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Shou-Hua Zhu

Publications and source records attributed to Shou-Hua Zhu.

18 recordsLinked to original sources
arXiv2022

Massive On-shell Recursion Relations for n-point Amplitudes

We construct two and three-line shifts for tree-level amplitude with massless and/or massive particles, and provide a method to construct general multi-line shifts for all masses. We choose the massless-massive BCFW shift from these shifts and examine its validity in renormalizable theories. Using such a shift, we find that amplitudes with at least one massless vector boson are constructible. This reveals the importance of gauge theory in the construction of amplitudes with massive particles. We also find that this kind of amplitudes have a cancellation related to group structure among different channels, which is essential for constructibility. Furthermore, we show that in the limit of large shift parameter $z$, the amplitude with four massive vector bosons, which can include transverse massive vector particles, have structures proportional to the amplitude with shifted vector particles replaced by Goldstone bosons in the leading order. This is responsible for the failure of massive-massive BCFW recursion relations in the amplitudes with four massive vector bosons.

hep-th↗
arXiv2021

Dark Matter Freeze-out via Catalyzed Annihilation

We present a new paradigm of dark matter freeze-out, where the annihilation of dark matter particles is catalyzed. We discuss in detail the regime that the depletion of dark matter proceeds via $2χ\to 2A'$ and $3A' \to 2χ$ processes, in which $χ$ and $A'$ denote dark matter and the catalyst respectively. In this regime, the dark matter number density is depleted polynomially rather than exponentially (Boltzmann suppression) as in classic WIMPs and SIMPs. The paradigm applies for a secluded weakly interacting dark sector with a dark matter in the $\text{MeV-TeV}$ mass range. The catalyzed annihilation paradigm is compatible with CMB and BBN constraints, with enhanced indirect detection signals.

hep-ph↗
arXiv2019

Effective Field Theory Perspective on Next-to-Minimal Composite Higgs

We study both the CP-even and CP-odd effective chiral Lagrangians of next minimal composite Higgs model {with symmetry breaking pattern depicted by the coset $SO(6)/SO(5)$} through the sigma/omega decomposition, in which the Goldstone matrix of the coset is decomposed in terms of the standard model Higgs doublet and an additional scalar singlet $s$ at the electroweak scale. The effective Lagrangian is described by the electroweak chiral Lagrangian up to $p^4$ order, with a function dependence on the Higgs boson and new scalar $s$, named Higgs function. This function in the effective Lagrangian incorporates the Higgs non-linearity or vacuum misalignment effects in the next minimal composite Higgs model, due to the Riemann curvature on the Nambu-Goldstone bosons scalar manifold, leads to various Higgs couplings deviated from the standard model ones, and also indicates the relations among different Higgs couplings in the low energy. Matching to the Higgs effective field theory below the electroweak scale, we obtain various low energy observables such as the electroweak oblique parameters, anomalous triple and quartic gauge couplings, anomalous couplings of Higgs to gauge bosons, in which the Higgs non-linearity effects are encoded in the ratio $ξ\equiv v^2/f^2$ of the electroweak scale and the new physics scale.

hep-ph↗
arXiv2019

EFTs meet Higgs Nonlinearity, Compositeness and (Neutral) Naturalness

Composite Higgs and neutral-naturalness models are popular scenarios in which the Higgs boson is a pseudo Nambu-Goldstone boson, and naturalness problem is addressed by composite top partners. Since the standard model effective field theory (SMEFT) with dimension-six operators cannot fully retain the information of Higgs nonlinearity due to its PNGB nature, we systematically construct low energy Lagrangian in which the information of compositeness and Higgs nonlinearity are encoded in the form factors, the two-point functions in the top sector. We classify naturalness conditions in various scenarios, and first present these form factors in composite neutral naturalness models. After extracting out Higgs effective couplings from these form factors and performing the global fit, we find the value of Higgs top coupling could still be larger than the standard model one if the top quark is embedded in the higher dimensional representations. Also we find the impact of Higgs nonlinearity is enhanced by the large mass splitting between composite states. In this case, pattern of the correlation between the $t\bar{t}h$ and $t\bar{t}hh$ couplings is quite different for the linear and nonlinear Higgs descriptions.

hep-ph↗
arXiv2018

Non-Thermal Cosmic Rays During Big Bang Nucleosynthesis to Solve the Lithium Problem

The discrepancy between the theoretical prediction of primordial lithium abundances and astronomical observations is called the Lithium Problem. We find that extra contributions from non-thermal hydrogen and helium during Big Bang nucleosynthesis can explain the discrepancy, for both Li-7 and Li-6, and will change the deuterium abundance only little. The allowed parameter space of such an amount of non-thermal particles and the energy range is shown. The hypothesis is stable regardless of the cross-section uncertainty of relevant reactions and the explicit shape of the energy spectrum.

