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Abdesselam, A.

Publications and source records attributed to Abdesselam, A..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Observation of Z b ( 10610 ) and Z b ( 10650 ) Decaying to B Mesons

We detail the analysis of the three-body e + e - → B B ¯ π ± , B B ¯ * π ± , and B * B ¯ * π ± processes, including the first observations of the Z b ± ( 10 610 ) → [ B B ¯ * + c . c . ] ± and Z b ± ( 10 650 ) → [ B * B ¯ * ] ± transitions that are found to dominate the corresponding final states. We measure Born cross sections for the three-body production of σ ( e + e - → [ B B ¯ * + c . c . ] ± π ∓ ) = [ 17.4 ± 1.6 ( stat ) ± 1.9 ( syst ) ] pb and σ ( e + e - → [ B * B ¯ * ] ± π ∓ ) = [ 8.75 ± 1.15 ( stat ) ± 1.04 ( syst ) ] pb and set a 90% C.L. upper limit of σ ( e + e - → [ B B ¯ ] ± π ∓ ) < 2.9 pb . The results are based on a 121.4 fb - 1 data sample collected with the Belle detector at a center-of-mass energy near the Υ ( 10 860 ) peak.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

First model-independent Dalitz analysis of B 0 → DK* 0 , D→K$^{0}_{S}$π + π – decay

We report a measurement of the amplitude ratio r S of B 0 → D 0 K* 0 and B 0 → D 0 ¯K* 0 decays with a Dalitz analysis of D → K$^{0}_{S}$π + π – decays, for the first time using a model-independent method. We set an upper limit rS<0.87 at the 68\% confidence level, using the full data sample of 772×10 6 BB¯ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB e + e – collider. This result is obtained from observables x–= +0.4$^{+1.0+0.0}_{–0.6–0.1}$ ± 0.0, y– = –0.6$^{+0.8+0.1}_{–1.0–0.0}$ ± 0.1, x + = +0.1$^{+0.7+0.0}_{–0.4–0.1}$ ± 0.1 and y + = +0.3$^{+0.5+0.0}_{–0.8–0.1}$ ± 0.1, where x ± = r S cos(δ S ± Φ 3 ), y ± = r S sin(δ S ± Φ 3 ) and Φ 3 (δ S ) is the weak (strong) phase difference between B 0 → D 0 K* 0 and B 0 → D¯ 0 K* 0 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Observation of the Decay B s 0 → K 0 K ¯ 0

We measure the decay B$^{0}_{s}$ → K 0 K¯ 0 using data collected at the Υ(5S) resonance with the Belle detector at the KEKB e + e – collider. The data sample used corresponds to an integrated luminosity of 121.4 fb–1. We measure a branching fraction B(B$^{0}_{s}$ → K 0 K¯ 0 ) = [19.6$^{+5.8}_{–5.1}$(stat.) ± 1.0(sys.)±2.0(N B$^{0}_{s}$B¯$^{0}_{s}$ )]×10 –6 with a significance of 5.1 standard deviations. Here, this measurement constitutes the first observation of this decay.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Inclusive and exclusive measurements of B decays to χ c 1 and χ c 2 at Belle

We report inclusive and exclusive measurements for χ c1 and χ c2 production in B decays. We measure B(B→ χc1 X) = (3.03 ± 0.05(stat) ± 0.24(syst)) × 10 –3 and B(B→χ c2 X) = (0.70 ± 0.06(stat) ± 0.10(syst)) × 10 –3 . For the first time, χ c2 production in exclusive B decays in the modes B 0 →χ c2 π – K + and B + →χ c2 π + π – K + has been observed, along with first evidence for the B + →χ c2 π + K$^{0}_{S}$ decay mode. For χ c1 production, we report the first observation in the B + →χ c1 π + π – K + , B 0 →χ c1 π + π – K$^{0}_{S}$ and B 0 →χ c1 π 0 π – K + decay modes. Using these decay modes, we observe a difference in the production mechanism of χ c2 in comparison to χ c1 in B decays. In addition, we report searches for X(3872) and χ c1 (2P) in the B + →(χ c1 π + π – )K + decay mode. In conclusion, the reported results use 772 × 10 6 BB¯ events collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e – collider.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Search for the rare decay D 0 → γ γ at Belle

