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Jun 30, 2018
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Jun 30, 2018
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Bridget Bertoni; Seyda Ipek; David McKeen; Ann E. Nelson
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Cold dark matter explains a wide range of data on cosmological scales. However, there has been a steady accumulation of evidence for discrepancies between simulations and observations at scales smaller than galaxy clusters. Solutions to these small scale structure problems may indicate that simulations need to improve how they include feedback from baryonic matter, or may imply that dark matter properties differ from the standard cold, noninteracting scenario. One promising way to affect...
Topics: High Energy Physics - Experiment, High Energy Physics - Phenomenology, Astrophysics, Cosmology and...
Source: http://arxiv.org/abs/1412.3113
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4.0
Jun 30, 2018
06/18
Jun 30, 2018
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Seyda Ipek; David McKeen; Ann E. Nelson
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Supersymmetric theories with a $U(1)_R$ symmetry have Dirac gauginos, solve the supersymmetric flavor and CP problems, and have distinctive collider signatures. However when supergravity is included, the $U(1)_R$ must be broken, adding small Majorana mass terms which split the mass of the two components of the Dirac gaugino and lead to oscillations between $U(1)_R$ charge eigenstates. We present a general study of fermion-antifermion oscillations in this system, including the effects of decays...
Topics: High Energy Physics - Phenomenology, High Energy Physics - Experiment
Source: http://arxiv.org/abs/1407.8193
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Jun 30, 2018
06/18
Jun 30, 2018
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Akshay Ghalsasi; Ann E. Nelson
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In models with a light scalar field (the `acceleron') coupled to neutrinos, neutrino masses depend on neutrino density. The resulting coupled system of mass varying neutrinos (MaVaNs) and the acceleron can act as a negative pressure fluid and is a candidate for dark energy \cite{Fardon:2003eh} . MaVaNs also allow for higher $\Sigma$m$_\nu$ than terrestrial bounds, giving late forming warm dark matter. In this paper we study the effect of increasing neutrino mass on the CMB spectrum,...
Topics: High Energy Physics - Experiment, High Energy Physics - Phenomenology, Astrophysics, Cosmology and...
Source: http://arxiv.org/abs/1405.0711
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4.0
Jun 30, 2018
06/18
Jun 30, 2018
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Seyda Ipek; David McKeen; Ann E. Nelson
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Evidence for an excess of gamma rays with O(GeV) energy coming from the center of our galaxy has been steadily accumulating over the past several years. Recent studies of the excess in data from the Fermi telescope have cast doubt on an explanation for the excess arising from unknown astrophysical sources. A potential source of the excess is the annihilation of dark matter into standard model final states, giving rise to gamma ray production. The spectrum of the excess is well fit by 30 GeV...
Topics: High Energy Physics - Phenomenology, High Energy Astrophysical Phenomena, Astrophysics
Source: http://arxiv.org/abs/1404.3716
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Jun 29, 2018
06/18
Jun 29, 2018
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Timothy Cohen; Graham D. Kribs; Ann E. Nelson; Bryan Ostdiek
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Motivated by the recent excess in the diphoton invariant mass near 750 GeV, we explore a supersymmetric extension of the Standard Model that includes the minimal set of superpartners as well as additional Dirac partner chiral superfields in the adjoint representation for each gauge group. The bino partner pseudoscalar is identified as the 750 GeV resonance, while superpotential interactions between it and the gluino (wino) partners yield production via gluon fusion (decay to photon pairs) at...
Topics: High Energy Physics - Phenomenology, High Energy Physics - Experiment
Source: http://arxiv.org/abs/1605.04308
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Jun 28, 2018
06/18
Jun 28, 2018
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David McKeen; Ann E. Nelson
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We enumerate the conditions necessary for $CP$ violation to be manifest in $n$-$\bar n$ oscillations, and build a simple model that can give rise to such effects. We discuss a possible connection between neutron oscillations and dark matter, provided the mass of the latter lies between $m_p-m_e$ and $m_p+m_e$. We apply our results to a possible baryogenesis scenario involving $CP$ violation in the oscillations of the $\Xi^0$.
