Date

Measurement of the Prompt $J/\psi$ and $\psi$(2S) Polarizations in $pp$ Collisions at $\sqrt{s}$ = 7 TeV

The CMS collaboration Chatrchyan, Serguei ; Khachatryan, Vardan ; Sirunyan, Albert M ; et al.
Phys.Lett.B 727 (2013) 381-402, 2013.
Inspire Record 1244128 DOI 10.17182/hepdata.63898

The polarizations of prompt J/psi and psi(2S) mesons are measured in proton-proton collisions at sqrt(s) = 7 TeV, using a dimuon data sample collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 4.9 inverse femtobarns. The prompt J/psi and psi(2S) polarization parameters lambda[theta], lambda[phi], and lambda[theta,phi], as well as the frame-invariant quantity lambda(tilde), are measured from the dimuon decay angular distributions in three different polarization frames. The J/psi results are obtained in the transverse momentum range 14 < pt < 70 GeV, in the rapidity intervals abs(y) < 0.6 and 0.6 < abs(y) < 1.2. The corresponding psi(2S) results cover 14 < pt < 50 GeV and include a third rapidity bin, 1.2 < abs(y) < 1.5. No evidence of large transverse or longitudinal polarizations is seen in these kinematic regions, which extend much beyond those previously explored.

60 data tables

Lambda-Theta in the CS frame for the J/psi as a function of pT for 0.0 < |y| < 0.6.

Lambda-Theta in the CS frame for the J/psi as a function of pT for 0.6 < |y| < 1.2.

Lambda-Phi in the CS frame for the J/psi as a function of pT for 0.0 < |y| < 0.6.

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Measurement of the Y1S, Y2S and Y3S polarizations in pp collisions at sqrt(s) = 7 TeV

The CMS collaboration Chatrchyan, Serguei ; Khachatryan, Vardan ; Sirunyan, Albert M ; et al.
Phys.Rev.Lett. 110 (2013) 081802, 2013.
Inspire Record 1185414 DOI 10.17182/hepdata.60126

The polarizations of the Y(1S), Y(2S), and Y(3S) mesons are measured in proton-proton collisions at sqrt(s) = 7 TeV, using a data sample of Y(nS) to oppositely charged muon pair decays collected by the CMS experiment, corresponding to an integrated luminosity of 4.9 inverse femtobarns. The dimuon decay angular distributions are analyzed in three different polarization frames. The polarization parameters lambda[theta], lambda[phi], and lambda[theta,phi], as well as the frame-invariant quantity lambda-tilde, are presented as a function of the Y(nS) transverse momentum between 10 and 50 GeV, in the rapidity ranges abs(y) < 0.6 and 0.6 < abs(y) < 1.2. No evidence of large transverse or longitudinal polarizations has been seen in the explored kinematic region.

75 data tables

Distribution of Lambda-Theta in the CS frame for Y(1S) production in the |y| range 0.0-0.6.

Distribution of Lambda-Theta in the CS frame for Y(1S) production in the |y| range 0.6-1.2.

Distribution of Lambda-Phi in the CS frame for Y(1S) production in the |y| range 0.0-0.6.

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Measurement of Lambda polarization from Z decays

The ALEPH collaboration Buskulic, D. ; De Bonis, I. ; Decamp, D. ; et al.
Phys.Lett.B 374 (1996) 319-330, 1996.
Inspire Record 415745 DOI 10.17182/hepdata.47830

The polarization of Λ baryons from Z decays is studied with the Aleph apparatus. Evidence of longitudinal polarization of s quarks from Z decay is observed for the first time. The measured longitudinal Λ polarization is P L Λ = −0.32 ± 0.07 for z = p p beam > 0.3 . This agrees with the prediction of −0.39 ± 0.08 from the standard model and the constituent quark model, where the error is due to uncertainties in the mechanism for Λ production. The observed Λ polarization is diluted with respect to the primary s quark polarization by Λ baryons without a primary s quark. Measurements of the Λ forward-backward asymmetry and of the correlation between back-to-back Λ Λ pairs are used to check this dilution. In addition the transverse Λ polarization is measured. An indication of transverse polarization, more than two standard deviations away from zero, is found along the normal to the plane defined by the thrust axis and the Λ direction.

3 data tables

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Measurement of Lambda(b) polarization in Z decays

The ALEPH collaboration Buskulic, D. ; Casper, D. ; De Bonis, I. ; et al.
Phys.Lett.B 365 (1996) 437-447, 1996.
Inspire Record 402895 DOI 10.17182/hepdata.48060

The Λ b polarization in hadronic Z decays is measured in semileptonic decays from the average energies of the charged lepton and the neutrino. In a data sample of approximately 3 million hadronic Z decays collected by the ALEPH detector at LEP between 1991 and 1994, 462 ± 31 Λ b candidates are selected using ( Λπ + )-lepton correlations. From this event sample, the Λ b polarization is measured to be P Λ b = −0.23 −0.20 +0.24 (stat.) −0.07 +0.08 (syst.).

1 data table

No description provided.


Measurement of the polarization of tau leptons produced in Z decays

The ALEPH collaboration Decamp, D. ; Deschizeaux, B. ; Goy, C. ; et al.
Phys.Lett.B 265 (1991) 430-444, 1991.
Inspire Record 316781 DOI 10.17182/hepdata.29377

The polarization of τ leptons produced in the reaction e + e − → τ + τ − at the Z resonance has been measured using the τ decay modes e ν e ν τ , μν μ ν τ , πν τ , ϱν τ , and a 1 ν τ . The mean value obtained is P τ = −0.152±0.045, indicating that parity is violated in the neutral current process e + e − → τ + τ − . The result corresponds to a ratio of a neutral current vector and axial vector coupling constants of the τ lepton g V τ (M 2 Z ) g A τ (M 2 Z ) = 0.076±0.023 and a value of the electroweak mixing parameter sin 2 θ w ( M 2 Z ) = 0.2302 ± 0.0058.

2 data tables

Results are for both TAU+ and TAU- decay. Final combined result contains statistical and systematic errors added in quadrature.

No description provided.