Selectron Pair Production at e-e- and e+e- Colliders with Polarized Beams

We investigate selectron pair production and decay in e-e- scattering and e+e- annihilation with polarized beams taking into account neutralino mixing as well as ISR and beamstrahlung corrections. One of the main advantages of having both modes at disposal is their complementarity concerning the threshold behaviour of selectron pair production. In e-e- the cross sections at threshold for seleectron_R selectron_R and selectron_L selectron_L rise proportional to the momentum of the selectron and in e+ e- that for selectron_R selectron_L. Measurements at threshold with polarized beams can be used to determine the selectron masses precisely. Moreover we discuss how polarized electron and positron beams can be used to establish directly the weak quantum numbers of the selectrons. We also use selectron pair production to determine the gaugino mass parameter M_1. This is of particular interest for scenarios with non-universal gaugino masses at a high scale resulting in |M_1| << |M_2| at the electroweak scale. Moreover, we consider also the case of a non-vanishing selectron mixing and demonstrate that it leads to a significant change in the phenomenology of selectrons.Comment: LaTex, 23 pages, 14 figures, v2, typos corrected, version to appear in Eur.Phys.J.

Understanding Spectrum Education and Workforce Needs

Texas A&M University leads a multi-institutional collaboration funded by a National Science Foundation (NSF) planning grant to develop a comprehensive research plan for a National Center for Spectrum Innovation. NSF plans to invest $25 million over five years to stand up a national center, one that is operational within two years. The center’s goals are to conduct critical convergence-based research and technology development; serve as a hub for collaborative engagements; educate the workforce; propose appropriate policies, standards, and regulations; advance relevant economic issues; and address ethical issues, including attending to the needs of populations currently underserved by spectrum-related technologies. To inform the planning grant’s education and workforce efforts, the Business-Higher Education Forum (BHEF) developed this report to share preliminary findings from its background research and interviews, which subsequently informed a more comprehensive quantitative analysis of job postings data on current and emerging spectrum occupations, highlighting top skills, top employers, top industries, and top locations. The report demonstrates the broad, diverse, and high-demand landscape of spectrum’s current and future education and workforce needs

Event shape discrimination of supersymmetry from large extra dimensions at a linear collider

The production of a charged lepton (e/mu) pair with a large missing energy at a linear collider is discussed as a means of distinguishing the minimal supersymmetry (MSSM) scenario from that with large extra dimensions (ADD) for parameter ranges where the total cross sections are comparable for both. Analyses in terms of event shape variables, specifically sphericity and thrust, are shown to enable a clear discrimination in this regard.Comment: LaTex 13 pages, 11 figures, 1 table. Some clarifications and additions are made and also results for CLIC include

CP violation through particle mixing and the H-A lineshape

We consider the possibility of looking for CP-mixing effects in two-Higgs doublet models (and particularly in the MSSM) by studying the lineshape of the CP-even (H) and CP-odd (A) neutral scalars. In most cases H and A come quite degenerate in mass, and their s-channel production would lead to nearly overlapping resonances. CP-violating effects may connect these two Higgs bosons, giving origin to one-loop particle mixing, which, due to their mass proximity, can be resonantly enhanced. The corresponding transition amplitude contains then CP-even and CP-odd components; besides the signal of intereference between both amplitudes, leading to a CP-odd asymmetry, we propose to look for the mixing probability itself, a quantity which, although CP-even, can originate only from a CP-odd amplitude. We show that, in general, the effect of such a mixing probability cannot be mimicked by (or be re-absorbed into) a simple redefinition of the H and A masses in the context of a CP-conserving model. Specifically, the effects of the CP-mixing are such that, either the mass-splitting of the H and A bosons cannot be accounted for in the absence of CP-mixing, and/or the detailed energy dependence of the produced lineshape is clearly different from the one obtained by redefining the masses, but not allowing any mixing. This analysis suggests that the detailed study of the lineshape of this Higgs system may provide valuable information on the CP nature of the underlying theory.Comment: 16 pages, 13 figures; v2: added one reference; v3: radiative corrections taken into account, agreement now with CP-SuperH, conclusions unchanged. v3 matches the paper version accepted for publication in JHE

Refining the predictions of supersymmetric CP-violating models: A top-down approach

We explore in detail the consequences of the CP-violating phases residing in the supersymmetric and soft SUSY breaking parameters in the approximation that family flavour mixings are ignored. We allow for non-universal boundary conditions and in such a consideration the model is described by twelve independent CP-violating phases and one angle which misaligns the vacuum expectation values (VEVs) of the Higgs scalars. We run two-loop renormalization group equations (RGEs), for all parameters involved, including phases, and we properly treat the minimization conditions using the one-loop effective potential with CP-violating phases included. We show that the two-loop running of phases may induce sizable effects for the electric dipole moments (EDMs) that are absent in the one-loop RGE analysis. Also important corrections to the EDMs are induced by the Higgs VEVs misalignment angle which are sizable in the large tanb region. Scanning the available parameter space we seek regions compatible with accelerator and cosmological data with emphasis on rapid neutralino annihilations through a Higgs resonance. It is shown that large CP-violating phases, as required in Baryogenesis scenarios, can be tuned to obtain agreement with WMAP3 cold dark matter constraints, EDMs and all available accelerator data, in extended regions of the parameter space which may be accessible to LHC.Comment: 41 pages, 22 eps figures. A reference added and a typo corrected; version to appear in JHE

