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1.
S. Abd El-Bary S. Abd El-Samad R. Bilger K. -Th. Brinkmann H. Clement M. Dietrich E. Doroshkevich S. Dshemuchadse K. Ehrhardt A. Erhardt W. Eyrich A. Filippi H. Freiesleben M. Fritsch R. Geyer A. Gillitzer C. Hanhart J. Hauffe K. Haug D. Hesselbarth R. Jaekel B. Jakob L. Karsch K. Kilian H. Koch J. Kress E. Kuhlmann S. Marcello S. Marwinski R. Meier K. Möller H. P. Morsch L. Naumann J. Ritman E. Roderburg P. Schönmeier M. Schulte-Wissermann W. Schroeder M. Steinke F. Stinzing G. Y. Sun J. Wächter G. J. Wagner M. Wagner U. Weidlich A. Wilms P. Wintz S. Wirth G. Zhang P. Zupranski 《The European Physical Journal A - Hadrons and Nuclei》2008,37(3):267-277
The two-pion production reaction pp → ppπ+π− was measured with a polarized proton beam at T
p
≈ 750 and 800MeV using the short version of the COSY-TOF spectrometer. The implementation of a delayed-pulse technique for
Quirl and central calorimeter provided positive π+ identification in addition to the standard particle identification, energy determination as well as time-of-flight and angle
measurements. Thus all four-momenta of the emerging particles could be determined with 1–4 overconstraints. Total and differential
cross-sections as well as angular distributions of the vector analyzing power have been obtained. They are compared to previous
data and theoretical calculations. In contrast to predictions we find significant analyzing-power values up to A
y
= 0.3. The data taken in the energy region of the excitation of the Roper resonance confirm that its dominant ππ decay channel
is N
* → Nσ. 相似文献
2.
3.
H. Müller 《The European Physical Journal A - Hadrons and Nuclei》2001,11(1):113-119
We investigate the reaction pp↦da
0
+ at COSY and SIS energies together with accompanying background reactions and inclusive particle yields. The a
0
+ is considered as a usual u
quark model state with two decay channels a
0
+↦K
+
and a
0
+↦π+η. Calculated cross-sections for a
0
+ production as well as for the corresponding non-resonant channels pp↦dK
+
and pp↦dπ+η are compared. Especially, in case of the final channel dπ+η, high statistics measurements are necessary to extract the a
0
+ signal from the high non-resonant background.
Received: 20 December 2000 / Accepted: 7 May 2001 相似文献
4.
T. Skorodko M. Bashkanov D. Bogoslawsky H. Calen F. Cappellaro H. Clement L. Demiroers E. Doroshkevich D. Duniec C. Ekström K. Franssen L. Gustafsson B. Höistad G. Ivanov M. Jacewicz E. Jiganov T. Johansson O. Khakimova M. Kaskulov S. Keleta I. Koch F. Kren S. Kullander A. Kupść A. Kuznetsov P. Marciniewski R. Meier B. Morosov C. Pauly H. Petterson Y. Petukhov A. Povtorejko K. Schönning W. Scobel B. Shwartz V. Sopov J. Stepeniak P. Thörngren-Engblom V. Tikhomirov G. J. Wagner M. Wolke A. Yamamoto J. Zabierowski J. Złomanczuk 《The European Physical Journal A - Hadrons and Nuclei》2008,35(3):317-319
In most investigations the Roper resonance is sensed only very indirectly via complex partial-wave analyses. We find indications
for its excitation in the invariant nπ+ mass spectrum of the pp → npπ+ reaction at M ≈ 1360 MeV with a width of ≈ 150 MeV . The values fit very favorably to the most recent phase shift results as well as to
the observations at BES. In the near-threshold two-pion production pp → ppπ0π0 , where the Roper excitation and its subsequent decays via the routes N
* → Δπ → Nππ and N
* → Nσ are the only dominant processes, we find its direct decay into the Nσ channel to be the by far dominating decay process --in favor of a monopole excitation of the Roper resonance. 相似文献
5.
