NMSSM from alternative deflection in generalized deflected anomaly mediated SUSY breaking

We propose a new approach to generate messenger–matter interactions in deflected anomaly mediated SUSY breaking mechanism from typical holomorphic messenger–matter mixing terms in the Kahler potential. This approach is a unique feature of AMSB and has no analog in GMSB-type scenarios. New coupling strengths from the scaling of the (already known) Yukawa couplings always appear in this approach. With messenger–matter interactions in deflected AMSB, we can generate a realistic soft SUSY breaking spectrum for next-to-minimal supersymmetric standard model (NMSSM). Successful electroweak symmetry breaking conditions, which is not easy to satisfy in NMSSM for ordinary AMSB-type scenario, can be satisfied in a large portion of parameter space in our scenarios. We study the relevant phenomenology for scenarios with (Bino-like) neutralino and axino LSP, respectively. In the case of axino LSP, the SUSY contributions to \(\Delta a_\mu \) can possibly account for the muon \(g-2\) discrepancy. The corresponding gluino masses, which are found to below 2.2 TeV, could be tested soon at LHC.     

Recent results from LEP

Recent results from the LEP collider at CERN are presented: on the identification of e ⁺ e ⁻ → W ⁺ W ⁻ and the determination of the W mass and width and limits on its anomalous couplings; the search for the Standard Model and non-minimal Higgs; search for SUSY and other new particles. Fits to all electroweak data leading to predictions of the Higgs mass within the Standard Model are presented.     

A large scale double beta and dark matter experiment: On the physics potential of GENIUS

The physics potential of GENIUS, a recently proposed double beta decay and dark matter experiment is discussed. The experiment will allow to probe neutrino masses down to 10^?(2–3) eV. GENIUS will test the structure of the neutrino mass matrix, and therefore implicitly neutrino oscillation parameters comparable or superior in sensitivity to the best proposed dedicated terrestrial neutrino oscillation experiments. If the 10^-3 eV level is reached, GENIUS will even allow to test the large angle MSW solution of the solar neutrino problem. Even in its first stage GENIUS will confirm or rule out degenerate or inverted neutrino mass scenarios, which have been widely discussed in the literature as a possible solution to current hints on finite neutrino masses and also test the ν_e ? ν_μ hypothesis of the atmospheric neutrino problem. GENIUS would contribute to the search for R-parity violating SUSY and right-handed W-bosons on a scale similar or superior to LHC. In addition, GENIUS would largely improve the current 0νββ decay searches for R-parity conserving SUSY and leptoquarks. Concerning cold dark matter (CDM) search, the low background anticipated for GENIUS would, for the first time ever, allow to cover the complete MSSM neutralino parameter space, making GENIUS competitive to LHC in SUSY discovery. If GENIUS could find SUSY CDM as a by-product it would confirm that R-parity must be conserved exactly. GENIUS will thus be a major tool for future non-accelerator particle physics.     

Chargino decays in the complex MSSM: a full one-loop analysis

We evaluate two-body decay modes of charginos in the Minimal Supersymmetric Standard Model with complex parameters (cMSSM). Assuming heavy scalar quarks we take into account all decay channels involving charginos, neutralinos, (scalar) leptons, Higgs bosons and Standard Model gauge bosons. The evaluation of the decay widths is based on a full one-loop calculation including hard and soft QED radiation. Special attention is paid to decays involving the Lightest Supersymmetric Particle (LSP), i.e. the lightest neutralino, or a neutral or charged Higgs boson. The higher-order corrections of the chargino decay widths involving the LSP can easily reach a level of about ±10%, while the corrections to the decays to Higgs bosons are slightly smaller, translating into corrections of similar size in the respective branching ratios. These corrections are important for the correct interpretation of LSP and Higgs production at the LHC and at a future linear e ⁺ e ⁻ collider. The results will be implemented into the Fortran code FeynHiggs.     

