共查询到20条相似文献,搜索用时 31 毫秒
1.
It is shown that measurement of the cross-section differences at large transverse momentum provides a good test of perturbative QCD. Such differences are insensitive to the parton Fermi motion and to the poorly known sea-quark and gluon distribution functions. Moreover the hadronized photon component is shown to contribute little compared to the point-like one. Presently available photon beams at the CERN-SPS and FNAL are sufficient to test QCD in large-pT photoproduction. 相似文献
2.
T. Fujii T. Kondo F. Takasaki S. Yamada S. Homma K. Huke S. Kato H. Okuno I. Endo H. Fujii 《Nuclear Physics B》1977,120(3):395-422
The differential cross sections for γp→π+n from hydrogen and the ratios from deuterium were measured at nine c.m. angles between 30° and 150° for laboratory photon energies between 260 and 800 MeV. A magnetic spectrometer with three layers of scintillation hodoscope was used to detect charged π mesons. The cross section for γn→π?p was obtained as a product of and the ratio. The overall features in the cross sections of the two reactions, γp→π+n and γn→π?p, and in the ratios, , agree with predictions by Moorhouse, Oberlack and Rosenfeld, and Metcalf and Walker. An investigation of the possible existence of an isotensor current was made and a negative result was found. In detailed balance comparison with the new results on the inverse reaction π?p→γn, no apparent violation of time-reversal invariance was observed. 相似文献
3.
P. Gregory D. Everett P. Grossmann P. Mason H. Muirhead G. Warren R. Carlsson G. Ekspong S.O. Holmgren S. Nilsson R. Stenbacka C. Walck 《Nuclear Physics B》1974,78(2):222-232
Relations have been derived between the invariant cross sections for various inclusive processes by assuming factorisation of the leading (pomeron) and non-leading (meson) trajectories. In this paper predictions for the invariant cross sections have been tested using data from interactions at 4.6 and 9.1 GeV/c.A large discrepancy between experiment and theory is apparent for the π? data: in the π+ case the discrepancy is less marked but still present. 相似文献
4.
Yu.M. Antipov V.A. Bessubov N.P. Budanov Yu.P. Gorin S.P. Denisov S.V. Klimenko A.A. Lebedev Yu.V. Mikhailov A.I. Petrukhin S.A. Polovnikov V.N. Roinishvili D.A. Stoyanova F.A. Yotch 《Physics letters. [Part B]》1978,76(2):235-236
The differential cross sections and of inclusive J/ψ production by 43 GeV/c π? off Be, Cu and W nuclei have been measured. Fitting we observed the increase of α with pt2. 相似文献
5.
A high-accuracy investigation of the level scheme of 47V has been performed using the 46Ti(p, γ)47V reaction. The γ-decay schemes of the strong (p, γ) resonances at Ep = 1546, 1549, 1565 and 1572 keV lead to 17 new energy levels in 47V with excitation energies between 2.7 and 5.1 MeV. From the (p,γ) angular distributions mixing ratios of the primary γ-transitions and Jπ values of the resonances and of many states populated in the γ-decay have been determined. The total width of the Ep = 1549, 1565 and 1572 keV resonances for γ-decay are found to be Γγ = 0.12, 0.15 and 0.03 eV, respectively. The Q-value of the 46Ti(p,γ)47V reaction is found to be 5168.6 keV. The two resonances at Ep = 1549 and 1565 keV, which have , are interpreted as fine structure components of the analogue state of the level in 47Ti while the () resonance at Ep = 1546 keV might correspond to the parent state in 47Ti. The analogue-antianalogue M1 transition strength of the split analogue state is 0.01 single-particle units and fits well into our systematics of IAS → AIAS transitions in fp-shell nuclei. 相似文献
6.
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
7.
