The quantum mechanics of bound states with discrete energy levels is well understood. The quantum mechanics of scattering processes is also well understood. However, the quantum mechanics of moving bound states is sti...The quantum mechanics of bound states with discrete energy levels is well understood. The quantum mechanics of scattering processes is also well understood. However, the quantum mechanics of moving bound states is still debatable. When it is at rest, the space-like separation between the constituent particles is the primary variable. When the bound state moves, this space-like separation picks up the time-like separation. The time-separation is not a measurable variable in the present form of quantum mechanics. The only way to deal with this un-observable variable is to treat it statistically. This leads to rise of the statistical variables such entropy and temperature. Paul A. M. Dirac made efforts to construct bound-state wave functions in Einstein’s Lorentz-covariant world. In 1927, he noted that the c-number time-energy relation should be incorporated in the relativistic world. In 1945, he constructed four-dimensional oscillator wave functions with one time coordinate in addition to the three-dimensional space. In 1949, Dirac introduced the light-cone coordinate system for Lorentz transformations. It is then possible to integrate these contributions made by Dirac to construct the Lorentz-covariant harmonic oscillator wave functions. This oscillator system can explain the proton as a bound state of the quarks when it is at rest, and explain the Feynman’s parton picture when it moves with a speed close to that of light. While the un-measurable time-like separation becomes equal to the space-like separation at this speed, the statistical variables become prominent. The entropy and the temperature of this covariant harmonic oscillator are calculated. It is shown that they rise rapidly as the proton speed approaches that of light.展开更多
Study of nucleons charge radii and electromagnetic form factors are expected to provide valuable information about the distribution of electric charge within the fundamental particles in nucleon’s inner structure. In...Study of nucleons charge radii and electromagnetic form factors are expected to provide valuable information about the distribution of electric charge within the fundamental particles in nucleon’s inner structure. In the recent years, dramatic progress has been made in the understanding of the nucleon structure and the precision of its partonic content, due to the vast theoretical progress, and the availability of new high precision measurements. Here in this article, we present a simple model for the charge structure of the nucleons and the most available sets of the structure functions to calculate the mean square charge radius N2> for both protons and neutrons. Our results are consistent with the modern understanding of the nucleons as well as recent experimental data. We discuss the origin of the sign rN2> for both proton and neutron.展开更多
Results are presented from the Hermes experiment which uses semi-inclusive deep inelastic lepton scattering to study the flavor structure of the nucleon.Data have been accumulated for pion and kaon double spin asymmet...Results are presented from the Hermes experiment which uses semi-inclusive deep inelastic lepton scattering to study the flavor structure of the nucleon.Data have been accumulated for pion and kaon double spin asymmetries,single-spin azimuthal asymmetries for meson electroproduction,deep virtual Compton scattering （DVCS）,and meson multiplicities.These results provide information on the properties of the strange sea in the proton,constraints on transverse momentum dependent quark parton distributions,and demonstrate the promise of DVCS for isolating the total angular momentum carried by the quarks in the proton.展开更多
We study the medium modified fragmentation function in high-energy heavy-ion collisions. We show that the ACSX and QW formalisms are equivalent to each other in the high-Q2 limit in both theoretical and numerical aspe...We study the medium modified fragmentation function in high-energy heavy-ion collisions. We show that the ACSX and QW formalisms are equivalent to each other in the high-Q2 limit in both theoretical and numerical aspects.展开更多
The recent measurement of the differential γ ＋ c-jet cross section, performed at the Tevatron collider in Run II by the D0 collaboration, is studied in a next-to-leading order（NLO） global QCD analysis to assess it...The recent measurement of the differential γ ＋ c-jet cross section, performed at the Tevatron collider in Run II by the D0 collaboration, is studied in a next-to-leading order（NLO） global QCD analysis to assess its impact on the proton parton distribution functions（PDFs）. We show that these data lead to a significant change in the gluon and charm quark distributions. We demonstrate also that there is an inconsistency between the new high precision HERA I＋II combined data and Tevatron measurement. Moreover, in this study we investigate the impact of older EMC measurements of charm structure function F_c^2 on the PDFs and compare the results with those from the analysis of Tevatron data. We show that both of them have the same impact on the PDFs, and thus can be recognized as the same evidence for the inefficiency of perturbative QCD in dealing with charm production in some kinematic regions.展开更多
