Searches for Double Beta Decay of $^{134}$Xe with EXO-200
200 Collaboration, J. B. Albert, G. Anton, I. Badhrees, P. S. Barbeau, R. Bayerlein, D. Beck, V. Belov, M. Breidenbach, T. Brunner, G. F. Cao, W. R. Cen, C. Cha… 展开作者
200 Collaboration, J. B. Albert, G. Anton, I. Badhrees, P. S. Barbeau, R. Bayerlein, D. Beck, V. Belov, M. Breidenbach, T. Brunner, G. F. Cao, W. R. Cen, C. Chambers, B. Cleveland, M. Coon, A. Craycraft, W. Cree, T. Daniels, M. Danilov, S. J. Daugherty, J. Daughhetee, J. Davis, S. Delaquis, A. Der Mesrobian-Kabakian, R. DeVoe, T. Didberidze, J. Dilling, A. Dolgolenko, M. J. Dolinski, W. Fairbank, J. Farine, S. Feyzbakhsh, P. Fierlinger, D. Fudenberg, R. Gornea, K. Graham, G. Gratta, C. Hall, J. Hoessl, P. Hufschmidt, M. Hughes, A. Jamil, M. J. Jewell, A. Johnson, S. Johnston, A. Karelin, L. J. Kaufman, T. Koffas, S. Kravitz, R. Krücken, A. Kuchenkov, K. S. Kumar, Y. Lan, D. S. Leonard, S. Li, C. Licciardi, Y. H. Lin, R. MacLellan, M. G. Marino, T. Michel, B. Mong, D. Moore, K. Murray, R. Nelson, O. Njoya, A. Odian, I. Ostrovskiy, A. Piepke, A. Pocar, F. Retière, P. C. Rowson, J. J. Russell, A. Schubert, D. Sinclair, E. Smith, V. Stekhanov, M. Tarka, T. Tolba, R. Tsang, P. Vogel, J. -L. Vuilleumier, M. Wagenpfeil, A. Waite, J. Walton, T. Walton, M. Weber, L. J. Wen, U. Wichoski, L. Yang, Y. -R. Yen, O. Ya. Zeldovich, J. Zettlemoyer, T. Ziegler
Searches for double beta decay of $^{134}$Xe were performed with EXO-200, a single-phase liquid xenon detector designed to search for neutrinoless double beta decay of $^{136}$Xe. Using an exposure of $29.6\text{ kg}\!\cdot\!\text{yr}$, the lower limits of $\text{T}_{1/2}^{2νβ\!β}>8.7\cdot10^{20}\text{ yr}$ and $\text{T}_{1/2}^{0νβ\!β}>1.1\cdot10^{23}\text{ yr}$ at 90% confidence level were derived, with corresponding half-life sensitivities of $1.2\cdot10^{21}\text{ yr}$ and $1.9\cdot10^{23}\text{ yr}$. These limits exceed those in the literature for $^{134}$Xe, improving by factors of nearly $10^{5}$ and 2 for the two antineutrino and neutrinoless modes, respectively.
Neutrinoless double beta decay is a lepton number violating process whose observation would also establish that neutrinos are their own anti-particles. There are many experimental efforts with a variety of techniques. Some (EXO, Kamland-Zen, GERDA phase I and CANDLES) started take data in 2011 and EXO has reported the first measurement of the half life for the double beta decay with two neutrinos of $^{136}$Xe. The sensitivities of the different proposals are reviewed.
A collection of stories is presented on discoveries of double beta decay (including neutrinoless one) which were refuted in the subsequent investigations.
Xenon time projection chambers (TPCs) have become a well-established detection technology for neutrinoless double beta decay searches in $^{136}$Xe. I discuss the motivations for this choice. I describe the status and prospects of both liquid and gaseous xenon TPC projects for double beta decay.
