arXiv subjects

P. Q. Hung

Publications and source records attributed to P. Q. Hung.

At least 55 records · Page 3Linked to original sources

arXiv2007

Shadow vacuum alignment and dark energy

In a recent model of dark energy (with several phenomenological consequences), the universe is assumed to be trapped in a false vacuum with an energy density of the order of (10^{-3} eV)^4, mimicking the presently successful $ΛCDM$ scenario. This involves a new gauge group SU(2)_Z, {\em the shadow sector}, which becomes strong at a scale $Λ_Z \sim 10^{-3} eV$. The model is described by the SU(2)_Z instanton-induced potential of an axion-like scalar field, a_Z, with two degenerate vacuua. The false (metastable) vacuum appears as a result of an phenomenological (ad-hoc) soft breaking term linear in a_Z which explicitely breaks that degeneracy. In this paper, we discuss a possible dynamical origin for this soft breaking term as coming from the alignment of the vacuum along a direction in which the condensate of the shadow fermions, $<\barψ^{(Z)}_{i} i γ_{5} ψ^{(Z)}_{i}>$ which breaks spontaneously both P and CP, is non-vanishing. The present universe lives in a vacuum which violates both P and CP in the shadow SU(2)_Z sector!

hep-ph↗

arXiv2007

Implications of right-handed neutrinos with electroweak-scale masses

The possibility of constructing a model in which right-handed neutrinos have electroweak-scale masses as well as being {\em non-sterile} was espoused in Ref. 1. In this talk, I will review the ideas and results of Ref. 1 and discuss its implications for colliders such as the Tevatron, LHC and ILC.

hep-ph↗

arXiv2007

A model of electroweak-scale right-handed neutrino mass

If neutrino masses are realized through the see-saw mechanism, can the right-handed neutrinos be produced and detected at present and future colliders? The answer is negative in the most popular see-saw scenarios for the simple reason that they are too heavy in these models. However, a simple extension of the Standard Model (SM) particle content, including mirror fermions, two $SU(2)_L$ triplet and one singlet Higgs fields, leads to a scenario in which the see-saw mechanism is realized with the Majorana mass $M_R$ of the right-handed neutrino being of the order of the electroweak scale or smaller. A custodial SU(2) symmetry arising from the two triplet Higgs fields ensures that $ρ=1$ at tree level even when their vacuum expectation values (VEV) which determine the value of $M_R$, can be as large as the electroweak scale. $M_R$ is found to obey the bound $\frac{M_Z}{2} \leq M_R < 246 GeV $ which makes it accessible experimentally (Tevatron, LHC or ILC) since, in our scenario, $ν_R$'s can couple directly to the Standard Model (SM) gauge bosons.

hep-ph↗

arXiv2006

$E_6$ unification in a model of dark energy and dark matter

A model of dark energy and dark matter was proposed earlier by one of us (PQH) which involved an unbroken gauge group $SU(2)_Z$ whose coupling $α_Z \equiv g_Z^2/4 π\sim O(1)$ at a scale $Λ_Z \sim 3 \times 10^{-3} eV$ starting from a value within the range of the Standard Model (SM) couplings at a high energy scale $\sim 10^{16} GeV$. In that model, the universe is assumed to be presently trapped in a false vacuum with an energy density $\sim Λ_Z^4$. In this paper, we present a scenario in which $SU(2)_Z$ is unified with the SM through several steps: $E_6 \to SU(2)_Z \otimes SU(6) \to SU(2)_Z \otimes SU(3)_c \otimes SU(3)_L \otimes U(1) \to SU(2)_Z \otimes SU(3)_c \otimes SU(2)_L \otimes U(1)_Y$. This unification provides a rationale for why the value of the $SU(2)_Z$ coupling is within the range of the SM couplings at high energies. The particle content and the route of symmetry breaking in this model is very different from the usual $E_6$ unification encountered in the literature. Several implications, in addition to the dark energy, include the existence of heavy mirror particles which could be searched for at future colliders such as the LHC.

hep-ph↗

arXiv2006

Dark Energy and the False Vacuum

In this talk, I will present highlights of a recent model of dark energy and dark matter in which the present universe is ``trapped'' in a {\em false vacuum} described by the potential of an axion-like scalar field (the acceleron) which is related to a new strong interaction gauge sector, $SU(2)_Z$, characterized by a scale $Λ_Z \sim 3 \times 10^{-3} eV$. This false vacuum model mimicks the $ΛCDM$ scenario. In addition, there are several additional implications such as a new mechanism for leptogenesis coming from the decay of a ``messenger'' scalar field, as well as a new model of ``low-scale'' inflation whose inflaton is the ``radial'' partner of the acceleron.

astro-ph↗

arXiv2006

Low-scale inflation in a model of dark energy and dark matter

We present a complete particle physics model that explains three major problems of modern cosmology: inflation, dark matter and dark energy, and also gives a mechanism for leptogenesis. The model has a new gauge group $SU(2)_Z$ that grows strong at a scale $Λ\sim 10^{-3}$ eV. We focus on the inflationary aspects of the model. Inflation occurs with a Coleman-Weinberg potential at a low scale, down to $\sim 6\times 10^5\gev$, being compatible with observational data.

