1,600 research outputs found
On the Use of Quantum Algebras in Rotation-Vibration Spectroscopy
A two-parameter deformation of the Lie algebra u is used, in conjunction
with the rotor system and the oscillator system, to generate a model for
rotation-vibration spectroscopy of molecules and nuclei.Comment: 10 pages, Latex File, published in Modern Group Theoretical Methods
in Physics, J. Bertrand et al. (eds.), Kluwer Academic Publishers (1995),
27-3
Determining matrix elements and resonance widths from finite volume: the dangerous mu-terms
The standard numerical approach to determining matrix elements of local
operators and width of resonances uses the finite volume dependence of energy
levels and matrix elements. Finite size corrections that decay exponentially in
the volume are usually neglected or taken into account using perturbation
expansion in effective field theory. Using two-dimensional sine-Gordon field
theory as "toy model" it is shown that some exponential finite size effects
could be much larger than previously thought, potentially spoiling the
determination of matrix elements in frameworks such as lattice QCD. The
particular class of finite size corrections considered here are mu-terms
arising from bound state poles in the scattering amplitudes. In sine-Gordon
model, these can be explicitly evaluated and shown to explain the observed
discrepancies to high precision. It is argued that the effects observed are not
special to the two-dimensional setting, but rather depend on general field
theoretic features that are common with models relevant for particle physics.
It is important to understand these finite size corrections as they present a
potentially dangerous source of systematic errors for the determination of
matrix elements and resonance widths.Comment: 26 pages, 13 eps figures, LaTeX2e fil
R-parity violation in SU(5)
We show that judiciously chosen R-parity violating terms in the minimal
renormalizable supersymmetric SU(5) are able to correct all the
phenomenologically wrong mass relations between down quarks and charged
leptons. The model can accommodate neutrino masses as well. One of the most
striking consequences is a large mixing between the electron and the Higgsino.
We show that this can still be in accord with data in some regions of the
parameter space and possibly falsified in future experiments.Comment: 30 pages, 1 figure. Revised version. To appear in JHE
Computer simulation of breast reduction surgery
Background: Plastic surgery of the breast, particularly breast reduction, is considered difficult. It can become a challenge for a less experienced surgeon to understand
exactly what to do when facing a particular type of breast
and how to avoid unsatisfactory results.
Methods: The goal of this study was to create a computer
model of the breast that provides a basis for the simulation
of breast surgery, particularly breast reduction. The
reconstruction of elastic parameters is based on observations of the breast with the patient in different positions.
Results: It is shown that several measurements with the
patient in different positions allow one to choose the
parameters of the model and determine the elastic coefficients of the breast and the skin. The geometry of the breast before and after surgery is simulated. A qualitative study of the incision parameters’ influence on the final geometry of the breast is presented.
Conclusion: The developed methodology and software
allow one to estimate the form of the breast after the surgery by knowing its form before surgery and taking into
consideration the parameters of incision applied by the
surgeon at the time of surgery. The described approach can be used for the qualitative and quantitative study of breast reduction surgery with a satisfactory result.
Level of Evidence: V (This journal requires that authors
assign a level of evidence to each article. For a full
description of these Evidence-Based Medicine ratings,
please refer to the Table of Contents or the online
Instructions to Authors http://www.springer.com/00266.
Neutrino Mass and from a Mini-Seesaw
The recently proposed "mini-seesaw mechanism" combines naturally suppressed
Dirac and Majorana masses to achieve light Standard Model neutrinos via a
low-scale seesaw. A key feature of this approach is the presence of multiple
light (order GeV) sterile-neutrinos that mix with the Standard Model. In this
work we study the bounds on these light sterile-neutrinos from processes like
\mu ---> e + \gamma, invisible Z-decays, and neutrinoless double beta-decay. We
show that viable parameter space exists and that, interestingly, key
observables can lie just below current experimental sensitivities. In
particular, a motivated region of parameter space predicts a value of BR(\mu
---> e + \gamma) within the range to be probed by MEG.Comment: 1+26 pages, 7 figures. v2 JHEP version (typo's fixed, minor change to
presentation, results unchanged
Spontaneous R-Parity Violation, Flavor Symmetry and Tribimaximal Mixing
We explore the possibility of spontaneous R parity violation in the context
of flavor symmetry. Our model contains singlet matter chiral superfields which are arranged as triplet of
and as well as few additional Higgs chiral superfields which are singlet
under MSSM gauge group and belong to triplet and singlet representation under
the flavor symmetry. R parity is broken spontaneously by the vacuum
expectation values of the different sneutrino fields and hence we have
neutrino-neutralino as well as neutrino-MSSM gauge singlet higgsino mixings in
our model, in addition to the standard model neutrino- gauge singlet neutrino,
gaugino-higgsino and higgsino-higgsino mixings. Because all of these mixings we
have an extended neutral fermion mass matrix. We explore the low energy
neutrino mass matrix for our model and point out that with some specific
constraints between the sneutrino vacuum expectation values as well as the MSSM
gauge singlet Higgs vacuum expectation values, the low energy neutrino mass
matrix will lead to a tribimaximal mixing matrix. We also analyze the potential
minimization for our model and show that one can realize a higher vacuum
expectation value of the singlet
sneutrino fields even when the other sneutrino vacuum expectation values are
extremely small or even zero.Comment: 18 page
Azimuthal anisotropy and correlations at large transverse momenta in and Au+Au collisions at = 200 GeV
Results on high transverse momentum charged particle emission with respect to
the reaction plane are presented for Au+Au collisions at =
200 GeV. Two- and four-particle correlations results are presented as well as a
comparison of azimuthal correlations in Au+Au collisions to those in at
the same energy. Elliptic anisotropy, , is found to reach its maximum at
GeV/c, then decrease slowly and remain significant up to
-- 10 GeV/c. Stronger suppression is found in the back-to-back
high- particle correlations for particles emitted out-of-plane compared to
those emitted in-plane. The centrality dependence of at intermediate
is compared to simple models based on jet quenching.Comment: 4 figures. Published version as PRL 93, 252301 (2004
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