Higgs friends and counterfeits at hadron colliders

We consider the possibility of "Higgs counterfeits" - scalars that can be produced with cross sections comparable to the SM Higgs, and which decay with identical relative observable branching ratios, but which are nonetheless not responsible for electroweak symmetry breaking. We also consider a related scenario involving "Higgs friends," fields similarly produced through gg fusion processes, which would be discovered through diboson channels WW, ZZ, gamma gamma, or even gamma Z, potentially with larger cross sections times branching ratios than for the Higgs. The discovery of either a Higgs friend or a Higgs counterfeit, rather than directly pointing towards the origin of the weak scale, would indicate the presence of new colored fields necessary for the sizable production cross section (and possibly new colorless but electroweakly charged states as well, in the case of the diboson decays of a Higgs friend). These particles could easily be confused for an ordinary Higgs, perhaps with an additional generation to explain the different cross section, and we emphasize the importance of vector boson fusion as a channel to distinguish a Higgs counterfeit from a true Higgs. Such fields would naturally be expected in scenarios with "effective Z's," where heavy states charged under the SM produce effective charges for SM fields under a new gauge force. We discuss the prospects for discovery of Higgs counterfeits, Higgs friends, and associated charged fields at the LHC.Comment: 27 pages, 5 figures. References added and typos fixe

Phenomenology and Cosmology of an Electroweak Pseudo-Dilaton and Electroweak Baryons

In many strongly-interacting models of electroweak symmetry breaking the lowest-lying observable particle is a pseudo-Goldstone boson of approximate scale symmetry, the pseudo-dilaton. Its interactions with Standard Model particles can be described using a low-energy effective nonlinear chiral Lagrangian supplemented by terms that restore approximate scale symmetry, yielding couplings of the pseudo-dilaton that differ from those of a Standard Model Higgs boson by fixed factors. We review the experimental constraints on such a pseudo-dilaton in light of new data from the LHC and elsewhere. The effective nonlinear chiral Lagrangian has Skyrmion solutions that may be identified with the `electroweak baryons' of the underlying strongly-interacting theory, whose nature may be revealed by the properties of the Skyrmions. We discuss the finite-temperature electroweak phase transition in the low-energy effective theory, finding that the possibility of a first-order electroweak phase transition is resurrected. We discuss the evolution of the Universe during this transition and derive an order-of-magnitude lower limit on the abundance of electroweak baryons in the absence of a cosmological asymmetry, which suggests that such an asymmetry would be necessary if the electroweak baryons are to provide the cosmological density of dark matter. We revisit estimates of the corresponding spin-independent dark matter scattering cross section, with a view to direct detection experiments.Comment: 34 pages, 4 figures, additional references adde

Distinguishing Various Models of the 125 GeV Boson in Vector Boson Fusion

The hint of a new particle around 125 GeV at the LHC through the decay modes of diphoton and a number of others may point to quite a number of possibilities. While at the LHC the dominant production mechanism for the Higgs boson of the standard model and some other extensions is via the gluon fusion process, the alternative vector boson fusion is more sensitive to electroweak symmetry breaking through the gauge-Higgs couplings and therefore can be used to probe for models beyond the standard model. In this work, using the well known dijet-tagging technique to single out the vector boson fusion mechanism, we investigate its capability to discriminate a number of models that have been suggested to give an enhanced inclusive diphoton production rate, including the standard model Higgs boson, fermiophobic Higgs boson, Randall-Sundrum radion, inert-Higgs-doublet model, two-Higgs-doublet model, and the MSSM. The rates in vector-boson fusion can give more information of the underlying models to help distinguishing among the models.Comment: 31 pages, 3 figures; in this version some wordings are change

Holographic metastability

We show how supersymmetric QCD in a slice of AdS can naturally acquire metastable vacua. The formulation closely follows that of Intriligator, Seiberg and Shih (ISS), with an "electric" sector on the UV brane and a "magnetic" sector on the IR brane. However the 't Hooft anomaly matching that constrains the Seiberg duality central to ISS is replaced by anomaly inflow and cancellation, and the source of strong coupling is the CFT to which the theory couples rather than the gauge groups. The theory contains an anomaly free R-symmetry that, when broken by UV effects, leads to an O'Raifeartaigh model on the IR brane. In contrast to ISS, the R-symmetry breaking in the UV can be maximal, and yet the R-symmetry breaking in the IR theory remains under strict control: there is no need for retrofitting of small parameters.Comment: 20 pages, 2 figure

Revealing the electroweak properties of a new scalar resonance

One or more new heavy resonances may be discovered in experiments at the CERN Large Hadron Collider. In order to determine if such a resonance is the long-awaited Higgs boson, it is essential to pin down its spin, CP, and electroweak quantum numbers. Here we describe how to determine what role a newly-discovered neutral CP-even scalar plays in electroweak symmetry breaking, by measuring its relative decay rates into pairs of electroweak vector bosons: WW, ZZ, \gamma\gamma, and Z\gamma. With the data-driven assumption that electroweak symmetry breaking respects a remnant custodial symmetry, we perform a general analysis with operators up to dimension five. Remarkably, only three pure cases and one nontrivial mixed case need to be disambiguated, which can always be done if all four decay modes to electroweak vector bosons can be observed or constrained. We exhibit interesting special cases of Higgs look-alikes with nonstandard decay patterns, including a very suppressed branching to WW or very enhanced branchings to \gamma\gamma and Z\gamma. Even if two vector boson branching fractions conform to Standard Model expectations for a Higgs doublet, measurements of the other two decay modes could unmask a Higgs imposter.Comment: 23 pages, two figures; v2: minor revision and version to appear in JHE

