共查询到20条相似文献,搜索用时 31 毫秒
1.
Based on QCD sum rules we explore the consequences of a scenario for the ρ meson, where the chiral symmetry breaking condensates are set to zero whereas the chirally symmetric condensates remain at their vacuum values. This clean-cut scenario causes a lowering of the ρ spectral moment by about 120 MeV. The complementarity of mass shift and broadening is discussed. A simple parametrization of the ρ spectral function leads to a width of about 280 MeV if no shift of the peak position is assumed. 相似文献
2.
K. Morita 《Indian Journal of Physics》2011,85(6):825-829
We study behavior of J/ψ in hot gluonic matter using QCD sum rules. Taking into account temperature dependences of the gluon condensates extracted
from lattice thermodynamics for the pure SU(3) system, we find that the mass and width of J/ψ exhibit rapid change across the critical temperature. 相似文献
3.
Nonperturbative QCD vacuum with two light quarks at finite temperature was studied in a hadron resonance-gas model. Temperature dependences of the quark and gluon condensates in the confined phase were obtained. It is shown that the quark condensate and one-half (chromoelectric component) of the gluon condensate are evaporated at the same temperature corresponding to the quark-hadron phase transition. With allowance for the temperature shift of hadron masses, the critical temperature was found to be T c ?190 MeV. 相似文献
4.
We discuss how the spectral changes of quarkonia at T
c can reflect the ‘critical’ behaviour of QCD phase transition. Starting from the temperature dependencies of the energy density
and pressure from lattice QCD calculation, we extract the temperature dependencies of the scalar and spin-2 gluon condensates
near T
c. We also parametrize these changes into the electric and magnetic condensate near T
c. While the magnetic condensate hardly changes across T
c, we find that the electric condensate increases abruptly above T
c. Similar abrupt change is also seen in the scalar condensate. Using the QCD second-order Stark effect and QCD sum rules,
we show that these sudden changes induce equally abrupt changes in the mass and width of J/ψ, both of which are larger than 100 MeV at slightly above T
c.
相似文献
5.
We study the vector meson electro-production off the proton in a QCD inspired model.A calculation of the differential cross section is performed for the J/ψ,φ meson off the proton.The theoretical results are consistent with the experimental data,and remind us to consider the contribution from the tensor glueball and Odderon to the differential cross section.Since gluons interact among themselves via self-interaction,the gluons can form a glueball with quantum numbers IG,JPC =0+,2++,with a decay width Γt =100 MeV and mass of mG = 2.23 GeV.The three gluons can form a three gluon color bound state with charge conjugation quantum number C =-1.This study is quite important to verify the validity of QCD and to search for new particles(tensor glueball and Odderon) as well as quest for new physics. 相似文献
6.
G. V. Efimov S. N. Nedelko 《The European Physical Journal C - Particles and Fields》1998,1(1-2):343-350
It is shown that an (anti-) self-dual homogeneous vacuum gluon field appears in a natural way within the problem of calculation of the QCD partition function in the form of Euclidean functional integral with periodic boundary conditions. There is no violation of cluster property within this formulation, nor are parity, color and rotational symmetries broken explicitly. The massless limit of the product of the quark masses and condensates, $m_f \left\langle {\bar \psi _f \psi _f } \right\rangle $ , is calculated to all loop orders. This quantity does not vanish and is proportional to the gluon condensate appearing due to the nonzero strength of the vacuum gluon field. We conclude that the gluon condensate can be considered as an order parameter both for confinement and chiral symmetry breaking. 相似文献
7.
