51 results match your criteria: "Institute of Particle and Nuclear Physics[Affiliation]"

First measurement of neutrino oscillation parameters using neutrinos and antineutrinos by NOvA.

Phys Rev Lett

October 2019

Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA.

The NOvA experiment has seen a 4.4σ signal of ν[over ¯]_{e} appearance in a 2 GeV ν[over ¯]_{μ} beam at a distance of 810 km. Using 12.

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Precise Determination of the Branching Ratio of the Neutral-Pion Dalitz Decay.

Phys Rev Lett

January 2019

Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 18000 Praha 8, Czech Republic.

We provide a new value for the ratio R=Γ(π^{0}→e^{+}e^{-}γ(γ))/Γ(π^{0}→γγ)=11.978(6)×10^{-3}, which is by 2 orders of magnitude more precise than the current Particle Data Group average. It is obtained using the complete set of the next-to-leading-order radiative corrections in the QED sector, and incorporates up-to-date values of the π^{0}-transition-form-factor slope.

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Vector Effective Field Theories from Soft Limits.

Phys Rev Lett

June 2018

Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, California 91125, USA.

We present a bottom-up construction of vector effective field theories using the infrared structure of scattering amplitudes. Our results employ two distinct probes of soft kinematics: multiple soft limits and single soft limits after dimensional reduction applicable in four and general dimensions, respectively. Both approaches uniquely specify the Born-Infeld (BI) model as the only theory of vectors completely fixed by certain infrared conditions which generalize the Adler zero for pions.

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Individual Low-Energy Toroidal Dipole State in ^{24}Mg.

Phys Rev Lett

May 2018

Institut für Theoretische Physik II, Universität Erlangen, D-91058 Erlangen, Germany.

The low-energy dipole excitations in ^{24}Mg are investigated within the Skyrme quasiparticle random phase approximation for axial nuclei. The calculations with the force SLy6 reveal a remarkable feature: the lowest I^{π}K=1^{-}1 excitation (E=7.92  MeV) in ^{24}Mg is a vortical toroidal state (TS) representing a specific vortex-antivortex realization of the well-known spherical Hill's vortex in a strongly deformed axial confinement.

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Exceptional points near first- and second-order quantum phase transitions.

Phys Rev E

January 2018

Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague, Czech Republic.

We study the impact of quantum phase transitions (QPTs) on the distribution of exceptional points (EPs) of the Hamiltonian in the complex-extended parameter domain. Analyzing first- and second-order QPTs in the Lipkin-Meshkov-Glick model we find an exponentially and polynomially close approach of EPs to the respective critical point with increasing size of the system. If the critical Hamiltonian is subject to random perturbations of various kinds, the averaged distribution of EPs close to the critical point still carries decisive information on the QPT type.

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Article Synopsis
  • The study investigates the effects of nitric oxide (NO) deficiency on cardiovascular function in the brain stem of young and adult Wistar rats by examining the role of the AT1R-NAD(P)H oxidase-superoxide pathway.
  • Researchers treated rats with specific NO inhibitors and measured blood pressure, gene expression, and nitric oxide synthase (NOS) activity over six weeks.
  • Results showed that L-NAME (a non-specific NOS inhibitor) increased blood pressure and reduced NOS activity in both age groups, while antioxidant responses were enhanced in adult rats, indicating age-dependent differences in how NO deficiency affects oxidative stress and cardiovascular function.
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Constraints on Oscillation Parameters from ν_{e} Appearance and ν_{μ} Disappearance in NOvA.

Phys Rev Lett

June 2017

Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA.

Article Synopsis
  • The NOvA experiment improved measurements of muon neutrino (ν_{μ}) to electron neutrino (ν_{e}) transitions, detecting 33 ν_{e} candidates amid a background of 8.2±0.8.
  • Combining this data with recent ν_{μ} disappearance results and reactor experiment constraints,
  • the study disfavored the inverted mass hierarchy scenario for neutrino mixing at over 93% confidence level across all values of the CP-violating phase (δ_{CP}).
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Measurement of the Neutrino Mixing Angle θ_{23} in NOvA.

Phys Rev Lett

April 2017

Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA.

