1,610 research outputs found
Spin-Correlation Coefficients and Phase-Shift Analysis for p+He Elastic Scattering
Angular Distributions for the target spin-dependent observables A,
A, and A have been measured using polarized proton beams at
several energies between 2 and 6 MeV and a spin-exchange optical pumping
polarized He target. These measurements have been included in a global
phase-shift analysis following that of George and Knutson, who reported two
best-fit phase-shift solutions to the previous global p+He elastic
scattering database below 12 MeV. These new measurements, along with
measurements of cross-section and beam-analyzing power made over a similar
energy range by Fisher \textit{et al.}, allowed a single, unique solution to be
obtained. The new measurements and phase-shifts are compared with theoretical
calculations using realistic nucleon-nucleon potential models.Comment: Submitted to Phys. Rev.
Supersymmetric QCD flavor changing top quark decay
We present a detailed and complete calculation of the gluino and scalar
quarks contribution to the flavour-changing top quark decay into a charm quark
and a photon, gluon, or a Z boson within the minimal supersymmetric standard
model including flavour changing gluino-quarks-scalar quarks couplings in the
right-handed sector. We compare the results with the ones presented in an
earlier paper where we considered flavour changing couplings only in the
left-handed sector. We show that these new couplings have important
consequences leading to a large enhancement when the mixing of the scalar
partners of the left- and right-handed top quark is included. Furthermore CP
violation in the flavour changing top quark decay will occur when a SUSY phase
is taken into account.Comment: 14 pages, latex, 3 figure
Patterns in the Fermion Mixing Matrix, a bottom-up approach
We first obtain the most general and compact parametrization of the unitary
transformation diagonalizing any 3 by 3 hermitian matrix H, as a function of
its elements and eigenvalues. We then study a special class of fermion mass
matrices, defined by the requirement that all of the diagonalizing unitary
matrices (in the up, down, charged lepton and neutrino sectors) contain at
least one mixing angle much smaller than the other two. Our new parametrization
allows us to quickly extract information on the patterns and predictions
emerging from this scheme. In particular we find that the phase difference
between two elements of the two mass matrices (of the sector in question)
controls the generic size of one of the observable fermion mixing angles: i.e.
just fixing that particular phase difference will "predict" the generic value
of one of the mixing angles, irrespective of the value of anything else.Comment: 29 pages, 3 figures, references added, to appear in PR
Unraveling the Nature of Charge Excitations in LaCuO with Momentum-Resolved Cu -edge Resonant Inelastic X-ray Scattering
Results of model calculations using exact diagonalization reveal the orbital
character of states associated with different Raman loss peaks in Cu -edge
resonant inelastic X-ray scattering (RIXS) from LaCuO. The model
includes electronic orbitals necessary to highlight non-local Zhang-Rice
singlet, charge transfer and - excitations, as well as states with apical
oxygen 2 character. The dispersion of these excitations is discussed with
prospects for resonant final state wave-function mapping. A good agreement with
experiments emphasizes the substantial multi-orbital character of RIXS profiles
in the energy transfer range 1-6 eV.Comment: Original: 4.5 pages. Replaced: 4 pages and 4 figures with updated
content and reference
Transverse beam polarization and CP-violating triple-gauge-boson couplings in e+e- -> gamma Z
We show that an anomalous CP-violating gamma-gamma-Z vertex gives rise to a
novel asymmetry with transversely polarized electron and positron beams in the
process e+e- -> gamma Z. This asymmetry, which is odd under naive time
reversal, is proportional to the real part of the gamma-gamma-Z CP-violating
coupling. This is in contrast to the simple forward-backward asymmetry of the
gamma (or Z) with unpolarized or longitudinally polarized beams studied
earlier, which is even under naive time reversal, and is proportional to the
imaginary part. We estimate the sensitivity of future experiments to the
determination of CP-odd gamma-gamma-Z and gamma-Z-Z couplings using these
asymmetries and transversely polarized beams.Comment: 13 pages, latex, 7 figures included as postscrip
Weak dipole moment of in collisions with longitudinally polarized electrons
It is pointed out that certain CP-odd momentum correlations in the production
and subsequent decay of tau pairs in collisions get enhanced when the
is longitudinally polarized. Analytic expressions for these correlations
are obtained for the single-pion decay mode of when have
a ``weak" dipole form factor (WDFF) coupling to . For collisions
at the peak, a sensitivity of about 1-5\mbox{ cm} for
the WDFF can be reached using a {\em single} decay
channel, with 's likely to be available at the SLC at Stanford with
polarization of 62\%-75\%.Comment: 9 pages, Latex, PRL-TH-93/17 (Revised
[Colored solutions of Yang-Baxter equation from representations of U_{q}gl(2)]
We study the Hopf algebra structure and the highest weight representation of
a multiparameter version of . The commutation relations as well as
other Hopf algebra maps are explicitly given. We show that the multiparameter
universal matrix can be constructed directly as a quantum double
intertwiner, without using Reshetikhin's transformation. An interesting feature
automatically appears in the representation theory: it can be divided into two
types, one for generic , the other for being a root of unity. When
applying the representation theory to the multiparameter universal
matrix, the so called standard and nonstandard colored solutions of the Yang-Baxter equation is obtained.Comment: [14]pages, latex, no figure
Measurement of the electric dipole moment using longitudinal polarization of beams
Certain CP-odd momentum correlations in the production and subsequent decay
of pairs in collisions are enhanced significantly when the
and beams are longitudinally polarized. These may be used to probe
the real and imaginary parts of , the electric dipole moment of
the . Closed-form expressions for these ``vector correlations'' and the
standard deviation of the operators defining them due to standard model
interactions are presented for the two-body final states of decays. If
42\% average polarization of each beam is achieved, as proposed for the
tau-charm factories, with equal integrated luminosities for each sign of
polarization and a total yield of pairs, it is
possible to attain sensitivities for of , , cm respectively and for of , , cm respectively at the three operating center-of-mass energies of
3.67, 4.25 and 10.58 GeV. These bounds emerge when the effects of a posible
weak dipole form factor are negligible as is the case when it is of
the same order of magnitude as . Furthermore, in such a
polarization experiment where different polarizations are possible, a
model-independent disentangling of their individual effects is possible, and a
technique to achieve this is described. A strong longitudinal polarization
physics programme at the tau-charm factory appears warranted.Comment: 30 pages, latex, no figure
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