Topic: High Energy Physics - Phenomenology
Source: http://arxiv.org/abs/1512.05359
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Jun 28, 2018
06/18
Jun 28, 2018
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Akshay Ghalsasi; David McKeen; Ann E. Nelson
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We propose a new mechanism for baryogenesis at the 1-200 MeV scale. Enhancement of CP violation takes place via interference between oscillations and decays of mesinos--bound states of a scalar quark and antiquark and their CP conjugates. We present the mechanism in a simplified model with four new fundamental particles, with masses between 300 GeV and 10 TeV, and show that some of the experimentally allowed parameter space can give the observed baryon-to-entropy ratio.
Topics: High Energy Physics - Phenomenology, Cosmology and Nongalactic Astrophysics, Astrophysics
Source: http://arxiv.org/abs/1508.05392
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Jun 26, 2018
06/18
Jun 26, 2018
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Ann E. Nelson; Tuhin S. Roy
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We propose the framework, "generalized supersoft supersymmetry breaking". "Supersoft" models, with $D$-type supersymmetry breaking and heavy Dirac gauginos, are considerably less constrained by the LHC searches than the well studied MSSM. These models also ameliorate the supersymmetric flavor and $CP$ problems. However, previously considered mechanisms for obtaining a natural size Higgsino mass parameter (namely, $\mu$) in supersoft models have been relatively complicated...
Topic: High Energy Physics - Phenomenology
Source: http://arxiv.org/abs/1501.03251
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Sep 23, 2013
09/13
Sep 23, 2013
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Ann E. Nelson; Matthew J. Strassler
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We describe a realistic, renormalizable, supersymmetric ``quindecuplet'' model in which the top quark, left handed bottom quark, and up-type Higgs boson are composite, with a compositeness scale $\sim 1-3$ TeV. The top-Higgs Yukawa coupling is a dynamically generated strong interaction effect, and is naturally much larger than any other Yukawa coupling. The light quark doublets and right-handed up-type quarks are also composite but at higher energies; the hierarchy of quark masses and mixings...
Source: http://arxiv.org/abs/hep-ph/9607362v1
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Sep 23, 2013
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Sep 23, 2013
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Ann E. Nelson; Jakub Scholtz
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We explore the possibility that the dark matter is a condensate of a very light vector boson. Such a condensate could be produced during inflation, provided the vector mass arises via the Steuckelberg mechanism. We derive bounds on the kinetic mixing of the dark matter boson with the photon, and point out several potential signatures of this model.
Source: http://arxiv.org/abs/1105.2812v3
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Sep 23, 2013
09/13
Sep 23, 2013
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Ann E. Nelson; Christopher Spitzer
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We present a simple model in which dark matter couples to the standard model through a light scalar intermediary that is itself unstable. We find this model has several notable features, and allows a natural explanation for a surplus of positrons, but no surplus of anti-protons, as has been suggested by early data from PAMELA and ATIC. Moreover, this model yields a very small nucleon coupling, well below the direct detection limits. In this paper we explore the effect of this model in both the...
Source: http://arxiv.org/abs/0810.5167v3
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Sep 23, 2013
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Sep 23, 2013
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D. Elazzar Kaplan; Francois Lepeintre; Antonio Masiero; Ann E. Nelson; Antonio Riotto
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We present a supersymmetric model of flavor. A single U(1) gauge group is responsible for both generating the flavor spectrum and communicating supersymmetry breaking to the visible sector. The problem of Flavor Changing Neutral Currents is overcome, in part using an `Effective Supersymmetry' spectrum among the squarks, with the first two generations very heavy. All masses are generated dynamically and the theory is completely renormalizable. The model contains a simple Froggatt-Nielsen sector...
Source: http://arxiv.org/abs/hep-ph/9806430v1
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Sep 23, 2013
09/13
Sep 23, 2013
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Ann E. Nelson
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Comparatively simple models, with low energy structure similar to that of the MSSM, but with far fewer arbitrary parameters, can be constructed in which supersymmetry is dynamically broken at low energies. The phenomenology of these models is somewhat different than that of the usual scenario with supersymmetry broken in a hidden sector.