We search for the rare radiative decay D 0 → 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(D 0 → γγ) < 8.5 × 10 –7 at 90% confidence level. This is the most restrictive limit on the decay channel to date.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Study of B 0 → ρ + ρ – decays and implications for the CKM angle Φ 2

We present a measurement of the branching fraction and the longitudinal polarization fraction of B 0 → ρ + ρ – decays, as well as the time-dependent CP violating parameters in decays into longitudinally polarized ρ + ρ – pairs with Belle’s final data set of 772 × 10 6 BB¯ pairs, at the Υ(4S) resonance, collected at the asymmetric-energy e + e – collider KEKB. We obtain B(B 0 → ρ + ρ – ) = (28.3 ± 1.5(stat) ± 1.5(syst)) × 10 –6 , f L = 0.988 ± 0.012(stat) ± 0.023(syst), A CP = 0.00 ± 0.10(stat) ± 0.06(syst), S CP = –0.13 ± 0.15(stat) ± 0.05(syst). As a result, we perform an isospin analysis to constrain the Cabibbo-Kobayashi-Maskawa angle Φ 2 and obtain two solutions with Φ 2 = (93.7 ± 10.6)°, being most compatible with other Standard-Model based fits to the data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of the decay B → D ℓ ν ℓ in fully reconstructed events and determination of the Cabibbo-Kobayashi-Maskawa matrix element | V c b |

We present a determination of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| using the decay B → Dℓν ℓ (ℓ = e,μ) based on 711 fb –1 of e + e – → Υ(4S) data recorded by the Belle detector and containing 772 × 10 6 BB¯ pairs. Here, one B meson in the event is fully reconstructed in a hadronic decay mode, while the other, on the signal side, is partially reconstructed from a charged lepton and either a D + or D 0 meson in a total of 23 hadronic decay modes. The isospin-averaged branching fraction of the decay B → Dℓν ℓ is found to be B(B 0 → D – ℓ + ν ℓ ) = (2.31 ± 0.03(stat) ± 0.11(syst))%. Analyzing the differential decay rate as a function of the hadronic recoil with the parametrization of Caprini, Lellouch, and Neubert and using the form-factor prediction G(1) = 1.0541 ± 0.0083 calculated by FNAL/MILC, we obtain η EW |V cb | = (40.12 ± 1.34) × 10 –3 , where ηEW is the electroweak correction factor. Alternatively, assuming the model-independent form-factor parametrization of Boyd, Grinstein, and Lebed and using lattice QCD data from the FNAL/MILC and HPQCD collaborations, we find η EW |V cb | = (41.10 ± 1.14) × 10 –3 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

First observation of the decay B 0 → ψ ( 2 S ) π 0

We report a measurement of the B 0 → ψ(2S)π 0 branching fraction based on the full Υ(4S) data set of 772 × 10 6 BB¯ pairs collected by the Belle detector at the KEKB asymmetric-energy e + e – collider. We obtain B(B 0 → ψ(2S)π 0 ) = (1.17 ± 0.17(stat) ± 0.08(syst)) × 10 –5 . Here, the result has a significance of 7.2 standard deviations and is the first observation of the decay B 0 → ψ(2S)π 0 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Search for B 0 → π – τ + ν τ with hadronic tagging at Belle

We search for the process B 0 → π – τ + ν τ using the full Belle data set of 711 fb –1 , corresponding to 772 × 10 6 BB¯ pairs, collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e – collider. Here, we reconstruct one B meson in a hadronic decay and search for the B 0 → π – τ + ν τ process in the remainder of the event. No significant signal is observed and an upper limit of B(B 0 → π – τ + ν τ ) < 2.5 × 10 –4 is obtained at the 90% confidence level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Study of π 0 pair production in single-tag two-photon collisions

