arXiv subjects

Bo-Qiang Ma

Publications and source records attributed to Bo-Qiang Ma.

At least 163 records · Page 9Linked to original sources

arXiv2011

Neutrino Oscillations: from Standard and Non-standard Viewpoints

In the standard model of neutrino oscillations, the neutrino flavor states are mixtures of mass-eigenstates, and the phenomena are well described by the neutrino mixing matrix, i.e., the PMNS matrix. I review the recent progress on parametrization of the neutrino mixing matrix. Besides that I also discuss on the possibility to describe the neutrino oscillations by a non-standard model in which the neutrino mixing is caused by the Lorentz violation (LV) contribution in the effective field theory for LV. We assume that neutrinos are massless and that neutrino flavor states are mixing states of energy eigenstates. In our calculation the neutrino mixing parts depend on LV parameters and neutrino energy. The oscillation amplitude varies with the neutrino energy, thus neutrino experiments with energy dependence may test and constrain the Lorentz violation scenario for neutrino oscillation.

hep-ph↗

arXiv2011

B_c meson rare decays in the light-cone quark model

We investigate the rare decays $B_c \rightarrow D_s(1968) \ell \bar{\ell}$ and $B_c\rightarrow D_s^*(2317) \ell \bar{\ell}$ in the framework of the light-cone quark model (LCQM). The transition form factors are calculated in the space-like region and then analytically continued to the time-like region via exponential parametrization. The branching ratios and longitudinal lepton polarization asymmetries (LPAs) for the two decays are given and compared with each other. The results are helpful to investigating the structure of $B_c$ meson and to testing the unitarity of CKM quark mixing matrix. All these results can be tested in the future experiments at the LHC.

hep-ph↗

arXiv2011

The $\sin2ϕ$ azimuthal asymmetry in single longitudinally polarized $πN$ Drell-Yan process

We study the $\sin2ϕ$ azimuthal asymmetry in the $πN$ Drell-Yan process, when the nucleon is longitudinally polarized. The asymmetry is contributed by the combination of the Boer-Mulders function and the longitudinal transversity distribution function. We consider the Drell-Yan processes by $π^\pm$ beams colliding on the proton and deuteron targets, respectively. We calculate the $\sin2ϕ$ azimuthal asymmetries in these processes using the Boer-Mulders function and the longitudinal transversity from spectator models. We show that the study on single polarized $πN$ Drell-Yan processes can not only give the information on the new 3-dimensional parton distribution functions in momentum space, but also shed light on the chiral-odd structure of the longitudinally polarized nucleon.

hep-ph↗

arXiv2011

Tetramixing of vector and pseudoscalar mesons: A source of intrinsic quarks

The tetramixing of pseudoscalar mesons $π$-$η$-$η'$-$η_c$ and vector mesons $ω$-$ρ$-$ϕ$-$J/ψ$ are studied in the light-cone constituent quark model, and such mixing of four mesons provides a natural source for the intrinsic charm $c\bar{c}$ components of light mesons. By mixing with the light mesons, the charmonium states $J/ψ$ and $η_c$ could decay into light mesons more naturally, without introducing gluons or a virtual photon as intermediate states. Thus, the introduction of light quark components into $J/ψ$ is helpful to reproduce the new experimental data of $J/ψ$ decays. The mixing matrices and the $Q^2$ behaviors of the transition form factors are also calculated and compared with experimental data.

hep-ph↗

arXiv2011

Universal entropy bound and discrete space-time

Starting from the universal entropy bounds suggested by Bekenstein and Susskind and applying them to the black-body radiation situation, we get a cut-off of space $ Δx \geq χl_{\mathrm{P}}$ with $χ\geq 0.1$. We go further to get a cut-off of time $ Δt \geq χl_{\mathrm{P}}/c $, thus, the discrete space-time structure is obtained. With the discrete space-time, we can explain the uncertainty principle. Based on the hypothesis of information theory and the entropy of black holes, we get the precise value of the parameter $χ$ and demonstrate the reason why the entropy bounds hold.

hep-th↗

arXiv2011

A new relation between quark and lepton mixing matrices

We propose a new relation between quark mixing matrix and lepton mixing matrix. Since the parameters in the quark sector are well determined, we employ them to describe the mixing of leptons. Phenomenologically, we study the neutrino oscillation probabilities for different channels, which can be measured precisely in forthcoming reactor and accelerator experiments. As an example of the applicability of our assumption, CP violation in the lepton sector is also discussed. In the latest T2K experiment, the range of the mixing angle $θ_{13}$ is measured, and our prediction of $θ_{13}$ is compatible with their result.

