arXiv subjects

Georg Weiglein

Publications and source records attributed to Georg Weiglein.

104 records · Page 6Linked to original sources

arXiv2007

SUSY in the Light of B Physics and Electroweak Precision Observables

Indirect information about the possible scale of supersymmetry (SUSY) breaking can be obtained from the comparison of precisely measured observables (and also of exclusion limits) with accurate theory predictions incorporating SUSY loop corrections. Recent results are reviewed obtained from a combined analysis of the most sensitive electroweak precision observables (EWPO), M_W, sin^2_theta^eff, Gamma_Z, (g-2)_μand M_h, and B-physics observables (BPO), BR(b -> s γ), BR(B_s -> μ^+μ^-), BR(B_u -> τν_τ) and ΔM_{B_s}. Assuming that the lightest supersymmetric particle (LSP) provides the cold dark matter density preferred by WMAP and other cosmological data, χ^2 fits are performed to the parameters of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which the SUSY-breaking parameters are universal at the GUT scale, and the non-universal Higgs model (NUHM), in which this constraint is relaxed for the soft SUSY-breaking contributions to the Higgs masses. Within the CMSSM indirect bounds on the mass of the lightest CP-even Higgs boson are derived.

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arXiv2007

SUSY Higgs bosons at the LHC

Recent results on MSSM Higgs physics at the LHC are reviewed. The dependence of the LHC discovery reach in the b\bar b H/A, H/A \to τ^+τ^- channel on the underlying SUSY scenario is analysed. This is done by combining the latest results for the prospective CMS experimental sensitivities for an integrated luminosity of 30 or 60 fb^-1 with state-of-the-art theoretical predictions of MSSM Higgs-boson properties. The results are interpreted in terms of the parameters governing the MSSM Higgs sector at lowest order, M_A and tan_beta. While the higgsino mass parameter μhas a significant impact on the prospective discovery reach (and correspondingly the ``LHC wedge'' region), it is found that the discovery reach is rather stable with respect to variations of other supersymmetric parameters. Within the discovery region a determination of the masses of the heavy neutral Higgs bosons with an accuracy of 1-4% seems feasible. It is furthermore shown that Higgs-boson production in central exclusive diffractive channels can provide important information on the properties of the neutral MSSM Higgs bosons.

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arXiv2005

The LHC and the ILC

The synergy between the Large Hadron Collider and the International Linear Collider during concurrent running of the two machines has the potential to maximise the physics gain from both facilities. Some examples of detailed case studies of the interplay between the LHC and ILC are given, with a particular emphasis on new results that have been obtained after the first LHC / ILC Study Group report was released.

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arXiv2004

The Linear Collider Physics Case: International Response to the Technology Independent Questions Posed by the International Technology Recommendation Panel

The International Technology Recommendation Panel distributed a list of questions to each major laboratory. Question 30, part b and d, were technology independent and related to the physics goals of the Linear Collider. An international panel, with representation from Asia, Europe, and the Americas, was formed by the World Wide Study during LCWS04 to formulate a response. This is given below and constitutes the response of the world-wide Linear Collider community.

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arXiv2004

The anomalous magnetic moment of the muon in the MSSM - recent developments

We present recent results of two interesting classes of supersymmetric two-loop contributions to (g-2)_mu. Two-loop diagrams involving either a closed sfermion loop or a closed chargino/neutralino loop can amount to 5*10^{-10}, which is almost one standard deviation of the current experimental uncertainty. We discuss the dependence of these two classes on the unknown supersymmetric parameters and their impact on the supersymmetric prediction of (g-2)_mu.

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arXiv2004

Electroweak and supersymmetric two-loop corrections to (g-2)_μ

We present the up to now most precise evaluation of electroweak and supersymmetric contributions to the anomalous magnetic moment of the muon \amu, describing in detail also the calculational techniques. We calculate the bosonic two-loop contributions in the Standard Model without the approximation of a heavy Higgs-boson mass, finding corrections up to 0.2*10^{-10} for a light Higgs boson. In the Minimal Supersymmetric Standard Model the corresponding two-loop contributions from the two-Higgs-doublet model part differ from the Standard Model result by up to 0.3*10^{-10}. Finally, we evaluate the diagrams where a loop of charginos or neutralinos, the superpartners of gauge and Higgs bosons, is inserted into a two-Higgs-doublet one-loop diagram. These corrections can amount up to 10*10^{-10}, which is almost 2σof the current experimental uncertainty.

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arXiv2004

Interplay between the LHC and a Linear Collider in Searches for New Physics

The LHC / LC Study Group investigates how analyses at the LHC could profit from results obtained at a future Linear Collider and vice versa, leading to mutual benefits for the physics program at both machines. Some examples of results obtained within this working group so far concerning searches for new physics are briefly summarised.