Source: http://arxiv.org/abs/hep-ph/9511218v1
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Sep 23, 2013
09/13
Sep 23, 2013
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Ann E. Nelson
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We propose a simple and natural model of dynamical supersymmetry breaking, which could be used as a mechanism for spontaneous supersymmetry breaking in a gravitationally coupled hidden sector. The gaugino masses in the visible sector are naturally of the same size as the squark, slepton, and gravitino masses.
Source: http://arxiv.org/abs/hep-ph/9511350v1
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Sep 23, 2013
09/13
Sep 23, 2013
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Ann E Nelson
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We should be taking advantage of recent gains in our nonperturbative understanding of supersymmetric gauge theories to find the ``standard'' model of of dynamical supersymmetry breaking, and possibly of flavor as well. As an illustration of the possibilities for understanding the flavor hierarchy, I describe a realistic, renormalizable, supersymmetric model with a compositeness scale of $\sim 1-3$ TeV for the top quark, the left handed bottom quark, and the up-type Higgs. The top-Higgs Yukawa...
Source: http://arxiv.org/abs/hep-ph/9608254v1
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Sep 23, 2013
09/13
Sep 23, 2013
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Sichun Sun; David B. Kaplan; Ann E. Nelson
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We describe a model of quarks which identifies the large global symmetries of little Higgs models with the global flavor symmetries that arise in a deconstruction of the extra-dimensional 'topological insulator' model of flavor. The nonlinearly realized symmetries of little Higgs theories play a critical role in determining the flavor structure of fermion masses and mixing. All flavor physics occurs at the few TeV scale in this model, yet flavor changing neutral currents arising from the new...
Source: http://arxiv.org/abs/1303.1811v3
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Sep 23, 2013
09/13
Sep 23, 2013
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Emanuel Katz; Jaeyong Lee; Ann E. Nelson; Devin G. E. Walker
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We describe a natural UV complete theory with a composite little Higgs. Below a TeV we have the minimal Standard Model with a light Higgs, and an extra neutral scalar. At the TeV scale there are additional scalars, gauge bosons, and vector-like charge 2/3 quarks, whose couplings to the Higgs greatly reduce the UV sensitivity of the Higgs potential. Stabilization of the Higgs mass squared parameter, without finetuning, occurs due to a softly broken shift symmetry--the Higgs is a pseudo...
Source: http://arxiv.org/abs/hep-ph/0312287v2
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Sep 23, 2013
09/13
Sep 23, 2013
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Ann E Nelson
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I construct solutions to Einstein's equations in 6 dimensions with bulk cosmological constant and intersecting 4-branes. Solutions exist for a continuous range of 4-brane tension, with long distance gravity localized to a 3+1 dimensional Minkowski intersection, provided that the additional tension of the intersection satisfies one condition.
Source: http://arxiv.org/abs/hep-th/9909001v3
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Sep 23, 2013
09/13
Sep 23, 2013
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Andrew G. Cohen; David B. Kaplan; Ann E. Nelson
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A massless up quark is an intriguing solution to the strong CP problem. We discuss how lattice computations can be used in conjunction with chiral perturbation theory to address the consistency of $m_u=0$ with the observed hadron spectrum and interactions. It is not necessary to simulate very light quarks-three flavor partially quenched computations with comparable sea and valence quark masses on the order of the strange quark mass could suffice.
Source: http://arxiv.org/abs/hep-lat/9909091v3
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Sep 22, 2013
09/13
Sep 22, 2013
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Rob Fardon; Ann E. Nelson; Neal Weiner
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We show that mass varying neutrinos (MaVaNs) can behave as a negative pressure fluid which could be the origin of the cosmic acceleration. We derive a model independent relation between the neutrino mass and the equation of state parameter of the neutrino dark energy, which is applicable for general theories of mass varying particles. The neutrino mass depends on the local neutrino density and the observed neutrino mass can exceed the cosmological bound on a constant neutrino mass. We discuss...
Source: http://arxiv.org/abs/astro-ph/0309800v2
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Sep 22, 2013
09/13
Sep 22, 2013
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Ann E. Nelson
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I discuss a ``more minimal'' modification of the minimal supersymmetric standard model, in which supersymmetry breaking is connected with the physics of flavor. Flavor Changing Neutral Currents (FCNC) for the first two families are suppressed, and for the third family may be of comparable size to the FCNC in the Standard Model.
