Search

We consider the effects of new light species on the Cosmic Microwave Background. In the massless limit, these effects can be parameterized in terms of a single number, the relativistic degrees of freedom. We perform a thorough survey of natural, minimal models containing new light species and numerically calculate the precise contribution of each of these models to this number in the framework of effective field theory. After reviewing the relevant details of early universe thermodynamics, we provide a map between the parameters of any particular theory and the predicted effective number of degrees of freedom. We then use this map to interpret the recent results from the Cosmic Microwave Background survey done by the Planck satellite. Using this data, we present new constraints on the parameter space of several models containing new light species. Future measurements of the Cosmic Microwave Background can be used with this map to further constrain the parameter space of all such models., Comment: 38 pages plus appendices and references; 10 figures and 1 table; references added, discussion of anapole moments added; supernovae cooling bounds added, discussion of models condensed

The current measurement of the Higgs mass, the ubiquitous nature of loop-suppressed gaugino masses in gravity-mediated supersymmetry breaking, relic dark matter density from $\sim$ TeV mass gauginos, together with the success of supersymmetric gauge coupling unification, suggest that scalar superpartner masses are roughly $m_{sc} \sim$ 100-1000 TeV. Higgsino masses, if not at the Planck scale, should generically appear at the same scale. The gaugino mass contributions from anomaly mediation, with the heavy Higgsino threshold, generally leads to a more compressed spectrum than standard anomaly mediation, while the presence of extra vector-like matter near $m_{sc}$ typically leads to an even more compressed spectrum. Heavy Higgsinos improve gauge coupling unification relative to the MSSM. Heavy scalars suggest new possibilities for flavor physics -- large flavor violations in the soft masses are now allowed, yielding interesting levels for new FCNC's, and re-opening the attractive possibility of a radiatively generated fermion mass hierarchy. Gluinos and binos/winos must decay through higher dimension operators, giving a unique handle on the presence of new physics the scale $m_{sc}$. Gluino decays should be spectacular, for example yielding events with four tops -- at modestly displaced vertices -- and two Higgses plus missing energy. The high scale $m_{sc}$ can also be probed in flavor-violating gluino decays, as well as a specific pattern of gluino branching ratios to the third generation. Finally, with heavy Higgsinos, the dominant decay for neutral winos and binos proceeds via the Higgs $\tilde b \to \tilde w h$. The heaviness of the Higgsinos can be inferred from the branching ratio for the rare decay $\tilde b \to \tilde w Z$.

Most generic models of hidden sector supersymmetry breaking do not feature singlets, and gauginos obtain masses from anomaly mediated supersymmetry breaking. If one desires a natural model, then the dominant contribution to scalar masses should be of the same order, i.e. also from AMSB. However, pure AMSB models suffer from the tachyonic slepton problem. Moreover, there is a large splitting between the gluino and the wino LSP masses resulting in tight exclusion limits from typical superpartner searches. We introduce messenger fields into this framework to obtain a hybrid theory of gauge and anomaly mediation, solving both problems simultaneously. Specifically, we find any number of vector-like messenger fields (allowed by GUT unification) compress the predicted gaugino spectrum when their masses come from the Giudice-Masiero mechanism. This more compressed spectrum is less constrained by LHC searches and allows for lighter gluinos. In addition to the model, we present gaugino pole mass equations that differ from (and correct) the original literature.

We argue that evidence can be uncovered for stops between 300-600 GeV in 5 fb^-1 of 7 TeV proton-proton collisions if they decay into top quarks and light neutral particles. We also show that with 20 fb^-1 of 8 TeV running, discovery or exclusion can be made in large regions of parameter space. Events with a fully hadronic top/anti-top pair and a pair of invisible decay products can be identified with the top-tagging of a fat jet, a single b-tag, a missing transverse energy cut, as well as other kinematic cuts to reduce backgrounds with real top quarks in them. Such cuts obliterate the background suggesting discovery can be made with a handful of events., Comment: 8 pages, 7 figures

