484 research outputs found
Hard-core Final State Interaction Effects in Deep Inelastic Scattering
Hard-core final state interaction effects in the response function are
investigated in the asymptotic limit of momentum transfer q->Infinity. A new
treatment of the response is presented, which displays the relevant scattering
contribution. A modification of the otherwise expected free response is
obtained for Fermi and Bose systems and smearing of the condensate peak is
shown in this limit. A comparison with other treatments of final state
interactions is made.Comment: 13 pages, in RevTex. To be published in Physics Letters A. Figures
can be obtained from [email protected]
BFV-complex and higher homotopy structures
We present a connection between the BFV-complex (abbreviation for
Batalin-Fradkin-Vilkovisky complex) and the so-called strong homotopy Lie
algebroid associated to a coisotropic submanifold of a Poisson manifold. We
prove that the latter structure can be derived from the BFV-complex by means of
homotopy transfer along contractions. Consequently the BFV-complex and the
strong homotopy Lie algebroid structure are quasi-isomorphic and
control the same formal deformation problem.
However there is a gap between the non-formal information encoded in the
BFV-complex and in the strong homotopy Lie algebroid respectively. We prove
that there is a one-to-one correspondence between coisotropic submanifolds
given by graphs of sections and equivalence classes of normalized Maurer-Cartan
elemens of the BFV-complex. This does not hold if one uses the strong homotopy
Lie algebroid instead.Comment: 50 pages, 6 figures; version 4 is heavily revised and extende
Ultrafast photoinduced charge transport in Pt(II) donor-acceptor assembly bearing naphthalimide electron acceptor and phenothiazine electron donor
Visible light-induced charge transfer dynamics were investigated in a novel transition metal triad acceptor–chromophore–donor, (NDI–phen)Pt(II)(–C[triple bond, length as m-dash]C–Ph–CH2–PTZ)2 (1), designed for photoinduced charge separation using a combination of time-resolved infrared (TRIR) and femtosecond electronic transient absorption (TA) spectroscopy. In 1, the electron acceptor is 1,4,5,8-naphthalene diimide (NDI), and the electron donor is phenothiazine (PTZ), and [(phen)Pt(–C[triple bond, length as m-dash]C–Ph–)], where phen is 1,10-phenanthroline, represents the chromophoric core. The first excited state observed in 1 is a 3MLCT/LL′CT, with {Pt(II)–acetylide}-to-phen character. Following that, charge transfer from the phen-anion onto the NDI subunit to form NDI−–phen–[Pt–(C[triple bond, length as m-dash]C)2]+–PTZ2 occurs with a time constant of 2.3 ps. This transition is characterised by appearance of the prominent NDI-anion features in both TRIR and TA spectra. The final step of the charge separation in 1 proceeds with a time constant of [similar]15 ps during which the hole migrates from the [Pt–(C[triple bond, length as m-dash]C)2] subunit to one of the PTZ groups. Charge recombination in 1 then occurs with two distinct time constants of 36 ns and 107 ns, corresponding to the back electron transfer to each of the two donor groups; a rather rare occurrence which manifests that the hole in the final charge-separated state is localised on one of the two donor PTZ groups. The assignment of the nature of the excited states and dynamics in 1 was assisted by TRIR investigations of the analogous previously reported ((COOEt)2bpy)Pt(C[triple bond, length as m-dash]C–Ph–CH2–PTZ)2 (2), (J. E. McGarrah and R. Eisenberg, Inorg. Chem., 2003, 42, 4355; J. E. McGarrah, J. T. Hupp and S. N. Smirnov, J. Phys. Chem. A, 2009, 113, 6430) as well as (bpy)Pt(C[triple bond, length as m-dash]C–Ph–C7H15)2, which represent the acceptor-free dyad, and the chromophoric core, respectively. Thus, the step-wise formation of the full charge-separated state on the picosecond time scale and charge recombination via tunnelling have been established; and the presence of two distinct charge recombination pathways has been observed
Kaon-Nucleon Scattering Amplitudes and Z-Enhancements from Quark Born Diagrams
We derive closed form kaon-nucleon scattering amplitudes using the ``quark
Born diagram" formalism, which describes the scattering as a single interaction
(here the OGE spin-spin term) followed by quark line rearrangement. The low
energy I=0 and I=1 S-wave KN phase shifts are in reasonably good agreement with
experiment given conventional quark model parameters. For Gev
however the I=1 elastic phase shift is larger than predicted by Gaussian
wavefunctions, and we suggest possible reasons for this discrepancy. Equivalent
low energy KN potentials for S-wave scattering are also derived. Finally we
consider OGE forces in the related channels K, KN and K,
and determine which have attractive interactions and might therefore exhibit
strong threshold enhancements or ``Z-molecule" meson-baryon bound states.
