arXiv subjects

Carsten Rott

Publications and source records attributed to Carsten Rott.

At least 37 records · Page 2Linked to original sources

arXiv2018

Status and Prospects of the JSNS2 Experiment

The JSNS$^2$ experiment aims to search for the existence of neutrino oscillations with $Δ{\rm m}^2$ near 1 eV$^2$ at the J-PARC Materials and Life Science Experimental Facility (MLF). A 3~GeV 1~MW proton beam incident on a mercury target produces an intense neutrino source from muon decay at rest ($μ^{+} \rightarrow e^{+} + \barν_μ + ν_{e}$). The oscillation to be searched for is $\barν_μ$ to $\barν_{e}$, detected via the inverse beta decay~(IBD) reaction ($\barν_{e} + p \rightarrow e^{+} + n$), which is then distinctively tagged by gammas from neutron capture of Gadolinium. The first of two detectors with 17 tons fiducial volume is currently under construction at a distance of 24 m from the mercury target. JSNS$^2$ is expected to provide the ultimate test of the LSND anomaly by replicating nearly identical conditions. The status of the experiment, which is expected to start taking data in Spring 2019, is discussed and its physics potential reviewed.

physics.ins-det↗

arXiv2017

Status of Dark Matter Searches (Rapporteur Talk)

This article reviews the status of the field of dark matter as of summer 2017, when it was discussed at 35th International Cosmic Ray Conference (ICRC 2017) in Busan, Korea. It is the write-up of a rapporteur talk on the status of dark matter searches given at the conference.

astro-ph.HE↗

arXiv2017

Solar Atmospheric Neutrinos: A New Neutrino Floor for Dark Matter Searches

As is well known, dark matter direct detection experiments will ultimately be limited by a "neutrino floor," due to the scattering of nuclei by MeV neutrinos from, e.g., nuclear fusion in the Sun. Here we point out the existence of a new "neutrino floor" that will similarly limit indirect detection with the Sun, due to high-energy neutrinos from cosmic-ray interactions with the solar atmosphere. We have two key findings. First, solar atmospheric neutrinos $\lesssim 1$ TeV cause a sensitivity floor for standard WIMP scenarios, for which higher-energy neutrinos are absorbed in the Sun. This floor will be reached once the present sensitivity is improved by just one order of magnitude. Second, for neutrinos $\gtrsim 1$ TeV, which can be isolated by muon energy loss rate, solar atmospheric neutrinos should soon be detectable in IceCube. Discovery will help probe the complicated effects of solar magnetic fields on cosmic rays. These events will be backgrounds to WIMP scenarios with long-lived mediators, for which higher-energy neutrinos can escape from the Sun.

astro-ph.HE↗

arXiv2017

New Dark Matter Search Strategies at DUNE

If dark matter annihilates to light quarks in the core of the Sun, then a flux of 236 MeV neutrinos will be produced from the decay of stopped kaons. We consider strategies for DUNE to not only observe such a signal, but to determine the direction of the neutrino from the hadronic recoil. We show that this novel strategy can provide a better handle on systematic uncertainties associated with dark matter searches.

hep-ph↗

arXiv2017

Enhanced Photon Traps for Hyper-Kamiokande

Hyper-Kamiokande, the next generation large water Cherenkov detector in Japan, is planning to use approximately 80,000 20-inch photomultiplier tubes (PMTs). They are one of the major cost factors of the experiment. We propose a novel enhanced photon trap design based on a smaller and more economical PMT in combination with wavelength shifters, dichroic mirrors, and broadband mirrors. GEANT4 is utilized to obtain photon collection efficiencies and timing resolution of the photon traps. We compare the performance of different trap configurations and sizes. Our simulations indicate an enhanced photon trap with a 12-inch PMT can match a 20-inch PMTs collection efficiency, however at a cost of reduced timing resolution. The photon trap might be suitable as detection module for the outer detector with large photo coverage area.

astro-ph.IM↗

arXiv2017

Directional Searches at DUNE for Sub-GeV Monoenergetic Neutrinos Arising from Dark Matter Annihilation in the Sun

We consider the use of directionality in the search for monoenergetic sub-GeV neutrinos arising from the decay of stopped kaons, which can be produced by dark matter annihilation in the core of the Sun. When these neutrinos undergo charged-current interactions with a nucleus at a neutrino detector, they often eject a proton which is highly peaked in the forward direction. The direction of this track can be measured at DUNE, allowing one to distinguish signal from background by comparing on-source and off-source event rates. We find that directional information can enhance the signal to background ratio by up to a factor of 5.

