Project of NNbar Experiment at the WWR-M Reactor

Fomin, A. K.; Serebrov, A. P.; Zherebtsov, O. M.; Chaikovskii, M. E.; Murashkin, A. N.; Leonova, E.; Fedorova, O P; Ivochkin, V. G.; Lyamkin, V. A.; Prudnikov, D. V.; Chechkin, A. V.

doi:10.18502/ken.v3i1.1731

Cited by 4 publications

(5 citation statements)

References 7 publications

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“…Estimates based on Eq. (68) put BSM theories with scales of Λ BSM ∼ 700 TeV and O(1) matching coefficients within reach of nextgeneration experiments that will be able to detect baryon number violation with τ −1 n-n ≥ 10 9 s [49][50][51][52]. To more precisely assess the expected signatures of theories with B-violation at Λ BSM ∼ 700 TeV, the operators can be evolved V. Matrix element results for the chiral basis operators with independent non-zero matrix elements in the isospin limit.…”

Section: Resultsmentioning

confidence: 99%

Lattice QCD determination of neutron-antineutron matrix elements with physical quark masses

et al. 2019

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Matrix elements of six-quark operators are needed to extract new physics constraints from experimental searches for neutron-antineutron oscillations. This work presents in detail the first lattice quantum chromodynamics calculations of the necessary neutron-antineutron transition matrix elements including calculation methods and discussions of systematic uncertainties. Implications of isospin and chiral symmetry on the matrix elements, power counting in the isospin limit, and renormalization of a chiral basis of six-quark operators are discussed. Calculations are performed with a chiral-symmetric discretization of the quark action and physical light quark masses in order to avoid the need for chiral extrapolation. Non-perturbative renormalization is performed, including a study of lattice cutoff effects. Excited-state effects are studied using two nucleon operators and multiple values of source-sink separation. Results for the dominant matrix elements are found to be significantly larger compared to previous results from the MIT bag model. Future calculations are needed to fully account for systematic uncertainties associated with discretization and finite-volume effects but are not expected to significantly affect this conclusion. * erinaldi@bnl.gov †

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Section: Resultsmentioning

confidence: 99%

Lattice QCD determination of neutron-antineutron matrix elements with physical quark masses

et al. 2019

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“…To conclude, there has been recent phenomenological interest in n-n oscillations and the possibility of new searches for n-n vacuum oscillations and transitions in nuclei at ESS, DUNE, and other experiments [7][8][9]11]. The magnitudes of electroweak-singlet n-n transition matrix elements are 4-8 times larger than those computed in the "MIT bag model" [12].…”

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confidence: 89%

“…The best direct bound on τ n-n is from the cold neutron experiment at Institut Laue-Langevin (ILL), τ n-n > 0.89 × 10 8 s [6], which is essentially background-free and can be improved with larger neutron flux, magnetic shielding, and the latest technologies in neutron optics. There has been a proposal for a new cold neutron experiment at the European Spallation Source (ESS) that would be ≈ 10 3 times more sensitive than the ILL experiment and improve cold neutron constraints on τ n-n by a factor of 32 [7,8], as well as experiments at other reactors [9]. The best bound to date on the neutronantineutron transition time within Oxygen-16 is from Super-K, τ O 16 > 1.9×10 32 years [4], which constrains the free oscillation time τ n-n > 2.7 × 10 8 s after taking into account nuclear structure effects [10].…”

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confidence: 99%

Neutron-Antineutron Oscillations from Lattice QCD

et al. 2019

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Fundamental symmetry tests of baryon number violation in low-energy experiments can probe beyond the Standard Model (BSM) explanations of the matter-antimatter asymmetry of the universe. Neutron-antineutron oscillations are predicted to be a signature of many baryogenesis mechanisms involving low-scale baryon number violation. This work presents first-principles calculations of neutron-antineutron matrix elements needed to accurately connect measurements of the neutron-antineutron oscillation rate to constraints on |∆B| = 2 baryon number violation in BSM theories. Several important systematic uncertainties are controlled by using a state-of-the-art lattice gauge field ensemble with physical quark masses and approximate chiral symmetry, performing nonperturbative renormalization with perturbative matching to the MS scheme, and studying excited state effects in two-state fits. Phenomenological implications are highlighted by comparing expected bounds from proposed neutron-antineutron oscillation experiments to predictions of a specific model of post-sphaleron baryogenesis. Quantum chromodynamics is found to predict at least an order of magnitude more events in neutron-antineutron oscillation experiments than previous estimates based on the "MIT bag model" for fixed BSM parameters. Lattice artifacts and other systematic uncertainties that are not controlled in this pioneering calculation are not expected to significantly change this conclusion.