Excitation functions of the capture reaction 12C(p, γ0)13N have been obtained at θγ = 0° and 90° and Ep = 150–2500 keV. The results can be explained if a direct radiative capture process, E1(s and d → p), to the ground state in 13N is included in the analysis in addition to the two well-known resonances in this beam energy range and 1699 . The direct capture component is enhanced through interference effects with the two resonance amplitudes. From the observed direct capture cross section, a spectroscopic factor of C2S(l = 1) = 0.49 ± 0.15 has been deduced for the ground state in 13N. Excitation functions for the reaction have been obtained at θγ = 0° and 90° and Ep = 610–2700 keV. Away from the 1699 keV resonance the capture γ-ray yield is dominated by the direct capture process E1 (p → s) to the unbound state. Above Ep = 1 MeV, the observed excitation functions are well reproduced by the direct capture theory to unbound states (bremsstrahlung theory). Below Ep = 1 MeV, i.e., Ep → 457 keV, the theory diverges in contrast to observation. This discrepancy is well known in bremsstrahlung theory as the “infrared problem”. From the observed direct capture cross sections at , a spectroscopic factor of C2S(l = 0) = 1.02 ± 0.15 has been found for the unbound state. A search for direct capture transitions to the and unbound states resulted in upper limits of C2S(l = 1) ≦ 0.5 and C2S(l = 2) ? 1.0, respectively. The results are compared with available stripping data as well as shell-model calculations. The astrophysical aspect of the 12C(p, γ0)13N reaction also is discussed. 相似文献
8.
C.P. Bust J.R. Carter W.W. Neale J.G. Rushbrooke D.R. Ward R.E. Ansorge B.Y. Oh M. Pratap G. Sionakides G.A. Smith J. Whitmore R. Raja L. Voyvodic 《Nuclear Physics B》1978,140(3):409-422
We have investigated the reactions . The final state is dominated by diffractive production of a system which shows a strong tendency to form . The process is also observed in this reaction, indicating an energy dependence of s?1.5±0.1. The channel shows less single diffraction, and has a doubly diffractive component consistent with pomeron factorization. Strong Δ++(Δ++) production is agoain seen, but in contrast to the channel we also observe considerable ?0 production. 相似文献
9.
D. Denegri Y. Pons R. Barloutaud A. Borg C. Louedec M. Spiro K. Paler T.P. Shah S.N. Tovey B. Chaurand B. Drevillon G. Labrosse R. Lestienne R.A. Salmeron 《Nuclear Physics B》1975,91(1):54-68
We have studied the reaction K-p → K-π+π-π+π-p at 14.3 GeV/c to search for evidence of the double dissociation process . In the channel π1-π2-Δ++ (1236) there is evidence for simultaneous production of low-mass enhancements in the and Δ++(1236)π2- subsystems which correspond to the and decay modes. In this particular final state the double fragmentation system is produced with a cross section of the order of a few microbarns. Our data are consistent with the factorizable pomeron exchange model of double diffractive dissociation. 相似文献
10.
G.W. Brandenburg W.B. Johnson D.W.G.S. Leith J.S. Loos J.A.J. Matthews F.C. Winkelmann R.J. Yamartino 《Physics letters. [Part B]》1973,44(3):305-309
Differential cross sections for center of mass scattering angles near 90° are presented for the reactions , and KL°p → KS°p in the momentum interval 1.0 to 7.5 GeV/c. The energy dependences of these cross sections are found to be equally well described by the parameterization: or . 相似文献
11.
G. Backenstoss M. Hasinoff P. Pavlopoulos J. Repond L. Tauscher D. Tröster P. Blüm R. Guigas H. Koch M. Meyer H. Poth U. Raich B. Richter L. Adiels I. Bergström K. Fransson A. Kerek M. Suffert K. Zioutas 《Nuclear Physics B》1983,228(3):424-438
Proton-antiproton annihilations at rest in liquid hydrogen were investigated through the inclusive γ spectrum, related to the annihilation. The high-energy part of the spectrum was used to deduce branching ratios for the so far unobserved annihilation channels: , , , and . An upper limit for the π0η′ channel was deduced to be . 相似文献
12.
The angular distribution of proton polarization Pγ' (θ) from the reaction has been measured at 975 keV deuteron energy. Moreover, the energy dependence of Pγ′(Ed) was measured at 45°(lab) for deuteron energies between 250 and 975 keV. The values of σ0(θ)Pγ' (θ) were fitted in terms of an associated Legendre polynomial expansion. The measured energy dependence of Pγ' (Ed) has been analyzed in terms of barrier-penetration parameters. 相似文献
13.
We present a microscopically-founded potential model for the reaction at energies of astrophysical interest. The model is shown to reproduce the cross section very well. The reaction is dominated by the first excited J = 1? resonance in 14O. For this resonance we find a proton width of Γc.m. = 40.1 keV and a photon width of Γγ = 1.50 eV. 相似文献
14.
