arXiv subjects

Maxim Perelstein

Publications and source records attributed to Maxim Perelstein.

At least 91 records · Page 5Linked to original sources

arXiv2007

Testing Gluino Spin with Three-Body Decays

We examine the possibility of distinguishing a supersymmetric gluino from a Kaluza-Klein gluon of universal extra dimensions (UED) at the Large Hadron Collider (LHC). We focus on the case when all kinematically allowed tree-level decays of this particle are 3-body decays into two jets and a massive daughter (typically weak gaugino or Kaluza-Klein weak gauge boson). We show that the shapes of the dijet invariant mass distributions differ significantly in the two models, as long as the mass of the decaying particle mA is substantially larger than the mass of the massive daughter mB. We present a simple analysis estimating the number of events needed to distinguish between the two models under idealized conditions. For example, for mA/mB=10, we find the required number of events to be of order several thousand, which should be available at the LHC within a few years. This conclusion is confirmed by a parton level Monte Carlo study which includes the effects of experimental cuts and the combinatoric background.

hep-ph↗

arXiv2007

Little Higgs Models and T Parity

Little Higgs models are an interesting extension of the Standard Model at the TeV scale. They provide a simple and attractive mechanism of electroweak symmetry breaking. We review one of the simplest models of this class, the Littlest Higgs model, and its extension with T parity. The model with T parity satisfies precision electroweak constraints without fine-tuning, contains an attractive dark matter candidate, and leads to interesting phenomenology at the Large Hadron Collider (LHC).

hep-ph↗

arXiv2006

Indirect Detection of Little Higgs Dark Matter

Little Higgs models with T parity contain an attractive dark matter candidate, the heavy photon. We compute the cross section of the heavy photon annihilation into Z-photon pairs, which turns out to be substantially higher than the previously computed cross section for the two photon final state. Unfortunately, even with this enhancement, the monochromatic photon flux from galactic heavy photon annihilation is unlikely to be detectable by GLAST or the currently operating atmospheric Cerenkov telescopes. We also compute the flux of high-energy neutrinos from the annihilation of the heavy photons captured by the Sun and the Earth. The maximum flux of upward-going muons due to such neutrinos is about 1 yr^{-1}km^{-2}.

hep-ph↗

arXiv2006

Collider Signature of T-quarks

Little Higgs models with T Parity contain new vector-like fermions, the T-odd quarks or "T-quarks", which can be produced at hadron colliders with a QCD-strength cross section. Events with two acoplanar jets and large missing transverse energy provide a simple signature of T-quark production. We show that searches for this signature with the Tevatron Run II data can probe a significant part of the Little Higgs model parameter space not accessible to previous experiments, exploring T-quark masses up to about 400 GeV. This reach covers parts of the parameter space where the lightest T-odd particle can account for the observed dark matter relic abundance. We also comment on the prospects for this search at the Large Hadron Collider (LHC).

hep-ph↗

arXiv2006

Electroweak Precision Constraints on the Littlest Higgs Model with T Parity

We compute the leading corrections to the properties of W and Z bosons induced at the one-loop level in the SU(5)/SO(5) Littlest Higgs model with T parity, and perform a global fit to precision electroweak data to determine the constraints on the model parameters. We find that a large part of the model parameter space is consistent with data. Values of the symmetry breaking scale as low as 500 GeV are allowed, indicating that no significant fine tuning in the Higgs potential is required. We identify a region within the allowed parameter space in which the lightest T-odd particle, the partner of the hypercharge gauge boson, has the correct relic abundance to play the role of dark matter. In addition, we find that a consistent fit to data can be obtained for large values of the Higgs mass, up to 800 GeV, due to the possibility of a partial cancellation between the contributions to the T parameter from Higgs loops and new physics.