We report a measurement of the differential cross section of π 0 pair production in single-tag two-photon collisions, γ*γ→π 0 π 0 , in e + e - scattering. The cross section is measured for Q 2 up to 30 GeV 2 , where Q 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*| < 1.0 for the total energy and pion scattering angle, respectively, in the γ*γ center-of-mass system. The results are based on a data sample of 759 fb -1 collected with the Belle detector at the KEKB asymmetric-energy e + e - collider. The transition form factor of the f 0 (980) and that of the f 2 (1270) with the helicity-0, -1, and -2 components separately are measured for the first time and are compared with theoretical calculations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of the lepton forward-backward asymmetry in B → X s ℓ + ℓ - decays with a sum of exclusive modes

We report the first measurement of the lepton forward-backward asymmetry $\mathscr{A}$ FB as a function of the squared four-momentum of the dilepton system, q 2 , for the electroweak penguin process B→X s ℓ + ℓ - with a sum of exclusive final states, where ℓ is an electron or a muon and X s is a hadronic recoil system with an s quark. The results are based on a data sample containing 772×10 6 $B$$\bar{B}$ pairs recorded at the Υ(4S) resonance with the Belle detector at the KEKB e + e - collider. $\mathscr{A}4 FB for the inclusive B→X s ℓ + ℓ - is extrapolated from the sum of 10 exclusive X s states whose invariant mass is less than 2 GeV/c 2 . For q 2 >10.2 GeV 2 /c 2 , $\mathscr{A}$ FB <0 is excluded at the 2.3σ level, where σ is the standard deviation. For q 2 <4.3 GeV 2 /c 2 , the result is within 1.8σ of the Standard Model theoretical expectation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurements of the Υ ( 10860 ) and Υ ( 11020 ) resonances via σ ( e + e - → Υ ( n S ) π + π - )

In this work, we report new measurements of the total cross sections for e + e - → Υ ( n S ) π + π - ( n = 1 , 2, 3) and e + e - → b b ¯ from a high-luminosity fine scan of the region s = 10.63 – 11.05 GeV with the Belle detector. We observe that the Υ ( n S ) π + π - spectra have little or no nonresonant component and extract from them the masses and widths of Υ ( 10860 ) and Υ ( 11020 ) and their relative phase. We find M 10860 = ( 10891.1 ± 3. 2 - 1.7 + 0.6 ) MeV / c 2 and Γ 10860 = ( 53. 7 - 5.6 - 5.4 + 7.1 + 1.3 ) MeV and report first measurements M 11020 = ( 10987. 5 - 2.5 - 2.1 + 6.4 + 9.0 ) MeV / c 2 , Γ 11020 = ( 6 1 - 19 - 20 + 9 + 2 ) MeV , and Φ 11020 - Φ 10860 = ( - 1.0 ± 0.4 - 0.1 + 1.4 ) rad .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Observation of B 0 → p Λ ¯ D ( * ) -

We report the first observation of the decays B 0 →p$\bar{Λ}$D(*)-. The data sample of 711 fb -1 used in this analysis corresponds to 772 million $B$$\bar{B}$ pairs, collected at the Υ(4S) resonance by the Belle detector at the KEKB asymmetric-energy e + e - collider. We observe 19.8σ and 10.8σ excesses of events for the two decay modes and measure the branching fractions of B 0 →p$\bar{Λ}$D- and B 0 →p$\bar{Λ}$D(*)- to be (25.1±2.6±3.5)×10 -6 and (33.6±6.3±4.4)×10 -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 (p$\bar{Λ}$) system is observed, consistent with that observed in similar B decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Inclusive cross sections for pairs of identified light charged hadrons and for single protons in e + e - at s = 10.58 GeV

