2,699 research outputs found
Theories of Non-Experiments in Coherent Decays of Neutral Mesons
Many theoretical calculations of subtle coherent effects in quantum mechanics
do not carefully consider the interface between their calculations and
experiment. Calculations for gedanken experiments using initial states not
satisfied in realistic experiments give results requiring interpretation.
Confusion and ambiguities frequently arise. Calculations for time-dependent
mixing oscillations describe non-experiments. Physical experiments describe
oscillations in space in the laboratory system resulting from interference
between waves having the same energy and time dependence; different
momenta and space dependence. Time-dependent oscillations are not observed.Comment: 8 page
What is coherent in neutrino oscillations
Simple rigorous quantum mechanics with no hand waving nor loopholes clarifies
the confusion between three contradictory descriptions of neutrino
oscillations: (1)The time oscillations shown in standard textbooks produced by
neutrino eigenstates with different masses and different energies. (2) That
time oscillations and interference between states having different energies
cannot be observed in realistic experiments. (3) That interference between
different neutrino mass eigenstates is not observable in "missing mass"
experiments where information determining the neutrino mass is available from
other particles measured in production or detection vertices.
Quantum-mechanical ignorance of the neutrino momentum is rigorously shown to be
imposed by all realistic detectors and to produce coherence between amplitudes
from neutrino states with the same energy and different masses. Conditions are
precisely formulated for the loss of coherence when mass eigenstate wave
packets moving with different velocities separate. The example of Bragg
scattering shows how quantum-mechanically imposed ignorance produces coherence.Comment: 13 pages, Abstract and text of original contribution completely
revise
Systematics of Large Axial Vector Meson Production in Heavy Flavor Weak Decays
Branching ratios observed for and B decays to final states
are comparable to those for corresponding decays to
and and much larger than those for all other
decays. Implications are discussed of a "vector-dominance model" in which a
is produced and immediately turns into an axial vector, vector or pseudoscalar
meson. Data for decays to all such final states are shown to have large
branching ratios and satisfy universality relations. Upper limits on small
strong phase differences between amplitudes relevant to CP violation models are
obtained from analysis of the predicted and observed suppression of
decays into neutral final states , and . .
Branching ratios of are predicted for the as yet unobserved
presence of the charmed-strange axial vector in B decays.Comment: 14 page
Puzzles in Hyperon, Charm and Beauty Physics
Puzzles awaiting better experiments and better theory include: (1) the
contradiction between good and bad SU(3) baryon wave functions in fitting
Cabibbo theory for hyperon decays, strangeness suppression in the sea and the
violation of the Gottfried Sum rule - no model fits all; (2) Anomalously
enhanced Cabibbo-suppressed decays; (3) anomalously
enhanced and suppressed decays; (4) the OZI rule in weak
decays; (5) Vector dominance () in weak
decays (6) Puzzles in doubly-cabibbo-suppressed charm decays.(7) Problems in
obtaining spin structure from polarization measurements of produced
's.Comment: 5 page
How to Use Weak Decays in Analyses of Data on Nucleon Spin Structure Functions
The use of weak decays to determine proton spin structure is examined in view
of possible violations of the Bjorken and Gottfried Sum rules, flavor symmetry
breaking and flavor asymmetry in the sea. The use of the neutron decay is found
to be unaffected by all these. A method for including these effects in analyses
of hyperon decays shows that a flavor-asymmetric sea produced by SU(3) symmetry
breaking has only a small effect on results for the total spin carried by
quarks. However the strange quark contribution cannot be reliably obtained from
charged lepton scattering and weak decay data alone, and requires additional
model-dependent input relating nucleon and hyperon wave functions.Comment: 10 pages, Weizmann Report WIS-94/24/May-PH, Tel Aviv Report TAUP
2165-9
New Quark Relations for Hadron Masses and Magnetic Moments - A Challenge for Explanation from QCD
Prompted by the recent surprising results in QCD spectroscopy, we extend the
treatment of the constituent quark model showing that mass differences and
ratios have the same values when obtained from mesons and baryons. We obtain
several new successful relations involving hadrons containing two and three
strange quarks and hadrons containing heavy quarks and give a new prediction
regarding spin splitting between doubly charmed baryons. We provide numerical
evidence for an effective supersymmetry between mesons and baryons related by
replacing a light antiquark by a light diquark. We also obtain new relations
between quark magnetic moments and hadron masses. Limits of validity of this
approach and disagreements with experiment in properties of the Sigma and Xi
baryons are discussed as possible clues to a derivation from QCD.Comment: Presentation improved, references added, typos correcte
Theoretical Summary of the HADRON99 conference
The Constituent Quark Model has provided a remarkable description of the
experimentally observed hadron spectrum but still has no firm theoretical
basis. Attempts to provide a QCD justification discussed at Hadron99 include
QCD Sum Rules, instantons, relativistic potential models and the lattice.
Phenomenological analyses to clarify outstanding problems like the nature of
the scalar and pseudoscalar mesons and the low branching ratio for were presented. New experimental puzzles include the observation of
.Comment: 10 pages, espcrc1.st
Application of M\"ossbauer-Type Sum Rules for Meson Decays
Sum rules originally derived for the M\"ossbauer Effect are applied to weak
semileptonic B decays. The sum rules follow from assuming that the decay by
electroweak boson emission of an unstable nucleus or heavy quark in a bound
system is described by a pointlike coupling to a current which acts only on the
decaying object, that the Hamiltonian of the bound state depends on the
momentum of the decaying object only in the kinetic energy and that the boson
has no final state interactions. The decay rate and the first and second
moments of the boson energy spectrum for fixed momentum transfer are shown to
be the same as for a noninteracting gas of such unstable objects with a
momentum distribution the same as that of the bound state. B meson semileptonic
decays are shown to be dominated by the lowest-lying states in the charmed
meson spectrum.Comment: 9 page
FSI Rescattering in Decays via States with and
New results going beyond those obtained from isospin and flavor symmetry and
subject to clear experimental tests are obtained for effects of FSI in
decays to charmless strange final states containing neutral flavor-mixed mesons
like , , and . The most general strong-interaction
diagrams containing arbitrary numbers of quarks and gluons are included with
the assumptions that any pair created by gluons must be a flavor
singlet, and that there are no hairpin diagrams in which a final meson contains
a pair from the same gluon vertex. The smallness of
suggests that it might have a large CP violation. A sum rule is derived to test
whether the large requires the addition of an additional glueball
or charm admixture. Further analysis from decay systematics supports this
picture of FSI and raises questions about charm admixture in the
Penguins, Trees and Final State Interactions in B Decays in Broken SU3
The availability of data on decays to strange quasi-two-body final
states, either with or without charmonium opens new possibilities for
understanding different contributions of weak diagrams and in particular the
relative contributions of tree and penguin diagrams. Corresponding and
decays to charge conjugate final states are equal in the SU(3) symmetry
limit and the dominant SU(3) breaking mechanism is given by ratios of CKM
matrix elements. Final State Interactions effects should be small, because
strong interactions conserve and should tend to cancel in ratios between
charge conjugate states. Particularly interesting implications of decays into
final states containing and are discussed.Comment: special macro - phyzz
- …