Q2-Dependence of the Bjorken Sum Rule in the Resonance Region

Q²-evolution of the Bjorken sum rule in the resonance region is studied. The roles of the Roper resonance N^* (1440) estimated by the constituent quark model and by the hybrid model are stressed. Moreover, the Q²- dependence of the Gerasimov-Drell-Hearn sum rule contributed by the resonances is also discussed.     

Gerasimov–Drell–Hearn求和规则的Q2依赖性质

在组分夸克模型中重子共振态的光子激发下,通过数值计算核子上光子总吸收截面σ_1/2和σ_3/2,检验了Gerasimov–Drell–Heam(GDH)求和规则.这种计算包括了总计17个低激发的、非奇异重子共振态.发现纵横相干截面在随Q²变化的求和规则研究中扮演了重要角色.结果显示在94%可信度上这些共振态使GDH求和规则饱和.特别是在Q²=0和小Q²的区域,主要是共振态P₃₃(1232)激发使求和规则饱和.在Q²=1.0GeV²以下,GDH积分有一个很强的Q²依赖性质,且在Q²=0.3GeV²附近变号.由于共振态贡献的迅速下降,当Q²>1.0GeV²时,GDH积分对Q²依赖变弱.     

Q 2-Dependence of the Drell-Hearn-Gerasimov integral

The energy and four-momentum (Q²) dependence of the photo-absorption cross section on the proton is calculated for helicity у/2 and х/2 states. An effective Lagrangian model is used, formulated in terms of meson and baryon degrees of freedom, which obeys crossing symmetry, unitarity, Lorentz and gauge invariance. The difference in the cross sections for the two helicity states, the Drell-Hearn-Gerasimov integral I_DHG(Q²), is evaluated at different Q². We find that at small momentum transfer the absolute value of I_DHG(Q²) first increases to reach a maximum at Q² , 0.05 GeV² before decreasing at higher Q².     

πNN过程对Gottfried求和规则破坏的贡献

指出在计算πNN过程对核子结构函数的贡献时,将反冲核子视为物理核子更为合理.对Gottfried求和规则破坏、对质子中海夸克分布u和d不对称u(x)–d(x)等方面的贡献给出了详细的计算,与已有实验进行比较.结果表明π介子交换不是导致这一破坏以及影响核子结构函数的效应的惟一来源.     

Gottfried Sum Rule in QCD Nonsinglet Analysis of DIS Fixed-Target Data

Deep-inelastic-scattering data from fixed-target experiments on the structure function F₂ were analyzed in the valence-quark approximation at the next-to-next-to-leading-order accuracy level in the strong-coupling constant. In this analysis, parton distributions were parametrized by employing information from the Gottfried sum rule. The strong-coupling constant was found to be α _s (M²_Z) = 0.1180 ± 0.0020 (total expt. error), which is in perfect agreement with the world-averaged value from an updated Particle Data Group (PDG) report, α^PDG _s (M²_Z) = 0.1181 ± 0.0011. Also, the value of 〈x〉_u?d = 0.187 ± 0.021 found for the second moment of the difference in the u- and d-quark distributions complies very well with the most recent lattice result 〈x〉^LATTICE_u?d = 0.208 ± 0.024.     

Fusion Effect in Q2 Evolution Equation

A momentum-conserved Q₂ evolution equation is obtained after the fusion process is included into the Altarelli-Parisi splitting-function argument.     

xF3(x,Q2) Structure Function and Gross-Llewellyn Smith Sum Rule with Nuclear Effect and Higher Twist Correction

We present an analysis of the xF₃(x,Q²) structure function and Gross-Llewellyn Smith(GLS) sum rule taking into account the nuclear effects and higher twist correction. This analysis is based on the results presented in[N.M. Nath, et al., Indian J. Phys. 90 (2016) 117]. The corrections due to nuclear effects predicted in several earlier analysis are incorporated to our results of xF₃(x,Q²) structure function and GLS sum rule for free nucleon, corrected upto next-next-to-leading order (NNLO) perturbative order and calculate the nuclear structure function as well as sum rule for nuclei. In addition, by means of a simple model we have extracted the higher twist contributions to the non-singlet structure function xF₃(x,Q²) and GLS sum rule in NNLO perturbative orders and then incorporated them to our results. Our NNLO results along with nuclear effect and higher twist corrections are observed to be compatible with corresponding experimental data and other phenomenological analysis.     

Nonperturbative calculation of the 2-photon transverse resonance in radio-frequency spectroscopy

A new analytic nonperturbative approximation procedure is used to calculate the frequency shift of the first transverse resonance in the 2-level atomic system. The accuracy of our result as tested for the vanishing constant magnetic field H₀ against the known exact result is within 1 ppm.     

