A comparison of analysis techniques for extracting resonance parameters from lattice Monte Carlo data

Different methods for extracting resonance parameters from Euclidean lattice field theory are tested. Monte Carlo simulations of the O(4) non-linear sigma model are used to generate energy spectra in a range of different volumes both below and above the inelastic threshold. The applicability of the analysis methods in the elastic region is compared. Problems which arise in the inelastic region are also emphasised.Comment: 17 pages, 20 figures; clarification and minor corrections added, to appear in PR

B -> X_s gamma in supersymmetry: large contributions beyond the leading order

We discuss possible large contributions to B -> X_s gamma, which can occur at the next-to-leading order in supersymmetric models. They can originate from terms enhanced by tan(beta) factors, when the ratio between the two Higgs vacuum expectation values is large, or by logarithm of M_{susy}/M_W, when the supersymmetric particles are considerably heavier than the W boson. We give compact formulae which include all potentially large higher-order contributions. We find that tan(beta) terms at the next-to-leading order do not only appear from the Hall-Rattazzi-Sarid effect (the modified relation between the bottom mass and Yukawa coupling), but also from an analogous effect in the top-quark Yukawa coupling. Finally, we show how next-to-leading order corrections, in the large tan(beta) region, can significantly reduce the limit on the charged-Higgs mass, even if supersymmetric particles are very heavy.Comment: 18 pages, 5 figs, extended discussion of light stop case, notational improvement

Witten index and phase diagram of compactified N=1 supersymmetric Yang-Mills theory on the lattice

Owing to confinement, the fundamental particles of N=1 Supersymmetric Yang-Mills (SYM) theory, gluons and gluinos, appear only in colourless bound states at zero temperature. Compactifying the Euclidean time dimension with periodic boundary conditions for fermions preserves supersymmetry, and confinement is predicted to persist independently of the length of the compactified dimension. This scenario can be tested non-perturbatively with Monte-Carlo simulations on a lattice. SUSY is, however, broken on the lattice and can be recovered only in the continuum limit. The partition function of compactified N=1 SYM theory with periodic fermion boundary conditions corresponds to the Witten index. Therefore it can be used to test whether supersymmetry is realized on the lattice. Results of our recent numerical simulations are presented, supporting the disappearance of the deconfinement transition in the supersymmetric limit and the restoration of SUSY at low energies.Comment: 7 pages, 3 figures, Proceedings of the 33rd International Symposium on Lattice Field Theory (Lattice 2015), 14-18 July 2015, Kobe International Conference Center, Kobe, Japa

Progress in weakly coupled string phenomenology

The weakly coupled vacuum of $E_8\otimes E_8$ heterotic string theory remains an attractive scenario for particle physics. The particle spectrum and the issue of dilaton stabilization are reviewed. A specific model for hidden sector condensation and supersymmetry breaking, that respects known constraints from string theory, is described, and its phenomenological and cosmological implications are discussed.Comment: 15 pages, full postscript also available from http://phyweb.lbl.gov/theorygroup/papers/48640.p

Gluino Decays in Split Supersymmetry

We compute the gluino lifetime and branching ratios in Split Supersymmetry. Using an effective-theory approach, we resum the large logarithmic corrections controlled by the strong gauge coupling and the top Yukawa coupling. We find that the resummation of the radiative corrections has a sizeable numerical impact on the gluino decay width and branching ratios. Finally, we discuss the gluino decays into gravitino, relevant in models with direct mediation of supersymmetry breaking.Comment: 21 pages, 6 figure

Phase structure of the N=1 supersymmetric Yang-Mills theory at finite temperature

Supersymmetry (SUSY) has been proposed to be a central concept for the physics beyond the standard model and for a description of the strong interactions in the context of the AdS/CFT correspondence. A deeper understanding of these developments requires the knowledge of the properties of supersymmetric models at finite temperatures. We present a Monte Carlo investigation of the finite temperature phase diagram of the N=1 supersymmetric Yang-Mills theory (SYM) regularised on a space-time lattice. The model is in many aspects similar to QCD: quark confinement and fermion condensation occur in the low temperature regime of both theories. A comparison to QCD is therefore possible. The simulations show that for N=1 SYM the deconfinement temperature has a mild dependence on the fermion mass. The analysis of the chiral condensate susceptibility supports the possibility that chiral symmetry is restored near the deconfinement phase transition.Comment: 26 pages, 12 figure

PeV-Scale Supersymmetry

Although supersymmetry has not been seen directly by experiment, there are powerful physics reasons to suspect that it should be an ingredient of nature and that superpartner masses should be somewhat near the weak scale. I present an argument that if we dismiss our ordinary intuition of finetuning, and focus entirely on more concrete physics issues, the PeV scale might be the best place for supersymmetry. PeV-scale supersymmetry admits gauge coupling unification, predicts a Higgs mass between 125 GeV and 155 GeV, and generally disallows flavor changing neutral currents and CP violating effects in conflict with current experiment. The PeV scale is motivated independently by dark matter and neutrino mass considerations.Comment: 5 RevTex page

Complejidad y dimensiones en los estudios sobre Babbage: la máquina analítica. Un análisis del fracaso cultural del primer proyecto de calculadora digital programable secuencialmente.

En este artículo se analiza el caso histórico de la máquina analítica de Babbage junto con algunos otros ejemplos relacionados, con la intención de comprender qué tipo de condiciones retrasaron el advenimiento de la > hasta un siglo después de los primeros diseños de calculadoras programables multi-propósito. La respuesta a este interrogante proviene de una hibridación entre el enfoque socioeconómico de los estudios de ciencia, tecnología y sociedad y la teoría de la complejidad aplicada a los fenómenos sociales en la historia de la técnica. Como conclusión se prueba que el propio Babbage pudo ser consciente de estas constricciones en la estructura social de los medios de producción que retrasarían la emergencia del cálculo automático durante un siglo.This article analyses the historical case of the Babbage's machine and other related examples in order to understand the conditions delaying the coming of the •computer revolution· during one century since the first designs of programmable calculators. The response derives from the joining of both che STS socioeconomic approach and the complexity theory applied to social phenomena in the history of technology. As a result, it is showed that Babbage could be conscious of these constrictions in the social structure, which would be responsible for the delay of the emergence of automatic calculus during one century