3,151 research outputs found
b --> s g g decay in the two and three Higgs doublet models with CP violating effects
We study the decay width and CP-asymmetry of the inclusive process b--> s g g
(g denotes gluon) in the three and two Higgs doublet models with complex Yukawa
couplings. We analyse the dependencies of the differential decay width and
CP-asymmetry to the s- quark energy E_s and CP violating parameter \theta. We
observe that there exist a considerable enhancement in the decay width and CP
asymmetry is at the order of 10^{-2}. Further, it is possible to predict the
sign of C_7^{eff} using the CP asymmetry.Comment: 15 pages, 7 Figures (required epsf style
Calix[n]arene derivatives for gas storage
Abstract only availableThe calix[n]arenes are versatile inclusion compounds (Scheme 1) comprise of cyclic, polyphenolic compounds that can be tailored synthetically by altering X, Y, R and n. In solid state, we found simple calixarenes are quite interesting for example separation of hydrogen from mixture of gases so our attention turned into the closely related calixarenes for sorption studies. With this little back ground on calixarenes and their uses in solid state, we designed and synthesized tert-butylsulfonylcalix[4]arene and Tetra-p-tert-butyl-tetramethoxysulfonylcalix[4]arene from tert-butylthiacalix[4]arene by oxidizing in the presence H2O2 or NaBO3 in exceptional yield. Furthermore, asymmetric bridging of two calix[4]arene molecules to form a calixarene tubes with a larger and easily accessible cavity was also attempted to synthesize. Finally, H1NMR spectral and X- ray crystallographic modeling studies was done to reveal the conformational characteristics of the synthesized compounds.Stevens' Chemistry Progra
Improved Methods for Observing CP Violation in B+/- --> K+/- D0 and Measuring the CKM Phase gamma
Various methods are discussed for obtaining the CKM angle gamma through the
interference of the charged B-meson decay channels B- -> K- D0 and B- -> K-
D0-bar where the D0 and D0-bar decay to common final states. It is found that
choosing final states which are not CP eigenstates can lead to large direct CP
violation which can give significant bounds on gamma without any theoretical
assumptions. If two or more modes are studied, gamma may be extracted with a
precision on the order of +/-15 degrees given about 10^8 B-mesons. We also
discuss the case of three body decays of the D0 where additional information
may be obtained from the distribution of the D0 decay products and consider the
impact of D-D-bar oscillations.Comment: 51 pages 8 figures, typo in equation 33 correcte
Host-guest complexes to molecular encapsulation of hydrogen
Abstract only availableScience has always been about man learning from and attempting to mimic nature. In supramolecular chemistry this possibility is evident due to particularly interesting architectures of natural shell-like containers such as viruses and ferritin. One class of compounds studied for this purpose are calixarenes. Their typical cone structure allows them to sequester a variety of other molecules making it useful to form host-guest complexes or supramolecules. In such complexes, the host is a large molecule, in our case a calixarene, possessing a sizeable central cavity and the guest can be a monoatomic cation, a simple inorganic anion or a more sophisticated molecule such as a hormone, pheromone or neuro transmitter. In today's supramolecular chemistry field these compounds can be used for catalysis, biocatalysis, stabilization of reactive intermediates, drug transport, and the now emerging field of storage, processing and release of gases. The synthesis of this molecular capsule able to incorporate a guest begins with the methylation of the phenols present on the lower rim of calix[4]arene, an aldehyde was introduced along the upper ring followed by an oxidation to a carboxylic acid yielding tetracarboxycalix[4]arene. The tetrasubstituted calix[4]arene was crystallized from methanol and water to yield pale yellow crystals that were analyzed by X-ray. In this particular case, the objective was to incorporate gaseous hydrogen as the guest, which will be studied in due course. Further applications of this host-guest system could be the purification and storage of hydrogen for use in fuel cell. The nanoscale systems are a leading development strategy in many research areas. General advantages are the ability of saving time, space, costs, and materials for that reason supramolecular chemistry open a door to a new source of inspiration in the science world.Stevens' Chemistry Progra
CP Nonconservation in at the Tevatron
The reaction is found to be rather rich in exhibiting
several different types of CP asymmetries. The spin of the top quark plays an
important role. Asymmetries are related to form factors arising from radiative
corrections of the production vertex due to non-standard physics. As
illustrations, effects are studied in two Higgs Doublet Models and in
Supersymmetric Models; asymmetries up to a few percent may be possible.Comment: 14 pages, 3 figures. Note: replaced due to minor problems that
appeared on some postscript previewers. No change in conten
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Responsiveness of PROMIS® to change in chronic obstructive pulmonary disease.
