arXiv subjects

Bo-Qiang Ma

Publications and source records attributed to Bo-Qiang Ma.

At least 199 records · Page 11Linked to original sources

arXiv2009

A Model of Fermion Masses and Mixings Triggered by Family Problem in Warped Extra Dimensions

We suggest a model which addresses both the fermion mass hierarchy problem and the family problem in two-layer warped extra dimensions. In this model, 3 family fermions in 4 dimensions (4D) generate from 1 family in two-layer warped 6D by two step Kluza-Klein decompositions. The mass hierarchies are produced by the exponential behavior of 4D fermion zero mode profiles. The mixings and masses of fermions are closely related to the family problem. By adjusting parameters in this model, the numerical results can be very close to the experimental data both in the quark sector and in the lepton sector. In the lepton sector, we suppose neutrinos to be Dirac ones. The neutrino masses of sub-$\mathrm{eV}$ scale are obtained, and also CP violation emerges in the lepton sector.

hep-ph↗

arXiv2009

Lorentz violation dispersion relation and its application

We derive a modified dispersion relation (MDR) in the Lorentz violation extension of quantum electrodynamics (QED) sector in the standard model extension (SME) framework. Based on the extended Dirac equation and corresponding MDR, we observe the resemblance of the Lorentz violation coupling with spin-gravity coupling. We also develop a neutrino oscillation mechanism induced by the presence of nondiagonal terms of Lorentz violation couplings in 2-flavor space in a 2-spinor formalism by explicitly assuming neutrinos to be Marjorana fermions. We also obtain a much stringent bound ($\backsim10^{-25}$) on one of the Lorentz violation parameters by applying MDR to the ultrahigh energy cosmic ray (UHECR) problem.

hep-ph↗

arXiv2009

Nuclear EMC Effect in a Statistical Model

A simple statistical model in terms of light-front kinematic variables is used to explain the nuclear EMC effect in the range $x \in [0.2,~0.7]$, which was constructed by us previously to calculate the parton distribution functions (PDFs) of the nucleon. Here, we treat the temperature $T$ as a parameter of the atomic number $A$, and get reasonable results in agreement with the experimental data. Our results show that the larger $A$, the lower $T$ thus the bigger volume $V$, and these features are consistent with other models. Moreover, we give the predictions of the quark distribution ratios, \emph{i.e.}, $q^A(x) / q^D(x)$, $\bar{q}^A(x) / \bar{q}^D(x)$, and $s^A(x) / s^D(x)$, and also the gluon ratio $g^A(x) / g^D(x)$ for iron as an example. The predictions are different from those by other models, thus experiments aiming at measuring the parton ratios of antiquarks, strange quarks, and gluons can provide a discrimination of different models.

nucl-th↗

arXiv2009

Unified triminimal parametrizations of quark and lepton mixing matrices

We present a detailed study on triminimal parametrizations of quark and lepton mixing matrices with different basis matrices. We start with a general discussion on the triminimal expansion of the mixing matrix and on possible unified quark and lepton parametrization using quark-lepton complementarity (QLC). We then consider several interesting basis matrices and compare the triminimal parametrizations with the Wolfenstein-like parametrizations. The usual Wolfenstein parametrization for quark mixing is a triminimal expansion around the unit matrix as the basis. The corresponding QLC lepton mixing matrix is a triminimal expansion around the bimaximal basis. Current neutrino oscillation data show that the lepton mixing matrix is very well represented by the tri-bimaximal mixing. It is natural to take it as an expanding basis. The corresponding zeroth order basis for quark mixing in this case makes the triminimal expansion converge much faster than the usual Wolfenstein parametrization. The triminimal expansion based on tri-bimaximal mixing can be converted to the Wolfenstein-like parametrizations discussed in the literature. We thus have a unified description between different kinds of parametrizations for quark and lepton sectors: the standard parametrizations, the Wolfenstein-like parametrizations, and the triminimal parametrizations.

hep-ph↗

arXiv2009

Pretzelosity $h_{1T}^{\perp}$ and quark orbital angular momentum

We calculate the pretzelosity distribution ($h_{1T}^{\perp}$), which is one of the eight leading twist transverse momentum dependent parton distributions (TMDs), in the light-cone formalism. We find that this quantity has a simple relation with the quark orbital angular momentum distribution, thus it may provide a new possibility to access the quark orbital angular momentum inside the nucleon. The pretzelosity distribution can manifest itself through the $\sin(3ϕ_h-ϕ_S)$ asymmetry in semi-inclusive deep inelastic scattering process. We calculate the $\sin(3ϕ_h-ϕ_S)$ asymmetry at HERMES, COMPASS and JLab kinematics, and present our prediction on different targets including the proton, deuteron and neutron targets. Inclusion of transverse momentum cut in data analysis could significantly enhance the $\sin(3ϕ_h-ϕ_S)$ asymmetry for future measurements.

