The Large Enriched Germanium Experiment for Neutrinoless Double Beta Decay (LEGEND)

The observation of neutrinoless double-beta decay (0${\nu}{\beta}{\beta}$) would show that lepton number is violated, reveal that neutrinos are Majorana particles, and provide information on neutrino mass. A discovery-capable experiment covering the inverted ordering region, with effective Majorana neutrino masses of 15 - 50 meV, will require a tonne-scale experiment with excellent energy resolution and extremely low backgrounds, at the level of $\sim$0.1 count /(FWHM$\cdot$t$\cdot$yr) in the region of the signal. The current generation $^{76}$Ge experiments GERDA and the MAJORANA DEMONSTRATOR utilizing high purity Germanium detectors with an intrinsic energy resolution of 0.12%, have achieved the lowest backgrounds by over an order of magnitude in the 0${\nu}{\beta}{\beta}$ signal region of all 0${\nu}{\beta}{\beta}$ experiments. Building on this success, the LEGEND collaboration has been formed to pursue a tonne-scale $^{76}$Ge experiment. The collaboration aims to develop a phased 0${\nu}{\beta}{\beta}$ experimental program with discovery potential at a half-life approaching or at $10^{28}$ years, using existing resources as appropriate to expedite physics results.Comment: Proceedings of the MEDEX'17 meeting (Prague, May 29 - June 2, 2017

The first search for bosonic super-WIMPs with masses up to 1 MeV/c2^2 with GERDA

We present the first search for bosonic super-WIMPs as keV-scale dark matter candidates performed with the GERDA experiment. GERDA is a neutrinoless double-beta decay experiment which operates high-purity germanium detectors enriched in $^{76}$Ge in an ultra-low background environment at the Laboratori Nazionali del Gran Sasso (LNGS) of INFN in Italy. Searches were performed for pseudoscalar and vector particles in the mass region from 60 keV/c$^2$ to 1 MeV/c$^2$. No evidence for a dark matter signal was observed, and the most stringent constraints on the couplings of super-WIMPs with masses above 120 keV/c$^2$ have been set. As an example, at a mass of 150 keV/c$^2$ the most stringent direct limits on the dimensionless couplings of axion-like particles and dark photons to electrons of $g_{ae} < 3 \cdot 10^{-12}$ and ${\alpha'}/{\alpha} < 6.5 \cdot 10^{-24}$ at 90% credible interval, respectively, were obtained.Comment: 6 pages, 3 figures, submitted to Physical Review Letters, added list of authors, updated ref. [21

Активность 2-[3-(2-хлорэтил)-3-нитрозоуреидо]-1,3- пропандиола (хлонизола) в сравнении с ломустином на модели интракраниально трансплантированных опухолей у мышей

Background. Alkylating drugs have been used in tumor chemo therapy for many decades, and the search for effective compounds continues.The aim of the study was to study the activity of the developed new compound – 2-[3-(2-chloroethyl)-3-nitrosoureido]-1,3-propanediol (chlonisol) in comparison with lomustine (CCNU) from the nitrosoalkylurea group, which is similar in chemical structure, in the model of intracranially transplanted Ehrlich's tumor and sarcoma 180 in mice.Methods. According to the developed technique, 64 female mice of the BALB/c line were punctured in the skull under anesthesia and inoculated with tumor cells of Ehrlich's carcinoma or sarcoma 180 in 0.9 % sodium chloride solution. After 24 hours, the test substances were administered at the maximum tolerated doses – chlonisol (20 mg/kg, i.p.) and lomustine (50 mg/kg, orally), once. The effect was compared with the control (solvent injection).Results. Chlonisol significantly increased the median overall survival (MOS) of animals after intracranial transplantation of both Ehrlich's tumor (by 39 %) and sarcoma 180 (by 84 %) compared with control (p&lt;0.0001). Chlonisol reduced the risk of death in mice by 73 % compared to control in Ehrlich tumor transplantation and by 83 % in sarcoma 180 (p&lt;0.0001). In contrast, lomustine did not show a significant therapeutic effect in intracranial transplantation of both tumors.Conclusion. The high activity of chlonisol in comparison with lomustine gives reason to consider it as a potential cytostatic agent in the treatment of nervous system tumors.Актуальность. Алкилирующие препараты многие десятилетия используются в химиотерапии опухолей, и поиск эффективных соединений продолжается.Цель исследования изучить активность разрабатываемого нового соединения – 2-[3-(2-хлорэтил)-3-нитрозоуреидо]- 1,3-пропандиола (хлонизола) в сравнении с ломустином (CCNU) из близкой по химическому строению группы нитрозоалкилмочевины на модели интракраниально трансплантированных опухолей Эрлиха и саркомы 180 у мышей.Методы. 64 мышам самкам линии BALB/c, согласно разработанной методики, под наркозом делали прокол в черепе и инокулировали опухолевые клетки карциномы Эрлиха или саркомы 180 в 0,9 % растворе натрия хлорида. Через 24 ч вводили тестируемые вещества в максимально переносимых дозах – хлонизол (20 мг/кг, в/б) и ломустин (50 мг/кг, перорально), однократно. Эффект сравнивали с контролем (введение растворителя).Результаты. Хлонизол достоверно увеличивал медиану продолжительности жизни (МПД) животных-опухоленосителей после интракраниальной трансплантации как опухоли Эрлиха (на 39 %), так и саркомы 180 (на 84 %) по сравнению с контролем (р&lt;0,0001). Хлонизол снижал риск гибели мышей на 73 % по отношению к контролю при трансплантации опухоли Эрлиха и на 83 % – при саркоме 180 (р&lt;0,0001). В противоположность этому, ломустин не проявил достоверного терапевтического эффекта при интракраниальной трансплантации обоих опухолевых штаммов.Заключение. Высокая активность хлонизола в сравнении с ломустином даёт основание рассматривать его как потенциальный цитостатик при лечении опухолей нервной системы