We study vacuum of QCD in this work. The structure of non-local
quark vacuum condensate, values of various local quark and gluon
vacuum condensates, quark-gluon mixed vacuum condensate, quark and
gluon virtuality in QCD vacuum state, quark dynamical mass and
susceptibility of QCD vacuum state to external field are predicted by use of the solutions of Dyson-Schwinger equations in “rainbow”
approximation with a modeling gluon propagator and three different
sets of quark-quark interaction parameters. Our theoretical
predictions are in good agreement with the correspondent empirical
values used widely in literature, and many other theoretical
calculations. The quark propagator and self-energy functions are
also obtained from the numerical solutions of Dyson-Schwinger
equations. This work is centrally important for studying
non-perturbative QCD, and has many important applications both in
particle and nuclear physics. 相似文献
8.
Ablikim M Bai JZ Ban Y Bian JG Cai X Chang JF Chen HF Chen HS Chen HX Chen JC Chen J Chen J Chen ML Chen YB Chi SP Chu YP Cui XZ Dai HL Dai YS Deng ZY Dong LY Du SX Du ZZ Fang J Fang SS Fu CD Fu HY Gao CS Gao YN Gong MY Gong WX Gu SD Guo YN Guo YQ Guo ZJ Harris FA He KL He M He X Heng YK Hu HM Hu T Huang GS Huang L Huang XP Ji XB Jia QY Jiang CH Jiang XS Jin DP Jin S Jin Y Lai YF Li F Li G Li HH Li J Li JC Li QJ Li RB Li RY Li SM Li WG Li XL Li XQ Li XS Liang YF Liao HB Liu CX Liu F Liu F 《Physical review letters》2004,93(11):112002
An enhancement near the m(p)+M(Lambda) mass threshold is observed in the combined pLambda and pLambda invariant-mass spectrum from J/psi-->pK(-)Lambda;+c.c. decays. It can be fit with an S-wave Breit-Wigner resonance with a mass m=2075+/-12(stat)+/-5(syst) MeV and a width of Gamma=90+/-35(stat)+/-9(syst) MeV; it can also be fit with a P-wave Breit-Wigner resonance. Evidence for a similar enhancement is also observed in psi(')-->pK(-)Lambda;+c.c. decays. The analysis is based on samples of 5.8x10(7)J/psi and 1.4x10(7)psi(') decays accumulated in the BES II detector at the Beijing Electron-Positron Collider. 相似文献
9.
Ablikim M Bai JZ Ban Y Bian JG Cai X Chen HF Chen HS Chen HX Chen JC Chen J Chen YB Chi SP Chu YP Cui XZ Dai YS Deng ZY Dong LY Dong QF Du SX Du ZZ Fang J Fang SS Fu CD Gao CS Gao YN Gu SD Gu YT Guo YN Guo YQ Guo ZJ Harris FA He KL He M Heng YK Hu HM Hu T Huang GS Huang XP Huang XT Ji XB Jiang XS Jiao JB Jin DP Jin S Jin Y Lai YF Li G Li HB Li HH Li J Li RY Li SM Li WD Li WG Li XL Li XQ Li YL Liang YF Liao HB Liu CX Liu F Liu F Liu HH Liu HM Liu J Liu JB Liu JP Liu RG Liu ZA Lu F Lu GR Lu HJ 《Physical review letters》2005,95(26):262001
The decay channel J/psi --> gamma(pi)(+)pi(-)eta is analyzed using a sample of 5.8 x 10(7) J/psi events collected with the BESII detector. A resonance, the Chi(1835), is observed in the pi(+)pi(-)eta invariant-mass spectrum with a statistical significance of 7.7 sigma. A fit with a Breit-Wigner function yields a mass M = 1833.7 +/- 6.1(stat) +/- 2.7(syst) MeV/c(2), a width Tau = 67.7 +/- 20.3(stat) +/- 7.7(syst) MeV/c(2), and a product branching fraction B(J/psi --> gammaChi) . B(Chi --> pi(+)pi(-)eta) = [2.2 +/- 0.4(stat) +/- 0.4(syst)] x 10(-4). The mass and width of the Chi(1835) are not compatible with any known meson resonance. Its properties are consistent with expectations for the state that produces the strong pp mass threshold enhancement observed in the J/psi --> gammapp process at BESII. 相似文献
10.
