共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
S. E. Baru M. V. Beilin A. E. Blinov V. E. Blinov A. E. Bondar A. D. Bukin S. I. Eidelman Yu. I. Eidelman V. R. Groshev V. A. Kiselev S. G. Klimenko G. M. Kolachev S. I. Mishnev A. P. Onuchin V. S. Panin V. V. Petrov I. Ya. Protopopov A. G. Shamov V. A. Sidorov Yu. I. Skovpen A. N. Skrinsky V. A. Tayursky V. I. Telnov A. B. Temnykh Yu. A. Tikhonov G. M. Tumaikin A. E. Undrus A. I. Vorobiov V. N. Zhilich A. A. Zholents 《Zeitschrift fur Physik C Particles and Fields》1992,53(2):219-224
The total cross section for hadrons was measured as a function of the invariant massW of the system (1.25 to 4.25 GeV) at thee
+
e
–-collider VEPP-4 with the detector MD-1. For the first time the data were obtained by detecting both scattered leptons with almost zero emission angles. The mean squared four momentum transfer q
2 is –0.005 GeV2, the rmsW resolution is 100–250 MeV. The data on the mean charged multiplicity n
C
are well described by the function n
C
=(1.62 ±0.37)+(1.83±0.45)·ln(W(GeV)). TheW dependence of the total cross section is consistent with the theoretical prediction (nb)=240+270/W(GeV). 相似文献
3.
Nikolai N. Nikolaev Vladimir R. Zoller 《Zeitschrift fur Physik C Particles and Fields》1992,56(4):623-628
One expects a similarity of the energy dependence of the difference
tot(*p)–
tot(*n) for virtual (deep inelastic scatteringQ
2m
2) and real (Q
2=0) photons. Previous analysis of D structure functions with allowence for nuclear shadowing (NS) in the deuteron has led to conclusion that
tot(*p)–
tot(*n)<0>0>x<0.015. the=" early=" evidence=" from=" the=" real=" photoproduction=" data=">0.015.>
tot(p)–
tot(n)<0. we=" critically=" reexamine=" determinations=" of=" the=">0.>
tot(p)–
tot(n), using more accurate calculations of NS correction to
tot(D), and discuss a possibility of
tot(n)
tot(p) at moderately high energies. 相似文献
4.
New measurements of the reactione
+
e
– confirm previous evidence for the decay1 and provide a strong constraint on the mass of the1. The results from a detailed analysis of these data are compared with those from a corresponding analysis of new data on the reactione
+
e
–. It is shown that
in accord with expectation. This identification of a strong1 decay supports a previous claim that the1 and theC(1480), observed in the channel, cannot be different manifestations of the same particle. 相似文献
5.
G. M. Beladidze S. I. Bityukov G. V. Borisov Yu. P. Gouz R. I. Dzhelyadin Yu. M. Ivanyushenkov A. N. Karyukhin I. A. Kachaev G. A. Klyuchnikov V. F. Konstantinov M. E. Kostrikov V. V. Kostyukhin A. A. Kriushin Yu. A. Khoklov V. V. Lapin T. A. Lomtadze V. D. Matveyev V. A. Medovikov V. F. Obraztsov A. P. Ostankov D. I. Ryabchikov V. K. Semenov E. A. Starchenko N. A. Shalanda E. G. Tskhadadze N. K. Vishnevsky E. V. Vlasov V. I. Yakimschuk A. M. Zaitsev S. A. Zimin 《Zeitschrift fur Physik C Particles and Fields》1992,54(2):235-238
The reaction
–
C
–
C has been studied at 36 GeV/c. A clear signal for the decaya
2
–
(1320)
–
· is observed in the
–
mass spectrum. The measured ratio of branchings is BR (a
2
–
–
)/BR(a
2
–
–
);(3.4±0.8±0.5)·10–2. 相似文献
6.
