Separated cross sections in \pi^0 electroproduction at threshold at Q^2 = 0.05 GeV^2/c^2

The A1 collaboration Weis, M. ; Bartsch, P. ; Baumann, D. ; et al.
Eur.Phys.J.A 38 (2008) 27-33, 2008.
Inspire Record 751930 DOI 10.17182/hepdata.51606

The differential cross sections \sigma_0=\sigma_T+\epsilon \sigma_L, \sigma_{LT}, and \sigma_{TT} of \pi^0 electroproduction from the proton were measured from threshold up to an additional center of mass energy of 40 MeV, at a value of the photon four-momentum transfer of Q^2= 0.05 GeV^2/c^2 and a center of mass angle of \theta=90^\circ. By an additional out-of-plane measurement with polarized electrons \sigma_{LT'} was determined. This showed for the first time the cusp effect above the \pi^+ threshold in the imaginary part of the s-wave. The predictions of Heavy Baryon Chiral Perturbation Theory are in disagreement with these data. On the other hand, the data are somewhat better predicted by the MAID phenomenological model and are in good agreement with the dynamical model DMT.

2 data tables

The separated cross section SIG(0), SIG(LT) and SIG(TT).

Beam helicity asymmetry.


Helicity-dependent cross sections and double-polarization observable E in eta photoproduction from quasi-free protons and neutrons

The A2 collaboration Witthauer, L. ; Dieterle, M. ; Abt, S. ; et al.
Phys.Rev.C 95 (2017) 055201, 2017.
Inspire Record 1589331 DOI 10.17182/hepdata.132013

Precise helicity-dependent cross sections and the double-polarization observable $E$ were measured for $\eta$ photoproduction from quasi-free protons and neutrons bound in the deuteron. The $\eta\rightarrow 2\gamma$ and $\eta\rightarrow 3\pi^0\rightarrow 6\gamma$ decay modes were used to optimize the statistical quality of the data and to estimate systematic uncertainties. The measurement used the A2 detector setup at the tagged photon beam of the electron accelerator MAMI in Mainz. A longitudinally polarized deuterated butanol target was used in combination with a circularly polarized photon beam from bremsstrahlung of a longitudinally polarized electron beam. The reaction products were detected with the electromagnetic calorimeters Crystal Ball and TAPS, which covered 98\% of the full solid angle. The results show that the narrow structure observed earlier in the unpolarized excitation function of $\eta$ photoproduction off the neutron appears only in reactions with antiparallel photon and nucleon spin ($\sigma_{1/2}$). It is absent for reactions with parallel spin orientation ($\sigma_{3/2}$) and thus very probably related to partial waves with total spin 1/2. The behavior of the angular distributions of the helicity-dependent cross sections was analyzed by fitting them with Legendre polynomials. The results are in good agreement with a model from the Bonn-Gatchina group, which uses an interference of $P_{11}$ and $S_{11}$ partial waves to explain the narrow structure.

81 data tables

Diff. cross section for helicity-1/2 at W= 1.505 GeV

Diff. cross section for helicity-1/2 at W= 1.515 GeV

Diff. cross section for helicity-1/2 at W= 1.525 GeV

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K0 production in one prong tau decays

The ALEPH collaboration Buskulic, D. ; Casper, D. ; De Bonis, I. ; et al.
Phys.Lett.B 332 (1994) 219-227, 1994.
Inspire Record 373752 DOI 10.17182/hepdata.68011

From a sample of about 75000 τ decays identified with the ALEPH detector, K 0 production in 1-prong hadronic decays is investigated by tagging the K L 0 component in a hadronic calorimeter. Results are given for the final states ν τ h − K 0 and ν τ h − π 0 K 0 where the h − is separated into π and K contributions by means of the dE / dx measurement in in the central detector. The resulting branching ratios are: ( Bτ → ν τ π − K 0 ) = (0.88±0.14±0.09)%, ( Bτ → ν τ K − K 0 ) = (0.29±0.12±0.03)%, ( Bτ → ν τ π − π 0 K 0 ) = (0.33±0.14±0.07)% aand ( Bτ → ν τ K − π 0 K 0 ) = (0.05±0.05±0.01)%. The K ∗ decay rate in the K 0 π channel agrees with that in the Kπ 0 mode: the combined value for the branching ratio is (Bτ → ν τ K ∗− ) = (1.45±0.13±0.11)% .