The simultaneous beta decay of two neutrons in a nucleus without the emission of neutrinos (called neutrinoless double beta decay) is a lepton number violating process which is not allowed in the Standard Model of particle physics. More than a dozen experiments using different candidate isotopes and a variety of detection techniques are searching for this decay. Some (EXO-200, Kamland-Zen, GERDA) started to take data recently. EXO and Kamland-Zen have reported first limits of the half life $T_{1/2}^{0ν}$ for $^{136}$Xe. After a decade of little progress in this field, many new results will soo…
Neutrinoless double decay is a unique probe for lepton number conservation and neutrino properties. It allows to investigate the Dirac/Majorana nature of the neutrinos and their absolute mass scale (hierarchy problem) with unprecedented sensitivity. A number of experiments are presently under preparation to cover the quasi-degenerate region of the neutrino mass spectrum. Improved sensitivities are however required to sound the so-called inverted hierarchy region. This is a real challenge faced by a number of new proposed projects, based either on large expansions of the present experiments or …
Liquid Xe TPCs are among the most popular choices for double beta decay and WIMP dark matter searches. Gaseous Xe has intrinsic advantages when compared to Liquid Xe, specifically, tracking capability and better energy resolution for double beta decay searches. The performance of gaseous Xe can be further improved by molecular additives such as trimethylamine(TMA), which are expected to (1) cool down the ionization electrons, (2) convert Xe excitation energy to TMA ionizations through Penning transfer, and (3) produce scintillation and electroluminescence light in a more easily detectable wave…
The sensitivity for double beta decay studies of Xe-134 and Xe-124 is investigated assuming a potential large scale Xe experiment developed for dark matter searches depleted in Xe-136. The opportunity for an observation of the 2nu double beta decay of Xe-134 is explored for various scenarios. A positive observation should be possible for all calculated nuclear matrix elements. The detection of 2$ν$ ECEC of Xe-124 can be probed in all scenarios covering the theoretical predicted half-life uncertainties and a potential search for Xe-126 is discussed. The sensitivity to beta+/EC decay of Xe-124 i…
This article reviews the application of high pressure gas xenon (HPXe) time projection chambers to neutrinoless double beta decay experiments. First, the fundamentals of the technology and the historical development of the field are discussed. Then, the state of the art is presented, including the prospects for the next generation of experiments with masses in the ton scale.
Bolometers are low temperature particle detectors with high energy resolution and detection efficiency. Some types of bolometric detectors are also able to perform an efficient particle identification. A wide variety of radiopure dielectric and diamagnetic materials makes the bolometric technique favorable for applications in astroparticle physics. In particular, thanks to their superior performance, bolometers play an important role in the world-wide efforts on searches for neutrinoless double-beta decay. Such experiments strongly require an extremely low level of the backgrounds that can eas…
We introduce a novel particle detection concept for large-volume, fine granularity particle detection: The Ion Fluorescence Chamber (IFC). In electronegative gases such as SF$_6$ and SeF$_6$, ionizing particles create ensembles of positive and negative ions. In the IFC, positive ions are drifted to a chemically active cathode where they react with a custom organic turn-on fluorescent monolayer encoding a long-lived 2D image. The negative ions are sensed electrically with course resolution at the anode, inducing an optical microscope to travel to and scan the corresponding cathode location for …
A new approach (called COBRA) for investigating double beta decay using CdTe (CdZnTe) semiconductor detectors is proposed. It follows the idea that source and detector are identical. This will allow simultaneous measurements of 5 $β^-β^-$ - and 4 $β^+β^+$ - emitters at once. Half-life limits for neutrinoless double beta decay of Cd-116 and Te-130 can be improved by more than one order of magnitude with respect to current limits and sensitivities on the effective Majorana neutrino mass of less than 1 eV can be obtained. Furthermore, for the first time a realistic chance of observing double elec…
Searches for rare and exotic Higgs decays using proton-proton collision data with the center-of-mass energy of 8 TeV and 13 TeV collected with the ATLAS detector are presented. Various final states are considered. No significant deviations from the Standard Model expectations are found. The results are interpreted in different Beyond Standard Model theories.
Tremendous efforts are required to scale the summit of observing neutrinoless double beta decay ($0 νββ$). This article quantitatively explores the interplay between exposure (target mass X data taking time) and background levels in $0 νββ$ experiments. In particular, background reduction can substantially alleviate the necessity of unrealistic large exposure as the normal mass hierarchy (NH) is probed. The non-degenerate (ND)-NH can be covered with an exposure of O(100) ton-year, which is only an order of magnitude larger than those planned for next generation projects - provided that the bac…
We report on a search for neutrinoless double-beta decay of $^{136}$Xe with EXO-200. No signal is observed for an exposure of 32.5 kg-yr, with a background of ~1.5 x 10^{-3} /(kg yr keV) in the $\pm 1σ$ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay $T_{1/2}^{0νββ}$($^{136}$Xe) > 1.6 x 10$^{25}$ yr (90% CL), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation.
