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Register a new userObservation of two charged bottomonium-like resonances in Y(5S) decays
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the Belle Collaboration
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We report the observation of two narrow structures in the mass spectra of the pi+-Y(nS) (n=1,2,3) and pi+-hb(mP)(m$ (m=1,2) pairs that are produced in association with a single charged pion in Y(5S) decays. The measured masses and widths of the two structures averaged over the five final states are M_1=(10607.2+-2.0) MeV/c2, Gamma_1=(18.4+-2.4) MeV and M_2=(10652.2+-1.5) MeV/c2, Gamma_2=(11.5+-2.2) MeV. The results are obtained with a 121.4 1/fb data sample collected with the Belle detector in the vicinity of the Y(5S) resonance at the KEKB asymmetric-energy e+e- collider.
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Recent results obtained using the data sample of 23.6 fb^-1 collected on the Y(5S) resonance with the Belle detector at the KEKB asymmetric energy e+ e- collider are discussed. Measurements of several B_s^0 decay branching fractions are reported. Studies of the Y(5S) decays to the channels with B^+ and B^0 mesons or bottomonium states are discussed.
Decays of the Y(5S) resonance to channels with B^+ and B^0 mesons are studied using a 23.6 fb^-1 data sample collected on the Y(5S) resonance with the Belle detector at the KEKB asymmetric energy e^+ e^- collider. The fully reconstructed B^+ -> J/psi K^+, B^0 -> J/psi K^{*0}, B^+ -> bar_D^0 pi^+ and B^0 -> D^- pi^+ decays are used to obtain the B^+ and B^0 production rates per bb_bar event, f(B^+) = (67.5 pm 3.6 pm 4.8)% and f(B^0)=(70.4^{+5.2}_{-5.1} pm 6.2)%$. Assuming equal rates to B^+ and B^0 mesons in all channels produced at the Y(5S) energy, we measure the fractions for bb_bar event transitions to the two-body and multi-body channels with B^{+/0} meson pairs, f(Bbar{B}) = (5.1 pm 0.9 pm 0.4)%, f(Bbar{B}^*+B^*bar{B}) = (12.6^{+1.2}_{-1.1} pm 1.0)%, f(B^*bar{B}^*) = (34.5^{+1.9}_{-1.8} pm 2.7)%, f(B^{(*)}bar{B}^{(*)}pi(pi)) = (16.4^{+1.6}_{-1.5} pm 1.2)%, f(Bbar{B} pi) = (0.0 pm 1.1 pm 0.2)%, f(Bbar{B}^*pi+B^*bar{B}pi) = (6.8^{+2.1}_{-2.0} pm 0.7)%, and f(B^*bar{B}^*pi) = (1.0^{+1.3}_{-1.2} pm 0.3)%.
Decays of the Y(5S) resonance to channels with B^+ and B^0 mesons are studied using a 23.6 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy e^+ e^- collider. Fully reconstructed B^+ -> J/psi K^+, B^0 -> J/psi K^{*0}, B^+ -> bar{D}^0 pi^+ and B^0 -> D^- pi^+ decays are used to obtain the charged and neutral B production rates per bbar{b} event, f(B^+) = (72.1 ^{+3.9}_{-3.8} pm 5.0)% and f(B^0) = (77.0 ^{+5.8}_{-5.6} pm 6.1)%. Assuming equal rates to B^+ and B^0 mesons in all channels produced at the Y(5S) energy, we measure the fractions for transitions to two-body and three-body channels with B meson pairs, f(Bbar{B}) = (5.5 ^{+1.0}_{-0.9} pm 0.4)%, f(Bbar{B}^* + B^*bar{B}) = (13.7 pm 1.3 pm 1.1)%, f(B^*bar{B}^*) = (37.5 ^{+2.1}_{-1.9} pm 3.0)%, f(Bbar{B}pi) = (0.0 pm 1.2 pm 0.3)%, f(Bbar{B}^*pi + B^*bar{B}pi) = (7.3 ^{+2.3}_{-2.1} pm 0.8)%, and f(B^*bar{B}^*pi) = (1.0 ^{+1.4}_{-1.3} pm 0.4)%. The latter three fractions are obtained assuming isospin conservation.
We report the first observation of Y(5S) -> Y(nS) pi0 pi0 decays. The neutral partner of the Zb+-(10610), the Zb0(10610) decaying to Y(2,3S) pi0, is observed for the first time with a 6.5 sigma significance using a Dalitz analysis of Y(5S) -> Y(2,3S) pi0 pi0 decays. The results are obtained with a 121.4 fb^-1 data sample collected with the Belle detector at the Y(5S) resonance at the KEKB asymmetric-energy e+e- collider.
Many new states in the charmonium and bottomonium mass region were recently discovered by the BaBar, Belle and CDF Collaborations. We use the QCD Sum Rule approach to study the possible structure of some of these states. In particular we identify the recently observed bottomonium-like resonance $Z_b^+(10610)$ with the first excitation of the tetraquark $X_b(1^{++})$, the analogue of the X(3872) state in the charm sector.
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