The apparent absence of light superpartners at the LHC strongly constrains the viability of the MSSM as a solution to the hierarchy problem. These constraints can be significantly alleviated by R-parity violation (RPV). Bilinear R-parity violation, with the single operator L H_u, does not require any special flavor structure and can be naturally embedded in a GUT while avoiding constraints from proton decay (unlike baryon-number-violating RPV). The LSP in this scenario can be naturally long-lived, giving rise to displaced vertices. Many collider searches, particularly those selecting b-jets or leptons, are insensitive to events with such detector-scale displaced decays owing to cuts on track quality and impact parameter. We demonstrate that for decay lengths in the window ~1-1000 mm, constraints on superpartner masses can be as low as ~450 GeV for squarks and ~40 GeV for LSPs. In some parts of parameter space light LSPs can dominate the Higgs decay width, hiding the Higgs from existing searches. This framework motivates collider searches for detector-scale displaced vertices. LHCb may be ideally suited to trigger on such events, while ATLAS and CMS may need to trigger on missing energy in the event., Comment: 35 pages, 4 figures

Dark matter with mass below about a GeV is essentially unobservable in conventional direct detection experiments. However, newly proposed technology will allow the detection of single electron events in semiconductor materials with significantly lowered thresholds. This would allow detection of dark matter as light as an MeV in mass. Compared to other detection technologies, semiconductors allow enhanced sensitivity because of their low ionization energy around an eV. Such detectors would be particularly sensitive to dark matter with electric and magnetic dipole moments, with a reach many orders of magnitude beyond current bounds. Observable dipole moment interactions can be generated by new particles with masses as great as 1000 TeV, providing a window to scales beyond the reach of current colliders., Comment: 26 pages, 6 figures, references added, error in mass contribution corrected, discussion of constraints expanded and clarified, plot of mass range sensitivity expanded

We present a simple UV completion of Atomic Dark Matter (aDM) in which heavy right-handed neutrinos decay to induce both dark and lepton number densities. This model addresses several outstanding cosmological problems: the matter/anti-matter asymmetry, the dark matter abundance, the number of light degrees of freedom in the early universe, and the smoothing of small-scale structure. Additionally, this realization of aDM may reconcile the CoGeNT excess with recently published null results and predicts a signal in the CRESST Oxygen band. We also find that, due to unscreened long-range interactions, the residual un recombined dark ions settle into a diffuse isothermal halo., Comment: 17 pages, 3 figures, expanded discussion of light degrees of freedom, minor typos corrected, to appear in JCAP

We discuss the feasibility of seeing a Higgs boson which decays to four partons through a pair of (pseudo-)scalars at the LHC. We restrict our search to Higgs bosons produced in association with a W/Z boson at high transverse momentum. We argue that subjet analysis techniques are a good discriminant between such events and W/Z plus jets and top-antitop production. For light scalar masses (below 30 GeV), we find evidence that a flavor-independent search for such a non-standard Higgs boson is plausible with 100 fb^-1 of data, while a Higgs decaying to heavier scalars is only likely to be visible in models where scalar decays to b quarks dominate., Comment: 6 pages, 4 figures

Particles with TeV mass and strong self-interactions generically have the right annihilation cross section to explain an observed excess of cosmic electrons and positrons if the end-product of the annihilation is charged leptons. We present an explicit model of strongly-coupled TeV-scale dark matter whose relic abundance related to the matter-antimatter asymmetry of the observed universe. The B - L asymmetry of the standard model is transfered to the dark sector by an operator carrying standard model lepton number. Lepton number violation naturally induces dark matter particle-antiparticle oscillations at late times, allowing dark matter-antimatter annihilations today. The dark matter annihilates into lighter strongly-interacting particles in the dark sector that decay to leptons via the transfer operator. The strong dynamics in the dark sector is at the weak scale due to supersymmetry breaking. The correct dark matter abundance is automatically obtained for natural values of dimensionless parameters, analogous to the situation for conventional WIMPs., Comment: 4 pages, revtex, 1 figure; v2: corrected discussion of relic density, bounds on dark matter Majorana mass

We discuss the feasibility of seeing a Higgs boson which decays to four bottom quarks through a pair of (pseudo-)scalars at the LHCb experiment to argue that the use of b-physics triggers and off-line vertex reconstruction, as opposed to jet triggers with b tagging, may be more effective for this signal. Focusing on inclusive production for the Higgs, we find that for light scalar masses below 20 GeV, signal reconstruction efficiencies of order a few percent may be enough for LHCb to find evidence for a Higgs with a dominant 4b decay channel., Comment: 6 pages, 2 figures

