A re-examination of the BEST Trial using composite outcomes, including emergency department visits

Objectives: The influence of choice of endpoint on trial size, duration, and interpretation of results was examined in patients with heart failure who were enrolled in BEST (Beta-blocker Evaluation of Survival Trial). Background: The choice of endpoints in heart failure trials has evolved over the past 3 decades. Methods: In the BEST trial, we used Cox regression analysis to examine the effect of bucindolol on the current standard composite of cardiovascular death or heart failure hospitalization (CVD/HFH) compared with the original primary mortality endpoint and the expanded composite that included emergency department (ED) visits. We also undertook an analysis of recurrent events primarily using the Lin, Wei, Ying, and Yang model. Results: Overall, 448 (33%) patients on placebo and 411 (30%) patients on bucindolol died (hazard ratio [HR]: 0.90; 95% confidence interval [CI]: 0.78 to 1.02; p = 0.11). A total of 730 (54%) patients experienced CVD/HFH on placebo and 624 (46%) on bucindolol (HR: 0.80; 95% CI: 0.72 to 0.89; p < 0.001). Adding ED visits increased these numbers to 768 (57%) and 668 (49%), respectively (HR: 0.81; 95% CI: 0.73 to 0.90; p < 0.001). A total of 568 (42%) patients on placebo experienced HFH compared with 476 (35%) patients on bucindolol (HR: 0.78; 95% CI: 0.69 to 0.89; p < 0.001), with a total of 1,333 and 1,124 admissions, respectively. With the same statistical assumptions, using the composite endpoint instead of all-cause mortality would have reduced the trial size by 40% and follow-up duration by 69%. The rate ratio for recurrent events (CVD/HFH) was 0.83 (95% CI: 0.73 to 0.94; p = 0.003). Conclusions: Choice of endpoint has major implications for trial size and duration, as well as interpretation of results. The value of broader composite endpoints and inclusion of recurrent events needs further investigation. (Beta Blocker Evaluation in Survival Trial [BEST]; NCT00000560

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.]

The detection of a strong episignature for Chung–Jansen syndrome, partially overlapping with Börjeson–Forssman–Lehmann and White–Kernohan syndromes

Chung-Jansen syndrome is a neurodevelopmental disorder characterized by intellectual disability, behavioral problems, obesity and dysmorphic features. It is caused by pathogenic variants in the PHIP gene that encodes for the Pleckstrin homology domain-interacting protein, which is part of an epigenetic modifier protein complex. Therefore, we hypothesized that PHIP haploinsufficiency may impact genome-wide DNA methylation (DNAm). We assessed the DNAm profiles of affected individuals with pathogenic and likely pathogenic PHIP variants with Infinium Methylation EPIC arrays and report a specific and sensitive DNAm episignature biomarker for Chung–Jansen syndrome. In addition, we observed similarities between the methylation profile of Chung–Jansen syndrome and that of functionally related and clinically partially overlapping genetic disorders, White–Kernohan syndrome (caused by variants in DDB1 gene) and Börjeson–Forssman–Lehmann syndrome (caused by variants in PHF6 gene). Based on these observations we also proceeded to develop a common episignature biomarker for these disorders. These newly defined episignatures can be used as part of a multiclass episignature classifier for screening of affected individuals with rare disorders and interpretation of genetic variants of unknown clinical significance, and provide further insights into the common molecular pathophysiology of the clinically-related Chung–Jansen, Börjeson–Forssman–Lehmann and White–Kernohan syndromes.</p

Measurement of radon-induced backgrounds in the NEXT double beta decay experiment

The measurement of the internal 222Rn activity in the NEXT-White detector during the so-called Run-II period with 136Xe-depleted xenon is discussed in detail, together with its implications for double beta decay searches in NEXT. The activity is measured through the alpha production rate induced in the fiducial volume by 222Rn and its alpha-emitting progeny. The specific activity is measured to be (38.1 ± 2.2 (stat.) ± 5.9 (syst.)) mBq/m3. Radon-induced electrons have also been characterized from the decay of the 214Bi daughter ions plating out on the cathode of the time projection chamber. From our studies, we conclude that radon-induced backgrounds are sufficiently low to enable a successful NEXT-100 physics program, as the projected rate contribution should not exceed 0.1 counts/yr in the neutrinoless double beta decay sample

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.

