Scholarly Works, Center for Neutrino Physics

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  • Probing new physics at DUNE operating in a beam-dump mode
    Brdar, Vedran; Dutta, Bhaskar; Jang, Wooyoung; Kim, Doojin; Shoemaker, Ian M.; Tabrizi, Zahra; Thompson, Adrian; Yu, Jaehoon (American Physical Society, 2023-03)
    In this work we demonstrate that a future accelerator-based neutrino experiment such as DUNE can greatly increase its sensitivity to a variety of new physics scenarios by operating in a mode where the proton beam impinges on a beam dump. We consider two new physics scenarios, namely light dark matter and axionlike particles and show that by utilizing a dump mode at a DUNE-like experiment, unexplored new regions of parameter space can be probed with an exposure of only 3 months with half of its expected initial beam power. Specifically, targetless configuration of future high intensity neutrino experiments will probe the parameter space for thermal relic dark matter as well as the QCD axion. The strength of such a configuration in the context of new physics searches stems from the fact that the neutrino flux is significantly reduced compared to that of the target, resulting in much smaller backgrounds from neutrino interactions. We have verified this in detail by explicitly computing neutrino fluxes which we make publicly available in order to facilitate further studies with a targetless configuration.
  • Gravity-improved metastability bounds for the Type-I seesaw mechanism
    Chauhan, Garv; Steingasser, Thomas (2023-09-22)
    Right-handed neutrinos (RHN) destabilize the electroweak vacuum by increasing its decay rate. In the SM, the latter is dominated by physics at the RG scale at which λ reaches its minimum, 𝜇SM∗ ∼ 1017 GeV. For large neutrino Yukawa coupling Yν, RHNs can push μ* beyond the Planck scale, implying that gravitational effects need to be taken into account. In this work, we perform the first comprehensive study of electroweak vacuum metastability in the type-I seesaw mechanism including these effects. Our analysis covers both low- and high-scale seesaw models, with two as well as three RHNs and for multiple values of the Higgs’ non-minimal coupling to gravity. We find that gravitational effects can significantly stabilize the vacuum, leading to weaker metastability bounds. We show that metastability sets the strongest bounds for low-scale seesaws with MN > 1 TeV. For high-scale seesaws, we find upper bounds on the allowed masses for the RHNs, which are relevant for high-scale leptogenesis. We also point out that Tr(𝑌†𝜈Yν), which is commonly used to express these metastability bounds, cannot be used for all of parameter space. Instead, we argue that bounds can always be expressed reliably through Tr(𝑌†𝜈Yν𝑌†𝜈Yν). Lastly, we use this insight to develop a new technique for an easier RG analysis applicable to scenarios with degenerate RHN masses.
  • The Andromeda gamma-ray excess: background systematics of the millisecond pulsars and dark matter interpretations
    Zimmer, Fabian; Macias, Oscar; Ando, Shin'ichiro; Crocker, Roland M.; Horiuchi, Shunsaku (Oxford University Press, 2022-09)
    Since the discovery of an excess in gamma rays in the direction of M31, its cause has been unclear. Published interpretations focus on dark matter or stellar related origins. Studies of a similar excess in the Milky Way centre motivate a correlation of the spatial morphology of the signal with the distribution of stellar mass in M31. However, a robust determination of the best theory for the observed excess emission is challenging due to uncertainties in the astrophysical gamma-ray foreground model. We perform a spectro-morphological analysis of the M31 gamma-ray excess using state-of-the-art templates for the distribution of stellar mass in M31 and novel astrophysical foreground models for its sky region. We construct maps for the old stellar populations of M31 based on data from the PAndAS survey and carefully remove the foreground stars. We also produce improved astrophysical foreground models via novel image inpainting techniques based on machine learning methods. Our stellar maps, mimicking the location of a population of millisecond pulsars in the bulge of M31, reach a 5.4 sigma significance, making them as strongly favoured as the simple phenomenological models usually considered in the literature, e.g. disc-like templates. This detection is robust to generous variations of the astrophysical foreground model. Once the stellar templates are included in the astrophysical model, we show that the dark matter annihilation interpretation of the signal is unwarranted. We demonstrate that about one million unresolved millisecond pulsars naturally explain the observed gamma-ray luminosity per stellar mass, energy spectrum, and stellar bulge-to-disc flux ratio.