1 data table

Invariant mass distribution for the $K^0\pi$ system data. The numbers have been read from the plot in the paper.


One prong tau decays into charged kaons

The ALEPH collaboration Buskulic, D. ; Casper, D. ; De Bonis, I. ; et al.
Phys.Lett.B 332 (1994) 209-218, 1994.
Inspire Record 373751 DOI 10.17182/hepdata.68012

Form a sample of about 75000 τ decays measured in the ALEPH detector, 1-prong charged kaon decays are identified by the dE / dx measurement in the central detector. The resulting branching ratios for the inclusive and exclusive modes are: B ( τ → ν τ K − ≥ 0 π 0 ≥ 0 K 0 ) = (1.60±0.07±0.12)%, B ( τ → ν τ K − = (0.64±0.05±0.05)%, B ( τ → ν τ − π 0 = (0.53±0.05±0.07)% and B ( τ → ν τ K − π 0 π 0 ) = (0.04±0.03±0.02)%. Exclusive modes are corrected for measured K L 0 production. The rate for τ → ν τ K − agrees well with the prediction based on τ - μ universality.

1 data table

Invariant mass distribution of the $K\pi^0$ final state, as obtained from a $dE/dx$ fit in each mass bin. The numbers have been read from the plot in the paper, with the errors simply set to zero if they are smaller than the point size.


Search for single top production in e+ e- collisions at s**(1/2) = 189-GeV - 202-GeV.

The ALEPH collaboration Barate, R. ; Decamp, D. ; Ghez, Philippe ; et al.
Phys.Lett.B 494 (2000) 33-45, 2000.
Inspire Record 533360 DOI 10.17182/hepdata.49857

Single top production via flavour changing neutral currents in the reactions e + e − → t ̄ c / u is searched for in approximately 411 pb −1 of data collected by ALEPH at centre-of-mass energies in the range between 189 and 202 GeV. In total, 58 events are selected in the data to be compared with 50.3 expected from Standard Model backgrounds. No deviation from the Standard Model expectation is observed. Upper limits at 95% CL on single top production cross sections at s =189 –202 GeV are derived. A model-dependent limit on the sum of branching ratios BR(t→Zc)+BR(t→Zu)<17% is obtained.

1 data table

SIG(C=LEPT) and SIG(C=HADR) are the cross sections upper limits evaluated for leptonic and hadronic decay modes of the W-boson, while SIG(C=COMB) are the values obtained by combining the leptonic and hadronic W-boson decay channels. All cross sections values are obtained under assumption of BR(TQ --> W+ BQ) = 100 %.


Measurement of triple gauge boson couplings at LEP energies up to 189-GeV

The ALEPH collaboration Heister, A. ; Schael, S. ; Barate, R. ; et al.
Eur.Phys.J.C 21 (2001) 423-441, 2001.
Inspire Record 555574 DOI 10.17182/hepdata.49832

The triple gauge-boson couplings involving the W are determined using data samples collected with the ALEPH detector at mean centre-of-mass energies of 183 GeV and 189 GeV, corresponding to integrated luminosities of 57 pb^-1 and 174 pb^-1, respectively. The couplings, g^Z_1, Kappa_gamma and lambda_gamma, are measured using W-pair events, single-W production and single-gamma production. Each coupling is measured individually with the other two coupling fixed at their Standard Model value. Including ALEPH results from lower energies, the 95% confidence level intervals for the deviation to the Standard Model are -0.087 < Dg^Z_1 < 0.141 -0.200 < DKappa_gamma < 0.258 -0.062 < Lambda_gamma < 0.147. Fits are also presented where two or all three couplings are allowed to vary. In addition, W-pair events are used to set limits on the C- or P-violating couplings g^V_4, g^V_5, Kappa_V, and Lambda_V, where V denotes either gamma or Z. No deviations from the Standard Model expectations are observed.

4 data tables

The errors included the statistical and systematic uncertainties. Deviation from SM values.

The errors included the statistical and systematic uncertainties. Combined results, lower sqrt(s) data are also included.

The errors included the statistical and systematic uncertainties. Combined results, lower sqrt(s) data are also included. Three-parameter fit.

