Neutralino Cascades in the (M+1)SSM

In the (M+1)SSM an additional gauge singlet Weyl spinor appears in the neutralino sector. For a large part of the parameter space this approximative eigenstate is the true LSP. Then most sparticle decays proceed via an additional cascade involving the NLSP LSP transition, where the NLSP is the non-singlet next-to-lightest neutralino. We present a comprehensive list of all processes, which contribute to the NLSP LSP transition, the partial widths and the total NLSP decay rate. We perform a scan of the parameters of the model compatible with universal soft terms, and find that the NLSP life time can be quite large, leading to macroscopically displaced vertices. Our results imply that the signatures for sparticle production in the (M+1)SSM can be very different from the MSSM, and are important for calculations of the abundance of dark matter in this model. Received: 10 December 1997 / Revised version: 26 January 1998 / Published online: 30 March 1998     

Search for an LSP gluino at LEP with the DELPHI detector

In some supersymmetric models, the gluino () is predicted to be light and stable. In that case, it would hadronize to form R-hadrons. In these models, the missing energy signature of the lightest supersymmetric particle is no longer valid, even if R-parity is conserved. Therefore, such a gluino is not constrained by hadron collider results, which looked for the decay . Data collected by the DELPHI detector in 1994 at 91.2 GeV have been analysed to search for events. No deviation from Standard Model predictions is observed and a gluino mass between 2 and 18 GeV/c² is excluded at the 95% confidence level in these models. Then, R-hadrons produced in the squark decays were searched for in the data collected by DELPHI at the centre-of-mass energies of 189 to 208 GeV, corresponding to an overall integrated luminosity of 609 Pb^-1. The observed number of events is in agreement with the Standard Model predictions. Limits at 95% confidence level are derived on the squark masses from the excluded regions in the plane () GeV/c², and GeV/c² for purely left squarks. GeV/c², and GeV/c² independent of the mixing angle. Received: 6 November 2002 / Published online: 15 January 2003     

Masses and couplings of the lightest Higgs bosons in (M + 1)SSM

We study the upper limits on the mass of the lightest and second lightest CP even Higgs bosons in the (M + 1)SSM, the MSSM extended by a gauge singlet. The dominant two loop contributions to the effective potential are included, which reduce the Higgs masses by GeV. Since the coupling R of the lightest Higgs scalar to gauge bosons can be small, we study in detail the relations between the masses and couplings of both lightest scalars. We present upper bounds on the mass of a ”strongly” coupled Higgs (R < 1/2) as a function of lower experimental limits on the mass of a ”weakly” coupled Higgs (R < 1/2). With the help of these results, the whole parameter space of the model can be covered by Higgs boson searches. Received: 7 September 1999 / Published online: 12 July 2002     

Constraints from charge and colour breaking minima in the (M+1)SSM

We study the constraints on the parameter space of the supersymmetric standard model extended by a gauge singlet, which arise from the absence of global minima of the effective potential with slepton or squark vevs. Particular attention is paid to the so-called “UFB” directions in field space, which are F-flat in the MSSM. Although these directions are no longer F-flat in the (M+1)SSM, we show that the corresponding MSSM-like constraints on m₀/M_1/2 apply also to the (M+1)SSM. The net effect of all constraints on the parameter space are more dramatic than in the MSSM. We discuss the phenomenological implications of these constraints.     

Folded localized excitations of the (2+1)-dimensional (M+N)-component AKNS system

Starting from the standard truncated Painlevé expansion and a multilinear variable separation approach, a quite general variable separation solution of the (2+1)-dimensional (M+N)-component AKNS (Ablowitz–Kaup–Newell–Segur) system is derived. In addition to the single-valued localized coherent soliton excitations like dromions, breathers, instantons, peakons, and a previously revealed chaotic localized solution, a new type of multi-valued (folded) localized excitation is obtained by introducing some appropriate lower-dimensional multiple valued functions. The folded phenomenon is quite universal in the real natural world and possesses quite rich structures and abundant interaction properties.     

Luminescence of orthovanadates M 3 + M3+(VO4)2 and M 2 + M4+ (VO4)2

The absorption, excitation, and luminescence spectra of vanadates of type M ₃ ⁺ M³⁺(VO₄)₂ and M ₂ ⁺ M⁴⁺(VO₄)₂ are studied, where M⁺ is Na, K, Rb, Cs; M³⁺ is Al, Sc; M⁴⁺ is Zr, Sn, Ti. The luminescence spectra maxima are located at 490–510 nm, while those of the excitation spectra are at 360–375 nm. Temperature characteristics of luminescence and thermostimulated luminescence are studied. The question of activation of complex vanadates by rare-earth ions is considered.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 24–28, March, 1976.     

Instability at the origin in (2+1)-dimensional QED

Stability at the origin in (2+1)-dimensional QED withN four-component Dirac fermions is studied by keeping the leading order terms in 1/N in the effective potential. It is shown that the effective potential in the direction of fermion wave-function renormalization is always unstable for any flavor numberN, which reconfirms that chiral symmetry is broken for anyN.     

