Explore the vast range of titles available.

An estimate is given of the simulation with the Monte Carlo (MC) method using the signal to background ratios in invariant mass spectra of pion-kaon system for decays of D 0 → K − π + and → K + π − originated from decays of D * + → D 0 π + and D* − → π − at different momentum/angular bins of pions (when pion is coming to the ARICH acceptance) and kaons (kaon is in ARICH acceptance). The tabulated data for mentioned ratios will be used by Belle II collaboration to study the ARICH performance. Then the results of ARICH efficiencies and misidentification probability extracted based on tabulated ratios, will become important ingredient for future physics analysis.

Abstract The Aerogel Ring Imaging Cherenkov (ARICH) counter serves as a particle identification device in the forward end-cap region of the Belle II spectrometer. It is capable of identifying pions and kaons with momenta up to $4\\>$GeV$\\>$c$^{-1}$ by detecting Cherenkov photons emitted in the silica aerogel radiator. After the detector alignment and calibration of the probability density function, we evaluate the performance of the ARICH counter using early beam collision data. Event samples of $D^{\\ast +} \\to D^0 \\pi^+ (D^0 \\to K^-\\pi^+)$ were used to determine the $\\pi(K)$ efficiency and the $K(\\pi)$ misidentification probability. We found that the ARICH counter is capable of separating kaons from pions with an identification efficiency of $93.5 \\pm 0.6 \\, \\%$ at a pion misidentification probability of $10.9 \\pm 0.9 \\, \\%$. This paper describes the identification method of the counter and the evaluation of the performance during its early operation.

We report the first measurement of the exclusive cross sections e+e- → $B\\overline{B}$, e+e- → $B{\\overline{B}}^{\\ast }$, and e+e- → ${B}^{\\ast }{\\overline{B}}^{\\ast }$ in the energy range from 10.63 GeV to 11.02 GeV. The B mesons are fully reconstructed in a large number of hadronic final states and the three channels are identified using a beam-constrained-mass variable. The shapes of the exclusive cross sections show oscillatory behavior with several maxima and minima. The results are obtained using data collected by the Belle experiment at the KEKB asymmetric-energy e+e- collider.

Charged lepton flavor violation is forbidden in the Standard Model but possible in several new physics scenarios. In many of these models, the radiative decays $\\tau^{\\pm}\\rightarrow\\ell^{\\pm}\\gamma$ ($\\ell=e,\\mu$) are predicted to have a sizeable probability, making them particularly interesting channels to search at various experiments. An updated search via $\\tau^{\\pm}\\rightarrow\\ell^{\\pm}\\gamma$ using full data of the Belle experiment, corresponding to an integrated luminosity of 988 fb$^{-1}$, is reported for charged lepton flavor violation. No significant excess over background predictions from the Standard Model is observed, and the upper limits on the branching fractions, $\\mathcal{B}(\\tau^{\\pm}\\rightarrow \\mu^{\\pm}\\gamma)$$\\leq$$4.2\\times10^{-8}$ and $\\mathcal{B}(\\tau^{\\pm}\\rightarrow e^{\\pm}\\gamma)$$\\leq$$5.6\\times10^{-8}$, are set at 90% confidence level.

