Transverse-target-spin asymmetry in exclusive $\omega$-meson electroproduction

The HERMES collaboration Airapetian, A. ; Akopov, N. ; Akopov, Z. ; et al.
Eur.Phys.J.C 75 (2015) 600, 2015.
Inspire Record 1391139 DOI 10.17182/hepdata.75465

Hard exclusive electroproduction of $\omega$ mesons is studied with the HERMES spectrometer at the DESY laboratory by scattering 27.6 GeV positron and electron beams off a transversely polarized hydrogen target. The amplitudes of five azimuthal modulations of the single-spin asymmetry of the cross section with respect to the transverse proton polarization are measured. They are determined in the entire kinematic region as well as for two bins in photon virtuality and momentum transfer to the nucleon. Also, a separation of asymmetry amplitudes into longitudinal and transverse components is done. These results are compared to a phenomenological model that includes the pion pole contribution. Within this model, the data favor a positive $\pi\omega$ transition form factor.

4 data tables

The amplitudes of the five sine and two cosine modulations as determined in the entire kinematic region. The results receive an additional 8.2% scale uncertainty corresponding to the target-polarization uncertainty.

The definition of intervals and the mean values of the kinematic variables.

Results on the kinematic dependences of the five asymmetry amplitudes $A_{UT}$ and two amplitudes $A_{UU}$. The first two columns correspond to the $-t'$ intervals $0.00 - 0.07 - 0.20$ GeV$^2$ and the last two columns to the $Q^{2}$ intervals $1.00 - 1.85 - 10.00$ GeV$^2$. The results receive an additional 8.2% scale uncertainty corresponding to the target-polarization uncertainty.

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Investigation of the Angular Dependence of the Cross Section for Photoproduction of Pions on Nucleons

Adamovich, M.I. ; Larionova, V.G. ; Latypova, R.A. ; et al.
Sov.Phys.JETP 26 344-349, 2015.
Inspire Record 1387574 DOI 10.17182/hepdata.17060

The differential cross sections for they+ p-- n + 7T+ process were measured for y-quantum energies 200, 205 and 210 MeV and meson emission angles 16, 24, 36, 44, 56, 64, 76, 84, 96, 104, 116, 124, 136, 144 and 156° relative to the photon beam in the laboratory system. A phenomenological analysis of the results is carried out and some multipole charged-meson photoproduction amplitudes are determined. The results are compared with the predictions of the dispersion-relation theory.

1 data table

Axis error includes +- 4.8/4.8 contribution.


Spin density matrix elements in exclusive $\omega$ electroproduction on $^1$H and $^2$H targets at 27.5 GeV beam energy

The HERMES collaboration Airapetian, A. ; Akopov, N. ; Akopov, Z. ; et al.
Eur.Phys.J.C 74 (2014) 3110, 2014.
Inspire Record 1305286 DOI 10.17182/hepdata.70751

Exclusive electroproduction of $\omega$ mesons on unpolarized hydrogen and deuterium targets is studied in the kinematic region of Q$^2$>1.0 GeV$^2$, 3.0 GeV < W < 6.3 GeV, and -t'< 0.2 GeV$^2$. Results on the angular distribution of the $\omega$ meson, including its decay products, are presented. The data were accumulated with the HERMES forward spectrometer during the 1996-2007 running period using the 27.6 GeV longitudinally polarized electron or positron beam of HERA. The determination of the virtual-photon longitudinal-to-transverse cross-section ratio reveals that a considerable part of the cross section arises from transversely polarized photons. Spin density matrix elements are presented in projections of Q$^2$ or -t'. Violation of s-channel helicity conservation is observed for some of these elements. A sizable contribution from unnatural-parity-exchange amplitudes is found and the phase shift between those amplitudes that describe transverse $\omega$ production by longitudinal and transverse virtual photons, $\gamma^{*}_{L} \to \omega_{T}$ and $\gamma^{*}_{T} \to \omega_{T}$, is determined for the first time. A hierarchy of helicity amplitudes is established, which mainly means that the unnatural-parity-exchange amplitude describing the $\gamma^*_T \to \omega_T$ transition dominates over the two natural-parity-exchange amplitudes describing the $\gamma^*_L \to \omega_L$ and $\gamma^*_T \to \omega_T$ transitions, with the latter two being of similar magnitude. Good agreement is found between the HERMES proton data and results of a pQCD-inspired phenomenological model that includes pion-pole contributions, which are of unnatural parity.

