We report a measurement of the CP-violation parameter φ1 obtained in a time-dependent analysis of B0→D¯(*)0h0 decays followed by D¯0→KS0π+π− decay. A model-independent measurement is performed using ...the binned Dalitz plot technique. The measured value is φ1=11.7°±7.8°(stat)±2.1°(syst). Treating sin2φ1 and cos2φ1 as independent parameters, we obtain sin2φ1=0.43±0.27(stat)±0.08(syst) and cos2φ1=1.06±0.33(stat)−0.15+0.21(syst). The results are obtained with a full data sample of 772×106BB¯ pairs collected near the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider.
A
bstract
We present measurements of absolute branching fractions of hadronic and lep-tonic
$ D_s^{+} $
decays to
K
−
K
+
π
+
,
$ {{\overline{K}}^0} $
K
+
,
ηπ
+
,
μ
+
ν
μ
and
τ
+
ν
τ
and report a ...search for the leptonic
$ D_s^{+} $
→
e
+
ν
e
decays. The results are obtained from a data sample of 913 fb
−1
collected at or near the
$ \varUpsilon $
(4
S
) and
$ \varUpsilon $
(5
S
) resonances with the Belle detector at the KEKB asymmetric-energy
e
+
e
−
collider. The branching fractions of hadronic decays are measured to be
$ \begin{array}{*{20}{c}} {\mathcal{B}\left( {D_s^{+}\ \to\ {K^{-}}{K^{+}}{\pi^{+}}} \right) = \left( {5.06\pm 0.15\pm 0.21} \right)\%,} \\ {\mathcal{B}\left( {D_s^{+}\ \to\ {{\overline{K}}^0}{K^{+}}} \right) = \left( {2.95\pm 0.11\pm 0.09} \right)\%,} \\ {\mathcal{B}\left( {D_s^{+}\ \to\ \eta {\pi^{+}}} \right) = \left( {1.82\pm 0.14\pm 0.07} \right)\%,} \\ \end{array} $
where the first and second uncertainties are statistical and systematic, respectively. The branching fractions of leptonic decays are measured to be
$ \begin{array}{*{20}{c}} {\mathcal{B}\left( {D_s^{+}\ \to\ {\mu^{+}}{\nu_{\mu }}} \right)=\left( {0.531\pm 0.028\pm 0.020} \right)\%,} \\ {\mathcal{B}\left( {D_s^{+}\to {\tau^{+}}{\nu_{\tau }}} \right)=\left( {5.70\pm 0.21_{-0.30}^{-0.31 }} \right)\%,} \\ \end{array} $
which are combined to determine the
$ D_s^{+} $
meson decay constant
$ {f_{{{D_s}}}=\left( {255.5\pm 4.2\pm 5.1} \right)\ \mathrm{MeV}. $
We find no significant signal for
$ D_s^{+} $
→
e
+
ν
e
decays and set an upper limit of
$ \mathcal{B}\left( {D_s^{+}\ \to\ {e^{+}}{\nu_e}} \right) $
<
1
.
0(0
.
83)
×
10
−4
at 95% (90%) confidence level.
A
bstract
An angular analysis of the
B
0
→
K*
0
e
+
e
−
decay is performed using a data sample corresponding to an integrated luminosity of 9 fb
−
1
of
pp
collisions collected with the LHCb ...experiment. The analysis is conducted in the very low dielectron mass squared (
q
2
) interval between 0
.
0008 and 0
.
257 GeV
2
, where the rate is dominated by the
B
0
→
K
*
0
γ
transition with a virtual photon. The fraction of longitudinal polarisation of the
K
*
0
meson,
F
L
, is measured to be
F
L
= (4
.
4 ± 2
.
6 ± 1
.
4)%, where the first uncertainty is statistical and the second systematic. The
A
T
Re
observable, which is related to the lepton forward-backward asymmetry, is measured to be
A
T
Re
=
−
0
.
06 ± 0
.
08 ± 0
.
02. The
A
T
2
and
A
T
Im
transverse asymmetries, which are sensitive to the virtual photon polarisation, are found to be
A
T
2
= 0
.
11 ± 0
.
10 ± 0
.
02 and
A
T
Im
= 0
.
02 ± 0
.
10 ± 0
.
01. The results are consistent with Standard Model predictions and provide the world’s best constraint on the
b
→
sγ
photon polarisation.
A
bstract
A measurement of four branching-fraction ratios for three-body decays of
B
mesons involving two open-charm hadrons in the final state is presented. Run 1 and Run 2
pp
collision data are ...used, recorded by the LHCb experiment at centre-of-mass energies 7, 8, and 13 TeV and corresponding to an integrated luminosity of 9 fb
−
1
. The measured branching-fraction ratios are
B
B
+
→
D
∗
+
D
−
K
+
B
B
+
→
D
¯
0
D
0
K
+
=
0.517
±
0.015
±
0.013
±
0.011
,
B
B
+
→
D
∗
−
D
+
K
+
B
B
+
→
D
¯
0
D
0
K
+
=
0.577
±
0.016
±
0.013
±
0.013
,
B
B
0
→
D
∗
−
D
0
K
+
B
B
0
→
D
−
D
0
K
+
=
1.754
±
0.028
±
0.016
±
0.035
,
B
B
+
→
D
∗
+
D
−
K
+
B
B
+
→
D
∗
−
D
+
K
+
=
0.907
±
0.033
±
0.014
,
where the first of the uncertainties is statistical, the second systematic, and the third is due to the uncertainties on the
D
-meson branching fractions. These are the most accurate measurements of these ratios to date.