hep-ph↗

arXiv2008

Statistical effect in the parton distribution functions of the nucleon

A new and simple statistical approach is performed to calculate the parton distribution functions (PDFs) of the nucleon in terms of light-front kinematic variables. We do not put in any extra arbitrary parameter or corrected term by hand, which guarantees the stringency of our approach. Analytic expressions of the $x$-dependent PDFs are obtained in the whole $x$ region [0,1], and some features, especially the low-$x$ rise, are more agreeable with experimental data than those in some previous instant-form statistical models in the infinite-momentum frame (IMF). Discussions on heavy-flavored PDFs are also presented.

hep-ph↗

arXiv2008

Simple Classification of Light Baryons

We introduce a classification number $n$ which describes the baryon mass information in a fuzzy manner. According to $n$ and $J^p$ of baryons, we put all known light baryons in a simple table in which some baryons with same ($n$, $J^p$) are classified as members of known octets or decuplets. Meanwhile, we predict two new possible octets.

hep-ph↗

arXiv2008

Vector meson $ω$-$ϕ$ mixing and their form factors in light-cone quark model

The vector meson $ω$-$ϕ$ mixing is studied in two alternative scenarios with different numbers of mixing angles, i.e., the one-mixing-angle scenario and the two-mixing-angle scenario, in both the octect-singlet mixing scheme and the quark flavor mixing scheme. Concerning the reproduction of experimental data and the $Q^2$ behavior of transition form factors, one-mixing-angle scenario in the quark flavor scheme performs better than that in the octet-singlet scheme, while the two-mixing-angle scenario works well for both mixing schemes. The difference between the two mixing angles in the octet-singlet scheme is bigger than that in the quark flavor scheme.

hep-ph↗

arXiv2008

Triminimal Parametrization of Quark Mixing Matrix

Starting from a new zeroth order basis for quark mixing (CKM) matrix based on the quark-lepton complementarity and the tri-bimaximal pattern of lepton mixing, we derive a triminimal parametrization of CKM matrix with three small angles and a CP-violating phase as its parameters. This new triminimal parametrization has the merits of fast convergence and simplicity in application. With the quark-lepton complementary relations, we derive relations between the two unified triminimal parametrizations for quark mixing obtained in this work and for lepton mixing obtained by Pakvasa-Rodejohann-Weiler. Parametrization deviating from quark-lepton complementarity is also discussed.

hep-ph↗

arXiv2008

The influence of direct $D$-meson production to the determination on the nucleon strangeness asymmetry via dimuon events in neutrino experiments

Experimentally, the production of oppositely charged dimuon events by neutrino and anti-neutrino deep inelastic scattering (DIS) is used to determine the strangeness asymmetry inside a nucleon. Here we point out that the direct production of $D$-meson in DIS may make substantial influence to the measurement of nucleon strange distributions. The direct $D$-meson production is via the heavy quark recombination (HQR) and via the light quark fragmentation from perturbative QCD (LQF-P). To see the influence precisely, we compute the direct $D$-meson productions via HQR and LQF-P quantitatively and estimate their corrections to the analysis of the strangeness asymmetry. The results show that HQR has stronger effect than LQF-P does, and the former may influence the experimental determination of the nucleon strangeness asymmetry.

hep-ph↗

arXiv2008

$\cos 2 ϕ$ asymmetries in unpolarized semi-inclusive DIS

We use the Boer-Mulders functions parameterized from unpolarized $p+D$ Drell-Yan data by the FNAL E866/NuSea Collaboration combined with recently extracted Collins functions to calculate the $\cos 2 ϕ$ asymmetries in unpolarized semi-inclusive deeply inelastic scattering (SIDIS) processes both for ZEUS at Hadron Electron Ring Accelerator (HERA) and Jefferson Lab experiments (JLab), and to compare our results with their data. We also give predictions for the $\cos 2 ϕ$ asymmetries of SIDIS in the kinematical regime of HERMES Collaboration, and the forthcoming JLab experiments. We predict that the $\cos 2 ϕ$ asymmetries of semi-inclusive $π^-$ production are somewhat larger than that of $π^+$ production. We suggest to measure these two processes separately, which will provide more detail information on the Boer-Mulders functions as well as on the Collins functions.