The gaseous Xenon(Xe) time projection chamber (TPC) is an attractive detector technique for neutrinoless double beta decay and WIMP dark matter searches. While it is less dense compared to Liquid Xe detectors, it has intrinsic advantages in tracking capability and better energy resolution. The performance of gaseous Xe can be further improved by molecular additives such as trimethylamine(TMA), which is expected to (1) cool down the ionization electrons, (2) convert Xe excitation energy to TMA ionizations through Penning transfer, and (3) produce scintillation and electroluminescence light in a…
Searches for exotic decays of the 125 GeV Higgs boson performed with data collected by the CMS experiment are presented. Three classes of searches are detailed: searches for invisible decays of the Higgs boson, searches for lepton flavor violating Higgs decays, and searches for decays to the Higgs boson to light pseudoscalars decaying to SM particle pairs. These analyses are based on data collected at center-of-mass energies of 8 and 13 TeV.
The Standard Model of Particle Physics predicts the double-$β$ decay of certain nuclei with the emission of two active neutrinos. In this letter, we argue that double-$β$ decay experiments could be used to probe models with light exotic fermions through the search for spectral distortions in the electron spectrum with respect to the Standard Model expectations. We consider two concrete examples: models with light sterile neutrinos, singly produced in the double-$β$ decay, and models with a light $Z_2$-odd fermion, pair produced due to a $Z_2$ symmetry. We estimate the discovery potential of a …
Large detectors employing xenon are a leading technology in existing and planned searches for new physics, including searches for neutrinoless double beta decay ($0νββ$) and dark matter. While upcoming detectors will employ target masses of a ton or more, further extending gas or liquid phase Xe detectors to the kton scale would enable extremely sensitive next-generation searches for rare phenomena. The key challenge to extending this technology to detectors well beyond the ton scale is the acquisition of the Xe itself. We describe the motivation for extending Xe time projection chambers (TPCs…
NEXT (Neutrino Experiment with a Xenon TPC) is an experimental program whose goals are to discover neutrinoless double beta decay using $^{136}$Xe in high pressure xenon TPCs with electroluminescent readout. In this paper, results from the NEXT-White detector, which is currently taking data at Laboratorio Subterráneo de Canfranc (LSC) will be reported. The prospects for the NEXT-100 apparatus, scheduled to start operations in 2020, as well as the plans to extend the technology to large and ultra-low background detectors needed to fully explore the inverse hierarchy of neutrino masses, will als…
We propose a novel detection concept for neutrinoless double-beta decay searches. This concept is based on a Time Projection Chamber (TPC) filled with high-pressure gaseous xenon, and with separated-function capabilities for calorimetry and tracking. Thanks to its excellent energy resolution, together with its powerful background rejection provided by the distinct double-beta decay topological signature, the design discussed in this Letter Of Intent promises to be competitive and possibly out-perform existing proposals for next-generation neutrinoless double-beta decay experiments. We discuss …
Particle tracks and differential energy loss measured in high pressure gaseous detectors can be exploited for event identification in neutrinoless double beta decay~($0νββ$) searches. We develop a new method based on Kalman Filter in a Bayesian formalism (KFB) to reconstruct meandering tracks of MeV-scale electrons. With simulation data, we compare the signal and background discrimination power of the KFB method assuming different detector granularities and energy resolutions. Typical background from $^{232}$Th and $^{238}$U decay chains can be suppressed by another order of magnitude than tha…
In this paper we present two searches for new physics in Upsilon(3S) decays collected by the BABAR detector. We search for charged lepton-flavour violating decays of the Upsilon(3S), which are unobservable in the Standard Model but are predicted to occur in several beyond-the-Standard Model scenarios. We also search for production of a light Higgs or Higgs-like state produced in radiative decays of the Upsilon(3S) and decaying to muon pairs.