astro-ph↗

arXiv2006

A Model of Dark Energy and Dark Matter

A dynamical model for the dark energy is presented in which the ``quintessence'' field is the axion, $a_Z$, of a spontaneously broken global $U(1)_{A}^{(Z)}$ symmetry whose potential is induced by the instantons of a new gauge group $SU(2)_Z$. The $SU(2)_Z$ coupling becomes large at a scale $Λ_Z \sim 10^{-3} eV$ starting from an initial value $M$ at high energy which is of the order of the Standard Model (SM) couplings at the same scale $M$. A perspective on a possible unification of $SU(2)_Z$ with the SM will be briefly discussed. We present a scenario in which $a_Z$ is trapped in a false vacuum characterized by an energy density $\sim (10^{-3} eV)^4$. The lifetime of this false vacuum is estimated to be extremely large. Other estimates relevant to the ``coincidence issue'' include the ages of the universe when the $a_Z$ potential became effective, when the acceleration ``began'' and when the energy density of the false vacuum became comparable to that of (baryonic and non-baryonic) matter. Other cosmological consequences include a possible candidate for the weakly interacting (WIMP) Cold Dark Matter as well as a scenario for leptogenesis. A brief discussion on possible laboratory detections of some of the particles contained in the model will also be presented.

hep-ph↗

arXiv2005

A New Strong Interaction Sector as the origin for the Dark Energy and Dark Matter

A new strong interaction sector is proposed as a possible origin for the Dark Energy and Dark matter. It is described by an unbroken gauge group $SU(2)_Z$ which grows strong at a scale $Λ_Z \sim 10^{-3} eV$ provided its coupling is of the order of the electroweak coupling at some high energy scale (either $\sim 10^{16} GeV$ or $\sim O(TeV)$ . The present vacuum energy which is consistent with a cosmological constant is related to $Λ_Z$ and one of the $SU(2)_Z$ ``matter fields'' provides a candidate for the Dark Matter in the form of a weakly interacting massive particle (WIMP) with an annihilation cross section naturally of the order of the electroweak one at the time of its decoupling.

hep-ph↗

arXiv2005

Complete CKM quark mixing via dimensional deconstruction

It is shown that the deconstruction of $[SU(2)\times U(1)]^N$ into $[SU(2)\times U(1)]$ is capable of providing all necessary ingredients to completely impliment the complex CKM mixing of quark flavors. The hierarchical structure of quark masses originates from the difference in the deconstructed chiral zero-mode distribution in theory space, while the CP-violating phase comes from the genuinely complex vacuum expectation value of link fields. The mixing is constructed in a specific model to satisfy experimental bounds on quarks' masses and CP violation.

hep-ph↗

arXiv2005

Brane world unification of quark and lepton masses and its implication for the masses of the neutrinos

A TeV-scale scenario is constructed in an attempt to understand the relationship between quark and lepton masses. This scenario combines a model of early (TeV) unification of quarks and leptons with the physics of large extra dimensions. It demonstrates a relationship between quark and lepton mass scales at rather ``low'' (TeV) energies which will be dubbed as {\em early quark-lepton mass unification}. It also predicts that the masses of the neutrinos are naturally light and Dirac. There is an interesting correlation between neutrino masses and those of the unconventionally charged fermions which are present in the early unification model. If these unconventional fermions were to lie between 200 GeV and 300 GeV, the Dirac neutrino mass scale is predicted to be between 0.07 eV and 1 eV.

hep-ph↗

arXiv2004

Fermionic states in pure 4D deconstruction

We study the structure of fermionic mass eigenstates in a pure four-dimensional deconstruction approach. Unlike the case with the usual higher dimensional deconstruction (or latticized extra dimension), here the doubling of fermionic degrees of freedom is physical, thus there is no need to invoke Wilson terms to eliminate them. The fermionic structure is shaped by two key factors, namely the boundary conditions on fermions and the ratio of two breaking scales involved. The singular value decomposition theorem of linear algebra is employed to shed light into the phenomenologically crucial role of chiral boundary conditions. In this approach, we can explain the "localization" or "delocalization" nature of fermionic zero mode in flavor space and obtain analytically all higher modes. The application of boundary conditions on fermions to the implementation of CKM quark mixing is also found.

hep-ph↗

arXiv2004

Unconventional fermions: The Price of Quark-Lepton Unification at TeV Scales

The early petite unification (PUT) of quarks and leptons at TeV scales with sin^2 theta_W(M^2_Z) used as a constraint, necessitates the introduction of extra quarks and leptons with unconventional electric charges (up to 4/3 for the quarks and 2 for the leptons). This talk, in honor of Paul Frampton's 60th birthday, will be devoted to the motivation and construction of models of early unification and to their implications, including the issues of rare decays and unconventional fermions.

