arXiv subjects

Hong-Jian He

Publications and source records attributed to Hong-Jian He.

At least 73 records · Page 4Linked to original sources

arXiv2013

Natural Electroweak Symmetry Breaking from Scale Invariant Higgs Mechanism

We construct a minimal viable extension of the standard model (SM) with classical scale symmetry. Its scalar sector contains a complex singlet in addition to the SM Higgs doublet. The scale-invariant and CP-symmetric Higgs potential generates radiative electroweak symmetry breaking a la Coleman-Weinberg, and gives a natural solution to the hierarchy problem, free from fine-tuning. Besides the 125GeV SM-like Higgs particle, it predicts a new CP-even Higgs (serving as the pseudo-Nambu-Goldstone boson of scale symmetry breaking) and a CP-odd scalar singlet (providing the dark matter candidate) at weak scale. We systematically analyze experimental constraints from direct LHC Higgs searches and electroweak precision tests, as well as theoretical bounds from unitarity, triviality and vacuum stability. We demonstrate the viable parameter space, and discuss implications for new Higgs and dark matter (DM) searches at the upcoming LHC runs and for the on-going direct detections of DM.

hep-ph↗

arXiv2013

LHC Higgs Signatures from Topflavor Seesaw Mechanism

We study LHC Higgs signatures from topflavor seesaw realization of electroweak symmetry breaking with a minimal gauge extension SU(2) x SU(2) x U(1). This elegant renormalizable construction singles out top quark sector (instead of all other light fermions) to join the new SU(2) gauge force. It predicts extra vector-like spectator quarks (T, B), new gauge bosons (W', Z'), and a pair of neutral Higgs bosons (h, H). We demonstrate that for the lighter Higgs boson h of mass 125GeV, this model predicts modified Higgs signal rates in h --> γγ, WW*, ZZ* channels via gluon fusions, in h --> tau tau mode via vector boson fusions, and in h --> bb mode via gauge boson associate productions. We perform a global fit for our theory by including both direct search data (LHC and Tevatron) and indirect precision constraints. We further analyze the LHC discovery potential for detecting the heavier Higgs state H.

hep-ph↗

arXiv2013

Probing LHC Higgs Signals from Extended Electroweak Gauge Group

We study the effects of the extended electroweak gauge sector on the signal strengths of the Higgs boson at the LHC. Extension of the Higgs sector associate with the extension of the electroweak gauge symmetry. In our setup, there are two neutral Higgs states ($h$, $H$) and three new gauge bosons ($W'^{\pm}$, $Z'$). We assume the lightest scalar, $h$, is what LHC found and its mass is 125 GeV. We find the enhancement of $μ(gg \to h \to γγ)$. On the other hand, other decay processes are same as or smaller than the SM expectation.

hep-ph↗

arXiv2013

Unitary Standard Model from Spontaneous Dimensional Reduction and Weak Boson Scattering at the LHC

Spontaneous dimensional reduction (SDR) is a striking phenomenon predicted by a number of quantum gravity approaches which all indicate that the spacetime dimensions get reduced at high energies. In this work, we formulate an effective theory of electroweak interactions based upon the standard model, incorporating the spontaneous reduction of space-dimensions at TeV scale. The electroweak gauge symmetry is nonlinearly realized with or without a Higgs boson. We demonstrate that the SDR ensures good high energy behavior and predicts unitary weak boson scattering. For a light Higgs boson of mass 125GeV, the TeV-scale SDR gives a natural solution to the hierarchy problem. Such a light Higgs boson can have induced anomalous gauge couplings from the TeV-scale SDR. We find that the corresponding WW scattering cross sections become unitary at TeV scale, but exhibit different behaviors from that of the 4d standard model. These can be discriminated by the WW scattering experiments at the LHC.

hep-ph↗

arXiv2013

Vector Bosons Signals of Electroweak Symmetry Breaking

We study the physics potential of the 8 TeV LHC to discover signals of extended gauge models or extra dimensional models whose low energy behavior is well represented by an SU(2) x SU(2) x U(1) electroweak gauge structure. We find that with a combined integrated luminosity of 40 fb^(-1), the first new Kaluza-Klein mode of the W gauge boson can be discovered up to a mass of about 400 GeV, when produced in association with a Z boson.