The cross section, vector analyzing power, and proton polarization have been measured for the ln = 0 reaction 116Sn(d, p)117Sn(g.s.) at 8.22 MeV. In addition, cross section and analyzing power data have been obtained at 8.22 MeV for and for 116Sn(d, p)117Sn leading to excited states of 117Sn at 0.159, 0.317, 1.020, 1.179, 1.308 and 1.497 MeV. The cross section and analyzing power for and for leading to the 1.294 MeV state of 116Sn have also been measured at 12.91 MeV. The data for 116Sn(d, p)117Sn(g.s.) have been used to separate the contributions to the analyzing power arising from spin-dependent forces in the proton and deuteron channels. A similar analysis is presented for an transition at 11 MeV. Optical-model analyses have been performed for the elastic scattering data. The reaction data have been compared with distorted-wave calculations in order to investigate the validity of various deuteron potentials, as well as to extract spectroscopic information. 相似文献
15.
M.A. Jabiol D. Denegri C. Louedec F. Grard C. Poiret R. Windmolders M.I. Bogoljubsky A.M. Moiseev E.H. Starchenko E. De Wolf M. Barth M. Van Immerseel K.G. Zaitsev E.S. Lukin A.S. Proskurjakov L.N. Smirnova 《Nuclear Physics B》1981,183(3):330-348
The cross sections of several exclusive reactions in interactions are given. In the channels which dominate the interactions, the single and double diffractive dissociations are analysed and compared to the results obtained with K±p interactions at the same energy, pp and interactions at other energies. The test of factorization at the p → pπ+π? vertex is well verified. The process is studied and the cross sections of production are also given. 相似文献
16.
I.O. Kulik 《Physics letters. A》1984,106(4):187-190
For metals with small electron and phonon mean free paths (alloys, deformed or amorphous materials), there exists a possibility of determining α2F(ω) by measuring the V dependence of or of wide (d ? 103 Å) point contacts (PC) and then inverting the linear equation relating these quantities to α2F(ω). The procedure is elaborated numerically and tested successfully for model electron-phonon interaction spectra. 相似文献
17.
E. Eisenhandler W.R. Gibson C. Hojvat P.I.P. Kalmus L.C.Y. Lee Chi Kwong T.W. Pritchard E.C. Usher D.T. Williams M. Harrison W.H. Range M.A.R. Kemp A.D. Rush J.N. Woulds G.T.J. Arnison A. Astbury D.P. Jones A.S.L. Parsons 《Physics letters. [Part B]》1974,49(2):201-204
We present Legendre coefficients from fits to the differential cross-sections for in the momentum range 0.8 to 2.4 GeV/c. The s-dependence of the cross-sections at small angles is examined for evidence of Reggeized baryon exchange, and a fit made to this channel and backward K+p elastic scattering. Comparisons are made with . 相似文献
18.
《Physics letters. A》2003,280(2-3):127-130
We study the lowest energy E of a semirelativistic system of N identical massless bosons with Hamiltonian We prove where A=2.33810741 and . The average of these bounds determines E with an error less than 0.15% for all N⩾2. 相似文献
19.
We consider semi-inclusive reactions of the type p + p → (particle with large pT) + n charged particles + neutrals, and propose the following scaling law for the distribution function of the large-pT particle produced in association with n charged particles. This scaling rule is shown to be consistent with present information on single-particle spectra and average associated multiplicities at large pT. Also, we show that if the associated multiplicity were to continue to increase linearly with pT, then moments of the multiplicity distribution would increase like powers of s. 相似文献
20.
The complex polar Kerr effect (rotation and ellipticity) of magnetite single crystals has been measured at room temperature between 0.5 and 4.3 eV. From the magneto-optical data and the optical constants, the off-diagonal elements (?xy) of the dielectric tensor has been derived. Three well separated magneto-optical transitions have been indentified. At about 0.75 eV one strong magneto-optical structure with a diamagnetic line shape is assigned to a transition from Fe2+ in octahedral sites. Two other structures with paramagnetic line shapes near 1.85 and 2.90 eV are assigned to the orbital promotion processes and , respectively, which take into account Fe 3dn?1 final state effects. 相似文献