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)

Radiopurity assessment of the energy readout for the NEXT double beta decay experiment

[EN] The "Neutrino Experiment with a Xenon Time-Projection Chamber" (NEXT) experiment intends to investigate the neutrinoless double beta decay of 136Xe, and therefore requires a severe suppression of potential backgrounds. An extensive material screening and selection process was undertaken to quantify the radioactivity of the materials used in the experiment. Separate energy and tracking readout planes using different sensors allow us to combine the measurement of the topological signature of the event for background discrimination with the energy resolution optimization. The design of radiopure readout planes, in direct contact with the gas detector medium, was especially challenging since the required components typically have activities too large for experiments demanding ultra-low background conditions. After studying the tracking plane, here the radiopurity control of the energy plane is presented, mainly based on gamma-ray spectroscopy using ultra-low background germanium detectors at the Laboratorio Subterráneo de Canfranc (Spain). All the available units of the selected model of photomultiplier have been screened together with most of the components for the bases, enclosures and windows. According to these results for the activity of the relevant radioisotopes, the selected components of the energy plane would give a contribution to the overall background level in the region of interest of at most 2.4 × 10¿4 counts per keV, kg and year, satisfying the sensitivity requirements of the NEXT experiment.Special thanks are due to LSC directorate and staff for their strong support for performing the measurements at the LSC Radiopurity Service. We are really grateful to Grzegorz Zuzel for the radon emanation measurements. The NEXT Collaboration acknowledges support from the following agencies and institutions: the European Research Council (ERC) under the Advanced Grant 339787-NEXT; the Ministerio de Economia y Competitividad of Spain under grants FIS2014-53371-C04 and the Severo Ochoa Program SEV-2014-0398; the GVA of Spain under grant PROMETEO/2016/120; the Portuguese FCT and FEDER through the program COMPETE, project PTDC/FIS/103860/2008; the U.S. Department of Energy under contracts number DE-AC02-07CH11359 (Fermi National Accelerator Laboratory) and DE-FG02-13ER42020 (Texas A & and the University of Texas at Arlington.Cebrian, S.; Perez, J.; Bandac, I.; Labarga, L.; Álvarez-Puerta, V.; Azevedo, CDR.; Benlloch-Rodriguez, JM.... (2017). Radiopurity assessment of the energy readout for the NEXT double beta decay experiment. Journal of Instrumentation. 12. https://doi.org/10.1088/1748-0221/12/08/T08003S12Avignone, F. T., Elliott, S. R., & Engel, J. (2008). Double beta decay, Majorana neutrinos, and neutrino mass. Reviews of Modern Physics, 80(2), 481-516. doi:10.1103/revmodphys.80.481Martín-Albo, J., Muñoz Vidal, J., Ferrario, P., Nebot-Guinot, M., Gómez-Cadenas, J. J., … Cárcel, S. (2016). Sensitivity of NEXT-100 to neutrinoless double beta decay. Journal of High Energy Physics, 2016(5). doi:10.1007/jhep05(2016)159Renner, J., Farbin, A., Vidal, J. M., Benlloch-Rodríguez, J. M., Botas, A., Ferrario, P., … Borges, F. I. G. (2017). Background rejection in NEXT using deep neural networks. Journal of Instrumentation, 12(01), T01004-T01004. doi:10.1088/1748-0221/12/01/t01004Dafni, T., Álvarez, V., Bandac, I., Bettini, A., Borges, F. I. G. M., Camargo, M., … Conde, C. A. N. (2016). Results of the material screening program of the NEXT experiment. Nuclear and Particle Physics Proceedings, 273-275, 2666-2668. doi:10.1016/j.nuclphysbps.2015.10.024Cebrián, S., Pérez, J., Bandac, I., Labarga, L., Álvarez, V., Barrado, A. I., … Cárcel, S. (2015). Radiopurity assessment of the tracking readout for the NEXT double beta decay experiment. Journal of Instrumentation, 10(05), P05006-P05006. doi:10.1088/1748-0221/10/05/p05006Wang, X., Chen, X., Fu, C., Ji, X., Liu, X., Mao, Y., … Zhang, T. (2016). Material screening with HPGe counting station for PandaX experiment. Journal of Instrumentation, 11(12), T12002-T12002. doi:10.1088/1748-0221/11/12/t12002Barrow, P., Baudis, L., Cichon, D., Danisch, M., Franco, D., Kaether, F., … Wulf, J. (2017). Qualification tests of the R11410-21 photomultiplier tubes for the XENON1T detector. Journal of Instrumentation, 12(01), P01024-P01024. doi:10.1088/1748-0221/12/01/p01024Busto, J., Gonin, Y., Hubert, F., Hubert, P., & Vuilleumier, J.-M. (2002). Radioactivity measurements of a large number of adhesives. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 492(1-2), 35-42. doi:10.1016/s0168-9002(02)01280-9Nisi, S., Di Vacri, A., Di Vacri, M. L., Stramenga, A., & Laubenstein, M. (2009). Comparison of inductively coupled mass spectrometry and ultra low-level gamma-ray spectroscopy for ultra low background material selection. Applied Radiation and Isotopes, 67(5), 828-832. doi:10.1016/j.apradiso.2009.01.02

