共查询到20条相似文献,搜索用时 154 毫秒
1.
El?en Veli Veliev Gül?ah Kaya 《The European Physical Journal C - Particles and Fields》2009,63(1):87-91
In the present work, D
s
and B
s
meson parameters are investigated in the framework of thermal QCD sum rules. The temperature dependences of the mass and
the leptonic decay constants are investigated by using Borel transform sum rules and Hilbert moment sum rules. To increase
the sensitivity, the vacuum contributions are subtracted from the thermal expressions and the temperature dependences of the
leptonic decay constants and meson masses are studied. 相似文献
2.
TheW boson pair production by electron and positron of same helicity is computed. The restrictions due to the tree unitarity are exhibited in three sum rules and we have shown how the gauge theories satisfy the sum rules. A simple way to isolate heavy lepton contributions is presented. 相似文献
3.
M.A. Braun E.G. Ferreiro F. del Moral C. Pajares 《The European Physical Journal C - Particles and Fields》2002,25(2):249-257
Calculations of the production rate of particles with x > 1 in nuclear collisions due to the interaction of colour strings are presented. Momentum and colour sum rules are used
to determine the fragmentation functions of fused strings. Mechanisms of the string interaction are considered with total
and partial overlapping in the transverse plane. The results reveal a strong dependence of the chosen mechanism. In the percolation
scenario with partial overlapping the x-dependence of the production rates agrees well with the existing data. The magnitude of the rates for production is in agreement with experiment. However the rates for the protons are substantially below the data.
Received: 28 November 2001 / Revised version: 15 May 2002 / Published online: 12 July 2002 相似文献
4.
The
model for inclusive processes is reformulated to consider the production of heavy flavours (c, b andt) and higher order flavour exchange effects. Predictions are made in terms of sum rules and inequalities for various inclusive
cross-sections. Plausible parametrization of flavour symmetry breaking is also suggested. 相似文献
5.
L. Šamaj 《Journal of statistical physics》2007,128(6):1415-1428
In the equilibrium statistical mechanics of classical Coulomb fluids, the long-range tail of the Coulomb potential gives rise
to the Stillinger–Lovett sum rules for the charge correlation functions. For the jellium model of mobile particles of charge
q immersed in a neutralizing background, the Stillinger–Lovett sum rules give the charge and second moment of the screening
cloud around a particle of the jellium. In this paper, we generalize these sum rules to the screening cloud induced around
a pointlike guest charge Zq immersed in the bulk interior of the 2D jellium with the coupling constant Γ=β
q
2 (β is the inverse temperature), in the whole region of the thermodynamic stability of the guest charge amplitude Z>−2/Γ. The derivation is based on a mapping technique of the 2D jellium at the coupling Γ = (even positive integer) onto a
discrete 1D anticommuting-field theory; we assume that the final results remain valid for all real values of Γ corresponding
to the fluid regime. The generalized sum rules reproduce for arbitrary coupling Γ the standard Z=1 and the trivial Z=0 results. They are also checked in the Debye–Hückel limit Γ→0 and at the free-fermion point Γ=2. The generalized second-moment
sum rule provides some exact information about possible sign oscillations of the induced charge density in space. 相似文献
6.
S. Faller A. Khodjamirian Ch. Klein Th. Mannel 《The European Physical Journal C - Particles and Fields》2009,60(4):603-615
We derive new QCD sum rules for B→D and B→D
* form factors. The underlying correlation functions are expanded near the light-cone in terms of B-meson distribution amplitudes defined in HQET, whereas the c-quark mass is kept finite. The leading-order contributions of two- and three-particle distribution amplitudes are taken into
account. From the resulting light-cone sum rules we calculate all B→D
(*) form factors in the region of small momentum transfer (maximal recoil). In the infinite heavy-quark mass limit the sum rules
reduce to a single expression for the Isgur–Wise function. We compare our predictions with the form factors extracted from
experimental B→(*)
l
ν
l
decay rates fitted to dispersive parameterizations. 相似文献
7.
J. G. Körner K. Melnikov O. Yakovlev 《Zeitschrift fur Physik C Particles and Fields》1995,69(1):437-441
We consider the small velocity sum rules for heavy flavour semileptonic transitions that are used to estimate the zero recoil
values of semileptonic heavy flavour form factors. We analyze the complete O(α
s) radiative correction to these sum rules. The corrections are universal and influence all “model-independent” bounds previously
derived for semileptonic form factors at zero recoil.
