55 research outputs found
Phenomenology of a Pseudo-Scalar Inflaton: Naturally Large Nongaussianity
Many controlled realizations of chaotic inflation employ pseudo-scalar
axions. Pseudo-scalars \phi are naturally coupled to gauge fields through c
\phi F \tilde{F}. In the presence of this coupling, gauge field quanta are
copiously produced by the rolling inflaton. The produced gauge quanta, in turn,
source inflaton fluctuations via inverse decay. These new cosmological
perturbations add incoherently with the "vacuum" perturbations, and are highly
nongaussian. This provides a natural mechanism to generate large nongaussianity
in single or multi field slow-roll inflation. The resulting phenomenological
signatures are highly distinctive: large nongaussianity of (nearly) equilateral
shape, in addition to detectably large values of both the scalar spectral tilt
and tensor-to-scalar ratio (both being typical of large field inflation). The
WMAP bound on nongaussianity implies that the coupling, c, of the pseudo-scalar
inflaton to any gauge field must be smaller than about 10^{2} M_p^{-1}.Comment: 45 pages, 7 figure
Effects and Detectability of Quasi-Single Field Inflation in the Large-Scale Structure and Cosmic Microwave Background
Quasi-single field inflation predicts a peculiar momentum dependence in the
squeezed limit of the primordial bispectrum which smoothly interpolates between
the local and equilateral models. This dependence is directly related to the
mass of the isocurvatons in the theory which is determined by the
supersymmetry. Therefore, in the event of detection of a non-zero primordial
bispectrum, additional constraints on the parameter controlling the
momentum-dependence in the squeezed limit becomes an important question. We
explore the effects of these non-Gaussian initial conditions on large-scale
structure and the cosmic microwave background, with particular attention to the
galaxy power spectrum at large scales and scale-dependence corrections to
galaxy bias. We determine the simultaneous constraints on the two parameters
describing the QSF bispectrum that we can expect from upcoming large-scale
structure and cosmic microwave background observations. We find that for
relatively large values of the non-Gaussian amplitude parameters, but still
well within current uncertainties, galaxy power spectrum measurements will be
able to distinguish the QSF scenario from the predictions of the local model. A
CMB likelihood analysis, as well as Fisher matrix analysis, shows that there is
also a range of parameter values for which Planck data may be able distinguish
between QSF models and the related local and equilateral shapes. Given the
different observational weightings of the CMB and LSS results, degeneracies can
be significantly reduced in a joint analysis.Comment: 27 pages, 14 figure
Low-diffusion Xe-He gas mixtures for rare-event detection: electroluminescence yield
High pressure xenon Time Projection Chambers (TPC) based on secondary scintillation (electroluminescence) signal amplification are being proposed for rare event detection such as directional dark matter, double electron capture and double beta decay detection. The discrimination of the rare event through the topological signature of primary ionisation trails is a major asset for this type of TPC when compared to single liquid or double-phase TPCs, limited mainly by the high electron diffusion in pure xenon. Helium admixtures with xenon can be an attractive solution to reduce the electron diffu- sion significantly, improving the discrimination efficiency of these optical TPCs. We have measured the electroluminescence (EL) yield of Xe–He mixtures, in the range of 0 to 30% He and demonstrated the small impact on the EL yield of the addition of helium to pure xenon. For a typical reduced electric field of 2.5 kV/cm/bar in the EL region, the EL yield is lowered by ∼ 2%, 3%, 6% and 10% for 10%, 15%, 20% and 30% of helium concentration, respectively. This decrease is less than what has been obtained from the most recent simulation framework in the literature. The impact of the addition of helium on EL statistical fluctuations is negligible, within the experimental uncertainties. The present results are an important benchmark for the simulation tools to be applied to future optical TPCs based on Xe-He mixtures. [Figure not available: see fulltext.]