We propose that dark matter is dominantly comprised of atomic bound states. We build a simple model and map the parameter space that results in the early universe formation of hydrogen-like dark atoms. We find that atomic dark matter has interesting implications for cosmology as well as direct detection: Protohalo formation can be suppressed below $M_{proto} \sim 10^3 - 10^6 M_{\odot}$ for weak scale dark matter due to Ion-Radiation interactions in the dark sector. Moreover, weak-scale dark atoms can accommodate hyperfine splittings of order $100 \kev$, consistent with the inelastic dark matter interpretation of the DAMA data while naturally evading direct detection bounds., Comment: 17 pages, 3 figures

A method is introduced for distinguishing top jets (boosted, hadronically decaying top quarks) from light quark and gluon jets using jet substructure. The procedure involves parsing the jet cluster to resolve its subjets, and then imposing kinematic constraints. With this method, light quark or gluon jets with pT ~ 1 TeV can be rejected with an efficiency of around 99% while retaining up to 40% of top jets. This reduces the dijet background to heavy t-tbar resonances by a factor of ~10,000, thereby allowing resonance searches in t-tbar to be extended into the all-hadronic channel. In addition, top-tagging can be used in t-tbar events when one of the tops decays semi-leptonically, in events with missing energy, and in studies of b-tagging efficiency at high pT., Comment: 4 pages, 4 figures; v2: separate quark and gluon efficiencies included, figure on helicity angle added, and physics discussion extended

Using recently developed techniques for computing event shapes with Soft-Collinear Effective Theory, LEP event shape data is used to derive strong model-independent bounds on new colored particles. In the effective field theory computation, colored particles contribute in loops not only to the running of alpha_s but also to the running of hard, jet and soft functions. Moreover, the differential distribution in the effective theory explicitly probes many energy scales, so event shapes have strong sensitivity to new particle thresholds. Using thrust data from ALEPH and OPAL, colored adjoint fermions (such as a gluino) below 51.0 GeV are ruled out to 95% confidence level. This is nearly an order-of-magnitude improvement over the previous model-independent bound of 6.3 GeV., Comment: 4 pages, 2 figures

In supersymmetric models with R parity violation, constraints on superpartner masses are significantly weaker than in models which conserve R parity. We find in regions of parameter space where a neutral gaugino or third generation scalar is decoupled from the Z and/or traditional gaugino mass relationships do not hold allow some particles to be light enough to allow them to be the decay products of the Higgs. For example, surprisingly a stau could be lighter than 30 GeV if it decays hadronically. We estimate the Higgs bounds when one of these decays dominates and find allowed Higgs masses well below the current LEP bound on the standard model Higgs. We also survey the rich variety of final states in Higgs production., Comment: 27 pages 9 figures

The spectrum of supersymmetric theories with R-parity violation are much more weakly constrained than that of supersymmetric theories with a stable neutralino. We investigate the signatures of supersymmetry at the LHCb experiment in the region of parameter space where the neutralino decay leaves a displaced vertex. We find sensitivity to squark production up to squark masses of order 1 TeV. We note that if the Higgs decays to neutralinos in this scenario, LHCb should see the lightest Higgs boson before ATLAS and CMS., Comment: 7 pages, 5 figures

Both electroweak precision measurements and simple supersymmetric extensions of the standard model prefer a mass of the Higgs boson less than the experimental lower limit of 114 GeV. We show that supersymmetric models with R parity violation and baryon number violation have a significant range of parameter space in which the Higgs dominantly decays to six jets. These decays are much more weakly constrained by current LEP analyses and would allow for a Higgs mass near that of the $Z$. In general, lighter scalar quark and other superpartner masses are allowed and the fine-tuning typically required to generate the measured scale of electroweak symmetry breaking is ameliorated. The Higgs would potentially be discovered at hadron colliders via the appearance of new displaced vertices. The lightest neutralino could be discovered by a scan of vertex-less events LEP I data., Comment: 5 pages, 2 figures. Significant detail added to the arguments regarding LEP limits - made more quantitative. Better figures used, plotting more physical quantities. Typos corrected and references updated. Conclusions unchanged

