arXiv subjects

Yu-Feng Zhou

Publications and source records attributed to Yu-Feng Zhou.

At least 73 records · Page 4Linked to original sources

arXiv2012

Direct and indirect constraints on isospin-violating dark matter

The scenario of isospin-violating dark matter (IVDM) with destructive interference between DM-proton and DM-neutron scatterings provides a potential possibility to reconcile the experimental results of DAMA, CoGeNT and XENON. We explore the constraints on the IVDM from other direct detection experiments such as CRESST and SIMPLE, etc. and from the indirect DM searches such as the antiproton flux measured by BESS-Polar II. The results show that the relevant couplings in IVDM scenario are severely constrained.

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arXiv2012

Two Higgs Bi-doublet Model With Spontaneous P and CP Violation and Decoupling Limit to Two Higgs Doublet Model

The two Higgs bi-doublet left-right symmetric model (2HBDM) as a simple extension of the minimal left-right symmetric model with a single Higgs bi-doublet is motivated to realize both spontaneous P and 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 general two Higgs doublet model (2HDM) 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 ILC experiments.

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arXiv2012

Probing the fourth generation Majorana neutrino dark matter

Heavy fourth generation Majorana neutrino can be stable and contribute to a small fraction of the relic density of dark matter (DM) in the Universe. Due to its strong coupling to the standard model particles, it can be probed by the current direct detection experiments even it is a subdominant component of the whole halo DM. Assuming that it contributes to the same fraction of the local halo DM density as that of the DM relic density, we show that the current Xenon100 data constrain the mass of the stable Majorana neutrino to be greater than the mass of the top quark. In the mass range between 200 GeV and a few hundred GeV, the effective spin-independent cross section for the neutrino elastic scattering off nucleon is insensitive to the neutrino mass and is predicted to be $\sim 1.5\times 10^{-44} cm^2$, which can be reached by the direct DM search experiments soon. In the same mass region the predicted effective spin-dependent cross section for the heavy neutrino scattering off proton is in the range $2\times 10^{-40} cm^2\sim 2\times 10^{-39} cm^2$, which is within the reach of the ongoing IceCube experiment. We demonstrate such properties in a fourth generation model with the stability of the fourth Majorana neutrino protected by an additional generation-dependent U(1) gauge symmetry.

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arXiv2011

Dark matter conversion as a source of boost factor for explaining the cosmic ray positron and electron excesses

In interacting multi-component dark matter (DM) models, if the DM components are nearly degenerate in mass and the interactions between them are strong enough, the relatively heavy DM components can be converted into lighter ones at late time after the thermal decoupling. Consequently, the relic density of the lightest DM component can be considerably enhanced at late time. This may contribute to an alternative source of boost factor required to explain the positron and electron excesses reported by the recent DM indirect search experiments such as PAMELA, Fermi-LAT and HESS etc..

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arXiv2011

Enhancement of dark matter relic density from the late time dark matter conversions

We demonstrate that if the dark matter (DM) in the Universe contains multiple components,the interactions between the DM components may induce DM conversions. It is then possible that the lightest DM component with an annihilation cross section much larger than that of the typical weakly interacting massive particle (WIMP) can obtain a relic density in consistent with the cosmological observations, due to an enhancement from the DM conversion process at late time after the thermal decoupling. This provides an alternative source of large boost factor required to explain the excesses reported by the recent DM indirect search experiments.

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arXiv2011

Probing $W^\prime_L WH$ and $W^\prime_R W H$ Interaction at LHC

Many new physics models predict the existence of TeV-scale charged gauge boson $W^\prime$ together with Higgs boson(s). We study the $W^\prime WH$ interaction and explore the angular distribution of charged lepton to distinguish $W_R^\prime WH$ from $W_L^\prime WH$ in $pp\to HW\to b \bar b l ν$ process at the LHC. It is found that a new type forward-backward asymmetry($A_{FB}$) relating to the angle between the direction of the charged lepton in $W$ rest frame and that of the reconstructed $W^\prime$ in laboratory frame is useful to investigate the properties of $W^\prime W H$ interaction. We analyze the Standard Model backgrounds and develop a set of cuts to highlight the signal and suppress the backgrounds at LHC. We find that $A_{FB}$ can reach 0.03(-0.07) for $W_R^\prime$($W_L^\prime$) production at $\sqrt{S}=14$ TeV.