We measure the branching fractions and CP asymmetries for the singly Cabibbo-suppressed decays D$^{0}$ → π$^{+}$π$^{−}$η, D$^{0}$ → K$^{+}$K$^{−}$η, and D$^{0}$ → ϕη, using 980 fb$^{−1}$ of data from the Belle experiment at the KEKB e$^{+}$e$^{−}$ collider. We obtain$ {\\displaystyle \\begin{array}{c}\\mathcal{B}\\left({D}^0\\to {\\pi}^{+}{\\pi}^{-}\\eta \\right)=\\left[1.22\\pm 0.02\\left(\\mathrm{stat}\\right)\\pm 0.02\\left(\\mathrm{syst}\\right)\\pm 0.03\\left({\\mathcal{B}}_{\\mathrm{ref}}\\right)\\right]\\times {10}^{-3},\\\ {}\\mathcal{B}\\left({D}^0\\to {K}^{+}{K}^{-}\\eta \\right)=\\left[{1.80}_{-0.06}^{+0.07}\\left(\\mathrm{stat}\\right)\\pm 0.04\\left(\\mathrm{syst}\\right)\\pm 0.05\\left({\\mathcal{B}}_{\\mathrm{ref}}\\right)\\right]\\times {10}^{-4},\\\ {}\\mathcal{B}\\left({D}^0\\to \\phi \\eta \\right)=\\left[1.84\\pm 0.09\\left(\\mathrm{stat}\\right)\\pm 0.06\\left(\\mathrm{syst}\\right)\\pm 0.05\\left({\\mathcal{B}}_{\\mathrm{ref}}\\right)\\right]\\times {10}^{-4},\\end{array}} $where the third uncertainty ($ \\mathcal{B} _{ref}$) is from the uncertainty in the branching fraction of the reference mode D$^{0}$ → K$^{−}$π$^{+}$η. The color-suppressed decay D$^{0}$ → ϕη is observed for the first time, with very high significance. The results for the CP asymmetries are$ {\\displaystyle \\begin{array}{c}{A}_{CP}\\left({D}^0\\ {\\pi}^{+}{\\pi}^{-}\\eta \\right)=\\left[0.9\\pm 1.2\\left(\\mathrm{stat}\\right)\\pm 0.5\\left(\\mathrm{syst}\\right)\\right]\\%,\\\ {}{A}_{CP}\\left({D}^0\\to {K}^{+}{K}^{-}\\eta \\right)=\\left[-1.4\\pm 3.3\\left(\\mathrm{stat}\\right)\\pm 1.1\\left(\\mathrm{syst}\\right)\\right]\\%,\\\ {} ACP\\ \\left({D}^0\\to \\phi \\eta \\right)=\\left[-1.9\\pm 4.4\\left(\\mathrm{stat}\\right)\\pm 0.6\\left(\\mathrm{syst}\\right)\\right]\\%.\\end{array}} $The results for D$^{0}$ → π$^{+}$π$^{−}$η are a significant improvement over previous results. The branching fraction and A$_{CP}$ results for D$^{0}$ → K$^{+}$K$^{−}$η, and the ACP result for D$^{0}$ → ϕη, are the first such measurements. No evidence for CP violation is found in any of these decays.[graphic not available: see fulltext]

Using a data sample of 980 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider, we study the processes of $\\Xi^0_c\\to \\Lambda\\bar K^{*0}$, $\\Xi^0_c\\to \\Sigma^0\\bar K^{*0}$, and $\\Xi^0_c\\to \\Sigma^+K^{*-}$ for the first time. The relative branching ratios to the normalization mode of $\\Xi^0_c\\to\\Xi^-\\pi^+$ are measured to be $${\\cal B}(\\Xi^0_c\\to \\Lambda\\bar K^{*0})/{\\cal B}(\\xic\\to \\Xi^-\\pi^+)=0.18\\pm0.02({\\rm stat.})\\pm0.01({\\rm syst.}),$$${\\cal B}(\\Xi^0_c\\to \\Sigma^0\\bar K^{*0})/{\\cal B}(\\xic\\to \\Xi^-\\pi^+)=0.69\\pm0.03({\\rm stat.})\\pm0.03({\\rm syst.}),$$${\\cal B}(\\Xi^0_c\\to \\Sigma^+K^{*-})/{\\cal B}(\\xic\\to \\Xi^-\\pi^+)=0.34\\pm0.06({\\rm stat.})\\pm0.02({\\rm syst.}),$$ where the uncertainties are statistical and systematic, respectively. We obtain %measure the branching fractions of $\\Xi^0_c\\to \\Lambda\\bar K^{*0}$, $\\Xi^0_c\\to \\Sigma^0\\bar K^{*0}$, and $\\Xi^0_c\\to \\Sigma^+K^{*-}$ to be $${\\cal B}(\\Xi^0_c\\to \\Lambda\\bar K^{*0})=(3.3\\pm0.3({\\rm stat.})\\pm0.2({\\rm syst.})\\pm1.0({\\rm ref.}))\\times10^{-3},$$ $${\\cal B}(\\Xi^0_c\\to \\Sigma^0\\bar K^{*0})=(12.4\\pm0.5({\\rm stat.})\\pm0.5({\\rm syst.})\\pm3.6({\\rm ref.}))\\times10^{-3},$$ $${\\cal B}(\\Xi^0_c\\to \\Sigma^+K^{*-})=(6.1\\pm1.0({\\rm stat.})\\pm0.4({\\rm syst.})\\pm1.8({\\rm ref.}))\\times10^{-3},$$ where the uncertainties are statistical, systematic, and from ${\\cal B}(\\xic \\to \\Xi^-\\pi^+)$, respectively. The asymmetry parameters $\\alpha(\\Xi^0_c\\to \\Lambda\\bar K^{*0})$ and $\\alpha(\\Xi^0_c\\to \\Sigma^+K^{*-})$ are $0.15\\pm0.22({\\rm stat.})\\pm0.04({\\rm syst.})$ and $-0.52\\pm0.30({\\rm stat.})\\pm0.02({\\rm syst.})$, respectively, where the uncertainties are statistical followed by systematic.