P. V. Fedorets M. Büscher V. P. Chernyshev S. N. Dymov V. Yu. Grishina C. Hanhart M. Hartmann V. Hejny V. Kleber H. R. Koch L. A. Kondratyuk V. P. Koptev A. E. Kudryavtsev P. Kulessa S. I. Merzliakov S. M. Mikirtychiants M. E. Nekipelov H. Ohm R. Schleichert H. Ströher V. E. Tarasov K. -H. Watzlawik I. Zychor 《Physics of Atomic Nuclei》2006,69(2):306-313
The reaction pp → dπ
+
η has been measured at a beam energy of T
p
= 2.65 GeV (p
p
= 3.46 GeV/c) using the ANKE spectrometer at COSY-Julich. The missing-mass distribution of the detected dπ
+ pairs exhibits a peak around the η mass on top of a strong background of multipion pp → dπ
+(nπ) events. The differential cross section d
4
σ/dΩd
dΩ
π
+
dp
d
dp
π
+ for the reaction pp → dπ
+
η has been determined model independently for two regions of phase space. Employing a dynamical model for the a
0
+
production allows one then to deduce a total cross section of σ(pp → da
0
+
→ dπ
+
η) = 1.1 ± 0.3stat ± 0.7syst μb for the production of π
+
η via the scalar a
0
+
(980) resonance and σ(pp → dπ
+
η) = 3.5 ± 0.3stat ± 1.0syst μb for the nonresonant production. Using the same model as for the interpretation of recent results from ANKE for the reaction
, the ratio of the total cross sections is
, which is in agreement with branching ratios in the literature.
The text was submitted by the authors in English. 相似文献
6.
7.
V.Yu. Grishina L.A. Kondratyuk E.L. Bratkovskaya M. Büscher W. Cassing 《The European Physical Journal A - Hadrons and Nuclei》2000,9(2):277-285
We investigate the reactions πN↦a
0
N and pp↦da
0
+ near threshold and at medium energies. An effective Lagragian approach and the Regge pole model are applied to analyze different
contributions to the cross-section of the reaction πN↦a
0
N. These results are used to calculate the differential and total cross-sections of the reaction pp↦da
0
+ within the framework of the two-step model in which two nucleons produce an a0-meson via π-meson exchange and fuse to a deuteron. The necessity of new measurements on a0 production and branching fractions (of its decay to the K
and πη channels) is emphasized for clarifying the a0 structure. Detailed predictions for the reaction pp→da
0
+ are presented for the energy regime of the proton synchrotron COSY-Jülich.
Received: 4 August 2000 / Accepted: 17 September 2000 相似文献
8.
L. Roca C. Hanhart E. Oset U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2006,27(3):373-380
The Λ(1520)-resonance has been recently studied in a unitarized coupled-channel formalism with πΣ(1385), KΞ(1530), ˉN and πΣ as constituents blocks. We provide a theoretical study of the predictions of this model in physical observables of
the pp → pK+K-p and pp → pK+π0π0Λ reactions. In particular, we show that the ratio between the π0π0Λ and K-p mass distributions can provide valuable information on the ratio of the couplings of the Λ(1520)-resonance to πΣ(1385) and
ˉN than the theory predicts. Calculations are done for energies which are accessible in an experimental facility like COSY at
Jülich or the developing CSR facility at Lanzhou. 相似文献
9.
B.M. Abramov S.A. Bulychjov A.I. Khanov Y.S. Krestnikov A.P. Krutenkova V.V. Kulikov M.A. Matsyuk I.A. Radkevich A.I. Sutormin E.N. Turdakina 《The European Physical Journal A - Hadrons and Nuclei》1998,1(2):115-116
We report on our measurement of the inclusive spectrum of positive pions from the reaction pp→π++X on a CH
2 internal target of the ITEP proton synchrotron at 1.5 GeV/c with a missing mass resolution of about 1 MeV/c2. The goal of our experiment was the search for the hypothetical narrow πNN resonance (0.5\ MeV/c2 width and a mass of 2.06\ GeV/c2) with I(J
P
P)=even(0−), called d′. We do not see any statistically significant d′-signal. The upper limit for d′ production cross-section in pp-interactions is near 2μb at 84%C.L.
Received: 5 November 1997 相似文献
10.
V. V. Balashov V. K. Dolinov 《The European Physical Journal A - Hadrons and Nuclei》2008,37(1):97-110
An extended set of observables of the nuclear quasi-free (p, dπ+) reaction including the triple differential cross-section for coincidence measurements, its analyzing power in case of polarized
proton beams and, also, the parameters of the polarization of the excited recoil nucleus and the produced deuteron are considered
in the framework of the distorted-wave impulse approximation using the reaction 16O(p, dπ+)15N at a proton energy of 650 MeV as an example. The calculations show a high sensitivity of the differential cross-section
and, especially, of the polarization transfer characteristics of the reaction to the spin-multipole decomposition of the amplitude
of the basic two-body pp → dπ+ process. 相似文献
11.
《The European Physical Journal A - Hadrons and Nuclei》2008,35(3):333-342
The exclusive reactions γp → K
*0Σ+(1189) and γp → K
0π0Σ+(1189) , leading to the p 4π0 final state, have been measured with a tagged photon beam for incident energies from threshold up to 2.5GeV. The experiment
has been performed at the tagged photon facility of the ELSA accelerator (Bonn). The Crystal Barrel and TAPS detectors were
combined to a photon detector system of almost 4π geometrical acceptance. Differential and total cross-sections are reported.