We study a symmetry, schematically Energy -> - Energy, which suppresses matter contributions to the cosmological constant. The requisite negative energy fluctuations are identified with a "ghost" copy of the Standard Model. Gravity explicitly, but weakly, violates the symmetry, and naturalness requires General Relativity to break down at short distances with testable consequences. If this breakdown is accompanied by gravitational Lorentz-violation, the decay of flat spacetime by ghost production is acceptably slow. We show that inflation works in our scenario and can lead to the initial conditions required for standard Big Bang cosmology., Comment: 18 pages, 3 figures, References corrected

We introduce a new model of supersymmetry breaking dominated by anomaly mediation. It has a viable spectrum, successful electroweak symmetry breaking, solves the mu-problem and maintains the anomaly-mediated form for soft-masses down to low energies thus solving the flavor problem. The model consists of the minimal supersymmetric standard model plus a singlet, anomaly-mediated soft masses and a dirac mass which marries the bino to the singlet. We describe a large class of models in the UV which can produce such boundary conditions. The dirac mass does not affect the so-called "UV insensitivity" of the other soft parameters to running or supersymmetric thresholds and thus flavor physics at intermediate scales would not reintroduce the flavor problem. The dirac bino is integrated out at a few TeV and produces {\it finite and positive} contributions to all hyper-charged scalars at one loop thus producing positive squared slepton masses. The theory predicts some CP violation in the Higgs sector leading to a correlation between the spectra to be seen at the LHC and electric dipole moments within experimental reach in the near future., Comment: 20 pages, 1 figure

The little Higgs mechanism produces a light 100 GeV Higgs while raising the natural cutoff from 1 TeV to 10 TeV. We attempt an iterative little Higgs mechanism to produce multiple factors of 10 between the cutoff and the 100 GeV Higgs mass in a perturbative theory. In the renormalizable sector of the theory, all quantum corrections to the Higgs mass proportional to mass scales greater than 1 TeV are absent -- this includes quadratically divergent, log-divergent, and finite loops at all orders. However, even loops proportional to scales just a factor of 10 above the Higgs (or any other scalar) mass come with large numerical factors that reintroduce fine-tuning. Top loops, for example, produce an expansion parameter of not 1/(4 pi) but 1/5. The geometric increase in the number of fields at higher energies simply exacerbates this problem. We build a complete two-stage model up to 100 TeV, show that direct sensitivity of the electroweak scale to the cutoff is erased, and estimate the tuning due to large numerical factors. We then discuss the possibility, in a toy model with only scalar and gauge fields, of generating a tower of little Higgs theories and show that the theory quickly becomes a large-N gauge theory with ~ N fundamental scalars. We find evidence that at least this toy model could successfully generate light scalars with an exponentially large cutoff in the absence of supersymmetry or strong dynamics. The fine-tuning is not completely eliminated, but evidence suggests that this result is model dependent. We then speculate as to how one might marry a working tower of fields of this type at high scales to a realistic theory at the weak scale., Comment: 26 (+1) pages, 9 figures

We present an ultra-violet extension of the "simplest little Higgs" model. The model marries the simplest little Higgs at low energies to two copies of the "littlest Higgs'' at higher energies. The result is a weakly coupled theory below 100 TeV with a naturally light Higgs. The higher cutoff suppresses the contributions of strongly coupled dynamics to dangerous operators such as those which induce flavor changing neutral currents and CP violation. We briefly survey the distinctive phenomenology of the model., Comment: 19 pages, clarifications and references added

The LEP-II bound on the light Higgs mass rules out the vast majority of parameter space left to the Minimal Supersymmetric Standard Model (MSSM) with weak-scale soft-masses. This suggests the importance of exploring extensions of the MSSM with non-minimal Higgs physics. In this article, we explore a theory with an additional singlet superfield and an extended gauge sector. The theory has a number of novel features compared to both the MSSM and Next-to-MSSM, including easily realizing a light CP-even Higgs mass consistent with LEP-II limits, tan(beta) < 1, and a lightest Higgs which is charged. These features are achieved while remaining consistent with perturbative unification and without large stop-masses. Discovery modes at the Tevatron and LHC are discussed., Comment: 15 pages, 5 figures; Typo in equation (4.5) corrected; submitted to JHEP

