共查询到20条相似文献,搜索用时 46 毫秒
1.
M. Benayoun M. Feindt M. Girone A. Kirk Ph. Leruste J. -L. Narjoux K. Šafařík 《Zeitschrift fur Physik C Particles and Fields》1993,58(1):31-53
Motivated by nearly unanimous claim that the observed mass spectrum +- is not that expected from pure 0 dominance, we reanalyze all the published data on / +- decays. We find non-resonant contributions. In order to evaluate precisely the magnitude of these terms, we also refit the e+e- +- data to get reliably the 0 parameters and decay amplitude. We show that identifying the non-resonant contribution with the box anomaly predicted by QCD and chiral theories, one achieves a consistent picture. Several checks are performed which show the consistency of our fitted parameters. From four measurements, we determinef
1,f
8 and PS on purely experimental grounds, and we find them in the expected range. Presently available data allow for two solutions, one is consistent with QCD, the other favours integral charge quark models. We show that presently available data do not allow to choose among these two solutions. We discuss the interrelation of uncertainties in e+e- +- physics with our two solutions. 相似文献
2.
K. Karch D. Antreasyan H. W. Bartels D. Besset Ch. Bieler J. K. Bienlein A. Bizzeti E. D. Bloom I. Brock K. Brockmüller et al. 《Zeitschrift fur Physik C Particles and Fields》1992,54(1):33-44
The reactione
+
e
- e
+
e
- 00e
+
e
- 6 has been analysed using the full data sample taken with the Crystal Ball detector at the DORIS II storage ring at DESY. The 00 invariant mass spectrum is dominated by the ', for which we determine the radiative width (') to be (4.5±0.3±0.5)keV. Near 1.9 GeV/c2 we observe a second enhancement in the 00 mass distribution. Assuming that these events are created by the production and subsequent decay of a wide resonanceX(1900), we have investigated the decay modes, the invariant mass distributions of the 0 and 00 subsystems and the angular distributions of the final state mesons. We find that the data is best described byJ
PC=2. For thisJ
P assignment the resonance parameters are (X) BR(X)=(0.95±0.27±0.20) keV tot (X)=(221±92±44)MeV, andM(X)=(1881±32±40) MeV/c2.Deceased 相似文献
3.
Production of strange and charm particles by hadron-proton collisions is analyzed in terms of a fire-ball (FB) model assuming the multiplicity of secondaries of a given massm, to be proportional to the FB mass: n(m)M
*, the FB kinematics being determined by the Feynman-Yang scaling, as in the case of production. It is found that (m)1/m
2 and that, using this property together with the scaling, no-free-parameter fits to currently available data of strange and charm particles frompp and p collisions are satisfactory, as well as for the photoproduction of charm mesonD and charm hyperon
c
. 相似文献
4.
Giancarlo D'Ambrosio Mario Miragliuolo Francesco Sannino 《Zeitschrift fur Physik C Particles and Fields》1993,59(3):451-456
We discuss the decayK
s
+– in the framework of chiral perturbation theory. The direct emission in this decay can be an useful test of meson dynamics. 相似文献
5.
J. Brenneisen D. Grathwohl M. Lickert R. Ott H. Röpke J. Schmälzlin P. Siedle B. H. Wildenthal 《Zeitschrift für Physik A Hadrons and Nuclei》1995,352(2):149-159
The systematics of-decay modes and radiative widths of highly excited states in28Si has been extended by taking-ray spectra on 60 resonances of the27Al(p,) reaction in the range 1097 keVE
p
4492 keV (12643 keVE
x
15915 keV) and on the24Mg(,) resonances atE
=3355, 3431, 4003 keV (E
x
=12860, 12925, 13 415 keV). The-decay modes of levels in the sub-resonance region (E
x
=10–12.5 MeV) were studied with both the27
A1(p, ) reaction and the27
A1(d, n) reaction at Ed=4,5,6 MeV. Information on radiative widths of levels was obtained by measuring the resonance strengthsS
=(2I+1)
p
/ for 52 resonances of the27Al(p, ) reaction with an emphasis on prospective T=1 states. 相似文献
6.
S. B. Shlosman 《Communications in Mathematical Physics》1989,125(1):81-90
We consider the 2-dimensional Ising model with ferromagnetic nearest neighbour interaction at inverse temperature. LetS
N
=
t
be the total magnetization inside anN×N square box,
per
be the Gibbs state in with periodic b.c., andm() be the spontaneous magnetization. We show the existence of the limit
相似文献
7.