At energies close to the threshold, a flat angular distribution has been observed for the reaction γp → K
0π0Σ+ suggesting dominant s -channel production. Σ*(1385) and higher-lying hyperon states have been observed. An enhancement in the forward direction in the angular distributions
of the reaction γp → K
*0Σ+ indicates a t -channel exchange contribution to the reaction mechanism. The experimental data are in reasonable agreement with recent theoretical
predictions. 相似文献
12.
E. Oset J.A. Oller U.-G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2001,12(4):435-446
We perform a study of the final-state interactions of the K
+
and the
d systems in the reactions pp↦dK
+
and pp↦dπ+η. Since the two-meson system couples strongly to the a
0(980) resonance, these reactions are expected to be an additional source of information about the controversial scalar sector.
We also show that these reactions present peculiar features which can shed additional light on the much debated meson-baryon
scalar sector with strangeness -1. We deduce the general structure of the amplitudes close to the dK
+
threshold, allowing for primary K
+
as well as π+η production with the two mesons in relative S- or P-wave. The interactions of the mesons are accounted for by using chiral unitary techniques, which generate dynamically the
a
0(980) resonance, and the
d interaction is also taken into account. General formulae are derived that allow to incorporate the final-state interactions
in these systems for any model of the production mechanism. We illustrate this approach by considering two specific production
mechanisms based on three flavor meson-baryon chiral perturbation theory. It is demonstrated that in this scenario the
d interactions are very important and can change the cross-section by as much as one order of magnitude. The amount of π+ηversus
K
+
production is shown to depend critically on the primary mixture of the two mechanisms, with large interference effects due
to final-state interactions. These effects are also shown to occur in the event distributions of invariant masses which are
drastically modified by the final-state interactions of the two-meson or the
d system.
Received: 28 September 2001 / Accepted: 26 November 2001 相似文献
13.
K. N. Ermakov V. I. Medvedev V. A. Nikonov O. V. Rogachevsky A. V. Sarantsev V. V. Sarantsev S. G. Sherman 《The European Physical Journal A - Hadrons and Nuclei》2011,47(12):159
The detailed investigation of the single pion production reactions pp → pnπ and pp → ppπ at the incident proton momentum 1628 MeV/c has been carried out. The data are analyzed in the framework of the event-by-event maximum-likelihood method together with
the pp → ppπ
0 data measured earlier in the energy region below 1 GeV. At 1628 MeV/c the largest contributions stem from the 3
P
2, 3
P
1, 3
P
0, 1
D
2 and 3
F
2 initial partial waves. 相似文献
14.
A. Dzyuba V. Kleber M. Büscher V. P. Chernyshev S. Dymov P. Fedorets V. Grishina C. Hanhart M. Hartmann V. Hejny L. Kondratyuk V. Koptev P. Kulessa Y. Maeda T. Mersmann S. Mikirtychyants M. Nekipelov D. Prasuhn R. Schleichert A. Sibirtsev H. J. Stein H. Ströher I. Zychor 《The European Physical Journal A - Hadrons and Nuclei》2006,29(2):245-251
The reaction pp → dK
+ˉ has been investigated at excess energies Q = 47.4 and 104.7MeV above the K
+ˉ threshold at COSY Jülich. Coincident dK+ pairs were detected with the ANKE spectrometer, and subsequently ∼ 2000 events with a missing ˉ invariant mass were identified,
which fully populate the Dalitz plot. The joint analysis of invariant mass and angular distributions reveals s-wave dominance between the two kaons, in conjunction with a p-wave between the deuteron and the kaon pair, i.e.
Kˉ production via the a
0
+(980) channel. Integration of the differential distributions yields total cross-sections of σ(pp → dK
+ˉ) = (38±2stat±14syst)nb and (190±4stat±39syst)nb for the low and high Q value, respectively. 相似文献
15.
A. P. Serebrov 《JETP Letters》1996,63(1):1-6
It is shown that a two-step model of the reaction pd→3HeX (X=η, η′ eω, φ), involving the subprocesses pp) →dπ+ and π+
n→Xp, can account for the form of the energy dependence of experimental cross sections above the thresholds under the assumption
that the singlet part of the pp→dπ+ amplitude dominates. The spin-spin asymmetry for the reaction dp→3HeX has been found to be ∼;−1 in the forward-backward approximation.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 1, 3–7 (10 January 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
16.
