Existing Monte-Carlo generators with radiative corrections to the
e
+
e
-
→π
+
π
-
process are usually developed under the assumption that pions can be treated as pointlike particles. We study the
e
...+
e
-
→π
+
π
-
γ
process with final-state radiation and test this assumption using simulated events from the MCGPJ generator based on the scalar QED hypothesis. In order to increase a fraction of events with FSR, the analysis was performed in the energy region to the left from the
ρ
-meson peak (660÷785 MeV) that is based on the integrated luminosity of about 8.4 pb
-1
. The experimental data for the photon energy spectrum agree with the simulation results at 1% level.
A large data sample of
e
+
e
-
→ 4π collected by the CMD-3 experiment at the VEPP-2000
e
+
e
−
collider allowed for an amplitude analysis of the process
e
+
e
−
→ 4π in the center-of-mass energy ...range 900–2000 MeV. Various intermediate components were distinguished and dominance of the ωπ
0
and a
1
π amplitudes has been proved.
A study of hadron production at the nucleon-antinucleon threshold has been performed with the CMD-3 detector at the VEPP-2000
e
+
e
−
collider. A very fast rise with an about 1 MeV width has been ...observed in the
e
+
e
−
→
pp
̅ cross section. A sharp drop in the
e
+
e
−
→ 3(π
+
π
−
) cross section has been con?rmed and found to have a width of less than 2 MeV, in agreement with the observed fast rise of the
e
+
e
−
→
pp
̅ cross section. For the ?rst time a similar sharp drop is demonstrated in the
e
+
e
−
→
K
+
K
−
π
+
π
−
cross section. The behavior of the
e
+
e
−
→ 3(π
+
π
−
),
K
+
K
−
π
+
π
−
cross sections cannot be explained by an interference of any resonance amplitude with continuum, therefore this phenomenon cannot be due to a narrow near-threshold resonance. No such structure has been observed in the
e
+
e
−
→ 2(π
+
π
−
) cross section.
Detectors to Study Fast-Floating Processes on the SR Beam Kudashkin, D. V.; Arakcheev, A. S.; Aulchenko, V. M. ...
Surface investigation, x-ray, synchrotron and neutron techniques,
03/2021, Letnik:
15, Številka:
2
Journal Article
Recenzirano
This paper describes systematic measurements of the main parameters of the DIMEX-Si silicon microstrip detector prototype, designed to study fast processes in a beam of synchrotron radiation (SR). ...The dynamic range, spatial resolution and temporal parameters of the detector are estimated. The parameters of the prototype silicon detector are compared with the DIMEX-G gas version. The maximum flux which can be measured by the silicon detector is 40 times higher than that of the gas detector. The spatial resolution of the silicon detector is 130 microns and that of the gas detector is 250 microns. The estimated time resolution of the silicon detector is 15 ns, while for a gas detector this value is about 50 ns. All the characteristics of DIMEX-Si are measured with a cycle time of 25 ns. The results of the first tests of a full-scale silicon detector for diffraction studies, operating in the integrating mode at a speed of up to 2 Mframes/s, are also given. The sensor contains 1024 strips 30 mm long with a step of 50 microns; 512 of these strips are connected to readout electronics based on APC128 ASIC. Each chip contains 128 channels, which consist of a low-noise integrator with 32 analog memory cells. The possibility of signal visualization from single photons and electrons from
109
Cd and
90
Sr sources is shown.
The cross section of the process
e
+
e
−
→ π
+
π
−
π
+
π
−
has been measured using an integrated luminosity of 17 pb
−1
collected with the CMD-3 detector in the center-of-mass energy range 650-1000 ...MeV. High-precision measurements of various hadronic cross sections are of great interest in relation with the problem of the muon anomalous magnetic moment g-2. This measurement can be also used to test the relation between the cross section of
e
+
e
−
→ π
+
π
−
π
+
π
−
and the spectral function for the τ
−
→ π
−
π
0
π
0
π
0
decay predicted by the conservation of vector current (CVC).
A search for the process
e
+
e
−
→
D
*0
(2007) has been performed with the CMD-3 detector at the VEPP-2000
e
+
e
−
-collider. Two main decay modes of the
D
*0
(2007) decay,
D
0
π
0
and
D
0
γ, ...followed by
D
0
→
K
+
π
−
π
+
π
−
are used in this analysis. With an integrated luminosity of 3.7 pb
−1
collected at the center-of-mass energy E
c.m.
=2006.62 MeV our preliminary upper limit is B
D*
0
→
e
+
e
−
<1.6× 10
−6
at 90%C.L.
The development of the new spectrometric channel for the SND electromagnetic calorimeter is described. The time resolution of about 1 ns is achieved at an energy deposition in the calorimeter crystal ...of 100 MeV . The amplitude resolution is about 250 keV.
The VEPP-2000 e+e− collider has been operated in the Budker Institute of Nuclear Physics since 2010. Experiments are carried out with two detectors CMD-3 and SND. The calorimetry at the CMD-3 ...detector is based on three subsystems, two coaxial barrel calorimeters—Liquid Xenon calorimeter and crystal CsI calorimeter, and end cap calorimeter with BGO crystals. This paper describes the procedures of the energy calibration of the combined barrel calorimeter of the CMD-3 detector.
We report the final results of a study of the ψ(3770) meson using a data sample collected with the KEDR detector at the VEPP-4M electron–positron collider. The data analysis takes into account ...interference between the resonant and nonresonant DD¯ production, where the latter is related to the nonresonant part of the energy-dependent form factor FD. The vector dominance approach and several empirical parameterizations have been tried for the nonresonant FDNR(s).
Our results for the mass and total width of ψ(3770) areM=3779.2−1.7+1.8−0.7+0.5−0.3+0.3 MeV,Γ=24.9−4.0+4.6−0.6+0.5−0.9+0.2 MeV, where the first, second and third uncertainties are statistical, systematic and model, respectively. For the electron partial width two possible solutions have been found:(1)Γee=154−58+79−9+17−25+13 eV,(2)Γee=414−80+72−26+24−10+90 eV. Our statistics are insufficient to prefer one solution to another. The Solution (2) mitigates the problem of non-DD¯ decays but is disfavored by potential models.
It is shown that taking into account the resonance–continuum interference in the near-threshold region affects resonance parameters, thus the results presented cannot be directly compared with the corresponding PDG values obtained ignoring this effect.
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