Source: http://arxiv.org/abs/hep-ph/9704302v1
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Sep 22, 2013
09/13
Sep 22, 2013
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Baruch Feldman; Ann E. Nelson
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We show that inclusion of an extremely small quartic coupling constant in the potential for a nearly massless scalar field greatly increases the experimentally allowed region for the mass term and the coupling of the field to matter.
Source: http://arxiv.org/abs/hep-ph/0603057v2
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Sep 22, 2013
09/13
Sep 22, 2013
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Sandro Ambrosanio; Ann E. Nelson
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We discuss the phenomenology of a class of supersymmetric models in which some of the quark and lepton superfields are an integral part of a dynamical supersymmetry breaking sector. The corresponding squarks and sleptons are much heavier than any other superpartners, and could naturally have masses as high as ~ 40 TeV. We discuss a general set of conditions for acceptable flavor-changing neutral currents and natural electroweak symmetry breaking, and identify two particularly interesting new...
Source: http://arxiv.org/abs/hep-ph/9707242v1
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Sep 22, 2013
09/13
Sep 22, 2013
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Ann E. Nelson
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I review the motivation for dynamical supersymmetry breaking, the various mechanisms which have been discovered, and the prospects for model building.
Source: http://arxiv.org/abs/hep-ph/9707442v1
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Sep 22, 2013
09/13
Sep 22, 2013
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Z. Chacko; Patrick J. Fox; Ann E. Nelson; Neal Weiner
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Models with extra dimensions have changed our understanding of the hierarchy problem. In general, these models explain the weakness of gravity by diluting gravity in a large bulk volume, or by localizing the graviton away from the standard model. In this paper, we show that the warped geometries necessary for the latter scenario can naturally induce the large volumes necessary for the former. We present a model in which a large volume is stabilized without supersymmetry. We comment on the...
Source: http://arxiv.org/abs/hep-ph/0106343v2
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Sep 22, 2013
09/13
Sep 22, 2013
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Guy D. Moore; Ann E. Nelson
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Recently, interesting 4-D Lorentz violating models have been proposed, in which all particles have a common maximum velocity $c$, but gravity propagates (in the preferred frame) with a different maximum velocity $c_g \neq c$. We show that the case $c_g < c$ is very tightly constrained by the observation of the highest energy cosmic rays. Assuming a galactic origin for the cosmic rays gives a conservative bound of $c-c_g < 2 \times 10^{-15} c$; if the cosmic rays have an extragalactic...
Source: http://arxiv.org/abs/hep-ph/0106220v2
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Sep 22, 2013
09/13
Sep 22, 2013
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Ann E. Nelson
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Relatively simple models can be constructed in which supersymmetry is dynamically broken at energies of $10^5-10^7$ GeV. Models of this kind do not suffer from the naturalness and cosmological difficulties of conventional supergravity models, and make definite predictions for the spectrum of supersymmetric particle masses. Thus ``Renormalizable Visible Sector Models'' are a viable alternative to more conventional approaches. This talk mostly summarizes the results of a recent paper written with...
Source: http://arxiv.org/abs/hep-ph/9503345v1
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Sep 21, 2013
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Sep 21, 2013
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Ann E. Nelson; Takemichi Okui; Tuhin S. Roy
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We present a simple, perturbative, and renormalizable model with a flavor symmetry which can explain both the t-tbar forward-backward asymmetry and the bump feature present in the dijet mass distribution of the W+jj sample in the range 120-160 GeV that was recently reported by the CDF collaboration. The flavor symmetry not only ensures the flavor/CP safety of the model, but also relates the two anomalies unambiguously. It predicts a comparable forward-backward asymmetry in c-cbar. The...
Source: http://arxiv.org/abs/1104.2030v2
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Sep 21, 2013
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Sep 21, 2013
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Ann E. Nelson; Maurizio Piai; Christopher Spitzer
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We construct a model of an unparticle sector consisting of a supersymmetric SU(N) gauge theory with the number of flavors in the Seiberg conformal window. We couple this sector to the MSSM via heavy messengers. The resulting low energy theory has a Higgs coupling to unparticles. The Higgs vev drives the hidden Seiberg sector to a new conformal fixed point. The coupling to the Higgs mediates supersymmetry breaking to the Seiberg sector, and breaks conformal invariance at a lower scale. The low...