We report the first double differential cross sections of two charged pions and kaons (e + e - →hhX) in electron-positron annihilation as a function of the fractional energies of the two hadrons for any charge and hadron combination. The dependence of these di-hadron cross sections on the topology (same, opposite-hemisphere or anywhere) is also studied with the help of the event shape variable thrust and its axis. The ratios of these di-hadron cross sections for different charges and hadron combinations directly shed light on the contributing fragmentation functions. For example, we find that the ratio of same-sign pion pairs over opposite-sign pion pairs drops toward higher fractional energies where disfavored fragmentation is expected to be suppressed. These di-hadron results are obtained from a 655fb -1 data sample collected near the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e - collider. Extending the previously published single-pion and single-kaon cross sections, single-proton (e + e - →pX) cross sections are extracted from a 159fb -1 data sub-sample.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of the branching ratio of B ¯ → D ( * ) τ - ν ¯ τ relative to B ¯ → D ( * ) ℓ - ν ¯ ℓ decays with hadronic tagging at Belle

In this article we report a measurement of the branching fraction ratios R ( D ( * ) ) of B ¯ → D ( * ) τ - ν ¯ τ relative to B ¯ → D ( * ) ℓ - ν ¯ ℓ (where ℓ = e or μ ) using the full Belle data sample of 772 × 10 6 B B ¯ pairs collected at the Υ ( 4 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e - collider. The measured values are R ( D ) = 0.375 ± 0.064 ( stat ) ± 0.026 ( syst ) and R ( D * ) = 0.293 ± 0.038 ( stat ) ± 0.015 ( syst ) . The analysis uses hadronic reconstruction of the tag-side B meson and purely leptonic τ decays. The results are consistent with earlier measurements and do not show a significant deviation from the standard model prediction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Semi-inclusive studies of semileptonic B s decays at Belle

We present an analysis of the semi-inclusive decays B s → D s - X ℓ + ν and B s → D s * - X ℓ + ν , where X denotes a final state that may consist of additional hadrons or photons and ℓ is an electron or muon. The studied B s decays are contained in the 121.4 fb - 1 Υ ( 5 S ) data sample collected by the Belle detector at the KEKB asymmetric-energy e + e - collider. The branching fractions of the decays are measured to be B ( B s → D s - X ℓ + ν ) = [ 8.2 ± 0.2 ( stat ) ± 0.6 ( syst ) ± 1.4 ( ext ) ] % and B ( B s → D s * - X ℓ + ν ) = [ 5.4 ± 0.4 ( stat ) ± 0.4 ( syst ) ± 0.9 ( ext ) ] % , where the first two uncertainties are statistical and systematic and the last is due to external parameters. The measurement also provides an estimate of the B s ( * ) B ¯ s ( * ) production cross section, σ ( e + e - → B s ( * ) B ¯ s ( * ) ) = [ 53.8 ± 1.4 ( stat ) ± 4.0 ( syst ) ± 3.4 ( ext ) ] pb , at the center-of-mass energy s = 10.86 GeV .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

First Observation of the Hadronic Transition Υ ( 4 S ) → η h b ( 1 P ) and New Measurement of the h b ( 1 P ) and η b ( 1 S ) Parameters

Using a sample of 771.6 × 10 6 Υ Υ ( 4 S ) decays collected by the Belle experiment at the KEKB e + e - collider, we observe, for the first time, the transition Υ ( 4 S ) → η h b ( 1 P ) with the branching fraction B [ Υ ( 4 S ) → η h b ( 1 P ) ] = ( 2.18 ± 0.11 ± 0.18 ) × 10 - 3 and we measure the h b ( 1 P ) mass M h b ( 1 P ) = ( 9899.3 ± 0.4 ± 1.0 ) MeV / c 2 , corresponding to the hyperfine (HF) splitting Δ M HF ( 1 P ) = ( 0.6 ± 0.4 ± 1.0 ) MeV / c 2 . Using the transition h b ( 1 P ) → γ η b ( 1 S ) , we measure the η b ( 1 S ) mass M η b ( 1 S ) = ( 9400.7 ± 1.7 ± 1.6 ) MeV / c 2 , corresponding to Δ M HF ( 1 S ) = ( 59.6 ± 1.7 ± 1.6 ) MeV / c 2 , the η b ( 1 S ) width Γ η b ( 1 S ) = ( 8 - 5 + 6 ± 5 ) MeV / c 2 and the branching fraction B [ h b ( 1 P ) → γ η b ( 1 S ) ] = ( 56 ± 8 ± 4 ) % .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