118567855
Muon $g−2$, rare kaon decays, and parity violation from dark bosons
The muon g-2 discrepancy between theory and experiment may be explained by a light vector boson Z_d that couples to the electromagnetic current via kinetic mixing with the photon. We illustrate how the existing electron g-2, pion Dalitz decay, and other direct production data disfavor that explanation if the Z_d mainly decays into e+e-, mu+mu-. Implications of a dominant invisible Z_d decay channel, such as light dark matter, along with the resulting strong bounds from the rare K -> pi + 'missing energy' decay are examined. The K decay constraints may be relaxed if destructive interference effects due to Z-Z_d mass mixing are included. In that scenario, we show that accommodating the muon g-2 data through relaxation of K decay constraints leads to interesting signals for dark parity violation. As an illustration, we examine the alteration of the weak mixing angle running at low Q^2, which can be potentially observable in polarized electron scattering or atomic physics experiments.
118173341
Lightest U‐parity Particle (LUP): a hidden sector dark matter candidate
We introduce a new dark matter candidate, the lightest U‐parity particle (LUP). We suggest it as a good dark matter candidate especially in the R‐parity violating supersymmetric model.
118692473
“Dark” Z implications for parity violation, rare meson decays, and Higgs physics
General consequences of mass mixing between the ordinary Z boson and a relatively light Z_d boson, the "dark" Z, arising from a U(1)_d gauge symmetry, associated with a hidden sector such as dark matter, are examined. New effects beyond kinetic mixing are emphasized. Z-Z_d mixing introduces a new source of low energy parity violation well explored by possible future atomic parity violation and planned polarized electron scattering experiments. Rare K (B) meson decays into pi (K) l^+ l^- (l = e, mu) and pi (K) nu anti-nu are found to already place tight constraints on the size of Z-Z_d mixing. Those sensitivities can be further improved with future dedicated searches at K and B factories as well as binned studies of existing data. Z-Z_d mixing can also lead to the Higgs decay H -> Z Z_d, followed by Z -> l_1^+ l_1^- and Z_d -> l_2^+ l_2^- or "missing energy", providing a potential hidden sector discovery channel at the LHC. An illustrative realization of these effects in a 2 Higgs doublet model is presented.
119238978
Minimal gauge origin of baryon triality and flavorful signatures at the LHC
Abstract Baryon triality ( B 3 ) is a Z 3 discrete symmetry that can protect the proton from decay. Although its realization does not require supersymmetry, it is particularly appealing in the supersymmetry as an alternative to the popular R-parity. We discuss the issues in gauging B 3 , and present the minimal supersymmetric model with B 3 as the remnant discrete symmetry of a TeV scale U ( 1 ) gauge symmetry. A flavor-dependent U ( 1 ) charge is necessary to achieve this, and it results in very distinguishable and flavorful predictions for the LHC experiments. We find a complementarity between a 2-lepton sneutrino resonance and a 4-lepton Z ′ resonance in the supersymmetry search when a certain condition is satisfied. In addition, we introduce baryon tetrality ( B 4 ), which would play an equivalent role if there are four fermion generations.
118614634
Dark side of Higgs diphoton decays and muon g − 2
We propose that the LHC hints for a Higgs diphoton excess and the muon g-2 (g_mu-2) discrepancy between theory and experiment may be related by vector-like "leptons" charged under both U(1)_Y hypercharge and a "dark" U(1)_d. Quantum loops of such leptons can enhance the Higgs diphoton rate and also generically lead to U(1)_Y - U(1)_d kinetic mixing. The induced coupling of a light U(1)_d gauge boson Z_d to electric charge can naturally explain the measured g_mu-2. We update Z_d mass and coupling constraints based on comparison of the electron g-2 experiment and theory, and find that explaining g_mu-2 while satisfying other constraints requires Z_d to have a mass ~ 20-100 MeV. We predict new Higgs decay channels gamma Z_d and Z_d Z_d, with rates below the diphoton mode but potentially observable. The boosted Z_d -> e+e- in these decays would mimic a promptly converted photon and could provide a fraction of the apparent diphoton excess. More statistics or a closer inspection of extant data may reveal such events.
