575 research outputs found
Λ hyperon spin polarization and CP tests at BESIII
No full textIn these proceedings two preliminary results from the BESIII collaboration on polarized Λ and Λ¯ are reported. Both results are first observations and concern the resonant and non-resonant processes e−e+→J/ψ→ΛΛ¯ and e−e+→γ*→ΛΛ¯ at s=2.396 GeV, respectively. For J/ψ→ΛΛ¯ the relative phase between the electric and magnetic form factors, ΔΦ, has for the first time been determined, ΔΦ=42.4(6)stat(5)syst°\Delta \Phi = 42.4{(6)_{{\rm{stat}}}}(5)_{_{{\rm{syst}}}}^^\circ. That ΔΦ≠0 allows for a simultaneous measurement also of the asymmetry decay parameters Λ→pπ− (α−), Λ¯→p¯π+ (α+) and Λ¯→n¯π0 (α¯0). The measured value of α−=0.750±0.009±0.004 differs by 17(3)% from the PDG value. The simultaneous measurement for the asymmetry parameters allows for the most precise test of CP violation conducted for Λ decays, ACP = −0.006(12)stat(7)syst. The reaction e−e+→ΛΛ¯ at s=2.396 GeV is the first complete measurement of the time-like electric (GE) and magnetic (GM) form factor of any baryon as also the ratio R = |(GE/(GM)| and ΔΦ have been determined: R = 0.96(14)(12) and ΔΦ=37(12)stat(6)stat°. The obtained cross-section and effective form factor are σ = 119.0(53)stat(51)syst pb and |G| = 0.123(3)stat(3)syst, respectively
Lambda hyperon spin polarization and CP tests at BESIII
No full textIn these proceedings two preliminary results from the BESIII collaboration on polarized Lambda and (Lambda) over bar are reported. Both results are first observations and concern the resonant and non-resonant processes e(-)e(+) -> J/psi -> Lambda(Lambda) over bar and e(-)e(+) -> gamma* -> Lambda Lambda at root s = 2.396 GeV, respectively. For J/psi -> Lambda Lambda the relative phase between the electric and magnetic form factors, Delta Phi, has for the first time been determined, Delta Phi = 42.4(6)(stat) (5)(stat degrees). That Delta Phi not equal 0 allows for a simultaneous measurement also of the asymmetry decay parameters Lambda -> p pi(-) (alpha_), (Lambda) over bar -> (p) over bar pi(+) (alpha(+)) and (Lambda) over bar -> (n) over bar pi(0) ((alpha) over bar (0)). The measured value of alpha_ = 0.750 +/- 0.009 +/- 0.004 differs by 17(3)% from the PDG value. The simultaneous measurement for the asymmetry parameters allows for the most precise test of CP violation conducted for A decays, A(cp) = - 0.006(12)(stat) (7)(syst). The reaction e(-)e(+) -> Lambda(Lambda) over bar at root s = 2.396 GeV is the first complete measurement of the time-like electric (G(E)) and magnetic (G(M)) form factor of any baryon as also the ratio R = vertical bar(GE)/(G(M))vertical bar and Delta Phi have been determined: R = 0.96(14)(12) and Delta Phi = 37(12)(stat) (6)(stat)degrees. The obtained cross-section and effective form factor are sigma = 119.0(53)(stat)(51)(syst) pb and vertical bar G vertical bar = 0.123 (3)(stat) (3)(syst), respectively
Study of hc → 3(π+ π- )π0, hc → (π+ π-) ω, hc → 2(π+ π-)π0η, hc → 2(π+ π -) η, and hc → p‾p
No full textBased on (2712.4±14.1)×106 (3686) events collected with the BESIII detector, we study the decays ℎ→3(+−)0, ℎ→2(+−), ℎ→2(+−)0, ℎ→2(+−), and ℎ→¯via (3686)→0ℎ. The decay channel ℎ→3(+−)0 is observed for the first time, and its branching fraction is determined to be (9.28±1.14±0.77)×10−3, where the first uncertainty is statistical and the second is systematic. In addition, first evidence is found for the modes ℎ→2(+−)0 and ℎ→2(+−) with significances of 4.8 and 4.7, and their branching fractions are determined to be (7.55±1.51±0.77)×10−3 and (4.00±0.86±0.35)×10−3, respectively. No significant signals of ℎ→2(+−) and ℎ→¯are observed, and the upper limits of the branching fractions of these decays are determined to be <6.19×10−4 and <4.40×10−5 at the 90% confidence level, respectively.For complete list of authors see http://dx.doi.org/10.1103/PhysRevD.109.072018</p