Jue-ping LIU 《理论物理通讯》1987,8(2):239-253
The QCD sum rules for the proton. mass,the n-p mass ratio and the optimal observation point are analysed, which can greatly improve the precision of the theoretical results. If we take = and mu/(mu+md)-=0.35 which agree with the values from SVZ and current algebra[1,2],we obtain Mp=935.86MeV and Mp/Mn=0.99871 which coincide quite well with experimental values.The isospin behavior of light quarks is investigated. It shows that the isospin symmetry of the light quark condensates is very good up to the low-energy region (about 500MeV),and that the n-p mass difference can be originated from the u-and d-quark mass differences. 相似文献
11.
We study the vacuum structure in QCD in a nonperturbative manner using a variational approach with gluon condensates. We show
that in Coulomb gauge as the coupling becomes moderately strong, the perturbative vacuum of QCD becomes unstable leading to
gluon condensates and a gauge dependent effective mass for the gluons related to the gauge independent value of 〈vac‖G
μν
a
G
aμν‖vac〉 of Shifmanet al. 相似文献
12.
Alejandro Cabo Montes de Oca 《The European Physical Journal C - Particles and Fields》2008,55(1):85-93
The renormalization scheme for the Wick expansion of a modified version of the perturbative QCD introduced in previous works
is discussed. Massless QCD is considered by implementing the usual multiplicative scaling of the gluon and quark wave functions
and vertices. However, also massive quark and gluon counterterms are allowed in this massless theory since the condensates
are expected to generate masses. A natural set of expansion parameters of the physical quantities is introduced: the coupling
itself and the two masses mq and mg associated to quarks and gluons, respectively. This procedure allows one to implement a dimensional transmutation effect
through these new mass scales. A general expression for the new generating functional in terms of the mass parameters mq and mg is obtained in terms of integrals over arbitrary but constant gluon or quark fields in each case. Further, the one loop potential
is evaluated in more detail in the case when only the quark condensate is retained. This lowest order result again indicates
the dynamical generation of quark condensates in the vacuum. 相似文献
13.
With the help of the Ward-Takahashi identities associated with a specific non linear chiral transformation of the quark fields we show, in the framework of massless QCD, that in addition to scale invariance breaking gluon condensation implies dynamical chiral symmetry breaking, that is to say the appearance of a non vanishing quark condensate. Moreover the dynamically generated quark mass is directly connected to the quark and gluon condensates. 相似文献
14.
We study properties of a gluon plasma above the critical temperature Tc in a generalized quasiparticle approach with a Lorentz spectral function. The model parameters are determined by a fit of the entropy s to lattice QCD data. The effective degrees of freedom are found to be rather heavy and of a sizable width. With the spectral width being closely related to the interaction rate, we find a large effective cross section, which is comparable to the typical distance squared of the quasiparticles. This suggests that the system should be viewed as a liquid as also indicated by an estimate of the plasma parameter Gamma. Furthermore, within the quasiparticle approach we find a very low viscosity to entropy ratio, eta/s approximately 0.2 for T > 1.05 Tc, supporting the recent conjecture of an almost ideal quark-gluon liquid seen at RHIC. 相似文献
15.
We study the properties of mixed quark–gluon condensate at finite temperature and chemical potential in the framework of global color symmetry model. In comparing with the quark condensate, we confirm that both of these condensates give the same information about chiral phase transition. We also find that the ratio of these two condensates is insensitive to the temperature T and the chemical potential μ, which supports the conclusion obtained recently by the authors using quenched lattice QCD. 相似文献
16.
Frédéric Jugeau 《中国物理C(英文版)》2010,34(9)
We investigate the AdS/QCD duality for the two-point correlation functions of the lowest dimension scalar meson and scalar glueball operators,in the case of the Soft Wall holographic model of QCD.Masses and decay constants as well as gluon condensates are compared to their QCD estimates.In particular,the role of the boundary conditions for the bulk-to-boundary propagators is emphasized. 相似文献
17.
