Measurement of angular distributions and R = sigma(L)/sigma(T) in diffractive electroproduction of p(0) mesons

HERMES Collaboration

doi:10.1007/s100520000536

Measurement of angular distributions and R = sigma(L)/sigma(T) in diffractive electroproduction of p(0) mesons

HERMES Collaboration

Research output: Contribution to journal › Article › Academic › peer-review

Abstract

Production and decay angular distributions were extracted from measurements of exclusive electroproduction of the rho (0)(770) meson over a range in the virtual photon negative four-momentum squared 0.5 < Q(2) < 4 GeV2 and the photon-nucleon invariant mass range 3.8 < W < 6.5 GeV. The experiment was performed with the HERMES spectrometer, using a longitudinally polarized positron beam and a He-3 gas target internal to the HERA e(+/-) storage ring. The event sample combines rho (0) masons produced incoherently off individual nucleons and coherently off the nucleus as a whole. The distributions in one production angle and two angles describing the rho (0) --> pi (+)pi (-) decay yielded measurements of eight elements of the spin-density matrix, including one that had not been measured before. The results are consistent with the dominance of helicity conserving amplitudes and natural parity exchange. The improved precision achieved at 4 < W < 7 GeV, in combination with other data at W > 7 GeV, reveals evidence for an energy dependence in the ratio R of the longitudinal to transverse cross sections at constant Q(2).

Original language	English
Pages (from-to)	303-316
Number of pages	14
Journal	European Physical Journal C
Volume	18
Issue number	2
DOIs	https://doi.org/10.1007/s100520000536
Publication status	Published - 1 Dec 2000
Externally published	Yes

Keywords

MUON-PROTON-SCATTERING
VECTOR-MESONS
EXCLUSIVE ELECTROPRODUCTION
PHI ELECTROPRODUCTION
HIGH-ENERGIES
QCD
LEPTOPRODUCTION
PHOTONS
NUCLEON
RHO(0)

Access to Document

10.1007/s100520000536

Cite this

@article{f83a7b5f757e4915a8113cec94891977,

title = "Measurement of angular distributions and R = sigma(L)/sigma(T) in diffractive electroproduction of p(0) mesons",

abstract = "Production and decay angular distributions were extracted from measurements of exclusive electroproduction of the rho (0)(770) meson over a range in the virtual photon negative four-momentum squared 0.5 < Q(2) < 4 GeV2 and the photon-nucleon invariant mass range 3.8 < W < 6.5 GeV. The experiment was performed with the HERMES spectrometer, using a longitudinally polarized positron beam and a He-3 gas target internal to the HERA e(+/-) storage ring. The event sample combines rho (0) masons produced incoherently off individual nucleons and coherently off the nucleus as a whole. The distributions in one production angle and two angles describing the rho (0) --> pi (+)pi (-) decay yielded measurements of eight elements of the spin-density matrix, including one that had not been measured before. The results are consistent with the dominance of helicity conserving amplitudes and natural parity exchange. The improved precision achieved at 4 < W < 7 GeV, in combination with other data at W > 7 GeV, reveals evidence for an energy dependence in the ratio R of the longitudinal to transverse cross sections at constant Q(2).",

keywords = "MUON-PROTON-SCATTERING, VECTOR-MESONS, EXCLUSIVE ELECTROPRODUCTION, PHI ELECTROPRODUCTION, HIGH-ENERGIES, QCD, LEPTOPRODUCTION, PHOTONS, NUCLEON, RHO(0)",

author = "K. Ackerstaff and A. Airapetian and N. Akopov and M. Amarian and E.C. Aschenauer and H. Avakian and R. Avakian and A. Avetissian and B. Bains and M. Beckmann and S. Belostotski and J.E. Belz and T. Benisch and S. Bernreuther and N. Bianchi and S. Blanchard and J. Blouw and H. Bottcher and A. Borissov and J. Brack and B. Bray and W. Bruckner and A. Brull and E.E.W. Bruins and H.J. Bulten and G.P. Capitani and P. Carter and E. Cisbani and G.R. Court and P.P.J. Delheij and {De Sanctis}, E. and {De Schepper}, D. and E. Devitsin and P.K.A.D. Huberts and M. Duren and A. Dvoredsky and G. Elbakian and J. Emerson and A. Fantoni and A. Fechtchenko and M. Ferstl and K. Fiedler and B.W. Filippone and H. Fischer and B. Fox and J. Franz and S. Frullani and M.A. Funk and Y. Garber and {van den Brand}, J.F.J. and {HERMES Collaboration}",

year = "2000",

month = dec,

day = "1",

doi = "10.1007/s100520000536",

language = "English",

volume = "18",

pages = "303--316",

journal = "European Physical Journal C",

issn = "1434-6044",

publisher = "Springer Verlag",

number = "2",

}

TY - JOUR

T1 - Measurement of angular distributions and R = sigma(L)/sigma(T) in diffractive electroproduction of p(0) mesons

AU - Ackerstaff, K.