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Measurements of BR(b --> tau- anti-nu/tau X) and BR(b --> tau- anti-nu/tau D*+- X) and upper limits on BR(B- --> tau- anti-nu/tau) and BR(b --> s nu anti-nu).

The ALEPH collaboration Barate, R. ; Decamp, D. ; Ghez, Philippe ; et al.
Eur.Phys.J.C 19 (2001) 213-227, 2001.
Inspire Record 534887 DOI 10.17182/hepdata.49822

Inclusive branching ratios involving b to tau transitions are measured in approximately four million hadronic Z decays collected by the ALEPH detector at LEP. The fully-inclusive branching ratio b -> tau nu X and the semi-inclusive branching ratio b -> tau nu D*+/- X are measured to be (2.43 +/- 0.20 +/- 0.25)% and (0.88 +/- 0.31 +/- 0.28)%, in agreement with the standard model predictions. Upper limits on the branching fractions b -> tau nu and b -> s nu nubar are set to 8.3 10**-4 and 6.4 10**-4 at the 90% C.L. These results allow a 90% C.L. lower limit of 0.40 (GeV/c**2)**-1 to be set on the tan(beta)/mH+/- ratio, in the framework of type-II two-Higgs-doublet mode

1 data table

TAN(BETA) is the two-Higgs-doublet model parameter, while M_H is the mass of charged Higgs.


Study of the CP asymmetry of B0 ---> J / psi K0(S) decays in ALEPH

The ALEPH collaboration Barate, R. ; Decamp, D. ; Ghez, Philippe ; et al.
Phys.Lett.B 492 (2000) 259-274, 2000.
Inspire Record 533961 DOI 10.17182/hepdata.49841

The decay B0 -> J/psi K0_S is reconstructed with J/psi -> e+ e- or mu+ mu- and K0_S -> pi+ pi-. From the full ALEPH dataset at LEP1 of about 4 million hadronic Z decays, 23 candidates are selected with an estimated purity of 71%. They are used to measure the CP asymmetry of this decay, given by sin 2beta in the Standard Model, with the result sin 2beta = 0.84 +0.82-1.04 +-0.16. This is combined with existing measurements from other experiments, and increases the confidence level that CP violation has been observed in this channel to 98%.

1 data table

Standard Model predicts the time-dependent rate asymmetry as follows: A(t) = (B0(t)-BBAR0(t))/(B0(t)+BBAR0(t)) = SIN(2*BETA)*SIN(Delta(M)*t), where Delta(M) is the mass difference between the two B0 mass eigenstates.


Measurement of the tau polarisation at LEP.

The ALEPH collaboration Heister, A. ; Schael, S. ; Barate, R. ; et al.
Eur.Phys.J.C 20 (2001) 401-430, 2001.
Inspire Record 555653 DOI 10.17182/hepdata.49751

The polarisation of $\tau$'s produced in Z decay is measured using 160 pb$^{-1}$ of data accumulated at LEP by the ALEPH detector between 1990 and 1995. The variation of the polarisation with polar angle yields the two parameters ${\cal A}_e = 0.1504 \pm 0.0068 $ and ${\cal A}_{\tau} = 0.1451 \pm 0.0059$ which are consistent with the hypothesis of $e$-$\tau$ universality. Assuming universality, the value ${\cal A}_{e{-}\tau} = 0.1474 \pm 0.0045$ is obtained from which the effective weak mixing angle $\sin^2 {\theta_{\mathrm{W}}^{\mathrm{eff}}} =0.23147 \pm 0.00057 $ is derived.

1 data table

No description provided.


Study of hadronic final states from double tagged gamma gamma events at LEP.

The ALEPH collaboration Heister, A. ; Schael, S. ; Barate, R. ; et al.
CERN-EP-2003-025, 2003.
Inspire Record 619958 DOI 10.17182/hepdata.49702

The interaction of virtual photons is investigated using double tagged gammagamma events with hadronic final states recorded by the ALEPH experiment at e^+e^- centre-of-mass energies between 188 and 209 GeV. The measured cross section is compared to Monte Carlo models, and to next-to-leading-order QCD and BFKL calculations.

10 data tables

Differential cross section as a function of the relative energy of the scattered electrons.

Differential cross section as a function of the polar angle THETA of the scattered electrons.

Differential cross section as a function of the virtuality Q**2 of the photons.

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