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arXiv2010

Chiral Couplings of W' and Top Quark Polarization at the LHC

If a TeV-scale charged gauge boson (W') is discovered at the Large Hadron Collider (LHC), it will become imperative to determine its chiral couplings to standard model (SM) fermions in order to learn about the underlying theory containing the W'. We describe the reconstruction of the t, b decay mode of the W' at the LHC, and identify various kinematic observables such as the angular distributions of the top quark and the lepton resulting from top decay that can be used to disentangle the chiral couplings of the W' to SM fermions. We demonstrate by presenting analytical expressions, numerical simulations, as well as intuitive illustrations for these observables at the LHC that among the SM fermions, the polarized top quark can most directly probe the chirality of such couplings.

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arXiv2010

Searching for Dark Matter Signals in the Left-Right Symmetric Gauge Model with CP Symmetry

We investigate singlet scalar dark matter (DM) candidate in a left-right symmetric gauge model with two Higgs bidoublets (2HBDM) in which the stabilization of the DM particle is induced by the discrete symmetries P and CP. According to the observed DM abundance, we predict the DM direct and indirect detection cross sections for the DM mass range from 10 GeV to 500 GeV. We show that the DM indirect detection cross section is not sensitive to the light Higgs mixing and Yukawa couplings except the resonance regions. The predicted spin-independent DM-nucleon elastic scattering cross section is found to be significantly dependent on the above two factors. Our results show that the future DM direct search experiments can cover the most parts of the allowed parameter space. The PAMELA antiproton data can only exclude two very narrow regions in the 2HBDM. It is very difficult to detect the DM direct or indirect signals in the resonance regions due to the Breit-Wigner resonance effect.

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arXiv2010

Exploration of decaying dark matter in a left-right symmetric model

$SU(2)_L$ triplet scalars appear in models motivated for the left-right symmetry, neutrino masses and dark matter (DM), etc.. If the triplets are the main decay products of the DM particle, and carry nonzero lepton numbers, they may decay dominantly into lepton pairs, which can naturally explain the current experimental results reported by PAMELA and Fermi-LAT or ATIC. We discuss this possibility in an extended left-right symmetric model in which the decay of DM particle is induced by tiny soft charge-conjugation ($C$) violating interactions, and calculate the spectra for cosmic-ray positrons, neutrinos and gamma-rays. We show that the DM signals in the flux of high energy neutrinos can be significantly enhanced, as the triplets couple to both charged leptons and neutrinos with the same strength. In this scenario, the predicted neutrino-induced muon flux can be several times larger than the case in which DM particle only directly decays into charged leptons. In addition, the charged components of the triplet may give an extra contribution to the high energy gamma-rays through internal bremsstrahlung process, which depends on the mass hierarchy between the DM particle and the triplet scalars.

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arXiv2008

Gauge-singlet dark matter in a left-right symmetric model with spontaneous CP violation

We propose a dark matter (DM) scenario in an extension of a left-right symmetric model with a gauge-singlet scalar field. The gauge-singlet scalar can automatically become a DM candidate, provided that both P and CP symmetries are only broken spontaneously. Thus no extra discrete symmetries are needed to make the DM candidate stable. After constraining the model parameters from the observed relic DM density we make predictions for direct detection experiments. We show that for some parameter range, the predicted WIMP-nucleon elastic scattering cross section can reach the current experimental upper bound, which can be tested by the experiments in the near future.

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arXiv2008

Flavor symmetry analysis of charmless B --> VP decays

Based upon flavor SU(3) symmetry, we perform global fits to charmless B decays into one pseudoscalar meson and one vector meson in the final states. We consider different symmetry breaking schemes and find that the one implied by na{ï}ve factorization is slightly favored over the exact symmetry case. The $(\barρ,\barη)$ vertex of the unitarity triangle (UT) constrained by our fits is consistent with other methods within errors. We have found large color-suppressed, electroweak penguin and singlet penguin amplitudes when the spectator quark ends up in the final-state vector meson. Nontrivial relative strong phases are also required to explain the data. The best-fit parameters are used to compute branching ratio and CP asymmetry observables in all of the decay modes, particularly those in the $B_s$ decays to be measured at the Tevatron and LHC experiments.

