Supersymmetric penguin contributions to the decay b\rightarrow s\gamma with non-universal squarks masses

We give explicit expressions for the amplitudes associated with the supersymmetric (SUSY) contributions to the process in the context of SUSY extensions of the standard model (SM) with non-universal soft SUSY breaking terms. From experimental data we deduce limits on the squark mass insertions obtained from different contributions (gluinos, neutralinos and charginos). Received: 20 April 2001 / Revised version: 14 December 2001 / Published online: 5 April 2002     

Simulating the Wess-Zumino supersymmetry model in optical lattices

We study a cold atom-molecule mixture in two-dimensional optical lattices. We show that, by fine-tuning the atomic and molecular interactions, the Wess-Zumino supersymmetry (SUSY) model in 2+1 dimensions emerges in the low-energy limit and can be simulated in such mixtures. At zero temperature, SUSY is not spontaneously broken, which implies identical relativistic dispersions of the atom and its superpartner, a bosonic diatom molecule. This defining signature of SUSY can be probed by single-particle spectroscopies. Thermal breaking of SUSY at a finite temperature is accompanied by a thermal Goldstone fermion, i.e., phonino excitation. This and other signatures of broken SUSY can also be probed experimentally.     

Hard and soft supersymmetry breaking for 'graphinos' in uniform magnetic fields

Using irreducible and reducible representations of the Dirac matrices, we study the two- and four-component quantum mechanical supersymmetric (SUSY) theories for ultrarelativistic fermions in .2 C 1/ dimensions ('graphinos') in a background uniform magnetic field perpendicular to their plane of motion. We then consider ordinary and parity-violating mass terms and identify the former as a soft SUSY breaking term and the latter as the hard SUSY breaking one.     

二维超对称模型的超对称破缺和Witten指数

构造了一类超势W=(1/n)gφⁿ的二维O(N)对称超对称模型,详细计算了此类模型的Witten指数△。结果表明,当n为偶数时,超对称一定不能破缺,而当n为奇数时,超对称可以破缺。利用大N展开法,还研究了上述模型的超对称自发破缺机制,同时给出了相应的粒子谱。 关键词：     

Flux of Scalar Neutrino Dark Matter

Recently the exotic event observed at the Yunnan Cosmic Ray Station (YCRS) is reinterpreted as a neutral supersymmetric (SUSY) particle bombarding on proton to produce a charged SUSY particle which decays afterwards. The kinematics analysis determines the lower bounds of its mass and lifetime. Taking this bounds as inputs and following recent literatures to assume the scalar neutrino (sneutrino) as the main constituent of the cold SUSY dark matter, we calculate the flux of sneutrino at the earth detector in terms of the standard rate equation of cosmic matter.     

Detection of Supersymmetric Dark Matter

A re-analysis of a heavy charged particle production event observed at the cloudy chamber of the Yunnan Cosmic Ray Station (YCRS) in 1972 indicates that the mysterious heavy particle may be identified as a supersymmetric (SUSY) particle produced by a bombard of a neutral SUSY cosmic ray particle on proton. Based on the assumption, following the literatures that the neutral SUSYparticle which constitutes the main fiaction of the cold dark matter is scalar neutrino (sneutrino) or neutralino (photino), we evaluate the flux of such SUSY particles which gain sufficient energies via elastic scattering with charged cosmic particles on the way to an Earth detector and the capture rates in both the sneutrino and photino cases respectively. The errors appearing in the study are briefly discussed and this work may provide a basis of designing cosmic ray detectors to search for SUSY particles from the heaven.     

Search for supersymmetric mesinos near production threshold in terms of superf lavor symmetry

Supersymmetry(SUSY) may be one of the most favored extensions of the Standard Model(SM), but so far at the LHC no evidence of SUSY particles has been observed.An obvious question is whether they have already emerged but escaped our detection, or whether they do not exist at all.We propose that the future ILC may provide sufficient energy and luminosity to produce SUSY particles as long as they are not too heavy.Superflavor symmetry associates production rates of SUSY mesinos with those of regular mesons, because both contain a heavy constituent and a light one.In this work, we estimate the production rate of SUSY mesinos near their production threshold and compare it with B production.Our analysis indicates that if SUSY mesinos with masses below s~(1/2)/2(s~(1/2) is the ILC energy) exist, they could be observed at the future ILC or even the proposed CEPC in China.     

From flavour to SUSY flavour models

If supersymmetry (SUSY) will be discovered, successful models of flavour not only have to provide an explanation of the flavour structure of the Standard Model fermions, but also of the flavour structure of their scalar superpartners. We discuss aspects of such “SUSY flavour” models, towards predicting both flavour structures, in the context of supergravity (SUGRA). We point out the importance of carefully taking into account SUSY-specific effects, such as 1-loop SUSY threshold corrections and canonical normalisation, when fitting the model to the data for fermion masses and mixings. This entangles the flavour model with the SUSY parameters and leads to interesting predictions for the sparticle spectrum. We demonstrate these effects by analyzing an example class of flavour models in the framework of an SU(5) Grand Unified Theory with a family symmetry with real triplet representations. For flavour violation through the SUSY soft breaking terms, the class of models realises a scheme we refer to as “Trilinear Dominance”, where flavour violation effects are dominantly induced by the trilinear terms.     