Observation of the Anomalous Shape of X(1840) in J/Ï\u88 â\u86\u92 γ3(Ï\u80+ Ï\u80-) Indicating a Second Resonance Near p(p)over-bar Threshold
No full textUsing a sample of (10087 +/- 44) x 10(6) J/psi events, which is about 45 times larger than that was previously analyzed, a further investigation on the J/psi -> gamma 3(pi(+) pi(-)) decay is performed. A significant distortion at 1.84 GeV/c(2) in the line shape of the 3(pi(+) pi(-)) invariant mass spectrum is observed for the first time, which could be resolved by two overlapping resonant structures, X(1840) and X(1880). The new state X(1880) is observed with a statistical significance larger than 10 sigma. The mass and width of X(1880) are determined to be 1882.1 +/- 1.7 +/- 0.7 MeV/c(2) and 30.7 +/- 5.5 +/- 2.4 MeV, respectively, which indicates the existence of a p (p) over bar bound state.For complete list of authors see http://dx.doi.org/10.1103/PhysRevLett.132.151901</p
MEASUREMENT OF dd -> (3)He p pi(-) WITH WASA-at-COSY
No full textThe measurment of the charge symmetry conserving reactions dd -> (3)He p pi(-) and dd -> (3)He n pi(0) is the first step of the charge symmetry breaking physics program with WASA-at-COSY. The analysis of these channels helps to understand the experimental conditions and provides additional parameters for theoretical studies. The data have been collected in November 2007.</p
Observation of eta(c)(2S) -> 3(pi(+)pi(-)) and measurements of chi(cJ) -> 3(pi(+)pi(-)) in psi (3686) radiative transitions
No full textThe hadronic decay eta(c) (2S) -> 3 (pi(+)pi(-)) is observed with a statistical significance of 9.3 standard deviations using (448.1 +/- 2.9) x 10(6) psi(3686) events collected by the BESIII detector at the BEPCII collider. The measured mass and width of eta(c) (2S) are (3643.4 +/- 2.3 (stat) +/- 4.4 (syst)) MeV/c(2) and 19.8 +/- 3.9 (stat) +/- 3.1 (syst)) MeV, respectively, which are consistent with the world average values within two standard deviations. The product branching fraction B[psi(3686) -> gamma eta(c) (2S)] X B[eta(c)(2S) -> 3(pi(+)pi(-))] is measured to be (9.2 +/- 1.0(stat)+/- 1.2(syst)10(-6). Using B[psi(3686) -> gamma eta(c) (2S)] = (7.0(-2.5)(+3.4)) x 10(-4), we obtain B[eta(c)(2S) -> 3 (pi(+)pi(-))] = (1.31 +/- 0.15 (stat) +/- 0.17 (syst) ((+0.64)(-0.47)) (extr))x 10(-2), where the third uncertainty is from B [psi(3686)->gamma eta(c)(2S)]. We also measure the chi(cJ)-> 3(pi(+)pi(-)) (J = 0, 1, 2) decays via psi' -> gamma chi(cJ) transitions. The branching fractions are B[chi(c0) 3(pi(+)pi(-))] = (2.080 +/- 0.006(stat)+/- 0.068(syst))x10(-2), B [chi c(2) -> (pi(+)pi(-))]=1.092 x 0.004(stat)+/- 0.035(syst))x10(-2), and B[chi(C2) -> 3 (pi(+)pi(-))] = 1.565 +/- 0.005 (stat) +/- 0.048 (syst)) x 10(-2).For complete list of authors see http://dx.doi.org/10.1103/PhysRevD.106.032014</p
Measurement of e plus e- ? : ?p plus p - cross sections at center-of-mass energies from 2.00 to 3.08 GeV
