385,059 research outputs found
Chiral expansion of the decay width
A chiral field theory of mesons has been applied to study the contribution of
the current quark masses to the decay width at
the next leading order. enhancement has been predicted and there is no
new parameter.Comment: 9 page
The Lyman <span class='mathrm'>α</span> and Lyman <span class='mathrm'>β</span> lines in solar coronal streamers
No abstract available
Correlations of chaotic eigenfunctions: a semiclassical analysis
We derive a semiclassical expression for an energy smoothed autocorrelation
function defined on a group of eigenstates of the Schr\"odinger equation. The
system we considered is an energy-conserved Hamiltonian system possessing
time-invariant symmetry. The energy smoothed autocorrelation function is
expressed as a sum of three terms. The first one is analogous to Berry's
conjecture, which is a Bessel function of the zeroth order. The second and the
third terms are trace formulae made from special trajectories. The second term
is found to be direction dependent in the case of spacing averaging, which
agrees qualitatively with previous numerical observations in high-lying
eigenstates of a chaotic billiard.Comment: Revtex, 13 pages, 1 postscript figur
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Mitigation of microbunching instability in x-ray free electron laser linacs
The microbunching instability seeded by small initial density modulation and driven by collective effects can cause significant electron beam quality degradation in next generation x-ray free electron lasers. A method exploiting longitudinal mixing derived from the natural transverse spread of the electron beam through a dispersive bending magnet was proposed to suppress this instability several years ago [Phys. Rev. Lett. 111, 054801 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.054801]. Instead of using bending magnets to introduce the transverse-to-longitudinal coupling, which will lead to an inconvenient deflection of the downstream beam line, in this paper, we propose a scheme to mitigate the microbunching instability by inserting a quadrupole magnet inside a bunch compressor of the accelerator. This results in transverse-to-longitudinal phase space mixing and large slice energy spread that can efficiently mitigate the growth of the microbunching instability through the major accelerator section. Finally, at the exit of the accelerator, a dogleg section is used to restore the emittance and slice energy spread before entering the undulator radiation section. Multiparticle simulations show that the transverse space charge, structure wakefield, and the coherent synchrotron radiation effects will have a relatively small impact on this scheme
Quark Model Study of The eta Photoproduction: Evidence for a New S11 Resonance?
An extensive and systematic study of the recent eta photoproduction data up
to 1.2 GeV is presented within a chiral constituent quark model. A model
embodying all known nucleonic resonances shows clear need for a yet
undiscovered third S11 resonance in the second resonance region, for which we
determine the mass (1.729 GeV) and the total width (183 MeV). Furthermore, we
extract the configuration mixing angles, an important property of the
quark-quark interaction in the quark model, for the resonances S11(1535) and
S11(1650), as well as for the resonances D13(1520) and D13(1700). Our results
agree well with the quark model predictions. In addition, the partial eta N
decay widths and/or the photo-excitation helicity amplitudes for the nucleonic
resonances S11(1535), S11(1650), P11(1710), P13(1720), D13(1520), D13(1700),
D15(1675), and F15(1680) are also obtained in this approach.Comment: 25 pages, 5 figures, submitted to Eur. Phys.
Constraints on the CKM angle alpha in the B --> rho rho decays
Using a data sample of 122 million Upsilon(4S) -> BBbar decays collected with
BaBar detector at the PEP-II asymmetric B factory at SLAC, we measure the
time-dependent-asymmetry parameters of the longitudinally polarized component
in the B0 -> rho^+ rho^- decay as C_L = -0.23 +/- 0.24 (stat) +/- 0.14 (syst)
and S_L = -0.19 +/- 0.33 (stat) +/- 0.11 (syst). The B0 -> rho0 rho0 decay mode
is also searched for in a data sample of about 227 million BBbar pairs. No
significant signal is observed, and an upper limit of 1.1 * 10-6 (90% C.L.) on
the branching fraction is set. The penguin contribution to the CKM angle
uncertainty is measured to be 11 degree. All results are preliminary.Comment: 3 pages, 1 postscript figues, submitted to DPF200
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