hep-ph↗

arXiv2011

Note on a new fundamental length scale $l$ instead of the Newtonian constant $G$

The newly proposed entropic gravity suggests gravity as an emergent force rather than a fundamental one. In this approach, the Newtonian constant $G$ does not play a fundamental role any more, and a new fundamental constant is required to replace its position. This request also arises from some philosophical considerations to contemplate the physical foundations for the unification of theories. We here consider the suggestion to derive $G$ from more fundamental quantities in the presence of a new fundamental length scale $l$, which is suspected to originate from the structure of quantum space-time, and can be measured directly from Lorentz-violating observations. Our results are relevant to the fundamental understanding of physics, and more practically, of natural units, as well as explanations of experimental constraints in searching for Lorentz violation.

hep-th↗

arXiv2011

Lorentz violation induced vacuum birefringence and its astrophysical consequences

In the electromagnetism of loop quantum gravity, two helicities of a photon have different phase velocities and group velocities, termed as "vacuum birefringence". Two novel phenomenons, "peak doubling" and "de-polarization", are expected to appear for a linearly polarized light from astrophysical sources. We show that the criteria to observe these two phenomenons are the same. Further, from recently observed $γ$-ray polarization from Cygnus X-1, we obtain an upper limit $\sim 8.7\times10^{-12}$ for Lorentz-violating parameter $χ$, which is the most firm constraint from well-known systems. We also suggest to analyze possible existence of "peak doubling" through Fermi LAT GRBs.

astro-ph.HE↗

arXiv2011

Collins effect in semi-inclusive deep inelastic scattering process with a $^3$He target

We re-examine our previous calculation on the Collins effect in semi-inclusive deeply inelastic scattering (SIDIS) process with a $^3$He target, and find that our previous treatment on the dilution factors may cause the results larger than the realistic situation. We thus modify our calculation in an improved treatment with an updated prediction on the $\sin(ϕ_h+ϕ_S)$ asymmetry for the JLab 12 GeV under the transverse momentum dependent (TMD) factorization framework. Meanwhile, we also provide the prediction of such asymmetry for the JLab 6 GeV and the prediction of the $\sin(3ϕ_h-ϕ_S)$ asymmetry related to pretzelosity.

hep-ph↗

arXiv2011

Proposal for measuring new transverse momentum dependent parton distributions $g_{1T}$ and $h_{1L}^\perp$ through semi-inclusive deep inelastic scattering

We calculate $g_{1T}$ and $h_{1L}^\perp$, two of the eight leading twist transverse momentum dependent parton distributions (TMDs), in the light-cone quark-diquark model. The new TMDs can be measured through semi-inclusive deep inelastic scattering (SIDIS). We present predictions of the single and double spin asymmetries related to $g_{1T}$ and $h_{1L}^\perp$ in SIDIS at HERMES, COMPASS, and JLab kinematics respectively.

hep-ph↗

arXiv2011

Octet Quark Contents from SU(3) Flavor Symmetry

With the parametrization of parton distribution functions (PDFs) of the proton by Soffer \textit{et al.}, we extend the valence quark contents to other octet baryons by utilizing SU(3) flavor symmetry. We find the method practically useful. Fragmentation functions (FFs) are further obtained through the phenomenological Gribov-Lipatov relation at the $x \to 1$ region. Our results are compared with different models, and these different predictions can be discriminated by upcoming experiments.

hep-ph↗

arXiv2011

Probing pretzelosity $h^{\perp}_{1T}$ via the polarized proton-antiproton Drell-Yan process

We show that the polarized proton-antiproton Drell-Yan process is ideal to probe the pretzelosity distribution ($h_{1T}^\perp$), which is one of the new transverse-momentum-dependent parton distributions of the nucleon. We present predictions of the $\cos(2ϕ+ ϕ_a - ϕ_b)$ asymmetry in the transversely polarized proton-antiproton Drell-Yan process at PAX kinematics and find that the results are significantly larger compared with those of the $\sin(3ϕ_h - ϕ_S)$ asymmetry in the semi-inclusive deep inelastic scattering process at HERMES, COMPASS, and JLab kinematics. We conclude that the $\cos(2ϕ+ ϕ_a - ϕ_b)$ asymmetry in the PAX experiment can probe the new physical quantity of the pretzelosity distribution.

hep-ph↗

arXiv2011

Photon Gas Thermodynamics in Doubly Special Relativity

Doubly special relativity (DSR), with both an invariant velocity and an invariant length scale, elegantly preserves the principle of relativity between moving observers, and appears as a promising candidate of the quantum theory of gravity. We study the modifications of photon gas thermodynamics in the framework of DSR with an invariant length $|λ|$, after properly taking into account the effects of modified dispersion relation, upper bounded energy-momentum space, and deformed integration measure. We show that with a positive $λ$, the grand partition function, the energy density, the specific heat, the entropy, and the pressure are smaller than those of special relativity (SR), while the velocity of photons and the ratio of pressure to energy are larger. In contrast, with a negative $λ$, the quantum gravity effects show up in the opposite direction. However, these effects only manifest themselves significantly when the temperature is larger than $10^{-3} E_{\rm P}$. Thus, DSR can have considerable influence on the early universe in cosmological study.

