5,526 research outputs found
Non-leptonic B-decays, CP violation & the UT
We study the implication of the time-dependent CP asymmetry in
decays on the extraction of weak phases taking into account
the precise measurement of , obtained from the ``gold-plated''mode
. Predictions and uncertainties for the hadronic parameters
are investigated in QCD factorization. Furthermore, independent theoretical and
experimental tests of the factorization framework are briefly discussed.
Finally, a model-independent bound on the unitarity triangle from CP violation
in and is derived.Comment: 4 pages; 4 figures (requires epsfig, psfrag); To appear in the
proceedings of the 11th International Conference on Quantum Chromodynamics
(QCD 04), Montpellier, France, 5--10th July 200
Large electroweak penguin contribution in B -> K pi and pi pi decay modes
We discuss about a possibility of large electroweak penguin contribution in B
-> K pi and pi pi from recent experimental data. The experimental data may be
suggesting that there are some discrepancies between the data and theoretical
estimation in the branching ratios of them. In B -> K pi decays, to explain it,
a large electroweak penguin contribution and large strong phase differences
seem to be needed. The contributions should appear also in B -> pi pi. We show,
as an example, a solution to solve the discrepancies in both B -> K pi and B ->
pi pi. However the magnitude of the parameters and the strong phase estimated
from experimental data are quite large compared with the theoretical
estimations. It may be suggesting some new physics effects are including in
these processes. We will have to discuss about the dependence of the new
physics. To explain both modes at once, we may need large electroweak penguin
contribution with new weak phases and some SU(3) breaking effects by new
physics in both QCD and electroweak penguin type processes.Comment: 23 pages, 9 figure
On measuring alpha in B(t)-> rho^\pm pi^\mp
Defining a most economical parametrization of time-dependent B-> rho^\pm
pi^\mp decays, including a measurable phase alpha_{eff} which equals the weak
phase alpha in the limit of vanishing penguin amplitudes, we propose two ways
for determining alpha in this processes. We explain the limitation of one
method, assuming only that two relevant tree amplitudes factorize and that
their relative strong phase, delta_t, is negligible. The other method, based on
broken flavor SU(3), permits a determination of alpha in B^0-> rho^\pm pi^\mp
in an overconstrained system using also rate measurements of B^{0,+}-> K^* pi
and B^{0,+}->rho K. Current data are shown to restrict two ratios of penguin
and tree amplitudes, r_\pm, to a narrow range around 0.2, and to imply an upper
bound |alpha_{eff} - alpha| < 15 degrees. Assuming that delta_t is much smaller
than 90 degrees, we find alpha =(93\pm 16) degrees and (102 \pm 20) degrees
using BABAR and BELLE results for B(t)-> rho^\pm pi^mp. Avoiding this
assumption for completeness, we demonstrate the reduction of discrete
ambiguities in alpha with increased statistics, and show that SU(3) breaking
effects are effectively second order in r_\pm.Comment: 23 pages, 2 figures, data and references updated, to be published in
Phys. Rev.
Surface and Subsurface Properties of Aquatic Ecosystems
تعد الطبقة الدقيقة السطحيةSurface Micro Layer (SML) حداً فاصلاً بين سطح الماء والهواء ولها خصائص فيزيائية وكيميائية وبايولوجية تختلف عن الطبقة تحت السطحية Sub Surface Layer (SSL)، نظرًا لكونها مكانًا فريدًا بين الهواء والماء، فقد ظلت SML في زاوية بحثية متميزة، ولهذه الطبقة الدقيقة السطحية القدرة على تراكم المركبات الكيميائية العضوية وخاصة البروتينات والكاربوهيدرات والدهون. إن وجود مثل المواد العضوية الغنية بالطاقة في الطبقة الدقيقة السطحية يخلق حالة مميزة لتراكم وتطوير البكتيريا الهوائية وبشكل رئيس لبكتيريا متغايرة التغذية التي تكوّن البكتيريا النيوستونيةNeostonic Bacteria .The surface microlayer (SML) is the dividing border between the air and water surface. It has physical, chemical and biological properties which are distinctly from subsurface layer (SSL) waters. As its unique place between the air- water, the SML has remained in a distinct research corner. Surface microlayer is characterized by the capacity to accumulate of organic chemical compounds specially proteins, carbohydrates and lipid. The presence of such as energy-rich organic matters in the surface microlayer creates distinct condition for the accumulation and development of aerobic bacteria mainly heterotrophic bacteria forming bacterio-neusto
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Computational Investigations of Coordination Bonding and Adsorbate Properties in Metal-Organic Frameworks
In this thesis, I have used computational methods to the study of flexibility in metal-organic frameworks (MOFs) and the behavior of adsorbed gases and liquids in MOFs. Among nanoporous materials, MOFs are of particular interest for adsorption-based applications for reasons that include (1) their huge chemical space, which raises the possibility of tuning them for specific industrial processes and (2) the ability of the under-coordinated metals present in some MOFs to endow their respective materials with impressive adsorbate binding energies.Chapters 2 and 4 relate to analogs of a series of MOFs with under-coordinated metals (the M-MOF-74 series). In Chapter 2, I report the discovery of a novel argon adsorbate-induced deformation pattern for this framework series. This result was arrived at using a flexible framework model, and is presented as an explanation for an intriguing signal observed in experimental small-angle X-ray scattering profiles upon argon adsorption. This hypothesis is supported by a complementary investigation of an alternative explanation for the X-ray signal, in which argon atoms are proposed to adsorb at different densities in adjacent pores.In Chapter 3, I studied the dynamics of adsorbed xylene isomers in MOF-5. I compare the translational and rotational motion of the xylene isomers, and explain the differences based on molecular geometries. The most rod-like molecule, para-xylene, is more rotationally constricted in the pore due to its intermolecular interactions with the aromatic group of the MOF linker. This finding has implications for the rational design of MOFs, as a process that can take advantage of the MOF-induced variations in xylene isomer dynamics could be used for lucrative liquid-phase xylene separations.In Chapter 4, I present a method for parameterizing the type of flexible framework model used in Chapter 2 from ab initio quantum chemistry calculations. The goal of this work is to facilitate the rapid development of flexible, versatile MOF models that can capture changes in the coordination bonding of metals in MOFs. This type of model can be used to study structural transitions and may be extended to study MOF formation. We demonstrated that our approach yields models for the M-MOF-74 series that are stable and have simulated structural properties in good agreement with quantum chemistry calculations
Exploring the Unitarity Triangle through CP violation observables in
We discuss the determination of the CKM parameters from the forthcoming
violation observables in decays. Combining the information on
mixing induced CP violation in , with the
precision observable and the -- mixing phase
, we propose a determination of the unitarity triangle . Computing the penguin parameters within QCD
factorization yield precise determination of , reflected
by a weak dependence on the which is shown as a second order effect.
