A
bstract
The
Neutrino Experiment with a Xenon TPC
(NEXT) searches for the neutrinoless double-beta (0
νββ
) decay of
136
Xe using high-pressure xenon gas TPCs with electroluminescent amplification. ...A scaled-up version of this technology with about 1 tonne of enriched xenon could reach in less than 5 years of operation a sensitivity to the half-life of 0
νββ
decay better than 10
27
years, improving the current limits by at least one order of magnitude. This prediction is based on a well-understood background model dominated by radiogenic sources. The detector concept presented here represents a first step on a compelling path towards sensitivity to the parameter space defined by the inverted ordering of neutrino masses, and beyond.
A
bstract
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
νEC EC
) has been predicted for a number of isotopes, but only observed in
78
Kr,
130
Ba and, recently,
124
Xe. 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
νEC EC
. Here we report on the current sensitivity of the NEXT-White detector to
124
Xe 2
νEC EC
and on the extrapolation to NEXT-100. Using simulated data for the 2
νEC EC
signal and real data from NEXT-White operated with
124
Xe-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
124
Xe and for a 5-year run, a sensitivity to the 2
νEC EC
half-life of 6
×
10
22
y (at 90% confidence level) or better can be reached.
We present evidence of non-excimer-based secondary scintillation in gaseous xenon, obtained using both the NEXT-White time projection chamber (TPC) and a dedicated setup. Detailed comparison with ...first-principle calculations allows us to assign this scintillation mechanism to neutral bremsstrahlung (NBrS), a process that is postulated to exist in xenon that has been largely overlooked. For photon emission below 1000 nm, the NBrS yield increases from about10−2photon/e−cm−1bar−1at pressure-reduced electric field values of50Vcm−1bar−1to above3×10−1photon/e−cm−1bar−1at500Vcm−1bar−1. Above1.5kVcm−1bar−1, values that are typically employed for electroluminescence, it is estimated that NBrS is present with an intensity around1photon/e−cm−1bar−1, which is about 2 orders of magnitude lower than conventional, excimer-based electroluminescence. Despite being fainter than its excimeric counterpart, our calculations reveal that NBrS causes luminous backgrounds that can interfere, in either gas or liquid phase, with the ability to distinguish and/or to precisely measure low primary-scintillation signals (S1). In particular, we show this to be the case in the “buffer” region, where keeping the electric field below the electroluminescence threshold does not suffice to extinguish secondary scintillation. The electric field leakage in this region should be mitigated to avoid intolerable levels of NBrS emission. Furthermore, we show that this new source of light emission opens up a viable path toward obtaining S2 signals for discrimination purposes in future single-phase liquid TPCs for neutrino and dark matter physics, with estimated yields up to20–50photons/e−cm−1.
The two-photon exchange experiment at DESY Alarcon, R.; Beck, R.; Bernauer, J. C. ...
The European physical journal. A, Hadrons and nuclei,
04/2024, Letnik:
60, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We propose a new measurement of the ratio of positron-proton to electron-proton elastic scattering at DESY. The purpose is to determine the contributions beyond single-photon exchange, which are ...essential for the Quantum Electrodynamic (QED) description of the most fundamental process in hadronic physics. By utilizing a 20 cm long liquid hydrogen target in conjunction with the extracted beam from the DESY synchrotron, we can achieve an average luminosity of
2.12
×
10
35
cm
-
2
·
s
-
1
(
≈
200
times the luminosity achieved by OLYMPUS). The proposed two-photon exchange experiment (TPEX) entails a commissioning run at a beam energy of 2 GeV, followed by measurements at 3 GeV, thereby providing new data up to
Q
2
=
4.6
(GeV/
c
)
2
(twice the range of current measurements). We present and discuss the proposed experimental setup, run plan, and expectations.
The Neutrino Experiment with a Xenon TPC (NEXT) searches for the neutrinoless double-beta (0νββ) decay of 136Xe using high-pressure xenon gas TPCs with electroluminescent amplification. A scaled-up ...version of this technology with about 1 tonne of enriched xenon could reach in less than 5 years of operation a sensitivity to the half-life of 0νββ decay better than 1027 years, improving the current limits by at least one order of magnitude. This prediction is based on a well-understood background model dominated by radiogenic sources. The detector concept presented here represents a first step on a compelling path towards sensitivity to the parameter space defined by the inverted ordering of neutrino masses, and beyond.
Radio-frequency (RF) carpets with ultra-fine pitches are examined for ion transport in gases at atmospheric pressures and above. We develop new analytic and computational methods for modeling RF ion ...transport at densities where dynamics are strongly influenced by buffer gas collisions. An analytic description of levitating and sweeping forces from phased arrays is obtained, then thermodynamic and kinetic principles are used to calculate ion loss rates in the presence of collisions. This methodology is validated against detailed microscopic SIMION simulations. We then explore a parameter space of special interest for neutrinoless double beta decay experiments: transport of barium ions in xenon at pressures from 1 to 10 bar. Our computations account for molecular ion formation and pressure dependent mobility as well as finite temperature effects. We discuss the challenges associated with achieving suitable operating conditions, which lie beyond the capabilities of existing devices, using presently available or near-future manufacturing techniques.
Alzheimer's disease (AD) is a progressive neurodegenerative disorder for which numerous mouse models have been generated. In both AD patients and mouse models, there is increasing evidence that ...neuronal dysfunction occurs before the accumulation of β-amyloid (Aβ)-containing plaques and neurodegeneration. Characterization of the timing and nature of preplaque dysfunction is important for understanding the progression of this disease and to identify pathways and molecular targets for therapeutic intervention. Hence, we have examined the progression of dysfunction at the morphological, functional, and behavioral levels in the Tg2576 mouse model of AD. Our data show that decreased dendritic spine density, impaired long-term potentiation (LTP), and behavioral deficits occurred months before plaque deposition, which was first detectable at 18 months of age. We detected a decrease in spine density in the outer molecular layer of the dentate gyrus (DG) beginning as early as 4 months of age. Furthermore, by 5 months, there was a decline in LTP in the DG after perforant path stimulation and impairment in contextual fear conditioning. Moreover, an increase in the Aβ42/Aβ40 ratio was first observed at these early ages. However, total amyloid levels did not significantly increase until ≈18 months of age, at which time significant increases in reactive astrocytes and microglia could be observed. Overall, these data show that the perforant path input from the entorhinal cortex to the DG is compromised both structurally and functionally, and this pathology is manifested in memory defects long before significant plaque deposition.
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