F. zu Bentheim P. David J. Debrus F. Hinterberger R. Jahn F. Lübke H. Mommsen R. Schoenmackers B. Schüller 《Zeitschrift für Physik A Hadrons and Nuclei》1976,40(3):163-168
Experimental data of the elastic scattering of-particles on10B forE
= 30–50.6 MeV are presented. They are analysed together with the data of a previous measurement forE
= 5–30 MeV in the frame of the optical model including spin-orbit coupling. The interaction radii of the-10B-systems are determined with the Inopin-Ericson model forE
= 5–50 MeV. The mean free path of-particles in10B is calculated. 相似文献
7.
K. O. Zell H. -G. Friederichs B. Heits D. Hippe H. W. Schuh P. von Brentano C. Protop 《Zeitschrift für Physik A Hadrons and Nuclei》1976,3(3):371-380
77Se has been investigated by the reaction74Ge(,n) at 14 MeV. Gamma singles spectra, gamma angular distributions and gamma-gamma coincidences have been taken. A level scheme has been established, spins and parities have been assigned. States of a rotational band on the 1/2– ground state, a rotational band on the 5/2– 249.7 keV state and an anormal band have been identified.
Nuclear Reaction
74Ge(,n )E
=14 MeV; measuredE
,I
,--Coin.,-ang. distr.77Se deduced levels,J, . Enriched target, Ge (Li). 相似文献
8.
H. Albrecht T. Hamacher R. P. Hofmann T. Kirchhoff R. Mankel A. Nau S. Nowak H. Schr?der H. D. Schulz M. Walter et al. 《Zeitschrift fur Physik C Particles and Fields》1995,68(2):215-220
Using the ARGUS detector at the storage ring DORIS II we have measured decays into three charged mesons containingK
* mesons. Exploiting the good particle identification capabilities of the detector we have determined the following branching ratios:
,B
r
(–K
*0
K
–
v
)= (0.20±0.05±0.04)%, andB
r
(–K
*–
X
0
v
) =(1.15±0.15–0.18
+0.13)%.Supported by the German Bundesministerium für Forschung und Technologie, under contract number 054DO51P. 相似文献
9.
M. Ciuchini E. Franco G. Martinelli L. Reina L. Silvestrini 《Zeitschrift fur Physik C Particles and Fields》1995,68(2):239-255
An upgraded analysis of ,x
d
and /, using the latest determinations of the relevant experimental and theoretical parameters, is presented. Using the recent determination of the top quark mass,m
t
=(174±17) GeV, our best estimate is /=(3.1±2.5)×10–, which lies in the range given by E731. We describe our detemination of / and make a comparison with other similar studies. A detailed discussion of the matching of the full theory to the effective Hamiltonian, written in terms of lattice operators, is also given. 相似文献
10.
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
11.
J. Rico B. Rubio J. L. Tain A. Gadea J. Bea L. M. Garcia-Raffi O. Tengblad P. Kleinheinz R. Menegazzo R. Wirowski P. von Brentano G. Siems J. Blomqvist 《Zeitschrift für Physik A Hadrons and Nuclei》1993,345(2):245-246
In a high sensitivity (,2n) in-beam study of
62
144
Sm82, with the Kölner Würfel OSIRIS -detector array including a Compton polarimeter, we have identified the complete two-proton multiplets d
5
2/–2
, d
5
2/–1
g
7
2/–1
, g
7
2/–2
, h11/2d
5
2/–1
and the 9– to 4– members of the h11·/2g
7
2/–1
multiplet.Work partially supported by CICYT (Spain). 相似文献
12.
13.
A new procedure is devised to evaluate the proton form-factor at the ¯pp threshold from experimental data on ¯ppe
+
e
– annihilation at rest. Comparison of the ¯ppe
+
e
– and¯pp
+– processes reveals that annihilation ranges for various channels are ranked in line with quark dynamics.This work has been funded in part by the German Federal Minister for Research and Technology (BMFT) under the contract number 06HD756 相似文献
14.