hep-ph↗

arXiv2008

Fermion Families from Two Layer Warped Extra Dimensions

In extra dimensions, the quark and lepton mass hierarchy can be reproduced from the same order bulk mass parameters, and standard model fermion families can be generated from one generation in the high dimensional space. We try to explain the origin of the same order bulk mass parameters and address the family replication puzzle simultaneously. We show that they correlate with each other. We construct models that families are generated from extra dimensional space, and in the meantime the bulk mass parameters of same order emerge naturally. The interesting point is that the bulk mass parameters, which are in same order, correspond to the eigenvalues of a Schrödinger-like equation. We also discuss the problem existing in this approach.

hep-ph↗

arXiv2008

Muon Charge Ratio of Ultrahigh Energy Cosmic Rays

The muon charge ratio of ultrahigh energy cosmic rays may provide information to detect the composition of the primary cosmic rays. We propose to extract the charge information of high energy muons in very inclined extensive air showers by analyzing their relative lateral positions in the shower transverse plane.

astro-ph↗

arXiv2008

Left-right asymmetry in semi-inclusive deep inelastic scattering process

We analyze the left-right asymmetry of pion production in semi-inclusive deep inelastic scattering (SIDIS) process of unpolarized charged lepton on transversely polarized nucleon target. Unlike available treatments, in which some specific weighting functions are multiplied to separate theoretically motivated quantities, we do not introduce any weighting function following the analyzing method by the E704 experiment. The advantage is that this basic observable is free of any theoretical bias, although we can perform the calculation under the current theoretical framework. We present numerical calculations at both HERMES kinematics for the proton target and JLab kinematics for the neutron target. We find that with the current theoretical understanding, Sivers effect plays a key role in our analysis.

hep-ph↗

arXiv2008

Unified parametrization of quark and lepton mixing matrices in tri-bimaximal pattern

Parametrization of the quark and lepton mixing matrices is the first attempt to understand the mixing of fermions. In this work, we parameterize the quark and lepton matrices with the help of quark-lepton complementarity (QLC) in a tri-bimaximal pattern of lepton mixing matrix. In this way, we combine the parametrization of the two matrices with each other. We apply this new parametrization to several physical quantities, and show its simplicity in the expression of, e.g., the Jarlskog parameter of CP violation.

hep-ph↗

arXiv2008

Extracting Boer-Mulders functions from $p+D$ Drell-Yan processes

We extract the Boer-Mulders functions of valence and sea quarks in the proton from unpolarized $p+D$ Drell-Yan data measured by the FNAL E866 Collaboration. Using these Boer-Mulders functions, we calculate the $\cos 2 ϕ$ asymmetries in unpolarized $pp$ Drell-Yan processes, both for the FNAL E866/NuSea and the BNL Relativistic Heavy Ion Collider (RHIC) experiments. We also estimate the $\cos 2 ϕ$ asymmetries in the unpolarized $p\bar{p}$ Drell-Yan processes at GSI.

hep-ph↗

arXiv2008

A systematic phenomenological study of the $\cos 2 ϕ$ asymmetry in unpolarized semi--inclusive DIS

We study the $\cos 2 ϕ$ azimuthal asymmetry in unpolarized semi-inclusive DIS, taking into account both the perturbative contribution (gluon emission and splitting) and the non perturbative effects arising from intrinsic transverse motion and transverse spin of quarks. In particular we explore the possibility to extract from $<\cos 2 ϕ>$ some information about the Boer--Mulders function $h_1^{\perp}$, which represents a transverse--polarization asymmetry of quarks inside an unpolarized hadron. Predictions are presented for the HERMES, COMPASS and JLab kinematics, where $<\cos 2 ϕ>$ is dominated by the kinematical higher--twist contribution, and turns to be of order of few percent. We show that a larger asymmetry in $π^-$ production, compared to $π^+$ production, would represent a signature of the Boer--Mulders effect.

hep-ph↗

arXiv2008

Influence of Heavy Quark Recombination on the Nucleon Strangeness Asymmetry

The nucleon strange and anti-strange distribution asymmetry is an important issue in the study of the nucleon structure. In this work, we show that the heavy quark recombination processes from a perturbative QCD picture can give a sizable influence on the measurement of the nucleon strangeness asymmetry from charged-current charm production processes, such as the CCFR and NuTeV dimuon measurements. When the influence of heavy quark recombination is considered, a positive effective $δS^-_{\mathrm{HR}}$ should be added to the initially extracted strangeness asymmetry $S^-\equiv\int dx[s(x)-\bar s(x)]x$, supporting the strangeness asymmetry $S^-$ being positive, which is helpful to explain the NuTeV anomaly within the framework of the standard model.

hep-ph↗