  • Neutrino portals, terrestrial upscattering, and atmospheric neutrinos
    Gustafson, R. Andrew; Plestid, Ryan; Shoemaker, Ian M. (American Physical Society, 2022-11)
    We consider the upscattering of atmospheric neutrinos in the interior of Earth producing heavy neutral leptons (HNLs) which subsequently decay inside large volume detectors (e.g., Super-Kamiokande or DUNE). We compute the flux of upscattered HNLs arriving at a detector and the resultant event rate of visible decay products. Using Super-Kamiokande's atmospheric neutrino dataset we find new leading constraints for dipole couplings to any flavor with HNL masses between roughly 10 and 100 MeV. For mass mixing with tau neutrinos, we probe new parameter space near HNL masses of similar to 20 MeV with prospects for substantial future improvements. We also discuss prospects at future experiments such as DUNE, JUNO, and Hyper-Kamiokande.
  • Light Curves and Event Rates of Axion Instability Supernovae
    Mori, Kanji; Moriya, Takashi J.; Takiwaki, Tomoya; Kotake, Kei; Horiuchi, Shunsaku; Blinnikov, Sergei I. (IOP Publishing, 2023-01)
    It was recently proposed that exotic particles can trigger a new stellar instability that is analogous to the e (-) e (+) pair instability if they are produced and reach equilibrium in the stellar plasma. In this study, we construct axion instability supernova (AISN) models caused by the new instability to predict their observational signatures. We focus on heavy axion-like particles (ALPs) with masses of similar to 400 keV-2 MeV and coupling with photons of g ( a gamma ) similar to 10(-5) GeV-1. It is found that the Ni-56 mass and the explosion energy are significantly increased by ALPs for a fixed stellar mass. As a result, the peak times of the light curves of AISNe occur earlier than those of standard pair-instability supernovae by 10-20 days when the ALP mass is equal to the electron mass. Also, the event rate of AISNe is 1.7-2.6 times higher than that of pair-instability supernovae, depending on the high mass cutoff of the initial mass function.
  • Symmetry in Neutrino Oscillation in Matter: New Picture and the νSM-Non-Unitarity Interplay
    Minakata, Hisakazu (MDPI, 2022-12-06)
    We update and summarize the present status of our understanding of the reparametrization symmetry with an i↔j state exchange in neutrino oscillation in matter. We introduce a systematic method called “Symmetry Finder” (SF) to uncover such symmetries, demonstrate its efficient hunting capability, and examine their characteristic features. Apparently they have a local nature: the 1–2 and 1–3 state exchange symmetries exist at around the solar and atmospheric resonances, respectively, with the level-crossing states exchanged. However, this view is not supported, to date, in the globally valid Denton et al. (DMP) perturbation theory, which possesses the 1–2, but not the 1–3, exchange symmetry. This is probably due to our lack of understanding, and we find a clue for a larger symmetry structure than we know of. In the latter part of this article, we introduce non-unitarity, or unitarity violation (UV), into the νSM neutrino paradigm, a low-energy description of beyond νSM new physics at a high (or low) scale. Based on the analyses of UV extended versions of the atmospheric resonance and the DMP perturbation theories, we argue that the reparametrization symmetry has a diagnostic capability for the theory with the νSM and UV sectors. Speculation is given on the topological nature of the identity, which determines the transformation property of the UV α parameters.
  • Neutrino oscillations at JUNO, the Born rule, and Sorkin's triple path interference
    Huber, Patrick; Minakata, Hisakazu; Minic, Djordje; Pestes, Rebekah; Takeuchi, Tatsu (American Physical Society, 2022-06-10)
    We argue that neutrino oscillations at JUNO offer a unique opportunity to study Sorkin's triple path interference, which is predicted to be zero in canonical quantum mechanics by virtue of the Born rule. In particular, we compute the expected bounds on triple path interference at JUNO and demonstrate that they are comparable to those already available from electromagnetic probes. Furthermore, the neutrino probe of the Born rule is much more direct due to an intrinsic independence from any boundary conditions, whereas such dependence on boundary conditions is always present in the case of electromagnetic probes. Thus, neutrino oscillations present an ideal probe of this aspect of the foundations of quantum mechanics.