Search for the Standard Model Higgs boson with the OPAL detector at LEP

This paper summarises the search for the Standard Model Higgs boson in e ⁺ e ^- collisions at centre-of-mass energies up to 209 GeV performed by the OPAL Collaboration at LEP. The consistency of the data with the background hypothesis and various Higgs boson mass hypotheses is examined. No indication of a signal is found in the data and a lower bound of 112.7 Gev/c² is obtained on the mass of the Standard Model Higgs boson at the 95% CL. Received: 13 March 2002 / Revised version: 9 October 2002 / Published online: 13 December 2002     

The new look pMSSM with neutralino and gravitino LSPs

The pMSSM provides a broad perspective on SUSY phenomenology. In this paper we generate two new, very large, sets of pMSSM models with sparticle masses extending up to 4?TeV, where the lightest supersymmetric particle (LSP) is either a neutralino or gravitino. The existence of a gravitino LSP necessitates a detailed study of its cosmological effects and we find that Big Bang Nucleosynthesis places strong constraints on this scenario. Both sets are subjected to a global set of theoretical, observational and experimental constraints resulting in a sample of ??225k viable models for each LSP type. The characteristics of these two model sets are briefly compared. We confront the neutralino LSP model set with searches for SUSY at the 7?TeV LHC using both the missing (MET) and non-missing E _T ATLAS analyses. In the MET case, we employ Monte Carlo estimates of the ratios of the SM backgrounds at?7 and?8?TeV to rescale the 7?TeV data-driven ATLAS backgrounds to 8?TeV. This allows us to determine the pMSSM parameter space coverage for this collision energy. We find that an integrated luminosity of ??5?C20?fb^?1 at 8?TeV would yield a substantial increase in this coverage compared to that at 7?TeV and can probe roughly half of the model set. If the pMSSM is not discovered during the 8?TeV run, then our model set will be essentially void of gluinos and lightest first and second generation squarks that are ?700?C800?GeV, which is much less than the analogous mSUGRA bound. Finally, we demonstrate that non-MET SUSY searches continue to play an important role in exploring the pMSSM parameter space. These two pMSSM model sets can be used as the basis for investigations for years to come.     

Virtual LSPs at e+ e− colliders

Currently popular search strategies for supersymmetric particles may be significantly affected due to relatively light sneutrinos which decay dominantly into invisible channels. In certain cases the second lightest neutralino may also decay invisibly leading to two extra carriers of missing energy (in addition to the lightest supersymmetric particle (LSP) ) — the virtual LSPs (VLSPs). A tree lavel calculation shows that if the sneutrino mass happens to be in the small but experimentally allowed range (m _≈ν ≈ 45–55 GeV), these particles together with neutralino pairs may contribute significantly to the missing energy in the process e⁺e^? → γ+ E at LEP-2 energies as an enhancement over the Standard Model or the conventional MSSM predictions. It is further shown that a much larger region of the parameter space can be scanned at a high luminosity e⁺e^? collider at 500 GeV like the proposed NLC machine. Moreover, at both LEP-2 and NLC this process may play a complementary role to direct chargino searches, which may fail due to a near mass degeneracy of the chargino and the sneutrino. Formulae for the cross sections taking into account full mixings of the charginos and the neutralinos are derived. The signal remains observable even in the context of more restricted models based onN=1 SUGRA with common scalar and gaugino masses. A preliminary study of the QED radiative corrections due to soft multiple photon emission as well as hard collinear bremsstrahlung indicates that these corrections play a crucial role in estimating the background.     

Production of supersymmetric particles ine + e − andep collisions

A review is given of the theoretical predictions for chargino, neutralino and selectron pair production ine ⁺ e ^– annihilation and for slepton and squark production inep collisions. The energy range considered is that of LEP, SLC and HERA. The expectations for the production of SUSY particles at ane ⁺ ev ^– collider in the TeV energy range are also discussed.Invited talk at the International Symposium Hadron Interactions — Theory and Phenomenology, Bechyn, Czechoslovakia, June 26–July 1, 1988.I want to thank H. Baer, H. Fraas, D. Karatas, W. Majerotto and X. Tata for discussions and correspondence. Financial supports of the Czechoslovak Academy of Sciences and the Austrian Academy of Sciences are gratefully acknowledged.     