Source: http://arxiv.org/abs/0905.0503v2
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Sep 21, 2013
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Sep 21, 2013
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Ann E. Nelson; Matthew J. Strassler
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We explore the effects of a strongly-coupled, approximately scale-invariant sector on the renormalization of soft supersymmetry breaking terms. A useful formalism for deriving exact results for renormalization of soft supersymmetry breaking terms is given in an appendix, and used to generalize previously known results to include the effects of nontrilinear superpotential terms. We show that a class of theories which explain the flavor hierarchy without flavor symmetries can also solve the...
Source: http://arxiv.org/abs/hep-ph/0104051v2
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Sep 21, 2013
09/13
Sep 21, 2013
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Kiwoon Choi; David B. Kaplan; Ann E. Nelson
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We suggest here that CP is a discrete {\it gauge} symmetry, and is therefore not violated by quantum gravity. We show that four dimensional CP can arise as a discrete gauge symmetry in theories with dimensional compactification, if the original number of Minkowski dimensions equals $8k+1$, $8k+2$ or $8k+3$, and if there are certain restrictions on the gauge group; these conditions are met by superstrings. CP may then be broken spontaneously below $10^9$ GeV, explaining the observed CP violation...
Source: http://arxiv.org/abs/hep-ph/9205202v1
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Sep 20, 2013
09/13
Sep 20, 2013
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Netta Engelhardt; Ann E. Nelson; Jonathan R. Walsh
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We consider searching for light sterile fermions and new forces by using long baseline oscillations of neutrinos and antineutrinos. A new light sterile state and/or a new force can lead to apparent CPT violation in muon neutrino and antineutrino oscillations. As an example, we present an economical model of neutrino masses containing a sterile neutrino. The potential from the Standard Model neutral current gives rise to a difference between the disappearance probabilities of neutrinos and...
Source: http://arxiv.org/abs/1002.4452v3
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Sep 20, 2013
09/13
Sep 20, 2013
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Andrew G. Cohen; David B. Kaplan; Francois Lepeintre; Ann E. Nelson
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We discuss how to extract non-Standard Model effects from B-factory phenomenology. We then analyze the prospects for uncovering evidence for Effective Supersymmetry, a class of supersymmetric models which naturally suppress flavor changing neutral currents and electric dipole moments without squark universality or small CP violating phases, in experiments at BaBar, BELLE, HERA-B, CDF/D0 and LHC-B.
Source: http://arxiv.org/abs/hep-ph/9610252v3
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Sep 20, 2013
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Sep 20, 2013
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Tom Banks; David B. Kaplan; Ann E. Nelson
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We provide a taxonomy of dynamical supersymmetry breaking theories, and discuss the cosmological implications of the various types of models. Models in which supersymmetry breaking is produced by chiral superfields which only have interactions of gravitational strength (\eg\ string theory moduli) are inconsistent with standard big bang nucleosynthesis unless the gravitino mass is greater than $\CO(3) \times 10^4$ GeV. This problem cannot be solved by inflation. Models in which supersymmetry is...
Source: http://arxiv.org/abs/hep-ph/9308292v1
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Sep 20, 2013
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Sep 20, 2013
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Ann E. Nelson; Lisa Randall
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We show that if there are only two Higgs doublets in the supersymmetric standard model, large $\tan\beta$ requires a fine tuning in the parameters of the Lagrangian of order ($1/\tan\beta$), which cannot be explained by any approximate symmetry. With an extended Higgs sector, large $\tan\beta$ can be natural. We give an explicit example with four doublets in which it is possible to achieve large $\tan\beta$ as a result of an approximate symmetry, without any light superpartners. The approximate...
Source: http://arxiv.org/abs/hep-ph/9308277v1
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Sep 19, 2013
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Sep 19, 2013
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Ann E. Nelson
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I describe, from the bottom up, a sequence of natural effective field theories. Below a TeV we have the minimal standard model with a light Higgs, and an extra neutral scalar. In the 1-10 TeV region these scalars are part of a multiplet of pseudo Nambu-Goldstone Bosons. Interactions with additional TeV mass scalars, gauge bosons, and vector-like charge 2/3 quarks stabilize the Higgs mass squared parameter without finetuning. Electroweak superconductivity may be determined in this effective...
