491 research outputs found
Measurement of the mass difference m(B-0)-m(B+)
No full textUsing 230 x 10(6) B (B) over bar events recorded with the BABAR detector at the e(+)e(-) storage rings PEP-II, we reconstruct approximately 4100 B-0 -> J/psi K+pi(-) and 9930 B+ -> J/psi K+ decays with J/psi -> mu(+)mu(-) and e(+)e(-). From the measured B-momentum distributions in the e(+)e(-) rest frame, we determine the mass difference m(B-0) - m(B+) = (+0.33 +/- 0.05 +/- 0.03) MeV/c(2)
Measurement of Collins asymmetries in inclusive production of charged pion pairs in e+e− annihilation at BABAR
Get PDFWe present measurements of Collins asymmetries in the inclusive process e+e−→ππX, where π stands for charged pions, at a center-of-mass energy of 10.6 GeV. We use a data sample of 468 fb−1 collected by the BABAR experiment at the PEP-II B factory at SLAC, and consider pairs of charged pions produced in opposite hemispheres of hadronic events. We observe clear asymmetries in the distributions of the azimuthal angles in two distinct reference frames. We study the dependence of the asymmetry on several kinematic variables, finding that it increases with increasing pion momentum and momentum transverse to the analysis axis, and with increasing angle between the thrust and beam axis
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Search for a Low-mass Higgs Boson in Y(3S)--> gamma A^0, A^0--> tau^ tau^- at BABAR
No full textWe search for a light Higgs boson A{sup 0} in the radiative decay Y(3S) {yields} {gamma}A{sup 0}, A{sup 0} {yields} T{sup +}T{sup -}, T{sup +} {yields} e{sup +}{nu}{sub e}{nu}{sub T}, or T{sup +} {yields} {mu}{sup +} {nu}{sub {mu}T}. The data sample contains 122 x 10{sup 6} Y(3S) events recorded with the BABAR detector. We find no evidence for a narrow structure in the studied T{sup +}T{sup -} invariant mass region of 4.03 < m{sub T{sup +}T{sup -}} < 10.10 GeV/c{sup 2}. We exclude at the 90% confidence level (C.L.) a low-mass Higgs boson decaying to T{sup +}T{sup -} with a product branching fraction B(Y(3S) {yields} {gamma}A{sup 0}) x B(A{sup 0} {yields} T{sup +}T{sup -}) > (1.5-16) x 10{sup -5} across the mT{sup +}T{sup -} range. We also set a 90% C.L. upper limit on the T{sup +}T{sup -} decay of the {eta}{sub b} at B({eta}{sub b} {yields} T{sup +}T{sup -}) < 8%
Measurements of the tau mass and the mass difference of the tau(+) and tau(-) at BABAR
Get PDFWe present the result from a precision measurement of the mass of the tau lepton, M-tau, based on 423 fb(-1) of data recorded at the Upsilon(4S) resonance with the BABAR detector. Using a pseudomass endpoint method, we determine the mass to be 1776.68 +/- 0.12(stat)+/- 0.41(syst) MeV. We also measure the mass difference between the tau(+) and tau(-), and obtain (M-tau(+)-M-tau(-))/M-AVG(tau)=(-3.4 +/- 1.3(stat)+/- 0.3(syst))x10(-4), where M-AVG(tau) is the average value of M-tau(+) and M-tau(-)
A ZEUS next-to-leading-order QCD analysis of data on deep inelastic scattering
Get PDFNext-to-leading-order QCD analyses of the ZEUS data on deep inelastic scattering together with fixed-target data have been performed, from which the gluon and quark densities of the proton and the value of the strong coupling constant alpha <sub>s</sub> (M<sub> Z</sub>) were extracted. The study includes a full treatment of the experimental systematic uncertainties including point-to-point correlations. The resulting uncertainties in the parton density functions are presented. A combined fit for alpha <sub>s</sub> (M<sub> Z</sub>) and the gluon and quark densities yields a value for alpha <sub>s</sub> (M<sub> Z</sub>) in agreement with the world average. The parton density functions derived from ZEUS data alone indicate the importance of HERA data in determining the sea quark and gluon distributions at low x. The limits of applicability of the theoretical formalism have been explored by comparing the fit predictions to ZEUS data at very low Q<sup> 2</sup>
Search for a low-mass Higgs Boson in upsilon(3S) -> gamma A(0), A(0) -> tau(+) tau(-) at BABAR
Get PDFWe search for a light Higgs boson A(0) in the radiative decay Upsilon(3S) -> gamma A(0), A(0) -> tau(+) tau(-), tau(+) -> e(+) nu(e)(nu) over bar (tau) or tau(+) -> mu(+) nu(mu)(nu) over bar (tau) . The data sample contains 122 X 10(6) Upsilon(3S) events recorded with the BABAR detector. We find no evidence for a narrow structure in the studied tau(+) tau(-) invariant mass region of 4.03 A(0)) B(A(0) -> tau(+) tau(-)) > (1.5 - 16) X 10(-5) across the m(tau+ tau-) range. We also set a 90% C. L. upper limit on the tau(+) tau(-) decay of the eta(b) at B(eta(b) -> tau(+) tau(-)) < 8%
