共查询到20条相似文献,搜索用时 15 毫秒
1.
Victor Elias 《Physics letters. [Part B]》1977,68(4):335-338
The Callan-Gross relation is shown to be consistent with MIT-SLAC data for for x ? 0.33 in deep inelastic eN scattering, despite the fact that these data are taken in the large Q2 region where F1 and F2 individually exhibit scaling violation. Comparison is made with asymptotic freedom predictions, and color excitation is proposed to explain large values of at small x. 相似文献
2.
The predictions of perturbative QCD are derived in the deep euclidean region, whereas the physical region for most observables is timelike. The confrontation of these predictions with experiment thus necessitates an analytic continuation. This we find introduces large higher order corrections in terms of αs(|Q2|), the usual choice ofperturbative expansion parameter. These corrections are naturally absorbed by changing to the expansion parameter , where αs(Q2)n is the leading term in the spacelike region. For the intermediate range of Q2 experimentally accessible at present, where is significantly smaller than αs(|Q2|), we find the resulting phenomenology is improved. In particular, we demonstrate how the values of obtained from analyses of quarkonium decays become consistent. 相似文献
3.
S. Childress P. Franzini J. Lee-Franzini R.L. McCarthy R.D. Schamberger P.M. Tuts 《Physics letters. [Part B]》1976,65(2):177-180
We have measured at 500 GeV the cross section for the inclusive reaction p + p → + X. We determine the mass spectrum of the diffractive peak to be and the scaling part of the cross section to be dσ/dMX2 = (15.7±1.1)/smb/GeV2. 相似文献
4.
C.A. Piketty 《Nuclear Physics B》1974,68(1):44-65
We have evaluated the parity-violation contribution in atoms in the framework of SO(3) gauge theory. Various hadronic models have been used: first, for simplicity, the unrealistic five-quark one, next, others involving three ordinary SU(3) triplets for which all unwanted strangeness-changing processes are suppressed, up to order . In the free quark approximation, we obtain quite similar parity-violation effects which are proportional to (ΔM2 is the difference of squared masses of leptons (MX02 ? Mν2 = MX02), or of quarks (ΔMq2)). Namely, in large atoms (Z ? 1) the electronic contribution which is proportional to gives the largest effect (are the spin, momentum operators and mass of the lepton). Parity-violating effects in SO(3) gauge models are ?10?4 smaller than those evaluated in the Weinberg theory with a neutral parity-violating current and will remain undetectable in the near future. 相似文献
5.
M. Ambrosio G. Anzivino G. Barbarino G. Carboni V. Cavasinni T. Del Prete P.D. Grannis D. Lloyd Owen M. Morganti G. Paternoster S. Patricelli M. Valdata-Nappi 《Physics letters. [Part B]》1982,115(6):495-502
We measured the differential cross section for p?p and pp elastic scattering in the momentum-transfer range 0.01 <|t| < 1.0 GeV2 at the CERN Intersecting Storage Rings with center-of-mass energy . Fitting the differential cross section with an exponential [Aexp (bt)], we found for |t| < 0.05 GeV2, whilst for |t| > 0.09 GeV2, . Using the optical theorem, we obtained for the total cross section and, by integrating the differential cross section, we obtained for the total elastic cross section . Calculations of σtot combining elastic-rate and total-rate measurements are also given. All of these measurements were also performed for pp scattering at the same energy, and the results for both reactions are compared. 相似文献
6.
We use semiclassical methods to discuss the scaling behaviour of quarkonium level splittings up to . Special emphasis is laid on the effects of asymptotic freedom which are found to be essential for . The bound t system will almost look like the ? system except that is larger than 0.8. In the ? system R will already be close to 0.8. 相似文献
7.
R. Stroynowski D. Blockus W. Dunwoodie D.W.G.S. Leith M. Marshall C.L. Woody B. Barnett C.Y. Chien T. Fieguth M. Gilchriese D. Hutchinson W.B. Johnson P. Kunz T. Lasinski L. Madansky W.T. Meyer A. Pevsner S. Williams 《Physics letters. [Part B]》1980,97(2):315-319
The production of prompt electron-positron pairs in 16 GeV/c π-p collisions has been measured using the LASS spectrometer at SLAC. An excess of events is observed above the estimated contribution of direct and Dalitz decays of known resonances in the kinematic range defined by and . The excess signal decreases slowly with increasing M, but exhibits very steep χ and pT2 dependence. 相似文献
8.
M. Coupland E. Eisenhandler W.R. Gibson P.I.P. Kalmus A. Astbury 《Physics letters. [Part B]》1977,71(2):460-464
Antiproton-proton total elastic cross sections at 21 incident momenta in the range 0.69 to 2.43 GeV/c have been deduced by combining p?p elastic differential cross sections over a c.m. angular range with forward elastic cross sections derived from recent real-part measurements and p?p total cross sections. Two bumps are observed, at and , having widths of Г1 ~ 0.135 and . Corresponding structures in other p?p reaction channels are discussed. 相似文献
9.
H. Kleinert 《Physics letters. [Part B]》1976,62(1):77-80
In quark gluon theory with very small bare masses, -ψ, spontaneous breakdown of chiral symmetry generates sizable masses Mu, Md, Ms, … We find (. Scalar densities have well determined non-zero vaccum expectations at an SU(3) breaking of the vacuum c′ ≡ 〈0|u8|〉/〈0|uo|0〉 ≈ ? 16% 相似文献
10.