astro-ph.CO↗
arXiv2010

Gamma rays and neutrinos from dark matter annihilation in galaxy clusters

The $γ$-ray and neutrino emissions from dark matter (DM) annihilation in galaxy clusters are studied. After about one year operation of Fermi-LAT, several nearby clusters are reported with stringent upper limits of GeV $γ$-ray emission. We use the Fermi-LAT upper limits of these clusters to constrain the DM model parameters. We find that the DM model distributed with substructures predicted in cold DM (CDM) scenario is strongly constrained by Fermi-LAT $γ$-ray data. Especially for the leptonic annihilation scenario which may account for the $e^{\pm}$ excesses discovered by PAMELA/Fermi-LAT/HESS, the constraint on the minimum mass of substructures is of the level $10^2-10^3$ M$_{\odot}$, which is much larger than that expected in CDM picture, but is consistent with a warm DM scenario. We further investigate the sensitivity of neutrino detections of the clusters by IceCube. It is found that neutrino detection is much more difficult than $γ$-rays. Only for very heavy DM ($\sim 10$ TeV) together with a considerable branching ratio to line neutrinos the neutrino sensitivity is comparable with that of $γ$-rays.

astro-ph.HE↗
arXiv2009

Clumpiness enhancement of charged cosmic rays from dark matter annihilation with Sommerfeld effect

Boost factors of dark matter annihilation into antiprotons and electrons/positrons due to the clumpiness of dark matter distribution are studied in detail in this work, taking the Sommerfeld effect into account. It has been thought that the Sommerfeld effect, if exists, will be more remarkable in substructures because they are colder than the host halo, and may result in a larger boost factor. We give a full calculation of the boost factors based on the recent N-body simulations. Three typical cases of Sommerfeld effects, the non-resonant, moderately resonant and strongly resonant cases are considered. We find that for the non-resonant and moderately resonant cases the enhancement effects of substructures due to the Sommerfeld effect are very small ($\sim \mathcal{O}(1)$) because of the saturation behavior of the Sommerfeld effect. For the strongly resonant case the boost factor is typically smaller than $\sim \mathcal{O}(10)$. However, it is possible in some very extreme cases that DM distribution is adopted to give the maximal annihilation the boost factor can reach up to $\sim 1000$. The variances of the boost factors due to different realizations of substructures distribution are also discussed in the work.

astro-ph.HE↗
arXiv2008

Generalization of Friedberg-Lee Symmetry

We study the possible origin of Friedberg-Lee symmetry. First, we propose the generalized Friedberg-Lee symmetry in the potential by including the scalar fields in the field transformations, which can be broken down to the FL symmetry spontaneously. We show that the generalized Friedberg-Lee symmetry allows a typical form of Yukawa couplings, and the realistic neutrino masses and mixings can be generated via see-saw mechanism. If the right-handed neutrinos transform non-trivially under the generalized Friedberg-Lee symmetry, we can have the testable TeV scale see-saw mechanism. Second, we present two models with the $SO(3)\times U(1)$ global flavour symmetry in the lepton sector. After the flavour symmetry breaking, we can obtain the charged lepton masses, and explain the neutrino masses and mixings via see-saw mechanism. Interestingly, the complete neutrino mass matrices are similar to those of the above models with generalized Friedberg-Lee symmetry. So the Friedberg-Lee symmetry is the residual symmetry in the neutrino mass matrix after the $SO(3)\times U(1)$ flavour symmetry breaking.

hep-ph↗
arXiv2004

Higgs Boson Production in gamma-gamma Collisions via Resolved Photon Contributions

We studied single Higgs boson production in $γγ$ collisions proceeding via the hadronic content of the photon. For SM Higgs masses of current theoretical interest, the resolved photon contributions are non-negligible in precision cross section measurements. We found that production of the heavier Higgs bosons H^0 and A^0 of the MSSM can probe regions of the SUSY parameter space that will complement other measurements. Finally, we showed that associated t H^\pm production in gamma-gamma collisions can be used to make an accurate determination of tan(beta) for low and high tan(beta)by precision measurements of the gamma gamma to H^\pm t +X cross section.

hep-ph↗
arXiv2001

B_s \to \ell^+ \ell^- in a model II 2HDM and MSSM

In this paper we analyze the process $B_s \to \ell^+ \ell^-$ in a model II 2HDM and MSSM. All the leading terms of Wilson coefficients relevant to the process are given in the large tan$β$ limit. It is shown that the decay width for $B_s \to \ell^+ \ell^-$ depends on all parameters except $m_{A^0}$ in the 2HDM. The branching ratio of $B_s \to μ^+ μ^-$ can reach its experimental bound in some large tan$β$ regions of the parameter space in MSSM because the amplitude increases like tan$^3β$ in the regions. For l=$τ$, the branching ratio can even reach $10^{-4}$ in the regions. Therefore, the experimental measurements of leptonic decays of $B_s$ could put a constraint on the contributions of neutral Higgs bosons and consequently the parameter space in MSSM.