Measurement of the mass and width of the D_{s1}(2536)^{+} meson
Get PDFThe decay width and mass of the Ds1(2536)+ meson are measured via the decay channel Ds1+→D*+KS0 using 385 fb-1 of data recorded with the BABAR detector in the vicinity of the Υ(4S) resonance at the PEP-II asymmetric-energy electron-positron collider. The result for the decay width is Γ(Ds1+)=0.92±0.03(stat.)±0.04(syst.) MeV. For the mass, a value of m(Ds1+)=2535.08±0.01(stat.)±0.15(syst.) MeV/c2 is obtained. The mass difference between the Ds1+ and the D*+ is measured to be m(Ds1+)-m(D*+)=524.83±0.01(stat.)±0.04(syst.) MeV/c2, representing a significant improvement compared to the current world average. The unnatural spin-parity assignment for the Ds1+ meson is confirme
Search for di-muon decays of a low-mass Higgs boson in radiative decays of the Υ(1S)
Get PDFWe search for di-muon decays of a low-mass Higgs boson (A[superscript 0]) produced in radiative Υ(1S) decays. The Υ(1S) sample is selected by tagging the pion pair in the Υ(2S,3S)→π[superscript +]π[superscript -]Υ(1S) transitions, using a data sample of 92.8×10[superscript 6] Υ(2S) and 116.8×10[superscript 6] Υ(3S) events collected by the BABAR detector. We find no evidence for A[superscript 0] production and set 90% confidence level upper limits on the product branching fraction B(Υ(1S)→γA[superscript 0])×B(A[superscript 0]→μ[superscript +]μ[superscript -]) in the range of (0.28-9.7)×10[superscript -6] for 0.212≤m[subscript A][superscript 0]≤9.20 GeV/c[superscript 2]. The results are combined with our previous measurements of Υ(2S,3S)→γA[superscript 0], A[superscript 0]→μ[superscript +]μ[superscript -] to set limits on the effective coupling of the b quark to the A[superscript 0].United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio
Measurement of the Branching Fractions of B̅ →D**l-ν̅ l Decays in Events Tagged by a Fully Reconstructed B Meson
No full textWe report a measurement of the branching fractions of B̅ →D**l-ν̅ l decays based on 417 fb-1 of data collected at the Υ(4S) resonance with the BABAR detector at the PEP-II e+e- storage rings. Events are selected by fully reconstructing one of the B mesons in a hadronic decay mode. A fit to the invariant mass differences m(D(*)π)-m(D(*)) is performed to extract the signal yields of the different D** states. We observe the B̅ →D**l-ν̅ l decay modes corresponding to the four D** states predicted by heavy quark symmetry with a significance greater than 5 standard deviations including systematic uncertainties
Study of B̅ →Xuℓν̅ decays in BB̅ events tagged by a fully reconstructed B-meson decay and determination of |V[subscript ub]|
Get PDFWe report measurements of partial branching fractions for inclusive charmless semileptonic B decays B̅ →Xuℓν̅ and the determination of the Cabibbo–Kobayashi–Maskawa (CKM) matrix element |Vub|. The analysis is based on a sample of 467×10[superscript 6] Υ(4S)→BB̅ decays recorded with the BABAR detector at the PEP-II e[superscript +]e[superscript -] storage rings. We select events in which the decay of one of the B mesons is fully reconstructed and an electron or a muon signals the semileptonic decay of the other B meson. We measure partial branching fractions ΔB in several restricted regions of phase space and determine the CKM element |V[subscript ub]| based on different QCD predictions. For decays with a charged lepton momentum p[subscript ℓ][superscript *]>1.0 GeV in the B meson rest frame, we obtain ΔB=(1.80±0.13[subscript stat]±0.15[subscript sys]±0.02[subscript theo])×10[superscript -3] from a fit to the two-dimensional M[subscript X]-q[superscript 2] distribution. Here, M[subscript X] refers to the invariant mass of the final state hadron X and q[superscript 2] is the invariant mass squared of the charged lepton and neutrino. From this measurement we extract |V[subscript ub]|=(4.33±0.24[subscript exp]±0.15[subscript theo])×10[superscript -3] as the arithmetic average of four results obtained from four different QCD predictions of the partial rate. We separately determine partial branching fractions for B̅[superscript 0] and B[superscript -] decays and derive a limit on the isospin breaking in B̅→X[subscript u]ℓν̅ decays
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