HEPData Search

Showing 10 of 35 results

Exclusive rho^0 production in deep inelastic scattering at HERA

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Magill, S. ; et al.

PMC Phys.A 1 (2007) 6, 2007.

Inspire Record 757991 DOI 10.17182/hepdata.54963

Exclusive rho^0 electroproduction at HERA has been studied with the ZEUS detector using 120 pb^{-1} of integrated luminosity collected during 1996-2000. The analysis was carried out in the kinematic range of photon virtuality 2 < Q^2 < 160 GeV$^2, and gamma^* p centre-of-mass energy 32 < W < 180 GeV. The results include the Q^2 and W dependence of the gamma^* p --> rho^0 p cross section and the distribution of the squared-four-momentum transfer to the proton. The helicity analysis of the decay-matrix elements of the rho^0 was used to study the ratio of the gamma^* p cross section for longitudinal and transverse photon as a function of Q^2 and W. Finally, an effective Pomeron trajectory was extracted. The results are compared to various theoretical predictions.

30 data tables

Table 1

Measurement of the spin density matrix element r_04_00 as a function of Q**2.

Table 2

Measurement of the spin density matrix element RE(r_04_10) as a function of Q**2.

Table 3

Measurement of the spin density matrix element r_04_1-1 as a function of Q**2.

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Exclusive electroproduction of J/psi mesons at HERA.

The ZEUS collaboration Chekanov, S. ; Derrick, M. ; Krakauer, D. ; et al.

Nucl.Phys.B 695 (2004) 3-37, 2004.

Inspire Record 647777 DOI 10.17182/hepdata.46277

The exclusive electroproduction of J/psi mesons, ep->epJ/psi, has been studied with the ZEUS detector at HERA for virtualities of the exchanged photon in the ranges 0.15<Q^2<0.8 GeV^2 and 2<Q^2<100 GeV^2 using integrated luminosities of 69 pb^-1 and 83 pb^-1, respectively.The photon-proton centre-of-mass energy was in the range 30<W<220 GeV and the squared four-momentum transfer at the proton vertex |t|<1.The cross sections and decay angular distributions are presented as functions of Q^2, W and t. The effective parameters of the Pomeron trajectory are in agreement with those found in J/psi photoproduction. The spin-density matrix elements, calculated from the decay angular distributions, are consistent with the hypothesis of s-channel helicity conservation. The ratio of the longitudinal to transverse cross sections, sigma_L/sigma_T, grows with Q^2, whilst no dependence on W or t is observed. The results are in agreement with perturbative QCD calculations and exhibit a strong sensitivity to the gluon distribution in the proton.

20 data tables

Table 1

Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 0.15 to 0.18 GeV**2.

Table 2

Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 2 to 5 GeV**2.

Table 3

Cross sections for exclusive J/PSI production as a function of W in the Q**2 region 5 to 10 GeV**2.

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Production asymmetry measurement of high x(T) hadrons in p(pol.) p collisions at 40-GeV.

Abramov, V.V. ; Dyshkant, A.S. ; Evdokimov, V.N. ; et al.

Nucl.Phys.B 492 (1997) 3-17, 1997.

Inspire Record 429347 DOI 10.17182/hepdata.40519

Single-spin asymmetries for hadrons have been measured in collisions of transversely-polarized 40 GeV/c proton beam with an unpolarized liquid hydrogen target. The asymmetries were measured for pi+-, K+-, protons and antiprotons, produced in the central region (0.02 < Xf < 0.10 and 0.7 < Pt < 3.4 GeV/c). Asymmetries for pi+-, K+- and antiprotons show within measurement errors the linear dependence on Xt and change a sign near 0.37. For protons negative asymmetry, independent of Xt has been found. The results are compared with those of other experiments and SU(6) model predictions.

3 data tables

Table 1

Table 2

Table 3

Neutral strange particle production in sulphur sulphur and proton sulphur collisions at 200-GeV/nucleon

The NA35 collaboration Bartke, J. ; Bialkowska, H. ; Bock, R. ; et al.

Z.Phys.C 48 (1990) 191-200, 1990.

Inspire Record 304994 DOI 10.17182/hepdata.15177

The production of Λ,$\bar \Lambda$ andKs0 has been studied in 200 GeV/nucleonp+S and S+S collisions in the streamer chamber of the NA35 experiment at the CERN SPS. Significant enhancement of the multiplicities of all observed strange particles relative to negative hadrons was observed in central S+S collisions, as compared top+p andp+S collisions. The latter collisions show no overall (relative) strangeness enhancement overp+p, but the rapidity distributions and hadron multiplicities indicate some secondary cascading production of Λ particles in thep+S andp+Au collisions. The Λ polarization in central S+S collisions was found to be compatible with zero up topT=2 GeV/c.

15 data tables

Table 1

Tranverse kinetic energy spectra of neutral strange particles in P SU collisions.

Table 2

Tranverse kinetic energy spectra of neutral strange particles in P SU collisions.

Table 3

Tranverse kinetic energy spectra of neutral strange particles in SU SU collisions.

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Polarization of cumulative protons in the reaction gamma A --> p X.

Avakyan, R.O. ; Avakian, E.O. ; Avdalyan, G.A. ; et al.

Sov.J.Nucl.Phys. 51 (1990) 999-1000, 1990.

Inspire Record 306076 DOI 10.17182/hepdata.17310

None

3 data tables

Table 1

No description provided.

Table 2

No description provided.

Table 3

No description provided.

New Measurement of the Production Polarization and Magnetic Moment of the Cascade Minus Hyperon

Trost, L.H. ; McCliment, E.R. ; Newsom, C.R. ; et al.

Phys.Rev.D 40 (1989) 1703, 1989.

Inspire Record 280604 DOI 10.17182/hepdata.23053

We have measured the production polarization and magnetic moment of a sample of 89×103Ξ− hyperons produced in the inclusive reaction p(400 GeV/c)+Cu→Ξ−+X. The weighted average of the polarization is -0.070±0.008±0.010 at a pt of 0.63 GeV/c. The Ξ−'s magnetic moment yields the value μΞ=−0.661±0.036±0.036 nuclear magnetons. The first error is statistical, the second systematic.

1 data table

Table 1

No description provided.