R. Chistov

Study of the decays B{yields}D{sub s1}(2536){sup +}D{sup (*)}

We report a study of the decays B{yields}D{sub s1}(2536){sup +}D{sup (*)}, where D{sup (*)} is D{sup 0}, D{sup -} or D*{sup -}, using a sample of 657x10{sup 6}BB pairs collected at the {Upsilon}(4S) resonance with the Belle detector at the KEKB asymmetric-energy e{sup +}e{sup -} collider. The branching fractions of the decays B{sup +}{yields}D{sub s1}(2536){sup +}D{sup 0}, B{sup 0}{yields}D{sub s1}(2536){sup +}D{sup -} and B{sup 0}{yields}D{sub s1}(2536){sup +}D{sup *-} multiplied by that of D{sub s1}(2536){sup +}{yields}(D*{sup 0}K{sup +}+D*{sup +}K{sup 0}) are found to be (3.97{+-}0.85{+-}0.56)x10{sup -4}, (2.75{+-}0.62{+-}0.36)x10{sup -4} and (5.01{+-}1.21{+-}0.70)x10{sup -4}, respectively. The ratio B(D{sub s1}{yields}D*{sup 0}K{sup +})/B(D{sub s1}{yields}D*{sup +}K{sup 0}) is measured to be 0.88{+-}0.24{+-}0.08.We report a study of the decays B -> D-s1(2536)+ (D) over bar (()*()), where (D) over bar (()*()) is (D) over bar (0), D- or D*(-), using a sample of 657 x 10(6)B (B) over bar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The branching fractions of the decays B+ -> D-s1(2536)(+) (D) over bar (0), B-0 -> D-s1(2536)D-+(-) and B-0 -> D-s1(2536)D+*(-) multiplied by that of D-s1(2536)(+) -> (D*K-0(+) + D*K-+(0)) are found to be (3.97 +/- 0.85 +/- 0.56) x 10(-4), (2.75 +/- 0.62 +/- 0.36) x 10(-4) and (5.01 +/- 1.21 +/- 0.70) x 10(-4), respectively. The ratio B(D-s1 -> D*K-0(+))/B(D-s1 -> D*K-+(0)) is measured to be 0.88 +/- 0.24 +/- 0.08.

Measurement of e{sup +}e{sup -}{yields}D{sub s}{sup (*)+}D{sub s}{sup (*)-} cross sections near threshold using initial-state radiation

We report a measurement of exclusive e(+)e(-) -> Ds(*)+Ds(*)- cross sections as a function of center-of-mass energy near the Ds(*)+Ds(*)- threshold with initial-state radiation. The analysis is based on a data sample collected with the Belle detector with an integrated luminosity of 967 fb(-1).

Measurement of the e{sup +}e{sup -}{yields}D{sup 0}D*{sup -}{pi}{sup +} cross section using initial-state radiation

We report measurements of the exclusive cross section for e{sup +}e{sup -}{yields}D{sup 0}D*{sup -}{pi}{sup +} as a function of center-of-mass energy from the D{sup 0}D*{sup -}{pi}{sup +} threshold to 5.2 GeV with initial-state radiation. No evidence is found for Y(4260){yields}D{sup 0}D*{sup -}{pi}{sup +} decays. The analysis is based on a data sample collected with the Belle detector at or near a center-of-mass energy of 10.58 GeV with an integrated luminosity of 695 fb{sup -1} at the KEKB asymmetric-energy e{sup +}e{sup -} collider.

Measurement of the e{sup +}e{sup -}{yields}J/{psi}cc cross section at {radical}(s){approx_equal}10.6 GeV

We present a new measurement of the e{sup +}e{sup -}{yields}J/{psi}cc cross section where the cc pair can fragment either into charmed hadrons or a charmonium state. In the former case the J/{psi} and a charmed hadron are reconstructed, while the latter process is measured using the recoil mass technique, which allows the identification of two-body final states without reconstruction of one of the charmonia. The measured e{sup +}e{sup -}{yields}J/{psi}cc cross section is (0.74{+-}0.08(+0.09/-0.08)) pb, and the e{sup +}e{sup -}{yields}J/{psi}X{sub non-cc} cross section is (0.43{+-}0.09{+-}0.09) pb. We note that the measured cross sections are obtained from a data sample with the multiplicity of charged tracks in the event larger than 4; corrections for the effect of this requirement are not performed as this cannot be done in a model-independent way. The analysis is based on a data sample with an integrated luminosity of 673 fb{sup -1} recorded near the {upsilon}(4S) resonance with the Belle detector at the KEKB e{sup +}e{sup -} asymmetric-energy collider.