This Letter reports new results on muon neutrino disappearance from NOvA, using a 14 kton detector equivalent exposure of 6.05×10^{20} protons on target from the NuMI beam at the Fermi National Accelerator Laboratory. The measurement probes the muon-tau symmetry hypothesis that requires maximal θ_{23} mixing (θ_{23}=π/4).

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Ultrahigh energy cosmic ray air showers probe particle physics at energies beyond the reach of accelerators. Here we introduce a new method to test hadronic interaction models without relying on the absolute energy calibration, and apply it to events with primary energy 6-16 EeV (E_{CM}=110-170  TeV), whose longitudinal development and lateral distribution were simultaneously measured by the Pierre Auger Observatory. The average hadronic shower is 1.

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The Earth's engine is driven by unknown proportions of primordial energy and heat produced in radioactive decay. Unfortunately, competing models of Earth's composition reveal an order of magnitude uncertainty in the amount of radiogenic power driving mantle dynamics. Recent measurements of the Earth's flux of geoneutrinos, electron antineutrinos from terrestrial natural radioactivity, reveal the amount of uranium and thorium in the Earth and set limits on the residual proportion of primordial energy.

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We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8±0.

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First Measurement of Electron Neutrino Appearance in NOvA.

Phys Rev Lett

April 2016

Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA.

We report results from the first search for ν_{μ}→ν_{e} transitions by the NOvA experiment. In an exposure equivalent to 2.74×10^{20} protons on target in the upgraded NuMI beam at Fermilab, we observe 6 events in the Far Detector, compared to a background expectation of 0.

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On-Shell Recursion Relations for Effective Field Theories.

Phys Rev Lett

January 2016

Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, 91125 California, USA.

We derive the first ever on-shell recursion relations applicable to effective field theories. Based solely on factorization and the soft behavior of amplitudes, these recursion relations employ a new rescaling momentum shift to construct all tree-level scattering amplitudes in the nonlinear sigma model, Dirac-Born-Infeld theory, and the Galileon. Our results prove that all theories with enhanced soft behavior are on-shell constructible.

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Effective Field Theories from Soft Limits of Scattering Amplitudes.

Phys Rev Lett

June 2015

Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, California 91125, USA.

We derive scalar effective field theories-Lagrangians, symmetries, and all-from on-shell scattering amplitudes constructed purely from Lorentz invariance, factorization, a fixed power counting order in derivatives, and a fixed order at which amplitudes vanish in the soft limit. These constraints leave free parameters in the amplitude which are the coupling constants of well-known theories: Nambu-Goldstone bosons, Dirac-Born-Infeld scalars, and Galilean internal shift symmetries. Moreover, soft limits imply conditions on the Noether current which can then be inverted to derive Lagrangians for each theory.

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Energy-dependent patterns in the arrival directions of cosmic rays are searched for using data of the Pierre Auger Observatory. We investigate local regions around the highest-energy cosmic rays with [Formula: see text] eV by analyzing cosmic rays with energies above [Formula: see text] eV arriving within an angular separation of approximately 15[Formula: see text]. We characterize the energy distributions inside these regions by two independent methods, one searching for angular dependence of energy-energy correlations and one searching for collimation of energy along the local system of principal axes of the energy distribution.

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We developed a silicon avalanche photodiode (Si-APD) linear-array detector for use in nuclear resonant scattering experiments using synchrotron X-rays. The Si-APD linear array consists of 64 pixels (pixel size: 100 × 200 μm(2)) with a pixel pitch of 150 μm and depletion depth of 10 μm. An ultrafast frontend circuit allows the X-ray detector to obtain a high output rate of >10(7) cps per pixel.

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Search for photon-linelike signatures from dark matter annihilations with H.E.S.S.

Phys Rev Lett

January 2013

Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, D 22761 Hamburg, Germany.

Gamma-ray line signatures can be expected in the very-high-energy (E(γ)>100 GeV) domain due to self-annihilation or decay of dark matter (DM) particles in space. Such a signal would be readily distinguishable from astrophysical γ-ray sources that in most cases produce continuous spectra that span over several orders of magnitude in energy. Using data collected with the H.

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Regularity-induced separation of intrinsic and collective dynamics.

Phys Rev Lett

August 2010

Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics, Charles University, V Holesovickách 2, Prague, 18000, Czech Republic.

