We present the first results of the Fermilab National Accelerator Laboratory (FNAL) Muon g-2 Experiment for the positive muon magnetic anomaly a_{μ}≡(g_{μ}-2)/2. The anomaly is determined from the ...precision measurements of two angular frequencies. Intensity variation of high-energy positrons from muon decays directly encodes the difference frequency ω_{a} between the spin-precession and cyclotron frequencies for polarized muons in a magnetic storage ring. The storage ring magnetic field is measured using nuclear magnetic resonance probes calibrated in terms of the equivalent proton spin precession frequency ωover ˜_{p}^{'} in a spherical water sample at 34.7 °C. The ratio ω_{a}/ωover ˜_{p}^{'}, together with known fundamental constants, determines a_{μ}(FNAL)=116 592 040(54)×10^{-11} (0.46 ppm). The result is 3.3 standard deviations greater than the standard model prediction and is in excellent agreement with the previous Brookhaven National Laboratory (BNL) E821 measurement. After combination with previous measurements of both μ^{+} and μ^{-}, the new experimental average of a_{μ}(Exp)=116 592 061(41)×10^{-11} (0.35 ppm) increases the tension between experiment and theory to 4.2 standard deviations.
The sensitivity of the Deep Underground Neutrino Experiment (DUNE) to neutrino oscillation is determined, based on a full simulation, reconstruction, and event selection of the far detector and a ...full simulation and parameterized analysis of the near detector. Detailed uncertainties due to the flux prediction, neutrino interaction model, and detector effects are included. DUNE will resolve the neutrino mass ordering to a precision of 5
σ
, for all
δ
CP
values, after 2 years of running with the nominal detector design and beam configuration. It has the potential to observe charge-parity violation in the neutrino sector to a precision of 3
σ
(5
σ
) after an exposure of 5 (10) years, for 50% of all
δ
CP
values. It will also make precise measurements of other parameters governing long-baseline neutrino oscillation, and after an exposure of 15 years will achieve a similar sensitivity to
sin
2
2
θ
13
to current reactor experiments.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The Deep Underground Neutrino Experiment (DUNE), a 40-kton underground liquid argon time projection chamber experiment, will be sensitive to the electron-neutrino flavor component of the burst of ...neutrinos expected from the next Galactic core-collapse supernova. Such an observation will bring unique insight into the astrophysics of core collapse as well as into the properties of neutrinos. The general capabilities of DUNE for neutrino detection in the relevant few- to few-tens-of-MeV neutrino energy range will be described. As an example, DUNE’s ability to constrain the
ν
e
spectral parameters of the neutrino burst will be considered.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Many models of physics beyond the standard model predict the existence of new Abelian forces with new gauge bosons mediating interactions between "dark sectors" and the standard model. We report a ...search for a dark boson Z' coupling only to the second and third generations of leptons in the reaction e super(+) e super(?)arrowrightmu super(+)mu super(?)Z',Z'arrowrightmu super(+) mu? using 514fb super(?1) of data collected by the BABAR experiment. No significant signal is observed for Z' masses in the range 0.212-10 GeV. Limits on the coupling parameter g' as low as 7x10 super(?4) are derived, leading to improvements in the bounds compared to those previously derived from neutrino experiments.
Many scenarios of physics beyond the standard model predict the existence of new gauge singlets, which might be substantially lighter than the weak scale. The experimental constraints on additional ...scalars with masses in the MeV to GeV range could be significantly weakened if they interact predominantly with leptons rather than quarks. At an e+e− collider, such a leptophilic scalar (ϕL) would be produced predominantly through radiation from a τ lepton. We report herein a search for e+e−→τ+τ−ϕL, ϕL→ℓ+ℓ− (ℓ=e, μ) using data collected by the BABAR experiment at SLAC. No significant signal is observed, and we set limits on the ϕL coupling to leptons in the range 0.04<mϕL<7.0 GeV. These bounds significantly improve upon the current constraints, excluding almost entirely the parameter space favored by the observed discrepancy in the muon anomalous magnetic moment below 4 GeV at 90% confidence level.
We study the process e + e − → e + e − η ′ in the double-tag mode and measure for the first time the γ * γ * → η ′ transition form factor F η′ ( Q 2 1 , Q 2 2 ) in the momentum-transfer range 2 < Q 2 ...1 , Q 2 2 < 60 GeV 2 . The analysis is based on a data sample corresponding to an integrated luminosity of around 469 fb − 1 collected at the PEP-II e + e − collider with the BABAR detector at center-of-mass energies near 10.6 GeV.
Background: Copper amine oxidases are a ubiquitous and novel group of quinoenzymes that catalyze the oxidative deamination of primary amines to the corresponding aldehydes, with concomitant reduction ...of molecular oxygen to hydrogen peroxide. The enzymes are dimers of identical 70–90 kDa subunits, each of which contains a single copper ion and a covalently bound cofactor formed by the post-translational modification of a tyrosine side chain to 2,4,5-trihydroxyphenylalanine quinone (TPQ).
Results The crystal structure of amine oxidase from
Escherichia coli has been determined in both an active and an inactive form. The only structural differences are in the active site, where differences in copper coordination geometry and in the position and interactions of the redox cofactor, TPQ, are observed. Each subunit of the mushroom-shaped dimer comprises four domains: a 440 amino acid C-terminal
β sandwich domain, which contains the active site and provides the dimer interface, and three smaller peripheral
α/
β domains (D1–D3), each of about 100 amino acids. D2 and D3 show remarkable structural and sequence similarity to each other and are conserved throughout the quinoenzyme family. In contrast, D1 is absent from some amine oxidases. The active sites are well buried from solvent and lie some 35 å apart, connected by a pair of
β hairpin arms.
Conclusion The crystal structure of
E. coli copper amine oxidase reveals a number of unexpected features and provides a basis for investigating the intriguing similarities and differences in catalytic mechanism of members of this enzyme family. In addition to the three conserved histidines that bind the copper, our studies identify a number of other conserved residues close to the active site, including a candidate for the catalytic base and a fourth conserved histidine which is involved in an interesting intersubunit interaction.
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