We find that the minimum-spin, minimum-isospin channels and two additional
K channels are most conducive to the formation of bound states.
Related interesting topics for future experimental and theoretical studies of
KN interactions are also discussed.Comment: 34 pages, figures available from the authors, revte
Field-linked States of Ultracold Polar Molecules
We explore the character of a novel set of ``field-linked'' states that were
predicted in [A. V. Avdeenkov and J. L. Bohn, Phys. Rev. Lett. 90, 043006
(2003)]. These states exist at ultralow temperatures in the presence of an
electrostatic field, and their properties are strongly dependent on the field's
strength. We clarify the nature of these quasi-bound states by constructing
their wave functions and determining their approximate quantum numbers. As the
properties of field-linked states are strongly defined by anisotropic dipolar
and Stark interactions, we construct adiabatic surfaces as functions of both
the intermolecular distance and the angle that the intermolecular axis makes
with the electric field. Within an adiabatic approximation we solve the 2-D
Schrodinger equation to find bound states, whose energies correlate well with
resonance features found in fully-converged multichannel scattering
calculations
Radiative decays with light scalar mesons and singlet-octet mixing in ChPT
We study different types of radiative decays involving f0(980) and a0(980)
mesons within a unified ChPT-based approach at one-loop level. Light scalar
resonances which are seen in pi pi, pi eta, K K-bar channels of phi(1020)
radiative decays and in J/psi decays are responsible for key questions of
low-energy dynamics in the strong interaction sector, and decays phi(1020) ->
gamma a0(980), phi(1020) -> gamma f0(980), a0(980) -> gamma gamma, f0(980) ->
gamma gamma are of interest for current experimental programs in Juelich,
Frascati and Novosibirsk. From theoretical point of view it is important to
verify whether light scalar mesons are members of some flavor octet or nonet.
We find a value of mixing angle dictated by consistency with experiment and
coupling structures of ChPT Lagrangian. Decay widths f0(980)/a0(980) -> gamma
rho(770)/omega(782), which are not studied experimentally yet, are predicted.
We also obtain several relations between widths, which hold independently of
coupling constants and represent a fingerprint of the model.Comment: 18 pages, 8 figures; misprints in text and tables corrected,
discussion extended, references added; version accepted for publication in
Eur.Phys.J.
