共查询到20条相似文献,搜索用时 625 毫秒
1.
We have performed an isospin analysis of single-pion production processes in antiproton-nucleon scattering from threshold to 2.90 GeV/c. Reactions used are . Results show that σ1, the total I=1 cross section, rises rapidly from threshold to reach a broad maximum around 2.5 GeV/c and σ0, the I=0 cross section, rises from threshold and continues on a linearly rising trend at least up to 2.90 GeV/c. In the region of 2.9 GeV/c, σ1 and σ0 have comparable values, thus suggesting that considerable amount of and states is produced even in this low momentum region. We further determine that single pion production processes are not the source of the π0 (2375,190) enhancement observed in the and total cross sections and may account for as much as 25±8% of the π1 (2350,140) enhancement. 相似文献
2.
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
3.
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
4.
An empirical investigation of data provides evidence for a dynamical variable connected with the boundary of the physical region. Absence of a fixed u = ?0.2 dip in recent high-energy data disagrees with nucleon-exchange (N) line-reversal expectations from π+p→pπ+ backward scattering. We notice however that the π+p→pπ+ dip is not located at fixed u but remains with a surprising accuracy at a fixed distance u' = u ? umin from the physical boundary. Conjecturing that dips associated with particle exchanges occur at fixed u', we predict that the N-exchange dip in will be considerably displaced at non-asymptotic energies. Our conjecture places the fixed u' = ?0.2 dip near for momenta around 2 GeV/c. Folded distributions exhibit a dip structure at this location. These observations suggest that the failure of line reversal at low energies is due to direct-channel effects, since fixed u' dips occur naturally in geometrical and direct-channel models. 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.
J. Boucrot B. Bouquet B. DAlmage A. Ferrer A. Jacholkowski A. Lahellec P. Petroff P. Roudeau J. Six F. Navach P. Sonderegger D. Treille P. Rivet A. Volte P. Benkheiri G. de Rosny A. Rouge R. Salmeron H. Yoshida 《Nuclear Physics B》1977,121(2):251-269
Negative results on backward production, via baryon exchange, of exotic non-strange mesons are presented. The reactions π?p→pforwardX?and π?n→ pforwardX?? have been studied with a 12 GeV/cπ? beam in the Omega spectrometer at CERN. No resonant peak in has been seen. The upper limits obtained on cross sections for exotic meson production are lower than the ?? backward production cross section in the π?p→p?? reaction; this result seems to contradict the predictions of the two-component duality model. Compared to already published experiments in the search for exotics produced via baryon exchange, the sensitivity of this experiment is increased by an order of magnitude. 相似文献
7.
The one-electron momentum distribution function for an electron gas is investigated by a diagrammatic analysis of perturbation theory. It is shown that has the following exact asymptotic form for large k (k ? pF; pF, the Fermi momentum): , where g?(0) is the zero-distance value of the spin-up-spin-down pair correlation function. The physical implications of the above asymptotic form are discussed. 相似文献
8.
C. Evangelista B. Ghidini A. Palano V. Picciarelli G. Zito P. Mättig K. Müller E. Paul W. Rühmer B.R. French D.H. Miller W.A. Mitaroff C. Palazzi-Cerrina R. Strub A.S. Thompson P.L. Woodworth M. Edwards L. Pregernig 《Physics letters. [Part B]》1977,70(3):373-376
Inclusive production is studied in π?p interactions at 16 GeV/c with x? > 0.2. The is found to be pre-dominantly centrally produced with cross section for x? > 0.2 and compares closely to data on production in π+p interactions at the same energy. 相似文献
9.
K. Böckmann J. Hofmann U. Idschok J. Lowsky B. Schröder V. Blobel H. Fesefeldt R. Schulte G. Kellner D.R.O. Morrison H. Saarikko T. Coghen 《Nuclear Physics B》1980,166(2):284-300
A study is presented of the inclusive production cross sections of K1±(892) vector mesons in pp interactions at 12 and 24 GeV/c and in π+p interactions at 16 GeV/c. The K1± inclusive cross section is ~0.9 mb for both pp at 24 GeV/c and π+p interactions at 16 GeV/c. For pp interactions, and are seen to rise with energy, showing a threshold behaviour. In both pp and π+p interactions, largely exceeds at these energies and this excess is interpreted as K1+ production by beam and target fragmentations. The decays of K1±0 yield ~30% of the K0 observed in the final states. The pT2 dependence of both K1+ and K1? cross sections is described by an exponential with slope of ~3.3 (GeV/c)?2. The longitudinal momentum spectra for K1+ in 16 GeV/cπ+p and 24 GeV/c pp interactions are similar in shape in the target hemisphere. The K1? spectra are similar over the whole kinematic region when viewed in the quark c.m.s. and point to a central production mechanism. Comparing K1+ and ρ0 production, striking similarities are found. 相似文献
10.
D. Chultem V.S. Evseev V.M. Sidorov V.A. Khalkin R. Engfer H.H. Müller H.K. Walter 《Nuclear Physics A》1979,316(3):290-294
A search for the existence of the tetraneutron has been made using the double charge exchange reaction residuals for 4n production and the capture process in the same target, , for the 4n detection. No event has been found, giving an upper limit for the product of the production cross section σp, the detection cross section σd and the 4n lifetime τ. Assuming 10?18 ≦ τ ≦ 10?9 sec it follows that σpσdτ ≦ 2.5 × 10?65cm4 sec with 90 % confidence, and for with 90 % confidence. The magnitude of this value is comparable to the experimental limit of the 4He(π?, π+)4n cross section. 相似文献
11.
