arXiv subjects
Publications and source records attributed to Seong Chan Park.
Recently a weak X-ray emission around E ~ 3.5 keV was detected in the Andromeda galaxy and various galaxy clusters including the Perseus galaxy cluster but its source has been unidentified. Axino, the superpartner of axion, with a mass 2E is suggested as a possible origin of the line with R-parity violating decay into photon and neutrino. Moreover, most of parameter space is consistent with recent observation by the BICEP2 experiment.
The observed value of the Higgs mass indicates that the Higgs potential becomes small and flat at the scale around $10^{17}$GeV. Having this fact in mind, we reconsider the Higgs inflation scenario proposed by Bezrukov and Shaposhnikov. It turns out that the non-minimal coupling $ξ$ of the Higgs-squared to the Ricci scalar can be smaller than ten. For example, $ξ=7$ corresponds to the tensor-to-scalar ratio $r\simeq0.2$, which is consistent with the recent observation by BICEP2.
Discovery of a Higgs boson and precise measurements of its properties open a new window to test physics beyond the standard model. Models with Universal Extra Dimensions are not exception. Kaluza-Klein excitations of the standard model particles contribute to the production and decay of the Higgs boson. In particular, the parameters associated with third generation quarks are constrained by Higgs data, which are relatively insensitive to other searches often involving light quarks and leptons. We investigate implications of the 126 GeV Higgs in Next-to-Minimal Universal Extra Dimensions, and show that boundary terms and bulk masses allow a lower compactification scale as compared to in Minimal Universal Extra Dimensions.
As the electromagnetic gauge symmetry makes the electron stable, a new abelian gauge symmetry may be responsible for the stability of superheavy dark matter. The gauge boson associated with the new gauge symmetry naturally plays the role of dark radiation and contributes to the effective number of `neutrino species', which has been recently measured by Planck. We estimate the contribution of dark radiation from the radiative decay of a scalar particle induced by the WIMPZILLA in the loop. The scalar particle may affect the invisible decay of the Higgs boson by the Higgs portal type coupling.
We present a general model with universal extra dimensions in the presence of the bulk fermion masses and boundary localized kinetic terms, which are generically allowed by symmetries of five dimensional gauge theory. We provide a comprehensive analysis for a general UED model, including Kaluza-Klein mass spectra, their interactions with the SM particles, and constraints from LHC, electroweak tests, and dark matter experiments. Finally we show current bounds on the size of allowed universal bulk mass and universal brane-localized terms.
We study the signature of dilepton and a hard jet ($\ell^+\ell^-j$) via heavy new gauge boson production in split universal extra dimension scenario where the Kaluza-Klein parity is conserved but the Kaluza-Klein number is not. A hard cut to the jet energy effectively removes virtually all possible backgrounds and provides a handle to search of new physics involving new neutral heavy states as the Kaluza-Klein $Z$ boson. The signature can be more generically used in search of other new states such as graviton and radion in warped extra dimension models.
In light of the recent observation of the Fermi-LAT 130 GeV gamma-ray line, we suggest a model of scalar dark matter in hidden sector, which can decay into two (hidden) photons. The process is radiatively induced by a GUT scale fermion in the loop, which is charged under a hidden sector U(1), and the kinetic mixing ($\sim εF^{μν}F'_{μν}$) enables us to fit the required decay width for the Fermi-LAT peak. The model does not allow any dangerous decay channels into light standard model particles.
The recent discovery of a new boson of mass roughly 125 GeV has been reported by the ATLAS and CMS collaborations. Although its signals in various decay modes resemble those of the standard model (SM) Higgs boson, observed are the combinations of entangled information about the production, decay rates and total decay width of the new boson. In addition, some decay channels show non-negligible deviation from the SM expectation, such as the $2σ$ excess in the diphoton channel. In the four types (I, II, X and Y) of two Higgs doublet models, we perform the global $χ^2$ fit in three scenarios: (i) the new boson is the light CP-even Higgs boson $h^0$; (ii) it is the heavy CP-even Higgs boson $H^0$; (iii) the signals are from degenerate $h^0$ and the pseudoscalar $A^0$. Considering other phenomenological constraints such as flavor physics, electroweak precision data, and the LEP search for the Higgs boson, we find that the the first scenarios in Type II and Type Y models actually provide better or similarly good fit to the data than the SM. All the other models are excluded at 95% C.L..
In models with extra dimensions, vectorlike Dirac masses for fermion fields are generically allowed. These masses are independent of electroweak symmetry breaking and do not contribute to the known masses for the quarks and leptons. They control the profile of the bulk wave functions, the mass spectra of Kaluza-Klein modes, and interactions that could be tested in experiments. In this article, we study the effects of bulk masses in electroweak precision measurements and in dark matter and collider searches, to set bounds on the bulk mass parameters in models with a flat universal extra dimension, namely, Split-UED. We find the current bound on the universal bulk-mass to be smaller than (0.2-0.3)/R, where R is the radius of the extra dimension. Similar but slightly relaxed bounds are obtained in the non-universal bulk mass case. The LHC is expected to play an important role in constraining the remaining parameter space.