Source: http://arxiv.org/abs/hep-ph/0304036v1
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Sep 19, 2013
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Sep 19, 2013
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Rob Fardon; Ann E. Nelson; Neal Weiner
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We present a supersymmetric model of dark energy from Mass Varying Neutrinos which is stable against radiative corrections to masses and couplings, and free of dynamical instabilities. This is the only such model of dark energy involving fields with significant couplings to any standard model particle. We briefly discuss consequences for neutrino oscillations and solar neutrinos.
Source: http://arxiv.org/abs/hep-ph/0507235v2
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Sep 19, 2013
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Sep 19, 2013
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Ann E. Nelson; Nathan Seiberg
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We point out a connection between R symmetry and \susy\ breaking. We show that the existence of an R symmetry is a necessary condition for \susy\ breaking and a spontaneously broken R symmetry is a sufficient condition provided two conditions are satisfied. These conditions are: {\it genericity}, \ie\ the effective Lagrangian is a generic Lagrangian consistent with the symmetries of the theory (no fine tuning), and {\it calculability}, \ie\ the low energy theory can be described by a...
Source: http://arxiv.org/abs/hep-ph/9309299v1
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Sep 19, 2013
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Sep 19, 2013
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Z. Chacko; Markus A. Luty; Ann E. Nelson; Eduardo Ponton
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We consider supersymmetric theories where the standard-model quark and lepton fields are localized on a "3-brane" in extra dimensions, while the gauge and Higgs fields propagate in the bulk. If supersymmetry is broken on another 3-brane, supersymmetry breaking is communicated to gauge and Higgs fields by direct higher-dimension interactions, and to quark and lepton fields via standard-model loops. We show that this gives rise to a realistic and predictive model for supersymmetry...
Source: http://arxiv.org/abs/hep-ph/9911323v3
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Sep 19, 2013
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Sep 19, 2013
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Patrick J. Fox; Ann E. Nelson; Neal Weiner
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We introduce a new supersymmetric extension of the standard model in which the gauge sector contains complete N=2 supersymmetry multiplets. Supersymmetry breaking from the D-term vev of a hidden sector U(1) gauge field leads to Dirac soft supersymmetry breaking gaugino masses, and a new type of soft scalar trilinear couplings. The resulting squark and slepton masses are finite, calculable, positive and flavor universal. The Higgs soft mass squared is negative. The phenomenology of these...
Source: http://arxiv.org/abs/hep-ph/0206096v3
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Sep 19, 2013
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Sep 19, 2013
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Ann E. Nelson; Nuria Rius; Veronica Sanz; Mithat Unsal
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We propose a supersymmetric extension of the standard model which is a realistic alternative to the MSSM, and which has several advantages. No ``mu'' supersymmetric Higgs/Higgsino mass parameter is needed for sufficiently heavy charginos. An approximate U(1) R symmetry naturally guarantees that tan beta is large, explaining the top/bottom quark mass hierarchy. This symmetry also suppresses supersymmetric contributions to anomalous magnetic moments, b to s gamma, and proton decay, and these...
Source: http://arxiv.org/abs/hep-ph/0206102v3
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Sep 19, 2013
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Sep 19, 2013
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Ann E. Nelson
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The most severe constraints on quark-lepton four-fermion contact interactions come from the agreement of atomic parity violation measurements with the Standard Model. In this letter I note that for contact interactions which arise in theories of composite quarks and leptons, other approximate global symmetries than parity can eliminate the contribution of contact terms to atomic parity violation. The most stringent tests of compositeness therefore come from the high energy collider experiments...
Source: http://arxiv.org/abs/hep-ph/9703379v2
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Sep 19, 2013
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Sep 19, 2013
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Ann E Nelson
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Neutrinos may mix with ultralight fermions, which gives flavor oscillations, and with heavier fermions, which yields short distance flavor change. I consider the case where both effects are present. I show that in the limit where a single oscillation length is experimentally accessible, the effects of heavier fermions on neutrino oscillations can generically be accounted for by a simple formula containing four parameters, including observable CP violation. I consider the anomalous LSND and...