No full textUsing data corresponding to an integrated luminosity of 651 pb-1 accumulated at 22 center-of-mass energies from 2.00 to 3.08 GeV by the BESIII experiment, the process e+e- & RARR; 0ic+ic- is studied. The cross sections for e+e- & RARR; 0ic+ic- are consistent with previous results, but with improved precision. To measure the mass and width of the structure observed in the cross section line shape, a combine fit is performed after enhancing the contribution from 0f0(980). The fit reveals a structure with the mass of M = 2178 +20 +5 MeV=c2 and the width of & UGamma; = 140 +36 +16 MeV, where the first uncertainties are statistical and the second ones are systematic.For complete list of authors see http://dx.doi.org/10.1103/PhysRevD.108.032011</p
Observation of χcJ → 3( K+ K-)
No full textBy analyzing (27.12 ± 0.14) x 108 Ψ(3686) events collected with the BESIII detector operating at the BEPCII collider, the decay processes χcJ → 3(K+ K-) (J = 0, 1, 2) are observed for the first time with statistical significances of 8.2σ, 8.1σ, and 12.4σ, respectively. The product branching fractions of Ψ(3686) → γχcJ , χcJ → 3(K+K-) are presented and the branching fractions of χcJ → 3(K+K-) decays are determined to be Bχc0 → 3(K+K-) = (10.7 ± 1.8 ± 1.1) x 10-6, Bχc1 →3(K+K-) = (4.2 ± 0.9 ± 0.5) x 10-6, and Bχc2 → 3(K+K-) = (7.2 ± 1.1 ± 0.8) x 10-6, where the first uncertainties are statistical and the second are systematic.For complete list of authors see http://dx.doi.org/10.1103/PhysRevD.109.072016</p
Measurements of the branching fractions of the P-wave charmonium spin-singlet state hc(1P1) →\u86\u92 h+h-π\u800/η
No full textBased on (2712.4 ± 14.3) x 106 ψ(3686) events, we investigate four hadronic decay modes of the P-wave charmonium spin-singlet state hc(1P1) → h+h-π0/η(h =π or K) via the process ψ(3686) → π0hc at BESIII. The hc → π+π-π0 decay is observed with a significance of 9.6σ after taking into account systematic uncertainties. Evidences for hc → K+K-π0 and hc → K+K-η are found with significances of 3.5σ and 3.3σ, respectively, after considering the systematic uncertainties. The branching fractions of these decays are measured to be B(hc → π+π-π0) = (1.36 ± 0.16 ± 0.14)x10-3, B(hc → K+K-π0) = (3.26 ± 0.84 ± 0.36) x 10-4, and B(hc → K+K-η) = (3.13 ± 1.08 ± 0.38) x 10-4, where the first uncertainties are statistical and the second are systematic. No significant signal of hc → π+π-η is found, and the upper limit of its decay branching fraction is determined to be B(hc → π+π-η) < 4.0 x 10-4 at the 90% confidence level.For complete list of authors see http://dx.doi.org/10.1103/PhysRevD.110.032023</p
Measurement of the absolute branching fraction of the inclusive decay Ds plus ? p plus p plus p-X
No full textUsing an e thorn e- collision data sample with a total integrated luminosity of 3.19 fb-1 collected with the BESIII detector at a center-of-mass energy of 4.178 GeV, the branching fraction of the inclusive decay of the D thorn s meson to final states including at least three charged pions is measured for the first time to be BoD thorn s & RARR; & pi; thorn & pi; thorn & pi;-X thorn 1/4 o32.81 â \u820.35stat â \u820.63syst thorn %. In this measurement the charged pions from K0S meson decays are excluded. The partial branching fractions of D thorn s & RARR;& pi; thorn & pi; thorn & pi;-X are also measured as a function of the & pi; thorn & pi; thorn & pi;- invariant mass.For complete list of authors see http://dx.doi.org/10.1103/PhysRevD.108.032001</p
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