arXiv subjects

Hock-Seng Goh

Publications and source records attributed to Hock-Seng Goh.

14 recordsLinked to original sources

arXiv2015

The Twin Higgs: Natural Electroweak Breaking from Mirror Symmetry

We present `twin Higgs models', simple realizations of the Higgs as a pseudo-Goldstone boson that protect the weak scale from radiative corrections up to scales of order 5 - 10 TeV. In the ultra-violet these theories have a discrete symmetry which interchanges each Standard Model particle with a corresponding particle which transforms under a twin or mirror Standard Model gauge group. In addition, the Higgs sector respects an approximate global SU(4) symmetry. When this global symmetry is broken, the discrete symmetry tightly constrains the form of corrections to the pseudo-Goldstone Higgs potential, allowing natural electroweak symmetry breaking. Precision electroweak constraints are satisfied by construction. These models demonstrate that, contrary to the conventional wisdom, stabilizing the weak scale does not require new light particles charged under the Standard Model gauge groups.

hep-ph↗

arXiv2010

Lepton Number Violating Signals of the Top Partners in the Left-Right Twin Higgs Model

We study the collider signatures of the left-right twin Higgs model in the case that the right-handed neutrino mass is less than the mass of the right-handed gauge boson. In this scenario, new leptonic decay chains open up, allowing the particles which cancel the one-loop quadratic divergences of the Higgs, the right-handed gauge bosons and top-partners, to be discovered. Half of these events contain same-sign leptons without missing energy, which have no genuine standard model background and for which the backgrounds are purely instrumental. These signals may be used to complement other collider searches, and in certain regions of parameter space, may be the only way to observe the particles responsible for natural electroweak symmetry breaking in the left-right twin Higgs model.

hep-ph↗

arXiv2009

Environmentally Selected WIMP Dark Matter with High-Scale Supersymmetry Breaking

We explore the possibility that both the weak scale and the thermal relic dark matter abundance are environmentally selected in a multiverse. An underlying supersymmetric theory containing the states of the MSSM and singlets, with supersymmetry and R symmetry broken at unified scales, has just two realistic low energy effective theories. One theory, (SM + \tilde{w}), is the Standard Model augmented only by the wino, having a mass near 3 TeV, and has a Higgs boson mass in the range of (127 - 142) GeV. The other theory, (SM + \tilde{h}/\tilde{s}), has Higgsinos and a singlino added to the Standard Model. The Higgs boson mass depends on the single new Yukawa coupling of the theory, y, and is near 141 GeV for small y but grows to be as large as 210 GeV as this new coupling approaches strong coupling at high energies. Much of the parameter space of this theory will be probed by direct detection searches for dark matter that push two orders of magnitude below the present bounds; furthermore, the dark matter mass and cross section on nucleons are correlated with the Higgs boson mass. The indirect detection signal of monochromatic photons from the galactic center is computed, and the range of parameters that may be accessible to LHC searches for trilepton events is explored. Taking a broader view, allowing the possibility of R symmetry protection to the TeV scale or axion dark matter, we find four more theories: (SM + axion), two versions of Split Supersymmetry, and the E-MSSM, where a little supersymmetric hierarchy is predicted. The special Higgs mass value of (141 \pm 2) GeV appears in symmetry limits of three of the six theories, (SM + axion), (SM + \tilde{w}) and (SM + \tilde{h}/\tilde{s}), motivating a comparison of other signals of these three theories.

hep-ph↗

arXiv2009

R-axion detection at LHC

Supersymmetric models with spontaneously broken approximate R-symmetry contain a light spin 0 particle, the R-axion. The properties of the particle can be a powerful probe of the structure of the new physics. In this paper, we discuss the possibilities of the R-axion detection at the LHC experiments. It is challenge to observe this light particle in the LHC environment. However, for typical values in which the mass of the R-axion is a few hundred MeV, we show that those particles can be detected by searching for displaced vertices from R-axion decay.