The excellent particle identification capabilities of the ALICE detector, using the time projection chamber and the time-of-flight detector, allow the detection of light nuclei and anti-nuclei. Furthermore, the high tracking resolution provided by the inner tracking system enables the separation of primary nuclei from those coming from the decay of heavier systems. This allows for the reconstruction of decays such as the hypertriton mesonic weak decay ($^3_Λ$H$\rightarrow ^3$He + $π^-$), the decay of a hypothetical bound state of a $Λ$n into a deuteron and pion or the H-dibaryon decaying into …
I present three recent results from searches for exotic physics at the BaBar/PEP-II B-factory. These results span many of the samples produced at the B-factory, including B mesons, tau leptons, and Upsilon(3S) mesons. We have searched for CPT-violation in B mixing and find no significant deviation from the no-violation hypothesis. We have also searched for lepton-flavor-violating decays of the tau using tau- -> omega l- and tau- -> l+ l- l+ and their charge conjugates. We find no evidence for these processes and set upper limits on their branching fractions. Finally, we have searched for a low…
Neutrinoless double beta decay is a hypothetical, very slow nuclear transition in which two neutrons undergo beta decay simultaneously and without the emission of neutrinos. The importance of this process goes beyond its intrinsic interest: an unambiguous observation would establish a Majorana nature for the neutrino and prove the violation of lepton number. NEXT is a new experiment to search for neutrinoless double beta decay using a radiopure high-pressure xenon gas TPC, filled with 100 kg of Xe enriched in Xe-136. NEXT will be the first large high-pressure gas TPC to use electroluminescence…
We report on the latest direct searches for light exotics at LHCb, conducted during Run I of LHC. This proceedings are divided into two sections, the first part will cover the search for the lepton number violating decay ${B}\rightarrow {π^{+}μ^{-}μ^{-}}$ while the second part will cover the search for a low mass dark boson in the decay $B^0 \rightarrow K^{*0}χ$, with $χ\rightarrow μ^+μ^-$ and $K^{*0} \rightarrow K^+π^-$. The data used in these searches correspond to integrated luminosities of 1.0 and $2.0$ fb$^{-1}$ collected in $pp$ collisions at centre of mass energies of $\sqrt{s}=7$ and 8…
A review of the experimental status of purely leptonic ${B^0_{[s]}\to\ell^+\ell^-}$ decays is given and the new analysis of ${B^0_{[s]}\toμ^+μ^-}$ observables with the LHCb experiment is presented. The new results are the most precise single experiment measurements of the quantities to date and are consistent with the Standard Model. However, they also match the recent anomalies found in $b\to s\ell\ell$ transitions excellently.
The Neutrino Experiment with a Xenon TPC (NEXT) seeks to discover the neutrinoless double beta ($ββ0ν$) decay of $^{136}$Xe using a high-pressure xenon gas time projection chamber with electroluminescent amplification. The observation of $ββ0ν$ decay would prove that neutrinos are Majorana particles and that lepton number is not conserved. The NEXT detector concept offers several features of great value for $ββ0ν$-decay searches, including excellent energy resolution, tracking for the active suppression of backgrounds and scalability to large source masses. The initial phase of the NEXT projec…
Low-energy experiments studying single beta decay can serve as sensitive probes of Lorentz invariance that can complement interferometric searches for deviations from this spacetime symmetry. Experimental signatures of a dimension-three operator for Lorentz violation that are unobservable in neutrino oscillations are described for the decay the polarized and unpolarized neutrons as well as for measurements of the spectral endpoint in beta decay.
