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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.

The Gerda collaboration is performing a sensitive search for neutrinoless double beta decay of 76Ge 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 kgyear). It will reach thereby a half-life sensitivity of more than 1026 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 detectors are made from germanium with the fraction of the 76Ge isotope enriched from 7.8% to about 87%. Since the source and the detector of Ovßß decay are identical in this calorimetric approach, the detection efficiency is high. A rock overburden of about 3,500 m water equivalent removes the hadronic components of cosmic ray showers and reduces the muon flux at the experiment by six orders of magnitude, to 1.2 muons m-2 h-1.

A search for neutrinoless ... decay processes accompanied with Majoron emission has been performed using data collected during Phase I of the GERmanium Detector Array (GERDA) experiment at the Laboratori Nazionali del Gran Sasso of INFN (Italy). Processes with spectral indices ... were searched for. No signals were found and lower limits of the order of 10... yr on their half-lives were derived, yielding substantially improved results compared to previous experiments with ...Ge. A new result for the half-life of the neutrino-accompanied ... decay of ...Ge with significantly reduced uncertainties is also given, resulting in ... yr.

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The GERmanium Detector Array (Gerda) experiment at the Gran Sasso underground laboratory (LNGS) of INFN is searching for neutrinoless double beta (...) decay of ...Ge. The signature of the signal is a monoenergetic peak at 2039 keV, the ... value of the decay. To avoid bias in the signal search, the present analysis does not consider all those events, that fall in a 40 keV wide region centered around ... The main parameters needed for the ... analysis are described. A background model was developed to describe the observed energy spectrum. The model contains several contributions, that are expected on the basis of material screening or that are established by the observation of characteristic structures in the energy spectrum. The model predicts a flat energy spectrum for the blinding window around ... with a background index ranging from 17.6 to 23.8 ... ... cts/(keV kg yr). A part of the data not considered before has been used to test if the predictions of the background model are consistent. The observed number of events in this energy region is consistent with the background model. The background at ... is dominated by close sources, mainly due to ...K, ...Bi, ...Th, ...Co and ... emitting isotopes from the ...Ra decay chain. The individual fractions depend on the assumed locations of the contaminants. It is shown, that after removal of the known ... peaks, the energy spectrum can be fitted in an energy range of 200 keV around ... with a constant background. This gives a background index consistent with the full model and uncertainties of the same size.