hep-ph↗

arXiv2013

Introduction of the CDEX experiment

Weakly Interacting Massive Particles (WIMPs) are the candidates of dark matter in our universe. Up to now any direct interaction of WIMP with nuclei has not been observed yet. The exclusion limits of the spin-independent cross section of WIMP-nucleon which have been experimentally obtained is about 10^{-7}pb at high mass region and only 10^{-5}pb} at low mass region. China Jin-Ping underground laboratory CJPL is the deepest underground lab in the world and provides a very promising environment for direct observation of dark matter. The China Dark Matter Experiment (CDEX) experiment is going to directly detect the WIMP flux with high sensitivity in the low mass region. Both CJPL and CDEX have achieved a remarkable progress in recent two years. The CDEX employs a point-contact germanium semi-conductor detector PCGe whose detection threshold is less than 300 eV. We report the measurement results of Muon flux, monitoring of radioactivity and Radon concentration carried out in CJPL, as well describe the structure and performance of the 1 kg PCGe detector CDEX-1 and 10kg detector array CDEX-10 including the detectors, electronics, shielding and cooling systems. Finally we discuss the physics goals of the CDEX-1, CDEX-10 and the future CDEX-1T detectors.

physics.ins-det↗

arXiv2013

Spontaneous Spacetime Reduction and Unitary Weak Boson Scattering at the LHC

Theories of quantum gravity predict spacetime dimensions to become reduced at high energies, a striking phenomenon known as spontaneous dimensional reduction (SDR). We construct an effective electroweak theory based on the standard model (SM) and incorporate the TeV-scale SDR, which exhibits good high energy behavior and ensures the unitarity of weak gauge boson scattering. This also provides a natural solution to the hierarchy problem in the presence of scalar Higgs boson. We demonstrate that this model predicts unitary longitudinal weak boson scattering, and can be discriminated from the conventional 4d SM by the WW scattering experiments at the CERN LHC.

hep-ph↗

arXiv2012

LHC Higgs Signatures from Extended Electroweak Gauge Symmetry

We study LHC Higgs signatures from the extended electroweak gauge symmetry SU(2) x SU(2) x U(1). Under this gauge structure, we present an effective UV completion of the 3-site moose model with ideal fermion delocalization, which contains two neutral Higgs states (h, H) and three new gauge bosons (W', Z'). We study the unitarity, and reveal that the exact E^2 cancellation in the longitudinal WW scattering amplitudes is achieved by the joint role of exchanging both spin-1 new gauge bosons and spin-0 Higgs bosons. We identify the lighter Higgs state h with mass 125GeV, and derive the unitarity bound on the mass of heavier Higgs boson H. The parameter space of this model is highly predictive. We study the production and decay signals of this 125GeV Higgs boson h at the LHC. We demonstrate that the h Higgs boson can naturally have enhanced signals in the diphoton channel $gg \to h \toγγ$, while the events rates in the reactions $gg \to h \to WW^*$ and $gg \to h \to ZZ^*$ are generally suppressed relative to the SM expectation. Searching the h Higgs boson via associated productions and vector boson fusions are also discussed for our model. We further analyze the LHC signals of the heavier Higgs boson H as a distinctive new physics discriminator from the SM. For wide mass-ranges of H, we derive constraints from the existing LHC searches, and study the discovery potential of H at the LHC(8TeV) and LHC(14TeV).

hep-ph↗

arXiv2012

Octahedral Symmetry with Geometrical Breaking: New Prediction for Neutrino Mixing Angle theta_{13} and CP Violation

We propose octahedral group O_h as the family symmetry of neutrino-lepton sector. We find that O_h contains subgroups Z_2(mu-tau) x Z_2(solar) and Z_4^l for realizing the bimaximal (BM) mixings, theta_{23} = theta_{12} = 45^o and theta_{13}=0^o, where Z_2(mu-tau) x Z_2(solar) and Z_4^l serve as the residual symmetries of neutrinos and charged leptons, respectively. We present geometric interpretations of BM mixing in the octahedron, and construct natural geometrical breaking of Z_4^l, leading to nontrivial deviations from the BM mixings. Our theory makes truly simple predictions of a relatively large reactor angle, theta_{13} = 45^o - theta_{12} = 7.5^o - 13.7^o (3 sigma), the nearly maximal atmospheric angle and the approximate maximal Dirac CP violation. These agree well with the current neutrino data, and will be further probed by the on-going and upcoming oscillation experiments.

hep-ph↗

arXiv2012

Discovering New Gauge Bosons of Electroweak Symmetry Breaking at LHC-8

We study the physics potential of the 8TeV LHC (LHC-8) to discover, during its 2012 run, a large class of extended gauge models or extra dimensional models whose low energy behavior is well represented by an SU(2)^2 x U(1) gauge structure. We analyze this class of models and find that with a combined integrated luminosity of 40-60/fb at the LHC-8, the first new Kaluza-Klein mode of the W gauge boson can be discovered up to a mass of about 370-400 GeV, when produced in association with a Z boson.

hep-ph↗

arXiv2012

Common Origin of mu-tau and CP Breaking in Neutrino Seesaw, Baryon Asymmetry, and Hidden Flavor Symmetry