V. Bernard N. Kaiser Ulf-G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》1999,4(3):259-275
We evaluate the threshold matrix–element for the reaction pp→ppπ0 in a fully relativistic Feynman diagrammatic approach. We employ a simple effective range approximation to take care of the
S–wave pp final–state interaction. The experimental value for the threshold amplitude A = (2.7 −i0.3) fm4 can be reproduced by contributions from tree level chiral (long–range) pion exchange and short–range effects related to vector
meson exchanges, with ω-exchange giving the largest individual contribution. Pion loop effects appear to be small. We stress
that the commonly used heavy baryon formalism is not applicable in the NN–system above the pion production threshold due to
the large external momentum, |p|≃ (Mm
π)−1/2, with M and m
π the nucleon and the pion mass, respectively. We furthermore investigate the reaction pp→pnπ+ near threshold within the same approach. We extract from the data the triplet threshold amplitude as B = (2.8 −i1.5) fm4. Its real part can be well understood from (relativistic) tree level meson–exchange diagrams. In addition, we investigate
the process pp→ppη near threshold. We use a simple factorization ansatz for the ppη final–state interaction and extract from the data the modulus of the threshold amplitude, |C|= 1.32 fm4. With g
ηN= 5.3, this value can be reproduced by (relativistic) tree level meson–exchange diagrams and η–rescattering, whose strength
is fixed by the ηN scattering length. We also comment on the recent near threshold data for η′–production.
Received: 27 November 1998 相似文献
17.
A. Sibirtsev J. Haidenbauer H. -W. Hammer U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2006,29(3):363-367
We show that the recently measured asymmetry in helicity-angle spectra of the Λ-hyperons, produced in the reaction pp → K
+Λp reaction, and the energy dependence of the total pp → K
+Λp cross-section can be explained consistently by the same Λp final-state interaction. Assuming that there is no final-state interaction in the Σ0
p channel, as suggested by the available data for the reaction pp → K
+Σ0
p, we can also reproduce the energy dependence of the Λ/Σ0 production ratio and, in particular, the rather large ratio observed near the reaction thresholds. The nominal ratio of the
Λ and Σ0 production amplitudes squared, i.e. when disregarding the final-state interaction, turns out to be about 3, which is in line with hyperon production data from
proton and nuclear targets available at high energies. 相似文献
18.
Rescattering corrections to the impulse approximation for the processes γd → π
0
d and π
−
d → π
−
d are discussed. It is shown that the rescattering effects give a nonnegligible contribution to the real part of these amplitudes.
At the same time, the contributions from the imaginary parts of impulse and rescattering corrections drastically cancel each
other. This cancellation means that the processes π
−
d → π
0
nn and γd → π
+
nn/π
−
pp, when the nucleon pair is in the spin triplet state, are strongly suppressed near threshold as required by the Pauli principle.
From Yadernaya Fizika, Vol. 67, No. 4, 2004, pp. 764–768.
Original English Text Copyright ? 2004 by Baru, Kudryavtsev, Tarasov.
This article was submitted by the authors in English. 相似文献
19.
V. Lensky V. Baru E. Epelbaum C. Hanhart J. Haidenbauer A. Kudryavtsev U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2007,33(4):339-348
We discuss the possibility to extract the neutron-neutron scattering length ann from experimental spectra on the reaction γd → π+
nn . The transition operator is calculated to high accuracy from chiral perturbation theory. We argue that for properly chosen
kinematics, the theoretical uncertainty of the method can be as low as 0.1 fm. 相似文献
20.
N. Kaiser 《The European Physical Journal A - Hadrons and Nuclei》1999,5(1):105-110
We analyze the recent total cross section data for pp→pΛK
+ near threshold measured at COSY. Using an effective range approximation for the on-shell pΛ S-wave final state interaction we extract from these data the combination ?= (2|K
s|2+|K
t|2)−1/2= 0.38 fm4 of the singlet (K
s) and triplet (K
t) threshold transition amplitudes. We present an exploratory calculation of various (tree-level) vector and pseudoscalar meson
exchange diagrams. Pointlike ω-exchange alone and the combined (ρ0,ω,K*+)-exchange can explain the experimental value of ?. The pseudoscalar meson exchanges based on a SU(3) chiral Lagrangian turn
out to be too large. However, when adding π0-exchange in combination with the resonant πN→S
11(1650) →KΛ transition and introducing monopole form factors with a cut-off Λc= 1.5 GeV one is again able to reproduce the experimental value of ?. More exclusive measurements are necessary to reveal
the details of the pp→pΛK
+ production mechanism.
Received: 28 October 1998 / Revised version: 12 January 1999 相似文献