Search results for "Variant"
showing 10 items of 1267 documents
Non-standard neutrino oscillations: perspective from unitarity triangles
2021
We formulate an alternative approach based on unitarity triangles to describe neutrino oscillations in presence of non-standard interactions (NSI). Using perturbation theory, we derive the expression for the oscillation probability in case of NSI and cast it in terms of the three independent parameters of the leptonic unitarity triangle (LUT). The form invariance of the probability expression (even in presence of new physics scenario as long as the mixing matrix is unitary) facilitates a neat geometric view of neutrino oscillations in terms of LUT. We examine the regime of validity of perturbative expansions in the NSI case and make comparisons with approximate expressions existing in liter…
Role of the f 1 (1285) state in theJ/ψ→ϕK¯K⁎and J / ψ → ϕf 1 (1285) decays
2016
Abstract We study the role of the f 1 ( 1285 ) resonance in the decays of J / ψ → ϕ K ¯ K ⁎ and J / ψ → ϕ f 1 ( 1285 ) . The theoretical approach is based on the results of chiral unitary theory where the f 1 ( 1285 ) resonance is dynamically generated from the K ⁎ K ¯ – c.c. interaction. In order to further test the dynamical nature of the f 1 ( 1285 ) state, we investigate the J / ψ → ϕ K ¯ K ⁎ decay close to the K ¯ K ⁎ threshold and make predictions for the ratio of the invariant mass distributions of the J / ψ → ϕ K ¯ K ⁎ decay and the J / ψ → ϕ f 1 ( 1285 ) partial decay width with all the parameters of the mechanism fixed in previous studies. The results can be tested in future exper…
Structure of chromomagnetic fields in the glasma
2014
The initial stage of a heavy ion collision is dominated by nonperturbatively strong chromoelectric and -magnetic fields. The spatial Wilson loop provides a gauge invariant observable to probe the dynamics of the longitudinal chromomagnetic field. We discuss recent results from a real time lattice calculation of the area-dependence of the expectation value of the spatial Wilson loop. We show that at relatively early times after the collision, a universal scaling as a function of the area emerges at large distances for very different initial conditions, with a nontrivial critical exponent. A similar behavior has earlier been seen in calculations of the gluon transverse momentum spectrum, whic…
The role of charged exotic states in e+e− → ψ(2S) π+π−
2019
Abstract In this work, we use the dispersion theory to provide a physical description of recent BESIII data on the reaction e + e − → ψ ( 2 S ) π + π − . Taking into account explicitly the effects of charged exotic intermediate states in the t- and u-channels as well as the two-pion final state interaction, we describe the invariant mass distribution for four different e + e − center-of-mass energies. The effects of the ππ rescattering are accounted for in a single channel Omnes approach which is found to explain the ππ-invariant mass distributions at all e + e − center-of-mass energies. For q = 4.226 GeV and q = 4.258 GeV the already established charged exotic state Z c ( 3900 ) is conside…
Double- π0 photoproduction from the deuteron
2000
The photoproduction of two neutral pions from the deuteron has been studied for incident photon energies from 200 MeV to 820 MeV with the TAPS spectrometer at MAMI (Mainz Microtron). The total cross-section was determined and used to deduce the cross-section from the neutron. Due to the good statistical quality of the data Dalitz plots for the three particles in the exit channel (pi (0)pi N-0) could be constructed. The invariant mass distributions derived from them are presented in this paper. They indicate that the important reaction mechanism in the second resonance region is a sequential decay pattern involving the population of the Delta (1232)-resonance as an intermediate state.
Invarianzgruppen von Bewegungsgleichungen mit Kommutatorring
1967
An attempt to describe particles by hermitian operators obeying commutator relations leads to a ring of sixteen elements to be represented by matrices of infinite rank. Equations of motion containing elements of the ring are shown to be invariant under charge-conjugation, time-reversal and inhomogeneous Lorentz transformations. Analogs to Pauli- and Gursey-transformations can also be defined and may be used to introduce isospin and helicity.
η→π0γγdecay within a chiral unitary approach revisited
2008
In view of the recent experimental developments in η→π^(0)γ γ decay, and the fact that the Particle Data Group in the online edition of 2007 reports sizable changes of the radiative decay widths of vector mesons used as input in the theoretical calculations of E. Oset, J. R. Pelaez, and L. Roca [Phys. Rev. D 67, 073013 (2003)], a reevaluation of the decay width of the in this channel has been done, reducing its uncertainty by almost a factor of 2. The new input of the Particle Data Group is used, and invariant mass distributions and total widths are compared with the most recent results from the AGS and MAMI experiments, and preliminary ones of KLOE. The agreement of the theory with the AGS…
Two neutral pion photoproduction off the proton between threshold and 800 MeV
1997
Abstract The photoproduction of two neutral pions off the proton has been studied for incident photon energies between E γ = 309 MeV (threshold) and 792 MeV with the TAPS photon spectrometer at the Mainz Microtron MAMI. Both 3γ- and 4γ-events have been analysed in order to deduce the total p ( γ , 2 π 0 ) p cross section. The total cross section is less than 300 nb between threshold and ⋍ 460 MeV, beyond which it starts to rise to a maximum value of about 11 μb at around 750 MeV. For the highest energies it starts to decrease again. The 4γ-sample has been used to reconstruct 2 neutral pions from the above reaction channel by an invariant mass and a missing mass analysis. After reconstructio…
EXTRACTION OF ΛΛ SCATTERING LENGTH
2009
We determine ΛΛ scattering parameters from a ΛΛ invariant mass spectrum that was obtained by 12 C (K-, K+ΛΛ) reaction at the KEK Proton Synchrotron. In the framework of Watson's procedure, the obtained scattering length [Formula: see text] and effective range [Formula: see text] are most consistent with the values predicted by using the Nijmegen soft core models (NSC97's). However, the predicted values by using the Nijmegen hard-core ND ( G -matrix) and the extended soft-core (ESC00) models are out of two standard deviations from the determined scattering parameters.
A theoretical view on bound antikaon-nuclear states
2008
We present an overview of the latest theoretical studies on the antikaon properties in the nuclear medium, in connection with the recent experimental claims of very deeply bound antikaon-nuclear states. We argue that proper many-body formulations using modern realistic antikaon-nucleon interactions are not able to generate such systems. Instead, a simple two-nucleon antikaon absorption mechanism where the remaining nucleus acts as spectator explains the peak in the semi-inclusive proton momentum spectrum, observed on a 4He target at KEK (but later not confirmed in an inclusive experiment) and on a 6Li target at FINUDA. This signal is clearly seen in another FINUDA experiment measuring the i…