  • Cerium Ruthenium Low-Energy Antineutrino Measurements for Safeguarding Military Naval Reactors
    Cogswell, Bernadette K.; Huber, Patrick (American Physical Society, 2022-06-14)
    The recent agreement to transfer nuclear submarine reactors and technology from two nuclear-weapon states to a non-nuclear-weapon state (AUKUS deal) highlights an unsolved problem in international safeguards: how to safeguard naval reactor fuel while it is on board an operational nuclear submarine. Proposals to extend existing safeguards technologies and practices are complicated by the need for civilian international inspectors to gain access to the interior of the submarine and the reactor compartment, which raises national security concerns. In this Letter we show that implementing safeguards on submarine propulsion reactors using a low-energy antineutrino reactor-off method, between submarine patrols, can by-pass the need for onboard access all together. We find that, using inverse beta decay, detectors can achieve a timely and high level of assurance that a submarine???s nuclear core has not been diverted (detector mass of around 100 kg) nor its enrichment level changed (detector mass of around 10 tons).
  • Toward diagnosing neutrino non-unitarity through CP phase correlations
    Minakata, Hisakazu (Oxford University Press, 2022-06-14)
    We discuss correlations between the neutrino-mass-embedded Standard Model CP phase d and the phases that originate from new physics which cause neutrino-sector unitarity violation (UV) at low energies. This study aims to provide one of the building blocks for machinery to diagnose non-unitarity, our ultimate goal. We extend the perturbation theory of neutrino oscillation in matter proposed by Denton et al. (DMP) to include the UV effect expressed by the alpha parametrization. By analyzing the DMP-UV perturbation theory to first order, we are able to draw a complete picture of the delta-UV phase correlations in the whole kinematical region covered by terrestrial neutrino experiments. Two regions exist with characteristically different patterns of the correlations: (i) the chiral-type [e(-i delta)alpha(mu e), e(-i delta)alpha(tau e), alpha(tau mu)] (Particle Data Group convention) correlation in the entire high-energy region vertical bar rho E vertical bar greater than or similar to 6 (g/cm(3)) GeV, and (ii) (blobs of the a parameters)-e(+/- i delta) correlation anywhere else. Some relevant aspects for the measurement of the UV parameters, such as the necessity of determining all the alpha(beta gamma) elements at once, are also pointed out.
  • Using DUNE to shed light on the electromagnetic properties of neutrinos
    Mathur, Varun; Shoemaker, Ian M.; Tabrizi, Zahra (2022-10-06)
    We study future DUNE sensitivity to various electromagnetic couplings of neutrinos, including magnetic moments, milli-charges, and charge radii. The DUNE PRISM capabilities play a crucial role in constraining the electron flavored couplings. We find that DUNE will be able to place the strongest beam based constraint on the muon-neutrino magnetic moment by improving on LSND’s bounds by roughly a factor of two, although Borexino’s constraint from solar neutrinos will be stronger. For the muon neutrino millicharge DUNE can place the leading beam based bound, with two orders of magnitude improvement compared to the existing COHERENT constraint, suggesting that DUNE can be useful for light mediators more generally. Despite this strength, the millicharge bounds are not competitive with strong bounds from stellar cooling, beta-decay, and matter stability. Finally, DUNE may be able to test the SM prediction for the muon neutrino charge radius, by placing a constraint two times better than CHARM-II and CCFR experiments.
  • Cosmic-ray upscattered inelastic dark matter
    Bell, Nicole F.; Dent, James B.; Dutta, Bhaskar; Ghosh, Sumit; Kumar, Jason; Newstead, Jayden L.; Shoemaker, Ian M. (American Physical Society, 2021-10-21)
    Light nonrelativistic components of the galactic dark matter halo elude direct detection constraints because they lack the kinetic energy to create an observable recoil. However, cosmic rays can upscatter dark matter to significant energies, giving direct detection experiments access to previously unreachable regions of parameter space at very low dark matter mass. In this work we extend the cosmic-ray dark matter formalism to models of inelastic dark matter and show that previously inaccessible regions of the mass-splitting p ammeter space can be probed. Conventional direct detection of nonrelativistic halo dark matter is limited to mass splittings of delta similar to 10 keV and is highly mass dependent. We find that including the effect of cosmic-ray upscattering can extend the reach to mass splittings of delta similar to 100 MeV and maintain that reach at much lower dark matter mass.