In the Standard Model (SM), the weak gauge bosons and fermions acquire mass through the Higgs mechanism. A lower limit on the SM Higgs mass of 114.4 GeV was obtained from the direct search at LEP. Although a single Higgs doublet is sufficient to explain the non-zero particle masses while keeping the theory SU(2) gauge invariant, several extensions to this minimal model were proposed, to which this limit does not apply. Most of the models discussed here introduce one additional Higgs doublet and are therefore called Two Higgs doublet models (2HDM). Several signatures predicted by such models ha…
Several recent searches for exotic and rare decays of the Standard Model Higgs boson with the ATLAS and CMS detectors are presented. The searches are performed on $\sqrt{s}$=13 TeV proton-proton collisions data collected at the LHC between 2015 and 2018. The topics covered include searches for the Higgs boson decays into two pseudoscalars, $H\rightarrow aa$, in three different final states, $2b2μ$, $4b$ and $2\mu2τ$, search for lepton-flavour violating Higgs decays, $H\rightarrow μτ/ eτ$, and search for a rare $H\rightarrow \ell\ell γ$ decay. ATLAS presents evidence for the $H\rightarrow \ell\…
DAMA is an observatory for rare processes and it is operative deep underground at the Gran Sasso National Laboratory of the I.N.F.N. (LNGS). Here some arguments will be presented on the investigation on dark matter particles by annual modulation signature and on some of the realized double beta decay searches.
We have searched for the pair production of first generation scalar leptoquarks using the full data set (123 pb**-1) collected with the D0 detector at the Fermilab Tevatron during 1992-1996. We observe no candidates, consistent with the expected background. We combine these new results from the ee + jets and enu + jets channels with the published nunu + jets result to obtain a 95% CL upper limits on the LQ pair production cross section as a function of mass and beta, the branching ratio to a charged lepton and a quark. Comparing to the NLO theory predictions, we set 95% CL lower limits on the …
Double beta $ββ$ decay experiments are one of the most active research topics in Neutrino Physics. The measurement of the neutrinoless mode $0νββ$ could give unique information on the neutrino mass scale and nature. The current generation of experiments aims at detector target masses at the 100 kg scale, while the next generation will need to go to the ton scale in order to completely explore the inverse hierarchy models of neutrino mass. Very good energy resolutions and ultra-low background levels are the two main experimental requirements for a successful experiment. The topological informat…
Searches for final states expected in models with light gravitinos have been performed, including experimental topologies with multi-leptons with missing energy, leptons and photons with missing energy, and jets and photons with missing energy. No excess over the expectations from the Standard Model has been observed. Limits are placed on production cross-sections in the different experimental topologies. Additionally, combining with searches for the anomalous production of lepton and photon pairs with missing energy, results are interpreted in the context of minimal models of gauge mediated S…
The NEMO 3 experiment searches for neutrinoless double beta decay and makes precision measurements of two-neutrino double beta decay in seven isotopes. The latest two-neutrino half-life results are presented, together with the limits on neutrinoless half-lives and the corresponding effective Majorana neutrino masses. Also given are the limits obtained on neutrinoless double beta decay mediated by Rp-violating SUSY, right-hand currents and different Majoron emission modes.
We study in this letter the double beta decay of 136Xe with emission of two neutrinos which has been recently measured by the EXO-200 collaboration. We use the same shell model framework, valence space, and effective interaction that we have already employed in our calculation of the nuclear matrix element (NME) of its neutrinoless double beta decay. Using the quenching factor of the Gamow-Teller operator which is needed to reproduce the very recent high resolution 136Xe (3He, t)136Cs data, we obtain a nuclear matrix element M(2nu)=0.025 MeV^(-1) compared with the experimental value M(2nu)=0.0…
We propose leveraging our proficiency for detecting Higgs resonances by using the Higgs as a tagging object for new heavy physics. In particular, we argue that searches for exotic Higgs production from decays of color-singlet fields with electroweak charges could beat current searches at the LHC which look for their decays to vectors. As an example, we study the production and decay of vector-like leptons which admit Yukawa couplings with SM leptons. We find that bounds from Run 2 searches are consistent with anywhere from hundreds to many thousands of Higgses having been produced in their dec…
This paper reviews the current status and future outlook of neutrinoless double beta decay searches, which try to provide an answer to the fundamental question of whether neutrinos are Dirac or Majorana particles.
Limits on an exotic heavy quark $T$ are broadly generalized by considering the full range of $T\rightarrow Wb, th$ or $tZ$ branching ratios. We combine results of specific $T\rightarrow tZ$ and $T\rightarrow Wb$ searches with limits on various combinations of decay modes evaluated by re-interpreting other searches. We find strong bounds across the entire space of branching ratios, ranging from $m_T > 415$ GeV to $m_T > 557$ GeV at 95% confidence level.
