共查询到20条相似文献,搜索用时 46 毫秒
1.
Thomas D. Gottschalk 《Nuclear Physics B》1983,227(3):413-434
Predictions of the QCD cluster model for charm production in high energy e+e? annihilation are presented. Details of the model relevant for heavy flavor production are discussed. The model is shown to describe well the shape of the recently measured z-distribution for charged D1 production at Q = 29 GeV. Reported rates for D1 production at CESR, PEP, and PETRA are found to be inexplicably high. Substantial Λc production is predicted, with the ratio found to be roughly flat in z for z ? 0.5 at high energies. It is argued that the results presented here are rather general predictions of models in which color is locally screened before hadrons actually form. 相似文献
2.
R. Sugahara F. Ochiai Y. Fukui A.M. Cooper M. Fukawa S. Kabe H. Kichimi A. Ono T. Sato A. Suzuki Y. Yoshimura K. Takahashi T. Okusawa K. Tanahashi S. Sasaki M. Teranaka O. Kusumoto T. Konishi 《Nuclear Physics B》1979,156(2):237-251
The inclusive production of Λ, KS0, Σ±(1385) and in π?p interactions at 6 GeV/c has been studied. The observed cross sections are: σ(Λ)=0.94±0.06 mb, σ(KS0)=0.98±0.06 mb, σ(Σ+(1385))=60±7 μb, σ(Σ?(1385))=90±9 μb, , respectively. The inclusive spectra of these particles are presented as functions of squared transverse momentum and Feynman scaling variable x. The polarization of Λ has also been investigated. It is found from a comparison with higher-energy data that the inclusive cross sections for Σ±(1385) and the production ratios Σ±(1385)/Λ in π?p at 6 GeV/c have not reached the high-energy limiting values. 相似文献
3.
P.V. Chliapnikov P.A. Gorbunov S.A. Gumenyuk V.V. Kniazev B.A. Manyukov V.M. Perevoztchikov V.N. Riadovikov V.A. Uvarov M.L. Faccini-Turluer M. Loret L. Mosca H. Blumenfeld J. Laberrigue C. Dujardin F. Grard J. Skura R. Windmolders M. Csejthey-Barth M. Gysen 《Nuclear Physics B》1977,131(1):93-106
A study of the inclusive and semi-inclusive Λ and production in K+p interactions at 32 GeV/c is presented. The inclusive cross sections for Λ and amount to 0.78 ± 0.05 and 0.42 ± 0.04 mb thus showing a remarkable growth between 16 and 32 GeV/c with a factor of 1.7 for Λ and 2.8 for . Target and beam fragmentation processes are found to be dominant for Λ and production respectively with the following lower limits for the corresponding cross sections: and . Although the early scaling conditions are fulfilled for the Λ production in the target fragmentation region, and production in the beam fragmentation region, scaling is not observed between 16 and 32 GeV/c in the x and pT2 Feynman variables. The Λ production is found to be very similar in the K+p inclusive reaction at 32 GeV/c and in the semi-inclusive reaction at the same energy. The pair production cross section increases significantly in K+p interactions from 16 to 32 GeV/c where it reaches the value . The cross sections for Λ or produced in association with an identified proton are also given and discussed. 相似文献
4.
T. P. McPharlin D. O. Caldwell J. P. Cumalat A. M. Eisner D. L. Fancher R. J. Morrison F. V. Murphy T. R. Risser S. J. Yellin 《Physics letters. [Part B]》1980,90(4):479-484
Using 20.5 GeV electrons on protons, we measured inclusive π0's (of transverse momentum, pT, from 0 to 1.4 GeV/c) produced by virtual photons of energy, ν, from 4 to 16.5 GeV and four-momentum squared, q2, from ?1.8 to ?8.5 (GeV/c)2. Comparing with charged pion data, we find , supporting the quark model. Photon knockout of a quark is favored as the interpretation of these data because of scaling in z = Eπ/ν and similarity in z-dependence of other pion production data. Consistent with this interpretation are the dependence of 〈pT〉 on q2, the azimuthal dependence, and fits to the constituent interchange model. We also observe a possible pT?4 dependence at large |q2| over a limited pT range. 相似文献
5.
