166 research outputs found
Measurements of spin rotation parameter A in pion-proton elastic scattering at 1.62 GeV/c
The ITEP-PNPI collaboration presents the results of the measurements of the
spin rotation parameter A in the elastic scattering of positive and negative
pions on protons at P_beam = 1.62 GeV/c. The setup included a
longitudinally-polarized proton target with superconductive magnet, multiwire
spark chambers and a carbon polarimeter with thick filter. Results are compared
to the predictions of partial wave analyses. The experiment was performed at
the ITEP proton synchrotron, Moscow.Comment: 7 pages, 3 figures. To be published in Phys. Lett.
Revisiting the SN1987A gamma-ray limit on ultralight axion-like particles
We revise the bound from the supernova SN1987A on the coupling of ultralight
axion-like particles (ALPs) to photons. In a core-collapse supernova, ALPs
would be emitted via the Primakoff process, and eventually convert into gamma
rays in the magnetic field of the Milky Way. The lack of a gamma-ray signal in
the GRS instrument of the SMM satellite in coincidence with the observation of
the neutrinos emitted from SN1987A therefore provides a strong bound on their
coupling to photons. Due to the large uncertainty associated with the current
bound, we revise this argument, based on state-of-the-art physical inputs both
for the supernova models and for the Milky-Way magnetic field. Furthermore, we
provide major amendments, such as the consistent treatment of
nucleon-degeneracy effects and of the reduction of the nuclear masses in the
hot and dense nuclear medium of the supernova. With these improvements, we
obtain a new upper limit on the photon-ALP coupling: g_{a\gamma} < 5.3 x
10^{-12} GeV^{-1}, for m_a < 4.4 x 10^{-10} eV, and we also give its dependence
at larger ALP masses. Moreover, we discuss how much the Fermi-LAT satellite
experiment could improve this bound, should a close-enough supernova explode in
the near future.Comment: Accepted for publication in JCAP (December 22nd, 2014
Gauge Formulation for Higher Order Gravity
This work is an application of the second order gauge theory for the Lorentz
group, where a description of the gravitational interaction is obtained which
includes derivatives of the curvature. We analyze the form of the second field
strenght, , in terms of geometrical variables. All possible
independent Lagrangians constructed with quadratic contractions of and
quadratic contractions of are analyzed. The equations of motion for a
particular Lagrangian, which is analogous to Podolsky's term of his Generalized
Electrodynamics, are calculated. The static isotropic solution in the linear
approximation was found, exhibiting the regular Newtonian behaviour at short
distances as well as a meso-large distance modification.Comment: Published versio
First Measurement of A_N at sqrt(s)=200 GeV in Polarized Proton-Proton Elastic Scattering at RHIC
We report on the first measurement of the single spin analyzing power (A_N)
at sqrt(s)=200GeV, obtained by the pp2pp experiment using polarized proton
beams at the Relativistic Heavy Ion Collider (RHIC). Data points were measured
in the four momentum transfer t range 0.01 < |t| < 0.03 (GeV/c)^2. Our result,
averaged over the whole t-interval is about one standard deviation above the
calculation, which uses interference between electromagnetic spin-flip
amplitude and hadronic non-flip amplitude, the source of A_N. The difference
could be explained by an additional contribution of a hadronic spin-flip
amplitude to A_N.Comment: 13 pages, 5 figures. New values of polarization errors. Final version
submitted to Phys. Lett.
Membranes with a boundary
We investigate the recently developed theory of multiple membranes. In
particular, we consider open membranes, i.e. the theory defined on a membrane
world volume with a boundary. We first restrict our attention to the gauge
sector of the theory. We obtain a boundary action from the Chern-Simons terms.