hep-ph↗

arXiv2009

The Leptonic Higgs as a Messenger of Dark Matter

We propose that the leptonic cosmic ray signals seen by PAMELA and ATIC result from the annihilation or decay of dark matter particles via states of a leptonic Higgs doublet to $τ$ leptons, linking cosmic ray signals of dark matter to LHC signals of the Higgs sector. The states of the leptonic Higgs doublet are lighter than about 200 GeV, yielding large $\barτ τ$ and $\barτ τ\barτ τ$ event rates at the LHC. Simple models are given for the dark matter particle and its interactions with the leptonic Higgs, for cosmic ray signals arising from both annihilations and decays in the galactic halo. For the case of annihilations, cosmic photon and neutrino signals are on the verge of discovery.

hep-ph↗

arXiv2008

The Quirky Collider Signals of Folded Supersymmetry

We investigate the collider signals associated with scalar quirks ("squirks") in folded supersymmetric models. As opposed to regular superpartners in supersymmetric models these particles are uncolored, but are instead charged under a new confining group, leading to radically different collider signals. Due to the new strong dynamics, squirks that are pair produced do not hadronize separately, but rather form a highly excited bound state. The excited ``squirkonium'' loses energy to radiation before annihilating back into Standard Model particles. We calculate the branching fractions into various channels for this process, which is prompt on collider time-scales. The most promising annihilation channel for discovery is W+photon which dominates for squirkonium near its ground state. We demonstrate the feasibility of the LHC search, showing that the mass peak is visible above the SM continuum background and estimate the discovery reach.

hep-ph↗

arXiv2007

A Little Twin Higgs Model

We present a twin Higgs model based on left-right symmetry with a tree level quartic. This is made possible by extending the symmetry of the model to include two Z_2 parities, each of which is sufficient to protect the Higgs from getting a quadratically divergent mass squared. Although both parities are broken explicitly, the symmetries that protect the Higgs from getting a quadratically divergent mass are broken only collectively. The quadratic divergences of the Higgs mass are thus still protected at one loop. We find that the fine tuning in this model is reduced substantially compared to the original left-right twin Higgs model. This mechanism can also be applied to the mirror twin Higgs model to get a significant reduction of the fine tuning, while keeping the mirror photon massless.

hep-ph↗

arXiv2007

Phenomenology of The Left-Right Twin Higgs Model

The twin Higgs mechanism has recently been proposed to solve the little hierarchy problem. We study the implementation of the twin Higgs mechanism in left-right models. At TeV scale, heavy quark and gauge bosons appear, with rich collider phenomenology. In addition, there are extra Higgses, some of which couple to both the Standard Model fermion sector and the gauge sector, while others couple to the gauge bosons only. We present the particle spectrum, and study the general features of the collider phenomenology of this class of model at the Large Hadron Collider.

hep-ph↗

arXiv2006

Folded Supersymmetry and the LEP Paradox

We present a new class of models that stabilize the weak scale against radiative corrections up to scales of order 5 TeV without large corrections to precision electroweak observables. In these `folded supersymmetric' theories the one loop quadratic divergences of the Standard Model Higgs field are cancelled by opposite spin partners, but the gauge quantum numbers of these new particles are in general different from those of the conventional superpartners. This class of models is built around the correspondence that exists in the large N limit between the correlation functions of supersymmetric theories and those of their non-supersymmetric orbifold daughters. By identifying the mechanism which underlies the cancellation of one loop quadratic divergences in these theories, we are able to construct simple extensions of the Standard Model which are radiatively stable at one loop. Ultraviolet completions of these theories can be obtained by imposing suitable boundary conditions on an appropriate supersymmetric higher dimensional theory compactified down to four dimensions. We construct a specific model based on these ideas which stabilizes the weak scale up to about 20 TeV and where the states which cancel the top loop are scalars not charged under Standard Model color. Its collider signatures are distinct from conventional supersymmetric theories and include characteristic events with hard leptons and missing energy.

