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127
result(s) for
"Gauzzi, P."
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Measurement of the KS→ πeν branching fraction with the KLOE experiment
A
bstract
The ratio
R
= Γ(
K
S
→ πeν
)
/
Γ(
K
S
→ π
+
π
−
) has been measured with a sample of 300 million
K
S
mesons produced in
ϕ → K
L
K
S
decays recorded by the KLOE experiment at the DAΦNE
e
+
e
−
collider.
K
S
→ πeν
events are selected by a boosted decision tree built with kinematic variables and time-of-flight measurements. Data control samples of
K
L
→ πeν
decays are used to evaluate signal selection efficiencies. With 49647
±
316 signal events we measure
R
= (1
.
0421
±
0
.
0066
stat
±
0
.
0075
syst
)
×
10
−
3
. The combination with our previous measurement gives
R
= (1
.
0338
±
0
.
0054
stat
±
0
.
0064
syst
)
×
10
−
3
. From this value we derive the branching fraction
B
(
K
S
→ πeν
) = (7
.
153
±
0
.
037
stat
±
0
.
044
syst
)
×
10
−
4
and
f
+
(0)
|V
us
|
= 0
.
2170
±
0
.
009.
Journal Article
Measurement of η → π0γγ branching fraction with the KLOE detector
A
bstract
We present a measurement of the doubly radiative decay
η
→
π
0
γγ
based on a sample of 82 million
η
mesons produced in the
e
+
e
−
→
ϕ
→
ηγ
process at the Frascati
ϕ
-factory DAΦNE. From the data analysis, 1246 ± 133 signal events were observed. By normalising the signal to the well-known
η
→ 3
π
0
decay the branching fraction
is measured to be (0
.
98 ± 0
.
11
stat
± 0
.
14
syst
) × 10
−
4
. This result agrees with a preliminary KLOE measurement, but is a factor of two smaller than the current world average. Results for
d
Γ(
η
→
π
0
γγ
)
/dM
2
(
γγ
) are also presented and compared with the latest theoretical predictions.
Journal Article
Measurement of η → π 0 γγ branching fraction with the KLOE detector
We present a measurement of the doubly radiative decay η → π0γγ based ona sample of 82 million η mesons produced in the e+e− → ϕ → ηγ process at the Frascatiϕ-factory DAΦNE. From the data analysis, 1246 ± 133 signal events were observed. Bynormalising the signal to the well-known η → 3π0 decay the branching fraction B(η → π0γγ) ismeasured to be (0.98 ± 0.11stat ± 0.14syst) × 10−4. This result agrees with a preliminary KLOEmeasurement, but is a factor of two smaller than the current world average. Results for dΓ(η →π0γγ)/dM 2(γγ) are also presented and compared with the latest theoretical predictions.
Journal Article
Precision tests of quantum mechanics and CPT symmetry with entangled neutral kaons at KLOE
A
bstract
The quantum interference between the decays of entangled neutral kaons is studied in the process
ϕ
→ K
S
K
L
→
π
+
π
−
π
+
π
−
, which exhibits the characteristic Einstein-Podolsky-Rosen correlations that prevent both kaons to decay into
π
+
π
−
at the same time. This constitutes a very powerful tool for testing at the utmost precision the quantum coherence of the entangled kaon pair state, and to search for tiny decoherence and
CPT
violation effects, which may be justified in a quantum gravity framework.
The analysed data sample was collected with the KLOE detector at DAΦNE, the Frascati
ϕ
-factory, and corresponds to an integrated luminosity of about 1.7 fb
−
1
, i.e. to about 1
.
7 × 10
9
ϕ
→ K
S
K
L
decays produced. From the fit of the observed ∆
t
distribution, being ∆
t
the difference of the kaon decay times, the decoherence and
CPT
violation parameters of various phenomenological models are measured with a largely improved accuracy with respect to previous analyses.
The results are consistent with no deviation from quantum mechanics and
CPT
symmetry, while for some parameters the precision reaches the interesting level at which — in the most optimistic scenarios — quantum gravity effects might show up. They provide the most stringent limits up to date on the considered models.
