2,348 research outputs found

    High-energy scissors mode

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    All the orbital M1 excitations, at both low and high energies, obtained from a rotationally invariant QRPA, represent the fragmented scissors mode. The high-energy M1 strength is almost purely orbital and resides in the region of the isovector giant quadrupole resonance. In heavy deformed nuclei the high-energy scissors mode is strongly fragmented between 17 and 25 MeV (with uncertainties arising from the poor knowledge of the isovector potential). The coherent scissors motion is hindered by the fragmentation and B(M1)<0.25  μN2B(M1) < 0.25 \; \mu^2_N for single transitions in this region. The (e,e)(e,e^{\prime}) cross sections for excitations above 17 MeV are one order of magnitude larger for E2 than for M1 excitations even at backward angles.Comment: 20 pages in RevTEX, 5 figures (uuencoded,put with 'figures') accepted for publication in Phys.Rev.

    Measurements of the Υ(10860)\Upsilon(10860) and Υ(11020)\Upsilon(11020) resonances via σ(e+eΥ(nS)π+π)\sigma(e^+e^-\rightarrow\Upsilon(n{\rm S})\pi^+\pi^-)

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    We report new measurements of the total cross sections for e+eΥ(nS)π+πe^+e^-\to \Upsilon(n{\rm S})\pi^+\pi^- (nn = 1, 2, 3) and e+ebbˉe^+e^-\to b\bar b from a high-luminosity fine scan of the region s=10.63\sqrt{s} = 10.63-11.0511.05 GeV with the Belle detector. We observe that the Υ(nS)π+π\Upsilon(n{\rm S})\pi^+\pi^- spectra have little or no non-resonant component and extract from them the masses and widths of Υ(10860)\Upsilon(10860) and Υ(11020)\Upsilon(11020) and their relative phase. We find M10860=(10891.1±3.21.7+0.6)M_{10860}=(10891.1\pm3.2^{+0.6}_{-1.7}) MeV/c2c^2 and \Gamma_{10860}=(53.7^{+7.1}_{-5.6}\,^{+1.3}_{-5.4}) MeV and report first measurements M_{11020}=(10987.5^{+6.4}_{-2.5}\,^{+9.0}_{-2.1}) MeV/c2c^2, \Gamma_{11020}=(61^{+9}_{-19}\,^{+2}_{-20}) MeV, and \phi_{\rm 11020}-\phi_{\rm 10860} = (-1.0\pm0.4\,^{+1.4}_{-0.1}) rad.Comment: University of Cincinnati preprint UCHEP-15-01, submitted to Physical Review D - Rapid Communication

    Observation of B0pΛˉD()B^{0} \rightarrow p\bar{\Lambda} D^{(*)-}

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    We report the first observation of the decays B0pΛˉD()B^0 \rightarrow p\bar{\Lambda} D^{(*)-}. The data sample of 711711 fb1^{-1} used in this analysis corresponds to 772772 million BBˉB\bar{B} pairs, collected at the Υ(4S)\Upsilon(4S) resonance by the Belle detector at the KEKB asymmetric-energy e+ee^{+}e^{-} collider. We observe 19.8σ19.8\sigma and 10.8σ10.8\sigma excesses of events for the two decay modes and measure the branching fractions of B0pΛˉDB^0 \rightarrow p\bar{\Lambda} D^{-} and B0pΛˉDB^0 \rightarrow p\bar{\Lambda} D^{*-} to be (25.1±2.6±3.5)×106(25.1\pm2.6\pm3.5)\times10^{-6} and (33.6±6.3±4.4)×106(33.6\pm6.3\pm4.4)\times10^{-6}, respectively, where the first uncertainties are statistical and the second are systematic. These results are not compatible with the predictions based on the generalized factorization approach. In addition, a threshold enhancement in the di-baryon (pΛˉp\bar{\Lambda}) system is observed, consistent with that observed in similar BB decays.Comment: 16 pages, 3 figures and 3 tables, submitted to PR

    Evidence for B- -> Ds+ K- l- nubar and search for B- -> Ds*+ K- l- nubar

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    We report measurements of the decays B- -> Ds(*)+ K- l- nubar in a data sample containing 657x10^6 BBbar pairs collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. We observe a signal with a significance of 6 sigma for the combined Ds and Ds* modes and find the first evidence of the B- -> Ds+ K- l- nubar decay with a significance of 3.4 sigma. We measure the following branching fractions: BF(B- -> Ds+ K- l nubar) = (0.30 +/- 0.09(stat) +0.11 -0.08(syst)) x 10^-3 and BF(B- -> Ds*+ K- l- nubar) = (0.59 +/- 0.12(stat) +/- 0.15(syst)) x 10^-3 and set an upper limit BF(B- -> Ds*+ K- l- nubar) < 0.56 x 10^-3 at the 90% confidence level. We also present the first measurement of the Ds+K- invariant mass distribution in these decays, which is dominated by a prominent peak around 2.6 GeV/c^2.Comment: Submitted to Phys. Rev.

