共查询到20条相似文献,搜索用时 12 毫秒
1.
M.N. Mineva M. Hellström M. Bernas J. Gerl H. Grawe M. Pfützner P.H. Regan M. Rejmund D. Rudolph F. Becker C.R. Bingham T. Enqvist B. Fogelberg H. Gausemel H. Geissel J. Genevey M. Górska R. Grzywacz K. Hauschild Z. Janas I. Kojouharov Y. Kopatch A. Korgul W. Korten J. Kurcewicz M. Lewitowicz R. Lucas H. Mach S. Mandal P. Mayet C. Mazzocchi J.A. Pinston Zs. Podolyàk H. Schaffner Ch. Schlegel K. Schmidt K. Sümmerer H.J. Wollersheim 《The European Physical Journal A - Hadrons and Nuclei》2001,11(1):9-13
Rapidity correlations in 800 GeV proton interactions with emulsion nuclei are investigated for different targets and multiplicity
regions. To study the energy dependence, the results have been compared with proton interactions at 200 GeV and 400 GeV. A
common feature of all the interactions is the existence of strong, short-range correlations. However, no dependence of cluster
parameters on primary energy or target mass is found. A marginal increase of correlation strength with multiplicity is observed.
Received: 30 March 2001 / Accepted: 18 September 2001 相似文献
2.
Namrata Ashutosh Bhardwaj Kirti Ranjan Sudeep Chatterji Ajay K. Srivastava V.K. Verma R.K. Shivpuri 《The European Physical Journal A - Hadrons and Nuclei》2002,13(4):405-410
Multiplicity distributions of charged particles produced in interactions of 800 GeV protons with emulsion nuclei in various
rapidity windows are presented. The data is also analyzed separately for the forward and the backward hemispheres, for rapidity
windows of different widths. It is found that the Negative Binomial Distribution (NBD) describes well the multiplicity distribution
of secondary particles in various rapidity windows and also in both the hemispheres. We have compared the NBD parameters,
in both the hemispheres, at 200 GeV and 360 GeV, with those at 800 GeV. The behaviour of NBD parameters in rapidity windows
of different widths and for different targets has also been studied.
Received: 30 August 2001 / Accepted: 28 January 2002 相似文献
3.
T. Renk 《The European Physical Journal A - Hadrons and Nuclei》2001,11(3):251-255
Following a prior analysis of measured pp elastic differential cross-sections, the impact parameter representation in terms of profile functions is calculated from
two different parametrizations of single diffractive dissociation data. The derivative of this quantity, with respect to the
collision energy squared s, measures the growth rate of the reaction's blackness. Its distribution in impact parameter space allows detailed insight
into the growth pattern of the total diffractive cross-section and the approaching unitarity limit. Comparing the results
with the elastic case, the different mechanisms of unitarization of two parametrizations are discussed.
Received: 19 January 2001 / Accepted: 11 July 2001 相似文献
4.
V. L. Lyuboshitz V. V. Lyuboshitz 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):465-467
The coherent inelastic processes of the type a→b, which may take place in the collisions of hadrons and γ-quanta with nuclei at very high energies (the nucleus remains the same), are theoretically investigated. The influence of
matter inside the nucleus is taken into account by using the optical model based on the concept of refraction index. Analytical
formulas for the effective cross-section σ
coh(a→b) are obtained, taking into account that at ultrarelativistic energies the main contribution into σ
coh(a→b) is provided by very small transferred momenta in the vicinity of the minimum longitudinal momentum transferred to the nucleus. 相似文献
5.
A. Sibirtsev K. Tsushima A.W. Thomas 《The European Physical Journal A - Hadrons and Nuclei》1999,6(3):351-359
We examine the production of open charm in antiproton annihilation on finite nuclei. The enhancement of the subthreshold
production cross section, even in a nucleus as light as carbon, should provide a clean signature of the reduction in the masses
of these mesons in-medium. We also show that a careful analysis of the D+ and D− spectra can yield important information on the cross section for D±N scattering.
Received: 10 June 1999 / Revised version: 13 August 1999 相似文献
6.
T. Osada O. V. Utyuzh G. Wilk Z. Wodarczyk 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(1-2):7-10
The extended Gaussian ensemble introduced recently as a
generalization of the canonical ensemble, which allows to treat energy
fluctuations present in the system, is used to analyze the inelasticity
distributions in high energy multiparticle production processes. 相似文献
7.
Ye.S. Golubeva W. Cassing L.A. Kondratyuk 《The European Physical Journal A - Hadrons and Nuclei》2002,14(2):255-263
We study the perspectives of resonant and nonresonant charmed-meson production in ˉp + A reactions within the Multiple Scattering Monte Carlo (MSMC) approach. We calculate the production of the resonances Ψ(3770),Ψ(4040)
and Ψ(4160) on various nuclei, their propagation and decay to D,ˉD, D
*,ˉD*, D
s,ˉDs in the medium and vacuum, respectively. The modifications of the open charm vector mesons in the nuclear medium are found
to be rather moderate or even small such that dilepton spectroscopy will require an invariant mass resolution of a few MeV.