We discuss couplings of scalar gluonium σ on the basis of the low energy theorems of broken chiral symmetry and the anomalous trace of the energy—momentum tensor, implemented using a phenomenological lagrangian. Taking the ITEP value of the gluon consensate as input, we find and , while mσ is undetermined. These results suggest that if the scalar gluonium mass is above 1 GeV, it is probably unobservably wide, while production in γγ collisions is probably too small to be detectable if mσ < 1.5 GeV. We comment on the observability of J/ψ → σ + γ and on the relevance of our results to other gluonia. 相似文献
11.
Otto Nachtmann 《Nuclear Physics B》1981,187(1):141-148
We consider the contribution to in deep inelastic lepton-hadron scattering from a certain class of 4-quark operators in the framework of QCD. We find for this case by explicit calculation that is of order g2(Q2), with g2(Q2) the running coupling strength of QCD, in agreement with a general result of Politzer. 相似文献
12.
M. Haguenauer P. Lundborg C. Matteuzzi G. Poulard L. Ramello S. Bonetti D. Cavalli D. Pedrini A. Pullia Ph. Heusse 《Physics letters. [Part B]》1981,100(2):185-190
Quark fragmentation functions are studied with ≈3500 charged current events induced in the bubble chamber Gargamelle by neutrinos of the SPS wide band beam, with 〈Eν〉 ≈ 25 GeV. The Q2 and W2 regions covered by this experiment are Q2 ≈ 0–40 GeV2 and W2 ≈ 1–100 GeV2, the mean values being 〈Q2〉 = 6.5 GeV2, 〈W2〉 = 22GeV2. A correlation between the variables and is found in the data in the region Q2 = 1–10 GeV2, which can be explained in terms of higher twist effects. These effects reproduce the Q2 evolution of the non-singlet moments of the fragmentation function without any need for logarithmic terms. 相似文献
13.
S.L. Verbeck J.C. Fong G. Igo C.A. Whitten D.L. Hendrie Y. Terrien V. Perez-Mendez G.W. Hoffmann 《Physics letters. [Part B]》1975,59(4):339-342
The energy spectra of α-particles recoiling from a 4He gas target bombarded by 0.58 and 0.72 GeV protons have been measured to obtain the differential cross sections for elastic scattering , in the region of four-momentum transfer squared, ?t=0.13 ? 0.55 (GeV/c)2. The experiment was designed especially to observe the region between the first and second diffraction maxima. 相似文献
14.
Results are presented of a 12 event/μb bubble-chamber experiment; the reactions discussed in detail are .The K1 (890)?p channel is dominated by the forward peak. The suggestion of flattering at cos θ = 1 is more pronounced in ; which is mainly natural-parity exchange. Pseudoscalar exchange contributes to ; this is more sharply peaked in t. The value of is somewhat larger than the upper limit from the dominant natural-parity exchange. There is significant structure in .The K1 (1420)?p channel is much more pronounced at 3.3 GeV/c than at 3.13 GeV/c, but is not markedly peripheral. The width of the K1 (1420) in the 3.3 GeV/c data is 42 ± 12 MeV/c2.The cross section for agrees with that expected from , assuming a single t-channel exchange. Our measured density matrix elements are consistent with a strong pseudoscalar exchange. 相似文献
15.
It is assumed that nucleon consists of three quarks with no admixture of gluons or strange quarks. Gluons as are seen in deep inelastic scattering, appear only as a result of bremsstrahlung by valence quarks. The model gives unique predictions for observable quantaties and imitates the scaling behavior at Q2 ? 2 GeV2 provided the coupling constant of strong interactions is relatively small at such values of . The predictions of the model agree with the data within (10 – 20) % accuracy and links consideration of deep inelastic scattering with the most naive quark model. The effect of charmed particles production is estimated within the model developed. It is shown that the standard four-quark model of weak interactions is inconsistent with observed anomalies in ν, -interactions. 相似文献
16.
The processes with the cross sections not decreasing with energy become important at high energies. The simplest processes of this kind are γγ → Vi0Vj0 where V0 = ?0, ω, ?, ….. We calculate their cross sections in the high-energy small angle region s ? |t| ? μ2. The cross section γγ → ?0?0 at high energies (s ? 10 GeV2) exceeds those of γγ → ππ, ?+?? considerably. At (this is the characteristic energy for the VLEPP and SLC colliders) and , the ratio . 相似文献
17.
Otto Nachtmann 《Nuclear Physics B》1974,74(3):422-428
Recent experimental results on electroproduction off protons show that the ratio σ(ep → eK+Σ0)/σ(ep → eK+Λ) decreases strongly with increasing Q2. A simple argument is given in the framework of the quark parton model which could provide a qualitative understanding of this fact. The decrease of the Σ0/Λ ratio is related to the decrease of the ratio as Q2 increases, where are the usual structure functions for deep inelastic electron-nucleon scattering. 相似文献
18.
19.
The average multiplicity in deep inelastic electro- and neutrinoproduction at large ω(ω~s/Q2 + 1) is related in Feynman's version of the parton model to the average multiplicities in high-energy electron-positron annihilation and hadron-hadron scattering. The relation is: , where Ce+e? and Ch are, respectively, the coefficients of ln(s/M1⊥2) in the multiplicities from e+-e? and P-P in to hadrons, and M1⊥ is an average transverse mass. 相似文献
20.
The cross section for production of single photons in the process is calculated including selectron propagator and photino mass effects and is found to be significantly smaller than the local limit for selectron masses ? 35 GeV/c2. Numerical results for the cross section are obtained as a function of selectron masses for photino masses and electron beam energies E = 14.5, 25, and 35 GeV appropriate to PEP, PETRA, and TRISTAN, respectively. 相似文献