Supported in part by the BMFT, Germany, under contract 06MZ730 相似文献
8.
K. Kumerički D. Müller K. Passek-Kumerički 《The European Physical Journal C - Particles and Fields》2008,58(2):193-215
To leading order approximation, the physical content of generalized parton distributions (GPDs) that is accessible in deep
virtual electroproduction of photons or mesons is contained in their value on the cross-over trajectory. This trajectory separates
the t-channel and s-channel dominated GPD regions. The underlying Lorentz covariance implies correspondence between these two regions through
their relation to GPDs on the cross-over trajectory. This point of view leads to a family of GPD sum rules which are a quark
analogue of finite energy sum rules and it guides us to a new phenomenological GPD concept. As an example, we discuss the
constraints from the JLab/Hall A data on the dominant u-quark GPD H. The question arises whether GPDs are governed by some kind of holographic principle. 相似文献
9.
Zhi-Gang Wang 《International Journal of Theoretical Physics》2012,51(2):507-517
In this article, we take the scalar diquarks as point particles and describe them as basic quantum fields, then introduce
the SU(3) color gauge interaction and new vacuum condensates to study the nonet scalar mesons as tetraquark states with the QCD
sum rules. Comparing with the conventional quark currents, the diquark currents have the outstanding advantage to satisfy
the two criteria of the QCD sum rules more easily. 相似文献
10.
A. G. Oganesian 《Physics of Atomic Nuclei》2009,72(3):465-469
The moments of the heavy-quark parton distribution functions in a heavy pseudoscalar meson are calculated from QCD sum rules.
Expanding these sum rules in the inverse heavy-quark mass we obtain the heavy-mass limits of the moments. Comparison with
the finite-mass results reveals that while the heavy-mass expansion works reasonably well for the b quark, one has to take into account terms of higher order than (1/m
c
)2 for the c quark. This result can provide a quantitative assessment of c- and b-quark fragmentation models based on the heavy-quark mass limit.
The text was submitted by the authors in English. 相似文献
11.
Finite energy and Laplace transform QCD sum rules atT0 are analyzed, and predictions for vacuum condensates are compared with the low temperature expansion of the energy density and pressure. Results show a serious disagreement which indicates a breakdown of the FESR programme already at dimension four, and which invalidates Laplace transform sum rules, at least in their straightforward extension to finite temperature. 相似文献
12.
Charmonium sum rules are analyzed with the primary goal to obtain the restrictions on the value of the dimension 4 gluon
condensate. The moments M
n
(Q
2
) of the polarization operator of the vector charm currents are calculated and compared with the experimental data. The three-loop
() perturbative corrections, the contribution of the gluon condensate with corrections and the contribution of the dimension 6 operator G3 are accounted. It is shown that the sum rules for the moments do not work at Q
2
= 0, where the perturbation series diverges and the G3 contribution is large. The domain in the (n, Q
2
) plane where the sum rules are legitimate is found. A strong correlation of the values of gluon condensate and charm quark mass is determined. The absolute limits are found to be for the gluon condensate and for the charm quark mass in the scheme.
Received: 16 July 2002 / Revised version: 6 November 2002 / Published online: 24 January 2003
RID="a"
ID="a" e-mail: ioffe@vitep1.itep.ru
RID="b"
ID="b" e-mail: zyablyuk@heron.itep.ru 相似文献
13.
H. Fredrikze 《Molecular physics》2013,111(5):903-922
The sum rules for neutron scattering experiments on monatomic isotopic mixtures are studied. The scattering is separated into a self part and a distinct part rather than into an incoherent part and a coherent part. Exact expressions for the moments are derived in terms of polynomials in ? 2. The coefficients in these polynomials are sums of averages of hermitean operators that have a classical analogue. For the interpretation, the coefficients are approximated including first order quantum corrections. It is argued that the separation into coherent and incoherent scattering is not justified in the presence of ‘isotopic incoherence’. Approximate expressions for the sum rules are proposed, in which combined averages (over the isotopic composition) appear of the scattering amplitudes and masses of the scattering atoms. These expressions, including first order quantum corrections to the sum rules, are not available in the literature. The importance of correct averaging over the isotopic composition of expressions that involve scattering amplitudes and masses is discussed for the case of a maximum incoherent mixture of 36Ar and 40Ar. 相似文献
14.
