共查询到20条相似文献,搜索用时 437 毫秒
1.
J. Bartels B. I. Ermolaev M. G. Ryskin 《Zeitschrift fur Physik C Particles and Fields》1996,72(4):627-635
The singlet contribution to theg 1(x, Q 2) structure function is calculated in the double-logarithmic approximation of perturbative QCD in the regionx?1. Double logarithmic contributions of the type (α s ln2(1/x)) k which are not included in the GLAP evolution equations are shown to give a power-like rise at small-x which is much stronger than the extrapolation of the GLAP expressions. The dominant contribution is due to the gluons which, in contrast to the unpolarized case, mix with the fermions also in the regionx?1. The two main reasons why the small-x behavior of the double logarithmic approximation is so much stronger than the usual GLAP evolution are: the larger kinematical region of integration (in particular, no ordering in transverse momentum) and the contributions from non-ladder diagrams. 相似文献
2.
We obtain a relation between the longitudinal structure function F
L(x, Q
2), F
2(x, Q
2) and G(x, Q
2) at small x, using the formalism recently reported by one of the authors [2]. We also obtain a relation between F
L(x, Q
2), F
2(x, Q
2) and its slope (dF
2(x, Q
2))/(dlnQ
2). This provides us with the determination of the longitudinal structure function F
L(x, Q
2) from F
2(x, Q
2) data and hence extract the gluon distribution G(x, Q
2). 相似文献
3.
At lowx, an analytic solution of the DGLAP equation for gluon in the next-to-leading order (NLO) is obtained by applying the method
of characteristics. Its compatibility with double leading logarithmic approximation (DLLA) asymptotics is discussed and comparison
with the exact ones like GRV98NLO is made. The solution is then utilized to calculate the derivatives∂F
2 (x,Q
2)/∂ lnQ
2
and ∂ lnF
2(x,Q
2)/∂ ln (1/x) and compared with the recent HERA data. Our solution is found to reproduce most of the essential features of the data on
the derivatives. 相似文献
4.
S.I. Manayenkov 《Zeitschrift fur Physik C Particles and Fields》1997,75(4):685-692
The analytical solution of the double-logarithmic integral equation with QCD running coupling describing small-x behaviour of the non-singlet structure function ? NS(x,Q 2) has been found for any cut-off parameter μ. Analytical properties of the solution and a position of the right-most singularity in the complex ρ-plane which determines the asymptotics of ? NS(x,Q 2) at small x have been studied. The asymptotical formula ? NS(x,Q 2) = C 1 x -λ1{lnκ1(Q 2/Λ2) —lnκ1 (μ 2/Λ2) + κ 1 lnκ1-1(Q 2/Λ2)[ψ(1) - ψ(λ1)]} valid if x ? 1 and ln(Q 2/Λ2) ? 1 has been obtained where C 1, λ1 are constants, κ 1 = g/λ1, λ1 < g = 8/(33 - 2gh f), gh f is a number of active flavours and ψ(ξ) denotes the digamma function. 相似文献
5.
《Nuclear Physics B》1999,537(1-3):477-500
6.
The transverse polarization distribution of quarks h1(x) is computed in a confinement model, the chiral chromodielectric model. The flavor structure of h1, its Q2 evolution and Soffer's inequality are studied. The Drell-Yan double transverse asymmetry ATT is evaluated and found to be one order of magnitude smaller than some previous estimates which equated it to the double longitudinal asymmetry. 相似文献
7.
We consider in detail Q 2-dependence of the DIS structure functions. Very often this dependence is claimed to be originated by the Q 2-dependence of the QCD coupling. This leads to the small-x asymptotics of the structure functions with Q 2-dependent intercepts. We demonstrate that the DGLAP parametrization α s = α s (Q 2) is an approximation valid in the region of large x (where 2pq can be approximated by Q 2) only, providing the factorization scale is also large. Outside this region, the DGLAP parametrization fails, so α s should be replaced by an effective coupling which is independent of Q 2 at small x. As a consequence, intercepts of the structure functions are independent of Q 2 . Nevertheless, the small-x asymptotics of the structure functions explicitly depend on Q 2 , even when the coupling does not depend on it. We also consider the structure functions at small Q 2 and give a comment on power-Q 2 corrections to the structure functions at large and small Q 2 . 相似文献
8.