EXO-200 is the first phase of the Enriched Xenon Observatory (EXO) experiment, which searches for neutrinoless double beta decay in 136Xe to measure the mass and probe the Majorana nature of the neutrino. EXO-200 consists of 200 kg of liquid Xe enriched to 80% in 136Xe in an ultra-low background TPC. Energy resolution is enhanced through the simultaneous collection of scintillation light using Large Area Avalanche Photodiodes (LAAPD's) and ionization charge. It is being installed at the WIPP site in New Mexico, which provides a 2000 meter water-equivalent overburden. EXO-200 will begin taking …
We propose a new detector concept, GraXe (to be pronounced as grace), to search for neutrinoless double beta decay in Xe-136. GraXe combines a popular detection medium in rare-event searches, liquid xenon, with a new, background-free material, graphene. In our baseline design of GraXe, a sphere made of graphene-coated titanium mesh and filled with liquid xenon (LXe) enriched in the Xe-136 isotope is immersed in a large volume of natural LXe instrumented with photodetectors. Liquid xenon is an excellent scintillator, reasonably transparent to its own light. Graphene is transparent over a large …
The study of neutrinoless double beta decay is of outmost importance for neutrino physics. It is considered to be the gold plated channel to probe the fundamental character of neutrinos and to determine the neutrino mass. From the experimental point about nine different isotopes are explored for the search. After a general introduction follows a short discussion on nuclear matrix element calculations and supportive measurements. The current experimental status of double beta searches is presented followed by a short discussion of the ideas and proposals for large scale experiments.
The connection of neutrino physics with neutrinoless double beta decay is reviewed. After presenting the current status of the PMNS matrix and the theoretical background of neutrino mass and lepton mixing, we will summarize the various implications of neutrino physics for double beta decay. The influence of light sterile neutrinos and other exotic modifications of the three neutrino picture is also discussed.
Searches for new leptophobic resonances at high energy colliders usually target their decay modes into pairs of light quarks, top quarks, or standard model bosons. Additional decay modes may also be present, producing signatures to which current searches are not sensitive. We investigate the performance of generic searches that look for resonances decaying into two large-radius jets. As benchmark for our analysis we use a supersymmetric $\text{U}(1)'$ extension of the Standard Model, the so-called U$μν$SSM, where all the SM decay modes of the $Z'$ boson take place, plus additional (cascade) de…
The international project ``Microcalorimeter Arrays for a Rhenium Experiment'' (MARE) aims at the direct and calorimetric measurement of the electron neutrino mass with sub-electronvolt sensitivity. Calorimetric neutrino mass experiments measure all the energy released in a beta decay except for the energy carried away by the neutrino, therefore removing the most severe systematic uncertainties which have plagued the traditional and, so far, more sensitive spectrometers. Calorimetric measurements are best realized exploiting the thermal detection technique. This approach uses thermal microcalo…
Compelling experimental evidences of neutrino oscillations and their implication that neutrinos are massive particles have given neutrinoless double beta decay a central role in astroparticle physics. In fact, the discovery of this elusive decay would be a major breakthrough, unveiling that neutrino and antineutrino are the same particle and that the lepton number is not conserved. It would also impact our efforts to establish the absolute neutrino mass scale and, ultimately, understand elementary particle interaction unification. All current experimental programs to search for neutrinoless do…
We analyze the impact of a measurement, or of an improved bound, on theta_{13} for the determination of the effective neutrino mass in neutrino-less double beta decay and cosmology. In particular, we discuss how an improved limit on (or a specific value of) theta_{13} can influence the determination of the neutrino mass spectrum via neutrino-less double beta decay. We also discuss the interplay with improved cosmological neutrino mass searches.
The program HiggsBounds is a well-established tool for testing Beyond-the-Standard Model (BSM) theories with an extended Higgs sector against experimental limits from collider searches at LEP, Tevatron and LHC. Thus far, it could be applied to any neutral or charged Higgs bosons originating from the modified Higgs sector. Implicitly, these particles were assumed to exhibit a somewhat hierarchical Yukawa structure as present in the Standard Model, where in particular the couplings to first generation fermions could be neglected. In this work, we extend the HiggsBounds functionalities to go beyo…
