A search for μ-e conversion in muonic gold Bertl, W.; Engfer, R.; Hermes, E.A. ...
The European physical journal. C, Particles and fields,
8/2006, Letnik:
47, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We report on a search for μ-e conversion in muonic gold performed with the SINDRUM II spectrometer at PSI. The measurement resulted in Γ(μ-Au→e-Aug.s.)/Γcapture(μ-Au)<7×10-13 (90% C.L.).
Experimental results on pion decays obtained with the PIBETA spectrometer at the Paul Scherrer Institute (PSI) are reviewed. For pion beta decay π
+
→ π
0
е
+
ν (πβ), a precision measurement of ...relative probability yields Г(πβ) = 1.036 ± 0.004(stat) ± 0.004(syst) ± 0.003(π
+
→е
+
ν) × 10
–8
, which implies
V
ud
= 0.9728(30) for the corresponding element of the Cabibbo–Kobayashi–Maskawa mixing matrix. Using a sample of 65 × 10
3
events, relative probability of the π
+
→е
+
νγ radiative pion decay (RPD) in the kinematic region of
E
γ
> 10 MeV and
θ
eγ
> 40° is measured as
B
exp
= 73.86(54) × 10
–8
. A statistical analysis of measured
E
e
+
and
E
γ
distributions for this decay yield the values
F
V
= 0.0258(17) and
F
A
= 0.0117(17) for the pion weak formfactors. Assuming that
F
V
linearly depends on the е
+
ν invariant mass
q
2
as
F
V
(
q
2
) =
F
V
(0)(1 +
aq
2
), the slope parameter is extracted as
а
= 0.10(6). The pion polarizability and neutral-pion lifetime are estimated as
α
E
= 2.78(10) × 10
–4
fm
3
and τ(π
0
) = (8.5 ± 1.1) × 10
–17
s, respectively. The data for decays π
+
→ е
+
ν and
μ
+
→
e
+
v
v
¯
γ
have been collected and are being processed. The follow-up PEN experiment aims at reducing the uncertainty on the π
+
→ е
+
ν relative probability by almost an order of magnitude (to 5 × 10
–4
).
CMS barrel pixel detector overview Kästli, H.Chr; Bertl, W.; Erdmann, W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2007, Letnik:
582, Številka:
3
Journal Article
Recenzirano
The pixel detector is the innermost tracking device of the CMS experiment at the LHC. It is built from two independent subdevices, the pixel barrel and the end disks. The barrel consists of three ...concentric layers around the beam pipe with mean radii of 4.4, 7.3 and 10.2
cm. There are two end disks on each side of the interaction point at
±
34.5
and
±
46.5
cm
.
This article gives an overview of the pixel barrel detector, its mechanical support structure, electronics components, services and its expected performance.
Upgrade plans for the CMS pixel barrel detector Erdmann, W.; Bertl, W.; Horisberger, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2010, Letnik:
617, Številka:
1
Journal Article
Recenzirano
The pixel detector of the CMS experiment will need to be replaced after a couple of years of LHC running because of radiation damage. On the other hand, plans for a step wise luminosity upgrade of ...the accelerator beyond the present design value around 2014 are being prepared. While the replacement pixel detector must be designed to handle increased particle rates, it should maintain or improve the tracking performance of the present system and must be compatible with existing services.
Design, commissioning and performance of the PIBETA detector at PSI Frlež, E; Počanić, D; Assamagan, K.A ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2004, Letnik:
526, Številka:
3
Journal Article
Recenzirano
We describe the design, construction and performance of the PIBETA detector built for the precise measurement of the branching ratio of pion beta decay, π
+→π
0e
+ν
e, at the Paul Scherrer Institute. ...The central part of the detector is a 240-module spherical pure CsI calorimeter covering
∼3
π
sr
solid angle. The calorimeter is supplemented with an active collimator/beam degrader system, an active segmented plastic target, a pair of low-mass cylindrical wire chambers and a 20-element cylindrical plastic scintillator hodoscope. The whole detector system is housed inside a temperature-controlled lead brick enclosure, which in turn is lined with cosmic muon plastic veto counters. Commissioning and calibration data were taken during two 3-month beam periods in 1999/2000 with π
+ stopping rates between
1.3·10
3
π
+/
s
and
1.3·10
6
π
+/
s
. We examine the timing, energy and angular detector resolution for photons, positrons and protons in the energy range of 5–
150
MeV
, as well as the response of the detector to cosmic muons. We illustrate the detector signatures for the assorted rare pion and muon decays and their associated backgrounds.
Design and test of the CMS pixel readout chip Barbero, M.; Bertl, W.; Dietrich, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2004, Letnik:
517, Številka:
1
Journal Article
Recenzirano
The readout chip for the CMS pixel detector must handle an enormous flux of data, while keeping the data loss at a minimum. Full size prototype readout chips bump-bonded to sensors have been tested ...in a pion beam simulating an LHC-like environment, and the data loss as a function of particle fluence has been measured.
We have measured the pi+-->e+ nugamma branching ratio over a wide region of phase space, based on a total of 65 460 events acquired using the PIBETA detector. Minimum-chi2 fits to the measured ...(E(e+), E(gamma) energy distributions result in the weak form factor value of F(A)=0.0119(1) with a fixed value of F(V)=0.0259. An unconstrained fit yields F(V)=0.0258(17) and F(A)=0.0117(17). In addition, we have measured a=0.10(6) for the dependence of F(V) on q2, the e+ nu pair invariant mass squared, parametrized as F(V)(q2)=F(V)(0)(1+aq(2)). The branching ratio for the kinematic region E(gamma)>10 MeV and theta(e(+)gamma)>40 degrees is measured to be B(expt)=73.86(54)x10(-8). Earlier deviations we reported in the high-E(gamma)-low-E(e+) kinematic region are resolved without a tensor term. We also derive new values for the pion polarizability alpha(E)=2.78(10)x10(-4) fm3 and neutral pion lifetime tau(pi0)=(8.5+/-1.1)x10(-17) s.
The SINDRUM II spectrometer at PSI is used in searches for
μ→
e conversion in muonic atoms. Here we report on a search for the charge-changing
μ
−→
e
+ conversion on titanium. The measurements ...yielded the new upper limits
Γ(
μ
−Ti →
e
+Ca
GS
)/
Γ(
μ
−Ti capture)<1.7×10
−12 (90% CL) for the ground state transition and
Γ(
μ
−Ti →
e
+Ca
GDR
)/
Γ(
μ
−Ti capture)<3.6×10
−11 (90% CL) for a giant dipole resonance excitation with both a mean energy and a width of 20 MeV. These results improve on our previous best limits by a factor of 2.5.
PDF