V. F. Perepelitsa N. Z. Akopov L. Dorsaz A. Ferrer A. A. Grigoryan V. V. Karapetyan V. I. Mikhailichenko S. Ya. Nikitin P. Sonderegger A. S. Zhokin 《Zeitschrift fur Physik C Particles and Fields》1991,50(3):395-404
We have analyzed backward meson production in
+
p reactions at 20GeV/c, which were measured in the CERN spectrometer triggered by a fast proton (p
f
), in experiment WA56. Production via baryon exchange of quasi-two-body final states
++ (1232)
0 (770),
++ (1232)f
2 (1270), and
++ (1232)
3
0
(1690) is clearly identified. The density matrix elements of meson resonances and of
++ (1232) are analyzed. We have observed also the reactions
+
p
++ (1232)
0 and
+
p
++ (1232) in thep
f
+
0 andp
f
+
+
–
0 final states. 相似文献
15.
The exact sphaleron solution in the bosonic sector of the electro-weak standard model is only known for weak mixing angle
w
=0. To investigate the behaviour closer to the experimental value
W
exp
30° we construct a non-contractible loop in configuration space that is sensitive to
W
. Our numerical results for the energy and the magnetic dipole moment, combined with previous perturbative results, indicate that the dependence on
W
is weak. 相似文献
16.
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
17.
I. G. Aznauryan 《Zeitschrift fur Physik C Particles and Fields》1995,68(3):459-462
We show that photoproduction experiments provide propitious conditions to study the exotic state 1–+ in the and channels. For unpolarized photons contributions from natural and unnatural parity exchanges do not interfere with each other, a fact which permits to estimate the correctness of phase shift analyses. In photoproduction of the + system in the mass range ofa
2(1320) a more stringent limit on the product (1–+)Br(1–+) can be obtained than in experiments on Primakoff production on nuclei. Particularly favourable is the study of the state 1–+ in the coherent photoproduction of the 0 and 0 systems on nuclei, with significantly enlarged statistics and a simplified phase shift analysis. 相似文献
18.
19.
T. A. Armstrong R. P. Barnes M. Benayoun W. Beusch I. J. Bloodworth J. N. Carney D. DiBari C. J. Dodenhoff C. Evangelista D. Evans B. Ghidini B. R. French M. Girone A. Jacholkowski J. B. Kinson A. Kirk K. Knudson V. Lenti V. Manzari F. Navach A. Palano E. Quercigh M. Sené R. Sené G. Vassiliadis O. Villalobos Baillie M. F. Votruba 《Zeitschrift fur Physik C Particles and Fields》1992,54(3):371-376
The reactionppp
f
(
+
–
)p
s
, where the
+
–
system is centrally produced, has been studied at 300 GeV/c. The
+
–
mass spectrum shows evidence for a
0
decay mode of the (958) andf
1 (1285). The branching ratio (f
1(1285)
+
+)/(f
1(1285)
0
) is found to be 5.0±0.7. No evidence is found for a
0(770) decay mode of theE/f
1 (1420) for which an upper limit BR (E/f
1(1420)
0
)<0.08 at=" 95%=" cl=" is=">0.08> 相似文献
20.
J. Döring L. Funke W. Wagner G. Winter 《Zeitschrift für Physik A Hadrons and Nuclei》1991,339(3):425-426
Excited states in the doubly-odd nucleus82Rb have been investigated via the reactions79Br(,n) and78Se(7Li,3n) using in-beam-ray spectroscopy. The level energy of the longlived 5– isomer has been determined to 68.3 keV which is below the energy of the 2– state found at 88.9 keV with a lifetime of=2.4(2) ns. A sequence of positive-parity states beginning with a 6+ level at 191.3 keV (=20(3) ns) and extending to a (10+) level has been interpreted to contain the two-particle configuration (g
9/2
9/2) and collective excitations. 相似文献