hep-ph↗

arXiv2016

First Observation of Time Variation in the Solar-Disk Gamma-Ray Flux with Fermi

The solar disk is a bright gamma-ray source. Surprisingly, its flux is about one order of magnitude higher than predicted. As a first step toward understanding the physical origin of this discrepancy, we perform a new analysis in 1-100 GeV using 6 years of public Fermi-LAT data. Compared to the previous analysis by the Fermi Collaboration, who analyzed 1.5 years of data and detected the solar disk in 0.1-10 GeV, we find two new and significant results: 1. In the 1-10 GeV flux (detected at $>5σ$), we discover a significant time variation that anticorrelates with solar activity. 2. We detect gamma rays in 10-30 GeV at $>5σ$, and in 30-100 GeV at $> 2σ$. The time variation strongly indicates that solar-disk gamma rays are induced by cosmic rays and that solar atmospheric magnetic fields play an important role. Our results provide essential clues for understanding the underlying gamma-ray production processes, which may allow new probes of solar atmospheric magnetic fields, cosmic rays in the solar system, and possible new physics. Finally, we show that the Sun is a promising new target for ground-based TeV gamma-ray telescopes such as HAWC and LHAASO.

astro-ph.HE↗

arXiv2015

Dark Matter Searches for Monoenergetic Neutrinos Arising from Stopped Meson Decay in the Sun

Dark matter can be gravitationally captured by the Sun after scattering off solar nuclei. Annihilations of the dark matter trapped and accumulated in the centre of the Sun could result in one of the most detectable and recognizable signals for dark matter. Searches for high-energy neutrinos produced in the decay of annihilation products have yielded extremely competitive constraints on the spin-dependent scattering cross sections of dark matter with nuclei. Recently, the low energy neutrino signal arising from dark-matter annihilation to quarks which then hadronize and shower has been suggested as a competitive and complementary search strategy. These high-multiplicity hadronic showers give rise to a large amount of pions which will come to rest in the Sun and decay, leading to a unique sub-GeV neutrino signal. We here improve on previous works by considering the monoenergetic neutrino signal arising from both pion and kaon decay. We consider searches at liquid scintillation, liquid argon, and water Cherenkov detectors and find very competitive sensitivities for few-GeV dark matter masses.

hep-ph↗

arXiv2015

Solar WIMPs Unraveled: Experiments, astrophysical uncertainties, and interactive Tools

The absence of a neutrino flux from self-annihilating dark matter captured in the Sun has tightly constrained some leading particle dark matter scenarios. The impact of astrophysical uncertainties on the capture process of dark matter in the Sun and hence also the derived constraints by neutrino telescopes need to be taken into account. In this review we have explored relevant uncertainties in solar WIMP searches, summarized results from leading experiments, and provided an outlook into upcoming searches and future experiments. We have created an interactive plotting tool that allows the user to view current limits and projected sensitivities of major experiments under changing astrophysical conditions.

astro-ph.HE↗

arXiv2015

Superheavy dark matter and IceCube neutrino signals:bounds on decaying dark matter

Superheavy dark matter may show its presence in high energy neutrino signals detected on earth. From the latest results of IceCube, we could set the strongest lower bound on the lifetime of dark matter beyond 100 TeV around $10^{28} {\rm sec}$. The excess around a PeV is noticed and may be interpreted as the first signal of DM even though further confirmation and dedicated searches are invited.

hep-ph↗

arXiv2015

The Leptoquark Implication from the CMS and IceCube Experiments

The recent excess in the CMS measurements of $eejj$ and $eνjj$ channels and the emergence of PeV comsic neutrino events at the IceCube experiment share an intriguing implication for a leptoquark with a 600-650 GeV mass. We investigate the CMS constraints on the flavor structure of a scenario with the minimal leptoquark Yukawa couplings and correlate such a scenario to the resonant enhancement in the very high energy shower event rates at the IceCube. We find for a single leptoquark, the CMS signals require large couplings to the third generation leptons. This leads to an enhancement in the $ν_τ$-nucleon scattering cross-section and subsequently more $ν_τ$ events at PeV energies. However, a visible enhancement above the Standard Model scattering would require a leptoquark Yukawa coupling larger than one that can be easily tested at the upcoming LHC runs.

hep-ph↗

arXiv2015

Spectrometry of the Earth using Neutrino Oscillations

The unknown constituents of the interior of our home planet have provoked the human imagination and driven scientific exploration. We herein demonstrate that large neutrino detectors could be used in the near future to significantly improve our understanding of the Earth's inner chemical composition. Neutrinos, which are naturally produced in the atmosphere, traverse the Earth and undergo oscillations that depend on the Earth's electron density. The Earth's chemical composition can be determined by combining observations from large neutrino detectors with seismic measurements of the Earth's matter density. We present a method that will allow us to perform a measurement that can distinguish between composition models of the outer core. We show that the next-generation large-volume neutrino detectors can provide sufficient sensitivity to reject outer core models with large hydrogen content and thereby demonstrate the potential of this novel method. In the future, dedicated instruments could be capable of distinguishing between specific Earth composition models and thereby reshape our understanding of the inner Earth in previously unimagined ways.

