1,486 research outputs found
Isospin-breaking effects on alpha extracted in B --> pi pi, rho rho, rho pi
Isospin-breaking in B --> pi pi caused by pi^0-eta-eta' mixing is studied in
a model-independent way using flavor SU(3). Measured branching ratios for B^+
--> pi^+ pi^0, B^+ --> pi^+ eta^(') and B^0 --> pi^0 eta^(') imply an
uncertainty in alpha smaller than 1.4 degree. We find a negligible effect of
pi^0-eta-eta' mixing on alpha in B --> rho pi. Characterizing the effect of
rho^0-omega mixing in B --> rho rho and in B --> rho pi by the two-pion
invariant mass dependence, we point out a way of constraining this effect
experimentally or eliminating it altogether. We show that a model-independent
shift in alpha caused by electroweak penguin amplitudes in B --> pi pi and B
--> rho rho, \Delta alpha_{EWP}=1.5+- 0.3 degree, may be slightly different in
B --> rho pi. Other sources of isospin-breaking in these processes are briefly
discussed.Comment: 21 pages, very slight changes, same version as in Physical Review
Semi-inclusive hadronic B decays as null tests of the Standard Model
We propose a new set of observables that can be used as experimental null
tests of the Standard Model in charged and neutral B decays. The CP asymmetries
in hadronic decays of charged B mesons into inclusive final states containing
at least one of the following mesons: K_{S,L}, eta', c\bar c bound states or
neutral K^* or D mesons, for all of which a U-spin rotation is equivalent to a
CP conjugation, are CKM suppressed and furthermore vanish in the exact U-spin
limit. We show how this reduces the theoretical error by using Soft Collinear
Effective Theory to calculate the CP asymmetries for K_{S,L} X_{s+d}, K^*
X_{s+d} and eta' X_{s+d} final states in the endpoint region. For these CP
asymmetries only the flavor and not the charge of the decaying B meson needs to
be tagged up to corrections of NLO in 1/m_b, making the measurements more
accessible experimentally.Comment: 8 pages, significantly expanded after the observation that both
neutral and charged B decays can be used, calculation for decays involving
eta' adde
Regio and Stereospecific 2 + 2 Photoaddition of Cyclopentene to Pentafluoro-alkoxybenzene
2 + 2 photoaddition of cyclopentene to pentafluoro-alkoxybenzene
in cyclohexane solution proceeds stereoselectively anti
and regiospecifically to the 3,4 position
Electronic Structure of Hydrazinium (2 + ) Ion. A Semiempirical MO Treatment
A simple semiempjrical MO treatment of the electronic structure
of hydrazinium (2 + ) ion was carried out on the basis of an
extended Htickel method. The electronic population analysis for
nitrogen and hydrogen atoms in this ion was calculated to b e (ls) 2
(2s)1 -121 (2px)1 ·3Go (2py)t·3Go (2p z)o .9BG and (ls)0o122, respectively
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.
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