共查询到20条相似文献,搜索用时 62 毫秒
1.
H. Ackermann T. Azemoon W. Gabriel H.D. Mertiens H.D. Reich G. Specht F. Janata D. Schmidt 《Nuclear Physics B》1978,137(3):294-300
We report on an experiment where the different contributions from the transverse and longitudinal polarization of the virtual photon are measured separately for the reaction e?p→e?π+n. The data taken above the resonance region at small ∣t∣ values in the q2 range of ∣q2∣ < 0.5 GeV2 show a clear dominance of the longitudinal part of the cross section and are well described by a generalized Born-term model. Using this model the electromagnetic form factor of the pion is determined. At q2 = ?0.35 GeV2 one gets Fπ = 0.598 ± 0.021. 相似文献
2.
S. Cittolin F. Gasparini S. Limentani P. Mittner M. Posocco C. Voci J. Chauveau M. Crozon A. Diaczek B. Lefievre P. Leruste J. Mas R. Sené J. Tocqueville 《Nuclear Physics B》1979,157(2):197-211
The cross section for the KL0p elastic scattering has been measured for the first time. The incident momentum and momentum transfer ranges are 3 ?p? 13 GeV/c, 0.1 ? |t| ? 1.3 GeV2. The results are compared to those of other experiments related to ours by isotopic spin conservation, finding agreement with some and discrepancies with others. The differential cross sections have been parametrized in the form Aebt. The coefficients show little or no dependence on energy, with A ? 9.8 mb · GeV?2and b ? 4.7 GeV?2. The effective linear trajectory has been determined and gives α0 = 0.95 ± 0.15, α′ = ?0.35 ± 0.48 GeV?2, in good agreement with dominance by pomeron exchange. 相似文献
3.
Based on the field-theory-inspired approach, a new expression for the pion form factor F π is proposed. It takes into account the pseudoscalar meson loops π+π? and $K\bar K$ and the mixing of ρ(770) with heavier ρ(1450) and ρ(1700) resonances. The expression ensures correct analytical properties and describes the data in the wide range of the energy squared ?10 GeV2 ≤ s ≤ 1 GeV2 without introducing the phenomenological Blatt-Weisskopf range parameter R π. 相似文献
4.
Y. Eisenberg B. Haber U. Karshon J. Mikenberg S. Pitluck E.E. Ronat A. Shapira G. Yekutieli 《Physics letters. [Part B]》1974,48(4):354-358
In a high statistics experiment a large dσ/dt′ slope of (23.7 ± 3.2) GeV?2 is obtained in the forward direction. The natural parity exchange cross-section shows a dip at t′ ≈ 0.2 GeV2 and peak at ≈ 0.6 GeV2. The ?o is separated from the S-wave background and we obtain ?00F ≈ 0.94, at t′ = 0. 相似文献
5.
Yu. Arestov A. Borovikov E. Kozlovsky A. Minaenko A. Moiseev C. Cochet D. Denegri C. Lewin M. A. Turluer U. Gensch H. J. Grabosch W. Lohmann J. MacNaughton France-USSR Collaboration CERN-USSR Collaboration 《Zeitschrift fur Physik C Particles and Fields》1981,8(4):283-289
New data on the inclusive production of the non-strange resonances ?0(770), ω(783), ?(1020) andf(1270) inK ? p interactions at 32 GeV/c are presented. The inclusive production cross sections are equal to (4.32±0.72) mb, (3.7±1.4) mb, (0.65±0.10) mb and (0.91±0.35) mb respectively. Estimates of the topological cross sections are also obtained. The invariant and non-invariantx-distributions for the vector mesons ?0 and ? indicate the prevalence of forward resonance production in the c.m. system. For the tensorf-meson the rapidity andx-distributions are presented. Thet′-distributions for ?0, ?, andf have exponential slopes of 0.6±0.1 GeV?2, 1.2±0.2 GeV?2, and 0.8±0.5 GeV?2 respectively. The exponential slope ofp T 2 -distribution of thef-meson is equal to (2.3±0.5) GeV?2. 相似文献
6.
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
7.
M. Bernardini D. Bollini P.L. Brunini E. Fiorentino T. Massam L. Monari F. Palmonari F. Rimondi A. Zichichi 《Physics letters. [Part B]》1973,46(2):261-264
The study of 620 hadron pairs produced in the s-range (1.44?9.0) GeV2, has yielded 110 collinear hadronic events. Their identification in terms of π and K mesons allows the determination of the time-like electromagnetic from factors of these pseudoscalar mesons in the above time-like range. The total number of (e+e?) events observed in the same experimental conditions is 18 048. 相似文献
8.