The minimal supersymmetric standard model, and extensions, have stringent upper bounds on the mass of the lightest Higgs boson if perturbativity up to the Planck scale is assumed. We argue that these bounds are softened tremendously if the Higgs is charged under an asymptotically free gauge group. We present a model with an additional SU(2) gauge group which easily produces Higgs masses above 200 GeV while avoiding electroweak constraints. If one allows some fine-tuning of the high-scale value of the gauge coupling, Higgs masses greater than 350 GeV are achieved. Unification of couplings is predicted to similar accuracy as in the minimal supersymmetric standard model with only small deviations at the two-loop level., Comment: 10 pages, JHEP3, clarifications added in sections 2 and conclusions, version to be published in JHEP

We present a model of electroweak symmetry breaking in which the Higgs boson is a pseudo-Nambu-Goldstone boson. By embedding the standard model SU(2) x U(1) into an SU(4) x U(1) gauge group, one-loop quadratic divergences to the Higgs mass from gauge and top loops are canceled automatically with the minimal particle content. The potential contains a Higgs quartic coupling which does not introduce one-loop quadratic divergences. Our theory is weakly coupled at the electroweak scale, it has new weakly coupled particles at the TeV scale and a cutoff above 10 TeV, all without fine tuning. We discuss the spectrum of the model and estimate the constraints from electroweak precision measurements., Comment: 29 pages, referencing error corrected after death threats, dude removed

Cosmological inflation gives a natural answer for a variety of cosmological questions, including the horizon problem, the flatness problem, and others. However, inflation yields new questions relating to the flatness of the inflaton potential. Recent studies of ``little'' fields, a special class of pseudo-Goldstone bosons, have shown it is possible to protect the mass of a field while still yielding order one interactions with other fields. In this paper, we will show that ``little inflatons'' are natural candidates for the slow roll field of hybrid inflation models. We consider both supersymmetric and non-supersymmetric models, and give a simple examples based on approximate Abelian symmetries which solve the inflaton flatness problem of supergravity. We also present hybrid models in which components of gauge fields in higher dimensions play the role of the inflaton. Protected by higher-dimensional gauge symmetry, they, too, naturally have large couplings while suppressed mass terms. We summarize the implications of the new WMAP data on such models., Comment: 25 pages; corrections, references added, discussion modified including consideration of WMAP results

We apply a recently proposed mechanism for predicting the weak mixing angle to theories with TeV-size dimensions. "Reconstruction" of the associated moose (or quiver) leads to theories which unify the electroweak forces into a five dimensional SU(3) symmetry. Quarks live at an orbifold fixed point where SU(3) breaks to the electroweak group. A variety of theories -- all sharing the same successful prediction of the weak mixing angle -- emerges; they differ primarily by the spatial location of the leptons and the absence or presence of supersymmetry. A particularly interesting theory puts leptons in a Konopinski-Mahmoud triplet and suppresses proton decay by placing quarks and leptons on opposite fixed points., Comment: 8 pages, 3 figures, LaTeX

We present models in which the observed fermion masses and mixings are generated by dynamically localizing the three generations of matter in a flat compact extra dimension. We first construct models assuming the hierarchy problem is addressed by the existence of large extra dimensions, i.e. the fundamental scale is not far above a TeV and supersymmetry is not imposed. These models are compactified, chiral, and don't require fine-tuning to generate the top mass. Limits on the compactification scale based on flavor-changing neutral currents are relaxed compared to those on existing models. We then supersymmetrize some of these models. Using N=1 superspace language in extra dimensions, we find space-dependent flat directions which can be used to localize fields. Finally, we discuss methods of breaking supersymmetry and the impact of these models on the superpartner spectrum., Comment: Latex using JHEP style; 28 pages

It is known that one can add D-term contributions for U(1)_Y and U(1)_{B-L} to the anomaly-mediated supersymmetry breaking to make the superparticle spectrum phenomenologically viable. We point out that this can be done without spoiling its important virtue, namely the ultraviolet insensitivity. This framework can be derived from supersymmetry breaking and U(1)_{B-L} breaking on hidden brane(s)., Comment: 19 pages, Latex, small clarifications added