We report searches for the processes e+e−→π+π−π0χbJ and e+e−→ϕχbJ (J=1, 2) based on data samples collected by the Belle experiment at the KEKB collider. We report the first observation of the process ...e+e−→(π+π−π0)non−ωχb1 and first evidence for e+e−→ωχbJ in the vicinity of the ϒ(11020) resonance, with center-of-mass energies from 10.96 to 11.05 GeV. The significances for (π+π−π0)non−ωχb1 and ωχbJ are greater than 5.3σ and 4.0σ, respectively. We also investigate the energy dependence of the e+e−→π+π−π0χbJ cross section, but we cannot determine whether the contributions are from the ϒ(10860) and ϒ(11020) resonances or nonresonant continuum processes. The signals for e+e−→ϕχbJ are not significant, and the upper limits of the Born cross sections at the 90% confidence level are 0.7 and 1.0 pb for e+e−→ϕχb1 and ϕχb2, respectively, for center-of-mass energies from 10.96 to 11.05 GeV.
We search for the rare radiative decay D0 → γγ using a data sample with an integrated luminosity of 832 fb–1 recorded by the Belle detector at the KEKB e+e– asymmetric-energy collider. Furthermore we ...find no statistically significant signal and set an upper limit on the branching fraction of B(D0 → γγ) < 8.5 × 10–7 at 90% confidence level. This is the most restrictive limit on the decay channel to date.
A
bstract
The decay-time-dependent
CP
asymmetry in
B
0
→ D
∗±
D
∓
decays is mea- sured using a data set corresponding to an integrated luminosity of 9 fb
−
1
recorded by the LHCb detector in ...proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The
CP
parameters are measured as
S
D
∗
D
=
−
0.861
±
0.077
stat
±
0.019
syst
,
Δ
S
D
∗
D
=
0.019
±
0.075
stat
±
0.012
syst
,
C
D
∗
D
=
−
0.059
±
0.092
stat
±
0.020
syst
,
ΔC
D
∗
D
=
−
0.031
±
0.092
stat
±
0.016
syst
,
A
D
∗
D
=
0.008
±
0.014
stat
±
0.006
syst
.
The analysis provides the most precise single measurement of
CP
violation in this decay channel to date. All parameters are consistent with their current world average values.
Exclusive electroproduction of
ω
mesons on unpolarized hydrogen and deuterium targets is studied in the kinematic region of
Q
2
>
1.0
GeV
2
, 3.0 GeV
<
W
<
6.3 GeV, and
-
t
′
<
0.2
GeV
2
. ...Results on the angular distribution of the
ω
meson, including its decay products, are presented. The data were accumulated with the HERMES forward spectrometer during the 1996–2007 running period using the 27.6 GeV longitudinally polarized electron or positron beam of HERA. The determination of the virtual-photon longitudinal-to-transverse cross-section ratio reveals that a considerable part of the cross section arises from transversely polarized photons. Spin density matrix elements are presented in projections of
Q
2
or
-
t
′
. Violation of
s
-channel helicity conservation is observed for some of these elements. A sizable contribution from unnatural-parity-exchange amplitudes is found and the phase shift between those amplitudes that describe transverse
ω
production by longitudinal and transverse virtual photons,
γ
L
∗
→
ω
T
and
γ
T
∗
→
ω
T
, is determined for the first time. A hierarchy of helicity amplitudes is established, which mainly means that the unnatural-parity-exchange amplitude describing the
γ
T
∗
→
ω
T
transition dominates over the two natural-parity-exchange amplitudes describing the
γ
L
∗
→
ω
L
and
γ
T
∗
→
ω
T
transitions, with the latter two being of similar magnitude. Good agreement is found between the HERMES proton data and results of a pQCD-inspired phenomenological model that includes pion-pole contributions, which are of unnatural parity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The nuclear-mass dependence of azimuthal cross-section asymmetries with respect to charge and longitudinal polarization of the lepton beam is studied for hard exclusive electroproduction of real ...photons. The observed beam-charge and beam-helicity asymmetries are attributed to the interference between the Bethe-Heitler and the deeply virtual Compton scattering processes. For various nuclei, the asymmetries are extracted for both coherent and incoherent-enriched regions, which involve different (combinations of) generalized parton distributions. For both regions, the asymmetries are compared to those for a free proton, and no nuclear-mass dependence is found.
PDF