We conjecture that all CP violations (both Dirac and Majorana types) arise from a common origin in neutrino seesaw. With this conceptually attractive and simple conjecture, we deduce that mu-tau breaking shares the common origin with all CP violations. We study the common origin of mu-tau and CP breaking in the Dirac mass matrix of seesaw Lagrangian (with right-handed neutrinos being mu-tau blind), which uniquely leads to inverted mass-ordering of light neutrinos. We then predict a very different correlation between the two small mu-tau breaking observables theta_{13}-0 and theta_{23}-45, which can saturate the present experimental upper limit on theta_{13}. This will be tested against our previous normal mass-ordering scheme by the on-going oscillation experiments. We also analyze the correlations of theta_{13} with Jarlskog invariant and neutrinoless double-beta-decay observable. From the common origin of CP and mu-tau breaking in the neutrino seesaw, we establish a direct link between the low energy CP violations and the cosmological CP violation for baryon asymmetry. With these we further predict a lower bound on theta_{13}, supporting the on-going probes of theta_{13} at Daya Bay, Double Chooz and RENO experiments. Finally, we analyze the general model-independent Z_2 x Z_2 symmetry structure of the light neutrino sector, and map it into the seesaw sector, where one of the Z_2's corresponds to the mu-tau symmetry and another the hidden symmetry Z_2^s (revealed in our previous work) which dictates the solar mixing angle θ_{12}. We derive the physical consequences of this Z_2^s and its possible partial violation in the presence of mu-tau breaking (without or with neutrino seesaw), regarding the theta_{12} determination and the correlation between mu-tau breaking observables.

hep-ph↗

arXiv2012

LHC Signatures of Two-Higgs-Doublets with Fourth Family

On-going Higgs searches in the light mass window are of vital importance for testing the Higgs mechanism and probing new physics beyond the standard model (SM). The latest ATLAS and CMS searches for the SM Higgs boson at the LHC (7TeV) found some intriguing excesses of events in the γγ/VV^* channels (V=Z,W) around the mass-range of 124-126 GeV. We explore a possible explanation of the γγand VV^* signals from the light CP-odd Higgs A^0 or CP-even Higgs h^0 from the general two-Higgs-doublet model with fourth-family fermions. We demonstrate that by including invisible decays of the Higgs boson A^0 or h^0 to fourth-family neutrinos, the predicted γγand VV^* signals can explain the observed new signatures at the LHC, and will be further probed by the forthcoming LHC runs in 2012.

hep-ph↗

arXiv2012

Spontaneous Mirror Parity Violation, Common Origin of Matter and Dark Matter, and the LHC Signatures

Existence of a mirror world in the universe is a fundamental way to restore the observed parity violation in weak interactions and provides the lightest mirror nucleon as a unique GeV-scale dark matter particle candidate. The visible and mirror worlds share the same spacetime of the universe and are connected by a unique space-inversion symmetry -- the mirror parity (P). We conjecture that the mirror parity is respected by the fundamental interaction Lagrangian, and study its spontaneous breaking from minimizing the Higgs vacuum potential. The domain wall problem is resolved by a unique soft breaking linear-term from the P-odd weak-singlet Higgs field. We also derive constraint from the Big-Bang nucleosynthesis. We then analyze the neutrino seesaw for both visible and mirror worlds, and demonstrate that the desired amounts of visible matter and mirror dark matter in the universe arise from a common origin of CP violation in the neutrino sector via leptogenesis. We derive the Higgs mass-spectrum and Higgs couplings with gauge bosons and fermions. We show their consistency with the direct Higgs searches and the indirect precision constraints. We further study the distinctive signatures of the predicted non-standard Higgs bosons at the LHC. Finally, we analyze the direct detections of GeV-scale mirror dark matter by TEXONO and CDEX experiments.

hep-ph↗

arXiv2012

GeV Scale Asymmetric Dark Matter from Mirror Universe: Direct Detection and LHC Signatures

Mirror universe is a fundamental way to restore parity symmetry in weak interactions. It naturally provides the lightest mirror nucleon as a unique GeV-scale asymmetric dark matter particle candidate. We conjecture that the mirror parity is respected by the fundamental interaction Lagrangian, and its possible soft breaking arises only from non-interaction terms in the gauge-singlet sector. We realize the spontaneous mirror parity violation by minimizing the vacuum Higgs potential, and derive the corresponding Higgs spectrum. We demonstrate that the common origin of CP violation in the visible and mirror neutrino seesaws can generate the right amount of matter and mirror dark matter via leptogenesis. We analyze the direct detections of GeV-scale mirror dark matter by TEXONO and CDEX experiments. We further study the predicted distinctive Higgs signatures at the LHC.

