338 research outputs found
The root of the universal tree and the origin of eukaryotes based on elongation factor phylogeny
The genes for the protein synthesis elongation factors Tu (EF-Tu) and G (EF-G) are the products of an ancient gene duplication, which appears to predate the divergence of all extant organismal lineages. Thus, it should be possible to root a universal phylogeny based on either protein using the second protein as an outgroup. This approach was originally taken independently with two separate gene duplication pairs, (i) the regulatory and catalytic subunits of the proton ATPases and (ii) the protein synthesis elongation factors EF-Tu and EF-G. Questions about the orthology of the ATPase genes have obscured the former results, and the elongation factor data have been criticized for inadequate taxonomic representation and alignment errors. We have expanded the latter analysis using a broad representation of taxa from all three domains of life. All phylogenetic methods used strongly place the root of the universal tree between two highly distinct groups, the archaeons/eukaryotes and the eubacteria. We also find that a combined data set of EF-Tu and EF-G sequences favors placement of the eukaryotes within the Archaea, as the sister group to the Crenarchaeota. This relationship is supported by bootstrap values of 60-89% with various distance and maximum likelihood methods, while unweighted parsimony gives 58% support for archaeal monophyly
CP Measurement in Quantum Teleportation of Neutral Mesons
Quantum teleportation using neutral pseudoscalar mesons shows novel
connections between particle physics and quantum information. The projection
basis, which is crucial in the teleportation process, is determined by the
conservation laws of particle physics, and is different from the Bell basis, as
in the usual case. Here we show that one can verify the teleportation process
by CP measurement. This method significantly simplifies the high energy quantum
teleportation protocol. Especially, it is rigorous, and is independent of
whether CP is violated in weak decays. This method can also be applied to
general verification of Einstein-Podolsky-Rosen correlations in particle
physics.Comment: 7 page
A Parton Model for Inclusive Semileptonic B Meson Decays
The parton model for semileptonic B meson decays is studied with special
attention to the decay distributions. We find that the spectra show dramatic
variations when we introduce cuts on the hadronic energy or invariant mass of
hadrons. Results for both and decays are
presented. The detailed spectra may help to separate the two types of decays.Comment: 9 pages, DO-TH 93/29, OHSTPY-HEP-T-93-011, September 199
CP Violation and Strong Phases from Penguins in Decays
We calculate direct CP-violating observables in charged decays
arising from the interference of amplitudes with different strong and CKM
phases. The perturbative strong phases develop at order from
absorptive parts of one-loop matrix elements of the next-to-leading logarithm
corrected effective Hamiltonian. CPT constraints are maintained. Based on this
model, we find that partial rate asymmetries between charge conjugate
decays can be as high as 15-30\% for certain channels with branching ratios in
the range. The small values of the coefficients of angular
correlations, which we calculated previously to be of order , are not
significantly degraded by the strong phases. The charge asymmetries of rates
and angular distributions would provide unambiguous evidence for direct CP
violation.Comment: 24 pages, 3 figures (upon request), LaTeX, preprint DESY 93-19
The Mass Definition in Hqet and a New Determination of V
Positive powers of the mass parameter in a physical quantity calculated with
the help of heavy quark effective theory originate from a Wilson coefficient in
the matching of QCD and HQET Green function. We show that this mass parameter
enters the calculation as a well--defined running current mass. We further
argue that the recently found ill--definition of the pole mass, which is the
natural expansion parameter of HQET, does not affect a phenomenological
analysis which uses truncated perturbative series. We reanalyse inclusive
semileptonic decays of heavy mesons and obtain the quark mass
where the error
is almost entirely due to scale--uncertainties. We also obtain
and
where the errors come
from the uncertainty in the kinetic energy of the heavy quark inside the meson,
in the experimental branching ratios, in QCD input parameters, and
scale--uncertainties.Comment: 21 p., 5 figs, all style files incl., TUM-T31-56/R (Sec. 2 revised,
phenomenological results unchanged
Probing for the Charm Content of and Mesons
A slow bump exists in the inclusive spectrum,
while the softness of spectrum in decay
is in strong contrast with expectations from color octet mechanism. We propose
{\it intrinsic} charm as the explanation:the former is due to ,with three charm quarks in the final state; the latter is just a small
fraction of "jet" events, where the
slow moving system evolves into pairs. Experimental search
for these phenomena at B Factories and the Tevatron is strongly urged, as the
implications go beyond QCD.Comment: 4 pages, REVTEX, 10 eps figures included. Major revision with more
discussions on the rescattering background, and a reappraisal of the
Upsilon(1S) decay in the presence of intrinsic charm, leading to a change in
Titl
A Phenomenological Analysis of Heavy Hadron Lifetimes
A phenomenological analysis of lifetimes of bottom and charmed hadrons within
the framework of the heavy quark expansion is performed. The baryon matrix
element is evaluated using the bag model and the nonrelativistic quark model.