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“…The tightest constraints from cold neutron beam experiments on the n-n oscillation time τ n-n were obtained at the Institut Laue-Langevin (ILL) and give τ n-n > 0.86 × 10 8 s [101]. Future experiments have been proposed at the European Spallation Source (ESS) [102,103] that could improve bounds on τ n-n by a factor of 32, as well as at other reactors [104]. Nuclear n-n annihilation searches in large underground volume detectors provide competitive or even stronger bounds on B-L violation than neutron beam experiments, but are more difficult to interpret theoretically.…”

Section: Baryon-number Minus Lepton-number Nonconservation and N-n Os...mentioning

confidence: 99%

The role of Lattice QCD in searches for violations of fundamental symmetries and signals for new physics

et al. 2019

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Executive summary 2 BSM scenarios may involve new particles and interactions that originate at very high-energy scales, or alternatively may involve new physics at relatively low scales with extremely feeble couplings [10]. This whitepaper focuses on the former class of BSM scenarios, for which an effective field theory (EFT) framework can be adopted to encompass all SM extensions that respect the SM gauge group and have the same low-energy particle content as the SM [11][12][13]. One challenge that often needs to be dealt with in carrying out the program in Fundamental Symmetries is that the SM processes that are sensitive to new physics often involve hadrons and nuclei as initial, final, and/or intermediate states at low energies, demanding that SM and ab initio quantum many-body calculations be performed in a highly nonperturbative regime.The Department of Energy (DOE)-funded USQCD collaboration, as the unified collaboration of the majority of the LQCD collaborations in the U.S., has long identified the role of LQCD studies in enabling and advancing research at the Intensity Frontier. The significant results produced by the collaboration in the past two decades in constraining the Cabibbo-Kobayashi-Maskawa (CKM) matrix quark-mixing matrix of the SM, and in constraining the quantities relevant to tests of CP violation in the Kaon sector, mark major accomplishments for the LQCD community, and signify the essential role of LQCD in complimenting both experiment and theory effort in HEP research. Such a role has been identified in other sectors in which there is, or is expected to be, hints of deviation from the SM and of new physics. In particular, compared to the year 2013 when the Collaboration's previous whitepapers were released, in 2018 the Collaboration has dedicated three separate whitepapers to the role of LQCD in research at the Intensity Frontier: 1 i) Opportunities for LQCD in quark and lepton flavor physics: Given the persisting tensions between theoretical predictions based on the SM and and experimental measurements in B meson decays at the LHC-B and the anomalous magnetic moment of the muon at the Brookhaven National Laboratory, and the continuing improvement in determinations of the CP violating parameters in Kaon and recently the heavy-meson sectors, there is a pressing need for reliable SM predictions of corresponding quantities from LQCD, to a precision level that is comparable to experimental determinations. Progress made by the USQCD collaboration in all these areas, the challenges ahead, and the plans forward are detailed in a companion whitepaper, see [6].ii) LQCD and neutrino-nucleus scattering: The large experimental enterprise in neutrino physics, in particular the upcoming Deep Underground Neutrino Experiment (DUNE) at Fermilab aims to shed light on CP violation in the lepton sector. However, reliable determinations of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) lepton-mixing matrix require accurate knowledge of neutrino-nucleus interactions. The neutrino-nucleon and neutrinonucleus scatt...

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Project of NNbar Experiment at the WWR-M Reactor

Cited by 4 publications

References 7 publications

Lattice QCD determination of neutron-antineutron matrix elements with physical quark masses

Lattice QCD determination of neutron-antineutron matrix elements with physical quark masses

Neutron-Antineutron Oscillations from Lattice QCD

The role of Lattice QCD in searches for violations of fundamental symmetries and signals for new physics

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