M.J. Corden J.D. Dowell J. Garvey R.J. Homer M. Jobes I.R. Kenyon T. McMahon R.C. Owen K.C.T.O. Sumorok R.J. Vallance P.M. Watkins J.A. Wilson P. Sonderegger B. Chaurand A. Romana R. Salmeron 《Physics letters. [Part B]》1981,98(3):220-224
J/ψ production at 40 GeV/c by π±, K±, p and incident on hydrogen has been studied and results compared with those obtained on tungsten in the same experiment. On hydrogen, J/ψ cross-section ratios relative to π? have been measured to be (for . The suppression of the proton induced cross sections shows the importance of calence quark-antiquark fusiin J/ψ production at this energy (i.e. MJ2/ψ/s=0.13). 相似文献
6.
A. Apostolakis R. Casali C. Caso Y. Goldschmidt-clermont L. Pape J.P. Porte A. Stergiou B. Tallini G. Vassiliadis H. Wenninger G. Grard V.P. Henri P. Herquet J. Kesteman S. Banerjee K.W.J. Barnham R. Beuselinck I. Butterworth A. Jacholkowska 《Physics letters. [Part B]》1977,66(2):185-190
We report the evidence for a narrow charged peak (5.5 s.d.), which we suggest calling the I, in the 6-prong-V0 topology of p interactions at 12 GeV/c. The mass, widht and the product of cross section σI times the branching ratio BR into the final state (Ksoτ±τ+τ? are found to be: , , σI·BR≈20 μbarn 相似文献
7.
The Stark effect of rotational and torsio-rotational transitions of propargyl mercaptan has been analyzed. Assuming a dependence of the dipole moment components on the internal rotation angle of the type: , , and , the following values of the determinable quantities were obtained: , , and .The SH bond moment was also evaluated from and compared with the SH bond moment of similar molecules. 相似文献
8.
I.V. Ajinenko Y.A. Belokopitov P.V. Chliapnikov L.N. Gerdyukov V.V. Kniazev A.I. Kurnosenko A.K. Likhoded V.M. Perevoztchikov V.N. Riadovikov A.M. Rybin O.G. Tchikilev V.F. Tchunikhin V.A. Uvarov A.P. Vorobjev 《Nuclear Physics B》1980,176(1):51-60
The inclusive production of and Ξ? hyperons is investigated in K+ p interactions at 32 GeV/c. The production cross sections, 36.4±9 μb for the and 6.5±3 μb for the Ξ?, are rising strongly with energy similarly to and Λ production in K+ p interactions. The are produced preferentially in the forward direction in the c.m.s., while the Ξ? are produced dominantly backwards. The average transverse momenta and 〈pT〉Ξ?=0.58±0.09 GeV/c. 相似文献
9.
Three-, two-, and one-dimensional disordered systems with randomly distributed, purely repulsive scattering centers, known as Lorentz models, are studied in the low energy limit [1]. Using a functional integral representation and a version of the “replica trick”, we have found in the D-dimensional system the density of electronic levels of the form and the constants b0, b1,…, bD, and γ have been determined. 相似文献
10.
A. Ferrer D. Treille P. Rivet A. Volte P. Benkheiri G. De Rosny A. Rougé B. Bouquet B. DAlmagne H. Nguyen P. Petroff F. Richard P. Roudeau J. Six H. Yoshida 《Nuclear Physics B》1981,178(3):373-391
We have analysed about 85 000 fast Λ0 events, obtained in a fast proton triggered experiment performed at the CERN-Ω spectrometer at 9 and 12 GeV/c incident π? beam. Nearly 2500 Λ0K+π? events have been isolated. We find strong production of quasi-two-body processes and consistent with u-channel hyperon exchange. Results on Λ0 polarization, K10 decay parameters and differential cross sections are given for and final states. A comparison is made with the associated backward production seen in the four-prong reaction π?p→pK?K+π? obtained in the same experiment. 相似文献
11.
H. Laven G. Otter G. Rudolph R. Klein H.J. Schreiber D.J. Kocher D.R.O. Morrison P. Schmid K.L. Wernhard R.M. Eason T.C. Bacon K.W.J. Barnham P.J. Dornan B. Pollock J. Macnaughton M. Markytan 《Nuclear Physics B》1977,127(1):43-56
The reactions (1) K?p → K+K?Λ and (2) have been studied on samples of 109 and 64 events, respectively, at 10 GeV/c and 125 and 69 events at 16 GeV/c, reasonably free from contaminations. The investigation of the first reaction uses also 84 events of the final state at 10 GeV/c. Analysis of the Van Hove plots indicates that the K+K?Λ and final states are produced by two main mechanisms: (i) a ΔQ = 0 process, with a strong diffractive component near threshold, involving the dissociations p → K+Λ in reaction (1) and in reaction (2) and (ii) a ΔQ = 1 process involving hypercharge exchange, and producing K+K? and systems in reactions (1) and (2), respectively, recoiling off the Λ. With increasing energy, this hypercharge exchange process decreases slowly when K+K? is produced, but fast where the production of , violating the Zweig rule, occurs. 相似文献
12.