Secondly, we consider the addition of certain boundary terms to various
Chern-Simons theories coupled to matter. These terms ensure the full bulk plus
boundary action has the correct amount of supersymmetry. For the ABJM model,
this construction motivates the inclusion of a boundary quartic scalar
potential. The boundary dynamics obtained from our modified theory produce
Basu-Harvey type equations describing membranes ending on a fivebrane. The
ultimate goal of this work is to throw light on the theory of fivebranes using
the theory of open membranes.Comment: 48 pages, Latex, v2 references adde
Model dependence of single-energy fits to pion photoproduction data
Model dependence of multipole analysis has been explored through
energy-dependent and single-energy fits to pion photoproduction data. The MAID
energy-dependent solution has been used as input for an event generator
producing realistic pseudo data. These were fitted using the SAID
parametrization approach to determine single-energy and energy-dependent
solutions over a range of lab photon energies from 200 to 1200 MeV. The
resulting solutions were found to be consistent with the input amplitudes from
MAID. Fits with a -squared per datum of unity or less were generally
achieved. We discuss energy regions where consistent results are expected, and
explore the sensitivity of fits to the number of included single- and
double-polarization observables. The influence of Watson's theorem is examined
in detail.Comment: 12 pages, 8 figure
P-wave excited baryons from pion- and photo-induced hyperon production
We report evidence for , , ,
, , and , and find
indications that might have a companion state at 1970\,MeV. The
controversial is not seen. The evidence is derived from a
study of data on pion- and photo-induced hyperon production, but other data are
included as well. Most of the resonances reported here were found in the
Karlsruhe-Helsinki (KH84) and the Carnegie-Mellon (CM) analyses but were
challenged recently by the Data Analysis Center at GWU. Our analysis is
constrained by the energy independent scattering amplitudes from either
KH84 or GWU. The two amplitudes from KH84 or GWU, respectively, lead to
slightly different branching ratios of contributing resonances but the
debated resonances are required in both series of fits.Comment: 22 pages, 28 figures. Some additional sets of data are adde
Electron self-trapping in intermediate-valent SmB6
SmB6 exhibits intermediate valence in the ground state and unusual behaviour
at low temperatures. The resistivity and the Hall effect cannot be explained
either by conventional sf-hybridization or by hopping transport in an impurity
band. At least three different energy scales determine three temperature
regimes of electron transport in this system. We consider the ground state
properties, the soft valence fluctuations and the spectrum of band carriers in
n-doped SmB6. The behaviour of excess conduction electrons in the presence of
soft valence fluctuations and the origin of the three energy scales in the
spectrum of elementary excitations is discussed. The carriers which determine
the low-temperature transport in this system are self-trapped electron-polaron
complexes rather than simply electrons in an impurity band. The mechanism of
electron trapping is the interaction with soft valence fluctuations.Comment: 12 pages, 3 figure
First Measurement of Proton-Proton Elastic Scattering at RHIC
The first result of the pp2pp experiment at RHIC on elastic scattering of
polarized protons at sqrt{s} = 200 GeV is reported here. The exponential slope
parameter b of the diffractive peak of the elastic cross section in the t range
0.010 <= |t| <= 0.019 (GeV/c)^2 was measured to be b = 16.3 +- 1.6 (stat.) +-
0.9 (syst.) (GeV/c)^{-2} .Comment: 9 pages 5 figure
Higgs Bundles, Gauge Theories and Quantum Groups
The appearance of the Bethe Ansatz equation for the Nonlinear Schr\"{o}dinger
equation in the equivariant integration over the moduli space of Higgs bundles
is revisited. We argue that the wave functions of the corresponding
two-dimensional topological U(N) gauge theory reproduce quantum wave functions
of the Nonlinear Schr\"{o}dinger equation in the -particle sector. This
implies the full equivalence between the above gauge theory and the
-particle sub-sector of the quantum theory of Nonlinear Schr\"{o}dinger
equation. This also implies the explicit correspondence between the gauge
theory and the representation theory of degenerate double affine Hecke algebra.
We propose similar construction based on the gauged WZW model leading to
the representation theory of the double affine Hecke algebra. The relation with
the Nahm transform and the geometric Langlands correspondence is briefly
discussed.Comment: 48 pages, typos corrected, one reference adde
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