Runaway Directions in O'Raifeartaigh Models

R-symmetries, which are needed for supersymmetry (SUSY) breaking in O’Raifeartaigh models, often lead to SUSY runaway directions trough a complexified R-transformation. Non-R symmetries also lead to runaway directions in a similar way. This work investigates the occurrence of runaway directions of both SUSY and SUSY breaking types. We clarify previous issues on fractional charges and genericness, and make a refined statement on conditions for runaway directions related to either R-symmetries or non-R symmetries. We present a generic and anomaly-free model to show the existence of runaway directions related to non-R symmetries. We also comment on the possibility to combine the non-R symmetry case to the R-symmetry case by an R-charge redefinition.     

The supersymmetric Ward identities on the lattice

Supersymmetric (SUSY) Ward identities are considered for the N=1 SU(2) SUSY Yang-Mills theory discretized on the lattice with Wilson fermions (gluinos). They are used in order to compute non-perturbatively a subtracted gluino mass and the mixing coefficient of the SUSY current. The computations were performed at gauge coupling and hopping parameter , 0.194, 0.1955 using the two-step multi-bosonic dynamical-fermion algorithm. Our results are consistent with a scenario where the Ward identities are satisfied up to O(a) effects. The vanishing of the gluino mass occurs at a value of the hopping parameter which is not fully consistent with the estimate based on the chiral phase transition. This suggests that, although SUSY restoration appears to occur close to the continuum limit of the lattice theory, the results are still affected by significant systematic effects. Received: 8 November 2001 / Revised version: 14 January 2001 / Published online: 15 March 2002     

Measuring gauge-mediated supersymmetry breaking parameters at a 500 GeV e^+e^- linear collider

We consider the phenomenology of a class of gauge-mediated supersymmetry (SUSY) breaking (GMSB) models at a Linear Collider (LC) with up to 500 GeV. In particular, we refer to a high-luminosity ( cm s) machine, and use detailed simulation tools for a proposed detector. Among the GMSB-model building options, we define a simple framework and outline its predictions at the LC, under the assumption that no SUSY signal is detected at LEP or Tevatron. We assess the potential of the LC to distinguish between the various SUSY model options and to measure the underlying parameters with high precision, including for those scenarios where a clear SUSY signal would have already been detected at the LHC before starting the LC operations. Our focus is on the case where a neutralino () is the next-to-lightest SUSY particle (NLSP), for which we determine the relevant regions of the GMSB parameter space. Many observables are calculated and discussed, including production cross sections, NLSP decay widths, branching ratios and distributions, for dominant and rare channels. We sketch how to extract the messenger and electroweak scale model parameters from a spectrum measured via, e.g. threshold-scanning techniques. Several experimental methods to measure the NLSP mass and lifetime are proposed and simulated in detail. We show that these methods can cover most of the lifetime range allowed by perturbativity requirements and suggested by cosmology in GMSB models. Also, they are relevant for any general low-energy SUSY breaking scenario. Values of as short as 10's of m and as long as 10's of m can be measured with errors at the level of 10% or better after one year of LC running with high luminosity. We discuss how to determine a narrow range () for the fundamental SUSY breaking scale , based on the measured , . Finally, we suggest how to optimise the LC detector performance for this purpose. Received: 19 May 1999 / Published online: 8 December 1999     

Smuon in the NMSSM confronted with the muon g–2 anomaly and SUSY searches

Motivated by recent supersymmetry (SUSY) search results, which prefer most SUSY particles to be heavy, and the muon g–2 anomaly, which prefers colorless SUSY particles to be light, we explore the status of a light smuon (the SUSY partner of a left-handed muon lepton) in the next-to-minimal supersymmetric standard model (NMSSM). Assuming colored SUSY particles to be heavy, and considering numerous experimental constraints, including muon g-2, SUSY searches, and dark matter, we scan the parameter space in the NMSSM with \begin{document}$ \mathbb{Z}_3 $\end{document}-symmetry and check the status of colorless SUSY particles and their possible mass order, paying special attention to the smuon. After calculations and discussions, we find that the surviving samples can be divided into several scenarios, where the mass region and decay information of the smuon are given. Overall, the smuon mass can be approximately 0.1~1.8 TeV. These results may be useful for smuon searches at the LHC and future colliders.     

