119173786
Higgs-pair production in littlest Higgs model with T parity
The Higgs-pair production process at the CERN Large Hadron Collider, which will provide a way to test the Higgs boson self-coupling, may be sensitive to new physics. In the framework of the littlest Higgs model with T parity, such Higgs-pair production can proceed through additional loop diagrams, and thus the production rate can be quite different from the standard model prediction. Our calculations show that, due to the loop contributions of both T-even and T-odd quarks predicted in this model, the production rate can be significantly enhanced relative to the standard model prediction and also can be larger than the production rate in the minimal supersymmetric model. Also, we find that the T-odd quark contributions, which were not included in a previous study, are equally important compared with the T-even quark contributions.
118438822
Dark matter and Higgs phenomenology predicted by left-right twin Higgs model in light of CDMS II results
The left-right twin Higgs model predicts a light stable scalar Ŝ, which is a candidate for WIMP dark matter. We study its scattering on nucleon and find that the cross section is below the CDMS II upper bound but can reach the SuperCDMS sensitivity. Then we study the Higgs phenomenology by paying special attention to the decay h → ŜŜ which is strongly correlated with the dark matter scattering on nucleon. We find that such an invisible decay can be sizable, which can severely suppress the conventional decay modes like h → VV (V = W, Z) and $ h \to b\bar b $. On the other hand, compared to the SM prediction, the rates of Higgs boson productions at the LHC via gluon-gluon fusion, weak boson fusion or in association with top quark pairs are all reduced significantly, e.g., the gluon-gluon fusion channel can be suppressed by about 30%.
118505375
LHC diphoton Higgs signal and top quark forward-backward asymmetry in quasi-inert Higgs doublet model
A bstractIn the quasi-inert Higgs doublet model, we study the LHC diphoton rate for a standard model-like Higgs boson and the top quark forward-backward asymmetry at Tevatron. Taking into account the constraints from the vacuum stability, unitarity, electroweak precision tests, flavor physics and the related experimental data of top quark, we find that compared with the standard model prediction, the diphoton rate of Higgs boson at LHC can be enhanced due to the light charged Higgs contributions, while the measurement of the top quark forward-backward asymmetry at Tevatron can be explained to within 1σ due to the non-standard model neutral Higgs bosons contributions. Finally, the correlations between the two observables are discussed.
119209933
Higgs boson production in photon-photon collision at ILC: a comparative study in different little Higgs models
We study the process $ \gamma \gamma \to h \to b\bar b $ at ILC as a probe of different little Higgs models, including the simplest little Higgs model (SLH), the littlest Higgs model (LH), and two types of littlest Higgs models with T-parity (LHT-I, LHT-II). Compared with the Standard Model (SM) prediction, the production rate is found to be sizably altered in these little Higgs models and, more interestingly, different models give different predictions. We find that the production rate can be possibly enhanced only in the LHT-II for some part of the parameter space, while in all other cases the rate is suppressed. The suppression can be 10% in the LH and as much as 60% in both the SLH and the LHT-I/LHT-II. The severe suppression in the SLH happens for a large tan β and a small mh, in which the new decay mode h → ηη (η is a light pseudo-scalar) is dominant; while for the LHT-I/LHT-II the large suppression occurs when f and mh are both small so that the new decay mode h → AHAH is dominant. Therefore, the precision measurement of such a production process at the ILC will allow for a test of these models and even distinguish between different scenarios.
119289681
CMB dipole asymmetry from a fast roll phase
The observed CMB (cosmic microwave background) dipole asymmetry cannot be explained by a single field model of inflation - it inevitably requires more than one field where one of the fields is responsible for amplifying the super-Hubble fluctuations beyond the pivot scale. Furthermore the current constraints on fNL and τNL require that such an amplification cannot produce large non-Gaussianity. In this paper we propose a model to explain this dipole asymmetry from a spectator field, which is responsible for generating all the curvature perturbations, but has a temporary fast roll phase before the Hubble exit of the pivot scale. The current data prefers spectator scenario because it leaves no isocurvature perturbations. The spectator model will also satisfy the well-known constraints arising from quasars, and the quadrupole and octupole of the CMB.
