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Jen-Chieh Peng

Publications and source records attributed to Jen-Chieh Peng.

53 records · Page 3Linked to original sources
arXiv2013

Probing flavor-dependent EMC effect with W boson production

A recent theoretical model predicts that the modification of quark distributions in the nuclear medium (EMC effect) depends on the flavor of the quarks. We investigate $W$-boson production in proton-nucleus collision as a possible tool to test this theoretical prediction. Several experimental observables in $W$ production sensitive to the flavor-dependent EMC effect are identified. Calculations for these experimental observables at the RHIC and LHC energies are presented using the recent flavor-dependent EMC model.

hep-ph↗
arXiv2012

Connected-Sea Partons

According to the path-integral formalism of the hadronic tensor, the nucleon sea contains two distinct components called connected sea (CS) and disconnected sea (DS). We discuss how the CS and DS are accessed in the lattice QCD calculation of the moments of the parton distributions. We show that the CS and DS components for $\bar u(x) + \bar d(x)$ can be extracted by using recent data on the strangeness parton distribution, the CT10 global fit, and the lattice result of the ratio of the strange to $u(d)$ moments in the disconnected insertion. The extracted CS and DS for $\bar u(x) + \bar d(x)$ have distinct Bjorken $x$ dependence in qualitative agreement with expectation. The analysis also shows that the momentum fraction of the $\bar u(x) + \bar d(x)$ is about equally divided between CS and DS at $Q^2 = 2.5 {\rm GeV}^2$. Implications on future global analysis for parton distributions are presented.

hep-ph↗
arXiv2012

Nucleon sea and the five-quark components

We generalize the approach of Brodsky {\it et al.} for the intrinsic charm quark distribution in the nucleons to the light-quark sector involving intrinsic $\bar u, \bar d, s$ and $\bar s$ sea quarks. We compare the calculations with the existing $\bar d - \bar u$, $s + \bar s$, and $\bar u + \bar d - s -\bar s$ data. The good agreement between the theory and the data is interpreted as evidence for the existence of the intrinsic light-quark sea in the nucleons. The probabilities for the $|uudu\bar{u}>$, $|uudd\bar{d}>$ and $|uuds\bar{s}>$ Fock states are also extracted.

hep-ph↗
arXiv2012

Extraction of Various Five-Quark Components of the Nucleons

We have generalized the approach of Brodsky {\it et al.} for the intrinsic charm quark distribution in the nucleons to the light-quark sector involving intrinsic $\bar u, \bar d, s$ and $\bar s$ sea quarks. We compare the calculations with the existing $\bar d - \bar u$, $s + \bar s$, and $\bar u + \bar d - s -\bar s$ data. The good agreement between the theory and the data allows the extraction of the probabilities for the $|uudu\bar{u}>$, $|uudd\bar{d}>$, and $|uuds\bar{s}>$ five-quark Fock states in the proton. We also calculate the $x$-dependence of the intrinsic charm after taking into consideration the QCD evolution of the intrinsic quark distribution.

hep-ph↗
arXiv2011

Dependence of Neutrino Mixing Angles and CP-violating Phase on Mixing Matrix Parametrizations

We consider various neutrino mixing matrix parametrizations and the dependence of the mixing angles and CP-violating phase on the different parametrizations. The transformations of neutrino mixing parameters between various parametrizations are presented. Although the $θ_{13}$ mixing angle is determined to be small in the conventional parametrization, we note that in several other parametrizations the values of $θ_{13}$ are quite large. Should the value of $θ_{13}$ turn out to be tiny in the conventional parametrization, this study suggests that other alternative mixing matrix representations would be more suitable for dertermining the value of the CP-violating phase.

hep-ph↗
arXiv2011

Extraterrestrial Solar Neutrino Physics

We advocate the extraterrestrial solar neutrino physics (etSNP) as a means of investigating solar neutrino physics (SNP). As we already know, the dominant and subdominant (vacuum) oscillation lengths would be approximately one kilometer and one hundred kilometers. On the other hand, we know so far that the matter-enhanced oscillations take place only in the core of the Sun. Thus, the etSNP, i.e. solar neutrino physics that could be extracted outside the Earth, would assume a special unique role. The etSNP experiments include (1) a satellite (detector) around the Earth or around the Jupiter or others (to provide the shadow, for the matter-enhanced neutrino oscillations), (2) during the Sun-Venus-Earth eclipse or similar, and (3) the chemical compositions of the geology type (as in the Jupiter or in the Venus, to study the origins of these planets). To be specific, we note that the reactions induced by the ^8B solar neutrinos, in view of the sole high energy nature (E_ν^{max}=14.03 MeV), would be most interesting in the solar environment. Moreover, the experiments such as the chemical compositions of the geology type (on the Venus or Jupiter) and the matter-enhanced oscillations when the Sun-Venus-Earth eclipse, or the Sun-Mercury-Earth eclipse, may also be interesting.

hep-ph↗
arXiv2011

Flavor Asymmetry of the Nucleon Sea and the Five-Quark Components of the Nucleons

