2,162 research outputs found
Branching ratios and CP asymmetries in charmless nonleptonic B decays to radially excited mesons
Nonleptonic two body B decays including radially excited or
mesons in the final state are studied using the framework of
generalized naive factorization approach. Branching ratios and CP asymmetries
of , , and decays are calculated, where P and V stand for pseudoscalar and
vector charmless mesons. Form factors for and transitions are estimated in the improved version of the
Isgur-Scora-Grinstein-Wise quark model. In some processes, CP asymmetries of
more than 10% and branching ratios of order are found, which could be
reached in experiments.Comment: 18 pages, 11 table
B_s Mixing and B Hadron Lifetimes at CDF
We present the CDF results using 1.0 fb^{-1} of data on the mixing frequency
measurement in the B_s system and the lifetime measurements of several B
hadrons. We obtain \Delta m_s=17.77 +- 0.1 +- 0.07 ps^{-1} and
c\tau(\Lambda_b)=473.8 +- 23.1 +- 3.5 \mu m. The later one is more than 3 sigma
above the world average, but in reasonable agreement with HQE calculations.Comment: submitted to EPS2007 proceeding
Measuring Bs Width Difference at the Upsilon(5s) Using Quantum Entanglement
About 90% of Bs-bar Bs pairs produced at the Upsilon(5s) resonance are
initially Bs*-bar Bs* pairs which decay radiatively to Bs-bar Bs. This implies
that the Bs pair will then be in an eigenstate of charge conjugation (i.e.
C=-1) and therefore in an entangled state. This allows for a determination of
Delta Gamma/Gamma and the CP phase using a number of possible correlations
between the decays of the two Bs mesons. In particular, we consider the time
integrated correlation; the time ordering asymmetry and the time
ordering-charge asymmetry, which in addition to time ordering distinguishes Bs
from Bs-bar, for various combinations of final states. With the statistics of
about O(10^7-10^8) Upsilon(5s) events available at B factories, we find that
the time ordering asymmetry between suitably defined hadronic and flavor
specific (tagging) decays offers a promising method for determining the width
difference. The corresponding time ordering-charge asymmetry can also bound the
mixing phase. Similar observables involving exclusive decays are also
considered. At the super B factories with O(50) times greater luminosity time
ordering and time ordering-charge asymmetries between inclusive and exclusive
modes may also provide additional bounds on the phases in those decays;Comment: no figures; Updated version: This is the version accepted by Phys Rev
D; Some additional comments were added between equations 8 and 12, also
reference 20 to recent D0 results was adde
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
Subleading Shape-Function Effects and the Extraction of |V_ub|
We derive a class of formulae relating moments of B -> Xu l nu to B -> Xs
gamma in the shape function region, where m_X^2 ~ m_b Lambda_QCD. We also
derive an analogous class of formulae involving the decay B -> Xs l+ l-. These
results incorporate Lambda_QCD/m_b power corrections, but are independent of
leading and subleading hadronic shape functions. Consequently, they enable one
to determine |V_ub|/|V_tb V_ts*| to subleading order in a model-independent
way.Comment: 23 page
Constraining weak annihilation using semileptonic D decays
The recently measured semileptonic D_s decay rate can be used to constrain
weak annihilation (WA) effects in semileptonic D and B decays. We revisit the
theoretical predictions for inclusive semileptonic D_{(s)} decays using a
variety of quark mass schemes. The most reliable results are obtained if the
fits to B decay distributions are used to eliminate the charm quark mass
dependence, without using any specific charm mass scheme. Our fit to the
available data shows that WA is smaller than commonly assumed. There is no
indication that the WA octet contribution (which is better constrained than the
singlet contribution) dominates. The results constrain an important source of
uncertainty in the extraction of |Vub| from inclusive semileptonic B decays.Comment: 5 pages, 2 figures, published versio
Hadron Spectra for Semileptonic Heavy Quark Decay
We calculate the leading perturbative and power corrections to the hadronic
invariant mass and energy spectra in semileptonic heavy hadron decays. We apply
our results to the system. Moments of the invariant mass spectrum, which
vanish in the parton model, probe gluon bremsstrahlung and nonperturbative
effects. Combining our results with recent data on meson branching ratios,
we obtain a lower bound and an upper bound
GeV. The Brodsky-Lepage-Mackenzie scale setting
procedure suggests that higher order perturbative corrections are small for
bottom decay, and even tractable for charm decay.Comment: 24 pages, uses REVTeX, 5 EPS figures embedded with epsf.sty, slightly
modified version to appear in Phys. Rev.
CP Violation in Mixing
The existence of mixing at a detectable level requires
new physics, which effectively yields a superweak interaction.
In general this interaction may involve significant CP violation. For small
values of the mixing it may be much easier to detect the CP-violating part of
the mixing than the CP-conserving part.Comment: 3 pages, latex, no figure
Conclusions from CDF Results on CP Violation in D^0 \to \pi^+\pi^-, K^+K^- and Future Tasks
Within the Standard Model (SM) one predicts both direct and indirect CP
violation in D^0 \to \pi^+\pi^-, K^+K^- transitions, although the effects are
tiny: Indirect CP asymmetry cannot exceed O(10^{-4}), probably even O(10^{-5});
direct effects are estimated at not larger than 10^{-4}. At B factories direct
and indirect asymmetries have been studied with /\tau_{D^0} ~ 1; no CP
asymmetry was found with an upper bound of about 1%. CDF has shown intriguing
data on CP violation in D^0 \to \pi^+\pi^- [K^+K^-] with /\tau_{D^0} ~ 2.4
[2.65]. Also, CDF has not seen any CP violation. For direct CP asymmetry, CDF
has a sensitivity similar to the combination of the B factories, yet for
indirect CP violation it yields a significantly smaller sensitivity of
a_{cp}^{ind}=(-0.01 +- 0.06_{stat} +- 0.05_{syst})% due to it being based on
longer decay times. New Physics models (NP) like Little Higgs Models with
T-Parity (LHT) can produce an indirect CP asymmetry up to 1%; CDF's findings
thus cover the upper range of realistic NP predictions ~ 0.1 - 1%. One hopes
that LHCb and a Super-Flavour Factory will probe the lower range down to
~0.01%. Such non-ad-hoc NP like LHT cannot enhance direct CP violation
significantly over the SM level in D^0 \to \pi^+\pi^-, K^+K^- and D^{\pm} \to
\pi^{\pm}K^+K^- transitions, but others might well do so.Comment: 11 pages, 1 figure. V2 has minor corrections and corresponds to the
published versio
Four-quark Operators Relevant to B Meson Lifetimes from QCD Sum Rules
At the order of 1/m_b^3, the B meson lifetimes are controlled by the hadronic
matrix elements of some four-quark operators. The nonfactorizable magnitudes of
these four-quark operator matrix elements are analyzed by QCD sum rules in the
framework of heavy quark effective theory. The vacuum saturation for
color-singlet four-quark operators is justified at hadronic scale, and the
nonfactorizable effect is at a few percent level. However for color-octet
four-quark operators, the vacuum saturation is violated sizably that the
nonfactorizable effect cannot be neglected for the B meson lifetimes. The
implication to the extraction of some of the parameters from B decays is
discussed. The B meson lifetime ratio is predicted as
\tau(B^-)/\tau(B^0)=1.09\pm 0.02. However, the experimental result of the
lifetime ratio \tau(\Lambda_b)/\tau(B^0) still cannot be explained.Comment: 20 pages, latex, 6 figures, discussion on non-factorizable effect of
the four-quark condensate added, to appear in Phys. Rev. D57 (1998
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