AU - Airapetian, A.

AU - Akopov, N.

AU - Amarian, M.

AU - Aschenauer, E.C.

AU - Avakian, H.

AU - Avakian, R.

AU - Avetissian, A.

AU - Bains, B.

AU - Beckmann, M.

AU - Belostotski, S.

AU - Belz, J.E.

AU - Benisch, T.

AU - Bernreuther, S.

AU - Bianchi, N.

AU - Blanchard, S.

AU - Blouw, J.

AU - Bottcher, H.

AU - Borissov, A.

AU - Brack, J.

AU - Bray, B.

AU - Bruckner, W.

AU - Brull, A.

AU - Bruins, E.E.W.

AU - Bulten, H.J.

AU - Capitani, G.P.

AU - Carter, P.

AU - Cisbani, E.

AU - Court, G.R.

AU - Delheij, P.P.J.

AU - De Sanctis, E.

AU - De Schepper, D.

AU - Devitsin, E.

AU - Huberts, P.K.A.D.

AU - Duren, M.

AU - Dvoredsky, A.

AU - Elbakian, G.

AU - Emerson, J.

AU - Fantoni, A.

AU - Fechtchenko, A.

AU - Ferstl, M.

AU - Fiedler, K.

AU - Filippone, B.W.

AU - Fischer, H.

AU - Fox, B.

AU - Franz, J.

AU - Frullani, S.

AU - Funk, M.A.

AU - Garber, Y.

AU - van den Brand, J.F.J.

AU - HERMES Collaboration

PY - 2000/12/1

Y1 - 2000/12/1

N2 - Production and decay angular distributions were extracted from measurements of exclusive electroproduction of the rho (0)(770) meson over a range in the virtual photon negative four-momentum squared 0.5 < Q(2) < 4 GeV2 and the photon-nucleon invariant mass range 3.8 < W < 6.5 GeV. The experiment was performed with the HERMES spectrometer, using a longitudinally polarized positron beam and a He-3 gas target internal to the HERA e(+/-) storage ring. The event sample combines rho (0) masons produced incoherently off individual nucleons and coherently off the nucleus as a whole. The distributions in one production angle and two angles describing the rho (0) --> pi (+)pi (-) decay yielded measurements of eight elements of the spin-density matrix, including one that had not been measured before. The results are consistent with the dominance of helicity conserving amplitudes and natural parity exchange. The improved precision achieved at 4 < W < 7 GeV, in combination with other data at W > 7 GeV, reveals evidence for an energy dependence in the ratio R of the longitudinal to transverse cross sections at constant Q(2).

AB - Production and decay angular distributions were extracted from measurements of exclusive electroproduction of the rho (0)(770) meson over a range in the virtual photon negative four-momentum squared 0.5 < Q(2) < 4 GeV2 and the photon-nucleon invariant mass range 3.8 < W < 6.5 GeV. The experiment was performed with the HERMES spectrometer, using a longitudinally polarized positron beam and a He-3 gas target internal to the HERA e(+/-) storage ring. The event sample combines rho (0) masons produced incoherently off individual nucleons and coherently off the nucleus as a whole. The distributions in one production angle and two angles describing the rho (0) --> pi (+)pi (-) decay yielded measurements of eight elements of the spin-density matrix, including one that had not been measured before. The results are consistent with the dominance of helicity conserving amplitudes and natural parity exchange. The improved precision achieved at 4 < W < 7 GeV, in combination with other data at W > 7 GeV, reveals evidence for an energy dependence in the ratio R of the longitudinal to transverse cross sections at constant Q(2).

KW - MUON-PROTON-SCATTERING

KW - VECTOR-MESONS

KW - EXCLUSIVE ELECTROPRODUCTION

KW - PHI ELECTROPRODUCTION

KW - HIGH-ENERGIES

KW - QCD

KW - LEPTOPRODUCTION

KW - PHOTONS

KW - NUCLEON

KW - RHO(0)

U2 - 10.1007/s100520000536

DO - 10.1007/s100520000536

M3 - Article

SN - 1434-6044

VL - 18

SP - 303

EP - 316

JO - European Physical Journal C

JF - European Physical Journal C

IS - 2

ER -