148 research outputs found

    A Poisson process approximation for generalized K-5 confidence regions

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    One-sided confidence regions for continuous cumulative distribution functions are constructed using empirical cumulative distribution functions and the generalized Kolmogorov-Smirnov distance. The band width of such regions becomes narrower in the right or left tail of the distribution. To avoid tedious computation of confidence levels and critical values, an approximation based on the Poisson process is introduced. This aproximation provides a conservative confidence region; moreover, the approximation error decreases monotonically to 0 as sample size increases. Critical values necessary for implementation are given. Applications are made to the areas of risk analysis, investment modeling, reliability assessment, and analysis of fault tolerant systems

    Vacuum Stability and Triviality Analyses of the Renormalizable Coloron Model

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    The renormalizable coloron model is built around a minimally extended color gauge group, which is spontaneously broken to QCD. The formalism introduces massive color-octet vector bosons (colorons), as well as several new scalars and fermions associated with the symmetry breaking sector. In this paper, we examine vacuum stability and triviality conditions within the context of the renormalizable coloron model up to a cutoff energy scale of 100~TeV, by computing the beta-functions of all relevant couplings and determining their running behavior as a function of the renormalization scale. We constrain the parameter space of the theory for four separate scenarios based on differing fermionic content, and demonstrate that the vectorial scenarios are less constrained by vacuum stability and triviality bounds than the chiral scenarios. Our results are summarized in exclusion plots for the separate scenarios, with previous bounds on the model overlaid for comparison. We find that a 100 TeV hadron collider could explore the entire allowed parameter space of the chiral models very effectively.Comment: 17 pages, embedded color pdf figures. Typos corrected and appendix on fermion charges and mass generation adde

    Constraints on the Scalar Sector of the Renormalizable Coloron Model

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    The renormalizable coloron model is the minimal extension of the standard model color sector, in which the color gauge group is enlarged to SU(3)_{1c} x SU(3)_{2c}. In this paper we discuss the constraints on this model derived from the requirements of vacuum stability, tree-level unitarity, electroweak precision measurements, and from LHC measurements of the properties of the observed Higgs-like scalar boson. The combination of these theoretical and experimental considerations strongly constrains the allowed parameter space. (Erratum appended, March 2014.)Comment: 20 pages, pdf included figures. Brief phenomenological analysis of additional scalar s-boson added. Erratum appended: an error in the Higgs-boson gluon-fusion production amplitude arising from the new colored states is corrected, resulting in stronger constraints on the model parameter spac

    Global Symmetries and Renormalizability of Lee-Wick Theories

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    In this paper we discuss the global symmetries and the renormalizibility of Lee-Wick scalar QED. In particular, in the "auxiliary-field" formalism we identify softly broken SO(1,1) global symmetries of the theory. We introduce SO(1,1) invariant gauge-fixing conditions that allow us to show in the two-field formalism directly that the number of superficially divergent amplitudes in a LW Abelian gauge theory is finite. To illustrate the renormalizability of the theory, we explicitly carry out the one-loop renormalization program in LW scalar QED and demonstrate how the counterterms required are constrained by the joint conditions of gauge- and SO(1,1)-invariance. We also compute the one-loop beta-functions in LW scalar QED and contrast them with those of ordinary scalar QED.Comment: 17 pages, 3 eps figures included. Incorporates suggestions by referee; title change

    Diphoton Resonances in the Renormalizable Coloron Model

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    The renormalizable coloron model, which has previously been shown in the literature to be consistent with a wide array of theoretical and precision electroweak constraints, includes a pair of spinless bosons (one scalar, one pseudoscalar). We show that either of them, or both together if they are degenerate, could be responsible for the diphoton resonance signal for which both CMS and ATLAS have seen evidence. Because either of these bosons would be produced and decay through loops of spectator fermions, the absence of signals in dijet, ttˉt\bar{t}, and electroweak boson pair channels is not a surprise.Comment: 18 pages, 5 figures. (Modified to respond to referee comments, discussion of Landau poles in scalar couplings added.

    Hadron Collider Production of Massive Color-Octet Vector Bosons at Next-to-Leading Order

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    This paper completes the study of the next-to-leading order (NLO) QCD corrections to massive color-octet vector boson production at the LHC and Tevatron. The massive color-octet vector bosons are generically referred to as colorons. Building on our previous calculation of quark-initiated coloron production at NLO, we use the pinch technique to investigate coloron production via gluon fusion. We demonstrate that this one-loop production amplitude is finite, and find that its numerical contribution to coloron production is typically four orders of magnitude smaller than the contribution from quark annihilation. Coloron production via gluon fusion is therefore only relevant if the colorons are (nearly) fermiophobic. We then present extensive plots and tables of our full results for NLO coloron production at the Tevatron and the LHC.Comment: 22 pages, pdf figures included (references added

    Custodial Isospin Violation in the Lee-Wick Standard Model

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    We analyze the tension between naturalness and isospin violation in the Lee-Wick Standard Model (LW SM), by computing tree-level and fermionic one-loop contributions to the post-LEP electroweak parameters and the Zbb coupling. The model is most natural when the LW partners of the gauge bosons and fermions are light, but small partner masses can lead to large isospin violation. The post-LEP parameters yield a simple picture in the LW SM: the gauge sector contributes to Y and W only, with leading contributions arising at tree-level, while the fermion sector contributes to S-hat and T-hat only, with leading corrections arising at one loop. Hence, W and Y constrain the masses of the LW gauge bosons to satisfy M1, M2 > 2.4 TeV at 95% CL. Likewise, experimental limits on T-hat reveal that the masses of the LW fermions must satisfy Mq, Mt > 1.6 TeV at 95% CL if the Higgs mass is light and tend to exclude the LW SM for any LW fermion masses if the Higgs mass is heavy. Contributions from the top-quark sector to the Zbb coupling can be even more stringent, placing a lower bound of 4 TeV on the LW fermion masses at 95% CL.Comment: 16 pages, 8 embedded eps figure

    Coloron Models and LHC Phenomenology

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    This talk discusses the possibility of new physics within the strong gauge interactions, specifically the idea of an extended color gauge group that is spontaneously broken to QCD. After a brief review of the literature, three of our recent pieces of work on coloron phenomenology are summarized. First, some key results on coloron production to NLO at hadron colliders are described. Next, a method of using associated production of colorons and weak vector bosons to better determine coloron couplings is discussed. Finally, a new model that naturally realizes flavor physics is reviewed.Comment: 15 pages; 5 figures; contribution to SCGT12 "KMI-GCOE Workshop on Strong Coupling Gauge Theories in the LHC Perspective", 4-7 Dec. 2012, Nagoya University; new version fixes several minor text typos (including in one reference
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