The existence of the five-quark Fock states for the intrinsic charm quark in the nucleons was suggested some time ago, but conclusive evidence is still lacking. We generalize the previous theoretical approach to the light-quark sector and study possible experimental signatures for such five-quark states. In particular, we compare the $\bar d - \bar u$ and $\bar u + \bar d - s -\bar s$ data with the calculations based on the five-quark Fock states. The qualitative agreement between the data and the calculations is interpreted as evidence for the existence of the intrinsic light-quark sea in the nucleons. The probabilities for the $|uudu\bar{u}>$ and $|uudd\bar{d}>$ Fock states are also extracted.

hep-ph↗
arXiv2010

Partonic substructure of nucleons and nuclei with dimuon production

Dimuon production has been studied in a series of fixed-target experiments at Fermilab during the last two decades. Highlights from these experiments, together with recent results from the Fermilab E866 experiment, are presented. Future prospects for studying the parton distributions in the nucleons and nuclei using dimuon production are also discussed.

nucl-ex↗
arXiv2009

Flavor Asymmetry of the Nucleon Sea and W Boson Production

The advantage and feasibility of using $W$-boson production to extract unique information on the flavor asymmetry of the $\bar u$ and $\bar d$ sea-quark distributions in the proton are examined. The $W^+$ and $W^-$ production cross section ratios in $p+p$ collisions are shown to be sensitive to the $\bar d/ \bar u$ ratios, and they are free from charge-symmetry-breaking and nuclear-binding effects. The feasibility for measuring these ratios at the RHIC and LHC proton-proton colliders, as well as the expected sensitivity to the $\bar d/ \bar u$ ratios, are also presented.

nucl-ex↗
arXiv2008

TMDs and Drell-Yan Experiments at Fermilab and J-PARC

The roles of the Drell-Yan experiments in studying the Transverse-Momentum-Dependent (TMD) parton distributions are discussed. Recent results from the Fermilab E866 experiment on the angular distributions of Drell-Yan dimuons in $p+p$ and $p+d$ at 800 GeV/c are presented. These data are compared with the pion-induced Drell-Yan data, and with models which attribute the $\cos 2 ϕ$ azimuthal distribution to the presence of the transverse-momentum-dependent Boer-Mulders structure function $h_1^\perp$. Constraints on the magnitude of the sea-quark $h_1^\perp$ structure functions are obtained. Future prospects for studying the TMDs with Drell-Yan experiments at Fermilab and J-PARC are also discussed.

nucl-ex↗
arXiv2008

Neutron Electric Dipole Moment Experiments

The neutron electric dipole moment (EDM) provides unique information on CP violation and physics beyond the Standard Model. We first review the history of experimental searches for neutron electric dipole moment. The status of future neutron EDM experiments, including experiments using ultra-cold neutrons produced in superfluid helium, will then be presented.

nucl-ex↗
arXiv2003

Flavor Structure of the Nucleon Sea

The recent progress on our understanding of the flavor structure of unpolarized and polarized nucleon sea is reviewed. The large flavor asymmetry between the up and down sea quark distributions is now well established. This asymmetry strongly suggests the importance of the mesonic degrees of freedom in the description of the nucleon sea. The strong connection between the flavor structure and the spin structure of the nucleon sea is emphasized. Possible future measurements for testing various theoretical models are also discussed.

hep-ph↗
arXiv2002

Status of Spin Physics - Experimental Summary

The current status of spin physics experiments, based on talks presented at the Third Circum-Pan-Pacific Symposium on High Energy Spin Physics held in Beijing, 2001, is summarized in this article. Highlights of recent experimental results at SLAC, JLab, and DESY, as well as future plans at these facilities and at RHIC-spin are discussed.

hep-ph↗
arXiv2001

Flavor Asymmetry of Light Quarks in the Nucleon Sea

A surprisingly large asymmetry between the up and down sea quark distributions in the nucleon has been observed in recent deep inelastic scattering and Drell-Yan experiments. This result strongly suggests that the mesonic degrees of freedom play an important role in the description of the parton distributions of the hadronic sea. In this article, we review the current status of our knowledge of the flavor structure of the nucleon sea. The implications of various theoretical models as well as possible future measurements are also discussed.

nucl-ex↗
arXiv2000

Flavor Asymmetry of the Sea Quark Distributions

Recent deep inelastic scattering and Drell-Yan experiments have revealed a surprisingly large asymmetry between the up and down sea quark distributions in the nucleon. In this article, we review the status of the flavor asymmetry of the nucleon sea. The implications of the recent results on various theoretical models as well as possible future measurements are also discussed.

hep-ph↗
arXiv1999

Dileptons from P-Nucleus Collisions

Various QCD tests using recent results from fixed-target dimuon production experiments at Fermilab are discussed. We emphasize that clear evidence for scaling-violation in the Drell-Yan process remains to be established. Further experimental and theoretical work are needed to understand the polarization of the Drell-Yan pairs. The nuclear medium effects for dilepton productions are also discussed. In particular, the energy-loss of partons traversing nuclear medium is deduced from the Drell-Yan nuclear dependence.

hep-ph↗