A generalized positive energy theorem for spaces with asymptotic SUSY compactification

In this short note, we prove a generalized positive energy theorem for spaces with asymptotic SUSY compactification involving non-symmetric data. This work is motivated by the work of Dai [A positive mass theorem for spaces with asymptotic SUSY compactification, Comm. Math. Phys. 244 (2004) 335–345; A note on positive energy theorem for spaces with asymptotic SUSY compactification, 2004. arXiv:math-ph/0406006], Hertog–Horowitz–Maeda [Negative energy density in Calabi–Yau compactifications, JHEP 0305 (2003) 060], and Zhang [Angular momentum and positive mass theorem, Comm. Math. Phys. 206 (1999) 137–155].     

Unification of Laughlin and Moore-Read states in SUSY quantum Hall effect

Based on the recently proposed SUSY quantum Hall effect, we show that Laughlin and Moore-Read states are related by a hidden SUSY transformation. Regarding the SUSY Laughlin wavefunction as a master wavefunction, Laughlin and Moore-Read states appear as two extreme limits of component wavefunctions. Realizations of topological excitations on Laughlin and Moore-Read states are also discussed in the SUSY formalism. We develop a stereographically projected formulation of the SUSY quantum Hall effect. With appropriate interpretation of Grassmann odd coordinates, we illustrate striking analogies between SUSY quantum Hall effect and superfluidity.     

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.     

Neutrino magnetic moment inN=1 minimal supergravity

The complete one-loop supersymmetric (SUSY) correction to the magnetic moment (NMM) of a Dirac neutrino is calculated with allowance for mixing between the scalar leptons and for mixing between theW-gaugino and Higgs fermions. The contribution from the charged Higgs loop is negligible for all practical purpose. We thoroughly study the dependence of NMM on the SUSY parameters. The SUSY contribution to the NMM can be a few times less than or comparable to the value of the standard model (with a right-handed neutrino singlet added). The SUSY correction to the NMM increases with decreasing β value (tan β=〈H ₂〉/〈H ₁〉), and is not very sensitive to the charged scalar lepton mass.     

Non-linear supersymmetry for non-Hermitian,non-diagonalizable Hamiltonians: I. General properties

We study complex potentials and related non-diagonalizable Hamiltonians with special emphasis on formal definitions of associated functions and Jordan cells. The non-linear SUSY for complex potentials is considered and the theorems characterizing its structure are presented. We define the class of complex potentials invariant under SUSY transformations for (non-)diagonalizable Hamiltonians and formulate several results concerning the properties of associated functions. We comment on the applicability of these results for softly non-Hermitian PT-symmetric Hamiltonians. The role of SUSY (Darboux) transformations in increasing/decreasing of Jordan cells in SUSY partner Hamiltonians is thoroughly analyzed and summarized in the Index Theorem. The properties of non-diagonalizable Hamiltonians as well as the Index Theorem are illustrated in the solvable examples of non-Hermitian reflectionless Hamiltonians. The rigorous proofs are relegated to part II of this paper. At last, some peculiarities in resolution of identity for discrete and continuous spectra with a zero-energy bound state at threshold are discussed.     

Super Yang–Mills theory from nonlinear supersymmetry

The relation between a nonlinear supersymmetric (NLSUSY) theory and a SUSY Yang–Mills (SYM) theory is studied for N=3$N=3$ SUSY in two-dimensional space–time. We explicitly show the NL/L SUSY relation for the (pure) SYM theory by means of cancellations among Nambu–Goldstone fermion self-interaction terms.     

Spontaneous supersymmetry breaking in matrix models from the viewpoints of localization and Nicolai mapping

In the previous work, it was shown that, in supersymmetric (matrix) discretized quantum mechanics, inclusion of an external field twisting the boundary condition of fermions enables us to discuss spontaneous breaking of supersymmetry (SUSY) in the path-integral formalism in a well-defined way. In the present work, we continue investigating the same systems from the points of view of localization and Nicolai mapping. The localization is studied by changing of integration variables in the path integral, which is applicable whether or not SUSY is explicitly broken. We examine in detail how the integrand of the partition function with respect to the integral over the auxiliary field behaves as the auxiliary field vanishes, which clarifies a mechanism of the localization. In SUSY matrix models, we obtain a matrix-model generalization of the localization formula. In terms of eigenvalues of matrix variables, we observe that eigenvalues' dynamics is governed by balance of attractive force from the localization and repulsive force from the Vandermonde determinant. The approach of the Nicolai mapping works even in the presence of the external field. It enables us to compute the partition function of SUSY matrix models for finite N (N is the rank of matrices) with arbitrary superpotential at least in the leading nontrivial order of an expansion with respect to the small external field. We confirm the restoration of SUSY in the large-N limit of a SUSY matrix model with a double-well scalar potential observed in the previous work.     

On Wess–Zumino gauge

In the relation between the linear (L) supersymmetry (SUSY) representation and the nonlinear (NL) SUSY representation we discuss the role of the Wess–Zumino gauge. We show in two-dimensional spacetime that a spontaneously broken LSUSY theory with mass and Yukawa interaction terms for a minimal off-shell vector supermultiplet is obtained from a general superfield without imposing any special gauge conditions in N=2$N=2$ NL/L SUSY relation.