Оценка противоопухолевой активности 2-[3-(2-хлорэтил)- 3-нитрозоуреидо]-1,3-пропандиола (хлонизола) у мышей C57BL/6 с трансплантированной интракраниально меланомой B16

Background. The arsenal of antitumor drug therapy for melanoma brain metastases is limited. The search and study of new agents capable to penetrate the blood-brain barrier and provide a therapeutic effect against intracranial tumors remains an unmet clinical need. The aim is to evaluate the antitumor activity of the domestic derivative of nitrosoalkylureas, chlonisol, in mice with intracranially transplanted syngeneic B16 melanoma. Methods. The experiment was carried out in 18 female inbred C57BL/6 mice. After intracranial tumor transplantation, performed according to modified technique, the animals were randomized into two groups: I. Control (n = 10) – the animals were injected with normal saline 10 ml/kg intraperitoneally; II. Chlonisol (n = 8) – the animals were treated with the test compound at a dose of 15 mg/kg in normal saline intraperitoneally. The single administration of normal saline and chlonisol was performed 24 hours after tumor transplantation. The end point of the study was overall survival (OS) of the animals. Results. Compared with the control group, administration of chlonisol significantly increased the median OS of mice from 13 to 18 days (log rank test, p = 0.0005). Chlonisol significantly decreased the risk of death by 71 % compared with the control group (HR = 0.29; 95 %CI 0.10–0.82). By the 15th day after intracranial transplantation of B16 melanoma, all 10 mice in the control group died from intracerebral tumors (100 %), whereas in the chlonisol group only 2 out of 8 (25 %) mice died (Fisher's exact test, p = 0.0015). Conclusion. Despite the exploratory nature of the present study, it provides a good starting point for further research of chlonisol in brain tumors.Актуальность. Арсенал средств противоопухолевой терапии метастазов меланомы в головной мозг ограничен. Актуальным остаётся поиск и изучение новых средств, способных проникать через гематоэнцефалический барьер и оказывать терапевтический эффект в отношении интракраниальных опухолевых очагов. Цель. Оценить противоопухолевую активность отечественного производного нитрозоалкилмочевин хлонизола у мышей с трансплантированной интракраниально сингенной меланомой B16. Методы. Эксперимент был проведён на 18 инбредных мышах самках линии C57BL/6. После интракраниальной трансплантации опухоли, выполненной по модифицированной методике, животные были рандомизированы в две группы: I. Контроль (n = 10) – животным однократно внутрибрюшинно вводили 0,9 % раствор натрия хлорида в объёме 10 мл/кг; II. Хлонизол (n = 8) – животным однократно внутрибрюшинно вводили тестируемое соединение в дозе 15 мг/кг в 0,9 % раствора натрия хлорида. Введение 0,9 % раствора натрия хлорида и хлонизола выполняли через 24 часа после трансплантации опухоли. Конечной точкой исследования была оценка общей выживаемости (ОВ) животных. Результаты. По сравнению с контрольной группой введение хлонизола значимо увеличило медиану ОВ мышей с 13 до 18 дней (логранговый тест, p = 0,0005). В группе хлонизола установлено достоверное снижение риска смерти животных на 71 % по сравнению с контрольной группой (HR = 0,29; 95% CI 0,10–0,82). К 15-му дню после интракраниальной трансплантации меланомы В16 все 10 мышей контрольной группы погибли от внутримозговой опухоли (100 %), а в группе хлонизола погибли 2 из 8 (25 %) мышей (точный критерий Фишера, p = 0,0015). Заключение. Несмотря на разведочный характер представленного исследования, его результаты могут служить обоснованием для дальнейшего изучения хлонизола при опухолевых поражениях головного мозга