Journal Article
Measurement of the charge asymmetry for the KS → πeν decay and test of CPT symmetry with the KLOE detector
A
bstract
Using 1.63 fb
−1
of integrated luminosity collected by the KLOE experiment about 7 × 10
4
K
S
→
π
±
e
∓
ν
decays have been reconstructed. The measured value of the charge asymmetry for this decay is
A
S
= (−4.9 ± 5.7
stat
± 2.6
syst
) × 10
−3
, which is almost twice more precise than the previous KLOE result. The combination of these two measurements gives
A
S
= (−3.8 ± 5.0
stat
± 2.6
syst
) × 10
−3
and, together with the asymmetry of the
K
L
semileptonic decay, provides significant tests of the
CPT
symmetry. The obtained results are in agreement with
CPT
invariance.
Journal Article
Upper limit on the η → π+π− branching fraction with the KLOE experiment
A
bstract
Based on an integrated luminosity of 1.61 fb
−
1
e
+
e
−
collision data collected with the KLOE detector at DAΦNE, the Frascati
ϕ
-factory, a search for the
P
- and
CP
-violating decay
η → π
+
π
−
has been performed. Radiative
ϕ → ηγ
decay is exploited to access the
η
mesons. No signal is observed in the
π
+
π
−
invariant mass spectrum, and the upper limit on the branching fraction at 90% confidence level is determined to be ℬ(
η → π
+
π
−
)
<
4
.
9
×
10
−
6
, which is approximately three times smaller than the previous KLOE result. From the combination of these two measurements we get ℬ(
η → π
+
π
−
)
<
4
.
4
×
10
−
6
at 90% confidence level.
Journal Article
Precise measurement of Γ(K→e ν(γ))/Γ(K→μ ν(γ)) and study of K→e ν γ
We present a precise measurement of the ratio RK=Γ(K→eν(γ))/Γ(K→μν(γ)) and a study of the radiative process K→eνγ, performed with the KLOE detector. The results are based on data collected at the Frascati e+e− collider DAΦNE for an integrated luminosity of 2.2 fb−1. We find RK=(2.493±0.025stat±0.019syst)×10−5, in agreement with the Standard Model expectation. This result is used to improve constraints on parameters of the Minimal Supersymmetric Standard Model with lepton flavor violation. We also measured the differential decay rate dΓ(K→eνγ)/dEγ for photon energies 10
Journal Article
Measurement of eta meson production in gamma gamma interactions and Gamma ( eta arrow right gamma gamma ) with the KLOE detector
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).We present a measurement of eta meson production in photon-photon interactions produced by electron-positron beams colliding with ... GeV. The measurement is done with the KLOE detector at the -factory DA Phi NE with an integrated luminosity of 0.24 fb super(-1). The e super(+) e super(-) arrow right e super(+) e super(-) eta cross section is measured without detecting the out-going electron and positron, selecting the decays eta arrow right pi super(+) pi super(-) pi super(0) and eta arrow right pi super(0) pi super(0) pi super(0). The most relevant background is due to e super(+) e super(-) arrow right eta gamma when the monochromatic photon escapes detection. The cross section for this process is measured as sigma (e super(+) e super(-) arrow right eta gamma ) = (856 plus or minus 8 sub(stat) plus or minus 16 sub(syst)) pb. The combined result for the e super(+) e super(-) arrow right e super(+) e super(-) eta cross section is sigma (e super(+) e super(-) arrow right e super(+) e super(-) eta ) = (32.72 plus or minus 1.27 sub(stat) plus or minus 0.70 sub(syst)) pb. From this we derive the partial width Gamma ( eta arrow right gamma gamma ) = (520 plus or minus 20 sub(stat) plus or minus 13 sub(syst)) eV. This is in agreement with the world average and is the most precise measurement to date.
Journal Article
Precision measurement of the K S meson lifetime with the KLOE detector
Using a large sample of pure, slow, short lived K0 mesons collected with KLOE detector at DAΦNE, we have measured the KS lifetime. From a fit to the proper time distribution we find τ(KS)=(89.562±0.029stat±0.043syst) ps. This is the most precise measurement to date of the short lived K0 meson lifetime, in good agreement with the world average derived from previous measurements. We observe no dependence of the lifetime on the direction of the KS in galactic coordinates.
Journal Article