physics.geo-ph↗

arXiv2014

Impact of Dark Matter Velocity Distributions on Capture Rates in the Sun

Dark matter could be captured in the Sun and self-annihilate, giving rise to an observable neutrino flux. Indirect searches for dark matter looking for this signal with neutrino telescopes have resulted in tight constraints on the interaction cross-section of dark matter with ordinary matter. We investigate how robust limits are against astro-physical uncertainties. We study the effect of the velocity distribution of dark matter in our Galaxy on capture rates in the Sun. We investigate four sources of uncertainties: orbital speed of the Sun, escape velocity of dark matter from the halo, dark matter velocity distribution functions and existence of a dark disc. We find that even extreme cases currently discussed do not decrease the sensitivity of indirect detection significantly because the capture is achieved over a broad range of the velocity distribution by integration over the velocity distribution. The effect of the uncertainty in the high-velocity tail of dark matter halo is very marginal as the capture process is rather inefficient at this region. The difference in capture rate in the Sun for various scenarios is compared to the expected change in event rates for direct detection. The possibility of co-rotating structure with the Sun can largely boost the signal and hence makes the interpretation of indirect detection conservative compared to direct detection.

astro-ph.HE↗

arXiv2013

A Novel Approach to Study Atmospheric Neutrino Oscillation

We develop a general theoretical framework to analytically disentangle the contributions of the neutrino mass hierarchy, the atmospheric mixing angle, and the CP phase, in neutrino oscillations. To illustrate the usefulness of this framework, especially that it can serve as a complementary tool to neutrino oscillogram in the study of atmospheric neutrino oscillations, we take PINGU as an example and compute muon- and electron-like event rates with event cuts on neutrino energy and zenith angle. Under the assumption of exact momentum measurements of neutrinos with a perfect e-$μ$ identification and no backgrounds, we find that the PINGU experiment has the potential of resolving the neutrino mass hierarchy and the octant degeneracies within 1-year run, while the measurement of the CP phase is significantly more challenging. Our observation merits a serious study of the detector capability of estimating the neutrino momentum for both muon- and electron-like events.

hep-ph↗

arXiv2013

New Sensitivity to Solar WIMP Annihilation using Low-Energy Neutrinos

Dark matter particles captured by the Sun through scattering may annihilate and produce neutrinos, which escape. Current searches are for the few high-energy neutrinos produced in the prompt decays of some final states. We show that interactions in the solar medium lead to a large number of pions for nearly all final states. Positive pions and muons decay at rest, producing low-energy neutrinos with known spectra, including nuebar through neutrino mixing. We demonstrate that Super-Kamiokande can thereby provide a new probe of the spin-dependent WIMP-proton cross section. Compared to other methods, the sensitivity is competitive and the uncertainties are complementary.

astro-ph.HE↗

arXiv2012

Review of Indirect WIMP Search Experiments

Observational evidence for dark matter can be explained by Weakly Interacting Massive Particles (WIMPs). These dark matter particle candidates could indirectly be detected through the observation of signals produced as part of WIMP annihilations or decays. Latest results from indirect searches for WIMPs are reviewed. Current and planned experiments are presented and their prospects and discovery potential discussed.

astro-ph.HE↗

arXiv2011

Enhanced Sensitivity to Dark Matter Self-annihilations in the Sun using Neutrino Spectral Information

Self-annihilating dark matter gravitationally captured by the Sun could yield observable neutrino signals at current and next generation neutrino detectors. By exploiting such signals, neutrino detectors can probe the spin-dependent scattering of weakly interacting massive particles (WIMPs) with nucleons in the Sun. We describe a method how to convert constraints on neutrino fluxes to a limit on the WIMP-nucleon scattering cross section. In this method all neutrino flavors can be treated in a very similar way. We study the sensitivity of neutrino telescopes for Solar WIMP signals using vertex contained events and find that this detection channel is of particular importance in the search for low mass WIMPs. We obtain highly competitive sensitivities with all neutrino flavor channels for a Megaton sized detector through the application of basic spectral selection criteria. Best results are obtained with the electron neutrino channel. We discuss associated uncertainties and provide a procedure how to treat them for analyses in a consistent way.

astro-ph.HE↗

arXiv2009

Search for Dark Matter from the Galactic Halo with IceCube

Neutrinos produced in dark matter self-annihilations in the Galactic halo might be detectable by IceCube. We present a search for such a signal using the IceCube detector in the 22-string configuration. We first evaluate the sensitivity before presenting the result based on the collected data. We find that even with the partially instrumented detector and a small dataset, we are able to meaningfully constrain the dark matter self-annihilation cross-section. Future analyses, based on data sets from a larger detector and the inclusion of the Galactic center, are expected to considerably improve these results.

astro-ph.HE↗