We find that bottom-baryon lifetimes follow the pattern
.
However, neither the lifetime ratio nor the
absolute decay rates of the baryon and mesons can be explained.
One way of solving both difficulties is to allow the presence of linear
corrections by scaling the inclusive nonleptonic width with the fifth power of
the hadron mass rather than the heavy quark mass . The hierarchy
of bottom baryon lifetimes is dramatically modified to
: The
longest-lived among bottom baryons in the OPE prescription now
becomes shortest-lived. The replacement of by in nonleptonic
widths is natural and justified in the PQCD-based factorization approach
formulated in terms of hadron-level kinematics. For inclusive charmed baryon
decays, we argue that since the heavy quark expansion does not converge, local
duality cannot be tested in this case. We show that while the ansatz of
substituting the heavy quark mass by the hadron mass provides a much better
description of the charmed-baryon lifetime {\it ratios}, it appears unnatural
and unpredictive for describing the {\it absolute} inclusive decay rates of
charmed baryons, contrary to the bottom case.Comment: 35 pages, to appear in Phys. Rev. The CDF result on the lifetime
ratio of Lambda_b and B_d is discusse
Weak Phase and Strong Phase from CP Averaged and Decays
Assuming SU(3) symmetry for the strong phases in the four decay modes
B\rarrow \pi^-\pi^+, \pi^0 \pi^+, \pi^- K^+, \pi^- \bar{K}^0 and ignoring the
relative small electroweak penguin effects in those decays, the weak phase
and the strong phase can be determined in a model independent
way by the CP-averaged branching ratios of the four decay modes. It appears
that the current experimental data for and decays prefer
a negative value of . By combining with the other
constraints from , mixings and indirect
CP-violating parameter within the standard model, two favorable
solutions for the phases and are found to lie in the region:
35^{\circ}\alt\gamma\alt 62^{\circ} and 106^{\circ}\alt \delta \alt
180^{\circ} or 86^{\circ}\alt\gamma\alt 151^{\circ} and
0^{\circ}\alt\delta\alt 75^{\circ} within 1 standard deviation. It
is noted that if allowing the standard deviation of the data to be more than
1, the two solutions could approach to one solution with a much larger
region for the phases and . Direct CP asymme try
in B\rarrow \pi^-K^+ decay can be as large as
the present experimental upper bound. Direct CP asymmetry
in B\rarrow \pi^-\pi^+ decay can reach up to
about 40% at 1 level.Comment: 14 Pages, ReVTeX, 5 figures, one figure (Fig.3) is correcte
Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS
We present the results of a search for new, heavy particles that decay at a
significant distance from their production point into a final state containing
charged hadrons in association with a high-momentum muon. The search is
conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV
and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS
detector operating at the Large Hadron Collider. Production of such particles
is expected in various scenarios of physics beyond the standard model. We
observe no signal and place limits on the production cross-section of
supersymmetric particles in an R-parity-violating scenario as a function of the
neutralino lifetime. Limits are presented for different squark and neutralino
masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final
version to appear in Physics Letters
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