  • Optimization of the first CUPID detector module
    Alfonso, Krystal; Armatol, A.; Augier, C.; Avignone, F. T.; Azzolini, O.; Balata, M.; Barabash, A. S.; Bari, G.; Barresi, A.; Baudin, D.; Bellini, F.; Benato, G.; Beretta, M.; Bettelli, M.; Biassoni, M.; Billard, J.; Boldrini, V.; Branca, A.; Brofferio, C.; Bucci, C.; Camilleri, J.; Campani, A.; Capelli, C.; Capelli, S.; Cappelli, L.; Cardani, L.; Carniti, P.; Casali, N.; Celi, E.; Chang, C.; Chiesa, D.; Clemenza, M.; Colantoni, I.; Copello, S.; Craft, E.; Cremonesi, O.; Creswick, R. J.; Cruciani, A.; D’Addabbo, A.; D’Imperio, G.; Dabagov, S.; Dafinei, I.; Danevich, F. A.; De Jesus, M.; de Marcillac, P.; Dell’Oro, S.; Di Domizio, S.; Di Lorenzo, S.; Dixon, T.; Dompè, V.; Drobizhev, A.; Dumoulin, L.; Fantini, G.; Faverzani, M.; Ferri, E.; Ferri, F.; Ferroni, F.; Figueroa-Feliciano, E.; Foggetta, L.; Formaggio, J.; Franceschi, A.; Fu, C.; Fu, S.; Fujikawa, B. K.; Gallas, A.; Gascon, J.; Ghislandi, S.; Giachero, A.; Gianvecchio, A.; Gironi, L.; Giuliani, A.; Gorla, P.; Gotti, C.; Grant, C.; Gras, P.; Guillaumon, P. V.; Gutierrez, T. D.; Han, K.; Hansen, E. V.; Heeger, K. M.; Helis, D. L.; Huang, H. Z.; Imbert, L.; Johnston, J.; Juillard, A.; Karapetrov, G.; Keppel, G.; Khalife, H.; Kobychev, V. V.; Kolomensky, Yu. G.; Konovalov, S. I.; Kowalski, R.; Langford, T.; Lefevre, M.; Liu, R.; Liu, Y.; Loaiza, P.; Ma, L.; Madhukuttan, M.; Mancarella, F.; Marini, L.; Marnieros, S.; Martinez, M.; Maruyama, R. H.; Mas, Ph.; Mauri, B.; Mayer, D.; Mazzitelli, G.; Mei, Y.; Milana, S.; Morganti, S.; Napolitano, T.; Nastasi, M.; Nikkel, J.; Nisi, S.; Nones, C.; Norman, E. B.; Novosad, V.; Nutini, I.; O’Donnell, T.; Olivieri, E.; Olmi, M.; Ouellet, J. L.; Pagan, S.; Pagliarone, C.; Pagnanini, L.; Pattavina, L.; Pavan, M.; Peng, H.; Pessina, G.; Pettinacci, V.; Pira, C.; Pirro, S.; Poda, D. V.; Polischuk, O. G.; Ponce, I.; Pozzi, S.; Previtali, E.; Puiu, A.; Quitadamo, S.; Ressa, A.; Rizzoli, R.; Rosenfeld, C.; Rosier, P.; Scarpaci, J.; Schmidt, B.; Sharma, V.; Shlegel, V. N.; Singh, V.; Sisti, M.; Slocum, P.; Speller, D.; Surukuchi, P. T.; Taffarello, L.; Tomei, C.; Torres, J. A.; Tretyak, V. I.; Tsymbaliuk, A.; Velazquez, M.; Vetter, K. J.; Wagaarachchi, S. L.; Wang, G.; Wang, L.; Wang, R.; Welliver, B.; Wilson, J.; Wilson, K.; Winslow, L. A.; Xue, M.; Yan, L.; Yang, J.; Yefremenko, V.; Umatov, V. I.; Zarytskyy, M. M.; Zhang, J.; Zolotarova, A.; Zucchelli, S. (2022-09-12)
    CUPID will be a next generation experiment searching for the neutrinoless double 𝛽 decay, whose discovery would establish the Majorana nature of the neutrino. Based on the experience achieved with the CUORE experiment, presently taking data at LNGS, CUPID aims to reach a background free environment by means of scintillating Li2 100MoO4 crystals coupled to light detectors. Indeed, the simultaneous heat and light detection allows us to reject the dominant background of 𝛼 particles, as proven by the CUPID-0 and CUPID-Mo demonstrators. In this work we present the results of the first test of the CUPID baseline module. In particular, we propose a new optimized detector structure and light sensors design to enhance the engineering and the light collection, respectively. We characterized the heat detectors, achieving an energy resolution of (5.9 ± 0.2) keV FWHM at the Q-value of 100Mo (about 3034 keV). We studied the light collection of the baseline CUPID design with respect to an alternative configuration which features gravity-assisted light detectors’ mounting. In both cases we obtained an improvement in the light collection with respect to past measures and we validated the particle identification capability of the detector, which ensures an 𝛼 particle rejection higher than 99.9%, fully satisfying the requirements for CUPID.
