Status of Pion Decay Experiments Numao, T
Journal of physics. Conference series,
11/2016, Letnik:
770, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The branching ratio of pion decays, , has provided a sensitive test of electron-muon universality in weak interactions. The uncertainty of the Standard Model prediction is at a 0.01% level. Although ...a recent measurement, Re/μ = (1.2344 ± 0.0023(stat) ± 0.0019(syst)) × 10-4, reduced the experimental uncertainty by a factor of two, there is room for improvement by more than an order of magnitude. The status of two experiments at TRIUMF and PSI as well as related pion decay experiments is presented.
In the present work of the PIENU experiment, heavy neutrinos were sought in pion decays π+→μ+ν at rest by examining the observed muon energy spectrum for extra peaks in addition to the expected peak ...for a light neutrino. No evidence for heavy neutrinos was observed. Upper limits were set on the neutrino mixing matrix |Uμi|2 in the neutrino mass region of 15.7–33.8 MeV/c2, improving on previous results by an order of magnitude.
The NA62 experiment collected a large sample of charged kaon decays in 2007 with a highly efficient trigger for decays into electrons. A measurement of the π0 electromagnetic transition form factor ...slope parameter from 1.11×106 fully reconstructed K±→π±πD0, πD0→e+e−γ events is reported. The measured value a=(3.68±0.57)×10−2 is in good agreement with theoretical expectations and previous measurements, and represents the most precise experimental determination of the slope in the time-like momentum transfer region.
Study of a large NaI(Tl) crystal Aguilar-Arevalo, A.; Aoki, M.; Blecher, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2010, Letnik:
621, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Using a narrow band positron beam, the response of a large high-resolution NaI(Tl) crystal to an incident positron beam was measured. It was found that nuclear interactions cause the appearance of ...additional peaks in the low energy tail of the deposited energy spectrum.
The PIENU experiment aims to measure the branching ratio of the charged pion decay with precision of < 0.1 %. This measurement is much sensitive to search for massive neutrinos coupled to electrons ...in
π
+
→
e
+
ν
e
decay. The initial analysis was completed and the upper limit on the neutrino mixing parameter |
U
e
i
|
2
in the neutrino mass range of 0 to 55 MeV/
c
2
was improved by a factor of 1.5, and the sensitivity for the mass range of 68 to 129 MeV/
c
2
was improve by a factor of up to 4.
The pion branching ratio,
R
π
=
Γ
(
π
+
→
e
+
ν
e
+
π
+
→
e
+
ν
e
γ
)
Γ
(
π
+
→
μ
+
ν
μ
+
π
+
→
μ
+
ν
μ
γ
)
, provides a sensitive test of lepton universality and constraints on many new physics ...scenarios. The theoretical uncertainty on the Standard Model prediction of
R
π
is 0.02 %, a factor of twenty smaller than the experimental uncertainty. The analysis of a subset of data taken by the PIENU experiment will be presented. The result,
R
π
= (1.2344 ± 0.0023(
s
t
a
t
) ± 0.0019(
s
y
s
t
)) ⋅ 10
−4
1
, is consistent with the Standard Model prediction and represents a 0.1 % constraint on lepton non-universality.
Surfactant proteins (SP)-A and SP-D are collagen-like glycoproteins belonging to the "collectin" class of C-type lectins, which are primarily synthesized in type II cells. Recent studies reported the ...possibility of local production of SP-A and SP-D in the airways, but the amounts of surfactant proteins in patients with bronchial asthma have not been studied. The composition of surfactant proteins in mild, stable asthmatics in the first lavage as bronchial lavage (BL) and the second and third lavages consecutively as alveolar lavages (AL) were therefore, analysed separately. The co-relationships in the BL between the amounts of surfactant proteins and those of fucose, which is one of the markers of submucosal secretion were also analysed. Increased amounts of SP-A in BL and AL of in asthmatics were found as compared with those in controls. A high concentration of SP-D in the AL asthma patients was also found. The levels of SP-A correlated with those of fucose in patients with bronchial asthma (r=0.849, p<0.01). The observations in the present study suggested that surfactant protein A may be secreted from the airways with allergic inflammation in a different manner from the alveoli. The increased levels of surfactant proteins A and D may play a protective role in an allergic inflammation in the pathogenesis of bronchial asthma.
Status of the PIENU experiment at TRIUMF Ito, S; Aguilar-Arevalo, A; Aoki, M ...
Journal of physics. Conference series,
07/2015, Letnik:
631, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The PIENU experiment at TRIUMF aims to measure the branching ratio of pion decays R = Γ(π+ → e+νe + π+ → e+ νeγ) Γ(π+→μ+νμ + π+ → μ+νμγ) with precision <0.1%, providing a stringent test of the ...Standard Model hypothesis of electron-muon universality and a search for new physics.
Study of rare decays is an important approach for exploring physics beyond the Standard Model (SM). The branching ratio of the helicity suppressed pion decays, R = , is one of the most accurately ...calculated decay process involving hadrons and has so far provided the most stringent test of the hypothesis of electron-muon universality in weak interactions. The branching ratio has been calculated in the SM to better than 0.01% accuracy to be RSM = 1.2353(1) × 10 . The PIENU experiment at TRIUMF, which started taking physics data in September 2009, aims to reach an accuracy five times better than the previous experiments, so as to confront the theoretical calculation at the level of ±0.1%. If a deviation from the RSM is found, "new physics" beyond the SM, at potentially very high mass scales (up to 1000 TeV), could be revealed. Alternatively, sensitive constraints on hypotheses can be obtained for interactions involving pseudoscalar or scalar interactions. So far, 4 million π+ → e+ νe ue events have been accumulated by PIENU. This paper will outline the physics motivations, describe the apparatus and techniques designed to achieve high precision and present the latest results.
Status of the PIENU experiment Numao, T; Aguilar-Arevalo, A; Aoki, M ...
Journal of physics. Conference series,
01/2014, Letnik:
556, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The branching ratio, Re/μ Γ(π → eν + eνγ)/Γ(π → μν + μνγ), provides a sensitive test of muon-electron universality in weak interactions. The status of the PIENU experiment at TRIUMF, which aims to ...improve the precision of the Re/μ measurement by a factor of > 5, is presented.
PDF