118798405
Two Higgs bidoublet model with spontaneous P and CP violation and decoupling limit to the two Higgs doublet model
The two Higgs bidoublet left-right symmetric model (2HBDM) as a simple extension of the minimal left-right symmetric model with a single Higgs bidoublet is motivated to realize both spontaneous parity (P) violation and charge conjugation and parity (CP) violation while consistent with the low-energy phenomenology without significant fine-tuning. By carefully investigating the Higgs potential of the model, we find that sizable CP-violating phases are allowed after the spontaneous symmetry breaking. The mass spectra of the extra scalars in the 2HBDM are significantly different from the ones in the minimal left-right symmetric model. In particular, we demonstrate in the decoupling limit when the right-handed gauge-symmetry-breaking scale is much higher than the electroweak scale, the 2HBDM decouples into the general two Higgs doublet model with spontaneous CP violation and has rich induced sources of CP violation. We show that in the decoupling limit, it contains extra light Higgs bosons with masses around electroweak scale, which can be directly searched at the ongoing LHC and future International Linear Collider experiments.
119246009
What if bb does not dominate the decay of the Higgs-like boson?
The dominant decay mode of standard model Higgs at 126 GeV $b\bar{b}$ suffers from severe SM background at the LHC even in associated productions $Wh_{\rm SM}$ or $Z h_{\rm SM}$. The precision measurement of BR($\phi\to b\bar{b})$ requires more data to reduce its large error bar. We investigate the possibility of this channel with largest uncertainty not dominating the decay of Higgs-like boson discovered at the LHC. In such scenarios, the Higgs signal shows highly suppressed $b\bar{b}$, slightly reduced $\tau^{+}\tau^{-}$ and moderately enhanced gauge bosons comparing with the SM predictions. The model requires two different sources of electroweak symmetry breaking and radiative correction to $m_{b}$ strongly enhanced. However, large reduction in $b\bar{b}$ usually results large enhancement in $\tau^{+}\tau^{-}$ mode in particular. The reduction of $\tau^{+}\tau^{-}$ therefore implies that a new decay mode is inevitable. We find that a non-decoupling MSSM Higgs decay into lighter Higgs $H\to hh$ may fit the signature. Here, MSSM $H$ is identified as the 126 GeV resonance while $h$ is below $M_{H}/2$ and can evade the direct search bound at LEPII and Tevatron. Large $PQ$ and $R$ symmetry breaking effects mediated by strong interaction can strongly enhance radiative corrections in $m_b$. However, the scenario can only be realized in highly fine-tuned parameter region where $G_{Hhh}$ is tiny. Nevertheless, we discuss the discovery potential of this highly fine-tuned $H\to hh$ at the LHC.
7332532
Spectral measurement of electron antineutrino oscillation amplitude and frequency at Daya Bay.
A measurement of the energy dependence of antineutrino disappearance at the Daya Bay reactor neutrino experiment is reported. Electron antineutrinos (ν¯(e)) from six 2.9  GW(th) reactors were detected with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls. Using 217 days of data, 41 589 (203 809 and 92 912) antineutrino candidates were detected in the far hall (near halls). An improved measurement of the oscillation amplitude sin(2)2θ(13)=0.090(-0.009)(+0.008) and the first direct measurement of the ν¯(e) mass-squared difference |Δm(ee)2|=(2.59(-0.20)(+0.19))×10(-3)  eV2 is obtained using the observed ν¯(e) rates and energy spectra in a three-neutrino framework. This value of |Δm(ee)2| is consistent with |Δm(μμ)2| measured by muon neutrino disappearance, supporting the three-flavor oscillation model.
125000747
Search for the rare decays J/psi ---> D-(s) e+ nu(e), J/psi ---> anti-D0 e+ e-
Abstract We report on a search for the decays J / ψ → D s − e + ν e + c.c. , J / ψ → D − e + ν e + c.c. , and J / ψ → D 0 ¯ e + e − + c.c. in a sample of 5.8 × 10 7 J / ψ events collected with the BESII detector at the BEPC. No excess of signal above background is observed, and 90% confidence level upper limits on the branching fractions are set: B ( J / ψ → D s − e + ν e + c.c. ) 4.9 × 10 −5 , B ( J / ψ → D − e + ν e + c.c. ) 1.2 × 10 −5 , and B ( J / ψ → D 0 ¯ e + e − + c.c. ) 1.1 × 10 −5 .