Aubert B Barate R Boutigny D Couderc F Karyotakis Y Lees JP Poireau V Tisserand V Zghiche A Grauges E Palano A Pappagallo M Pompili A Chen JC Qi ND Rong G Wang P Zhu YS Eigen G Ofte I Stugu B Abrams GS Battaglia M Breon AB Brown DN Button-Shafer J Cahn RN Charles E Day CT Gill MS Gritsan AV Groysman Y Jacobsen RG Kadel RW Kadyk J Kerth LT Kolomensky YG Kukartsev G Lynch G Mir LM Oddone PJ Orimoto TJ Pripstein M Roe NA Ronan MT Wenzel WA Barrett M Ford KE Harrison TJ Hart AJ Hawkes CM Morgan SE 《Physical review letters》2005,95(14):142001
We study initial-state radiation events, e+ e- --> gammaISR pi+ pi- J/psi, with data collected with the BABAR detector. We observe an accumulation of events near 4.26 GeV/c2 in the invariant-mass spectrum of pi+ pi- J/psi. Fits to the mass spectrum indicate that a broad resonance with a mass of about 4.26 GeV/c2 is required to describe the observed structure. The presence of additional narrow resonances cannot be excluded. The fitted width of the broad resonance is 50 to 90 MeV/c2, depending on the fit hypothesis. 相似文献
18.
The problem of obtaining the Regge-like behaviour for meson mass spectrum in the hard-wall AdS/QCD models is addressed. We show that the problem can be solved by a simple incorporation of the effects of local vacuum condensates into such models. The slope of trajectories turns out to be determined by the local condensate of dimension 2 that is absent in the standard Operator Product Expansion. This pitfall, however, can be escaped by means of physically plausible modification of boundary conditions for the holographic fields corresponding to the usual gluon condensate, the latter then determines the slope. 相似文献
19.
Bai JZ Ban Y Bian JG Cai X Chang JF Chen HF Chen HS Chen J Chen J Chen JC Chen YB Chi SP Chu YP Cui XZ Dai YM Dai YS Dong LY Du SX Du ZZ Dunwoodie W Fang J Fang SS Fu CD Fu HY Fu LP Gao CS Gao ML Gao YN Gong MY Gong WX Gu SD Guo YN Guo YQ Guo ZJ Han SW Harris FA He J He KL He M He X Heng YK Hong T Hu HM Hu T Huang GS Huang L Huang XP Izen JM Ji XB Jiang CH Jiang XS Jin DP Jin S Jin Y Jones BD Ke ZJ Kong D Lai YF Li F Li G Li HH Li J Li JC Li K Li QJ Li RB Li RY Li W Li WG Li XQ Li XS Liu CF 《Physical review letters》2003,91(2):022001
We observe a narrow enhancement near 2m(p) in the invariant mass spectrum of pp pairs from radiative J/psi-->gammapp decays. No similar structure is seen in J/psi-->pi(0)pp decays. The results are based on an analysis of a 58 x 10(6) event sample of J/psi decays accumulated with the BESII detector at the Beijing electron-positron collider. The enhancement can be fit with either an S- or P-wave Breit-Wigner resonance function. In the case of the S-wave fit, the peak mass is below 2m(p) at M=1859(+3)(-10) (stat)+5-25(syst) MeV/c(2) and the total width is Gamma<30 MeV/c(2) at the 90% confidence level. These mass and width values are not consistent with the properties of any known particle. 相似文献
20.
I. Caprini 《Czechoslovak Journal of Physics》1991,41(1):12-19
A new method for the determination of the QCD condensates from low-energy hadronic data is proposed. It generalizes the usual QCD finite-energy sum rules, taking into account explicitely the truncation error of the high-energy QCD expansion. The method is applied to the e+e– annihilation intoI= 1 hadrons, indicating a rather large domain for the values of the gluon and four quark condensates. 相似文献