Higgs After the Discovery: A Status Report

Recently, the ATLAS and CMS collaborations have announced the discovery of a 125 GeV particle, commensurable with the Higgs boson. We analyze the 2011 and 2012 LHC and Tevatron Higgs data in the context of simplified new physics models, paying close attention to models which can enhance the diphoton rate and allow for a natural weak-scale theory. Combining the available LHC and Tevatron data in the ZZ* 4-lepton, WW* 2-lepton, diphoton, and b-bbar channels, we derive constraints on the effective low-energy theory of the Higgs boson. We map several simplified scenarios to the effective theory, capturing numerous new physics models such as supersymmetry, composite Higgs, dilaton. We further study models with extended Higgs sectors which can naturally enhance the diphoton rate. We find that the current Higgs data are consistent with the Standard Model Higgs boson and, consequently, the parameter space in all models which go beyond the Standard Model is highly constrained.Comment: 37 pages; v2: ATLAS dijet-tag diphoton channel added, dilaton and doublet-singlet bugs corrected, references added; v3: ATLAS WW channel included, comments and references adde

Lorentz Violation in Warped Extra Dimensions

Higher dimensional theories which address some of the problematic issues of the Standard Model(SM) naturally involve some form of $D=4+n$-dimensional Lorentz invariance violation (LIV). In such models the fundamental physics which leads to, e.g., field localization, orbifolding, the existence of brane terms and the compactification process all can introduce LIV in the higher dimensional theory while still preserving 4-d Lorentz invariance. In this paper, attempting to capture some of this physics, we extend our previous analysis of LIV in 5-d UED-type models to those with 5-d warped extra dimensions. To be specific, we employ the 5-d analog of the SM Extension of Kostelecky et. al. ~which incorporates a complete set of operators arising from spontaneous LIV. We show that while the response of the bulk scalar, fermion and gauge fields to the addition of LIV operators in warped models is qualitatively similar to what happens in the flat 5-d UED case, the gravity sector of these models reacts very differently than in flat space. Specifically, we show that LIV in this warped case leads to a non-zero bulk mass for the 5-d graviton and so the would-be zero mode, which we identify as the usual 4-d graviton, must necessarily become massive. The origin of this mass term is the simultaneous existence of the constant non-zero $AdS_5$ curvature and the loss of general co-ordinate invariance via LIV in the 5-d theory. Thus warped 5-d models with LIV in the gravity sector are not phenomenologically viable.Comment: 14 pages, 4 figs; discussion added, algebra repaire

What traits are carried on mobile genetic elements, and why?

Although similar to any other organism, prokaryotes can transfer genes vertically from mother cell to daughter cell, they can also exchange certain genes horizontally. Genes can move within and between genomes at fast rates because of mobile genetic elements (MGEs). Although mobile elements are fundamentally self-interested entities, and thus replicate for their own gain, they frequently carry genes beneficial for their hosts and/or the neighbours of their hosts. Many genes that are carried by mobile elements code for traits that are expressed outside of the cell. Such traits are involved in bacterial sociality, such as the production of public goods, which benefit a cell's neighbours, or the production of bacteriocins, which harm a cell's neighbours. In this study we review the patterns that are emerging in the types of genes carried by mobile elements, and discuss the evolutionary and ecological conditions under which mobile elements evolve to carry their peculiar mix of parasitic, beneficial and cooperative genes

Composite Higgs Sketch

The coupling of a composite Higgs to the standard model fields can deviate substantially from the standard model values. In this case perturbative unitarity might break down before the scale of compositeness is reached, which would suggest that additional composites should lie well below this scale. In this paper we account for the presence of an additional spin 1 custodial triplet of rhos. We examine the implications of requiring perturbative unitarity up to the compositeness scale and find that one has to be close to saturating certain unitarity sum rules involving the Higgs and the rho couplings. Given these restrictions on the parameter space we investigate the main phenomenological consequences of the spin 1 triplet. We find that they can substantially enhance the Higgs di-photon rate at the LHC even with a reduced Higgs coupling to gauge bosons. The main existing LHC bounds arise from di-boson searches, especially in the experimentally clean channel where the charged rhos decay to a W-boson and a Z, which then decay leptonically. We find that a large range of interesting parameter space with 700 GeV < m(rho) < 2 TeV is currently experimentally viable.Comment: 37 pages, 12 figures; v4: sum rule corrected, conclusions unchange

Supersymmetry with Light Stops

Recent LHC data, together with the electroweak naturalness argument, suggest that the top squarks may be significantly lighter than the other sfermions. We present supersymmetric models in which such a split spectrum is obtained through "geometries": being "close to" electroweak symmetry breaking implies being "away from" supersymmetry breaking, and vice versa. In particular, we present models in 5D warped spacetime, in which supersymmetry breaking and Higgs fields are located on the ultraviolet and infrared branes, respectively, and the top multiplets are localized to the infrared brane. The hierarchy of the Yukawa matrices can be obtained while keeping near flavor degeneracy between the first two generation sfermions, avoiding stringent constraints from flavor and CP violation. Through the AdS/CFT correspondence, the models can be interpreted as purely 4D theories in which the top and Higgs multiplets are composites of some strongly interacting sector exhibiting nontrivial dynamics at a low energy. Because of the compositeness of the Higgs and top multiplets, Landau pole constraints for the Higgs and top couplings apply only up to the dynamical scale, allowing for a relatively heavy Higgs boson, including m_h = 125 GeV as suggested by the recent LHC data. We analyze electroweak symmetry breaking for a well-motivated subset of these models, and find that fine-tuning in electroweak symmetry breaking is indeed ameliorated. We also discuss a flat space realization of the scenario in which supersymmetry is broken by boundary conditions, with the top multiplets localized to a brane while other matter multiplets delocalized in the bulk.Comment: 27 pages, 7 figure