文摘The quantum mechanics of bound states with discrete energy levels is well understood. The quantum mechanics of scattering processes is also well understood. However, the quantum mechanics of moving bound states is still debatable. When it is at rest, the space-like separation between the constituent particles is the primary variable. When the bound state moves, this space-like separation picks up the time-like separation. The time-separation is not a measurable variable in the present form of quantum mechanics. The only way to deal with this un-observable variable is to treat it statistically. This leads to rise of the statistical variables such entropy and temperature. Paul A. M. Dirac made efforts to construct bound-state wave functions in Einstein’s Lorentz-covariant world. In 1927, he noted that the c-number time-energy relation should be incorporated in the relativistic world. In 1945, he constructed four-dimensional oscillator wave functions with one time coordinate in addition to the three-dimensional space. In 1949, Dirac introduced the light-cone coordinate system for Lorentz transformations. It is then possible to integrate these contributions made by Dirac to construct the Lorentz-covariant harmonic oscillator wave functions. This oscillator system can explain the proton as a bound state of the quarks when it is at rest, and explain the Feynman’s parton picture when it moves with a speed close to that of light. While the un-measurable time-like separation becomes equal to the space-like separation at this speed, the statistical variables become prominent. The entropy and the temperature of this covariant harmonic oscillator are calculated. It is shown that they rise rapidly as the proton speed approaches that of light.
文摘Study of nucleons charge radii and electromagnetic form factors are expected to provide valuable information about the distribution of electric charge within the fundamental particles in nucleon’s inner structure. In the recent years, dramatic progress has been made in the understanding of the nucleon structure and the precision of its partonic content, due to the vast theoretical progress, and the availability of new high precision measurements. Here in this article, we present a simple model for the charge structure of the nucleons and the most available sets of the structure functions to calculate the mean square charge radius N2> for both protons and neutrons. Our results are consistent with the modern understanding of the nucleons as well as recent experimental data. We discuss the origin of the sign rN2> for both proton and neutron.
文摘Results are presented from the Hermes experiment which uses semi-inclusive deep inelastic lepton scattering to study the flavor structure of the nucleon.Data have been accumulated for pion and kaon double spin asymmetries,single-spin azimuthal asymmetries for meson electroproduction,deep virtual Compton scattering （DVCS）,and meson multiplicities.These results provide information on the properties of the strange sea in the proton,constraints on transverse momentum dependent quark parton distributions,and demonstrate the promise of DVCS for isolating the total angular momentum carried by the quarks in the proton.
基金Supported by NSFC (10875051,11020101060)Program of Science and Technology Department of Hubei Province(2009BFA010)CCNU09C01002 (Key Grant)
文摘We study the medium modified fragmentation function in high-energy heavy-ion collisions. We show that the ACSX and QW formalisms are equivalent to each other in the high-Q2 limit in both theoretical and numerical aspects.
文摘The recent measurement of the differential γ ＋ c-jet cross section, performed at the Tevatron collider in Run II by the D0 collaboration, is studied in a next-to-leading order（NLO） global QCD analysis to assess its impact on the proton parton distribution functions（PDFs）. We show that these data lead to a significant change in the gluon and charm quark distributions. We demonstrate also that there is an inconsistency between the new high precision HERA I＋II combined data and Tevatron measurement. Moreover, in this study we investigate the impact of older EMC measurements of charm structure function F_c^2 on the PDFs and compare the results with those from the analysis of Tevatron data. We show that both of them have the same impact on the PDFs, and thus can be recognized as the same evidence for the inefficiency of perturbative QCD in dealing with charm production in some kinematic regions.