BackgroundChronic obstructive pulmonary disease (COPD) is a progressive chronic disease characterized by airflow obstruction that leads to shortness of breath and substantial negative impacts on health-related quality of life (HRQL). The course of COPD includes periodic acute exacerbations that require changes in treatment and/or hospitalizations. This study was designed to examine the responsiveness of Patient-Reported Outcomes Measurement Information System® (PROMIS®) measures to changes associated with COPD exacerbation recovery.MethodsA longitudinal analysis using mixed-effects models was conducted of people who were enrolled while stable (n = 100) and those who experienced an acute exacerbation (n = 85). PROMIS (physical function, pain interference, pain behavior, fatigue, anxiety, depression, anger, social roles, discretionary social activities, Global Health, dyspnea severity and dyspnea functional limitations) and COPD-targeted HRQL measures were completed at baseline and at 12 weeks.ResultsWe administered PROMIS measures using computer adaptive testing (CAT), followed by administration of any remaining short form (SF) items that had not yet been administered by CAT. Examination of the difference between group differences from baseline to 12 weeks in the stable and exacerbation groups revealed that the exacerbation group changed (improved) significantly more than the stable group in anxiety (p < .001 to p < .01; f2 effect size [ES] = 0.023/0.021), fatigue (p < .0001; ES = 0.036/0.047) and social roles (p < .001 to p < .05; ES = 0.035/0.024). All effect sizes were small in magnitude and smaller than hypothesized. Depression was also statistically significant (p < .05, SF only) but the ES was trivial. For all other PROMIS domains, the differences were not significant and ES were trivial.ConclusionsThis longitudinal study provides some support for the validity of the PROMIS fatigue, anxiety, and social roles domains in COPD, but further evaluation of responsiveness is warranted
B_s ---> \gamma \gamma decay in the model III and 3HDM(O_2) with CP violating effects
We analyse the CP asymmetry for B_{s} -->\gamma\gamma in the two Higgs
doublet model with tree level flavor changing currents (model III) and three
Higgs doublet model with O_2 symmetry in the Higgs sector, including O_{7} type
long distance effects. Further, we study the dependencies of the branching
ratio Br(B_{s} --> \gamma\gamma)$ and the ratio of CP-even and CP-odd amplitude
squares, R=|A^{+}|^2/|A^{-}|^2, on the CP parameter sin \theta. We found that,
there is a weak CP asymmetry, at the order of 10^{-4}. Besides, the branching
ratio Br(B_{s} --> \gamma\gamma), and also R ratio, is not sensitive to the CP
parameter for |\frac{\bar{\xi}^{U}_{N,tt}}{\bar{\xi}^{D}_{N,bb}}|<1.Comment: 17 pages, 11 figure
Implications of a W^+W^- (ZZ) - Higgs - t c-bar$ Interaction for e^+e^- -> t c-bar \nu_e \nu_e-bar, t c-bar e^+ e^-, t c-bar Z and for t -> cW^+W^-, cZZ in a Two Higgs Doublet Model
The Standard Model with one extra Higgs doublet may give rise to enhanced
TREE-LEVEL flavor-changing-scalar coupling of a neutral Higgs to a pair of
top-charm quarks. This coupling may drive a large TREE-LEVEL effective
W^+W^-(ZZ) - Higgs - t c-bar interaction. As a result we find that the
reactions e^+e^- -> t c-bar \nu_e \nu_e-bar, t c-bar e^+ e^-, t c-bar Z and the
two rare top decays t -> cW^+W^-, t -> cZZ become very sensitive probes of such
an effective interaction. The most promising ones, e^+e^- -> t c-bar \nu_e
\nu_e-bar, t c-bar e^+ e^-, may yield several hundreds and up to thousands of
such events at the Next Linear Collider with a center of mass energy of
\sqrt{s}=0.5 - 2 TeV if the mass of the lightest neutral Higgs is a few hundred
GeV. The rare decays t -> cW^+W^- and t -> cZZ may be accessible at the LHC if
the mass of the lightest neutral Higgs lies in the narrow window 150 GeV < m_h
< 200 GeV.Comment: 18 pages, plain latex, 12 figures embadded in the text using epsfi
Enhanced CP Violation with Modes and Extraction of the CKM Angle gamma
The Gronau-London-Wyler (GLW) method extracts the CKM angle by
measuring decay rates involving mesons. Since that
method necessitates the interference between two amplitudes that are
significantly different in magnitude, the resulting asymmetries tend to be
small. CP violation can be greatly enhanced for decays to final states that are
common to both D^0 and and that are not CP eigenstates. In
particular, large asymmetries are possible for final states f such that is doubly Cabibbo suppressed while is Cabibbo allowed.
The measurement of interference effects in two such modes allows the extraction
of without prior knowledge of , which
may be difficult to determine due to backgrounds.Comment: 12 pages, LaTeX, no figure
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