Tests of the T, CP and CPT symmetries in the neutral kaon system are performed by the direct comparison of the probabilities of a kaon transition process to its symmetry-conjugate. The exchange of in ...and out states required for a genuine test involving an antiunitary transformation implied by time-reversal is implemented exploiting the entanglement of K0K‾0 pairs produced at a ϕ-factory.
A data sample collected by the KLOE experiment at DAΦNE corresponding to an integrated luminosity of about 1.7 fb−1 is analysed to study the Δt distributions of the ϕ→KSKL→π+π−π±e∓ν and ϕ→KSKL→π±e∓ν3π0 processes, with Δt the difference of the kaon decay times. A comparison of the measured Δt distributions in the asymptotic region Δt≫τS allows to test for the first time T and CPT symmetries in kaon transitions with a precision of few percent, and to observe CP violation with this novel method.
Based on a sample of 300 million KS mesons produced in ϕ→KLKS decays recorded by the KLOE experiment at the DAΦNE e+e− collider we have measured the branching fraction for the decay KS→πμν. The KS ...mesons are identified by the interaction of KL mesons in the detector. The KS→πμν decays are selected by a boosted decision tree built with kinematic variables and by a time-of-flight measurement. Signal efficiencies are evaluated with data control samples of KL→πμν decays. A fit to the reconstructed muon mass distribution finds 7223±180 signal events. Normalising to the KS→π+π− decay events the result for the branching fraction is B(KS→πμν)=(4.56±0.11stat±0.17syst)×10−4. It is the first measurement of this decay mode and the result allows an independent determination of |Vus| and a test of the lepton-flavour universality.
The Mu2e experiment at Fermilab searches for the charged-lepton flavor violating (CLFV) conversion of a negative muon into an electron in the field of an aluminum nucleus, with a distinctive ...signature of a monoenergetic electron of energy slightly below the muon rest mass (104.967 MeV). The Mu2e goal is to improve by four orders of magnitude the search sensitivity with respect to the previous experiments. Any observation of a CLFV signal will be a clear indication of new physics. The Mu2e detector is composed of a tracker, an electromagnetic calorimeter, and an external veto for cosmic rays surrounding the solenoid. The calorimeter plays an important role in providing particle identification capabilities, a fast online trigger filter, a seed for track reconstruction while working in vacuum, in the presence of 1-T axial magnetic field and in a harsh radiation environment. The calorimeter requirements are to provide a large acceptance for 100-MeV electrons and reach at these energies: 1) a time resolution better than 0.5 ns; 2) an energy resolution <10%; and 3) a position resolution of 1 cm. The calorimeter design consists of two disks, each one made of 674-undoped cesium iodine crystals read by two large area arrays of UV-extended silicon photomultipliers (SiPMs). We report here the construction and the test of the Module-0 prototype. The Module-0 has been exposed to an electron beam in the energy range around 100 MeV at the Beam Test Facility in Frascati. Preliminary results of timing and energy resolution at normal incidence are shown. A discussion of the technical aspects of the calorimeter engineering is also reported in this paper.
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.
The Mu2e experiment is constructing a calorimeter consisting of 1348 undoped cesium iodide (CsI) crystals in two disks. Each crystal has a dimension of 34 × 34 × 200 mm3 and is readout by a ...large-area silicon photomultipliers array. A series of technical specifications on mechanical and optical parameters was defined according to the calorimeter physics requirements. Preproduction CsI crystals were procured from three firms: Amcrys, Saint-Gobain, and Shanghai Institute of Ceramics. We report the quality assurance on crystal's scintillation properties and their radiation hardness against ionization dose and neutrons. With a fast decay time of about 30 ns and a light output of more than 100 p.e./MeV measured by a bialkali photomultiplier tube, undoped CsI crystals provide a cost-effective solution for Mu2e.