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arXiv2008

Two Higgs Bi-doublet Left-Right Model With Spontaneous P and CP Violation

A left-right symmetric model with two Higgs bi-doublet is shown to be a consistent model for both spontaneous P and CP violation. The flavor changing neutral currents can be suppressed by the mechanism of approximate global U(1) family symmetry. We calculate the constraints from neural $K$ meson mass difference $Δm_K$ and demonstrate that a right-handed gauge boson $W_2$ contribution in box-diagrams with mass well below 1 TeV is allowed due to a cancellation caused by a light charged Higgs boson with a mass range $150 \sim 300$ GeV. The $W_2$ contribution to $ε_K$ can be suppressed from appropriate choice of additional CP phases appearing in the right-handed Cabbibo-Kobayashi-Maskawa matrix. The model is also found to be fully consistent with $B^0$ mass difference $Δm_B$, and the mixing-induced CP violation quantity $\sin2β_{J/ψ}$, which is usually difficult for the model with only one Higgs bi-doublet. The new physics beyond the standard model can be directly searched at the colliders LHC and ILC.

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arXiv2008

Mixing-induced CP violating sources for electroweak baryogenesis from a semiclassical approach

The effects of flavor mixing in electroweak baryogenesis is investigated in a generalized semiclassical WKB approach. Through calculating the nonadiabatic corrections to the particle currents it is shown that extra CP violation sources arise from the off-diagonal part of the equation of motion of particles moving inside the bubble wall. This type of mixing-induced source is of the first order in derivative expansion of the Higgs condensate, but is oscillation suppressed. The numerical importance of the mixing-induced source is discussed in the Minimal Supersymmetric Standard Model and compared with the source term induced by semiclassical force. It is found that in a large parameter space where oscillation suppression is not strong enough, the mixing-induced source can dominate over that from the semiclassical force.

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arXiv2008

Mixing-induced CP violating sources for electroweak baryogenesis

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arXiv2007

Constraining Charming Penguins in Charmless B Decays

We discuss the correlations of charming penguin contributions to $B\toππ$, $πK$ and KK using approximate flavor SU(3) symmetry. Strong constraints are found from the direct CP asymmetries especially in $πK$ modes. We make a global fit to the latest data and find that only a small charming penguin is allowed, and the size of color-suppressed tree amplitude (C) relative to tree amplitudes (T) remains large $C/T\simeq0.6$, which disfavors the possibility of a large charming penguin as an explanation for the $ππ$ puzzle. We show that a small charming penguin can still have sizable effect in the time-dependence CP asymmetries in KK mode.

hep-ph↗

arXiv2007

A Two Higgs Bi-doublet Left-Right Model With Spontaneous CP Violation

We discuss a left-right symmetric model with two Higgs bi-doublet and spontaneous P and CP violation. The flavor changing neutral currents is suppressed by assuming approximate global U(1) family symmetry. We calculate the constraints from neural K meson mass difference Δm_K and demonstrate that a right-handed gauge boson W_2 contribution in box-diagrams with mass around 600 GeV is allowed due to a negative interference with a light charged Higgs boson around 150 \sim 300 GeV. The W_2 contribution to ε_K is suppressed from appropriate choice of additional CP phases appearing in the right-handed Cabbibo-Kobayashi-Maskawa(CKM) matrix. The model is found fully consistent with B^0 mass difference and the mixing-induced CP asymmetry measurements.

hep-ph↗

arXiv2007

Flavor SU(3) analysis of charmless B->PP decays

We perform a global fits to charmless $B \to PP$ decays which independently constrain the $(\barρ,\barη)$ vertex of the unitarity triangle. The fitted amplitudes and phase are used to predict the branching ratios and CP asymmetries of all decay modes, including those of the $B_s$ system. Different schemes of SU(3) breaking in decay amplitude sizes are analyzed. The possibility of having a new physics contribution to $K π$ decays is also discussed.

hep-ph↗

arXiv2006

Flavor SU(3) analysis of charmless B meson decays to two pseudoscalar mesons

Global fits to charmless B --> PP decays in the framework of flavor SU(3) symmetry are updated and improved without reference to the \sin2βmeasured from the charmonium decay modes. Fit results directly constrain the (\barρ,\barη) vertex of the unitarity triangle, and are used to predict the branching ratios and CP asymmetries of all decay modes, including those of the B_s system. Different schemes of SU(3) breaking in decay amplitude sizes are analyzed. The major breaking effect between strangeness-conserving and strangeness-changing decays can be accounted for by including a ratio of decay constants in tree and color-suppressed amplitudes. The possibility of having a new physics contribution to K πdecays is also examined from the data fitting point of view.

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