• Neutrinos are lighter than 0.8 electronv

    From ScienceDaily@1:317/3 to All on Mon Feb 14 21:30:48 2022
    Neutrinos are lighter than 0.8 electronvolts
    New world record: KATRIN experiment limits neutrino mass with
    unprecedented precision

    Date:
    February 14, 2022
    Source:
    Max Planck Institute for Physics
    Summary:
    New research has broken an important 'barrier' in neutrino physics
    which is relevant for both particle physics and cosmology. A new
    upper limit of 0.8 electronvolt (eV) for the mass of the neutrino
    has been obtained.

    This first push into the sub-eV mass scale of neutrinos by a model-
    independent laboratory method allows KATRIN to constrain the mass of
    these 'lightweights of the universe' with unprecedented precision.



    FULL STORY ==========================================================================
    The international KArlsruhe TRItium Neutrino Experiment (Katrin), located
    at Karlsruhe Institute of Technology (KIT), has broken an important
    "barrier" in neutrino physics which is relevant for both particle physics
    and cosmology.

    Based on new data a new upper limit of 0.8 electronvolt (eV) for the
    mass of the neutrino has been obtained. This first push into the sub-eV
    mass scale of neutrinos by a model-independent laboratory method allows
    Katrin to constrain the mass of these lightweights of the universe with unprecedented precision.


    ========================================================================== Neutrinos are arguably the most fascinating elementary particle in our universe. In cosmology they play an important role in the formation
    of large- scale structures, while in particle physics their tiny but
    non-zero mass sets them apart, pointing to new physics phenomena beyond
    our current theories.

    Without a measurement of the mass scale of neutrinos our understanding
    of the universe will remain incomplete.

    This is the challenge the international KATRIN experiment at Karlsruhe Institute of Technology (KIT) with partners from six countries has taken
    up as the world's most sensitive scale for neutrinos. It makes use of the
    beta decay of tritium, an unstable hydrogen isotope, to determine the
    mass of the neutrino via the energy distribution of electrons released
    in the decay process. This necessitates a major technological effort:
    the 70 meter long experiment houses the world's most intense tritium
    source as well as a giant spectrometer to measure the energy of decay
    electrons with unprecedented precision.

    The high quality of the data after starting scientific measurements in
    2019 has continuously been improved over the last two years. "KATRIN
    is an experiment with the highest technological requirements and is now
    running like perfect clockwork" enthuses Guido Drexlin (KIT), the project leader and one of the two co-spokespersons of the experiment. Christian Weinheimer (University of Mu"nster), the other co-spokesperson, adds that
    "the increase of the signal rate and the reduction of background rate
    were decisive for the new result." Data analysis The in-depth analysis
    of this data was demanding everything from the international analysis
    team led by its two coordinators, Susanne Mertens (Max Planck Institute
    for Physics and TU Munich) and Magnus Schlo"sser (KIT). Each and every
    effect, no matter how small, had to be investigated in detail. "Only by
    this laborious and intricate method we were able to exclude a systematic
    bias of our result due to distorting processes. We are particularly proud
    of our analysis team which successfully took up this huge challenge with
    great commitment," the two analysis coordinators are pleased to report.

    The experimental data from the first year of measurements and the modeling based on a vanishingly small neutrino mass match perfectly: from this,
    a new upper limit on the neutrino mass of 0.8 eV can be determined
    (Nature Physics, July 2021). This is the first time that a direct neutrino
    mass experiment has entered the cosmologically and particle-physically important sub-eV mass range, where the fundamental mass scale of neutrinos
    is suspected to be. "The particle physics community is excited that the 1-eV-barrier has been broken by KATRIN," comments neutrino expert John Wilkerson (University of North Carolina, Chair of the Executive Board).

    Susanne Mertens explains the path to the new record: "Our team at the MPP
    in Munich has developed a new analysis method for KATRIN that is specially optimized for the requirements of this high-precision measurement. This strategy has been successfully used for past and current results. My
    group is highly motivated: We will continue to meet the future challenges
    of KATRIN analysis with new creative ideas and meticulous accuracy."
    Further measurements should improve sensitivity The co-spokespersons and analysis coordinators of KATRIN are very optimistic about the future:
    "Further measurements of the neutrino mass will continue until the
    end of 2024. To realise the full potential of this unique experiment,
    we will not only steadily increase the statistics of signal events, we
    are continuously developing and installing improvements to further lower
    the background rate." The development of a new detector system (TRISTAN)
    plays a specific role in this, allowing KATRIN from 2025 on to embark on a search for "sterile" neutrinos with masses in the kiloelectronvolt-range,
    a candidate for the mysterious dark matter in the cosmos that has already manifested itself in many astrophysical and cosmological observations,
    but whose particle-physical nature is still unknown.

    ========================================================================== Story Source: Materials provided by
    Max_Planck_Institute_for_Physics. Note: Content may be edited for style
    and length.


    ========================================================================== Related Multimedia:
    *
    Mounting_of_electrodes_in_main_spectrometer_of_KATRIN_experiment,_and
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    Link to news story: https://www.sciencedaily.com/releases/2022/02/220214111754.htm

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