9.
We analyse the unitarity equation in impact-parameter space using recent ISR data (at s=930 GeV2) on σT, dσ/dt (elastic) and d2σ/dtdM2 (diffractive) as input. The assumption of s-channel helicity conservation for the diffractive process leads to a diffractive overlap function which is central. Unitarity then restricts single diffraction to satisfy 2σd?5.8 mb. The assumption of t-channel helicity conservation, on the other hand, gives the interesting result that diffractive processes are peripheral in b-space if the diffractively produced state has high spin. Unitarity in this case gives no significant bound on 2σd. For both cases, non-diffractive processes are peripheral. 相似文献
10.
We propose a two-component inflation model, based on maximally symmetric supergravity, where the scales of reheating and the inflation potential at the origin are decoupled. This is possible because of the second-order phase transition from SU(5) to SU(3)×SU(2)×U(1) that takes place when φ?φc<φ0, when φ0?O(M) is the value of the inflation at the global minimum, and leads to a reheating temperature TR?(1015–1016) GeV. This makes it possible to generate baryon asymmetry in the conventional way without any conflict with experimental data on proton lifetime. The mass of the gravitinos is , thus avoiding the gravitino problem. Monopoles are diluted by residual inflation in the broken phase below the cosmological bounds if φc?0.3M. 相似文献
11.
M. Bernardini D. Bollini P.L. Brunini E. Fiorentino T. Massam L. Monari F. Palmonari F. Rimondi A. Zichichi 《Physics letters. [Part B]》1973,44(4):393-396
The observation of 21 K+K? pairs in 38 hadron pair events produced at 1.5, 1.6, and 1.7 GeV total centre-of-mass energies in e+e? annihilations, establishes that time-like photons produce K pairs and π pairs with comparable rates in this energy range. The K-meson electromagnetic form factor at a mean s-value of 2.4 GeV2 is measured to be |FK| = 0.50±0.08. The number of e+e? pairs observed in the same angular and energy range is 5148. 相似文献
12.
P. Joos A. Ladage H. Meyer P. Stein G. Wolf S. Yellin C.K. Chen J. Knowles D. Martin J.M. Scarr I.O. Skillicorn K. Smith C. Benz G. Drews D. Hoffmann J. Knobloch W. Kraus H. Nagel K. Wacker 《Nuclear Physics B》1976,113(1):53-92
The reaction γVp → pπ+π? was studied in the W, Q2 region 1.3–2.8 GeV, 0.3–1.4 GeV2 using the streamer chamber at DESY. A detailed analysis of rho production viaγVp→?0p is presented. Near threshold rho production has peripheral and non-peripheral contributions of comparable magnitude. At higher energies (W > 2 GeV) the peripheral component is dominant. The Q2 dependence of σ(γVp→?0p) follows that of the rho propagator as predicted by VDM. The slope of dσ/dt at 〈Q2〉 = 0.4 and 0.8 GeV2 is within errors equal to its value at Q2 = 0. The overall shape of the ?0 is t dependent as in photoproduction, but is independent of Q2. The decay angular distribution shows that longitudinal rhos dominate in the threshold region. At higher energies transverse rhos are dominant. Rho production by transverse photons proceeds almost exclusively by natural parity exchange, σTN ? (0.83 ± 0.06) σT for 2.2 < W < 2.8 GeV. The s-channel helicity-flip amplitudes are small compared to non-flip amplitudes. The ratio R = σL/σT was determined assuming s-channel helicity conservation. We find R = ξ2Q2/M?2 with ξ2 ≈ 0.4 for 〈W〉 = 2.45 GeV. Interference between rho production amplitudes from longitudinal and transverse photons is observed. With increasing energy the phase between the two amplitudes decreases. The observed features of rho electroproduction are consistent with a dominantly diffractive production mechanism for W > 2 GeV. 相似文献
13.
Recently available differential cross section and density matrix information on π?p → B?p at 4 GeV/c are successfully described in terms of t channel exchanges and s channel absorptive effects. The s channel helicity amplitude which is dominant at small |t| (zero net helicity flip ω exchange) is found to have a zero at ?t = 0.2 GeV2. SU(3) and higher symmetries are used to predict cross sections for further axial vector meson production processes, in particular non-diffractive A1 production. The importance of these processes with regard to Regge phenomenology and meson spectroscopy is emphasized. 相似文献
14.