Searches for Gauge-Mediated Supersymmetry Breaking topologies in e^+e^- collisions at centre-of-mass energies up to \sqrt{s}=209 \mathrm{GeV}

Searches were performed for topologies predicted by gauge-mediated supersymmetry breaking models (GMSB). All possible lifetimes of the next-to-lightest SUSY particle (NLSP), either the lightest neutralino or slepton, decaying into the lightest SUSY particle, the gravitino, were considered. No evidence for GMSB signatures was found in the OPAL data sample collected at centre-of-mass energies up to $\sqrt{s}=209 \mathrm{GeV}$ at LEP. Limits on the product of the production cross-sections and branching fractions are presented for all search topologies. To test the impact of the searches, a complete scan over the parameters of the minimal model of GMSB was performed. NLSP masses below $53.5 \mathrm{GeV}/c^2$ in the neutralino NLSP scenario, below $87.4 \mathrm{GeV}/c^2$ in the stau NLSP scenario and below $91.9 \mathrm{GeV}/c^2$ in the slepton co-NLSP scenario are excluded at 95% confidence level for all NLSP lifetimes. The scan determines constraints on the universal SUSY mass scale Λ from the direct SUSY particle searches of Λ>40, 27, 21, 17, $15 \mathrm{GeV}/c^2$ for messenger indices N=1,2,3,4,5 for all NLSP lifetimes.     

Hunting effective LSPs at LEP 200

Relatively light sneutrinos, which are experimentally allowed, may significantly affect the currently popular search strategies for supersymmetric particles by decaying dominantly into an invisible channel. In certain cases the second lightest neutralino may also decay invisibly leading to two extra carriers of missing energy — in addition to the lightest supersymmetric particle (LSP) — the effective LSPs (ELSPs). It is shown that these ELSPs are allowed in supergravity models with common scalar and gaugino masses at the unification scale for a sizable region of parameter space and are consistent with all constraints derived so far from SUSY searches. The pair production of right handed sleptons, which can very well be the lightest charged SUSY particles in this scenario, at LEP 200 and their decay signatures are discussed. The signal survives kinematical cuts required to remove the standard model background. Charginos are also pair produced copiously if kinematically accessible; they also decay dominantly into hadronically quiet di-lepton + modes leading to interesting unlike sign dilepton events which are again easily separable from the Standard Model backgrounds at LEP 200 energies.     

Single and multi-photon events with missing energy in eecollisions at = 189 GeV

Single and multi-photon events with missing energy are analysed using data collected with the L3 detector at LEP at a centre-of-mass energy of 189 GeV, for a total of 176 pb of integrated luminosity. The cross section of the process e⁺e⁻ → γ(γ) is measured and the number of light neutrino flavours is determined to be N_ν=3.011±0.077 including lower energy data. Upper limits on cross sections of supersymmetric processes are set and interpretations in supersymmetric models provide improved limits on the masses of the lightest neutralino and the gravitino. Graviton-photon production in low scale gravity models with extra dimensions is searched for and limits on the energy scale of the model are set exceeding 1 TeV for two extra dimensions.     

Associated production of light gravitinos in e+e? and e?γ collisions

Light gravitino productions in association with a neutralino (selectron) in e ⁺ e ⁻ (e ⁻ γ) collisions are restudied in a scenario that the lightest supersymmetric particle is a gravitino and the produced neutralino (selectron) promptly decays into a photon (electron) and a gravitino. We explicitly give the helicity amplitudes for the production processes by using the effective goldstino interaction Lagrangian, and present the cross sections with different collision energies and mass spectra. We also examine selection efficiencies by kinematical cuts and beam polarizations for the signal and background processes, and show that the energy and angular distributions of the photon (electron) can explore the mass of the t-channel exchange particle as well as the mass of the decaying particle at a future e ⁺ e ⁻ (e ⁻ γ) collider.     

Neutralino phenomenology at LEP2 in supersymmetry with bilinear breaking of R-parity

We discuss the phenomenology of the lightest neutralino in models where an effective bilinear term in the superpotential parametrizes the explicit breaking of R-parity. We consider supergravity scenarios where the lightest supersymmetric particle (LSP) is the lightest neutralino and which can be explored at LEP2. We present a detailed study of the LSP decay properties and general features of the corresponding signals expected at LEP2. We also contrast our model with gauge mediated supersymmetry breaking.     

Search for supersymmetry with gauge-mediated breaking in diphoton events at D0

We report the results of a search for supersymmetry (SUSY) with gauge-mediated breaking in the missing transverse energy distribution of inclusive diphoton events using 263 pb(-1) of data collected by the D0 experiment at the Fermilab Tevatron Collider in 2002-2004. No excess is observed above the background expected from standard model processes, and lower limits on the masses of the lightest neutralino and chargino of about 108 and 195 GeV, respectively, are set at the 95% confidence level. These are the most stringent limits to date for models with gauge-mediated SUSY breaking with a short-lived neutralino as the next-to-lightest SUSY particle.     