D. Choudhury P. J. O'Donnell U. Sarkar 《Zeitschrift fur Physik C Particles and Fields》1992,54(2):307-309
The EMC collaboration have reported a measurement of the proton structure function which has been interpreted to mean that the spin of the proton is not predominantly that of the quarks (=u+d+s=0.13±0.19). We show that the magnetic moments of the baryons are independent of this measurement and are given (within 10–20%) for a range of including the valence model value =1. The magnetic moments of the quarks can only be fixed if the quantity is determined very accurately. 相似文献
8.
Narrow dibaryon resonances observed in elastic and inelastic hadron scattering channels atM
NN
*
=1875–2300 MeV/c2 are characterized by the relative resolution (FWHM/M
pp
*
) 10–3 comparable to that provided by Ge(Li) detectors in the case of gamma-ray spectroscopy. The gamma-ray spectrum analysis codes GSAP, AUTSPAN and SAMPO-80 have been used to analyse the effective mass distributions of dibaryons from the reactions dp (pn) p, dp (pp) n, np pp–, and pppp studied at the Dubna synchrophasotron. The produced results suggest these codes to be reliable software tools in the new spectroscopic region of interest.On leave fromNuclear Physics Institute, Czechosl. Acad. Sci., 250 68 e near Prague, Czechoslovakia. 相似文献
9.
D. Alde F. G. Binon M. Boutemeur C. Bricman S. V. Donskov M. Gouanère A. V. Inyakin V. A. Kachanov G. V. Khaustov E. A. Knapp A. V. Kulik G. L. Landsberg A. A. Lednev J. P. Peigneux S. A. Polovnikov M. Poulet Yu. D. Prokoshkin S. A. Sadovsky V. D. Samoylenko P. M. Shagin A. V. Shtannikov A. V. Singovsky J. P. Stroot V. P. Sugonyaev 《Zeitschrift fur Physik C Particles and Fields》1992,54(4):549-551
The production of
0 system in
–
p
charge-exchange interactions at
– momenta 38 GeV/c and 100 GeV/c has been studied. The 2 and
0
0 decay modes of
leading to 4 and 8 final states respectively have been detected. No statistically significant peak is observed in the
0 mass spectrum in the range of 1.2 GeV÷2.1 GeV. An upper limit of 6·10–3 has been established for thea
2
0
(1320)
0 branching ratio. 相似文献
10.
We analyzeK decays in the framework of Chiral Perturbation Theory. We study the different Dalitz plot distributions, trying to find regions whereo(p
6) contributions could be more easily detected. To fulfill this program we compute all theo(p
4) loop and counterterm contributions, finding a substantial agreement with the existing calculations and adding some small missing terms inK
S
+–.Work supported in part by the Human Capital and Mobility Program, EEC Contract N. CHRX-CT920026 相似文献
11.
J. Cleymans V. V. Goloviznin K. Redlich 《Zeitschrift fur Physik C Particles and Fields》1993,57(3):495-500
The most general angular decay distribution of the hadronic system in the decay of a polarized into one pseudoscalar plus a vector is calculated. Emphasis is put on decays ine
+
e
– experiments where the neutrino escapes detection and the restframe cannot be reconstructed. We propose a model for the decay intov
involving both a vector- and a second class axial vector-current contribution. Then we present numerical results for this decay channel. 相似文献
12.
On the basis of the approximate vanishing of the singlet axial charge of the nucleon, it is argued that
1 should decouple from all hadrons constructed out of the constituentu, d ors quarks in theU(3)
L
×U(3)
R
chiral limit for largeN
c
. Furthermore
1 should dominate the processesJ/, . A phenomenological analysis of the and couplings to many hadronic states is consistent with these results. 相似文献
13.