15.
We apply vacuum background fields method to correct the coefficient functions of theO + andO ? operators in ΔS=1 effective weak Hamiltonian responsible forK→2π decays. The additional relative octet enhancement factor of 2–3 is obtained by accounting for the gluon condensate corrections if the scale parameterπ 2x is set below 1 GeV2. 相似文献
16.
C.E.W. Ward I. Ambats A. Lesnik W.T. Meyer D.R. Rust D.D. Yovanovitch 《Physics letters. [Part B]》1974,48(5):471-473
We have measured the Λ° polarization in π?p→ K°Λ° at 5 GeV/c, using a data sample of 3709 events. The polarization is positive for small t, passes through zero near t = ?0.3 (GeV/c)2, and becomes large and negative at larger t, consistent with a value of ?1.0 for t between ?0.7 and ?1.6(GeV/c)2. 相似文献
17.
J.-C. Alder H. Behrens F.W. Brasse W. Fehrenbach J. Gayler S.P. Goel R. Haidan V. Korbel J. May M. Merkwitz 《Nuclear Physics B》1975,99(1):1-12
Results on the reaction ep→e′nπ+ are presented in the mass range 1.355 ?W ?1.775 GeV at q2=1GeV2 and in the range 1.415 ? W ? 1.595 GeV at q2=0.6 GeV2. From the angular distribution of the π+ meson the polarization terms σu + ?σL, σp and σI have been determined in the range of production angles 0 <θπ+ ?63° 相似文献
18.
D.P. Barber U. Becker H. Benda A. Boehm J.G. Branson J. Bron D. Buikman J. Burger C.C. Chang H.S. Chen M. Chen C.P. Cheng Y.S. Chu R. Clare P. Duinker G.Y. Fang H. Fesefeldt D. Fong R.Y. Zhu 《Physics letters. [Part B]》1979,85(4):463-466
We report on the results of the study of e+e? collisions at the highest PETRA energy of √s = 31.57 GeV, using the 4π sr, electromagnetic and calorimetric detector Mark J. Based on 88 hadron events, and an integrated luminosity of 243 nb?1 we obtain R = σ(e+e? → hadrons)/σ(e+e? → μ+μ?) = 4.0 ± 0.5 (statistical) ± 6 (systematic). The R value, the measured thrust distribution and average spherocity show no evidence for the production of new quark flavors. 相似文献
19.
N. Arteaga-Romero C. Marimalo P. Kessler S. Ong J. Silva 《Zeitschrift fur Physik C Particles and Fields》1986,32(1):105-111
In the context of a measurement recently performed by the PLUTO Collaboration at PETRA, we have computed the contribution of 2-jet, 3-jet and 4-jet production processes (each involving 2 large-p T jets) in γγ* collisions to the differential cross sectiondσ/(dp T dQ 2), whereQ 2 is the γ*'s four momentum squared. It results that the total correction to the 2-jet contribution \(\left( {\gamma \gamma ^ * \to q\bar q} \right)\) , obtained forp T andQ 2 values located in the range 2 GeV<p T <6 GeV and 0.1 GeV2<Q 2<12 GeV2 varies rather slowly as a function of those two parameters; it ranges between 30% and 70%. The specific contribution of the higher twist term involving the process \(\gamma \gamma ^ * \to Mq\bar q\) appears to be insignificant. The discrepancy observed between experiment and theory atQ 2?0.3 GeV2 andp T ?2-3.5 GeV is not explained by our results. 相似文献
20.
S. Cittolin F. Gasparini M. Goldin S. Limentani P. Mittner M. Posocco C. Voci C. Aubret T. Bunaciu J. Chauveau M. Crozon A. Diaczek B. Lefievre P. Leruste J. Mas J. Tocqueville 《Nuclear Physics B》1978,142(4):410-444
We present experimental data on the KL0p → KS0p reaction between 4 and 14 GeV/c in the range 0.1 ? |t| ? 2 GeV2. This experiment has been performed at the CERN PS, using spark chambers and a large aperture magnet. The results show a break of slope at t = ?0.3 GeV2. The ω trajectory deduced from the data has an intercept α(0) = 0.5 and a slope α′ = 0.88. A comparison with various models shows that the non-flip amplitude is dominant. 相似文献