Electron drift properties in high pressure gaseous xenon

[EN] Gaseous time projection chambers (TPC) are a very attractive detector technology for particle tracking. Characterization of both drift velocity and di¿usion is of great importance to correctly assess their tracking capabilities. NEXT-White is a High Pressure Xenon gas TPC with electroluminescent ampli¿cation, a 1:2 scale model of the future NEXT-100detector, which will be dedicated to neutrinoless double beta decay searches. NEXT-White has been operating at Canfranc Underground Laboratory (LSC) since December2016. The drift parameters have been measured using 83mKr for a range of reduced drift ¿elds at two di¿erent pressure regimes, namely 7.2 bar and 9.1 bar. Theresults have been compared with Magboltz simulations. Agreement at the 5% level or better has been found for drift velocity, longitudinal di¿usion and transverse di¿usion.The NEXT Collaboration acknowledges support from the following agencies and institutions: the European Research Council (ERC) under the Advanced Grant 339787-NEXT; 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 of Spain under grants FIS2014-53371-C04, 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 and FEDER through the program COMPETE, projects PTDC/FIS-NUC/2525/2014 and UID/FIS/04559/2013; the U.S. Department of Energy under contracts number DE-AC02-07CH11359 (Fermi National Accelerator Laboratory), DE-FG02-13ER42020 (Texas A&M) and de-sc0017721 (University of Texas at Arlington); and the University of Texas at Arlington. We also warmly acknowledge the Laboratorio Nazionale di 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.Simon, A.; Felkai, R.; Martinez-Lema, G.; Monrabal, F.; Gonzalez-Diaz, D.; Sorel, M.; Hernando Morata, JA.... (2018). Electron drift properties in high pressure gaseous xenon. Journal of Instrumentation. 13. https://doi.org/10.1088/1748-0221/13/07/P07013S13Nygren, D. (2009). High-pressure xenon gas electroluminescent TPC for 0-ν ββ-decay search. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 603(3), 337-348. doi:10.1016/j.nima.2009.01.222Gómez Cadenas, J. J., Álvarez, V., Borges, F. I. G., Cárcel, S., Castel, J., Cebrián, S., … Dias, T. H. V. T. (2014). Present Status and Future Perspectives of the NEXT Experiment. Advances in High Energy Physics, 2014, 1-22. doi:10.1155/2014/907067Martín-Albo, J., Muñoz Vidal, J., Ferrario, P., Nebot-Guinot, M., Gómez-Cadenas, J. J., … Cárcel, S. (2016). Sensitivity of NEXT-100 to neutrinoless double beta decay. Journal of High Energy Physics, 2016(5). doi:10.1007/jhep05(2016)159Álvarez, V., Borges, F. I. G., Cárcel, S., Castel, J., Cebrián, S., Cervera, A., … Díaz, J. (2013). Initial results of NEXT-DEMO, a large-scale prototype of the NEXT-100 experiment. Journal of Instrumentation, 8(04), P04002-P04002. doi:10.1088/1748-0221/8/04/p04002Álvarez, V., Borges, F. I. G., Cárcel, S., Castel, J., Cebrián, S., Cervera, A., … Díaz, J. (2013). Operation and first results of the NEXT-DEMO prototype using a silicon photomultiplier tracking array. Journal of Instrumentation, 8(09), P09011-P09011. doi:10.1088/1748-0221/8/09/p09011Álvarez, V., Borges, F. I. G. M., Cárcel, S., Castel, J., Cebrián, S., Cervera, A., … Díaz, J. (2013). Near-intrinsic energy resolution for 30–662keV gamma rays in a high pressure xenon electroluminescent TPC. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 708, 101-114. doi:10.1016/j.nima.2012.12.123Ferrario, P., Laing, A., López-March, N., Gómez-Cadenas, J. J., Álvarez, V., … Cebrián, S. (2016). First proof of topological signature in the high pressure xenon gas TPC with electroluminescence amplification for the NEXT experiment. Journal of High Energy Physics, 2016(1). doi:10.1007/jhep01(2016)104Pack, J. L., Voshall, R. E., & Phelps, A. V. (1962). Drift Velocities of Slow Electrons in Krypton, Xenon, Deuterium, Carbon Monoxide, Carbon Dioxide, Water Vapor, Nitrous Oxide, and Ammonia. Physical Review, 127(6), 2084-2089. doi:10.1103/physrev.127.2084Pack, J. L., Voshall, R. E., Phelps, A. V., & Kline, L. E. (1992). Longitudinal electron diffusion coefficients in gases: Noble gases. Journal of Applied Physics, 71(11), 5363-5371. doi:10.1063/1.350555Bowe, J. C. (1960). Drift Velocity of Electrons in Nitrogen, Helium, Neon, Argon, Krypton, and Xenon. Physical Review, 117(6), 1411-1415. doi:10.1103/physrev.117.1411Patrick, E. L., Andrews, M. L., & Garscadden, A. (1991). Electron drift velocities in xenon and xenon‐nitrogen gas mixtures. Applied Physics Letters, 59(25), 3239-3240. doi:10.1063/1.105744English, W. N., & Hanna, G. C. (1953). GRID IONIZATION CHAMBER MEASUREMENTS OF ELECTRON DRIFT VELOCITIES IN GAS MIXTURES. Canadian Journal of Physics, 31(5), 768-797. doi:10.1139/p53-070Hunter, S. R., Carter, J. G., & Christophorou, L. G. (1988). Low-energy electron drift and scattering in krypton and xenon. Physical Review A, 38(11), 5539-5551. doi:10.1103/physreva.38.5539Kobayashi, S., Hasebe, N., Hosojima, T., Ishizaki, T., Iwamatsu, K., Mimura, M., … Ishizuka, A. (2006). Ratio of Transverse Diffusion Coefficient to Mobility of Electrons in High-Pressure Xenon and Xenon Doped with Hydrogen. Japanese Journal of Applied Physics, 45(10A), 7894-7900. doi:10.1143/jjap.45.7894Álvarez, V., Borges, F. I. G., Cárcel, S., Cebrián, S., Cervera, A., Conde, C. A. N., … Esteve, R. (2013). Ionization and scintillation response of high-pressure xenon gas to alpha particles. Journal of Instrumentation, 8(05), P05025-P05025. doi:10.1088/1748-0221/8/05/p05025Lorca, D., Martín-Albo, J., Laing, A., Ferrario, P., Gómez-Cadenas, J. J., Álvarez, V., … Cebrián, S. (2014). Characterisation of NEXT-DEMO using xenon KαX-rays. Journal of Instrumentation, 9(10), P10007-P10007. doi:10.1088/1748-0221/9/10/p10007Kusano, H., Lopes, J. A. M., Miyajima, M., & Hasebe, N. (2013). Longitudinal and transverse diffusion of electrons in high-pressure xenon. Journal of Instrumentation, 8(01), C01028-C01028. doi:10.1088/1748-0221/8/01/c01028Henriques, C. A. O., Freitas, E. D. C., Azevedo, C. D. R., González-Díaz, D., Mano, R. D. P., Jorge, M. R., … Álvarez, V. (2017). Secondary scintillation yield of xenon with sub-percent levels of CO2 additive for rare-event detection. Physics Letters B, 773, 663-671. doi:10.1016/j.physletb.2017.09.017Obert, E. F. (1948). Compressibility Chart and the Ideal Reduced Volume. Industrial & Engineering Chemistry, 40(11), 2185-2186. doi:10.1021/ie50467a036Agostinelli, S., Allison, J., Amako, K., Apostolakis, J., Araujo, H., Arce, P., … Barrand, G. (2003). Geant4—a simulation toolkit. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 506(3), 250-303. doi:10.1016/s0168-9002(03)01368-8González-Díaz, D., Monrabal, F., & Murphy, S. (2018). Gaseous and dual-phase time projection chambers for imaging rare processes. 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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