We make a theoretical and phenomenological study of correlations between neutral and charged pions in multiparticle production in the framework of the so-called σ, π, ? and ?-? models. Following the method of Drijard and Pokorski, we express the predictions of various models in terms of the negative multiplicity distribution, which is known experimentally. In particular we compute the average number of , and the integral of π0?π0 correlations, f02(n_), as a function of the number of negative pions; we study also the total multiplicity distribution P(N) and its first two moments . We show that with the present experimental accuracy neither allow us to discriminate between the different models. 相似文献
13.
14.
K. Alpgård G. Ekspong P.O. Hulth U. Svedin N. Yamdagni F.O. Breivik A.G. Frodesen A. Krogstad V.-M. Hagman V. Karimäki P. Villanen 《Nuclear Physics B》1976,103(2):234-246
Inclusive cross sections are presented for strange-particle production in proton-proton interactions at 19 GeV/c for the pairs and for Λ, Ks0, Σ+, Σ? and Ξ?. The , the KY and the total strange particle cross sections have been found to be 1.40 ± 0.10 mb, 2.69 ± 0.09 mb and 4.23 ± 0.20 mb, respectively. The charged multiplicity distributions for events with Ks0, Λ, or K0 Λ are shown to follow a modified KNO curve, whereas K+ Λ does not. For the inclusive reactions , we find that the average charged multiplicity of the remainder system X++ is the same as when X++ is produced in other reactions with the same system energy and quantum numbers. 相似文献
15.
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
16.
R.M. Macfarlane 《Solid State Communications》1974,15(3):535-538
We have observed inter-term Raman scattering from 5T2g→5Eg Frenkel excitons in antiferromagnetic FeF2. It differs qualitatively from previously observed intra-term scattering in a sharply reduced zero-phonon cross section and the appearance of relatively strong exciton-phonon scattering. Since the Raman process is fully allowed, it is possible to measure excited state Debye-Waller factors, D, and we find and . 相似文献
17.
Given a mapping , whose bifurcation points accumulate at λ = Λ∞, it is shown that the iterates converge to a function ψ(μ,y)asp→∞, where X∞ maximizes . The function ψ is universal up to scaling in μ and y, and satisfies ψ(μ/δ,ψ(μ/δ,?y/α)) = ?α?1ψ(μ,y). This result generalizes the well-known Feigenbaum universal function g(y) with g(g(?y/α)) = ?g(y/α, which is the special case for μ = 0. 相似文献
18.
It is proved that the quantum mechanical Hamiltonian for bosons (resp, fermions) is bounded from below if N ≤ cbκ?1 (resp. ). H is unbounded from below if N ≥ cblκ?1 (resp. ). The constants cb and cbl (resp. cf and cfl) differ by about a factor 2 (resp. 4). 相似文献
19.
In this note we determine the oscillator strengths for the dipole absorption of neutral bound excitons in direct gap semiconductors, using our previously obtained 35-term Page and Fraser type wave function, and taking into account the detailed electronic structure as well as the electron-hole exchange interaction.The envelope part of the oscillator strengths varies considerably with the electron-hole mass ratio , and is maximum for the (D0, X)- complex when σ = 0.4. For typical σ-values (σ? 0.1–0.2), . But when σ approaches zero, the overlapping of the electron and the hole envelope wave functions of the (A0,X)-complex decreases progressively so that the oscillator strength also decreases and tends to zero.In the case of zinc-blende materials (Td) and positive spin-orbit coupling at , we confirm that the line strength for transitions to or from or level of the (A0, X)-complex is equal to one quarter of the line strength to or from the level.In the case of CdS, where our computed values are only in qualitative agreement with the experimental values, we discuss the use of the phenomenological result of Rashba. 相似文献
20.
H. Taureg G. Zech F. Dydak F.L. Navarria P. Steffen J. Steinberger H. Wahl E.G.H. Williams C. Geweniger K. Kleinknecht 《Physics letters. [Part B]》1976,65(1):92-96
The branching ratio has been determined to be (2.68±0.15)×10?3 for photon energies greater than 50 MeV in the KS0 rest frame. The decay KS0→π+π?γ is found to be dominated by the internal bremsstrahlung transition. The branching rato of a possible direct transition is found to be less than 0.06 × 10?3 at 90% confidence level for . 相似文献