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 共查询到20条相似文献,搜索用时 46 毫秒
1.
A. W. Thomas 《中国物理 C》2010,34(9):1153-1156
One of the most fascinating challenges facing modern strong interaction physics is to understand the origin of the spin of the nucleon in terms of the spin and orbital angular momentum of the quarks and gluons.We review recent progress on this problem as well as some of the uncertainties associated with state of the art lattice QCD simulations.In particular,we explain the importance of the corrections associated with chiral extrapolation and finite volume corrections,especially for the term B(0) extracted from the appropriate low moment of the deeply virtual Compton scattering amplitude.  相似文献   

2.
G. K. Mallot 《中国物理 C》2010,34(9):1269-1274
The Compass experiment at CERN is studying the nucleon spin structure with a 160 GeV polarized muon beam and polarized targets as well as hadron structure with 190 GeV pion,kaon and proton beams.The paper gives an overview of the results for the helicity and transverse spin structure of the nucleon.A first result from the spectroscopy experiments,the observation of a resonance with exotic J P C = 1-+ quantum numbers at 1660 MeV is also presented.The paper ends with an outlook to future measurements.  相似文献   

3.
G. Pakhlova 《中国物理 C》2010,34(9):1195-1200
We review the recent experimental results on hadron spectroscopy from B-factories focusing on the exotic charmonium-like states.Among them we discuss the X(3872),Y(3940),Z(4430) +,Z(4050) +,Z(4250) + and Y(4140) states found in B-meson decays,the X(3940) and X(4160) states produced in double charmonium production,the Y(4260),Y(4325),Y(4660) and X(4630) states produced with initial-state radiation in e + eannihilation and the X(3915),Y(4350) states observed in two-photon collisions.  相似文献   

4.
I. Uman 《中国物理 C》2010,34(9):1375-1378
The fixed target COMPASS experiment at CERN offers the opportunity to search for exotic mesons and glueball candidates in the light quark sector with unprecedented statistics.Preliminary results from the 2008 data taken with an incoming negative hadron beam (190 GeV/c,mainly pions) on a liquid hydrogen target are presented.New detectors dedicated to hadron beam measurements have been added.These give access to rare neutral and kaonic channels.An amplitude analysis which will allow to fit simultaneously diffractively and/or centrally produced resonances will be described and compared with those used in the CERN WA102 and BNL E852 experiments.  相似文献   

5.
T. Haas 《中国物理 C》2010,34(9):1254-1258
After the end of data taking in 2007,the experiments H1 and ZEUS have entered into an intense phase of data analysis.Recent results of this effort on neutral (NC) and charged current (CC) cross sections at high Q 2,the longitudinal structure function F L,inclusive diffraction,heavy flavour production and on searches for glueballs are presented.Also shown are results of a combined analysis on inclusive NC and CC cross sections performed by H1 and ZEUS using HERA-I data.  相似文献   

6.
We discuss recent progress in extracting the excited meson spectrum and radiative transition form factors from lattice QCD.We mention results in the charmonium sector,including the first lattice QCD calculation of radiative transition rates involving excited charmonium states,highlighting results for high spin and exotic states.We present recent results on a highly excited isovector meson spectrum from dynamical anisotropic lattices.Using carefully constructed operators we show how the continuum spin of extracted states can be reliably identified and confidently extract excited states,states with exotic quantum numbers and states of high spin.This spectrum includes the first spin-four state extracted from lattice QCD.We conclude with some comments on future prospects.  相似文献   

7.
蒋宇  李宁  孙为民  宗红石 《中国物理 C》2010,34(9):1324-1327
In this paper we calculate the equation of state (EOS) of QCD at zero temperature and finite chemical potential by using several models of quark propagators including the Dyson-Schwinger equations (DSEs) model,the hard-dense-loop (HDL) approximation and the quasi-particle model.The results are analyzed and compared with the known results in the literature.  相似文献   

8.
S. Aoki 《中国物理 C》2010,34(9):1236-1240
We report on new attempt to investigate baryon-baryon interactions in lattice QCD.From the Bethe-Salpeter (BS) wave function,we have successfully extracted the nucleon-nucleon (NN) potentials in quenched QCD simulations,which reproduce qualitative features of modern NN potentials.The method has been extended to obtain the tensor potential as well as the central potential and also applied to the hyperonnucleon (YN) interactions,in both quenched and full QCD.  相似文献   

9.
M. Karliner 《中国物理 C》2010,34(9):1191-1194
I discuss several recent highly accurate theoretical predictions for masses of baryons containing the b quark,especially Ωb (ssb) very recently reported by CDF.I also point out an approximate effective supersymmetry between heavy quark baryons and mesons and provide predictions for the magnetic moments of Λc and Λb .Proper treatment of the color-magnetic hyperfine interaction in QCD is crucial for obtaining these results.  相似文献   

10.
The mass pattern of nucleon and Δ resonances is compared with predictions based on quark models,the Skyrme model,AdS/QCD,and the conjecture of chiral symmetry restoration.  相似文献   