  • Measuring tau neutrino appearance probability via unitarity
    Martinez-Soler, Ivan; Minakata, Hisakazu (American Physical Society, 2021-11-16)
    We propose a unitarity method for determining tau neutrino appearance probability P(nu mu -> nu tau) in longbaseline (LBL) accelerator experiments and atmospheric neutrino observations. When simultaneous in situ measurements of P(nu mu -> nu mu) and P(nu mu -> nu e) proceed, as is typical in the LBL experiments, one can use unitarity to "measure" P(nu mu -> nu tau). A theorists' toy analysis for the model-independent determination of P(nu mu -> nu mu) and P(nu mu -> nu e) is presented by using the NOvA data. It is shown in our analysis that less than or similar to 5% (8%) measurement of tau neutrino appearance probability in neutrino (antineutrino) mode is possible in the peak region 1.5 less than or similar to E nu less than or similar to 2.5 GeV. The nu SM-independent nature of determination of the probabilities is emphasized.
  • The Double Chooz antineutrino detectors
    de Kerret, H.; Abe, Y.; Aberle, C.; Abrahão, T.; Ahijado, J. M.; Akiri, T.; Alarcón, J. M.; Alba, J.; Almazan, H.; dos Anjos, J. C.; Appel, S.; Ardellier, F.; Barabanov, I.; Barriere, J. C.; Baussan, E.; Baxter, A.; Bekman, I.; Bergevin, M.; Bernstein, A.; Bertoli, W.; Bezerra, T. J. C.; Bezrukov, L.; Blanco, C.; Bleurvacq, N.; Blucher, E.; Bonet, H.; Bongrand, M.; Bowden, N. S.; Brugière, T.; Buck, C.; Avanzini, M. B.; Busenitz, J.; Cabrera, A.; Caden, E.; Calvo, E.; Camilleri, L.; Carr, R.; Cazaux, S.; Cela, J. M.; Cerrada, M.; Chang, P. J.; Charon, P.; Chauveau, E.; Chimenti, P.; Classen, T.; Collin, A. P.; Conover, E.; Conrad, J. M.; Cormon, S.; Corpace, O.; Courty, B.; Crespo-Anadón, J. I.; Cribier, M.; Crum, K.; Cuadrado, S.; Cucoanes, A.; D’Agostino, M.; Damon, E.; Dawson, J. V.; Dazeley, S.; Dierckxsens, M.; Dietrich, D.; Djurcic, Z.; Dorigo, F.; Dracos, M.; Durand, V.; Efremeko, Y.; Elnimr, M.; Etenko, A.; Falk, E.; Fallot, M.; Fechner, M.; Felde, J.; Fernandes, S. M.; Fernández-Bedoya, C.; Francia, D.; Franco, D.; Fischer, V.; Franke, A. J.; Franke, M.; Furuta, H.; Garcia, F.; Garcia, J.; Gil-Botella, I.; Giot, L.; Givaudan, A.; Göger-Neff, M.; Gomez, H.; Gonzalez, L. F. G.; Goodenough, L.; Goodman, M. C.; Goon, J.; Gramlich, B.; Greiner, D.; Guertin, A.; Guillon, B.; Habib, S. M.; Haddad, Y.; Hara, T.; Hartmann, F. X.; Hartnell, J.; Haser, J.; Hatzikoutelis, A.; Hellwig, D.; Hervé, S.; Hofacker, R.; Horton-Smith, G.; Hourlier, A.; Ishitsuka, M.; Jänner, K.; Jiménez, S.; Jochum, J.; Jollet, C.; Kaether, F.; Kale, K.; Kalousis, L.; Kamyshkov, Y.; Kaneda, M.; Kaplan, D. M.; Karakac, M.; Kawasaki, T.; Kemp, E.; Kibe, Y.; Kirchner, T.; Konno, T.; Kryn, D.; Kutter, T.; Kuze, M.; Lachenmaier, T.; Lane, C. E.; Langbrandtner, C.; Lasserre, T.; Lastoria, C.; Latron, L.; Leonardo, C.; Letourneau, A.; Lhuillier, D.; Lima, H. P.; Lindner, M.; López-Castaño, J. M.; LoSecco, J. M.; Lubsandorzhiev, B.; Lucht, S.; Maeda, J.; Maesano, C. N.; Mariani, Camillo; Maricic, J.; Marie, F.; Martinez, J. J.; Martino, J.; Matsubara, T.; McKee, D.; Meigner, F.; Mention, G.; Meregaglia, A.; Meyer, J. P.; Miletic, T.; Milincic, R.; Millot, J. F.; Minotti, A.; Mirones, V.; Miyata, H.; Mueller, Th. A.; Nagasaka, Y.; Nakajima, K.; Navas-Nicolás, D.; Nikitenko, Y.; Novella, P.; Oberauer, L.; Obolensky, M.; Onillon, A.; Oralbaev, A.; Ostrovskiy, I.; Palomares, C.; Peeters, S. J. M.; Pepe, I. M.; Perasso, S.; Perrin, P.; Pfahler, P.; Porta, A.; Pronost, G.; Puras, J. C.; Quéval, R.; Ramirez, J. L.; Reichenbacher, J.; Reinhold, B.; Reissfelder, M.; Remoto, A.; Reyna, D.; Rodriguez, I.; Röhling, M.; Roncin, R.; Rudolf, N.; Rybolt, B.; Sakamoto, Y.; Santorelli, R.; Sato, F.; Schwan, U.; Schönert, S.; Schoppmann, S.; Scola, L.; Settimo, M.; Shaevitz, M. A.; Sharankova, R.; Sibille, V.; Sida, J.-L.; Sinev, V.; Shrestha, D.; Skorokhvatov, M.; Soldin, P.; Spitz, J.; Stahl, A.; Stancu, I.; Starzynski, P.; Stock, M. R.; Stokes, L. F. F.; Strait, M.; Stüken, A.; Suekane, F.; Sukhotin, S.; Sumiyoshi, T.; Sun, Y.; Sun, Z.; Svoboda, R.; Tabata, H.; Tamura, N.; Terao, K.; Tonazzo, A.; Toral, F.; Toups, M.; Thi, H. T.; Valdivia, F.; Valdiviesso, G.; Vassilopoulos, N.; Verdugo, A.; Veyssiere, C.; Viaud, B.; Vignaud, D.; Vivier, M.; Wagner, S.; Wiebusch, C.; White, B.; Winslow, L.; Worcester, M.; Wurm, M.; Wurtz, J.; Yang, G.; Yáñez, J.; Yermia, F.; Zbiri, K. (2022-09-08)
    This article describes the setup and performance of the near and far detectors in the Double Chooz experiment. The electron antineutrinos of the Chooz nuclear power plant were measured in two identically designed detectors with different average baselines of about 400 m and 1050 m from the two reactor cores. Over many years of data taking the neutrino signals were extracted from interactions in the detectors with the goal of measuring a fundamental parameter in the context of neutrino oscillation, the mixing angle θ13. The central part of the Double Chooz detectors was a main detector comprising four cylindrical volumes filled with organic liquids. From the inside towards the outside there were volumes containing gadolinium-loaded scintillator, gadolinium-free scintillator, a buffer oil and, optically separated, another liquid scintillator acting as veto system. Above this main detector an additional outer veto system using plastic scintillator strips was installed. The technologies developed in Double Chooz were inspiration for several other antineutrino detectors in the field. The detector design allowed implementation of efficient background rejection techniques including use of pulse shape information provided by the data acquisition system. The Double Chooz detectors featured remarkable stability, in particular for the detected photons, as well as high radiopurity of the detector components.