A.D. Krisch 《Physics letters. [Part B]》1973,44(1):71-75
The model assumes that when two high energy particles collide each behaves as a geometrical object which has a Gaussian density and is spherically symmetric except for the Lorentz-contraction in the incident direction. Folding the two spatial distribution together we obtain the slope (b) of the elastic diffraction peak in terms of the c.m. velocities (βi and βj) and the sizes (Ai and Aj) of the two incident particles. These sizes are assumed to have the experimental s-dependence of σtot ∝ πA2 for each reaction. The combined s-dependence of the σtot's and the β's gives the s-dependence of the elastic slope . This formula agrees with the experimental slope for p-p, -p, K+-p, K?-p and π±-p elastic scattering from 3 to 1500 GeV/c, with only 3 parameters: Aπ2 = 6.1, AK2 = 3.3 and Ap2 = 10.5 (GeV/c)?2. 相似文献
12.
Robert S. Mulliken 《Journal of Molecular Spectroscopy》1976,61(1):92-99
Predissociations in the y1Πg and Rydberg states of N2 (configurations and , respectively) and their likely causes, are discussed. Peaking of rotational intensity at unusually low J values, without sharp breaking off, is interpreted as due to case c? or case ci predissociation. Λ doubling in the y state, attributed to interactions with the state and with another, 1Σ+, state of the same electron configuration as x, is analyzed. From this analysis the location of the (unobserved) state, here labeled x′, is obtained. It is concluded that the predissociation in the Π+ levels of the y state is an indirect one mediated by the interaction with x′ coupled with predissociation of x′ by a state dissociating to atoms: combined, however, with perturbation of the y state by the k1Πg Rydberg state (configuration ), whose Π+ levels are completely predissociated. 相似文献
13.
Z. Strachman H. Braun J.P. Gerber G. Maurer A. Michalon B. Schiby R. Strub 《Nuclear Physics B》1975,98(1):120-136
A new approach to the t-channel isospin analysis of ZN → Z′(Nπ) reactions is presented. This approach, useful for when only five independent sets of data are availables, is used to analyse data of reactions obtained in a experiment at experiment at 5.5 GeV/c. the t behaviour of the different isospin exchange amplitudes, suggests their exchange mechanism production. The mass spectrum, MπN, of the contributions produced by exchanged isospin Iex = 1, shows enhancements corresponding to N(1490) N(1670) and Δ(1230) isobars, while the mass spectrum for Iex = 0 presents only a large bump at ~1350 MeV commonly identified as N1(1400). 相似文献
14.
K. Moriyasu T. Burnett D. Holmgren H.J. Lubatti D. Rees G. Swider B. Yuldashiev K. Dziunikowska A. Eskreys K. Eskreys A. Gula D. Kisielewska H. Rudnicka P. Stopa W. Ko R.L. Lander J.S. Pearson D. Pellett A. Zieminski 《Nuclear Physics B》1978,137(4):377-389
Double-scattering effects are studied in π?d interactions at 360 GeV/c. The partial cross sections are presented. The double-scattering probability per πd collision is found to be . We have extracted the partial cross section XN of the double-scattering plus interference contributions, and find that XN obeys KNO scaling. The data are compared with various theoretical predictions. 相似文献
15.
A. Berglund T. Buran P.J. Carlson C.J.S. Damerell I. Endo A.R. Gillman V. Gracco R.J. Homer M.J. Hotchkiss A. Lundby M. Macri B.N. Ratcliff A. Santroni T. Tso F. Wickens J.A. Wilson 《Nuclear Physics B》1978,137(3):276-282
The reaction has been studied at 10.1 GeV/c in the ?t interval from 0.15 to 1.5 (GeV/c)2. A line-reversal comparison with backward elastic scattering π+p → pπ+ shows good agreement for ?t > 0.3 (GeV/c)2. 相似文献
16.
Accurate SCF computations are reported on the Rydberg states of N2 of electron configurations , , and ---3σg2πg, also on the valence states of the configuration . The Rydberg state calculations supplement those of Lefebvre-Brion and Moser. A comparison is made between the states and the parallel set of states of the configuration. This comparison shows a sharp difference in the 1Σ+ states of the two configurations, the 1Σ+ state being very high in the latter but relatively low in the former configuration. Recknagel coefficients are given for the several states of the two configurations; as expected, these are much smaller for the configuration. Also, the 1Δ state is relatively lower for the latter configuration. 相似文献
17.
18.
Yu.M. Antipov G. Ascoli R. Baud R. Busnello G. Damgaard M.N. Kienzle-Focacci W. Kienzle R. Klanner L.G. Landsberg A.A. Lebedev C. Lechanoine P. Lecomte M. Martin V.N. Roinishvili R.D. Sard A. Snyder F.A. Yotch 《Nuclear Physics B》1975,99(2):189-210
The reaction has been studied at 25 and 40 GeV/c at the Serpukhov proton synchroton using the CERN-IHEP spectrometer. The differential cross section has been determined as a function of four-momentum transfer to the proton (0.05–0.30 (GeV/c)2) and mass (up to 2.2 and 2.6 GeV/c2). At both energies there is a broad low-mass maximum with an enhancement at 1.6–1.8 GeV/c2. The cross section in a given mass band falls rapidly with |t|, with an exponential slope that decreases with increasing mass. In both the background and the 1.7 GeV/c2 peak there is a strong component. Possible spin-parity (JP) contributions to it are discussed. Throughout the range 1.5–2.2 GeV there is at least one state of and there is interference between states of opposite P, |ΔJ| ? 1. At the peak there is a component. There are striking parallels between this reaction and the boson reactions π?p→π?π?π+p and K? → K?π?π+p. 相似文献
19.
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
20.
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