hep-ph↗

arXiv2006

Phenomenology of Left-Right Twin Higgs Model

Twin Higgs mechanism has recently been proposed to solve the ``little Hierarchy'' problem. We studied the implementation of twin Higgs mechanism in left-right models. We discussed the particle spectrum, and the collider phenomenology at the Large Hadron Collider.

hep-ph↗

arXiv2005

Gauge Mediation from Emergent Supersymmetry

We explore the possibility of gauge mediation in a paradigm whereby supersymmetry is posited to be an accidental symmetry of Nature and the Standard Model fields are composite bound states that emerge from a conformal field theory. The resultant effective theory can, through sequestering and conformal dynamics, exhibit most of the properties of low energy supersymmetry breaking while averting a number of cosmological and astrophysical constraints of the traditional framework of gauge mediation via dynamical supersymmetry breaking. Of particular phenomenological interest is that in our scenario, the gravitino is superheavy, the neutralino LSP is a viable candidate for cold dark matter and the flavor changing neutral currents are constrained to be, at the very minimum, only an order of magnitude below current experimental bounds.

hep-ph↗

arXiv2005

A Twin Higgs Model from Left-Right Symmetry

We present twin Higgs models based on the extension of the Standard Model to left-right symmetry that protect the weak scale against radiative corrections up to scales of order 5 TeV. In the ultra-violet the Higgs sector of these theories respects an approximate global symmetry, in addition to the discrete parity symmetry characteristic of left-right symmetric models. The Standard Model Higgs field emerges as the pseudo-Goldstone boson associated with the breaking of the global symmetry. The parity symmetry tightly constrains the form of radiative corrections to the Higgs potential, allowing natural electroweak breaking. The minimal model predicts a rich spectrum of exotic particles that will be accessible to upcoming experiments, and which are necessary for the cancellation of one-loop quadratic divergences. These include right-handed gauge bosons with masses not to exceed a few TeV and a pair of vector-like quarks with masses of order several hundred GeV.

hep-ph↗

arXiv2003

Supersymmetry without Supersymmetry

We investigate the possibility that supersymmetry is not a fundamental symmetry of nature, but emerges as an accidental approximate global symmetry at low energies. This can occur if the visible sector is non-supersymmetric at high scales, but flows toward a strongly-coupled superconformal fixed point at low energies; or, alternatively, if the visible sector is localized near the infrared brane of a warped higher-dimensional spacetime with supersymmetry broken only on the UV brane. These two scenarios are related by the AdS/CFT correspondence. In order for supersymmetry to solve the hierarchy problem, the conformal symmetry must be broken below 10^{11} GeV. Accelerated unification can naturally explain the observed gauge coupling unification by physics below the conformal breaking scale. In this framework, there is no gravitino and no reason for the existence of gravitational moduli, thus eliminating the cosmological problems associated with these particles. No special dynamics is required to break supersymmetry; rather, supersymmetry is broken at observable energies because the fixed point is never reached. In 4D language, this can be due to irrelevant supersymmetry breaking operators with approximately equal dimensions. In 5D language, the size of the extra dimension is stabilized by massive bulk fields. No small input parameters are required to generate a large hierarchy. Supersymmetry can be broken in the visible sector either through direct mediation or by the F term of the modulus associated with the breaking of conformal invariance.

hep-th↗

arXiv2003

Supergravity loop contributions to brane world supersymmetry breaking

We compute the supergravity loop contributions to the visible sector scalar masses in the simplest 5D `brane-world' model. Supersymmetry is assumed to be broken away from the visible brane and the contributions are UV finite due to 5D locality. We perform the calculation with N = 1 supergraphs, using a formulation of 5D supergravity in terms of N = 1 superfields. We compute contributions to the 4D effective action that determine the visible scalar masses, and we find that the mass-squared terms are negative.

hep-th↗