hep-ph↗

arXiv2004

Early SU(4)_PS x SU(2)_L x SU(2)_R x SU(2)_H Unification of Quarks and Leptons

We discuss various aspects of the early petite unification (PUT) of quarks and leptons based on the gauge group G_PUT=SU(4)_PS x SU(2)_L x SU(2)_R x SU(2)_H. This unification takes place at the scale M= O(1-2 TeV) and gives the correct value of sin^2 theta_W(M_Z^2) without the violation of the upper bound on the K_L -> mu e rate and the limits on FCNC processes. These properties require the existence of three new generations of unconventional quarks and leptons with charges up to 4/3 (for quarks) and 2 (for leptons) and masses O(250 GeV) in addition to the standard three generations of quarks and leptons. The horizontal group SU(2)_H connects the standard fermions with the unconventional ones. We work out the spontaneous symmetry breaking (SSB) of the gauge group G_PUT down to the SM gauge group, generalize the existing one-loop renormalization group (RG) analysis to the two-loop level including the contributions of Higgs scalars and Yukawa couplings, and demonstrate that the presence of three new generations of heavy unconventional quarks and leptons with masses O(250 GeV) is consistent with astrophysical constraints. The NLO and Higgs contributions to the RG analysis are significant while the Yukawa contributions can be neglected.

hep-ph↗

arXiv2003

Phenomenology of a Quark Mass Matrix from Six Dimensions and its implication for the Strong CP problem

A model of quark mass matrices from six dimensions, which is nearly democatic in nature and which is previously constructed by two of us (PQH and MS), is studied in detail in this manuscript. We found that not only it fits all the six quark masses as well as the CKM matrix but also that there exists a region in the allowed parameter space of the model where the constraint on the parameter \barθ of the Strong CP problem is satisfied. This region itself puts a constraint on the CKM parameters \barρ and \barη. As such, through our analysis, there appears to be a deep connection between Strong and Weak CP in this model

hep-ph↗

arXiv2003

Petite Unification of Quarks and Leptons: Twenty Two Years After

A recent surge of interest in the {\em early} unification of quarks and leptons, has prompted us to revive a paper \cite{HBB} written twenty two years ago. We provided there a general discussion of quark-lepton unification characterized by the gauge group $G_{S} \otimes G_{W}$ with two couplings $g_S$ and $g_W$ and by the unification mass scales $10\tev-1000\tev$. The constraint from $\sin^2 θ_{W}$ restricts the choices for $G_W$ and our favorite model was chosen to be $SU(4)_{\rm PS}\otimes SU(2)^4$. We review the main results of \cite{HBB}, update the original $SU(4)_{\rm PS}\otimes SU(2)^4$ model and propose two new models based on the groups $SU(4)_{\rm PS}\otimes SU(2)^3$ and $SU(4)_{\rm PS}\otimes SU(3)^2$ for which the consistency with the measured value of $\sin^{2}θ_{W}(M_{Z}^{2})$ determines the unification scale to be roughly $1 {\rm TeV}$ and $3-10 {\rm TeV}$, respectively. The implications of this very early unification is the existence of new quarks and leptons with charges up to 4/3 (for quarks) and 2 (for leptons) and masses $\ord(250\gev)$. Interestingly, in these models the rare decay $K_L\to μe$ is automatically absent at tree level and the one-loop contributions are consistent with the experimental upper bound for this decay.

hep-ph↗

arXiv2002

Almost Pure Phase Mass Matrices from Six Dimensions

A model of quark masses and mixing angles is constructed within the framework of two large extra compact dimensions. A ``democratic'' pure phase mass matrix arises in a rather interesting way. This type of mass matrix has often been used as a phenomenologically viable ansatz, albeit one which had very little dynamical justification. It turns out that the idea of Large Extra Dimensions provides a fresh look at this interesting phenomenological ansatz as presented in this paper. Some possible interesting connections to the strong CP problem will also be presented.

hep-ph↗

arXiv2002

A new mechanism for a naturally small Dirac neutrino mass

A mechanism is proposed in which a right-handed neutrino zero mode and a right-handed charged lepton zero mode can be localized at the same place along an extra compact dimension while having markedly different spreads in their wave functions: a relatively narrow one for the neutrino and a rather broad one for the charged lepton. In their overlaps with the wave function for the left-handed zero modes, this mechanism could produce a natural large hierarchy in the effective Yukawa couplings in four dimensions, and hence a large disparity in masses.

hep-ph↗

arXiv2001

Rare K decays in a model of quark and lepton masses

An extension of a model of neutrino masses to the quark sector provides an interesting link between these two sectors. A parameter which is important to describe neutrino oscillations and masses is found to be a crucial one appearing in various ``penguin'' operators, in particular the so-called Z penguin. This parameter is severely constrained by the rare decay process $K_{L} \to μ^{+} μ^{-}$. This in turn has interesting implications on the decay rates of other rare processes such as $K_{L} \to μe$, etc..., as well as on the masses of the neutrinos and the masses of the vector-like quarks and leptons which appear in our model.

hep-ph↗