We present measurements of the branching fractions for the decays B → Kμ$^{+}$μ$^{−}$ and B → Ke$^{+}$e$^{−}$, and their ratio (R$_{K}$), using a data sample of 711 fb$^{−1}$ that contains 772 × 10$^{6} B\\overline{B} $ events. The data were collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e$^{+}$e$^{−}$ collider. The ratio R$_{K}$ is measured in five bins of dilepton invariant-mass-squared (q$^{2}$): q$^{2}$ ∈ (0.1, 4.0), (4.00, 8.12), (1.0, 6.0), (10.2, 12.8) and (> 14.18) GeV$^{2}$/c$^{4}$, along with the whole q$^{2}$ region. The R$_{K}$ value for q$^{2}$ ∈ (1.0, 6.0) GeV$^{2}$/c$^{4}$ is $ {1.03}_{-0.24}^{+0.28} $ ± 0.01. The first and second uncertainties listed are statistical and systematic, respectively. All results for R$_{K}$ are consistent with Standard Model predictions. We also measure CP-averaged isospin asymmetries in the same q$^{2}$ bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the q$^{2}$ ∈ (1.0, 6.0) GeV$^{2}$/c$^{4}$ bin in the mode with muon final states. The measured differential branching fractions, $ d\\mathrm{\\mathcal{B}} $/dq$^{2}$, are consistent with theoretical predictions for charged B decays, while the corresponding values are below the expectations for neutral B decays. We have also searched for lepton-flavor-violating B → Kμ$^{±}$e$^{∓}$ decays and set 90% confidence-level upper limits on the branching fraction in the range of 10$^{−8}$ for B$^{+}$ → K$^{+}$μ$^{±}$e$^{∓}$, and B$^{0}$ → K$^{0}$μ$^{±}$e$^{∓}$ modes.[graphic not available: see fulltext]

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.

The first dedicated search for the ηc2(1D) is carried out using the decaysB+ → ηc2(1D)K+, B0 → ηc2(1D)K0S, B0 → ηc2(1D)π−K+, and B+ → ηc2(1D)π+K0Swith ηc2(1D) → hcγ. No significant signal is found. For the ηc2(1D) mass range between3795 and 3845 MeV/c2, the branching-fraction upper limits are determined to be B(B+ →ηc2(1D)K+) × B(ηc2(1D) → hcγ) < 3.7 × 10−5, B(B0 → ηc2(1D)K0S) × B(ηc2(1D) →hcγ) < 3.5 × 10−5, B(B0 → ηc2(1D)π−K+) × B(ηc2(1D) → hcγ) < 1.0 × 10−4, andB(B+ → ηc2(1D)π+K0S) × B(ηc2(1D) → hcγ) < 1.1 × 10−4 at 90% C. L. The analysis isbased on the 711 fb−1 data sample collected on the Υ(4S) resonance by the Belle detector,which operated at the KEKB asymmetric-energy e+e− collider.

We present the first model-independent measurement of the CKM unitarity triangle angle Φ3 using B±→ D( \\( {K}_{\\mathrm{S}}^0 \\) π+π–π0) K± decays, where D indicates either a D0 or \\( \\overline{D} \\) 0 meson. Measurements of the strong-phase difference of the D → \\( {K}_{\\mathrm{S}}^0 \\) π+π–π0 amplitude obtained from CLEO-c data are used as input. This analysis is based on the full Belle data set of $772 × 10^6 B$ \\( \\overline{B} \\) events collected at the Υ(4S) resonance. We obtain Φ3 = ( \\( {5.7}_{-8.8}^{+10.2} \\) ±3.5±5.7)° and the suppressed amplitude ratio rB = 0.323±0.147±0.023±0.051. Here the first uncertainty is statistical, the second is the experimental systematic, and the third is due to the precision of the strong-phase parameters measured from CLEO-c data. The 95% confidence interval on Φ3 is (–29.7, 109.5)°, which is consistent with the current world average.