Exact solution of the neutralino mass matrix

The eigenvalue problem for the neutralino mass matrix has been solved exactly and the eigenvalues are expressed in terms of thev ₁/v ₂, chargino and gluino masses which are directly measurable. An analytical formula for the lightest neutralino mass as a function of the above parameters is obtained. Formulae for the photino, zino and neutral higgsino contents of each of the physical neutralino mass eigenstates states have been found. Taking into account these formulae it has been possible to predict the upper (lower) bound on the mass of zino (photino) dominant neutralino states, including the lightest one. The neutralino-gluino and neutralino-chargino mass planes have also been constrained by using the latest LEP data.     

The measurement of $\alpha_s$ from event shapes with the DELPHI detector at the highest LEP energies

Searches for pair-production of supersymmetric particles under the assumption of non-conservation of R-parity with a dominant LL or term have been performed using the data collected by the DELPHI experiment at LEP in e ⁺ e^- collisions at centre-of-mass energies from 192 up to 208 GeV. No excess of data above Standard Model expectations was observed. The results were used to constrain the MSSM parameter space and to derive limits on the masses of supersymmetric particles.Received: 4 March 2004, Revised: 5 May 2004, Published online: 23 June 2004An Erratum to this article can be found at     

Higgs search: present and future

In this talk I review theoretical bounds on mass of the Higgs scalar in the Standard Model (SM) and then summarise current experimental limits from the LEP experiments. Following this I discuss the search strategies for the SM Higgs at LEP 200 and the TeV energye ⁺ e ^? colliders which are under discussion. This will be followed by a summary of the Higgs search potential of the pp supercolliders such as SSC/LHC. I then close with a brief discussion of a ‘Dark Higgs’ whose dominant decay modes are into invisible channels.     

Signatures of virtual LSPs at TEVATRON

Relatively light sneutrinos which are experimentally allowed and are not theoretically disfavoured may significantly affect the currently popular search strategies for supersymmetric particles by decaying dominantly into an invisible channel. In certain cases the second lightest neutralino may also decay invisibly leading to two extra carriers of missing energy (in addition to the lightest supersymmetric particle (LSP))—the virtual LSPs (VLSPs). The lighter charginos which would be produced in pairs with reasonably large cross-sections at TEVATRON energies, decay dominantly into the hadronically quiet lepton+sneutrino (E _T ) modes with large branching ratios leading to interesting unlike sign dilepton events which are not swamped by the standard model background. The kinematical cuts required to eliminate the backgrounds from WW, Drell-Yan and τ pair production are discussed in detail. With 100pb ^?1 luminosity 10–35 background free events can be found in a large region of the SUSY parameter space.     

Scalar field theory in the strong self-interaction limit

We revisit the monophoton plus missing energy signature at \(e^+e^-\) colliders in supersymmetric (SUSY) models where the gravitino is very light. There are two possible processes which provide the signal: gravitino pair production and associated gravitino production with a neutralino, leading the monophoton final state via an additional photon radiation and via the neutralino decay, respectively. By using the superspace formalism, we construct a model that allows us to study the parameter space for the both processes. We show that the signal cross section and the photon spectra provide information on the masses of the SUSY particles as well as the SUSY breaking scale.     

Resolving Fermi, PAMELA and ATIC anomalies in split supersymmetry without R-parity

A long-lived decaying dark matter as a resolution to Fermi, PAMELA and ATIC anomalies is investigated in the framework of split supersymmetry (SUSY) without R-parity, where the neutralino is regarded as the dark matter and the extreme fine-tuned couplings for the long-lived neutralino are naturally evaded in the usual approach. The energy spectra of electron and positron are from not only the direct neutralino decays denoted by χ→e ⁺ e ^? ν, but also the decaying chains such as $\chi\to e^{+}\nu\mu(\to \nu_{\mu}e\bar{\nu}_{e})$ . We find that with a proper lifetime of the neutralino, slepton-mediated effects could explain the ATIC and PAMELA data well, but an inconsistence occurs to the Fermi and PAMELA data without considering the ATIC one. However, by a suitable combination of χ→e ⁺ e ^? ν and $\chi\to e^{+}\nu \mu(\to\nu_{\mu}e\bar{\nu}_{e})$ , the sneutrino-mediated effects could simultaneously account for the Fermi and PAMELA data.