Demonstration of the event identification capabilities of the NEXT-White detector
[EN] In experiments searching for neutrinoless double-beta decay, the possibility of identifying the two emitted electrons is a powerful tool in rejecting background events and therefore improving the overall sensitivity of the experiment. In this paper we present the first measurement of the efficiency of a cut based on the different event signatures of double and single electron tracks, using the data of the NEXT-White detector, the first detector of the NEXT experiment operating underground. Using a 228Th calibration source to produce signal-like and background-like events with energies near 1.6 MeV, a signal efficiency of 71.6 ± 1.5 stat ± 0.3 sys% for a background acceptance of 20.6 ± 0.4 stat ± 0.3 sys% is found, in good agreement with Monte Carlo simulations. An extrapolation to the energy region of the neutrinoless double beta decay by means of Monte Carlo simulations is also carried out, and the results obtained show an improvement in background rejection over those obtained at lower energies.The NEXT Collaboration acknowledges support from the following agencies and institutions: the European Research Council (ERC) under the Advanced Grant 339787NEXT; the European Union's Framework Programme for Research and Innovation Horizon 2020 (2014-2020) under the Marie Sklodowska-Curie Grant Agreements No. 674896, 690575 and 740055; the Ministerio de Economia y Competitividad and the Ministerio de Ciencia, Innovacion y Universidades of Spain under grants FIS2014-53371-C04, RTI2018-095979, the Severo Ochoa Program SEV-2014-0398 and the Maria de Maetzu Program MDM-2016-0692; the GVA of Spain under grants PROMETEO/2016/120 and SEJI/2017/011; the Portuguese FCT under project PTDC/FIS-NUC/2525/2014, under project UID/FIS/04559/2013 to fund the activities of LIBPhys, and under grants PD/BD/FBD/105921/2014, SFRH/BPD/109180/2015 and SFRH/BPD/76842/2011; the U.S. Department of Energy under contracts number DE-AC02-06CH11357 (Argonne National Laboratory), DE-AC02-07CH11359 (Fermi National Accelerator Laboratory), DE-FG02-13ER42020 (Texas A&M) and DE-SC0019223/DE-SC0019054 (University of Texas at Arlington); and the University of Texas at Arlington. DGD acknowledges Ramon y Cajal program (Spain) under contract number RYC-2015-18820. We also warmly acknowledge the Laboratori Nazionali del Gran Sasso (LNGS) and the Dark Side collaboration for their help with TPB coating of various parts of the NEXT-White TPC. Finally, we are grateful to the Laboratorio Subterraneo de Canfranc for hosting and supporting the NEXT experiment.Ferrario, P.; Benlloch-Rodríguez, J.; Díaz López, G.; Hernando Morata, J.; Kekic, M.; Renner, J.; Usón, A.... (2019). Demonstration of the event identification capabilities of the NEXT-White detector. Journal of High Energy Physics (Online). (10):1-17. https://doi.org/10.1007/JHEP10(2019)052S11710M. Fukugita and T. Yanagida, Baryogenesis without grand unification, Phys. Lett.B 174 (1986) 45 [ INSPIRE ].EXO-200 collaboration, Improved measurement of the 2νββ half-life of136Xe with the EXO-200 detector, Phys. Rev.C 89 (2014) 015502 [ arXiv:1306.6106 ] [ INSPIRE ].XENON collaboration, Dark matter search results from a one ton-year exposure of XENON1T, Phys. Rev. Lett.121 (2018) 111302 [ arXiv:1805.12562 ] [ INSPIRE ].Caltech-Neuchâtel-PSI collaboration, Search for ββ decay in136Xe: new results from the Gotthard experiment, Phys. Lett.B 434 (1998) 407 [ INSPIRE ].NEXT collaboration, First proof of topological signature in the high pressure xenon gas TPC with electroluminescence amplification for the NEXT experiment, JHEP01 (2016) 104 [ arXiv:1507.05902 ] [ INSPIRE ].NEXT collaboration, The Next White (NEW) detector, 2018 JINST13 P12010 [ arXiv:1804.02409 ] [ INSPIRE ].M. Redshaw, E. Wingfield, J. McDaniel and E.G. Myers, Mass and double-beta-decay Q value of136Xe, Phys. Rev. Lett.98 (2007) 053003 [ INSPIRE ].NEXT collaboration, Initial results on energy resolution of the NEXT-White detector, 2018 JINST13 P10020 [ arXiv:1808.01804 ] [ INSPIRE ].NEXT collaboration, Energy calibration of the NEXT-White detector with 1% resolution near Qββ of136Xe, arXiv:1905.13110 [ INSPIRE ].NEXT collaboration, Electron drift properties in high pressure gaseous xenon, 2018 JINST13 P07013 [ arXiv:1804.01680 ] [ INSPIRE ].T.H. Cormen, C. Stein, R.L. Rivest and C.E. Leiserson, Introduction to algorithms, 2nd ed., McGraw-Hill Higher Education, U.S.A. (2001).NEXT collaboration, Calibration of the NEXT-White detector using83mKr decays, 2018 JINST13 P10014 [ arXiv:1804.01780 ] [ INSPIRE ].J. Martín-Albo, The NEXT experiment for neutrinoless double beta decay searches, Ph.D. thesis, Valencia U., IFIC, Valencia, Spain (2015).GEANT4 collaboration, GEANT4: a simulation toolkit, Nucl. Instrum. Meth.A 506 (2003) 250 [ INSPIRE ].J.J. Gomez-Cadenas et al., Sense and sensitivity of double beta decay experiments, JCAP06 (2011) 007 [ arXiv:1010.5112 ] [ INSPIRE ].NEXT collaboration, Radiogenic backgrounds in the NEXT double beta decay experiment, arXiv:1905.13625 [ INSPIRE ].NEXT collaboration, Background rejection in NEXT using deep neural networks, 2017 JINST12 T01004 [ arXiv:1609.06202 ] [ INSPIRE ].NEXT collaboration, Application and performance of an ML-EM algorithm in NEXT, 2017 JINST12 P08009 [ arXiv:1705.10270 ] [ INSPIRE ].NEXT collaboration, Secondary scintillation yield of xenon with sub-percent levels of CO2 additive for rare-event detection, Phys. Lett.B 773 (2017) 663 [ arXiv:1704.01623 ] [ INSPIRE ].NEXT collaboration, Electroluminescence TPCs at the thermal diffusion limit, JHEP01 (2019) 027 [ arXiv:1806.05891 ] [ INSPIRE ].R. Felkai et al., Helium-xenon mixtures to improve the topological signature in high pressure gas xenon TPCs, Nucl. Instrum. Meth.A 905 (2018) 82 [ arXiv:1710.05600 ] [ INSPIRE ].NEXT collaboration, Electron drift and longitudinal diffusion in high pressure xenon-helium gas mixtures, 2019 JINST14 P08009 [ arXiv:1902.05544 ] [ INSPIRE ].NEXT collaboration, Sensitivity of NEXT-100 to neutrinoless double beta decay, JHEP05 (2016) 159 [ arXiv:1511.09246 ] [ INSPIRE ].J. Muñoz Vidal, The NEXT path to neutrino inverse hierarchy, Ph.D. thesis, Valencia U., IFIC, Valencia, Spain (2018)
Sensitivity of the NEXT experiment to Xe-124 double electron capture
Double electron capture by proton-rich nuclei is a second-order nuclear process analogous to double beta decay. Despite their similarities, the decay signature is quite different, potentially providing a new channel to measure the hypothesized neutrinoless mode of these decays. The Standard-Model-allowed two-neutrino double electron capture (2¿EC EC) has been predicted for a number of isotopes, but only observed in 78Kr, 130Ba and, recently, 124Xe. The sensitivity to this decay establishes a benchmark for the ultimate experimental goal, namely the potential to discover also the lepton-number-violating neutrinoless version of this process, 0¿EC EC. Here we report on the current sensitivity of the NEXT-White detector to 124Xe 2¿EC EC and on the extrapolation to NEXT-100. Using simulated data for the 2¿EC EC signal and real data from NEXT-White operated with 124Xe-depleted gas as background, we define an optimal event selection that maximizes the NEXT-White sensitivity. We estimate that, for NEXT-100 operated with xenon gas isotopically enriched with 1 kg of 124Xe and for a 5-year run, a sensitivity to the 2¿EC EC half-life of 6 × 1022 y (at 90% confidence level) or better can be reached. [Figure not available: see fulltext.