hep-th↗

arXiv2011

Bose and Fermi gases in the early universe with self-gravitational effect

We study the self-gravitational effect on the equation of state (EoS) of Bose and Fermi gases in thermal equilibrium at the end of reheating, the period after quark-hadron transition and before Big Bang Nucleosynthesis (BBN). After introducing new grand canonical partition functions based on the work of Uhlenbeck and Gropper, we notice some interesting features of the newly developed EoSs with distinct behaviors of relativistic and non-relativistic gases under self-gravity. The usual negligence of the self-gravitational effect when solving the background expansion of the early universe is justified with numerical results, showing the magnitude of the self-gravitational modification of the state constant to be less than $O(10^{-78})$. This helps us to clarify the background thermal evolution of the primordial patch. Such clarification is crucial in testing gravity theories, evaluating inflation models and determining element abundances in BBN.

gr-qc↗

arXiv2011

Light flavor asymmetry of nucleon sea

The light flavor antiquark distributions of the nucleon sea are calculated in the effective chiral quark model and compared with experimental results. The contributions of the flavor-symmetric sea-quark distributions and the nuclear EMC effect are taken into account to obtain the ratio of Drell-Yan cross sections $σ^{\mathrm{pD}}/2σ^{\mathrm{pp}}$, which can match well with the results measured in the FermiLab E866/NuSea experiment. The calculated results also match the measured $\bar{d}(x)-\bar{u}(x)$ from different experiments, but unmatch the behavior of $\bar{d}(x)/\bar{u}(x)$ derived indirectly from the measurable quantity $σ^{\mathrm{pD}}/2σ^{\mathrm{pp}}$ by the FermiLab E866/NuSea Collaboration at large $x$. We suggest to measure again $\bar{d}(x)/\bar{u}(x)$ at large $x$ from precision experiments with careful experimental data treatment. We also propose an alternative procedure for experimental data treatment.

hep-ph↗

arXiv2011

Parametrization of fermion mixing matrices in Kobayashi-Maskawa form

Recent works show that the original Kobayashi-Maskawa (KM) form of fermion mixing matrix exhibits some advantages, especially when discussing problems such as unitarity boomerangs and maximal CP violation hypothesis. Therefore, the KM form of fermion mixing matrix is systematically studied in this paper. Starting with a general triminimal expansion of the KM matrix, we discuss the triminimal and Wolfenstein-like parametrizations with different basis matrices in detail. The quark-lepton complementarity relations play an important role in our discussions on describing quark mixing and lepton mixing in a unified way.

hep-ph↗

arXiv2011

Single spin asymmetry in $πp$ Drell-Yan process

We study the single spin asymmetries for the $πp^\uparrow\rightarrowμ^+μ^-X$ process. We consider the asymmetries contributed by the coupling of the Boer-Mulders function with the transversity distribution and the pretzelosity distribution, characterized by the $\sin(ϕ+ϕ_S)$ and $\sin(3ϕ-ϕ_S)$ azimuthal angular dependence, respectively. We estimate the magnitude of these asymmetries at COMPASS by using proper weighting functions. We find that the $\sin(ϕ+ϕ_S)$ asymmetry is of the size of a few percent and can be measured through the experiment. The $\sin(3ϕ-ϕ_S)$ asymmetry is smaller than the $\sin(ϕ+ϕ_S)$ asymmetry. After a cut on $q_T$, we succeed in enhancing the asymmetry.

hep-ph↗

arXiv2010

Isospin Symmetry Breaking in the Chiral Quark Model

We discuss the isospin symmetry breaking (ISB) of the valence- and sea-quark distributions between the proton and the neutron in the framework of the chiral quark model. We assume that isospin symmetry breaking is the result of mass differences between isospin multiplets and then analyze the effects of isospin symmetry breaking on the Gottfried sum rule and the NuTeV anomaly. We show that, although both flavor asymmetry in the nucleon sea and the ISB between the proton and the neutron can lead to the violation of the Gottfried sum rule, the main contribution is from the flavor asymmetry in the framework of the chiral quark model. We also find that the correction to the NuTeV anomaly is in an opposite direction, so the NuTeV anomaly cannot be removed by isospin symmetry breaking in the chiral quark model. It is remarkable that our results of ISB for both valence- and sea-quark distributions are consistent with the Martin-Roberts-Stirling-Thorne parametrization of quark distributions.

hep-ph↗