Production of New Charmoniumlike States in e{sup +}e{sup -}{yields}J/{psi}D{sup (*)}D{sup (*)} at {radical}(s){approx_equal}10.6 GeV

We report a study of the processes e{sup +}e{sup -}{yields}J/{psi}D{sup (*)}D{sup (*)}. In J/{psi}D*D* we observe a significant enhancement in the D*D* invariant mass spectrum, which we interpret as a new charmoniumlike state and denote X(4160). The X(4160) parameters are M=(4156{sub -20}{sup +25}{+-}15) MeV/c{sup 2} and {gamma}=(139{sub -61}{sup +111}{+-}21) MeV. We also report a new measurement of the X(3940) mass and width: M=(3942{sub -6}{sup +7}{+-}6) MeV/c{sup 2} and {gamma}=(37{sub -15}{sup +26}{+-}8) MeV. The analysis is based on a 693 fb{sup -1} data sample recorded near the {upsilon}(4S) resonance by the Belle detector at the KEKB asymmetric-energy collider.We report a study of the processes e+e-→J/ψD(*)D(*). In J/ψD*D* we observe a significant enhancement in the D*D* invariant mass spectrum, which we interpret as a new charmoniumlike state and denote X(4160). The X(4160) parameters are M=(4156-20+25±15)MeV/c2 and Γ=(139-61+111±21)MeV. We also report a new measurement of the X(3940) mass and width: M=(3942-6+7±6) MeV/c2 and Γ=(37-15+26±8)MeV. The analysis is based on a 693fb-1 data sample recorded near the Υ(4S) resonance by the Belle detector at the KEKB asymmetric-energy collider.

Observation of a Near-Threshold Enhancement in the e{sup +}e{sup -}{yields}{lambda}{sub c}{sup +}{lambda}{sub c}{sup -} Cross Section Using Initial-State Radiation

We report a measurement of the exclusive e+ e- -->Lambda+_(c)Lambda-_(c) cross section as a function of center-of-mass energy near the Lambda+_(c)Lambda-_(c) threshold. A clear peak with a significance of 8.2sigma is observed in the Lambda+_(c)Lambda-_(c) invariant mass distribution just above threshold. With an assumption of a resonance origin for the observed peak, a mass and width of M=[4634 (+8)_(-7)(stat)(+5)_(-8)(syst)] MeV/c(2) and Gamma_(tot)=[92 (+40)_(-24)(stat)(+10)_(-21)(syst)] MeV are determined. The analysis is based on a study of events with initial-state-radiation photons in a data sample collected with the Belle detector at the Upsilon(4S) resonance and nearby continuum with an integrated luminosity of 695 fb(-1) at the KEKB asymmetric-energy e+ e- collider.

Observation of two resonancelike structures in the {pi}{sup +}{chi}{sub c1} mass distribution in exclusive B{sup 0}{yields}K{sup -}{pi}{sup +}{chi}{sub c1} decays