119542847
Revival of the Thermal Sneutrino Dark Matter
Studies of the rotation curves of galaxies, large scale structures, and recent measurements of the cosmic microwave background radiation, have confirmed that about 23% of the energy in the Universe is in the form of cold dark matter (CDM) [1]. The origin and the nature of CDM is one of the biggest puzzles in both particle physics and cosmology. Since all known particles are ruled out as dark matter candidates, dark matter provides the strongest phenomenological motivation for new physics beyond the Standard Model (SM). The Minimal Supersymmetric Standard Model (MSSM), supplemented with an exact discrete symmetry (R-parity), possesses two natural CDM candidates: the lightest neutralino and the lightest scalar neutrino (sneutrino). The former is a generic mixture of the superpartners of the neutral gauge and Higgs bosons, and its phenomenology has been the subject of extensive studies over the last 20 years [2]. In contrast, the left-handed (LH) sneutrinos of the MSSM have been ruled out as a major component of the dark matter in the Universe, by the combination of cosmological and experimental constraints. More precisely, LH sneutrinos are weakly charged, and typically annihilate too rapidly via Z-mediated s-channel diagrams, resulting in a relic density too small to account for all of the dark matter. To suppress the annihilation rate it was proposed that the sneutrinos should be either very light (O(GeV)) [3] or very heavy (O(TeV)) [4]. However, a very light sneutrino is excluded by the measurement of the invisible width of the Z gauge boson, while a very heavy sneutrino is excluded by direct dark matter searches [4]. Therefore, the LH sneutrinos of the MSSM are now disfavored as dark matter candidates. On the other hand, the recent evidence of neutrino masses provides strong impetus for extending the particle content of the MSSM with right-handed (RH) neutri� ∗
118867944
HIGHER DERIVATIVE OPERATORS AS COUNTERTERMS IN ORBIFOLD COMPACTIFICATIONS
In the context of 5D N = 1 supersymmetric models compactified on S1/Z2 or S1/(Z2×Z2′) orbifolds and with brane-localized superpotential, higher derivative operators are generated radiatively as one-loop counterterms to the mass of the (brane or zero mode of the bulk) scalar field. It is shown that the presence of such operators which are brane-localised is not related to the mechanism of supersymmetry breaking considered (F-term, discrete or continuous Scherk–Schwarz breaking) and initial supersymmetry does not protect against the dynamical generation of such operators. Since in many realistic models the scalar field is commonly regarded as the Higgs field, and the higher derivative operators seem a generic presence in orbifold compactifications, we stress the importance of these operators for solving the hierarchy problem.
92983543
Dark matter, {mu} problem, and neutrino mass with gauged R symmetry
We show that the {mu} problem and the strong CP problem can be resolved in the context of the gauged U(1){sub R} symmetry, realizing an automatic Peccei-Quinn symmetry. In this scheme, right-handed neutrinos can be introduced to explain small Majorana or Dirac neutrino mass. The U(1){sub R} D-term mediated supersymmetry (SUSY) breaking, called the U(1){sub R} mediation, gives rise to a specific form of the flavor-conserving superpartner masses. For the given solution to the {mu} problem, electroweak symmetry breaking condition requires the superpartners of the standard model at low energy to be much heavier than the gravitino. Thus, the dark matter candidate can be either gravitino or right-handed sneutrino. In the Majorana neutrino case, only gravitino is a natural dark matter candidate. On the other hand, in the Dirac neutrino case, the right-handed sneutrino can be also a dark matter candidate as it gets mass only from SUSY breaking. We discuss the non-thermal production of our dark matter candidates from the late decay of stau and find that the constraints from the big bang nucleosynthesis can be evaded for a TeV-scale stau mass.
10115013
Gauge Coupling Unification in Six Dimensions
We compute the one-loop gauge couplings in six-dimensional non-Abelian gauge theories on the T /Z2 orbifold with general GUT breaking boundary conditions. For concreteness, we apply the obtained general formulae to the gauge coupling running in a 6D SO(10) orbifold GUT where the GUT group is broken down to the standard model gauge group up to an extra U(1). We find that the one-loop corrections depend on the parity matrices encoding the orbifold boundary conditions as well as the volume and shape moduli of extra dimensions. When the U(1) is broken by the VEV of bulk singlets, the accompanying extra color triplets also affect the unification of the gauge couplings. In this case, the B − L breaking scale compatible with the gauge coupling unification is sensitive to the change of the compactification scales. E-mail address: hmlee@andrew.cmu.edu
9857534
Neutralino dark matter from heavy axino decay
We consider cosmological consequences of a heavy axino, decaying to the neutralino in R-parity conserving models. The importance and influence of the axino decay on the resultant abundance of neutralino dark matter depends on the lifetime and the energy density of axino. For a high reheating temperature after inflation, copiously produced axinos dominate the energy density of the universe, and its decay produces a large amount of entropy. As a bonus, we obtain that the upper bound on the reheating temperature after inflation via gravitino decay can be moderated, because the entropy production by the axino decay more or less dilutes the gravitinos.
119261616
Higgs portal inflation
The Higgs sector of the Standard Model offers a unique opportunity to probe the hidden sector. The Higgs squared operator is the only dimension two operator which is Lorentz and gauge invariant. It can therefore couple both to scalar curvature and the hidden sector at the dim-4 level. We consider the possibility that a combination of the Higgs and a singlet from the hidden sector plays the role of inflaton, due to their large couplings to gravity. This implies that the quartic couplings satisfy certain constraints which leads to distinct low energy phenomenology, including Higgs signals at the LHC. We also address the unitarity issues and show that our analysis survives the unitarization procedure.