  • Extending the reach of leptophilic boson searches at DUNE and MiniBooNE with bremsstrahlung and resonant production
    Capozzi, Francesco; Dutta, Bhaskar; Gurung, Gajendra; Jang, Wooyoung; Shoemaker, Ian M.; Thompson, Adrian; Yu, Jaehoon (American Physical Society, 2021-12-10)
    New gauge bosons coupling to leptons are simple and well-motivated extensions of the Standard Model. We study the sensitivity to gauged L-mu- L-e, L-e - L-tau and L-mu- L-tau both with the existing beam dump mode data of MiniBooNE and with the DUNE near detector. We find that including bremsstrahlung and resonant production of Z' which decays to e(+/-) and mu(+/-) final states leads to a significant improvement in existing bounds, especially for L-mu- L-e and L-e - L-tau for DUNE while competitive constraints can be achieved with the existing data from the MiniBooNE's beam dump run.
  • Active-to-sterile neutrino dipole portal and the XENON1T excess
    Shoemaker, Ian M.; Tsai, Yu-Dai; Wyenberg, Jason (American Physical Society, 2021-12-27)
    In this paper, we find that a magnetic transition dipole moment between tau and sterile neutrinos can account for the XENON1T excess events. Unlike the ordinary neutrino dipole moment, the introduction of the new sterile mass scale allows for astrophysical bounds to be suppressed. Interestingly, the best-fit regions that are compatible with the SN1987A imply either boron-8 as the source flux. We find that sterile neutrinos in the similar to(500-800) keV mass range are capable of evading astrophysical constraints while being able to successfully explain the XENON1T event rate. We also set new constraints on the dipole portal based on the Xenon 1T data. The sterile neutrino in the best fit parameter space may have significant effects on big bang nucleosynthesis (BBN). We show the region in which a low reheating temperature of the Universe may allow the BBN constraints to be alleviated.
  • Future searches for light sterile neutrinos at nuclear reactors
    Berryman, Jeffrey M.; Delgadillo, Luis A.; Huber, Patrick (American Physical Society, 2022-02-02)
    We study the optimization of a green-field, two-baseline reactor experiment with respect to the sensitivity for electron antineutrino disappearance in search of a light sterile neutrino. We consider both commercial and research reactors and identify as key factors the distance of closest approach and detector energy resolution. We find that a total of 5 tons of detectors deployed at a commercial reactor with a closest approach of 25 m can probe the mixing angle sin(2) 2 theta down to similar to 5 x 10(-3) around Delta m(2) similar to 1 eV(2). The same detector mass deployed at a research reactor can be sensitive up to Delta m(2) similar to 20-30 eV(2) assuming a closest approach of 3 m and excellent energy resolution, such as that projected for the Taishan Antineutrino Observatory. We also find that lithium doping of the reactor could be effective in increasing the sensitivity for higher Delta m(2) values.
  • Statistical significance of the sterile-neutrino hypothesis in the context of reactor and gallium data
    Berryman, Jeffrey M.; Coloma, Pilar; Huber, Patrick; Schwetz, Thomas; Zhou, Albert (Springer, 2022-02-08)
    We evaluate the statistical significance of the 3+1 sterile-neutrino hypothesis using nu(e) and (nu) over bar (e) disappearance data from reactor, solar and gallium radioactive source experiments. Concerning the latter, we investigate the implications of the recent BEST results. For reactor data we focus on relative measurements independent of flux predictions. For the problem at hand, the usual chi(2)-approximation to hypothesis testing based on Wilks' theorem has been shown in the literature to be inaccurate. We therefore present results based on Monte Carlo simulations, and find that this typically reduces the significance by roughly 1 sigma with respect to the naive expectation. We find no significant indication in favor of sterile-neutrino oscillations from reactor data. On the other hand, gallium data (dominated by the BEST result) show more than 5 sigma of evidence supporting the sterile-neutrino hypothesis, favoring oscillation parameters in agreement with constraints from reactor data. This explanation is, however, in significant tension (similar to 3 sigma) with solar neutrino experiments. In order to assess the robustness of the signal for gallium experiments we present a discussion of the impact of cross-section uncertainties on the results.