We report the first observation of two resonance-like structures in the pi+ chi_c1 invariant mass distribution near 4.1 GeV/c^2 in exclusive B0-bar --> K- pi+ chi_c1 decays. From a Dalitz plot analysis in which the pi+ chi_c1 mass structures are represented by Breit-Wigner resonance amplitudes, we determine masses and widths of: M_1 = (4051 +-14 +20-41) MeV/c^2, Gamma_1 = (82 +21-17 +47-22) MeV, M_2 = (4248 +44-29 +180-35}) MeV/c^2, and Gamma_2 =(177 +54-39 +316-61) MeV/ and product branching fractions of BF(B0-bar --> K- Z+_1,2) x BF(Z+_1,2 --> pi+ chi_c1) = (3.0 +1.5-0.8 +3.7-1.6) x 10^-5 and (4.0 +2.3-0.9 +19.7-0.5) x 10^-5 respectively. Here the first uncertainty is statistical, the second is systematic. The significance of each of the pi+ chi_c1 structures exceeds 5 sigma, including the effects of systematics from various fit models. This analysis is based on 657 x 10^6 BB-bar events collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.Reference EPFL-ARTICLE-154418doi:10.1103/PhysRevD.78.072004View record in Web of Science Record created on 2010-11-05, modified on 2017-12-10We report the first observation of two resonancelike structures in the {pi}{sup +}{chi}{sub c1} invariant mass distribution near 4.1 GeV/c{sup 2} in exclusive B{sup 0}{yields}K{sup -}{pi}{sup +}{chi}{sub c1} decays. From a Dalitz plot analysis in which the {pi}{sup +}{chi}{sub c1} mass structures are represented by Breit-Wigner resonance amplitudes, we determine masses and widths of: M{sub 1}=(4051{+-}14{sub -41}{sup +20}) MeV/c{sup 2}, {gamma}{sub 1}=(82{sub -17-22}{sup +21+47}) MeV, M{sub 2}=(4248{sub -29-35}{sup +44+180}) MeV/c{sup 2}, and {gamma}{sub 2}=(177{sub -39-61}{sup +54+316}) MeV; and product branching fractions of B(B{sup 0}{yields}K{sup -}Z{sub 1,2}{sup +})xB(Z{sub 1,2}{sup +}{yields}{pi}{sup +}{chi}{sub c1})=(3.0{sub -0.8-1.6}{sup +1.5+3.7})x10{sup -5} and (4.0{sub -0.9-0.5}{sup +2.3+19.7})x10{sup -5}, respectively. Here the first uncertainty is statistical, the second is systematic. The significance of each of the {pi}{sup +}{chi}{sub c1} structures exceeds 5{sigma}, including the systematic uncertainty from various fit models. This analysis is based on 657x10{sup 6} BB events collected at the {upsilon}(4S) resonance with the Belle detector at the KEKB asymmetric-energy e{sup +}e{sup -} collider.

Observation of D{sub s1}(2536){sup +}{yields}D{sup +}{pi}{sup -}K{sup +} and angular decomposition of D{sub s1}(2536){sup +}{yields}D*{sup +}K{sub S}{sup 0}

Using 462 fb{sup -1} of e{sup +}e{sup -} annihilation data recorded by the Belle detector, we report the first observation of the decay D{sub s1}(2536){sup +}{yields}D{sup +}{pi}{sup -}K{sup +}. The ratio of branching fractions (B(D{sub s1}(2536){sup +}{yields}D{sup +}{pi}{sup -}K{sup +})/B(D{sub s1}(2536){sup +}{yields}D*{sup +}K{sup 0})) is measured to be (3.27{+-}0.18{+-}0.37)%. We also study the angular distributions in the D{sub s1}(2536){sup +}{yields}D*{sup +}K{sub S}{sup 0} decay and measure the ratio of D- and S-wave amplitudes. The S-wave dominates, with a partial width of {gamma}{sub S}/{gamma}{sub total}=0.72{+-}0.05{+-}0.01.Using 462fb-1 of e+e- annihilation data recorded by the Belle detector, we report the first observation of the decay Ds1(2536)+→D+π-K+. The ratio of branching fractions B(Ds1(2536)+→D+π-K+)B(Ds1(2536) +→D*+K0) is measured to be (3.27±0.18±0.37)%. We also study the angular distributions in the Ds1(2536)+→D*+KS0 decay and measure the ratio of D- and S-wave amplitudes. The S-wave dominates, with a partial width of ΓS/Γtotal=0.72±0.05±0.01.

Measurement of the Near-Threshold e{sup +}e{sup -}{yields}D{sup (*){+-}}D{sup (*){+-}} Cross Section using Initial-State Radiation

Reference EPFL-ARTICLE-154441doi:10.1103/PhysRevLett.98.092001View record in Web of Science Record created on 2010-11-05, modified on 2017-12-10

Observation of the decay B{sup 0}{yields}D{sub s}{sup +}{lambda}p

We report the first observation of the decay B0→Ds+Λ p with a statistical significance of 6.6σ. We measure B(B0→Ds+Λp)=(2.9±0.7±0.5±0.4) ×10-5, where the first error is statistical, the second is systematic, and the third error comes from the uncertainty in B(Ds+→π+). The data used for this analysis was accumulated at the Υ(4S) resonance, using the Belle detector at the KEKB asymmetric-energy e+e- collider. The integrated luminosity of the data sample is 414fb-1, corresponding to 449×106 BB pairs.