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arXiv2003

The LHC / LC Study Group and the Snowmass Points and Slopes

The ``LHC / LC Study Group'' investigates how analyses at the LHC could profit from results obtained at a future Linear Collider and vice versa. Some of the activities of this recently formed working group are briefly summarised. The LHC / LC Study Group home page is http://www.ippp.dur.ac.uk/~georg/lhclc/ . 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. Further information about the SPS can be found under http://www.ippp.dur.ac.uk/~georg/sps/ .

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arXiv2003

Precision Observables in the MSSM: Status and Perspectives

The current status of the theoretical predictions for the electroweak precision observables M_W, sin^2_theta_eff and m_h within the MSSM is briefly reviewed. The impact of recent electroweak two-loop results to the quantity Delta_rho is analysed and the sensitivity of the electroweak precision observables to the top-quark Yukawa coupling is investigated. Furthermore the level of precision necessary to match the experimental accuracy at the next generation of colliders is discussed.

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arXiv2002

Two-Loop Results for M_W in the Standard Model and the MSSM

Recent higher-order results for the prediction of the W-boson mass, M_W, within the Standard Model are reviewed and an estimate of the remaining theoretical uncertainties of the electroweak precision observables is given. An updated version of a simple numerical parameterisation of the result for M_W is presented. Furthermore, leading electroweak two-loop contributions to the precision observables within the MSSM are discussed.

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arXiv2002

Precision Analysis of the Lightest MSSM Higgs Boson at Future Colliders

We investigate the sensitivity of observables measurable in e^+ e^-, gamma gamma and mu^+ mu^- collisions for distinguishing the properties of the light neutral CP-even Higgs boson in the minimal supersymmetric extension of the Standard Model (MSSM) from those of a Standard Model (SM) Higgs boson with the same mass. We explore first the available parameter space in the constrained MSSM (CMSSM), with universal soft supersymmetry-breaking parameters, incorporating the most recent direct limits on sparticle and Higgs masses, the indirect constraints from b to s gamma and g_mu - 2, and the cosmological relic density. We calculate the products of the expected CMSSM Higgs production cross sections and decay branching ratios sigma X B normalized by the corresponding values expected for those of a SM Higgs boson of the same mass. The results are compared with the precisions expected at each collider, and allow for a direct comparison of the different channels. The measurements in the Higgs sector are found to provide important consistency tests of the CMSSM. We then generalize our analysis to the case of a non-universal Higgs model (NUHM), where the values of M_A and mu are independent parameters. We explore in particular the sensitivity to M_A, finding that measurements at e^+ e^-, gamma gamma and mu^+ mu^- colliders could yield indirect constraints on its value, up to M_A ~ 1200 GeV. We discuss the potential of these measurements for distinguishing between the CMSSM and the NUHM, probing in this way the assumption of universality.

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arXiv2000

The MSSM at present and future colliders

A brief overview over the phenomenology of the MSSM at present and future colliders is given. The complementarity of indirect tests of the model via precision observables and of the information from the direct production of SUSY particles is emphasized. If the lightest Higgs boson of the MSSM will be detected, its mass will also play an important role as a precision observable.

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arXiv1998

The Callan-Symanzik equation of the electroweak Standard Model and its 1-loop functions

We derive the Callan-Symanzik equation of the electroweak Standard Model in the QED-like on-shell parameterization. The various coefficient functions, the $β$-functions and anomalous dimensions, are determined in one-loop order in the most general linear gauge compatible with rigid symmetry. In this way the basic elements for a systematic investigation of higher-order leading logarithmic contributions in the Standard Model are provided. The one-loop $β$-function of the electromagnetic coupling turns out to be independent of mass ratios and it is QED-like in this sense. Besides the QED-contributions of fermions it contains non-abelian contributions from vectors and ghosts with negative sign, which overcompensate the contributions of the fermions if one restricts the latter to one fermion generation. We also compare our results with the symmetric theory and give relations between the $β$-functions of the spontaneously broken and the symmetric theory valid in one-loop order.

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arXiv1995

Gauge invariance, gauge-parameter independence and properties of Green functions

The application of the background-field method to the electroweak Standard Model is reviewed and further explored. Special emphasis is put on questions of gauge invariance and gauge-parameter (in-)dependence. Owing to the gauge invariance of the background-field effective action, the vertex functions obey simple Ward identities which imply important properties of the vertex functions. Carrying out the renormalization in a way respecting background-field gauge invariance leads to considerable simplifications. The generalization of the background-field method to the non-linear realization of the scalar sector of the Standard Model is illustrated. Furthermore, the interplay between gauge independence of the S-matrix and Ward identities of vertex functions is investigated. Finally, the Standard Model contributions to the $S$, $T$, and $U$ parameters are calculated and discussed within the background-field method.

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