hep-ph↗
arXiv2001

Renormalizaion group equations and infrared quasi fixed point behaviors of non-universal soft terms in MSSM

The renormalization group equations(RGEs) of non-universal soft supersymmetric breaking terms with CP violating phases are analyzed in this paper. We obtain the analytic solutions of RGEs by directly solving the RGEs themselves. Compared with the method of spurion expansion our approach proves to be simple and succinct, and easy to extend to the case of complex parameters. With the analytical forms of the solutions we obtained the infrared quasi fixed point behavior of soft terms are analyzed and it turns out to support the notion in scenarios with CP violating phases.

hep-ph↗
arXiv2000

Exclusive semileptonic rare decays $B ->_ ($K,K^*) \ell^+ \ell^- in supersymmetric theories

The invariant mass spectrum, forward-backward asymmetry, and lepton polarizations of the exclusive processes $B\to K(K^*)\ell^+ \ell^-, \ell=μ, τ$ are analyzed under supersymmetric context. Special attention is paid to the effects of neutral Higgs bosons (NHBs). Our analysis shows that the branching ratio of the process $\bkm$ can be quite largely modified by the effects of neutral Higgs bosons and the forward-backward asymmetry would not vanish. For the process $\bksm$, the lepton transverse polarization is quite sensitive to the effects of NHBs, while the invariant mass spectrum, forward-backward asymmetry, and lepton longitudinal polarization are not. For both $\bkt$ and $\bkst$, the effects of NHBs are quite significant. The partial decay widths of these processes are also analyzed, and our analysis manifest that even taking into account the theoretical uncertainties in calculating weak form factors, the effects of NHBs could make SUSY shown up.

hep-ph↗
arXiv1999

Bottom-Strange Associated Production at High Energy $e^{+}e^{-}$ Colliders in Standard Model

We investigate the flavor changing neutral current bsV(V=$γ$,Z) couplings in the production vertex for the process $e^+e^-\to b\bar s or \bar b s$ in the standard model. The precise calculations keeping all quark masses non-zero are carried out. Production cross sections are found to be the order of $10^{-3}$ fb at LEP II and the order of $10^{-1}$ fb when center-of-mass energy is near the mass of neutral gauge boson Z.

hep-ph↗
arXiv1999

The Supersymmetric QCD Radiative Corrections to Top Quark Semileptonic Decays

The one-loop supersymmetric QCD corrections to the top quark semileptonic decays $t\to b \bar{l} {ν_l}$ are considered. The corrections are found to reduce the decay width. In the still acceptable parameter space the corrections to the percentage change in top quark semileptonic decay width can reach the level of -0.7%.

hep-ph↗
arXiv1999

Top-Charm Associated Production at High Energy e^+e^- Colliders in Standard Model

The flavor changing neutral current tcV (V=γ,Z) couplings in the production vertex for the process $e^+e^-\to t\bar c$ or $\bar t c$ in the standard model are investigated. The precise calculations keeping all quark masses non-zero are carried out. The total production cross section is found to be $1.84 \times 10^{-9}$ fb at $\sqrt s =200 GeV$ and $0.572 \times 10^{-9}$ fb at $\sqrt s =500 GeV$ respectively. The result is much smaller than that given in ref. \cite{clwy} by a factor of $10^{-5}$.

hep-ph↗
arXiv1998

Top Quark Loop Corrections to the Neutral Higgs Boson Production at the Fermilab Tevatron

We calculate the $O(αm_t^2/m^2_W)$ corrections arising from diagrams involving the top-quark loops to the light neutral Higgs boson production via $q\bar q'\to WH$ at the Fermilab Tevatron in both the standard model and the minimal supersymmetric model. In contrast to the QCD correction which increases the tree-level cross section, the corrections imply a few percent reduction in the production cross section relative to the tree-leve results.

hep-ph↗
arXiv1998

Radiative Higgs Boson Decays H\to f\bar{f}γBeyond the Standard Model

Neutral Higgs boson radiative decays of the form h_0, H, A \to f\bar{f}γ, in the light fermion limit $m_f->0, are calculated in the two Higgs doublet model at one-loop level. Comparisons with the calculation within the standard model are given, which indicates that these two models are distinguishable in the decay mode fermion-antifermion -photon. Our results show that the concerned process may stand as an implement to identify the Higgs belongings in case there is a intermediate mass Higgs detected.

hep-ph↗