We propose that the adiabatic separation of collective and intrinsic motions in many-body systems is related to increased regularity of the intrinsic dynamics. The surmise is verified on the separation of rotations from intrinsic vibrations in the interacting boson model of nuclear structure.

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Quantum chaos in the nuclear collective model. II. Peres lattices.

Phys Rev E Stat Nonlin Soft Matter Phys

June 2009

Institute of Particle and Nuclear Physics, Charles University, V Holesovickách 2, 180 00 Prague, Czech Republic.

This is a continuation of our paper [Phys. Rev. E 79, 046202 (2009)] devoted to signatures of quantum chaos in the geometric collective model of atomic nuclei.

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Quantum chaos in the nuclear collective model: Classical-quantum correspondence.

Phys Rev E Stat Nonlin Soft Matter Phys

April 2009

Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics, Charles University, 180 00 Prague, Czech Republic.

Spectra of the geometric collective model of atomic nuclei are analyzed to identify chaotic correlations among nonrotational states. The model has been previously shown to exhibit a high degree of variability of regular and chaotic classical features with energy and control parameters. Corresponding signatures are now verified also on the quantum level for different schemes of quantization and with a variable classicality constant.

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Impact of quantum phase transitions on excited-level dynamics.

Phys Rev E Stat Nonlin Soft Matter Phys

September 2008

Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics, Charles University, V Holesovickách 2, 18000 Prague, Czech Republic.

The influence of quantum phase transitions on the evolution of excited levels in the critical parameter region is discussed. The analysis is performed for one- and two-dimensional systems with first- and second-order ground-state transitions. Examples include the cusp and nuclear collective Hamiltonians.

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Coulomb analogy for non-Hermitian degeneracies near quantum phase transitions.

Phys Rev Lett

September 2007

Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics, Charles University, V Holesovickách 2, 180 00 Prague, Czech Republic.

Degeneracies near the real axis in a complex-extended parameter space of a Hermitian Hamiltonian are studied. We present a method to measure distributions of such degeneracies on the Riemann sheet of a selected level and apply it in classification of quantum phase transitions. The degeneracies are shown to behave similarly as complex zeros of a partition function.

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Regular and chaotic vibrations of deformed nuclei with increasing gamma rigidity.

Phys Rev Lett

September 2004

Institute of Particle and Nuclear Physics, Charles University, V Holesovickách 2, 180 00 Prague, Czech Republic.

We study classical trajectories corresponding to L=0 vibrations in the geometric collective model of nuclei with stable axially symmetric quadrupole deformations. It is shown that with increasing stability against the onset of triaxiality the dynamics passes between a fully regular and semiregular limiting regime. In the transitional region, an interplay of chaotic and regular motions results in complex oscillatory dependence of the regular phase space on the Hamiltonian parameter and energy.

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Landau theory of shape phase transitions in the cranked interacting boson model.

Phys Rev Lett

March 2003

Institute of Particle and Nuclear Physics, Charles University, V Holesovickách 2, 180 00 Prague, Czech Republic.

Landau theory of phase transitions is applied to quadrupole shapes of rotating atomic nuclei within the interacting boson model (IBM) with cranking. It is shown that the coherent-state method must be generalized to allow for non-Hermitian quadrupole tensors of the coherent-state coefficients, which results in important modifications of the cranking shape-phase diagram compared to previous non-IBM studies of rotating nuclei. The parameter space has two surfaces of the first-order phase transitions and a curve of the second-order phase transition at their intersection.

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Decoherence and thermalization in a simple bosonic system.

Phys Rev E Stat Nonlin Soft Matter Phys

March 2001

Institute of Particle and Nuclear Physics, Charles University, V Holesovickách 2, 180 00 Prague, Czech Republic.

Properties of a parameter-dependent quantum system with the Hamiltonian H(lambda) randomized by fluctuations of the parameter lambda in a narrow range are investigated. The model employed (the interacting boson model-1) exhibits a crossover behavior at a critical parameter value. Due to the fluctuations, individual eigenstates /psi(alpha)(lambda)> of the Hamiltonian become statistical ensembles of states [density matrices rho(alpha)(lambda)], which allows us to study effects related to the decoherence and thermalization.

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