The Collins effect connects transverse quark spin with a measurable azimuthal dependence in the yield of hadronic fragments around the quark's momentum vector. Using two different reconstruction ...methods, we find evidence of statistically significant azimuthal asymmetries for charged pion pairs in e(+)e(-) annihilation at a center-of-mass energy of 10.52 GeV, which can be attributed to a transverse polarization of the primordial quarks. The measurement was performed using a sample of 79 x 10(6) hadronic events collected with the Belle detector.
We present a measurement of the standard model CP violation parameter sin2 phi(1) based on a 29.1 fb(-1) data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB ...asymmetric-energy e(+)e(-) collider. One neutral B meson is fully reconstructed as a J/psi K(S), psi(2S)K(S), chi(c1)K(S), eta(c)K(S), J/psi K(L), or J/psi K(*0) decay and the flavor of the accompanying B meson is identified from its decay products. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we determine sin2 phi(1) = 0.99+/-0.14(stat)+/-0.06(syst). We conclude that we have observed CP violation in the neutral B meson system.
We report the observation of an isotriplet of excited charmed baryons, decaying into Lambda(+)(c)pi(-), Lambda(+)(c)pi(0), and Lambda(+)(c)pi(+). We measure the mass differences ...M(Lambda(+)(c)pi)-M(Lambda(+)(c)) and widths to be 515.4(+3.2+2.1)(-3.1-6.0) MeV/c(2), 61(+18+22)(-13-13) MeV for the neutral state; 505.4(+5.8+12.4)(-4.6-2.0) MeV/c(2), 62(+37+52)(-23-38) MeV for the charged state; and 514.5(+3.4+2.8)(-3.1-4.9) MeV/c(2), 75(+18+12)(-13-11) MeV for the doubly charged state, where the uncertainties are statistical and systematic, respectively. These results are obtained from a 281 fb(-1) data sample collected with the Belle detector near the Upsilon(4S) resonance, at the KEKB asymmetric energy e(+)e(-) collider.
We have measured the branching fraction of the inclusive radiative
B meson decay
B→
X
s
γ to be
Br(
B→
X
s
γ)=(3.36±0.53(stat)±0.42(sys)
+0.50
−0.54(th))×10
−4. The result is based on a sample of
...6.07×10
6 B
B
̄
events collected at the
ϒ(4
S) resonance with the Belle detector at the KEKB asymmetric
e
+
e
− storage ring.
The lifetimes of the B(0) and B- mesons are extracted from 29.1 fb(-1) of data collected with the Belle detector at the KEK B factory. A fit to the decay length differences of neutral and charged B ...meson pairs, measured in events where one of the B mesons is fully reconstructed in several hadronic modes, yields tau(B(0)) = 1.554+/-0.030(stat)+/-0.019(syst) ps, tau(B-) = 1.695+/-0.026(stat)+/-0.015(syst) ps, and tau(B-)/tau(B(0)) = 1.091+/-0.023(stat)+/-0.014(syst).
Observation of B decays to two kaons Abe, K; Aihara, H; Anipko, D ...
Physical review letters,
05/2007, Letnik:
98, Številka:
18
Journal Article
Recenzirano
Using 449x10(6) BBover pairs collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider, we observe clear signals for B(+)-->Kover (0)K(+) and B(0)-->Kover (0)K(0) decays with ...5.3sigma and 6.0sigma significance, respectively. We measure the branching fractions B(B(+)-->Kover (0)K(+))=(1.22(-0.28-0.16)(+0.32+0.13))x10(-6) and B(B(0)-->Kover (0)K(0))=(0.87(-0.20)(+0.25)+/-0.09)x10(-6), and partial-rate asymmetries A(CP)(B(+)-->Kover (0)K(+))=0.13(-0.24)(+0.23)+/-0.02 and A(CP)(B(0)-->Kover (0)K(0))=-0.58(-0.66)(+0.73)+/-0.04. From a simultaneous fit, we also obtain B(B(+)-->K(0)pi(+))=(22.8(-0.7)(+0.8)+/-1.3)x10(-6) and A(CP)(B(+)-->K(0)pi(+))=0.03+/-0.03+/-0.01. The first and second error in the branching fractions and the partial-rate asymmetries are statistical and systematic, respectively. No signal is observed for B(0)-->K(+)K(-) decays, and for this branching fraction, we set an upper limit of 4.1x10(-7) at the 90% confidence level.
Status of the Belle SVD detector Abe, R; Aihara, H; Alimonti, G ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2002, Letnik:
478, Številka:
1
Journal Article
Recenzirano
The Belle spectrometer was designed for studies of B meson decays at an asymmetric e
+e
− collider operating at the ϒ(4S) resonance. One of its crucial components, a silicon vertex detector (SVD), is ...placed just outside a cylindrical beryllium beam-pipe. After a year of Belle operation an upgraded version of SVD was installed during the regular summer shut-down. The new SVD follows the same design, with a few important improvements. Rad-soft readout electronics was replaced by rad-tolerant one, allowing for longer lifetime of the detector. A new radiation and temperature monitoring system was developed and implemented. A saw-shaped inner surface was introduced in the beam-pipe to prevent potential synchrotron radiation damage. The upgraded detector started operating successfully in October 2000.
We report measurements of branching fractions for B --> K pi and B --> pi pi decays based on a data sample of 449 x 10(6) BBover pairs collected at the Upsilon(4S) resonance with the Belle detector ...at the KEKB asymmetric-energy e(+)e(-) collider. We also measure the ratios of partial widths for B-->Kpi decays, namely R(c) identical with 2Gamma(B(+) --> K(+) pi(0))/Gamma(B(+) --> K(0) pi(+)) = 1.08+/-0.06+/-0.08 and R(n) identical with Gamma(B(0) --> K(+) pi(-))/2 Gamma(B(0) --> K(0) pi(0)) = 1.08+/-0.08+/-0.08, where the first and the second errors are statistical and systematic, respectively. These ratios are sensitive to enhanced electroweak penguin contributions from new physics; the new measurements are, however, consistent with standard model expectations.
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