Efeito da rotação de culturas, da monocultura e da densidade de plantas na incidência das podridões da base do colmo e no rendimento de grãos do milho
Energy calibration of the NEXT-White detector with 1% resolution near Qßß of 136Xe
Excellent energy resolution is one of the primary advantages of electroluminescent high-pressure xenon TPCs. These detectors are promising tools in searching for rare physics events, such as neutrinoless double-beta decay (ßß0¿), which require precise energy measurements. Using the NEXT-White detector, developed by the NEXT (Neutrino Experiment with a Xenon TPC) collaboration, we show for the first time that an energy resolution of 1% FWHM can be achieved at 2.6 MeV, establishing the present technology as the one with the best energy resolution of all xenon detectors for ßß0¿ searches. [Figure not available: see fulltext
Low-diffusion Xe-He gas mixtures for rare-event detection: electroluminescence yield
High pressure xenon Time Projection Chambers (TPC) based on secondary scintillation (electroluminescence) signal amplification are being proposed for rare event detection such as directional dark matter, double electron capture and double beta decay detection. The discrimination of the rare event through the topological signature of primary ionisation trails is a major asset for this type of TPC when compared to single liquid or double-phase TPCs, limited mainly by the high electron diffusion in pure xenon. Helium admixtures with xenon can be an attractive solution to reduce the electron diffu- sion significantly, improving the discrimination efficiency of these optical TPCs. We have measured the electroluminescence (EL) yield of Xe–He mixtures, in the range of 0 to 30% He and demonstrated the small impact on the EL yield of the addition of helium to pure xenon. For a typical reduced electric field of 2.5 kV/cm/bar in the EL region, the EL yield is lowered by ~ 2%, 3%, 6% and 10% for 10%, 15%, 20% and 30% of helium concentration, respectively. This decrease is less than what has been obtained from the most recent simulation framework in the literature. The impact of the addition of helium on EL statistical fluctuations is negligible, within the experimental uncertainties. The present results are an important benchmark for the simulation tools to be applied to future optical TPCs based on Xe-He mixtures
Radiogenic backgrounds in the NEXT double beta decay experiment
Natural radioactivity represents one of the main backgrounds in the search for neutrinoless double beta decay. Within the NEXT physics program, the radioactivity- induced backgrounds are measured with the NEXT-White detector. Data from 37.9 days of low-background operations at the Laboratorio Subterráneo de Canfranc with xenon depleted in 136Xe are analyzed to derive a total background rate of (0.84±0.02) mHz above 1000 keV. The comparison of data samples with and without the use of the radon abatement system demonstrates that the contribution of airborne-Rn is negligible. A radiogenic background model is built upon the extensive radiopurity screening campaign conducted by the NEXT collaboration. A spectral fit to this model yields the specific contributions of 60Co, 40K, 214Bi and 208Tl to the total background rate, as well as their location in the detector volumes. The results are used to evaluate the impact of the radiogenic backgrounds in the double beta decay analyses, after the application of topological cuts that reduce the total rate to (0.25±0.01) mHz. Based on the best-fit background model, the NEXT-White median sensitivity to the two-neutrino double beta decay is found to be 3.5s after 1 year of data taking. The background measurement in a Qßß±100 keV energy window validates the best-fit background model also for the neutrinoless double beta decay search with NEXT-100. Only one event is found, while the model expectation is (0.75±0.12) events
Mitigation of backgrounds from cosmogenic 137Xe in xenon gas experiments using 3He neutron capture
136Xe is used as the target medium for many experiments searching for 0¿ßß. Despite underground operation, cosmic muons that reach the laboratory can produce spallation neutrons causing activation of detector materials. A potential background that is difficult to veto using muon tagging comes in the form of 137Xe created by the capture of neutrons on 136Xe. This isotope decays via beta decay with a half-life of 3.8 min and a Q ß of ~4.16 MeV. This work proposes and explores the concept of adding a small percentage of 3He to xenon as a means to capture thermal neutrons and reduce the number of activations in the detector volume. When using this technique we find the contamination from 137Xe activation can be reduced to negligible levels in tonne and multi-tonne scale high pressure gas xenon neutrinoless double beta decay experiments running at any depth in an underground laboratory
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