SUSY virtual effects at the LEP2 boundary

We examine the possibility that SUSY particles are light, i.e. have a mass just beyond the final kinematical reach of LEP2. In this case, even if light particles are not directly detected, their virtual effects are enhanced by a “close-to-threshold” resonance in the s-channel. We find that this resonant effect is absent in the case of light sfermions, while it is enhanced in the case of light gauginos, since neutralinos and charginos add coherently in some regions of the allowed parameter space. We discuss this “virtual alliance” in detail and try to examine the possibilities of its experimental verification. Received: 19 March 1999 / Published online: 12 August 1999     

The (2+1) Dirac Equation with a Delta Potential

In this Letter the bound states of (2+1) Dirac equation with the cylindrically symmetric (r–r ₀) potential are discussed. It is surprisingly found that the relation between the radial functions at two sides of r ₀ can be established by an SO(2) transformation. We obtain a transcendental equation for calculating the energy of the bound state from the matching condition in the configuration space. The condition for existence of bound states is determined by the Sturm-Liouville theorem.     

Heterometallic fullerides of Fe and Cu groups with the composition K2MC60 (M=Fe+2, Fe+3, Co+2, Ni+2, Cu+1, Cu+2, Ag+1)

Heterometallic fullerides with composition K₂MC₆₀, synthesized by exchange chemical reaction of K₅C₆₀ or K₄C₆₀ with chlorides of metals Fe and Cu groups have been investigated by X-ray diffraction, magnetic resonance, Raman and Mössbauer spectroscopy. Magnetization and susceptibility measurements have also been carried out. Metal chlorides from Fe and Cu groups enable to cover the whole range of electronic configuration of metal from d⁵ to d¹⁰. Heterometallic fullerides with M=Cu⁺², Fe⁺², Fe⁺³ and Ni⁺² appeared to be superconductors with T_c=13.9–16.5 K. Ferromagnetism and superconductivity coexist in investigated fulleride K₂Fe⁺³C₆₀.     

Electric-dipole allowed (E1) and forbidden (E2, M1 and M2)transition probabilities of 4f for N+

By applying systematically enlarged multi-configuration Dirac-Fock wavefunction,the transitions for electricdipole allowed(E1) and forbidden(E2,M1 and M2) lines are studied among 4f pair coupling and low-lying configurations for singly ionized nitrogen.Most important effects of relativity,electron correlation,the rearrangement of electron density,Breit interaction,and quantum electrodynamic effects are included in the computation.Then,allowed(E1) and forbidden(E2,M1 and M2) transition probabilities of 4f for N+ are obtained and compared with experimental results.Good agreement with available experimental results is found and most of the data of 4f are presented for the first time.     

Observability at LEP2 hadronic channels of a Z’ with small lepton couplings

We consider the effects of a number of models with one extra Z, with enhanced couplings to quarks, in the final hadronic channels at LEP2. We show that, for a number of representative cases, visible effects could be produced even for very low values of the lepton couplings, much smaller than the existing LEP1/SLC and the future LEP2 (lepton channel) bounds.     

Mixing ratio of the 0.34 MeV (M1 + E2) transition in49Ti

A direction-polarization correlation experiment was carried out in order to remove the ambiguity of the mixing ratio of the 0.34 MeV transition in⁴⁹Ti. The result of this experiment gives sufficient proof that the value is=+0.1.The authors wish to thank Mr. J. Holeek for his continuous help with the measurements and Ing. R. Michalec as well as other members of the Neutron Physics Department of our Institute for their interest and many helpful discussions.     

Supergravity in (2 + 1) dimensionsfrom (3 + 1)-dimensional supergravity

In the context of the formalism proposed by Stelle-West and Grignani-Nardelli, it is shown that Chern-Simons supergravity can be consistently obtained as a dimensional reduction of (3 + 1)-dimensional supergravity, when written as a gauge theory of the Poincaré group. The dimensional reductions are consistent with the gauge symmetries, mapping (3 + 1)-dimensional Poincaré supergroup gauge transformations onto (2 + 1)-dimensional Poincaré supergroup ones.     

Cyclic Representation of Quantum Group GL(2)q at qp=1 from the Regular Representation of M(2)q1

Regular representation of the matrix element algebra M(2)_q, of the quantum group GL(2)_q is studied, then the cyclic representation of GL(2)_q, is obtained as a quotient module of the regular representation of M(2)_q, with respect to some submodules at q^p = 1.     

Observation of the muon inner bremsstrahlung at?LEP1

Muon bremsstrahlung photons converted in front of the DELPHI main tracker (TPC) in dimuon events at LEP1 were studied in two photon kinematic ranges: 0.2<E _γ ≤1 GeV and transverse momentum with respect to the parent muon p _T <40 MeV/c, and 1<E _γ ≤10 GeV and p _T <80 MeV/c. A good agreement of the observed photon rate with predictions from QED for the muon inner bremsstrahlung was found, contrary to the anomalous soft photon excess that has been observed recently in hadronic Z ⁰ decays. The obtained ratios of the observed signal to the predicted level of the muon bremsstrahlung are 1.06±0.12±0.07 in the photon energy range 0.2<E _γ ≤1 GeV and 1.04±0.09±0.12 in the photon energy range 1<E _γ ≤10 GeV. The bremsstrahlung dead cone is observed for the first time in the direct photon production at LEP. Deceased.