hep-ph↗

arXiv2005

Little Higgs Models and Their Phenomenology

This article reviews the Little Higgs models of electroweak symmetry breaking and their phenomenology. Little Higgs models incorporate a light composite Higgs boson and remain perturbative until a scale of order 10 TeV, as required by precision electroweak data. The collective symmetry breaking mechanism, which forms the basis of Little Higgs models, is introduced. An explicit, fully realistic implementation of this mechanism, the Littlest Higgs model, is then discussed in some detail. Several other implementations, including simple group models and models with T parity, are also reviewed. Precision electroweak constraints on a variety of Little Higgs models are summarized. If a Little Higgs model is realized in nature, the predicted new particles should be observable at the Large Hadron Collider (LHC). The expected signatures, as well as the experimental sensitivities and the possible strategies for confirming the Little Higgs origin of new particles, are discussed. Finally, several other related topics are briefly reviewed, including the ultraviolet completions of Little Higgs models, as well as the implications of these models for flavor physics and cosmology.

hep-ph↗

arXiv2005

Phenomenology of Higgsless Models at the LHC and the ILC

We investigate the signatures of the recently proposed Higgsless models at future colliders. We focus on tests of the mechanism of partial unitarity restoration in the longitudinal vector boson scattering, which do not depend on any Higgsless model-building details. We study the LHC discovery reach for charged massive vector boson resonances and show that all of the preferred parameter space will be probed with $100 {\rm fb}^{-1}$ of LHC data. We also discuss the prospects for experimental verification of the Higgsless nature of the model at the LHC. In addition, in this talk we present new results relevant for the discovery potential of Higgsless models at the International Linear Collider (ILC).

hep-ph↗

arXiv2005

Robust Gamma Ray Signature of WIMP Dark Matter

If dark matter consists of weakly interacting massive particles (WIMPs), annihilation of WIMPs in the galactic center may lead to an observable enhancement of high energy gamma ray fluxes. We predict the shape and normalization of the component of the flux due to final state radiation by charged particles produced in WIMP annihilation events. The prediction is made without any assumptions about the microscopic theory responsible for WIMPs, and depends only mildly on the unknown distribution of the total WIMP annihilation cross section among the possible final states. In particular, if the WIMPs annihilate into a pair of charged fermions (leptons or quarks), the photon spectrum possesses a sharp edge feature, dropping abruptly at a photon energy equal to the WIMP mass. If such a feature is observed, it would provide strong evidence for the WIMP-related nature of the flux enhancement, as well as a measurement of the WIMP mass. We discuss the prospects for observational discovery of this feature at ground-based and space-based gamma ray telescopes.

hep-ph↗

arXiv2005

Collider Phenomenology of the Higgsless Models

We identify and study the signatures of the recently proposed Higgsless models at the Large Hadron Collider (LHC). We concentrate on tests of the mechanism of partial unitarity restoration in the longitudinal vector boson scattering, which is crucial to the phenomenological success of any Higgsless model and does not depend on the model-building details. We investigate the discovery reach for charged massive vector boson resonances and show that all of the preferred parameter space will be probed with 100 inverse fb of LHC data. Unitarity restoration requires that the masses and couplings of the resonances obey certain sum rules. We discuss the prospects for their experimental verification at the LHC.

hep-ph↗

arXiv2004

Gauge-Assisted Technicolor?

It is well known that technicolor models in which the electroweak symmetry is broken by QCD-like strong dynamics at the TeV scale generally predict unacceptably large corrections to low-energy observables. We investigate the models of electroweak symmetry breaking by strong dynamics in which the gauge symmetry is extended to include an arbitrary number of additional SU(2) and U(1) factors. This class of models includes the deconstructed version of the recently proposed five-dimensional "Higgsless" scenario. We conclude that the additional structure present in these theories does not suppress the effects of strongly coupled short-distance physics on the precision electroweak observables. In particular, the possibility that the symmetry breaking is due to QCD-like dynamics is still strongly disfavored by data.

hep-ph↗

arXiv2004

Dark Matter at Colliders: a Model-Independent Approach

Assuming that cosmological dark matter consists of weakly interacting massive particles, we use the recent precise measurement of cosmological parameters to predict the guaranteed rates of production of such particles in association with photons at electron-positron colliders. Our approach is based on general physical principles such as detailed balancing and soft/collinear factorization. It leads to predictions that are valid across a broad range of models containing WIMPs, including supersymmetry, universal extra dimensions, and many others. We also discuss the discovery prospects for the predicted experimental signatures.