The Mu2e experiment at Fermilab will search for the charged lepton flavor violating neutrino-less conversion of a negative muon into an electron in the field of an aluminum nucleus <xref ...ref-type="bibr" rid="ref1">1 , <xref ref-type="bibr" rid="ref2">2 . The Mu2e detector is comprised of a tracker, an electromagnetic calorimeter, and an external veto for cosmic rays. The calorimeter plays an important role in providing excellent particle identification capabilities, a fast and online trigger filter while aiding the track reconstruction capabilities. The calorimeter requirements are to provide a large acceptance for 100-MeV electrons and reach: 1) a time resolution better than 0.5 ns at 100 MeV; 2) an energy resolution O(10%) at 100 MeV; and 3) a position resolution of about 1 cm. The calorimeter consists of two disks, each one made of 674 pure CsI crystals readout by two large-area <inline-formula> <tex-math notation="LaTeX">2 \times 3 </tex-math></inline-formula> array of UV-extended silicon photomultipliers (Mu2e SiPMs) of <inline-formula> <tex-math notation="LaTeX">6\,\,\times6 </tex-math></inline-formula> mm 2 dimensions. A large-scale prototype has been constructed with 51 preproduction crystals readout by 102 Mu2e SiPMs. It has been tested at the beam test facility in Frascati, demonstrating satisfying results compared to the Mu2e requirements. At the moment of writing, the crystals production phase is halfway through the work, while the SiPM production has been completed. An overview of the characterization tests is also reported, together with a description of the final calorimeter design.
In this paper we present the time resolution measurements of the Lutetium–Yttrium Oxyorthosilicate (LYSO) calorimeter prototype for the Mu2e experiment. The measurements have been performed using the ...e− beam of the Beam Test Facility (BTF) in Frascati, Italy in the energy range from 100 to 400MeV. The calorimeter prototype consisted of twenty five 30×30×130mm3, LYSO crystals read out by 10×10mm2 Hamamatsu Avalanche Photodiodes (APDs). The energy dependence of the measured time resolution can be parametrized as σt(E)=a/E/GeV⊕b, with the stochastic and constant terms a=(51±1)ps and b=(10±4)ps, respectively. This corresponds to the time resolution of (162±4)ps at 100MeV.
QCALT: A tile calorimeter for KLOE-2 experiment Cordelli, M.; Corradi, G.; Happacher, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2010, Letnik:
617, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The upgrade of the
DA
Φ
NE
machine layout requires a modification of the size and position of the inner focusing quadrupoles of KLOE-2 thus asking for the realization of two new calorimeters covering ...the quadrupoles area. To improve the reconstruction of
K
L
→
2
π
0
events with photons hitting the quadrupoles a calorimeter with high efficiency to low energy photons (20–300
MeV), time resolution of less than 1
ns and space resolution of few cm, is needed. To match these requirements, we are designing a tile calorimeter, QCALT, where each single tile is readout by SiPM for a total granularity of 2400 channels. We show first tests of the different calorimeter components.
Mu2e will search for the Charge Lepton Flavor Violating (CLFV) conversion of a muon into an electron in the field of a nucleus. A clean discovery signature is provided by the mono-energetic ...conversion electron (
E
e
= 104.96 MeV). If no events are observed, Mu2e will set a limit on the ratio between the conversion and the nuclear capture rate below 3 × 10
−17
(at 90% C.L.). In order to confirm that the observed candidate is an electron, the calorimeter resolution requirements are to provide
E
res
< 10%,
T
res
< 500 ps for 100 MeV electrons while working in vacuum and in a high radiation environment and high magnetic field. The calorimeter is made of two annular aluminum disks, each one filled with 674 pure CsI crystals read out by SiPMs. A sophisticated mechanics and cooling system has been developed to support the crystals and cool the sensors. Radiation hard analog and fast digital electronics have been developed. In this paper the QC tests performed on the produced components and the construction status are reported, as well as the results obtained on the large size prototype with test beam data and at a cosmic ray test stand.
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