hep-ph↗

arXiv2010

Gauge-Invariant Quantum Gravity Corrections to Gauge Couplings via Vilkovisky-DeWitt Method and Gravity Assisted Gauge Unification

Gravity is the weakest force in nature, and the gravitational interactions with all standard model (SM) particles can be well described by perturbative expansions of the Einstein-Hilbert action as an effective theory, all the way up to energies below the fundamental Planck scale. We use Vilkovisky-DeWitt method to derive the first gauge-invariant nonzero gravitational power-law corrections to the running of gauge couplings, which make both Abel and non-Abel gauge interactions asymptotically free. We further demonstrate that the graviton-induced universal power-law runnings always assist the three SM gauge forces to reach unification around the Planck scale, irrespective of the detail of logarithmic corrections. We also compute the power-law corrections to the SM Higgs sector and derive modified triviality bound on the Higgs boson mass.

hep-th↗

arXiv2010

Common Origin of Soft mu-tau and CP Breaking in Neutrino Seesaw and the Origin of Matter

Neutrino oscillation data strongly support mu-tau symmetry as a good approximate flavor symmetry of the neutrino sector, which has to appear in any viable theory for neutrino mass-generation. The mu-tau breaking is not only small, but also the source of Dirac CP-violation. We conjecture that both discrete mu-tau and CP symmetries are fundamental symmetries of the seesaw Lagrangian (respected by interaction terms), and they are only softly broken, arising from a common origin via a unique dimension-3 Majorana mass-term of the heavy right-handed neutrinos. From this conceptually attractive and simple construction, we can predict the soft mu-tau breaking at low energies, leading to quantitative correlations between the apparently two small deviations θ_{23} - 45^o and θ_{13} - 0^o. This nontrivially connects the on-going measurements of mixing angle θ_{23} with the upcoming experimental probes of θ_{13}. We find that any deviation of θ_{23} - 45^o must put a lower limit on θ_{13}. Furthermore, we deduce the low energy Dirac and Majorana CP violations from a common soft-breaking phase associated with mu-tau breaking in the neutrino seesaw. Finally, from the soft CP breaking in neutrino seesaw we derive the cosmological CP violation for the baryon asymmetry via leptogenesis. We fully reconstruct the leptogenesis CP-asymmetry from the low energy Dirac CP phase and establish a direct link between the cosmological CP-violation and the low energy Jarlskog invariant. We predict new lower and upper bounds on the θ_{13} mixing angle, 1^o < θ_{13} < 6^o. In addition, we reveal a new hidden symmetry that dictates the solar mixing angle θ_12 by its group-parameter, and includes the conventional tri-bimaximal mixing as a special case, allowing deviations from it.

hep-ph↗

arXiv2010

Identifying Better Effective Higgsless Theories via W_L W_L Scattering

The three site Higgsless model has been offered as a benchmark for studying the collider phenomenology of Higgsless models. In this talk, we present how well the three site Higgsless model performs as a general representative of Higgsless models in describing W_L W_L scattering, and which modifications can make it more representative. We employ general sum rules relating the masses and couplings of the Kaluza-Klein (KK) modes of the gauge fields in continuum and deconstructed Higgsless models as a way to compare the different theories. After comparing the three site Higgsless model to flat and warped continuum Higgsless models, we analyze an extensions of the three site Higgsless model, namely, the Hidden Local Symmetry (HLS) Higgsless model. We demonstrate that W_LW_L scattering in the HLS Higgsless model can very closely approximate scattering in the continuum models, provided that the parameter `a' is chosen to mimic rho-meson dominance of pi-pi scattering in QCD.

hep-ph↗

arXiv2009

Double Type-II Seesaw, Baryon Asymmetry and Dark Matter for Cosmic e^\pm Excesses

We construct a new realization of type-II seesaw for neutrino masses and baryon asymmetry by extending the standard model with one light and two heavy singlet scalars besides one Higgs triplet. The heavy singlets pick up small vacuum expectation values to give a suppressed trilinear coupling between the triplet and doublet Higgs bosons after the light singlet drives the spontaneous breaking of lepton number. The Higgs triplet can thus remain light and be accessible at the LHC. The lepton number conserving decays of the heavy singlets can generate a lepton asymmetry stored in the Higgs triplet to account for the matter-antimatter asymmetry in the Universe. We further introduce stable gauge bosons from a hidden sector, which obtain masses and annihilate into the Higgs triplet after spontaneous breaking of the associated non-Abelian gauge symmetry. With Breit-Wigner enhancement, the stable gauge bosons can simultaneously explain the relic density of dark matter and the cosmic positron/electron excesses.

hep-ph↗