820 research outputs found
Scalar form factors of light mesons
The scalar radius of the pion plays an important role in CHPT, because it is
related to one of the basic effective coupling constants, viz. the one which
controls the quark mass dependence of F_pi at one loop. In a recent paper,
Yndurain derives a {\it robust lower bound} for this radius, which disagrees
with earlier determinations. We show that such a bound does not exist: the
"derivation" relies on an incorrect claim. Moreover, we discuss the physics of
the form factors associated with the operators \ubar u, \dbar d and \sbar s and
show that their structure in the vicinity of the K \Kbar threshold is quite
different. Finally, we draw attention to the fact that the new data on the
slope of the scalar K_l3 form factor confirm a recent, remarkably sharp
theoretical prediction.Comment: 13 pages, 2 figures. v2: minor changes - version to appear on Phys.
Lett. B. v3: Published version. Values of the measured K-pi radii correcte
Weak productions of new charmonium in semi-leptonic decays of B_c
We study the weak productions of novel heavy mesons, such as
, , , , X(3940),
Y(3940), X(3872), and Y(4260), in the semi-leptonic decays. Since there
is still no definite answer for the components of X(3940), Y(3940), X(3872),
Y(4260) so far, we will assign them as excited charmonium states with the
possible quantum numbers constrained by the current experiments. As for the
weak transition form factors, we calculate them in the framework of light-cone
QCD sum rules approach, which is proved to be a powerful tool to deal with the
non-perturbative hadronic matrix element. Our results indicate that different
interpretations of X(3940) can result in remarkable discrepancy of the
production rate in the decays, which would help to clarify the inner
structure of the X(3940) with the forthcoming LHC-b experiments. Besides, the
predicted large weak production rates of X(3872) and Y(3940) in decays
and the small semi-leptonic decay rate for all depend on
their quantum number assignments. Moreover, the mixing of
various vector charmonium states in the weak decay of is also discussed
in this work. The future experimental measurements of these decays will test
the inner structures of these particles, according to our predictions here.Comment: 26 pages, with 7 figures, revTex
Double-Lepton Polarization Asymmetries and Branching Ratio in B \rar K_{0}^{*}(1430) l^+ l^- transition from Universal Extra Dimension Model
We investigate the B \rar K_{0}^{*}(1430) l^+ l^- transition in the
Applequist-Cheng-Dobrescu model in the presence of a universal extra dimension.
In particular, we calculate double lepton polarization asymmetries and
branching ratio related to this channel and compare the obtained results with
the predictions of the standard model. Our analysis of the considered
observables in terms of radius of the compactified extra-dimension as the
new parameter of the model show a considerable discrepancy between the
predictions of two models in low values.Comment: 12 Pages, 15 Figures and 1 Tabl
Factorization fits to charmless strangeless B decays
We present fits to charmless strangeless hadronic B decay data for mean
branching ratios and CP-violating asymmetries using the QCD factorization model
of Beneke et al. Apart from one CP-violating parameter, the model gives a very
good representation of 26 measured data. We find the CKM angle alpha = (93.5
+/- 8.4 -1.3) degrees and to be quite stable to plausible "charming penguin"
corrections.Comment: 4 pages, LaTeX, Minor changes to text, references adde
Lifetimes of b-flavoured hadrons
I discuss the heavy quark expansion for the inclusive widths of heavy-light
hadrons, which predicts quite well the experimental ratios of B_q meson
lifetimes. As for , current determinations of
contribution to do not allow to explain the small measured
value of . As a final topic, I discuss the
implications of the measurement of the B_c lifetime.Comment: LaTex, 4 pages, 1 figure. Talk given at the "U.K. Phenomenology
Workshop on Heavy Flavours and CP violation" Durham, 17-22 Sep. 2000 (Mixing
and Lifetimes Working Group
Decay properties of new D-mesons
We consider radiative and pionic decays of the new D_s-mesons in the
framework of a phenomenologically motivated approach. Present data on ratios of
the two kinds of decays can be described without explicit using a 4-quark
component. Most probably, the isospin violation in decays of different
D_s-mesons is not universal, and the binding potential should be different from
Coulombic. New precise measurements may provide further clarification for the
nature of the D_s excited states.Comment: 12 pages, Late
Strong coupling constants of bottom and charmed mesons with scalar, pseudoscalar and axial vector kaons
The strong coupling constants, , ,
, , and
, where , and are scalar, pseudoscalar
and axial vector kaon mesons, respectively are calculated in the framework of
three-point QCD sum rules. In particular, the correlation functions of the
considered vertices when both and mesons are off-shell
are evaluated. In the case of , which is either or
, the mixing between these two states are also taken into account. A
comparison of the obtained result with the existing prediction on
as the only coupling constant among the considered
vertices, previously calculated in the literature, is also made.Comment: 20 Pages, 3 Figures and 8 Table
Calculation of coupling constant g_phi-pi-gamma in QCD sum rules
The coupling constant of g_phi-pi-gamma decay is calculated in the method of
QCD sum rules. A comparison of our prediction on the coupling constant with the
result obtained from analysis of the experimental data is performed.Comment: 6 pages, 3 figure
Scalar Quarkonia at Finite Temperature
Masses and decay constants of the scalar quarkonia, with
quantum numbers are calculated in the framework of
the QCD sum rules approach both in vacuum and finite temperature. The masses
and decay constants remain unchanged up to but they start to
diminish with increasing the temperature after this point. At near the critic
or deconfinement temperature, the decay constants reach approximately to 25% of
their values in vacuum, while the masses are decreased about 6% and 23% for
bottom and charm cases, respectively. The results at zero temperature are in a
good consistency with the existing experimental values and predictions of the
other nonperturbative approaches. Our predictions on the decay constants in
vacuum as well as the behavior of the masses and decay constants with respect
to the temperature can be checked in the future experiments.Comment: 12 Pages, 9 Figures and 2 Table
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