Low background experiments need a suppression of cosmogenically induced events. The
Gerda
experiment located at
Lngs
is searching for the
0
ν
β
β
decay of
76
Ge. It is equipped with an active muon ...veto the main part of which is a water Cherenkov veto with 66 PMTs in the water tank surrounding the
Gerda
cryostat. With this system 806 live days have been recorded, 491 days were combined muon–germanium data. A muon detection efficiency of
ε
μ
d
=
(
99.935
±
0.015
)
% was found in a Monte Carlo simulation for the muons depositing energy in the germanium detectors. By examining coincident muon–germanium events a rejection efficiency of
ε
μ
r
=
(
99
.
2
-
0.4
+
0.3
)
% was found. Without veto condition the muons by themselves would cause a background index of
BI
μ
=
(
3.16
±
0.85
)
×
10
-
3
cts
/
(
keV
·
kg
·
year
)
at
Q
β
β
.
Many extensions of the Standard Model of particle physics explain the dominance of matter over antimatter in our Universe by neutrinos being their own antiparticles. This would imply the existence of ...neutrinoless double-β decay, which is an extremely rare lepton-number-violating radioactive decay process whose detection requires the utmost background suppression. Among the programmes that aim to detect this decay, the GERDA Collaboration is searching for neutrinoless double-β decay of
Ge by operating bare detectors, made of germanium with an enriched
Ge fraction, in liquid argon. After having completed Phase I of data taking, we have recently launched Phase II. Here we report that in GERDA Phase II we have achieved a background level of approximately 10
counts keV
kg
yr
. This implies that the experiment is background-free, even when increasing the exposure up to design level. This is achieved by use of an active veto system, superior germanium detector energy resolution and improved background recognition of our new detectors. No signal of neutrinoless double-β decay was found when Phase I and Phase II data were combined, and we deduce a lower-limit half-life of 5.3 × 10
years at the 90 per cent confidence level. Our half-life sensitivity of 4.0 × 10
years is competitive with the best experiments that use a substantially larger isotope mass. The potential of an essentially background-free search for neutrinoless double-β decay will facilitate a larger germanium experiment with sensitivity levels that will bring us closer to clarifying whether neutrinos are their own antiparticles.
Upgrade for Phase II of the Gerda experiment Agostini, M.; Bakalyarov, A. M.; Balata, M. ...
The European physical journal. C, Particles and fields,
05/2018, Volume:
78, Issue:
5
Journal Article
Peer reviewed
Open access
The
Gerda
collaboration is performing a sensitive search for neutrinoless double beta decay of
76
Ge
at the INFN Laboratori Nazionali del Gran Sasso, Italy. The upgrade of the
Gerda
experiment from ...Phase I to Phase II has been concluded in December 2015. The first Phase II data release shows that the goal to suppress the background by one order of magnitude compared to Phase I has been achieved.
Gerda
is thus the first experiment that will remain “background-free” up to its design exposure (
100 kg
year
). It will reach thereby a half-life sensitivity of more than
10
26
year within 3 years of data collection. This paper describes in detail the modifications and improvements of the experimental setup for Phase II and discusses the performance of individual detector components.
A Part I in a series of articles on liability, negligence, and all things in between is presented. Among other things, there are various reasons of it--for example, breach of contract, medical ...negligence, or an intentional assault--but one concept predominates. Liability means that the party in the wrong must do something--most of the time, pay money--to return the injured party to his pre-injury state.
Falkenstein discusses two important legal doctrines, available to varying degrees in different states, that may shield one and his agency from liability even if one's negligence, in one's capacity as ...an environmental health professional, causes an injury. The first is called the "public-duty doctrine," and the second is the conecept of "immunity." Details are presented.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The GERmanium Detector Array (Gerda) at the Gran Sasso Underground Laboratory (LNGS) searches for the neutrinoless double ...beta decay (...) of ...Ge. Germanium detectors made of material with an enriched ...Ge fraction act simultaneously as sources and detectors for this decay. During Phase I of theexperiment mainly refurbished semi-coaxial Ge detectors from former experiments were used. For the upcoming Phase II, 30 new ...Ge enriched detectors of broad energy germanium (BEGe)-type were produced. A subgroup of these detectors has already been deployed in Gerda during Phase I. The present paper reviews the complete production chain of these BEGe detectors including isotopic enrichment, purification, crystal growth and diode production. The efforts in optimizing the mass yield and in minimizing the exposure of the ...Ge enriched germanium to cosmic radiation during processing are described. Furthermore, characterization measurements in vacuum cryostats of the first subgroup of seven BEGe detectors and their long-term behavior in liquid argon are discussed. The detector performance fulfills the requirements needed for the physics goals of Gerda Phase II.
The Gerda experiment at Lngs of INFN is equipped with an active muon veto. The main part of the system is a water Cherenkov veto with 66 PMTs in the water tank surrounding the Gerda cryostat. The ...muon flux recorded by this veto shows a seasonal modulation. Two causes have been identified: (i) secondary muons from the Cngs neutrino beam (2.2%) and (ii) a temperature modulation of the atmosphere (1.4%). A mean cosmic muon rate of Iμ0=(3.477±0.002stat±0.067sys)×10−4/(s · m2) was found in good agreement with other experiments at Lngs. Combining the present result with those from previous experiments at Lngs the effective temperature coefficient αT,Lngs is determined to 0.93 ± 0.03. A fit of the temperature coefficients measured at various underground sites yields a kaon to pion ratio rK/π of 0.10 ± 0.03.
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