Gottfried sum rule and the shape ofF 2 ⌍ -F 2 ⌍

The recent experimental determination of the Gottfried sum rule of deep inelastic scattering provides strong evidence that SU(2) flavor symmetry is broken by the sea quark distributions of the nucleon. Two mechanisms have been suggested to explain the data: Pauli blocking and non-perturbative contributions to the sea arising from the pion cloud surrounding the nucleon. We investigate the effects of these two mechanisms on several standard parametrizations of the quark distribution functions and find that each mechanism has different effects on the shapes of these distribution functions. The best agreement between the experimental data and the modified quark distributions occurs when both mechanisms are taken into account using a softπNN form factor and a small Pauli correction.     

Nonperturbative deformation of D-brane states by the world sheet noncommutativity

By introducing the noncommutativity in the world sheet, we discuss a modification of the D-brane states in the closed string theory. In particular we show how the world sheet noncommutativity induces a nonperturbative effect to the D-brane states.     

Nontrivial Effect of Time-Varying Migration on the Three Species Prey-Predator System

Migration is ubiquitous in ecosystem and often plays an important role in biological diversity. In this work,by introducing a time-varying migration rate associated with the difference of subpopulation density into a prey, we study the Hopf bifurcation and the critical phenomenon of predator extinction of the three species prey-predator system,which consists of a predator, a prey and a mobile prey. It is found that the system with migration exhibits richer dynamic behaviors than that without migration, including two Hopf bifurcations and two limit cycles. Interestingly,the parameters of migration have a drastically influence on the critical point of predator extinction, determining the coexistence of species. Moreover, the population evolution dynamics of one-dimensional multiple prey-predator system are also discussed.     

{Q\bar{s}}{\bar{Q}(') s} Molecular States in QCD Sum Rules

We systematically investigate the mass spectra of {Q\bar{s}}{bar{Q}^(')s}molecular states in the framework of QCD sum rules. The interpolating currents representing the molecular states are proposed. Technically, contributions of the operators up to dimension six are included in operator product expansion (OPE). The masses for molecular states with various{Q\bar{s}} {\bar{Q}^(')s} configurations are presented. The result 4.36±0.08 GeV for the D^*_s\bar{D}^*_s0 molecular state is consistent withthe mass 4350^+4.6_-5.1 ± 0.7 MeV of the newly observed X(4350), which could support X(4350) interpreted as a D^*_s\bar{D^}*_s0 molecular state.     

Nonperturbative heavy-quark diffusion in the quark-gluon plasma

We evaluate heavy-quark (HQ) transport properties in a quark-gluon plasma (QGP) within a Brueckner many-body scheme employing interaction potentials extracted from thermal lattice QCD. The in-medium T matrices for elastic charm- and bottom-quark scattering off light quarks in the QGP are dominated by attractive meson and diquark channels which support resonance states up to temperatures of ~1.5T(c). The resulting drag coefficient increases with decreasing temperature, contrary to expectations based on perturbative QCD scattering. Employing relativistic Langevin simulations we compute HQ spectra and elliptic flow in sqrt[s(NN)]=200 GeV Au-Au collisions. A good agreement with electron decay data supports our nonperturbative computation of HQ diffusion, indicative for a strongly coupled QGP.     

Nonperturbative dynamics in the color-magnetic QCD vacuum

In the deconfinement phase of QCD, quarks and gluons interact with the dense stochastic color-magnetic vacuum. We consider the dynamics of quarks in this deconfinement phase using the field correlators method and derive an effective nonperturbative interquark potential, in addition to the usual perturbative short-range interaction. We find the resulting angular-momentum-dependent interaction to be attractive enough to maintain bound states and, for light quarks (and gluons), to cause emission of quark and gluon pairs. Possible consequences for the strong-interacting quark-gluon plasma are briefly discussed. The text was submitted by the authors in English.     

Passive Q switching by heated CO2

Passive Q switching using heated CO₂ as a saturable absorber was observed. A kinetic model previously proposed is used to interpret this phenomenon. Our study reveals the important role of rotational and vibrational relaxation mechanisms.     

{Qs}{Q（＇）s} Molecular States in QCD Sum Rules

We systematically investigate the mass spectra of {Qs}{Q（＇）s} molecular states in the framework of QCD sum rules. The interpolating currents representing the molecular states are proposed. Technically, contributions of the operators up to dimension six are included in operator product expansion （OPE）. The masses for molecular states with various {Qs}{Q（＇）s} configurations are presented. The result 4.36 ± 0.08 Ge V for theDs＊ Ds0- ＊ molecular state is consistent with the mass 4350＋4.6 -5.1± 0.7 MeV of the newly observed X（4350）, which could support X（4350） interpreted as a D＊D＊so molecular state.     

Nonperturbative QCD thermodynamics in the external magnetic field

The thermodynamics of quarks and gluons strongly depends on the vacuum colormagnetic field, which grows with the temperature T, so that spatial string tension \(\sigma _s =\mathrm{const}~ g^4 (T) T^2\). We investigate below what happens when one imposes in addition constant magnetic field and discover remarkable structure of the resulting thermodynamic potential.