The impact of the direct CP violation observable on the penguin
parameters are investigated and a lower bound on is extracted. We also
discuss the effect of the -- new physics mixing phase on
the penguin parameters and . Using the SU(3)-flavour
symmetry argument and the current -factories data provided by the modes, we complement the CP-violating
observables in a variety of ways, in particular we find that .
Finally we analyze systematically the SU(3)-symmetry breaking factor within QCD
factorization.Comment: 22 pages, 6 figures, typos corrected, reference and some remarks
adde
Obtaining CKM Phase Information from B Penguin Decays
We discuss a method for extracting CP phases from pairs of B decays which are
related by flavor SU(3). One decay (B0 -> M1 M2) receives a significant bbar ->
dbar penguin contribution. The second (B' -> M1' M2') has a significant bbar ->
sbar penguin contribution, but is dominated by a single amplitude. CP phase
information is obtained using the fact that the B' -> M1' M2' amplitude is
related by SU(3) to a piece of the B0 -> M1 M2 amplitude. The leading-order
SU(3)-breaking effect (~25%) responsible for the main theoretical error can be
removed. For some decay pairs, it can be written in terms of known decay
constants. In other cases, it involves a ratio of form factors. However, this
form-factor ratio can either be measured experimentally, or eliminated by
considering a double ratio of amplitudes. In all cases, one is left only with a
second-order effect, ~5%. We find twelve pairs of B decays to which this method
can be applied. Depending on the decay pair, we estimate the total theoretical
error in relating the B' -> M1' M2' and B0 -> M1 M2 amplitudes to be between 5%
and 15%. The most promising decay pairs are Bd -> pi+ pi- and Bu+ -> K0 pi+,
and Bd -> D+ D- and Bd -> Ds+ D- or Bu+ -> Ds+ D0bar.Comment: 38 pages, JHEP format, no figures. Comments added to text regarding
most promising decay pairs; references added; conclusions unchange
Charm production in nonresonant e(+)e(-) annihilations at √s =10.55 GeV
This is the publisher's version also available electronically from http://journals.aps.org/prd/abstract/10.1103/PhysRevD.37.1719We report results on the differential and total cross sections for inclusive production of the charmed particles D*+, D*(0), D(0), D(+), D(s), and Λc in e(+)e(-) annihilations at √s=10.55 GeV. Widely used quark fragmentation models are discussed and compared with the measured charmed-particle momentum distributions. This comparison, as well as that with measurements at other center-of-mass energies, shows the need to take QCD corrections into account and their importance for a correct interpretation of the model parameters. The observed rate of D(0) and D(+) production is compared to the expected total charm production cross section. We measure the probability of a charmed meson being produced as a vector meson and the D*(+) decay branching fraction into D(0)π+
Anatomy of Prominent B and K Decays and Signatures of CP-Violating New Physics in the Electroweak Penguin Sector
The recent observation of B_d -> pi^0 pi^0 at the B factories with a
surprisingly large branching ratio represents a challenge for theory, and
complements the amazingly small B_d -> pi^+ pi^- rate. We point out that all
puzzling B -> pi pi features can be accommodated in the Standard Model (SM)
through non-factorizable hadronic interference effects, extract the relevant
parameters, and predict the CP asymmetries of B_d -> pi^0 pi^0. Using then
SU(3) flavour-symmetry and plausible dynamical assumptions, we fix the hadronic
B -> pi K parameters through their B -> pi pi counterparts, and determine the
CKM angle gamma, with a result in remarkable accordance with the usual fits for
the unitarity triangle. We may then analyse the B -> pi K system in the SM,
where we find agreement with the experimental picture, with the exception of
those observables that are significantly affected by electroweak (EW) penguins,
thereby suggesting new physics (NP) in this sector. Indeed, a moderate
enhancement of these topologies and a large CP-violating NP phase allow us to
describe any currently observed feature of the B -> pi K modes, and to predict
the CP-violating B_d -> pi^0 K_S observables. If we then restrict ourselves to
a specific scenario where NP enters only through Z^0 penguins, we obtain a link
to rare K and B decays, where the most spectacular NP effects are an
enhancement of the K_L -> pi^0 nu nu_bar rate by one order of magnitude with
BR(K_L -> pi^0 nu nu_bar) ~ 4 BR(K^+ -> pi^+ nu nu_bar), BR(K_L -> pi^0 e^+
e^-) = O(10^-10), (sin 2beta)_{pi nu nu_bar} < 0, and a large forward-backward
CP asymmetry in B_d -> K^* mu^+ mu^-. We address also epsilon'/epsilon and
other prominent decays, including B -> phi K and B -> J/psi K modes.Comment: 78 pages, 12 figures, LaTe
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