9 data tables

The 23 unpolarized and polarized $\omega$ SDMEs from the proton and deuteron data.

The 23 unpolarized and polarized $\omega$ SDMEs for the proton data in $Q^2$ intervals: $1.00 - 1.57 - 2.55 - 10.00$ GeV$^2$.

The 23 unpolarized and polarized $\omega$ SDMEs for the proton data in $-t'$ intervals: $0.000 - 0.044 - 0.105 - 0.200$ GeV$^2$.

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FRAGMENTATION OF QUARKS AND DIQUARKS IN pi- p INTERACTIONS AT P = 40-GeV/c

Grishin, V.G. ; Didenko, L.A. ; Metreveli, Z.V. ;
IN *TBILISI 1984, PROCEEDINGS, QUARKS 84, VOL. 2* 281-291 AND DUBNA JINR - 83-823 (83,REC.FEB.84) 12p, 1983.
Inspire Record 196648 DOI 10.17182/hepdata.39065

None

12 data tables

No description provided.

No description provided.

No description provided.

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ANALYSIS OF HADRON JET BEHAVIOR IN pi- C INTERACTIONS AT 40-GeV/c

Grishin, V.G. ; Didenko, L.A. ; Eliseev, S.M. ; et al.
Sov.J.Nucl.Phys. 38 (1983) 410, 1983.
Inspire Record 179980 DOI 10.17182/hepdata.9639

None

2 data tables

FOR Q(P=3 4)=ALL,1,2,3,4 MASSES OF NUCLEON, 2NUCLEONS, 3NUCLENOS AN SO ON WERE USED TO CALCULATE C.M. ANGLE.

No description provided.


ANALYSIS OF pi- p INTERACTIONS AT 40-GeV/c BY MEANS OF COLLECTIVE VARIABLES AND METHODICAL PROBLEMS OF DISCRIMINATING HADRON JETS

Grishin, V.G. ; Didenko, L.A. ; Kanarek, T.I. ; et al.
Sov.J.Nucl.Phys. 37 (1983) 545, 1983.
Inspire Record 179183 DOI 10.17182/hepdata.9735

None

12 data tables

No description provided.

DATA FOR NON-DIFFRACTIVE EVENTS.

No description provided.

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ESTIMATE OF THE AVERAGE MULTIPLICITY OF RELATIVISTIC PROTONS PRODUCED IN MULTI - NUCLEON AND pi- C-12 INTERACTIONS

Grishin, V.G. ; Kanarek, T. ; Simic, L. ;
Sov.J.Nucl.Phys. 36 (1982) 248, 1982.
Inspire Record 168966 DOI 10.17182/hepdata.39146

None

12 data tables

No description provided.

No description provided.

No description provided.

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COMPARISON OF THE JET BEHAVIOR OF HADRONS IN pi- p INTERACTIONS AT 40-GeV/c WITH HADRON PRODUCTION IN e+ e- ANNIHILATION

Grishin, V.G. ; Didenko, L.A. ; Kanarek, T. ;
JINR-P1-81-542, 1981.
Inspire Record 168221 DOI 10.17182/hepdata.39140

None

8 data tables

No description provided.

NON DIFFRACTION EVENTS.

No description provided.

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SOURCES OF LEADING PIONS IN pi+ p AND pi- p INTERACTIONS AT 16-GeV/c AND 40-GeV/c

Becker, L. ; Grishin, V.G. ; Kvatadze, R.A. ;
Sov.J.Nucl.Phys. 35 (1982) 543, 1982.
Inspire Record 166978 DOI 10.17182/hepdata.39232

None

10 data tables

P=4 IS 'LEADING'.

P=5 IS 'LEADING'.

P=5 IS 'LEADING'.

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Space-time Characteristics of Radiation Region of Secondary Negative Pions, Produced in $\pi^- p$ Interactions at 40-{GeV}/$c$

Angelov, N. ; Akhababian, N. ; Grishin, V.G. ; et al.
Yad.Fiz. 35 (1982) 76, 1982.
Inspire Record 166105 DOI 10.17182/hepdata.39205

None

1 data table

No description provided.