12,814,095 research outputs found
Exotic Baryons and Monopole Excitations in a Chiral Soliton Model
We compute the spectra of exotic pentaquarks and monopole excitations of the
low--lying and baryons in a chiral soliton model. Once the
low--lying baryon properties are fit, the other states are predicted without
any more adjustable parameters. This approach naturally leads to a scenario in
which the mass spectrum of the next to lowest--lying states is
fairly well approximated by the ideal mixing pattern of the
representation of flavor SU(3). We compare
our results to predictions obtained in other pictures for pentaquarks and
speculate about the spin--parity assignment for and Comment: 16 pages, 2 figures, 6 table
Structure of the Isovector Dipole Resonance in Neutron-Rich Nucleus and Direct Decay from Pygmy Resonance
The structure of the isovector dipole resonance in neutron-rich calcium
isotope, , has been investigated by implementing a careful treatment
of the differences of neutron and proton radii in the continuum random phase
approximation (). The calculations have taken into account the current
estimates of the neutron skin. The estimates of the escape widths for direct
neutron decay from the pygmy dipole resonance () were shown rather wide,
implicating a strong coupling to the continuum. The width of the giant dipole
resonance () was evaluated, bringing on a detailed discussion about its
microscopic structure.Comment: 13 pages, 2 figures, RevTex
Reconclining phi radiative decays with other data for a0(980), fo(980), pi-pi -> KK and pi-pi -> eta-eta
Data for phi -> gamma (eta-pizero) are analysed using the KK loop model and
compared with parameters of a0(980) derived from Crystal Barrel data. The
eta-pi mass spectrum agrees closely and the absolute normalisation lies just
within errors. However, BES parameters for fo(980) predict a normalisation for
phi -> gamma (pizero-pizero) at least a factor 2 lower than is observed. This
discrepancy may be eliminated by including constructive interference between
fo(980) and sigma. The magnitude required for sigma -> KK is consistent with
data on pi-pi -> KK. A dispersion relation analysis by Buttiker, Descotes-Genon
and Moussallam of pi-pi -> KK leads to a similar conclusion. Data on pi-pi ->
eta-eta also require decays of sigma to eta-eta. Four sets of pi-pi -> KK data
all require a small but definite fo(1370) signal.Comment: 21 pages, 11 figures, Small rearrangement of reference
Associated production of a light Higgs boson and a chargino pair in the MSSM at linear colliders
In the Minimal Supersymmetric Standard Model (MSSM), we study the light
Higgs-boson radiation off a light-chargino pair in the process e+e- -> h chi^+
chi^- at linear colliders with \sqs=500 GeV. We analyze cross sections in the
regions of the MSSM parameter space where the process can not proceed via
on-shell production and subsequent decay of either heavier charginos or the
pseudoscalar Higgs boson A. Cross sections up to a few fb's are allowed,
according to present experimental limits on the Higgs-boson, chargino and
sneutrino masses. We also show how a measurement of the process production rate
could provide a determination of the Higgs-boson couplings to charginos.Comment: 26 pages, 9 figures; figure misplacement fixed; to appear in
Eur.Phys.J.
The Making of the Standard Model
This is the edited text of a talk given at CERN on Septembr 16, 2003, as part
of a celebration of the 30th anniversary of the discovery of neutral currents
and the 20th anniversary of the discovery of the W and Z particles.Comment: 21 page
Quantifying bid-ask spreads in the Chinese stock market using limit-order book data: Intraday pattern, probability distribution, long memory, and multifractal nature
The statistical properties of the bid-ask spread of a frequently traded
Chinese stock listed on the Shenzhen Stock Exchange are investigated using the
limit-order book data. Three different definitions of spread are considered
based on the time right before transactions, the time whenever the highest
buying price or the lowest selling price changes, and a fixed time interval.
The results are qualitatively similar no matter linear prices or logarithmic
prices are used. The average spread exhibits evident intraday patterns
consisting of a big L-shape in morning transactions and a small L-shape in the
afternoon. The distributions of the spread with different definitions decay as
power laws. The tail exponents of spreads at transaction level are well within
the interval and that of average spreads are well in line with the
inverse cubic law for different time intervals. Based on the detrended
fluctuation analysis, we found the evidence of long memory in the bid-ask
spread time series for all three definitions, even after the removal of the
intraday pattern. Using the classical box-counting approach for multifractal
analysis, we show that the time series of bid-ask spread does not possess
multifractal nature.Comment: 8 EPJ pages including 7 eps figure
Two-pion Bose-Einstein correlations in central Pb-Pb collisions at = 2.76 TeV
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb
collisions at TeV at the Large Hadron Collider is
presented. We observe a growing trend with energy now not only for the
longitudinal and the outward but also for the sideward pion source radius. The
pion homogeneity volume and the decoupling time are significantly larger than
those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/388
On kaonic hydrogen. Quantum field theoretic and relativistic covariant approach
We study kaonic hydrogen, the bound K^-p state A_(Kp). Within a quantum field
theoretic and relativistic covariant approach we derive the energy level
displacement of the ground state of kaonic hydrogen in terms of the amplitude
of K^-p scattering for arbitrary relative momenta. The amplitude of low-energy
K^-p scattering near threshold is defined by the contributions of three
resonances Lambda(1405), Lambda(1800) and Sigma^0(1750) and a smooth elastic
background. The amplitudes of inelastic channels of low-energy K^-p scattering
fit experimental data on near threshold behaviour of the cross sections and the
experimental data by the DEAR Collaboration. We use the soft-pion technique
(leading order in Chiral Perturbation Theory) for the calculation of the
partial width of the radiative decay of pionic hydrogen A_(pi p) -> n + gamma
and the Panofsky ratio. The theoretical prediction for the Panofsky ratio
agrees well with experimental data. We apply the soft-kaon technique (leading
order in Chiral Perturbation Theory) to the calculation of the partial widths
of radiative decays of kaonic hydrogen A_(Kp) -> Lambda^0 + gamma and A_(Kp) ->
Sigma^0 + gamma. We show that the contribution of these decays to the width of
the energy level of the ground state of kaonic hydrogen is less than 1%.Comment: 33 pages, 1 figure, latex, References are adde
Creating Ioffe-Pritchard micro-traps from permanent magnetic film with in-plane magnetization
We present designs for Ioffe-Pritchard type magnetic traps using planar
patterns of hard magnetic material. Two samples with different pattern designs
were produced by spark erosion of 40 m thick FePt foil. The pattern on the
first sample yields calculated axial and radial trap frequencies of 51 Hz and
6.8 kHz, respectively. For the second sample the calculated frequencies are 34
Hz and 11 kHz. The structures were used successfully as a magneto-optical trap
for Rb and loaded as a magnetic trap. A third design, based on
lithographically patterned 250 nm thick FePt film on a Si substrate, yields an
array of 19 traps with calculated axial and radial trap frequencies of 1.5 kHz
and 110 kHz, respectively.Comment: 8 pages, 5 figures Revised and accepted for EPJD, improved picture
Wavelet transform modulus maxima based fractal correlation analysis
The wavelet transform modulus maxima (WTMM) used in the singularity analysis
of one fractal function is extended to study the fractal correlation of two
multifractal functions. The technique is developed in the framework of joint
partition function analysis (JPFA) proposed by Meneveau et al. [1] and is shown
to be equally effective. In addition, we show that another leading approach
developed for the same purpose, namely, relative multifractal analysis, can be
considered as a special case of JPFA at a particular parameter setting.Comment: 18 pgs, 5 fig
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