P. Abreu W. Adam T. Adye E. Agasi G. D. Alekseev P. Allen S. Almehed S. J. Alvsvaag U. Amaldi E. G. Anassontzis et al. 《Zeitschrift fur Physik C Particles and Fields》1992,55(4):555-567
From the analysis of a data sample corresponding to an integrated luminosity of 4.63 pb–1 taken during the 1990 run of LEP at centre of mass energies between 88.2 GeV an 94.2 GeV, the tau decays
and their charge conjugates have been studied. The following branching ratios have been measured;
,
, Br(– – (K–)v)=11.9±0.7±0.7%, BR (– – v)= 22.4±0.8±1.3%, in good agreement with world averages. The measured electronic and muonic branching ratios lead to a measurement of the strong coupling constant, s (m) = 0.26
–0.12
+0.09
. Extrapolating the s value fromm
tom
Z
yields s (mZ) = 0.109
–0.028
+0.012
.The average polarizationP
of taus produced in Z s s decays has also been measured using the above decay modes. The weighted mean of the polarizations obtained from the four decay modes isP
=–0.24±0.07. This value ofP
gives, in the improved Born approximation, a ratio between the axial and vector coupling constants of the tau of /a = 0.12 ± 0.04, and hence a value of the effective electroweak mixing parameter sin2 W(m
Z
2
). 相似文献
14.
Isotonic and isobaric dependencies of nuclear charge radii in the region between Z=54 and Z=70 are obtained from the analysis of isotope shift data r2 and muonic and electron scattering data on r2. They are compared with the predictions of the droplet model and the Hartree-Fock calculations. The isobaric dependencies of r2 have proven to be especially sensitive to the choice of an effective nucleon-nucleon interaction. 相似文献
15.
R. L. Altmeyer M. Göckeler R. Horsley E. Laermann G. Schierholz P. M. Zerwas 《Zeitschrift fur Physik C Particles and Fields》1995,68(3):443-449
We calculate the hadronic coupling constantsg
NN
andg
in QCD, including dynamical quarks in the framework of staggered fermions in the lattice approach. For the nucleon-pion coupling we obtaing
NN
=13.8±5.8, to be compared with the experimental value 13.13±0.07 [1]. The coupling has been analysed for two different sets of operators with the averaged resultg
=4.2±1.9 which is to be compared with the experimental value 6.06±0.01 [2]. 相似文献
16.
We consider contributions to
c
+
, and
from excited states. The calculations are performed within the MIT-bag model and a heavy quark bag model. Because the mass of
c
+
is rather big compared to the strange baryons, excited baryon states with mass close to that of
c
+
in some cases give significant pole contributions to the decay amplitudes of
c
+
. 相似文献
17.
G. Kernel D. Korbar P. Križan M. Mikuž F. Sever A. Stanovnik M. Starič D. Zavrtanik E. G. Michaelis N. W. Tanner C. W. E. van Eijk R. W. Hollander W. Lourens S. A. Clark J. D. Davies J. Lowe S. M. Playfer J. V. Jovanovich 《Zeitschrift fur Physik C Particles and Fields》1991,51(3):377-386
We report on results of an experiment to study the reaction –
p – + in the incident pion momentum region between 295 and 450 MeV/c. A departure from phase space was observed in invariant-mass spectra and angular distributions which cannot be explained with and resonance production. It indicates aI=0,J
P
= 0+ – + final-state interaction.Deceased 相似文献
18.
D. Buskulic D. Decamp C. Goy J. -P. Lees M. -N. Minard B. Mours B. Pietrzyk R. Alemany F. Ariztizabal P. Comas et al. 《Zeitschrift fur Physik C Particles and Fields》1993,59(2):215-229
Contact interactions are searched for using the differential cross sections for the reactionse
+
e
–e
+
e
–,e
+
e
–µ
+
µ
–,e
+
e
–
+
– ande
+
e
– measured at 12 energies around theZ peak and corresponding to about 20 pb–1 of cumulated luminosity. Four-fermion contact term models assuming various chiralities of lepton currents are fitted to the lepton data and lower limits on the energy scale of such terms are set at 95% c.l. The limits vary in the range 0.9–4.7 TeV, depending on the model and on the lepton flavour. Theee contact terms are searched for assuming various chiralities. Limits on the energy scale between 79 and 130 GeV are extracted from the data. The results are compared and combined with those reported at lower energies.Deceased 相似文献
19.
D. J. Broadhurst 《Zeitschrift fur Physik C Particles and Fields》1993,58(2):339-345
We calculate analytical contributions to then-loop asymptotic photon propagator from diagrams withn–1 electron loops, i.e. theO(1/N) terms in the largeN limit. The corresponding contributions to the on-shell -function, ()=6 log / logm reduced to rational combinations of
s
=
p
p
–s
. For the -function of the MOM scheme (i.e. the Gell-Man-Low function) we obtain theO(1/N) terms of
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