《Nuclear Physics B》1995,439(3):471-502
A measurement of the proton structure function F2(x, Q2) is reported for momentum transfers squared Q2 between 4.5 GeV2 and 1600 GeV2 and for Bjorken x between 1.8 × 10−14 and 0.13 using data collected by the HERA experiment H1 in 1993. It is observed that F2 increases significantly with decreasing x, confirming our previous measurement made with one tenth of the data available in this analysis. The Q2 dependence is approximately logarithmic over the full kinematic range covered. The subsample of deep inelastic events with a large pseudo-rapidity gap in the hadronic energy flow close to the proton remnant is used to measure the “diffractive” contribution to F2. 相似文献
9.
Stefano Catani 《Zeitschrift fur Physik C Particles and Fields》1997,75(4):665-678
I present a theoretical discussion of the uncertainties related to the QCD analysis of the proton structure function F 2(x,Q 2) at small x. The role played by the ‘unphysical’ gluon density is pointed out. It is shown how the study of more observables can reduce the theoretical uncertainty and, in particular, an alternative method of analysis, based on the introduction of physical anomalous dimensions, is suggested. 相似文献
10.
S. I. Manayenkov M. G. Ryskin 《The European Physical Journal C - Particles and Fields》1998,1(1-2):271-283
The role playing by the “soft” (κ T < 1 GeV/c) region in the small-x behaviour ofg 1(x,Q 2) and the non-singlet structure functionf 1, NS(x, Q2) has been studied with the help of the effective QCD Lagrangian which takes into account the lightest degrees of freedom — the constituent quarks and the π-mesons (Goldstone bosons). It has been shown that the quark-quark interaction due to the pion exchange has a negative couplingg for the isovector component (I = 1 in thet-channel) off 1(x,Q 2) and isosinglet component ofg 1(x, Q2). Here the pion induced interaction changes mainly the normalization of the quark distribution (it decreasesf 1,NS I = 1 (x,Q 2) two times atx < 3·10?3) and changes slightly the effective exponents λ (?1,NS ,g 1 ~x ?λ atx → 0). On the other hand due to a positive value of couplingg the value of λ increases by 15% for the isovector part ofg 1 (x,Q 2) and up to λ ≈ 0.5 (instead of λ ≈ 0.2 without the pion contribution) for the isoscalar non-singlet structure functionf 1,NS I = 0 (x,Q 2). 相似文献
11.
J. Kwieciński 《Zeitschrift fur Physik C Particles and Fields》1985,29(4):561-567
The gluon distributions in a proton are calculated in the region of smallx (10?4?x?10?2) and largeQ 2 taking into account the corrections which correspond to the sum of the leading powers of log 1/x beyond the leading logQ 2 approximation. It is shown that they become significant for very small values ofx only provided however that the non-leading terms in the limit of smallx are also consistently included. The leading log 1/x approximation gives the gluon distributions which can differ by a factor of 2 from their leading logQ 2 counterpart. 相似文献
12.
We study the heavy-quark contributions to the proton structure function F 2(x,Q 2) at next-to-leading order using compact formulas at small values of Bjorken??s x variable. The formulas provide a good agreement with the modern HERA data for F 2 c (x,Q 2). 相似文献
13.
The differential gluon structure function of the proton, ?(x, Q 2), introduced by Fadin, Kuraev, and Lipatov in 1975 is extensively used in small-x QCD. We report here the first determination of ?(x, Q 2) from experimental data on the small-x proton structure function F 2p (x, Q 2). We give convenient parametrizations for ?(x, Q 2) based partly on the available DGLAP evolution fits (GRV, CTEQ, and MRS) to parton distribution functions and on realistic extrapolations into the soft region. We discuss the impact of soft gluons on various observables. The x dependence of the so-determined ?(x, Q 2) varies strongly with Q 2 and does not exhibit simple Regge properties. Nonetheless, the hard-to-soft diffusion is found to give rise to a viable approximation of the proton structure function F 2p (x, Q 2) by the soft and hard Regge components with intercepts Δsoft=0 and Δhard ~ 0.4. 相似文献
14.
