82 research outputs found
Traintracks Through Calabi-Yaus: Amplitudes Beyond Elliptic Polylogarithms
We describe a family of finite, four-dimensional, -loop Feynman integrals
that involve weight- hyperlogarithms integrated over -dimensional
elliptically fibered varieties we conjecture to be Calabi-Yau. At three loops,
we identify the relevant K3 explicitly; and we provide strong evidence that the
four-loop integral involves a Calabi-Yau threefold. These integrals are
necessary for the representation of amplitudes in many theories---from massless
theory to integrable theories including maximally supersymmetric
Yang-Mills theory in the planar limit---a fact we demonstrate.Comment: 4+2 pages, 4 figures; references adde
The first search for bosonic super-WIMPs with masses up to 1 MeV/c 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 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 to 1
MeV/c. 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 have been set. As an example, at a mass of 150 keV/c the most
stringent direct limits on the dimensionless couplings of axion-like particles
and dark photons to electrons of and
at 90% credible interval,
respectively, were obtained.Comment: 6 pages, 3 figures, submitted to Physical Review Letters, added list
of authors, updated ref. [21
Search for tri-nucleon decays of ^{76}Ge in GERDA
We search for tri-nucleon decays of 76Ge in the dataset from the GERmanium Detector Array (GERDA) experiment. Decays that populate excited levels of the daughter nucleus above the threshold for particle emission lead to disintegration and are not considered. The ppp-, ppn-, and pnn-decays lead to 73Cu, 73Zn, and 73Ga nuclei, respectively. These nuclei are unstable and eventually proceed by the beta decay of 73Ga to 73Ge (stable). We search for the 73Ga decay exploiting the fact that it dominantly populates the 66.7 keV 73mGa state with half-life of 0.5 s. The nnn-decays of 76Ge that proceed via 73mGe are also included in our analysis. We find no signal candidate and place a limit on the sum of the decay widths of the inclusive tri-nucleon decays that corresponds to a lower lifetime limit of 1.2×1026 yr  (90% credible interval). This result improves previous limits for tri-nucleon decays by one to three orders of magnitude
Final Results of GERDA on the Search for Neutrinoless Double- Decay
The GERmanium Detector Array (GERDA) experiment searched for the
lepton-number-violating neutrinoless double- () decay of
Ge, whose discovery would have far-reaching implications in cosmology
and particle physics. By operating bare germanium diodes, enriched in
Ge, in an active liquid argon shield, GERDA achieved an unprecedently
low background index of counts/(keVkgyr) in
the signal region and met the design goal to collect an exposure of 100
kgyr in a background-free regime. When combined with the result of Phase
I, no signal is observed after 127.2 kgyr of total exposure. A limit on
the half-life of decay in Ge is set at
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
Characterization of inverted coaxial Ge detectors in GERDA for future double- decay experiments
Neutrinoless double- decay of Ge is searched for with germanium
detectors where source and detector of the decay are identical. For the success
of future experiments it is important to increase the mass of the detectors. We
report here on the characterization and testing of five prototype detectors
manufactured in inverted coaxial (IC) geometry from material enriched to 88% in
Ge. IC detectors combine the large mass of the traditional semi-coaxial
Ge detectors with the superior resolution and pulse shape discrimination power
of point contact detectors which exhibited so far much lower mass. Their
performance has been found to be satisfactory both when operated in vacuum
cryostat and bare in liquid argon within the GERDA setup. The measured
resolutions at the Q-value for double- decay of Ge
(Q = 2039 keV) are about 2.1 keV full width at half maximum in
vacuum cryostat. After 18 months of operation within the ultra-low background
environment of the GERmanium Detector Array (GERDA) experiment and an
accumulated exposure of 8.5 kgyr, the background index after analysis
cuts is measured to be counts
/(keVkgyr) around Q. This work confirms the
feasibility of IC detectors for the next-generation experiment LEGEND.Comment: 13 pages, 12 figures, submitted to EPJ
- …