Source: http://arxiv.org/abs/1010.3970v1
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Sep 19, 2013
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Sep 19, 2013
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Michael Dine; Ann E. Nelson
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Conventional approaches to supersymmetric model building suffer from several naturalness problems: they do not explain the large hierarchy between the weak scale and the Planck mass, and they require fine tuning to avoid large flavor changing neutral currents and particle electric dipole moments. The existence of models with dynamical supersymmetry breaking, which can explain the hierarchy, has been known for some time, but efforts to build such models have suffered from unwanted axions and...
Source: http://arxiv.org/abs/hep-ph/9303230v2
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Sep 19, 2013
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Sep 19, 2013
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Patrick Huet; Ann E. Nelson
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The baryon density which may be produced during the electroweak phase transition in supersymmetric models is computed, taking into account the previously neglected effects of transport, strong and weak anomalous fermion number violation, thermal scattering, and a new method for computing \cp\ violating processes during the transition. We can account for the observed baryon asymmetry, provided new \cp-violating phases are greater than $\sim 10^{-(2-4)}$, and some superpartners are light enough...
Source: http://arxiv.org/abs/hep-ph/9506477v3
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Sep 18, 2013
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Sep 18, 2013
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David B. Kaplan; Ann E. Nelson
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In theories of axion dark matter with large axion decay constant, temperature variations in the CMB are extremely sensitive to perturbations in the initial axion field, allowing one to place a lower bound on the total amount of inflation. The most stringent bound comes from axion strings, which for axion decay constant f=10^17 GeV would currently be observable at a distance of 6 x 10^16 light-years, nearly ten million times as far away as our horizon.
Source: http://arxiv.org/abs/0809.1206v1
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Sep 18, 2013
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Sep 18, 2013
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Ann E. Nelson; Neal Weiner
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In the MSSM, an unfortunate prediction of minimal anomaly mediated supersymmetry breaking is that the slepton masses squared are negative. This problem is particularly intractable because of the insensitivity of anomaly mediation to ultraviolet physics. In this paper we note that tree level couplings to the conformal compensator in the Kahler potential give 10 TeV as a natural mass scale for physics beyond the MSSM, and, moreover, that the SUSY breaking effects from physics at this scale do not...
Source: http://arxiv.org/abs/hep-ph/0210288v2
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Sep 18, 2013
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Sep 18, 2013
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Andrew G. Cohen; David B. Kaplan; Ann E. Nelson
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Bekenstein has proposed the bound S < pi M_P^2 L^2 on the total entropy S in a volume L^3. This non-extensive scaling suggests that quantum field theory breaks down in large volume. To reconcile this breakdown with the success of local quantum field theory in describing observed particle phenomenology, we propose a relationship between UV and IR cutoffs such that an effective field theory should be a good description of Nature. We discuss implications for the cosmological constant problem....
Source: http://arxiv.org/abs/hep-th/9803132v2
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58
Sep 18, 2013
09/13
Sep 18, 2013
by
D. Elazzar Kaplan; Ann E. Nelson
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We discuss general predictions for neutrino masses and mixing angles from R parity violation in the Minimal Supersymmetric Standard Model. If the soft supersymmetry breaking terms are flavor blind at short distance, then the leptonic analogue of the CKM matrix depends on only two real parameters, which are completely determined by fits to solar and atmospheric neutrino oscillations. Either the small angle MSW, large angle MSW, or ``just-so'' solutions to the solar neutrino problem are allowed,...
Source: http://arxiv.org/abs/hep-ph/9901254v2
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50
Sep 18, 2013
09/13
Sep 18, 2013
by
Ann E. Nelson; Matthew J. Strassler
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We present a new mechanism, which does not require any flavor symmetry, to explain the small Yukawa couplings and CKM mixing angles. The Yukawa matrices are assumed to be random at short distances and the hierarchical structure is generated in the infrared by renormalization group flow. The generic qualitative predictions of this mechanism are in good agreement with observation. We give several simple examples in supersymmetric theories. We show that our mechanism can also ameliorate the...
Source: http://arxiv.org/abs/hep-ph/0006251v3