Modeling of GERDA Phase II data

The GERmanium Detector Array (Gerda) experiment at the Gran Sasso underground laboratory (LNGS) of INFN is searching for neutrinoless double-beta (0\u3bd\u3b2\u3b2) decay of 76Ge. The technological challenge of Gerda is to operate in a \u201cbackground-free\u201d regime in the region of interest (ROI) after analysis cuts for the full 100 kg\ub7yr target exposure of the experiment. A careful modeling and decomposition of the full-range energy spectrum is essential to predict the shape and composition of events in the ROI around Q\u3b2\u3b2 for the 0\u3bd\u3b2\u3b2 search, to extract a precise measurement of the half-life of the double-beta decay mode with neutrinos (2\u3bd\u3b2\u3b2) and in order to identify the location of residual impurities. The latter will permit future experiments to build strategies in order to further lower the background and achieve even better sensitivities. In this article the background decomposition prior to analysis cuts is presented for Gerda Phase II. The background model fit yields a flat spectrum in the ROI with a background index (BI) of 16.04 120.85+0.78\ub710 123 cts/(keV\ub7kg\ub7yr) for the enriched BEGe data set and 14.68 120.52+0.47\ub710 123 cts/(keV\ub7kg\ub7yr) for the enriched coaxial data set. These values are similar to the one of Phase I despite a much larger number of detectors and hence radioactive hardware components

Calibration of the Gerda experiment

The GERmanium Detector Array (Gerda) collaboration searched for neutrinoless double-β decay in 76Ge with an array of about 40 high-purity isotopically-enriched germanium detectors. The experimental signature of the decay is a monoenergetic signal at Qββ= 2039.061 (7) keV in the measured summed energy spectrum of the two emitted electrons. Both the energy reconstruction and resolution of the germanium detectors are crucial to separate a potential signal from various backgrounds, such as neutrino-accompanied double-β decays allowed by the Standard Model. The energy resolution and stability were determined and monitored as a function of time using data from regular 228Th calibrations. In this work, we describe the calibration process and associated data analysis of the full Gerda dataset, tailored to preserve the excellent resolution of the individual germanium detectors when combining data over several years

LEGEND-1000 Preconceptual Design Report

We propose the construction of LEGEND-1000, the ton-scale Large Enriched Germanium Experiment for Neutrinoless $\beta \beta$ Decay. This international experiment is designed to answer one of the highest priority questions in fundamental physics. It consists of 1000 kg of Ge detectors enriched to more than 90% in the $^{76}$Ge isotope operated in a liquid argon active shield at a deep underground laboratory. By combining the lowest background levels with the best energy resolution in the field, LEGEND-1000 will perform a quasi-background-free search and can make an unambiguous discovery of neutrinoless double-beta decay with just a handful of counts at the decay $Q$ value. The experiment is designed to probe this decay with a 99.7%-CL discovery sensitivity in the $^{76}$Ge half-life of $1.3\times10^{28}$ years, corresponding to an effective Majorana mass upper limit in the range of 9-21 meV, to cover the inverted-ordering neutrino mass scale with 10 yr of live time

Final Results of GERDA on the Search for Neutrinoless Double-β\beta Decay

The GERmanium Detector Array (GERDA) experiment searched for the lepton-number-violating neutrinoless double-$\beta$ ($0\nu\beta\beta$) decay of $^{76}$Ge, whose discovery would have far-reaching implications in cosmology and particle physics. By operating bare germanium diodes, enriched in $^{76}$Ge, in an active liquid argon shield, GERDA achieved an unprecedently low background index of $5.2\times10^{-4}$ counts/(keV$\cdot$kg$\cdot$yr) in the signal region and met the design goal to collect an exposure of 100 kg$\cdot$yr in a background-free regime. When combined with the result of Phase I, no signal is observed after 127.2 kg$\cdot$yr of total exposure. A limit on the half-life of $0\nu\beta\beta$ decay in $^{76}$Ge is set at $T_{1/2}>1.8\times10^{26}$ yr at 90% C.L., which coincides with the sensitivity assuming no signal.Comment: 7 pages, 3 figures, submitted to Physical Review Letter

Final Results of GERDA on the Search for Neutrinoless Double-β Decay

The GERmanium Detector Array (GERDA) experiment searched for the lepton-number-violating neutrinoless double-β (0νββ) decay of ^{76}Ge, whose discovery would have far-reaching implications in cosmology and particle physics. By operating bare germanium diodes, enriched in ^{76}Ge, in an active liquid argon shield, GERDA achieved an unprecedently low background index of 5.2×10^{-4} counts/(keV kg yr) in the signal region and met the design goal to collect an exposure of 100 kg yr in a background-free regime. When combined with the result of Phase I, no signal is observed after 127.2 kg yr of total exposure. A limit on the half-life of 0νββ decay in ^{76}Ge is set at T_{1/2}>1.8×10^{26}  yr at 90% C.L., which coincides with the sensitivity assuming no signal