57 research outputs found
New Data from SND Detector in Novosibirsk
The current status of experiments with SND detector at VEPP-2M e^+e^-
collider in the energy range 2E_0=400-1400 MeV and recent results of data
analysis for , and decays and e^+e^- annihilation into
hadrons are presented.Comment: 7 pages, 8 figures, Latex2e, uses espcrc1.sty. Talk given at 8th
International Conference on Hadron Spectroscopy (HADRON 99), Beijing, China,
24-28 Aug 199
Study of the process in the energy region below 0.98 GeV
The cross section of the process was measured in
the Spherical Neutral Detector (SND) experiment at the VEPP-2M collider in the
energy region below 980 MeV. This measurement was based on about
selected events. The obtained cross section was analyzed
together with the SND and DM2 data in the energy region up to 2
GeV. The -meson parameters: MeV,
MeV and nb were obtained. It was found that the experimental data cannot be
described by a sum of only , , and
resonances contributions. This can be interpreted as a
manifestation of decay, suppressed by -parity, with relative
probability .Comment: 41 pages REVTEX and 34 figure
Experimental study of the e+e- -> pi0 gamma process in the energy region sqrt(s)=0.60-0.97 GeV
Results of the study of the e+e-->pi0 gamma process with SND detector at
VEPP-2M collider in the c.m.s. energy range sqrt(s)=0.60-0.97 GeV are
presented. Using 36513 selected events corresponding to a total integrated
luminosity of 3.4 pb^-1 the e+e-->pi0 gamma cross section was measured. The
energy dependence of the cross section was analyzed in the framework of the
vector meson dominance model. The data are well described by a sum of
phi,omega,rho0->pi0 gamma decay contributions with measured decay
probabilities: Br(omega->pi0 gamma)=(9.34+-0.15+-0.31)% and Br(rho0->pi0
gamma)=(5.15+-1.16+-0.73)*10^-4 . The rho-omega relative interference phase is
phi(rho,omega}=(-10.2+-6.5+-2.5) degree
Experimental Study of rho -> pi0 pi0 gamma and omega -> pi0 pi0 gamma Decays
The e+e- -> pi0 pi0 gamma process was studied in the SND experiment at
VEPP-2M e+e- collider in the energy region 0.60-0.97 GeV. From the analysis of
the energy dependence of measured cross section the branching ratios B(omega ->
pi0 pi0 gamma)= (6.6 +1.4-0.8(stat) +-0.6(syst))x10^-5 and B(rho -> pi0 pi0
gamma)=(4.1 +1.0-0.9(stat) +-0.3(syst))x10^-5 were obtained.Comment: 16 pages, 7 figures, submitted to Phys. Lett.
Search for direct production of a2(1320) and f2(1270) mesons in e+e- annihilation
A search for direct production of C-even resonances a2(1320) and f2(1270) in
e+e- annihilation was performed with SND detector at VEPP-2M e+e- collider. The
upper limits of electronic widths of these mesons were obtained at 90%
confidence level:
Gamma(a2(1320) \to e+e-) < 0.56 eV,
Gamma(f2(1270) \to e+e-) < 0.11 eV.Comment: 6 pages, 5 figures, 1 table. Submitted to Phys. Lett.
The process in the energy range 2E_0=1.04 - 1.38 GeV
In the experiment with the SND detector at VEPP-2M e^+e^- collider the
process was studied in the energy range 2E_0 from
1.04 to 1.38 GeV. A broad peak was observed with the visible mass
MeV and cross section in the maximum
nb. The peak can be interpreted as a -like resonance .Comment: 10 pages LATEX and 5 figure
Pion Form Factor at SND (new edition)
The update of the e^+e^-\to\pi^+\pi^- process cross section, measured in the
energy region \sqrt{s}<1 GeV with SND detector at VEPP-2M collider is
presented.Comment: Talk given at Int. Workshop e+e- Collisions from phi to psi, February
27 - March 2, 200
First Observation of PHI(1020)--->PI0+PI0+GAMMA Decay
In the SND experiment at the VEPP-2M electron-positron collider the
PHI(1020)--->PI0+PI0+GAMMA decay was studied. The branching ratio
B(PHI--->PI0+PI0+GAMMA)=(1.14+-0.10+-0.12)x10^{-4} was measured. It was shown,
that the F0(980)GAMMA mechanism dominates in this decay and the 4-quark model
of F0(980) describes our data most consistently.Comment: 6 pages, 6 figures, 1 table, Will be published in Phys.Lett.
Study of the decays into and final states
Radiative decays of the meson have been studied using a data sample of
about 19 million decays collected by the CMD-2 detector at VEPP-2M
collider in Novosibirsk. From selected and
events the following model independent results
have been obtained: \par for MeV, \par
.
It is shown that the intermediate mechanism dominates in
the decay and the corresponding branching ratio
is \par . The
systematic error is dominated by the possible model uncertainty. \par Using the
same data sample the upper limit has been obtained for the P- and CP-violating
decay of at 90% CL: \par
>.Comment: 13 pages, 6 figures, Submitted to Phys. Lett.
and Polarizabilities from {} Data on the Base of S-Matrix Approach
We suggest the most model-independent and simple description of the
process near threshold in framework of S-matrix
approach. The amplitudes contain the pion polarizabilities and rather
restricted information about interaction. Application of these
formulae for description of MARK-II \cite{M2} and Crystal Ball \cite{CB} data
gives: ,
(in units system ) at the experimental values of scattering lengths. Both
values are compartible with current algebra predictions.Comment: LaTeX, 14 pages plus 6 figures (not included, available upon request)
, ISU-IAP.Th93-03, Irkuts
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