Furthermore, the elastic and inelastic interactions of the open charm mesons in the medium are taken into account, which can
be related to (u, d )-, s- or c-quark exchange with nucleons. It is found that by studying the D/ˉD ratio for low momenta in the laboratory ( ? 2 - 2.2 GeV/c) as a function of the target mass A stringent constraints on the c-quark exchange cross-section can be obtained. On the other hand, the ratios D
-
s/D
+
s as well as D/D
-
s and D/D
+
s at low momenta as a function of A will permit to fix independently the strength of the s-quark exchange reaction in D
-
s
N scattering.
Received: 1 March 2002 / Accepted: 21 March 2002 相似文献
8.
W. Cassing Ye.S. Golubeva L.A. Kondratyuk 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):279-285
We study the possibility to measure the elastic ΦN (Φ≡J/ψ,ψ(2S), ψ(3770), χ2c) scattering cross section in the reaction ˉp+d→Φ+n
sp and the elastic D(ˉD)N scattering cross section in the reaction ˉp+d→D
−
D
0
p
sp. Our studies indicate that the elastic scattering cross sections can be determined for Φ momenta about 4–6 GeV/c and D/ˉD momenta 2–5 GeV/c by selecting events with p
t≥ 0.4 GeV/c for Φ's and p
t(p
sp) ≥ 0.5 GeV/c for D/ˉD-meson production.
Received: 8 November 1999 相似文献
9.
The phenomenological amplitude for the reaction πN→ππN fixed by fittings to the experimental data in the energy region 0.300 ≤P
Lab≤ 500 MeV/c is used for modelling the Chew–Low extrapolation and Olsson–Turner threshold approach. It is shown that the uncritical
application of the former results in enermous theoretical errors, the extracted values being in fact random numbers. The results
of the Olsson–Turner method are characterized by significant systematic errors coming from unknown details of the isobar physics.
Received: 10 December 1997 相似文献
10.
S. Barsov M. Büscher M. Hartmann V. Hejny A. Kacharava I. Keshelashvili A. Khoukaz V. Koptev P. Kulessa A. Kulikov I. Lehmann V. Leontyev G. Macharashvili Y. Maeda T. Mersmann S. Merzliakov S. Mikirtytchyants A. Mussgiller D. Oellers H. Ohm F. Rathmann R. Schleichert H. Seyfarth H. Ströher S. Trusov Yu. Valdau P. Wüstner S. Yaschenko C. Wilkin 《The European Physical Journal A - Hadrons and Nuclei》2007,31(1):95-104
The production of ω-mesons in the pp → ppω reaction has been investigated with the COSY-ANKE spectrometer for excess energies of 60 and 92MeV by detecting the two
final protons and reconstructing their missing mass. The large physical background was subtracted using an event-by-event
transformation of the proton momenta between the two energies. Differential distributions and total cross-sections were obtained
after careful studies of possible systematic uncertainties in the overall ANKE acceptance. The results are compared with the
predictions of theoretical models. Combined with data on the φ-meson, a more refined estimate is made of the Okubo-Zweig-Iizuka
rule violation in the φ/ω production ratio. 相似文献
11.
A.I. Titov B. Kämpfer B.L. Reznik 《The European Physical Journal A - Hadrons and Nuclei》2000,7(4):543-557
We analyze the production of φ mesons in πN and NN reactions in the near-threshold region, using throughout the conventional “non-strange” dynamics based on such processes
which are allowed by the non-ideal ω-φ mixing. We show that the occurrence of the direct φNN interaction may show up in different unpolarized and polarization observables in πN→Nφ reactions. We find a strong non-trivial difference between observables in the reactions pp→ppφ and pn→pnφ caused by the different role of the spin singlet and triplet states in the entrance channel. A series of predictions for
the experimental study of this effect is presented.
Received: 27 January 2000 相似文献
12.
Decays of neutral D-mesons are considered phenomenologically without invoking any particular models. Special attention is given to cascade decays
with intermediate neutral kaons where coherent double-flavour oscillations (CDFO) become possible. We show necessity and unique
possibilities of experiments on CDFO. They allow to relate with each other widths and masses of D-meson eigenstates, to separate interference effects due to D
0-ˉD
0 mixing and/or Cabibbo-favoured vs. doubly-suppressed transitions. Such experiments provide the only known ways to unambiguous
model-independent measurements of all CP-violating parameters and of Cabibbo-doubly-suppressed amplitudes, where the New Physics may have more prominent manifestations.
Similar experiments would be useful and interesting also for charged D-meson decays to neutral kaons.
Received: 13 August 1998 相似文献
13.