Spin Asymmetries in Squark and Gluino Production at Polarized Hadron Colliders

We study the production cross sections for squarks and gluinos in collision of longitudinally polarized hadrons. The corresponding polarized partonic cross sections are computed in leading order supersymmetric QCD. The resulting asymmetries are evaluated for the polarized proton collider RHIC, as well as for hypothetical polarized options of the Tevatron and the LHC. These asymmetries turn out to be sizable over a wide range of supersymmetric particle masses, thus potentially opening a window to detailed sparticle spectroscopy at future polarized hadron colliders.Comment: 25 pages, LaTeX, typos correcte

Diversification and Intensification in Parallel {SAT} Solving

International audienceIn this paper, we explore the two well-known principles of diversification and intensification in portfolio-based parallel SAT solving. These dual concepts play an important role in several search algorithms including local search, and appear to be a key point in modern parallel SAT solvers. To study their trade-off, we define two roles for the computational units. Some of them classified as Masters perform an original search strategy, ensuring diversification. The remaining units, classified as Slaves are there to intensify their master's strategy. Several important questions have to be answered. The first one is what information should be given to a slave in order to intensify a given search effort? The second one is, how often, a subordinated unit has to receive such information? Finally, the question of finding the number of subordinated units along their connections with the search efforts has to be answered. Our results lead to an original intensification strategy which outperforms the best parallel SAT solver, and solves some open SAT instances

Threshold corrections to m_b and the b\bar{b} -> H^0_i production in CP-violating SUSY scenarios

The inclusion of supersymmetric threshold corrections to the $b$-quark mass has dramatic consequences in scenarios with large CP-mixing effects in the Higgs sector. In particular, when the phase of the combination $M_{\tilde{g}}\mu$ is $\sim 180^{\rm o} \pm 30^{\rm o}$, the lightest-sbottom squark becomes tachyonic and, possibly, the $b$-quark Yukawa coupling nonperturbative for values of $\tan \beta$ ranging from intermediate up to large or very large, depending on the size of $arg(A_t\mu)$, $arg(A_b\mu)$, and the details of the spectrum. For these scenarios, when allowed, as well as scenarios with different values of $arg(M_{\tilde{g}}\mu)$, the cross sections for the production of the three neutral-Higgs bosons through $b$-quark have rather interesting dependences on $arg(A_t\mu)$ and $arg(A_b\mu)$, and the deviations induced by the $m_b$ corrections are rather large. In general, such production channel cannot be neglected with respect to the production through gluon fusion. For large CP-mixing effects, the lightest neutral-Higgs boson can be mainly CP odd and the $b$-quark fusion becomes its main production mechanism. Searches at the Tevatron and the LHC can easily detect such a Higgs boson, or constrain the CP-violating scenarios that allow it.Comment: 1+15 pages, 5 figures, References added. Extended discussion of the b-b-Higgs couplings, to appear in Phys. Lett.

Probing neutrino properties with charged scalar lepton decays

Supersymmetry with bilinear R-parity violation provides a predictive framework for neutrino masses and mixings in agreement with current neutrino oscillation data. The model leads to striking signals at future colliders through the R-parity violating decays of the lightest supersymmetric particle. Here we study charged scalar lepton decays and demonstrate that if the scalar tau is the LSP (i) it will decay within the detector, despite the smallness of the neutrino masses, (ii) the relative ratio of branching ratios Br({tilde tau}_1 --> e sum nu_i)/ Br({tilde tau}_1 --> mu sum nu_i) is predicted from the measured solar neutrino angle, and (iii) scalar muon and scalar electron decays will allow to test the consistency of the model. Thus, bilinear R-parity breaking SUSY will be testable at future colliders also in the case where the LSP is not the neutralino.Comment: 24 pages, 8 ps figs Report-no.: IFIC/02-33 and ZU-TH 11/0

CP violation in selectron cascade decays e_L -> e X_2^0 -> e X_1^0 mu+ mu-

Selectron decays constitute a source of 100% polarised neutralinos, whose helicity is fixed by the charge and "chirality" of the decaying selectron. In SUSY scenarios where the second neutralino X_2^0 has three-body decays, the cascade decay e_L -> e X_2^0 -> e X_1^0 mu+ mu- provides a clean place to study CP violation in the neutralino sector, through the analysis of CP-violating asymmetries involving the X_2^0 spin s and the momenta of the muons. We show that a CP-violating asymmetry in the triple product s . (p_mu- x p_mu+) could be observable at a 800 GeV linear collider provided the gaugino mass M_1 has a large phase at the electroweak scale. We compare our results with X_1^0 X_2^0 production, where a CP asymmetry is also observable within these scenarios.Comment: LaTeX 14 pages, 9 figures. Removed section 5 (which is included in Ref. [33]), improved discussion of backgrounds and added comments and references. To be published in Phys. Lett.