In low-scale gravity models, a particle collider with trans-Planckian collision energies can be an ideal place for producing black holes because a large amount of energy can be concentrated at the collision point, which can ultimately lead to black hole formation. In this article, the theoretical foundation for microscopic higher dimensional black holes is reviewed and the possible production and detection at the LHC is described and critically examined.
Physics in curved spacetime describes a multitude of phenomena, ranging from astrophysics to high energy physics. The last few years have witnessed further progress on several fronts, including the accurate numerical evolution of the gravitational field equations, which now allows highly nonlinear phenomena to be tamed. Numerical relativity simulations, originally developed to understand strong field astrophysical processes, could prove extremely useful to understand high-energy physics processes like trans-Planckian scattering and gauge-gravity dualities. We present a concise and comprehensive overview of the state-of-the-art and important open problems in the field(s), along with guidelines for the next years. This writeup is a summary of the "NR/HEP Workshop" held in Madeira, Portugal from August 31st to September 3rd 2011.
We study the new heavy charged gauge boson W' in various models including Left-Right symmetric, Little Higgs, Randall-Sundrum and universal extra dimension model considering pp \rightarrow W' \rightarrow lepton + neutrino with the 7 TeV and 14 TeV CM energies at the LHC. Of particular, we show that the universal extra dimension model is highly constrained by existing and forthcoming data.
Recently the CMS collaboration at the LHC reported "the first direct limit on black hole production at a particle accelerator" using a data sample corresponding to an integrated luminosity of 35/pb of pp-collision at a center of mass energy of 7 TeV. Even though the result has a strong impact on future searches, the interpretation lacks enough theoretical support. In this letter, we show that the parameter range which was considered by the CMS collaboration is actually out of the validity range of semi-classical black hole picture so that the Monte-Carlo simulation result which was crucially used in the analysis still needs further solid scientific basis.
We study a mechanism where tiny neutrino masses arise only from radiative contribution in a supersymmetric model. In each generation, the tree-level light neutrino mass is rotated away by introducing a second SM singlet $s_{L}$ that forms a Dirac mass term with the right-handed neutrino $n_{R}$. Even with non-zero Majorana neutrino mass for the right-handed neutrinos $M_{R} \bar{n^{c}_{R}} n_{R}$, the lightest neutrino remains massless at tree level due to an approximate symmetry as $U(1)_{ν-s}$. Holomorphic feature of superpotential ensures that the Majorana neutrino masses $M_{R} \bar{n^{c}_{R}} n_{R}$ and $M^{*}_{R} \bar{s^{c}_{L}} s_{L}$ are not generated simultaneously. However, the $U(1)_{ν-s}$ is not respected by the SM gauge interactions or interaction with Higgs. Consequently, tiny neutrino masses arise from radiative contributions. It is also shown that the right-handed neutrino Majorana mass $M_{R}$ can be at $\cal O$(KeV) to obtain the proper light neutrino mass.
We propose a natural scenario for the cosmological inflation with the non-minimal coupling term invoking compact hyperbolic extra dimensions. Thanks to the unique mathematical properties of compact hyperbolic space, the large volume of extra dimensions, which provides a natural understanding of the proper size of couplings, does not necessarily accompany with the low Kaluza-Klein scale so that the model allows a single field inflation with a scale around $10^{13}$ GeV. The model fulfills all the observed data and predicts a sizable gravitational perturbation, r~0.003.
We consider CPT violation in neutrino sector, which is induced by ghost condensation. A model with extra dimension is suggested where ghost condensation occurs at a distant location separated from the SM brane. Right handed neutrinos in the bulk, which are originally introduced to explain small Yukawa couplings, play the role of messenger fields communicating ghost condensation and the standard model sector and lead to a sizable CPT violation in neutrino sector at the leading order. The model provides a resolution to the recent MINOS anomaly without spoiling any experimental constraints and may be able to be tested by observing an interesting phenomenon, twinkling cosmic microwave background radiation, with timescale about O(10-100) minutes at future CMB observations e.g. Planck.
We propose a gauged $U(1)_{H}$ horizontal symmetry around TeV scale that is a subgroup of a $SU(3)_{H}$ horizontal gauge symmetry broken at ${\cal O}(10^{14}) \GeV$. The breaking generates right-handed Majorana neutrino masses through a $SU(3)_H$ sextet scalar. A particular Majorana right-handed neutrino mass matrix explicitly determines the remnant $U(1)_{H}$ at low energy which only couples to $b-s$ and $μ-τ$ in the gauge eigenstate. The dangerous $K-\bar{K}$, $D-\bar{D}$ mixing and $B_s \rightarrow μ^+ μ^-$ are kept to be safe because the relevant couplings are suppressed through high powers of small mixing angles in the fermion rotation matrix. Our analysis which applies to the general case shows that the Tevatron di-muon anomaly can be explained through the $B_{s}$ and $B_{d}$ mixing while keeping all the other experimental constraints within 90 \% C. L. For the $B$ meson decay, the $B_{s}\to μ^{\pm}τ^{\mp}$ is the leading leptonic decay channel which is several orders of magnitude below current experimental bound.
We study M-theory solutions involving compact hyperbolic spaces. The combination of a gap `a la Randall-Sundrum and the topology of an internal Riemann surface allows a geometrical solution to the hierarchy problem that does not require light Kaluza--Klein modes. We comment on the consequences of such a compactification for LHC physics.