The spin structure of the matrix element for the pseudoscalar meson production processes in nucleon-nucleon collisions is
established in the collinear kinematical regime in terms of 3 independent scalar amplitudes. This result is valid for any
reaction mechanism and for any energy of the colliding and the produced particles. The complete experiment for the full reconstruction
of all 3 complex amplitudes must contain two different classes of polarization experiments. The polarization transfer coefficients
can be used to determine the moduli of all 3 amplitudes, whereas the spin correlation coefficients for + collisions are sensitive to the relative phases of different amplitudes.
Received: 13 August 2001 / Accepted: 20 September 2001 相似文献
14.
15.
The reaction pn↦dφ is studied within a covariant boson exchange model. The behavior of polarization observables being accessible in forthcoming
experiments near threshold is predicted.
Received: 13 February 2001 / Accepted: 25 March 2002 相似文献
16.
On the basis of the experimental data on diffractive processes in πp, pp and pˉp collisions at intermediate, moderately high and high energies, we restore the scattering amplitude related to the t-channel exchange by vacuum quantum numbers by taking account of the diffractive s-channel rescatterings. At intermediate and moderately high energies, the t-channel exchange amplitude turns, with a good accuracy, into an effective pomeron which renders the results of the additive
quark model. At superhigh energies the scattering amplitude provides a Froissart-type behaviour, with an asymptotic universality
of cross sections such as σtot
πp/σtot
pp→ 1 at s→∞. The quark structure of hadrons being taken into account at the level of constituent quarks, the cross sections of pion
and proton (antiproton) in the impact parameter space of quarks, σπ(r
1⊥, r
2⊥; s) and σp(r
1⊥, r
2⊥, r
3⊥; s), are found as functions of s. These cross sections implicate the phenomenon of colour screening: they tend to zero at |r
i⊥−r
k⊥|→ 0. The effective colour screening radius for pion (proton) is found for different s. The predictions for the diffractive cross sections at superhigh energies are presented.
Received: 15 December 1998 相似文献
17.
The isoscalar-isovector (ρ-ω) interferences in the exclusive reactions π-
p↦ne
+
e
- and π+
n↦pe
+
e
- near the ω threshold leads to a distinct difference of the dielectron invariant-mass distributions depending on beam energy.
The strength of this effect is determined by the coupling of resonances to the nucleon vector-meson channels and other resonance
properties. Therefore, a combined analysis of these reactions can be used as a tool for determining the baryon resonance dynamics.
Received: 14 August 2001 / Accepted: 3 October 2001 相似文献
18.
V. Hejny J. Weiß P. Achenbach J. Ahrens J.R.M. Annand R. Beck M. Kotulla B. Krusche V. Kuhr R. Leukel I.J.D. MacGregor V. Metag R. Novotny V. Olmos de León F. Rambo A. Schmidt M. Schumacher U. Siodlaczek H. Ströher F. Wissmann M. Wolf 《The European Physical Journal A - Hadrons and Nuclei》2002,13(4):493-499
The photoproduction of η-mesons from 2H and 4He has been studied for energies close to the production thresholds. The experiments were carried out with the tagged photon
beam of the Mainz MAMI accelerator. The η-mesons were detected via their two photon decays with the electromagnetic calorimeter
TAPS. Total cross-sections, angular and momentum distributions of the η-mesons have been determined for both reactions. The
total cross-sections in the threshold region show a large enhancement over the predictions of a participant-spectator model,
indicating significant final-state interaction effects. The results are compared to recent model calculations taking into
account nucleon-nucleon and nucleon-η final-state interaction effects on different levels of sophistication.
Received: 23 November 2001 / Accepted: 11 February 2002 相似文献
19.
A ππ, ˉKK, and ρρ(ωω) fully coupled channel model is used to predict the lowest isospin S, P, D, F-wave phase shifts and inelasticities
for elastic ππ scattering from threshold to 2.0 GeV. As input the S-matrix is required to exhibit poles corresponding to the
meson resonance table of the Particle Data Group. As expected, the ππ inelasticity is very strongly related to the opening
of the ˉK channel near 1 GeV, and the opening of ρρ(4π) and ωω(6π) channels in the 1.5 GeV region. The predictions of this model are
compared to the various elastic ππ→ππ amplitudes, that were obtained from analyses of π− p →π−π+n data. The role of the various resonances, in particular the glueball candidate f
0(1500) and the f
J(1710) is investigated.
Received: 19 November 1997 相似文献
20.
Shi-Lin Zhu 《The European Physical Journal A - Hadrons and Nuclei》1999,4(3):277-281
The light cone QCD sum rules are derived for the K
*
Kπ coupling g
K
*
Kπ and the ρππ coupling g
ρππ. The contribution from the excited states and the continuum is subtracted cleanly through the double Borel transform with
respect to the two external momenta, p
1
2, p
2
2= (p−q)2. Our result g
K
*
Kπ= (8.7 ± 0.5) and g
ρππ= (11.5 ± 0.8) is in good agreement with the experimental value.
Received: 31 July 1998 / Revised version: 20 November 1998 相似文献