    Study of π0\pi^0 pair production in single-tag two-photon collisions

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    We report a measurement of the differential cross section of π0\pi^0 pair production in single-tag two-photon collisions, γγπ0π0\gamma^* \gamma \to \pi^0 \pi^0, in e+ee^+ e^- scattering. The cross section is measured for Q2Q^2 up to 30 GeV2^2, where Q2Q^2 is the negative of the invariant mass squared of the tagged photon, in the kinematic range 0.5 GeV < W < 2.1 GeV and cosθ|\cos \theta^*| < 1.0 for the total energy and pion scattering angle, respectively, in the γγ\gamma^* \gamma center-of-mass system. The results are based on a data sample of 759 fb1^{-1} collected with the Belle detector at the KEKB asymmetric-energy e+ee^+ e^- collider. The transition form factor of the f0(980)f_0(980) and that of the f2(1270)f_2(1270) with the helicity-0, -1, and -2 components separately are measured for the first time and are compared with theoretical calculations.Comment: 36 pages, 37 figures, 11 tables, Belle Preprint 2015-15, KEK Preprint 2015-2

    Measurement of Branching Fraction and Dalitz Distribution for B0->D(*)+/- K0 pi-/+ Decays

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    We present measurements of the branching fractions for the three-body decays B0 -> D(*)-/+ K0 pi^+/-andtheirresonantsubmodes and their resonant submodes B0 -> D(*)-/+ K*+/- using a sample of approximately 88 million BBbar pairs collected by the BABAR detector at the PEP-II asymmetric energy storage ring. We measure: B(B0->D-/+ K0 pi+/-)=(4.9 +/- 0.7(stat) +/- 0.5 (syst)) 10^{-4} B(B0->D*-/+ K0 pi+/-)=(3.0 +/- 0.7(stat) +/- 0.3 (syst)) 10^{-4} B(B0->D-/+ K*+/-)=(4.6 +/- 0.6(stat) +/- 0.5 (syst)) 10^{-4} B(B0->D*-/+ K*+/-)=(3.2 +/- 0.6(stat) +/- 0.3 (syst)) 10^{-4} From these measurements we determine the fractions of resonant events to be : f(B0-> D-/+ K*+/-) = 0.63 +/- 0.08(stat) +/- 0.04(syst) f(B0-> D*-/+ K*+/-) = 0.72 +/- 0.14(stat) +/- 0.05(syst)Comment: 7 pages, 3 figures submitted to Phys. Rev. Let

    Evidence of Υ(1S)J/ψ+χc1\Upsilon(1S) \to J/\psi+\chi_{c1} and search for double-charmonium production in Υ(1S)\Upsilon(1S) and Υ(2S)\Upsilon(2S) decays

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    Using data samples of 102×106102\times10^6 Υ(1S)\Upsilon(1S) and 158×106158\times10^6 Υ(2S)\Upsilon(2S) events collected with the Belle detector, a first experimental search has been made for double-charmonium production in the exclusive decays Υ(1S,2S)J/ψ(ψ)+X\Upsilon(1S,2S)\rightarrow J/\psi(\psi')+X, where X=ηcX=\eta_c, χcJ(J= 0, 1, 2)\chi_{cJ} (J=~0,~1,~2), ηc(2S)\eta_c(2S), X(3940)X(3940), and X(4160)X(4160). No significant signal is observed in the spectra of the mass recoiling against the reconstructed J/ψJ/\psi or ψ\psi' except for the evidence of χc1\chi_{c1} production with a significance of 4.6σ4.6\sigma for Υ(1S)J/ψ+χc1\Upsilon(1S)\rightarrow J/\psi+\chi_{c1}. The measured branching fraction \BR(\Upsilon(1S)\rightarrow J/\psi+\chi_{c1}) is (3.90±1.21(stat.)±0.23(syst.))×106(3.90\pm1.21(\rm stat.)\pm0.23 (\rm syst.))\times10^{-6}. The 90%90\% confidence level upper limits on the branching fractions of the other modes having a significance of less than 3σ3\sigma are determined. These results are consistent with theoretical calculations using the nonrelativistic QCD factorization approach.Comment: 12 pages, 4 figures, 1 table. The fit range was extended to include X(4160) signal according to referee's suggestions. Other results unchanged. Paper was accepted for publication as a regular article in Physical Review
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