11.
刘北江   《中国物理 C》2010,34(9):1303-1306
Light hadron spectroscopy is a powerful tool in hadronic physics.Several recent BES results on hadron spectroscopy are reported in this proceeding,including the confirmation of the enhancement in pp invariant mass in radiative J/ψ decays,the observation of a charged κ ± decaying to K ± π 0 and the measurement of exclusive decays of the χ c0 and χ c2 to π ^0 π^ 0 and ηη.  相似文献   

12.
The scheme-scale ambiguity that has plagued perturbative analysis in QCD remains on obstacle to making precise tests of the theory.Many attempts have been done to resolve the scale ambiguity.In this regard the BLM,EC,PMS and CORGI approaches are more distinct.We try to employ these methods to fix the scale ambiguity at NLO,NNLO and even in more higher order approximations.By optimizing the renormalization scale,there will be a possibility to predicate higher order terms.We present general results for predicted terms at any order,using different optimization methods.Some observable as specific examples will be used to indicate the validity of scale fixing to predicate the higher order terms.  相似文献   

13.
L. Ya. Glozman 《中国物理 C》2010,34(9):1212-1217
We overview two interconnected topics: possible effective restoration of chiral symmetry in highly excited hadrons and possible existence of confined but chirally symmetric matter at low temperatures and high densities.  相似文献   

14.
R. Kwee 《中国物理 C》2010,34(9):1360-1363
One of the first measurements that will be made at the LHC by ATLAS deals with the properties of inelastic collisions,namely the central charged particle density and transverse momentum distributions.Current predictions of these distributions have large uncertainties in the LHC energy range.We describe the ATLAS minimum bias triggers,designed to select all kind of inelastic interactions,and the performance of the track reconstruction software which was adapted to soft particle track reconstruction.The precision with which the minimum bias distributions can be measured with early data is presented and the uncertainties on the inelastic distributions due to trigger bias is discussed.  相似文献   

15.
In this paper we present the non-singlet QCD analysis to determine valence quark distribution up to four loop.We obtain the fractional difference between the 4-loop and the 1-,2and 3-loop presentations of xu v (x,Q^2) and xd v (x,Q^2).  相似文献   

16.
俞伟林   《中国物理 C》2010,34(9):1476-1478
Generalized Parton Distributions (GPDs) provide a way to access total angular momenta of partons and give a multidimensional picture of the nucleon structure.Deeply Virtual Compton Scattering (DVCS) is the most direct exclusive process to study GPDs.Different azimuthal cross-section asymmetries with respect to beam helicity,beam charge,and target polarization have been measured in the HERMES experiment.A recoil detector was installed at HERMES to directly detect the recoil proton.  相似文献   

17.
D. G. Richards 《中国物理 C》2010,34(9):1281-1285
Theoretical and computational advances have enabled not only the masses of the ground states,but also some of the low-lying excited states to be calculated using Lattice Gauge Theory.In this talk,I look at recent progress aimed at understanding the spectrum of baryon excited states,including both baryons composed of the light u and d quarks,and of the heavier quarks.I then describe recent work aimed at understanding the radiative transitions between baryons,and in particular the N-Roper transition.I conclude with the prospects for future calculations.  相似文献   

18.
孙亮   《中国物理 C》2010,34(9):1504-1507
Based on a data sample of 384 million BB pairs collected with the BABAR detector at the PEP-Ⅱ asymmetric e + e  ̄ storage ring,we measure branching fractions,direct CP,isospin and lepton-flavor asymmetries for the rare decays B → K (*) l + l ̄ in two di-lepton mass bins above and below the J/ψ resonance.For the B → K* l + l ̄ decay,we also measure the K* longitudinal polarization fraction and the di-lepton forwardbackward asymmetry.  相似文献   

19.
秦猛  李延标  白忠  林上金  刘卫 《中国物理 C》2010,34(11):1693-1695
Ground state entanglement and thermal entanglement of a two-qubit Heisenberg XXZ chain in the presence of the different Dzyaloshinski-Moriya interaction and inhomogeneous magnetic field are investigated.By the concept of concurrence,we find that the inhomogeneity of the magnetic field may make entanglement last for a long time and the critical temperature is dependent on Jz and b.The entanglement can be increased by increasing the temperature in some cases.We also find that the x-component parameter Dx has a higher critical temperature and more entanglement for a certain condition than the z-component parameter Dz.  相似文献   

20.
The measurement of parity-violating (PV) observables in few-nucleon system can shed light on our current understanding of the weak interaction between nucleons.Theoretical models describe the nucleonnucleon weak interaction at low energies use a series of undetermined parameters.Two parity violating measurements have been considered: the capture of polarized slow neutrons on hydrogen (n + p → d + γ) at Los Alamos National Laboratory for first phase and Oka Ridge National Laboratory for second phase and the helicity dependence of the deuteron photodisintegration cross section using circularly polarized photons (γ + d → n + p) at Shanghai Institute of Applied Physics.The goal of both experiments is to constraint the weak meson-nucleon couplings to a precision of 1 ×10^-8 .The introduction of both experiments is presented.  相似文献   

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