Recently, a
γ
γ
collider based on the existing 17.5 GeV linac of the European XFEL has been proposed. High-energy photons will be generated by Compton scattering of laser photons with a wavelength of ...0.5–1
μ
m
on electrons. Such a photon collider covers the range of invariant masses
W
γ
γ
<
12
Ge
V
/
c
2
. The physics program includes spectroscopy of
C
-even resonances (
c
-,
b
-quarkonia, 4-quark states, glueballs) in various
J
P
states. Variable circular and linear polarizations will help in determining the quantum numbers. In this paper, we present a summary of measured and predicted two-photon widths of various resonances in the mass region 3–12
Ge
V
/
c
2
and investigate the experimental possibility of observing these heavy two-photon resonances under the conditions of a large multi-hadron background. Registration of all final particles is assumed. The minimum values of
Γ
γ
γ
(
W
)
are obtained at which resonances can be detected at a
5
σ
confidence level in 1 year of operation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
Recently, a
$$\gamma \gamma $$
γ
γ
collider based on the existing 17.5 GeV linac of the European XFEL has been proposed. High-energy photons will be generated by Compton scattering of laser ...photons with a wavelength of 0.5–1
$${\,\upmu \mathrm m}$$
μ
m
on electrons. Such a photon collider covers the range of invariant masses
$$W_{\gamma \gamma } <12$$
W
γ
γ
<
12
$${\mathrm {\,Ge V\!/}c^2}$$
Ge
V
/
c
2
. The physics program includes spectroscopy of
$$ C $$
C
-even resonances (
c
-,
b
-quarkonia, 4-quark states, glueballs) in various
$$J^P$$
J
P
states. Variable circular and linear polarizations will help in determining the quantum numbers. In this paper, we present a summary of measured and predicted two-photon widths of various resonances in the mass region 3–12
$${\mathrm {\,Ge V\!/}c^2}$$
Ge
V
/
c
2
and investigate the experimental possibility of observing these heavy two-photon resonances under the conditions of a large multi-hadron background. Registration of all final particles is assumed. The minimum values of
$$\varGamma _{\gamma \gamma }(W)$$
Γ
γ
γ
(
W
)
are obtained at which resonances can be detected at a
$$5\sigma $$
5
σ
confidence level in 1 year of operation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The recent precise measurements of the
e
+
e
–
→
K
S
K
L
and
e
+
e
–
→
K
+
K
–
cross sections and the hadronic spectral function of the τ
–
→
K
–
K
S
ν
τ
decay are used to extract the isoscalar and ...isovector electromagnetic kaon form factors and their relative phase in a model-independent way. The experimental results are compared with a fit based on the vector-meson-dominance model.
The recent precise measurements of the e+e− → K+K− and e+e− → KSKL cross sections and the hadronic spectral function of the τ− → K−KSντ decay are used to extract the isoscalar and isovector ...electromagnetic kaon form factors and their relative phase in a model independent way. The experimental results are compared with a fit based on the vector-meson-dominance model.
The process
e
+
e
-
→
n
n
¯
is studied in the experiment at the VEPP-2000
e
+
e
-
collider with the SND detector. The technique of the time measurements in the multichannel NaI(Tl) electromagnetic ...calorimeter is used to select
n
n
¯
events. The value of the measured cross section in the center-of-mass energy range from 1.894 to 2 GeV varies from 0.5 to 0.35 nb. The effective neutron timelike form factor is derived from the measured cross section and compared with the proton form factor. The ratio of the neutron electric and magnetic form factors is obtained from the analysis of the antineutron polar angle distribution and found to be consistent with unity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The process
was studied in the energy range between 1 and 2 GeV to the best precision in the world. The data used correspond to an integrated luminosity of
accumulated with the SND detector at the ...VEPP-2000
collider. The statistical accuracy of the measured cross section is 2 to 22
, whereas the systematic uncertainty is 2.6 to 14
. The present results agree with the results of earlier measurements but have a better precision.
The process
is studied in the range of center-of-mass (c.m.) collision energies between 1.05 and 2.00 GeV on the basis of data corresponding to an integrated luminosity of 94.5 pb
that were ...accumulated in an experiment with the SND detector at the VEPP-2000
collider. The cross section for this process was measured for the first time and was found to receive a dominant contribution from the mechanism of a transition through an
intermediate state. The cross section measured for the process
agrees with the results of earlier measurements in the channel
. At a level of 5.7 standard deviations (5.7
), it is established that the process
is not fully described by hadronic intermediate states of the
type. The cross section was measured for this missing contribution, which may be generated by radiative processes—for example,
. It ranges from 15 to 20 pb over a broad energy interval extending from 1.3 to 1.9 GeV.
In an experiment with the SND detector at the VEPP-2000
collider, the cross sections for the processes
and
were measured at collision energies of
GeV in the center-of-mass frame. The results agree ...with the results of earlier measurements in the BABAR experiment and have a commensurate precision.
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