On the intersystem crossing rate in a Platinum(ii) donor–bridge–acceptor triad
The rates of ultrafast intersystem crossing in acceptor–bridge–donor molecules centered on Pt(II) acetylides are investigated. Specifically, a Pt(II) trans-acetylide triad NAP–[triple bond, length as m-dash]–Pt–[triple bond, length as m-dash]–Ph-CH2-PTZ [1], with acceptor 4-ethynyl-N-octyl-1,8-naphthalimide (NAP) and donor phenothiazine (PTZ), is examined in detail. We have previously shown that optical excitation in [1] leads to a manifold of singlet charge-transfer states, S*, which evolve via a triplet charge-transfer manifold into a triplet state 3NAP centered on the acceptor ligand and partly to a charge-separated state 3CSS (NAP−–Pt–PTZ+). A complex cascade of electron transfer processes was observed, but intersystem crossing (ISC) rates were not explicitly resolved due to lack of spin selectivity of most ultrafast spectroscopies. Here we revisit the question of ISC with a combination and complementary analysis of (i) transient absorption, (ii) ultrafast broadband fluorescence upconversion, FLUP, which is only sensitive to emissive states, and (iii) femtosecond stimulated Raman spectroscopy, FSR. Raman resonance conditions allow us to observe S* and 3NAP exclusively by FSR, through vibrations which are pertinent only to these two states. This combination of methods enabled us to extract the intersystem crossing rates that were not previously accessible. Multiple timescales (1.6 ps to ∼20 ps) are associated with the rise of triplet species, which can now be assigned conclusively to multiple ISC pathways from a manifold of hot charge-transfer singlet states. The analysis is consistent with previous transient infrared spectroscopy data. A similar rate of ISC, up to 20 ps, is observed in the trans-acetylide NAP–[triple bond, length as m-dash]–Pt–[triple bond, length as m-dash]–Ph [2] which maintains two acetylide groups across the platinum center but lacks a donor unit, whilst removal of one acetylide group in mono-acetylide NAP–[triple bond, length as m-dash]–Pt–Cl [3] leads to >10-fold deceleration of the intersystem crossing process. Our work provides insight on the intersystem crossing dynamics of the organo-metallic complexes, and identifies a general method based on complementary ultrafast spectroscopies to disentangle complex spin, electronic and vibrational processes following photoexcitation
Differential cross section and recoil polarization measurements for the gamma p to K+ Lambda reaction using CLAS at Jefferson Lab
We present measurements of the differential cross section and Lambda recoil
polarization for the gamma p to K+ Lambda reaction made using the CLAS detector
at Jefferson Lab. These measurements cover the center-of-mass energy range from
1.62 to 2.84 GeV and a wide range of center-of-mass K+ production angles.
Independent analyses were performed using the K+ p pi- and K+ p (missing pi -)
final-state topologies; results from these analyses were found to exhibit good
agreement. These differential cross section measurements show excellent
agreement with previous CLAS and LEPS results and offer increased precision and
a 300 MeV increase in energy coverage. The recoil polarization data agree well
with previous results and offer a large increase in precision and a 500 MeV
extension in energy range. The increased center-of-mass energy range that these
data represent will allow for independent study of non-resonant K+ Lambda
photoproduction mechanisms at all production angles.Comment: 22 pages, 16 figure
Study of the Decay phi --> eta pi0 gamma with the KLOE detector
In a sample of 5.3x10^7 phi-decays observed with the KLOE detector at the
Frascati phi-factory Dafne we find 605 eta pi0 gamma events with eta -->
gamma\gamma and 197 eta pi0 gamma events with eta --> pi+ pi- pi0. The decay
phi --> eta pi0 gamma is dominated by the process phi --> a0 gamma. From a fit
to the eta pi0 mass spectrum we find BR(phi --> ao(980) gamma)= (7.4 +-
0.7)x10^-5.Comment: 12 pages, 6 figures, submitted to Phys.Lett.
Complete measurement of three-body photodisintegration of 3He for photon energies between 0.35 and 1.55 GeV
The three-body photodisintegration of 3He has been measured with the CLAS
detector at Jefferson Lab, using tagged photons of energies between 0.35 GeV
and 1.55 GeV. The large acceptance of the spectrometer allowed us for the first
time to cover a wide momentum and angular range for the two outgoing protons.
Three kinematic regions dominated by either two- or three-body contributions
have been distinguished and analyzed. The measured cross sections have been
compared with results of a theoretical model, which, in certain kinematic
ranges, have been found to be in reasonable agreement with the data.Comment: 22 pages, 25 eps figures, 2 tables, submitted to PRC. Modifications:
removed 2 figures, improvements on others, a few minor modifications to the
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