《Nuclear Physics A》1997,626(4):886-910
We study the chiral-odd transversity spin-dependent quark distribution function h1(x) of the nucleon in a constituent quark model. The twist-2 structure functions, f1(x), g1(x) and h1(x) are calculated within the diquark spectator approximation. Whereas an inequality f1(x) > h1(x) > g1(x) holds with the interaction between quark and diquark being scalar, the axial-vector effective quark-diquark interaction, which contributes to the d-quark distribution, does not lead to such a simple relation. We find that h1(x) for the d-quark becomes somewhat smaller than g1d(x), when we fix the model parameter to reproduce known other structure functions. We also include corrections due to the non-trivial structure of the constituent quark, which is modeled by the Goldstone boson dressing. This improves agreements of f1(x) and g1(x) with experiments, and brings further reduction of h1d(x) distribution. Consequences for semi-inclusive experiments are also discussed. 相似文献
15.
D. P. Tarasov 《Technical Physics》2013,58(2):213-217
The elastic (G) and inelastic (Q ?1) properties of (Co45Fe45Zr10) x (Al2O3)100 ? x , Co x (CaF2)100 ? x , and Co x (PZT)100 ? x (x = 23–76 at %) nanocomposites obtained by ion-beam sputtering are studied in the temperature range 300–900 K. A significant rise in the Q Q ?1 (T) curve is observed at temperatures above 650 K, which is attributed to thermally activated migration of point defects under the conditions of confined geometry. 相似文献
16.
W. Vogelsang 《Zeitschrift fur Physik C Particles and Fields》1991,50(2):275-283
We present a careful analysis of the polarized photon-gluon fusion process. Discussing various regularization schemes it is demonstrated that one can safely extract a hard gluonic contribution to the proton's spin dependent structure functiong 1 P . The value of the first moment of the gluonic Wilson coefficient is shown to be in agreement with the anomaly result. Furthermore, we examine the question whether the gluonic contribution alone can account for existing experimental data forg 1 P (x,Q 2) (x≧0.01, <Q 2>?Q 0 2 =10 GeV2) and find a positive answer. 相似文献
17.
18.
Jerrold Franklin 《Nuclear Physics B》1978,138(1):122-140
Electron-proton deep inelastic scattering is treated as the incoherent scattering of electrons by bound Dirac partons in the proton rest frame. An approximate bound state wave function is used for the initial parton, while the final parton is considered free. A good fit is obtained to the structure function F1(x,Q2) in the range x > 0.15, Q2 > 2 GeV. The subsequent prediction for F2(x,Q2) is not as good, indicating a small additional contribution by longitudinal photons for W < 2.5 GeV. The parton momentum distribution is found to contain transverse momentum of 400–600 MeV, increasing with x. 相似文献
19.
《Physics letters. [Part B]》2001,504(3):235-240
We calculate twist-4 coefficient functions for the deep inelastic structure function F2(x,Q2) associated to 4-gluon operator matrix elements for general values of the Bjorken variable x and study the numerical effect on the slope ∂F2(x,Q2)/∂logQ2. It is shown that these contributions diminish the strongly rising twist-2 terms towards small values of x. 相似文献
20.
《Nuclear Physics B》1999,539(3):535-554
A systematic study of ϖF2(x, Q2)/ϖ ln Q2 and ϖ ln F2(x, Q2)/ϖ ln(1/x) is carried out in pQCD taking screening corrections into account. The result of calculations, which are different from the non-screened DGLAP prediction, are compared and shown to agree with the available experimental data as well as a pseudo data base generated from the ALLM'97 parameterization. This pseudo data base allows us to study in detail our predictions over a wider kinematic region than is available experimentally, and allows us to make suggestions for future experiments. Our results are compared with the GRV'94 parameterization (which is used as an input for our calculations) as well as the recently proposed MRST structure functions. 相似文献