hep-ph↗

arXiv2004

Late Time Neutrino Masses, the LSND Experiment and the Cosmic Microwave Background

Models with low-scale breaking of global symmetries in the neutrino sector provide an alternative to the seesaw mechanism for understanding why neutrinos are light. Such models can easily incorporate light sterile neutrinos required by the LSND experiment. Furthermore, the constraints on the sterile neutrino properties from nucleosynthesis and large scale structure can be removed due to the non-conventional cosmological evolution of neutrino masses and densities. We present explicit, fully realistic supersymmetric models, and discuss the characteristic signatures predicted in the angular distributions of the cosmic microwave background.

hep-ph↗

arXiv2003

Collider Tests of the Little Higgs Model

The little Higgs model provides an alternative to traditional candidates for new physics at the TeV scale. The new heavy gauge bosons predicted by this model should be observable at the Large Hadron Collider (LHC). We discuss how the LHC experiments could test the little Higgs model by studying the production and decay of these particles.

hep-ph↗

arXiv2003

Top Quarks and Electroweak Symmetry Breaking in Little Higgs Models

`Little Higgs' models, in which the Higgs particle arises as a pseudo-Goldstone boson, have a natural mechanism of electroweak symmetry breaking associated with the large value of the top quark Yukawa coupling. The mechanism typically involves a new heavy SU(2)_{L} singlet top quark, T. We discuss the relationship of the Higgs boson and the two top quarks. We suggest experimental tests of the Little Higgs mechanism of electroweak symmetry breaking using the production and decay of the T at the Large Hadron Collider.

hep-ph↗

arXiv2003

Domain Walls as Dark Energy

The possibility that the energy density of the Universe is dominated by a network of low-tension domain walls provides an alternative to the commonly discussed cosmological constant and scalar-field quintessence models of dark energy. We quantify the lower bound on the number density of the domain walls that follows from the observed near-isotropy of the cosmic microwave background radiation. This bound can be satisfied by a strongly frustrated domain wall network. No fine-tuning of the parameters of the underlying field theory model is required. We briefly outline the observational consequences of this model.

astro-ph↗

arXiv2002

The Weak Mixing Angle From TeV Scale Quark-Lepton Unification

Unified theories based on an extended left-right symmetric group, $SU(4) \times SU(2)^4$, are constructed in five dimensions. The compactification scale is assumed to be only a loop factor above the weak scale, so that the weak mixing angle is predicted to be close to its tree level value of 0.239. Boundary conditions in the 5th dimension break $SU(4) \to SU(3) \times U(1)_{B-L}$, removing powerful constraints from $K_L \to μe$ while allowing a reliable calculation of the leading logarithm corrections to $\sin^2 θ$. The compactification scale is expected in the 1--5 TeV region, depending on how $SU(2)^4$ is broken. Two illustrative models are presented, and the experimental signal of the $Z'$ gauge boson is discussed.

hep-ph↗

arXiv2001

Exploring New Physics Through Contact Interactions in Lepton Pair Production at a Linear Collider

If a contact interaction type correction to a Standard Model process is observed, studying its detailed properties can provide information on the fundamental physics responsible for it. Assuming that such a correction has been observed in lepton pair production at a 500 GeV - 1 TeV linear collider, we consider a few possible models that could explain it, such as theories with large and TeV-scale extra dimensions and models with lepton compositeness. We show that using the measured cross-sections and angular distributions, these models can be distinguished with a high degree of confidence.

hep-ph↗

arXiv2001

Extra dimensions vs. supersymmetric interpretation of missing energy events at a linear collider

The photon plus missing energy signature is a primary handle on two important classes of theories. Theories with large extra dimensions predict the production of photons in association with Kaluza-Klein excitations of the graviton. In supersymmetric theories with superlight gravitinos, photons can be produced in association with gravitino pairs. The signatures for these two theories are compared, and it is found that they can be distinguished by studying the photon energy distributions and scaling of the cross section with center-of-mass energy. Both these methods fail, however, if there are six extra dimensions. In that case, additional phenomena predicted by the theories would be required to narrow down the underlying causes of the photon plus missing energy signal. We also study the ability of these measurements to determine the number of extra dimensions.

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