V. Vescoli J. Favand F. Mila L. Degiorgi 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):149-154
The validity of the optical sum rules has been addressed eversince and was always matter of debate. Particularly controversial
is the proof that the partial sum rules can be extended to both optical conductivity and energy loss function. We show in this paper that for both transverse
(optical conductivity) and longitudinal (energy loss function) absorption processes the corresponding sum rule can be theoretically
established and through appropriate conditions for the integration limits exactly verified. We also focus our attention on
the one-dimensional case within the microscopic Hubbard model. An application of these concepts to the quasi one-dimensional
systems, for which we have chosen the organic (TMTSF)2PF6 material, will also be presented.
Received: 19 December 1997 / Received in final form: 9 March 1998 / Accepted: 23 March 1998 相似文献
15.
Summary The asymptotic behaviours of particle correlation functions and the related sum rules are discussed for a layered classical
plasma withe
2/r interactions in the fluid state, in dependence on the number of layers. These properties derive from consistency conditions
imposed by screening on the hierarchical equations, as already treated by A. Alastuey and P. A. Martin (J. Stat. Phys.,39, 405 (1985)) for various Coulomb fluids. The main results concern i) the type of clustering of correlations needed for the
validity of multipolar sum rules at various orders, ii) the proof that the pair correlation function in a finite multilayer
may carry an electric dipole moment and the calculation of its partioning among the layers, and iii) the dimensionality crossover
in an infinitely extended or periodically repeated multiplayer with varying interlayer spacing and wave vector. 相似文献
16.
P. Kolář 《Czechoslovak Journal of Physics》1989,39(11):1317-1320
Conclusions The sets (3) and (4) of condensates have been compared using the QCD sum rules (2) with indefinite weight functions. A bad matching between both sets of condensates and experimental data has been obtained. The standard values (3) appear to be closer to data but some increase ofQ is necessary to improve the agreement. Only higher values ofm
0
2
could change the results of this analysis. It is interesting that negative values ofm
0
2
considerably improve the agreement with data; note that this quantity cannot be determined with a sufficient accuracy. We conclude that the QCD sum rules (2) cannot definitely determine a privileged set of condensates.Dedicated to Academician Václav Votruba on the occasion of his eightieth birthday. 相似文献
17.
We use an appropriate combination of moments of finite energy sum rules in QCD in order to compute the B
q
-meson decay constants f
B
and
. We perform the calculation using a two-loop computation of the imaginary part of the pseudoscalar two point function in terms of the running bottom quark mass. The results are stable against the so-called QCD duality threshold, and they are in agreement with the estimates obtained from Borel transform QCD sum rules and lattice computations.Received: 28 July 2004, Revised: 10 September 2004, Published online: 23 November 2004PACS:
12.38.Bx, 12.38.LgSupported by MCYT-FEDER under contract FPA2002-00612. 相似文献
18.
Berger MS 《Physical review letters》2001,87(13):131801
Higgs boson mass sum rules of supersymmetric models offer attractive targets for precision tests at future muon colliders. These sum rules involve the gauge boson masses as well as the masses of the Higgs boson states which can be precisely measured in the s-channel production process at a muon collider. These measurements can sensitively probe radiative corrections to the Higgs boson masses as well as test for CP violation and nonminimality of the Higgs sector. 相似文献
19.
The kaon B-parameter is computed in the framework of strictly local QCD sum rules for a threepoint function involving pseudoscalar currents. As an application of these sum rules we derive a low energy formula for the B-parameter. We show that strictly local QCD sum rules yield more reliable results than other QCD sum rules, since they need less phenomenological information and do not suffer from stability problems. Our result for the B-parameter isB=0.74±0.17. 相似文献
20.
In this paper we establish the validity of the BBGKY equilibrium equations for Coulomb states which have been obtained as thermodynamic limit of finite volume states. We also give a new derivation of thel-sum rules for phases constructed by the cluster expansion. These sum rules are interpreted as Ward identities associated to a symmetry of the screening phase.Supported by the Swiss National Foundation for Scientific Research. 相似文献