comparable to that from the Standard Model (SM) alone: the $\nc$ contributions to $ε$ and $ε'/ε$ in the K-system, may actually dominate over the Standard Model contributions. Present data permit $\ncg$ to be the only source of $\cpviol$. Furthermore the most recent findings for g-2 of the muon are consistent with predictions from $\ncg$.
We briefly review the SUGRA, GMSB and AMSB supersymmetry breaking models. We then discuss the phenomenological differences between them and consequent characteristic experimental signatures. This is followed by a review of the discovery potential for supersymmetry at the Tevatron, LHC and a future e+e- linear collider.
A Supersymmetric Grand unified model is constructed based on SO(10)xSO(10) symmetry in which new types of Yukawa matrices couple standard and exotic fermions. Evolution of these couplings from the Grand Unified scale to the electroweak scale causes some of them to be driven to their fixed points. This solves the supersymmetric alignment problem and ensures that there are no observable flavor changing neutral currents mediated by supersymmetric particles. Fermion hierarchy and neutrino mixing constraints are automatically satisfied in this formalism.
Recent results from Super Kamiokande suggest $ν_μ-ν_τ$ mixing and hence lepton flavor violation. In supersymmetric models, this flavor violation may have implications for the pattern of slepton masses and mixings. Possible signals for this mixing in the decays of sleptons produced at the LHC are discussed. The sensitivity expected is compared to that of rare decays such as $τ\to μγ$.
The generic missing transverse energy signals at LHC for theories having large extra dimensions are discussed. Final states of jets plus missing energy and photons plus missing energy are simulated in the ATLAS detector. The discovery limit of LHC and the methods to determine the parameters of the underlying model are discussed.